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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form 10-K

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For the year ended December 31, 2021

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ImmunoGen, Inc.

Form 10-K

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Forward-looking statements

The Annual Report on Form 10-K includes forward-looking statements. Forward-looking statements are neither historical facts nor assurances of future performance. Instead, these forward-looking statements relate to analyses and other information that are based on beliefs, expectations, assumptions, and forecasts of future results and estimates of amounts that are not yet determinable. These statements also relate to our prospects, future developments, product candidates, and business strategies.

These forward-looking statements are identified by their use of terms and phrases, such as “anticipate,” “believe,” “could,” “estimate,” “expect,” “intend,” “may,” “plan,” “predict,” “project,” “will,” and other similar terms and phrases, including references to assumptions.

The forward-looking statements in this Annual Report on Form 10-K include, but are not limited to, statements about:

We may not actually achieve the plans, intentions, or expectations disclosed in our forward-looking statements, and investors should not place undue reliance on our forward-looking statements. Additionally, these forward-looking statements involve known and unknown risks, uncertainties, and other factors that may cause actual results to be materially different from those contemplated by our forward-looking statements. These known and unknown risks, uncertainties, and other factors are described in detail in the “Risk Factors” section and in other sections of this report.

The forward-looking statements contained herein represent our views as of the date of this Annual Report on Form 10-K. Except as required by law, we disclaim any intention or obligation to update or revise any forward-looking statements, whether as a result of new information, future events, or otherwise.

Risk Factors Summary

Our business is subject to varying degrees of risk and uncertainty. Investors should consider the risks and uncertainties summarized below, as well as the risks and uncertainties discussed further in Part I, Item 1A, “Risk Factors” of this Annual Report on Form 10-K.

Our business is subject to the following principal risks and uncertainties:

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Note Regarding Third-Party Trademarks

KADCYLA^® is a registered trademark of Genentech, Inc. KYMRIAH^® is a registered trademark of Novartis AG. Probody is a trademark of CytomX. ELZONRIS^® is a registered trademark of Menarini Group. Any other trademarks referred to in this Annual Report on Form 10-K are the property of their respective owners.

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We have established a leadership position in ADCs with a portfolio of differentiated product candidates addressing both solid tumors and hematologic malignancies.

Mirvetuximab Soravtansine

Our lead program is mirvetuximab soravtansine (mirvetuximab), a first-in-class investigational ADC targeting folate receptor alpha (FRα), a cell-surface protein over-expressed in a number of epithelial tumors, including ovarian, endometrial, and non-small-cell lung cancers. Following consultation with the U.S. Food and Drug Administration (FDA), we initiated two trials of mirvetuximab in patients with platinum-resistant ovarian cancer whose tumors express high levels of FRα (FRα-high): SORAYA, a single-arm clinical trial that could lead to accelerated approval, pending FDA review; and MIRASOL, a randomized Phase 3 clinical trial that, if successful, could lead to full approval in this setting.

SORAYA was designed to study mirvetuximab in patients with FRα-high platinum-resistant epithelial ovarian, primary peritoneal, or fallopian tube cancer and who have been treated with up to three prior regimens—at least one of which included bevacizumab. The primary endpoint for the study was confirmed objective response rate (ORR) as assessed by investigator, including complete and partial responses, and the key secondary endpoint was duration of response (DOR). ORR was also assessed by blinded independent central review (BICR). The study was designed to assess ORR as compared to a null hypothesis of a 12% ORR, based on expectations with available single agent chemotherapy from the AURELIA study in patients with platinum-resistant ovarian cancer and one to two prior lines of therapy.

SORAYA enrolled 106 patients with a median of three prior lines of therapy (range one to four; 51% had three prior lines of therapy and 48% had one to two prior lines of therapy). All patients received prior bevacizumab; 48% of patients received a prior poly ADP-ribose polymerase (PARP) inhibitor. As of the November 16, 2021 cutoff date, the median follow-up time was 8.1 months.

ORR by investigator was 32.4% (95% confidence interval (CI): 23.6%, 42.2%), including five complete responses (CRs). ORR by BICR was 31.6% (95% CI: 22.4%, 41.9%), including five CRs. Responses were observed regardless of prior PARP inhibitor or number of prior lines of therapy.

As of the November 16, 2021 cutoff date, median DOR was 5.9 months (95% CI: 5.6, 7.7). With nearly half of responders continuing on therapy, the duration of response continues to evolve, and, with longer follow-up, median DOR could increase.

Mirvetuximab was observed to be well-tolerated, consistent with safety data seen in more than 700 patients treated in the broader mirvetuximab program. Treatment-related adverse events (AEs) led to dose reductions in 19% of patients, dose delays in 32% of patients, and discontinuations in 7% of patients.

The most common treatment-related AEs included blurred vision (41% all grades; 6% grade 3+), keratopathy (35% all grades; 9% grade 3+), and nausea (29% all grades; 0% grade 3+).

We plan to submit a biologics license application (BLA) to the FDA in the first quarter of 2022 for accelerated approval of mirvetuximab in second through fourth-line patients with FRα-positive, platinum-resistant ovarian cancer. Thereafter, we plan to seek full approval pending a positive MIRASOL Phase 3 trial.

Beyond FRα-high, platinum-resistant ovarian cancer in patients who had one or more prior lines of therapy, our strategy is to move mirvetuximab into platinum-sensitive disease through supplemental approval and become the combination agent of choice in ovarian cancer. To this end, we initiated PICCOLO, a single-arm study of mirvetuximab monotherapy in later-line platinum-sensitive patients. We have also generated encouraging data in recurrent platinum-sensitive disease with the combination of mirvetuximab plus carboplatin and are supporting investigator-sponsored trials (ISTs) with this combination in a single-arm study in the neoadjuvant setting and in a randomized study comparing mirvetuximab combined with carboplatin to standard of care in patients with recurrent platinum-sensitive disease. We also intend to initiate a company-sponsored single-arm Phase 2 study (0420) of this combination followed by mirvetuximab continuation in FRα-low, medium, and high patients with platinum-sensitive disease. Results from this study and our ongoing ISTs will inform a path to the potential registration for mirvetuximab plus carboplatin and, in parallel, could support compendia listing for this combination.

In addition, we presented mature data from our Phase 1b FORWARD II trial of mirvetuximab plus Avastin^® (bevacizumab) in recurrent ovarian cancer in an oral presentation at the American Society for Clinical Oncology Annual Meeting in June 2021. The combination demonstrated a 64% ORR, 11.8 month median DOR, and 10.6 month median progression free survival. Most AEs were low grade and the most common treatment related adverse events were gastrointestinal or ocular issues. We believe these data could support compendia listing for this combination in close

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proximity to the initial monotherapy approval of mirvetuximab. Furthermore, we recently aligned with FDA on GLORIOSA, a potential randomized Phase 3 study of mirvetuximab plus bevacizumab maintenance in FRα-high recurrent platinum-sensitive disease. We expect to initiate this potential label-enabling study in the second quarter of 2022.

Pivekimab Sunirine

Pivekimab sunirine (pivekimab, formerly known as IMGN632) is an ADC comprised of a high-affinity antibody designed to target CD123 with site-specific conjugation to a DNA-alkylating payload of the novel IGN (indolinobenzodiazepine pseudodimer) class. Our IGNs are designed to alkylate DNA without cross-linking, which has provided a broad therapeutic index in preclinical models. We are advancing pivekimab in clinical trials for patients with blastic plasmacytoid dendritic cell neoplasm (BPDCN) and acute myeloid leukemia (AML).

BPDCN is a rare form of blood cancer, with an annual incidence of between 500 and 1,000 patients in the US. In October 2020, the FDA granted Breakthrough Therapy designation for pivekimab for the treatment of patients with relapsed or refractory BPDCN. Based on feedback from the FDA, we amended our ongoing 801 Phase 2 study, known as CADENZA, to include a new cohort of up to 20 frontline BPDCN patients. We expect to generate top-line data for this frontline cohort in the second half of 2022. At the 2021 American Society of Hematology (ASH) Annual Meeting in December 2021, we presented a poster highlighting three frontline patients who were enrolled in Study 801 prior to opening of the pivotal frontline cohort; all three of these patients achieved clinical complete response (CRc) as of the data cutoff date.

Our 802 study, which is a Phase 1b/2 study designed to determine the safety, tolerability, and preliminary antileukemia activity of pivekimab when administered in combination with azacytidine (AZA) and venetoclax (VEN) to patients with relapsed and frontline CD123-positive AML, is in dose-escalation, enrolling relapsed and refractory (R/R) patients to determine the recommended Phase 2 dose of pivekimab for the triplet combination regimen. At ASH 2021, we shared data in an oral presentation showing responses across all cohorts/doses and schedules (efficacy evaluable population, n=46). As of the cutoff date, the ORR was 48%, with a composite complete remission (CCR) rate of 30%. Higher intensity cohorts (n=29) were associated with higher response rates, including an ORR of 59% and a CCR rate of 38%. Significant activity was also observed in the FLT3 mutant subset (n=9), with ORR and CCR rates of 89% and 78%, respectively. The toxicity profile was manageable in this R/R AML population with multiple prior therapies. The most common treatment emergent AEs of any grade seen in >20% of patients were infusion-related reactions, febrile neutropenia, dyspnea, fatigue, hypophosphatemia, diarrhea, hypokalemia, nausea, vomiting, and pneumonia. Cytopenias and infections were consistent with those observed with the AZA+VEN regimen in this R/R population. No tumor lysis syndrome, veno-occlusive disease, capillary leak, or cytokine release were observed. The 30-day mortality was 0%.

We are in the final stages of determining the recommended Phase 2 dose for this triplet combination and expect to initiate expansion cohorts in relapsed and frontline patients this year.

Other Pipeline Programs

We continue to advance our earlier-stage pipeline programs. IMGC936 is an ADC in co-development with MacroGenics, Inc. that is designed to target ADAM9, an enzyme over-expressed in a range of solid tumors and implicated in tumor progression and metastasis. IMGC936 incorporates a number of innovations, including antibody engineering to extend half-life, site-specific conjugation with a fixed drug-antibody ratio to enable higher dosing, and a next-generation linker and payload designed for improved stability and bystander activity. We presented preclinical data on IMGC936 at the American Association for Cancer Research (AACR) Annual Meeting in April 2021, demonstrating anti-tumor activity in multiple solid tumor models. We continue to enroll patients in the Phase 1 study for this program and expect initial data in 2022.

IMGN151 is our next generation anti-FRα product candidate in preclinical development. This ADC integrates innovation in each of its components, which we believe may enable IMGN151 to address patient populations with lower levels of FRα expression, including tumor types outside of ovarian cancer. In January 2022, we submitted an IND application to evaluate IMGN151 in a planned Phase 1 clinical trial in patients with recurrent endometrial cancer and recurrent, high-grade serous epithelial ovarian, primary peritoneal, or fallopian tube cancers. In February 2022, the FDA placed a clinical hold on our IND application pending the resolution of certain chemistry, manufacturing, and controls, or CMC, information requests. We are generating data responsive to the requests and anticipate filing these responses mid-year, which we believe will enable us to proceed with the study in due course thereafter.

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Collaborations and Out-Licenses

Over the last 40 years, we believe ImmunoGen has assembled the most comprehensive ‘‘toolbox’’ in the ADC field. Our platform technology combines advanced chemistry and biochemistry with innovative approaches to antibody optimization, with a focus on increasing the diversity and potency of our payload agents, advancing antibody-payload linkage and release technologies, and integration of novel approaches to antibody engineering. These capabilities have enabled us to generate a pipeline of novel candidates with potent anti-tumor activity and favorable safety profiles that we can develop as monotherapies and in combination with existing and novel therapies.

Collaborating on ADC development with other companies allows us to generate revenue, mitigate expenses, enhance our capabilities, and extend the reach of our proprietary platform. The most advanced partner program is Roche’s marketed product, KADCYLA® (ado-trastuzumab emtansine). Our ADC technology is also used in candidates in clinical development with a number of partners. We have evolved our partnering approach to pursue relationships where we can gain access to technology and complementary capabilities, such as our technology swap with CytomX Therapeutics, Inc. (CytomX), as well as co-development and co-commercialization arrangements, such as our relationship with MacroGenics.

We have selectively licensed restricted access to our ADC platform technology to other companies to expand the use of our technology and to provide us with cash to fund our own product programs. These agreements typically provide the licensee with rights to use our ADC platform technology with its antibodies or related targeting vehicles to a defined target to develop products. The licensee is generally responsible for the development, clinical testing, manufacturing, registration, and commercialization of any resulting product candidate. As part of these agreements, we are generally entitled to receive upfront fees, potential milestone payments, royalties on the sales of any resulting products, and research and development funding based on activities performed at our collaborative partner’s request.

Below is a table setting forth our current licensed ADC partnerships and status of the most advanced program in each partnership:

¹ Undisclosed.

² Debiopharm has an exclusive license for Debio 1562 (formerly known as IMGN529).

³ Oxford BioTherapeutics and Menarini are developing MEN 1309, an ADC targeting CD205 and utilizing our DM4 payload, pursuant to a sublicense from Amgen, which in turn licensed our maytansinoid ADC technology to develop and commercialize ADCs targeting CD205.

Below is a brief description of the business relationships underlying each of the foregoing programs. For more information concerning these relationships, including their ongoing financial and accounting impact on our business, please read Note C, Significant Collaborative Agreements, to our consolidated financial statements included in this report.

Roche

In 2000, we granted Genentech, now a unit of Roche, an exclusive development and commercialization license to use our maytansinoid technology with antibodies that target HER2. Roche’s KADCYLA resulted from this license.

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KADCYLA was approved for marketing in the U.S., EU, and Japan in 2013. We are entitled to receive up to a total of $44 million in milestone payments, of which we have received $39 million to date, and also tiered royalties on the commercial sales of KADCYLA or any other resulting products as described below. Roche is responsible for the development, manufacturing, and marketing of any products resulting from this license.

In 2015, Immunity Royalty Holdings, L.P. (IRH) paid us $200 million to purchase our right to receive 100% of the royalty payments on commercial sales of KADCYLA arising under our development and commercialization license with Genentech, until IRH had received aggregate KADCYLA royalties equal to $235 million or $260 million, depending on when the aggregate KADCYLA royalties received by IRH reached a specified milestone. Once the applicable threshold was met, we would thereafter have received 85% and IRH would have received 15% of the KADCYLA royalties for the remaining royalty term. In January 2019, we sold our residual rights to receive royalty payments on commercial sales of KADCYLA to OMERS, the defined benefit pension plan for municipal employees in the Province of Ontario, Canada, for $65.2 million, net of fees. Simultaneously, OMERS purchased IRH’s right to the royalties we previously sold to IRH as described above, thereby obtaining the rights to 100% of the royalties received from that date on.

We also granted Roche, through its Genentech unit, exclusive development and commercialization licenses to use our maytansinoid ADC technology with antibodies to four specified targets, which were granted under the terms of a separate, now expired 2000 right-to-test agreement with Genentech. For each of these licenses, we are entitled to receive up to a total of $38 million in milestone payments and also royalties on the sales of any resulting products. Roche is responsible for the development, manufacturing, and marketing of any products resulting from these licenses. The standard termination provisions discussed below apply to these licenses.

Huadong

In October 2020, we entered into a collaboration and license agreement with Hangzhou Zhongmei Huadong Pharmaceutical Co., Ltd. (Huadong) a subsidiary of Huadong Medicine Co., Ltd., under which Huadong will exclusively develop and commercialize mirvetuximab in the People’s Republic of China, Hong Kong, Macau, and Taiwan, which we refer to as Greater China. Under the terms of the collaboration and license agreement, we received a non-refundable upfront payment of $40 million and are eligible to receive additional payments of up to $265.0 million as certain development, regulatory, and net sales milestones are achieved. We are also eligible to receive tiered low double digit to high teen royalties as a percentage of mirvetuximab commercial sales by Huadong in Greater China. Huadong is responsible for the development and commercialization of mirvetuximab in Greater China except in limited circumstances. In addition, we granted Huadong a right of first negotiation if we determine to enter into an agreement to grant a third party rights in Greater China to develop or commercialize a product, other than mirvetuximab, that specifically binds to FRα. We retain all rights to mirvetuximab in the rest of the world. The standard termination provisions discussed below apply to this license.

CytomX

In 2016, we granted CytomX an exclusive development and commercialization license to our maytansinoid and IGN ADC technology for use with Probodies™ that target CD166 under a now-expired reciprocal right-to-test agreement. We are entitled to receive up to a total of $160 million in milestone payments plus royalties on the commercial sales of any resulting product. CytomX is responsible for the manufacturing, product development, and marketing of any products resulting from this license. The standard termination provisions discussed below apply to this license.

In 2017, we took exclusive development and commercialization licenses to CytomX’s proprietary Probody technology for use with Probodies that target two specified targets under the same reciprocal right-to-test agreement. We terminated one of these licenses for convenience prior to the end of 2017 and terminated the second license in December 2019 in connection with the grant of the EpCAM license to CytomX discussed below.

In December 2019, we granted CytomX an exclusive development and commercialization license to our maytansinoid and IGN ADC technology for use with antibodies (and Probodies™ developed therefrom) that target EpCAM. In January 2020, we received a $7.5 million upfront license payment and are entitled to receive up to a total of $355 million in milestone payments plus royalties on the commercial sales of any resulting product. CytomX is responsible for the manufacturing, product development, and marketing of any products resulting from this license. The standard termination provisions discussed below apply to this license.

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Debiopharm

 In May 2017, Debiopharm International S.A. (Debiopharm) acquired our IMGN529 program, a clinical-stage anti-CD37 ADC for the treatment of patients with B-cell malignancies, such as non-Hodgkin lymphomas (NHL). Under the terms of the Exclusive License and Asset Purchase agreement, we received a $25.0 million upfront payment for specified assets related to IMGN529 and an exclusive license to additional intellectual property necessary or useful for Debiopharm to develop and commercialize IMGN529 (now known as Debio 1562). We also received a $5.0 million milestone payment upon transfer of certain ImmunoGen technologies related to the program and were entitled to receive a $25.0 million milestone payment upon IMGN529 entering a Phase 3 clinical trial.

In October 2021, we and Debiopharm amended the Exclusive License and Asset Purchase agreement, pursuant to which we are entitled to receive a percentage of all payments generated from future sublicenses of Debio 1562, including upfront fees, milestones, and royalties, up to an aggregate of $30.0 million and in lieu of the potential $25.0 million development milestone payment under the original agreement. The standard termination provisions discussed below apply to this agreement.

Bayer

In 2008, we granted Bayer an exclusive development and commercialization license to use our maytansinoid ADC technology with antibodies or other proteins that target mesothelin. We are entitled to receive, for each product developed and marketed by Bayer under this agreement, up to a total of $170.5 million in milestone payments plus royalties on the commercial sales of any resulting products. Bayer is responsible for the development, manufacturing, and marketing of any products resulting from this license. The standard termination provisions discussed below apply to this license.

Novartis

We granted Novartis exclusive development and commercialization licenses to our maytansinoid and IGN ADC technology for use with antibodies to six specified targets under a now-expired right-to-test agreement established in 2010. In May 2018, Novartis terminated one of its six development and commercialization licenses. With respect to each remaining license, we are entitled to receive up to a total of $199.5 million in milestone payments, plus royalties on the commercial sales of any resulting products. Novartis is responsible for the manufacturing, product development, and marketing of any products resulting from this agreement. The standard termination provisions discussed below apply to these licenses.

Oxford BioTherapeutics/Menarini

In 2013, we granted Amgen, Inc. (Amgen) an exclusive development and commercialization license to our maytansinoid ADC technology for use with antibodies that target CD205 under a now-expired right-to-test agreement, which Amgen sublicensed to Oxford BioTherapeutics, which is developing MEN 1309 with Menarini. With respect to this license, we are entitled to receive up to a total of $34 million in milestone payments, plus royalties on the commercial sales of any resulting products. Amgen (or its sublicensee(s)) is responsible for the manufacturing, product development, and marketing of any products resulting from this development and commercialization license. The standard termination provisions discussed below apply to this license.

Fusion

In December 2016, we entered into an exclusive license agreement to a specified target with Fusion Pharmaceuticals Inc. (Fusion). We are entitled to receive up to a total of $50 million in milestone payments plus royalties on the commercial sales of any resulting products. Fusion is responsible for the manufacturing, development, and marketing of any products resulting from the license. The standard termination provisions discussed below apply to this license.

Viridian

In October 2020, we entered into a license agreement with Viridian Therapeutics, Inc. (Viridian) pursuant to which we granted Viridian the exclusive right to develop and commercialize an insulin-like growth factor-1 receptor (IGF-1R) antibody for all non-oncology indications that do not use radiopharmaceuticals in exchange for an upfront payment, with the potential to receive up to a total of $143.0 million in milestone payments plus royalties on the commercial sales of any resulting product. Viridian is responsible for the manufacturing, development, and marketing of any products resulting from the license agreement. The standard termination provisions discussed below apply to this license.

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Standard Termination Provisions

Standard termination provisions in our license agreements state that the partner may terminate the agreement for convenience at any time upon prior written notice to us. The agreement may also be terminated by either party for a material breach by the other, subject to notice and cure provisions. We may also terminate certain of these agreements upon the occurrence of specified events. Upon termination, the partner’s rights to our intellectual property with respect to the applicable target are canceled and could then be used by us or re-licensed for that target. Unless earlier terminated, each agreement will continue in effect until the expiration of partner’s royalty obligations, which are determined on a product-by-product and country-by-country basis. For each product and country, royalty obligations commence upon first commercial sale of that product in that country and extend until the later of either the expiration of the last-to-expire ImmunoGen patent covering that product in that country or the expiration for that country of the minimum royalty period specified in the agreement.

Other Agreements

From time to time, we have entered into additional agreements with some of our collaborators pursuant to which we have provided certain Chemistry, Manufacturing and Controls (CMC)-related development and pre-pivotal ADC manufacturing services, or supplied ADC payloads, with respect to products they are developing under their licenses with us, with respect to which we have been entitled to receive payments at mutually negotiated rates.

Patents, Trademarks and Trade Secrets

ImmunoGen has a substantial and robust intellectual property portfolio comprising nearly 1,500 issued patents and over 600 pending patent applications on a worldwide basis. Our intellectual property strategy centers on obtaining high quality patent protection directed to various embodiments of our proprietary technologies and product candidates. Using this strategy, our ADC technology and our product candidates are protected through a multi-layered approach. In this regard, we have patents and patent applications covering antibodies and other cell binding agents, linkers, cytotoxic payload agents (e.g., tubulin-acting maytansinoids, DNA-alkylating IGNs, and DNA-acting camptothecins), conjugation methodologies and complete ADCs, comprising one or more of these components, as well as methods of making and using each of the above. Typically, multiple issued patents and pending patent applications cover various embodiments of each of ImmunoGen’s and our licensees’ product candidates.

We consider our tubulin-acting maytansinoid, DNA-alkylating IGN, and DNA-acting camptothecin cytotoxic payload agent technologies to be key components of our overall patent strategy. With regard to our tubulin-acting maytansinoid cytotoxic payload agents, we currently own 22 issued U.S. patents covering various embodiments of our maytansinoid technology including those with claims directed to certain maytansinoids, including DM4 and DM21, and methods of manufacturing of DM1, DM4, and DM21, as well as methods of using the same. These issued patents remain in force until various times between 2022 and 2038. With regard to our IGN payload agents, we have 35 issued U.S. patents covering various aspects of our DNA-acting cytotoxic payload agents, which will expire at various times between 2030 and 2042. With regard to our camptothecin agents, we have an issued U.S. patent covering various aspects of our camptothecin cytotoxic payload agents, which expires in 2040. In all cases, we have received or are applying for comparable patent protection in other major commercial and manufacturing jurisdictions, including Europe, Japan, and China. In nearly all cases for our maytansinoid, IGN, and camptothecin patent portfolios, we have additional pending patent applications disclosing and claiming many other related and strategically important embodiments of these technologies which, upon issuance or grant, will extend our patent protection term over these technologies by several additional years.

Our intellectual property strategy also includes pursuing patents directed to linkers, antibodies, conjugation methods, ADC formulations and the use of specific antibodies and ADCs to treat certain diseases. In this regard, we have 22 issued patents related to many of our linker technologies, as well as additional pending patent applications disclosing and claiming many other related and strategically important embodiments of these linker technologies, including methods of making the linkers and antibody maytansinoid conjugates comprising these linkers. These issued patents remain in force until various times between 2023 and 2034. We also have 20 issued U.S. patents covering methods of assembling ADCs from their constituent antibody, linker, and cytotoxic payload agent moieties. These issued patents will expire between 2026 and 2040. In nearly all instances for both our linker and conjugation patent portfolios, we have additional pending patent applications disclosing and claiming many other related and strategically important embodiments of these technologies which, upon issuance or grant, would extend our patent protection term over these technologies by several additional years. In all cases, we have received or are applying for comparable patents in other major commercial and manufacturing jurisdictions including Europe, Japan, and China.

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We also file, prosecute, and maintain a substantial portfolio of patents and patent applications specifically directed to ImmunoGen’s and our licensees’ ADC candidates. In this regard, we craft a detailed patent protection strategy for each ADC as it approaches clinical evaluation. Such strategies make use of the patents and patent applications described in the preceding paragraphs, as well as ADC-specific filings, to create a multi-layered and multi-jurisdictional patent protection approach for each ADC as it enters the clinic. In addition to the platform patent strategy described above and specific to mirvetuximab, we have 21 issued U.S. patents and 13 pending U.S. applications covering various embodiments of the composition of matter and methods of treatment using mirvetuximab, expiring at various times between 2031 and 2042. These ADC-specific patent strategies are intended to provide the exclusivity basis for revenue and royalties arising from commercial development of each of ImmunoGen’s and our licensees’ ADCs.

We expect our continued independent and collaborative work in each of these areas will lead to other patent applications. We will be the owner of all patents covering our independently generated inventions. In all other instances, we expect to either be the sole owner or co-owner of any patents covering collaboratively generated inventions insofar as they relate to co-developed products or our ADC platform technology, or otherwise have an exclusive or non-exclusive license to the technology covered by such patents.

We cannot provide assurance that pending patent applications will issue as patents or that any patents, if issued, will provide us with adequate protection against competitors with respect to the covered products, technologies, or processes. Defining the scope and term of patent protection involves complex legal and factual analyses and, at any given time, the result of such analyses may be uncertain. In addition, other parties may challenge our patents in litigation or administrative proceedings resulting in a partial or complete loss of certain patent rights owned or controlled by ImmunoGen. Furthermore, as a patent does not confer any specific freedom to operate, other parties may have patents that may block or otherwise hinder the development and commercialization of our technology.

In addition, many of the processes and much of the know-how that are important to us depend upon the skills, knowledge, and experience of our key scientific and technical personnel, which skills, knowledge, and experience are not patentable. To protect our rights in these areas, we require that all employees, consultants, advisors, and collaborators enter into confidentiality agreements with us. Further, we require that all employees enter into assignment of invention agreements as a condition of employment. We cannot provide assurance, however, that these agreements will provide adequate or any meaningful protection for our trade secrets, know-how, or other proprietary information in the event of any unauthorized use or disclosure of such trade secrets, know-how, or proprietary information. Further, in the absence of patent protection, we may be exposed to competitors who independently develop substantially equivalent technology or otherwise gain access to our trade secrets, know-how, or other proprietary information.

Competition

We focus on highly competitive areas of product development. Our competitors include major pharmaceutical companies and other biotechnology firms. For example, Pfizer, Seattle Genetics, Roche, Astellas, AstraZeneca, Daiichi Sankyo, GlaxoSmithKline, AbbVie, and the Menarini Group have programs to attach a cell-killing small molecule to an antibody for targeted delivery to cancer cells. Pharmaceutical and biotechnology companies, as well as other institutions, also compete with us for promising targets for antibody-based therapeutics, for obtaining licenses and collaboration agreements with other companies to develop targets for antibody-based therapeutics, and in recruiting highly qualified scientific personnel. Additionally, there are non-ADC therapies available and/or in development for the cancer types we and our partners are targeting. Many competitors and potential competitors have substantially greater scientific, research and product development capabilities, as well as greater financial, sales, marketing, and human resources than we do. In addition, many specialized biotechnology firms have formed collaborations with large, established companies to support the research, development, and commercialization of products that may be competitive with ours.

In particular, competitive factors within the antibody and cancer therapeutic market include:

Our competitive position depends on a combination of factors. These include effectively pursuing the development of proprietary products, the implementation of clinical development programs, the ability to appropriately manufacture, sell, and market our products, and obtain patent protection for our products. In addition, we must secure sufficient capital resources to accomplish all of the previously mentioned activities.

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Continued development of conventional and targeted chemotherapeutics by large pharmaceutical companies and biotechnology companies may result in new compounds that may compete with our product candidates. Antibodies developed by certain of these companies have been approved for use as cancer therapeutics. In the future, new antibodies or other targeted therapies may compete with our product candidates. Other companies have created or have programs to create potent cell-killing agents for attachment to antibodies. These companies may compete with us for technology out-license arrangements.

Managing the Impact of the COVID-19 Pandemic

Since the first quarter of 2020, we have continued to move our clinical studies forward while adapting to meet the evolving challenges of the COVID-19 pandemic. We implemented business continuity plans in March 2020 that enabled our workforce to remain productive while working from home until mid-September 2021, at which time our workforce returned to the office. From a manufacturing and supply chain perspective, we believe we have sufficient inventory on hand for all of our ongoing and near-term studies and to support the launch of mirvetuximab, if approved. From a regulatory perspective, since the beginning of the pandemic, we have received timely reviews of our submissions to the U.S. Food and Drug Administration (FDA) and other health authorities covering our clinical trial applications.

The impact of COVID-19 slowed site activation and patient enrollment for both SORAYA and MIRASOL, which resulted in a limited delay in patient accrual for each of these studies.

Regulatory Matters

Government Regulation and Product Approval

Government authorities in the U.S., at the federal, state, and local level, and other countries extensively regulate, among other things, the research, development, testing, manufacture, quality control, approval, labeling, packaging, storage, record-keeping, promotion, advertising, distribution, marketing, and export and import of products such as those we are developing. A new drug must be approved by the FDA through the new drug application, or NDA, process and a new biologic must be approved by the FDA through the biologics license application, or BLA, process before it may be legally marketed in the U.S.

U.S. Drug Development Process

In the U.S., the FDA regulates drugs under the federal Food, Drug, and Cosmetic Act (FDCA) and in the case of biologics, also under the Public Health Service Act (PHSA) and implementing regulations. The process of obtaining regulatory approvals and the subsequent compliance with applicable federal, state, and local statutes and regulations require the expenditure of substantial time and financial resources. Failure to comply with the applicable U.S. requirements at any time during the product development process, approval process, or after approval, may subject an applicant to adverse administrative or judicial actions. These actions could include the FDA’s refusal to approve pending applications, withdrawal of an approval, a clinical hold, warning letters, product recalls, product seizures, total or partial suspension of production or distribution, injunctions, fines, refusals of government contracts, restitution, disgorgement, or civil or criminal penalties. Any such administrative or judicial action could have a material adverse effect on our business.

The process required by the FDA before a drug or biologic may be marketed in the U.S. generally involves the following:

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Once a pharmaceutical candidate is identified for development, it enters the preclinical testing stage. Preclinical tests include laboratory evaluations of product chemistry, toxicity, and formulation, as well as animal studies. An IND sponsor must submit the results of the preclinical tests, together with manufacturing information and analytical data, to the FDA as part of the IND. The sponsor will also include a clinical protocol detailing, among other things, the objectives of the first phase of the clinical trial, the parameters to be used in monitoring safety, and the effectiveness criteria to be evaluated, if the first phase lends itself to an efficacy evaluation. Some nonclinical testing may continue even after the IND is submitted and clinical trials have begun. The IND automatically becomes effective 30 days after receipt by the FDA, unless the FDA, within the 30-day time period, places the clinical trial on a clinical hold. In such a case, the IND sponsor and the FDA must resolve any outstanding concerns before the clinical trial can begin. Clinical holds also may be imposed by the FDA at any time before or during clinical trials due to safety concerns about ongoing or proposed clinical trials or non-compliance with specific FDA requirements, and the trials may not begin or continue until the sponsor submits additional information that alleviates FDA concerns, and the FDA notifies the sponsor that the hold has been lifted.

Each clinical trial must be conducted under the supervision of one or more qualified investigators in accordance with cGCP requirements in accordance with a protocol for each phase of the clinical trial included as part of the IND, and timely safety reports must be submitted to the FDA and the investigators for serious and unexpected adverse events. A local or central institutional review board (IRB) acting on behalf of each institution participating in the clinical trial must review and approve each protocol before a clinical trial commences at that institution and must also approve the information regarding the trial and the consent form that must be provided to each trial subject or his or her legal representative, monitor the study until completed, and otherwise comply with IRB regulations.

Human clinical trials are typically conducted in three sequential phases that may overlap or be combined:

Post-approval trials, sometimes referred to as Phase 4, may be conducted after initial marketing approval. These trials are used to gain additional information about the use of the approved drug in the treatment of patients in the intended therapeutic indication. In certain instances, the FDA may mandate the performance of Phase 4 clinical trials as a condition of approval of an NDA or BLA.

The FDA or the sponsor may suspend a clinical trial at any time on various grounds, including a finding that the research subjects or patients are being exposed to an unacceptable health risk. Similarly, an IRB can suspend or terminate approval of a clinical trial at its institution if the clinical trial is not being conducted in accordance with the IRB’s requirements or if the drug has been associated with unexpected or serious patient reactions. Additionally, some clinical trials are overseen by an independent group of qualified experts organized by the sponsor, known as a data safety monitoring board or committee. Depending on its charter, this group may determine whether a trial may move forward at designated check points based on access to certain data from the trial. Phase 1, Phase 2, and Phase 3 testing may not be completed successfully within any specified period, if at all.

During the development of a new drug, sponsors may request meetings with the FDA to share information about the data gathered to date, for the FDA to provide advice, and for the sponsor and the FDA to reach agreement on the next phase of development.

Concurrent with clinical trials, companies usually complete additional animal studies and must also develop additional information about the chemistry and physical characteristics of the drug and finalize a process for manufacturing the product in commercial quantities in accordance with cGMP requirements. The manufacturing process must be capable of consistently producing quality batches of the product candidate and, among other things, the

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manufacturer must develop methods for testing the identity, strength, quality, and purity of the final drug. Additionally, appropriate packaging must be selected and tested, and stability studies must be conducted to demonstrate that the product candidate does not undergo unacceptable deterioration over its shelf life.

While the IND is active, progress reports summarizing the results of the clinical trials and nonclinical studies performed since the last progress report must be submitted at least annually to the FDA, and written IND safety reports must be submitted to the FDA and investigators for serious and unexpected suspected adverse events, findings from other studies suggesting a significant risk to humans exposed to the same or similar drugs, findings from animal or in vitro testing suggesting a significant risk to humans, and any clinically important increased incidence of a serious suspected adverse reaction compared to that listed in the protocol or investigator brochure.

There are also requirements governing the reporting of ongoing clinical trials and completed trial results to public registries. Most sponsors of clinical trials of FDA-regulated products are required to register and disclose specified clinical trial information, which is publicly available at www.clinicaltrials.gov. Information related to the product, patient population, phase of investigation, trial sites and investigators, and other aspects of the clinical trial is then made public as part of the registration. Sponsors are also obligated to discuss the results of their clinical trials after completion. Disclosure of the results of these trials can be delayed until the new product or new indication being studied has been approved. However, there are evolving rules and increasing requirements for publication of all trial-related information, and it is possible that data and other information from trials involving drugs that never garner approval could require disclosure in the future.

Companion Diagnostics

For some of our product candidates, including mirvetuximab and potentially others, we plan to work with collaborators to develop or obtain access to in vitro companion diagnostic tests to identify appropriate patients for these targeted therapies.

If the FDA believes that a diagnostic test is essential for the safe and effective use of a corresponding therapeutic product, the FDA may require the sponsor to develop, and obtain contemporaneous clearance or approval for a companion diagnostic. Companion diagnostics can be used to identify patients likely to be more responsive to a particular therapy or at increased risk for serious side effects as a result of treatment with a particular therapeutic product. They may also be useful for monitoring the response to treatment for the purpose of adjusting treatment or doses to achieve improved safety or effectiveness.

Companion diagnostics are regulated by the FDA as medical devices. The FDA indicated that it would apply a risk-based approach to determine the regulatory pathway for companion diagnostics. This means that the regulatory pathway will depend on the level of risk to patients, based on the intended use of the companion diagnostic device and the controls necessary to provide a reasonable assurance of safety and effectiveness. The two primary types of marketing pathways for medical devices are clearance of a premarket notification under Section 510(k) of the Federal Food, Drug, and Cosmetic Act, or 510(k), and approval of a premarket approval application (PMA). We expect that any companion diagnostic developed for use with our drug candidates will utilize the PMA pathway. If the diagnostic test and the therapeutic drug are studied together to support their respective approvals, the clinical trial must meet both the IND requirements and FDA’s companion diagnostic requirements that apply to clinical trials of significant risk devices.

The FDA expects that the therapeutic sponsor will address the need for a companion diagnostic device in its therapeutic product development plan and that, in most cases, the therapeutic product and its corresponding companion diagnostic device will be developed contemporaneously.

PMAs must be supported by valid scientific evidence, which typically requires extensive data, including technical, preclinical, clinical, and manufacturing data, to demonstrate to the FDA’s satisfaction the safety and effectiveness of the device. For diagnostic tests, a PMA typically includes data regarding analytical and clinical validation studies. As part of its review of the PMA, the FDA will conduct a pre-approval inspection of the manufacturing facility or facilities to ensure compliance with the Quality System Regulation (QSR) which requires manufacturers to follow design, testing, control, documentation, and other quality assurance procedures. FDA review of an initial PMA may require several years to complete.

After approval, the use of a companion diagnostic device with a therapeutic product will be stipulated in the instructions for use in the labeling of both the diagnostic device and the corresponding therapeutic product. In addition, a diagnostic test that was approved through the PMA process or one that was cleared through the 510(k) process and placed on the market will be subject to similar regulatory requirements that apply to approved drugs.

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U.S. Review and Approval Processes

The results of product development, preclinical and other non-clinical studies, and clinical trials, along with descriptions of the manufacturing process, analytical tests conducted on the chemistry of the drug, proposed labeling, and other relevant information are submitted to the FDA as part of an NDA or BLA requesting approval to market the product. The submission of an NDA or BLA is subject to the payment of user fees; a waiver of such fees may be obtained under certain limited circumstances. The FDA reviews all NDAs and BLAs submitted to ensure that they are sufficiently complete for substantive review before it accepts them for filing. The FDA may request additional information rather than accept an NDA or BLA for filing. In this event, the NDA or BLA must be resubmitted with the additional information. The resubmitted application also is subject to review before the FDA accepts it for filing. Once the submission is accepted for filing, the FDA begins an in-depth substantive review. FDA may refer the NDA or BLA to an advisory committee for review, evaluation, and recommendation as to whether the application should be approved and under what conditions. The FDA is not bound by the recommendation of an advisory committee, but it generally follows such recommendations. The approval process is lengthy and often difficult, and the FDA may refuse to approve an NDA or BLA if the applicable regulatory criteria are not satisfied or may require additional clinical or other data and information. Even if such data and information are submitted, the FDA may ultimately decide that the NDA or BLA does not satisfy the criteria for approval. Data obtained from clinical trials are not always conclusive and the FDA may analyze and interpret data differently than we analyze and interpret the same data. The FDA reviews an NDA to determine, among other things, whether a product is safe and effective for its intended use and whether its manufacturing is cGMP-compliant to assure and preserve the product’s identity, strength, quality, and purity. The FDA reviews a BLA to determine, among other things whether the product is safe, pure, and potent and the facility in which it is manufactured, processed, packed, or held meets standards designed to assure the product’s continued safety, purity, and potency. Before approving an NDA or BLA, the FDA will inspect the facility or facilities where the product is manufactured to assure compliance with cGMPs and may also inspect clinical trial sites to assure compliance with GCPs.

NDAs or BLAs receive either standard or priority review. Priority review, which is requested at the time of BLA or NDA submission, is designed to expedite the review for drugs that provide meaningful therapeutic benefit to patients over existing treatments. Priority review for an NDA for a new molecular entity and original BLAs will be 6 months from the date that the NDA or BLA is filed, compared to 10 months under standard review. Although FDA’s goal is to take action on priority review applications within 6 months, the agency does not always meet this goal and the review process may be significantly extended by FDA requests for additional information or clarification. Priority review does not change the standards for approval, but may expedite the approval process.

After the FDA evaluates an NDA or BLA, it will issue an approval letter or a Complete Response Letter. An approval letter authorizes commercial marketing of the drug with prescribing information for specific indications. A Complete Response Letter indicates that the review cycle of the application is complete, and the application will not be approved in its present form. A Complete Response Letter usually describes the specific deficiencies in the NDA or BLA identified by the FDA and may require additional clinical data, such as an additional Phase 3 trial or other significant and time-consuming requirements related to clinical trials, nonclinical studies, or manufacturing. If a Complete Response Letter is issued, the sponsor has one year to resubmit the NDA or BLA, addressing all of the deficiencies identified in the letter, or withdraw the application. Even if such data and information are submitted, the FDA may decide that the NDA or BLA does not satisfy the criteria for approval.

If a product receives regulatory approval, the approval may be significantly limited to specific diseases and dosages or the indications for use may otherwise be limited, which could restrict the commercial value of the product. In addition, the FDA may require a sponsor to conduct Phase IV testing which involves clinical trials designed to further assess a drug’s safety and effectiveness after NDA or BLA approval and may require testing and surveillance programs to monitor the safety of approved products which have been commercialized. The FDA may also place other conditions on approval including the requirement for a risk evaluation and mitigation strategy (REMS) to assure the safe use of the drug. If the FDA concludes a REMS is needed, the sponsor of the NDA or BLA must submit a proposed REMS. The FDA will not approve the NDA or BLA without an approved REMS, if required. A REMS could include medication guides, physician communication plans, or other elements to assure safe use, such as restricted distribution methods, patient registries, and other risk minimization tools. Any of these limitations on approval or marketing could restrict the commercial promotion, distribution, prescription, or dispensing of products. Marketing approval may be withdrawn for non-compliance with regulatory requirements or if problems occur following initial marketing.

The Pediatric Research Equity Act (PREA) requires a sponsor to conduct pediatric clinical trials for most drugs and biologics, for a new active ingredient, new indication, new dosage form, new dosing regimen, or new route of administration. Under PREA, original NDAs, BLAs, and supplements thereto, must contain a pediatric assessment

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unless the sponsor has received a deferral or waiver. The required assessment must evaluate the safety and effectiveness of the product for the claimed indications in all relevant pediatric subpopulations and support dosing and administration for each pediatric subpopulation for which the product is safe and effective. The sponsor or FDA may request a deferral of pediatric clinical trials for some or all of the pediatric subpopulations. A deferral may be granted for several reasons, including a finding that the drug or biologic is ready for approval for use in adults before pediatric clinical trials are complete or that additional safety or effectiveness data need to be collected before the pediatric clinical trials begin. Orphan indications are exempt from PREA. The FDA must send a non-compliance letter to any sponsor that fails to submit the required assessment, keep a deferral current, or fails to submit a request for approval of a pediatric formulation.

Patent Term Restoration and Marketing Exclusivity

Depending upon the timing, duration, and specifics of FDA approval of our drugs, some of our U.S. patents may be eligible for limited patent term extension under the Drug Price Competition and Patent Term Restoration Act of 1984, referred to as the Hatch-Waxman Amendments. The Hatch-Waxman Amendments permit a patent restoration term of up to five years as compensation for patent term lost during product development and the FDA regulatory review process. However, patent term restoration cannot extend the remaining term of a patent beyond a total of 14 years from the product’s approval date. The patent term restoration period is generally one-half the time between the effective date of an IND, and the submission date of an NDA or BLA, plus the time between the submission date of an NDA or BLA and the approval of that application. Only one patent applicable to an approved drug is eligible for the extension, and the extension must be applied for prior to expiration of the patent. The U.S. Patent and Trademark Office, in consultation with the FDA, reviews and approves the application for any patent term extension or restoration. In the future, we intend to apply for restorations of patent term for some of our currently owned or licensed patents to add patent life beyond their current expiration date, depending on the expected length of clinical trials and other factors involved in the filing of the relevant NDA.

Pediatric exclusivity is a type of marketing exclusivity available in the U.S. Under the Best Pharmaceuticals for Children Act (BPCA) an additional six months of marketing exclusivity may be available if a sponsor conducts clinical trials in children in response to a written request from the FDA (Written Request). If the Written Request does not include clinical trials in neonates, the FDA is required to include its rationale for not requesting those clinical trials. The FDA may request studies on approved or unapproved indications in separate Written Requests. The issuance of a Written Request does not require the sponsor to undertake the described clinical trials. To date, we have not received any Written Requests.

Biologics Price Competition and Innovation Act of 2009

The Patient Protection and Affordable Care Act, which included the Biologics Price Competition and Innovation Act of 2009 (BPCIA), amended the PHSA to create an abbreviated approval pathway for two types of “generic” biologics—biosimilars and interchangeable biologic products, and provides for a twelve-year data exclusivity period for the first approved biological product, or reference product, against which a biosimilar or interchangeable application is evaluated; however if pediatric clinical trials are performed and accepted by the FDA, the twelve-year data exclusivity period will be extended for an additional six months. A biosimilar product is defined as one that is highly similar to a reference product notwithstanding minor differences in clinically inactive components and for which there are no clinically meaningful differences between the biological product and the reference product in terms of the safety, purity, and potency of the product. An interchangeable product is a biosimilar product that meets additional requirements that show, among other things, that the product will produce the same clinical result as the reference product in any given patient. In addition, for products administered to a patient more than once, the effects of switching back and forth between the interchangeable product and a reference product on safety and efficacy will have to be evaluated. An interchangeable product may be substituted for the reference product without the intervention of the health care provider who prescribed the reference product.

The biosimilar applicant must demonstrate that the product is biosimilar based on data from (1) analytical studies showing that the biosimilar product is highly similar to the reference product; (2) animal studies (including toxicity); and (3) one or more clinical trials to demonstrate safety, purity, and potency in one or more appropriate conditions of use for which the reference product is approved. In addition, the applicant must show that the biosimilar and reference products have the same mechanism of action for the conditions of use on the label, route of administration, dosage, and strength, and the production facility must meet standards designed to assure product safety, purity, and potency.

An application for a biosimilar product may not be submitted until four years after the date on which the reference product was first approved. The first approved interchangeable biologic product will be granted an exclusivity

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period of up to one year after it is first commercially marketed, but the exclusivity period may be shortened under certain circumstances.

The FDA has issued a number of final and draft guidance documents in order to implement the law and will likely continue to publish new guidance as new issues relating to biosimilars and interchangeability are identified. The guidance documents provide FDA’s current thinking on approaches to demonstrating that a proposed biological product is biosimilar to or interchangeable with, a reference product. Although the FDA intends to issue additional guidance documents in the future, the absence of final guidance documents covering all issues does not prevent a sponsor from seeking licensure of a biosimilar or interchangeable product under the BPCIA, as evidenced by the products already approved by the FDA.

Orphan Drug Designation

Under the Orphan Drug Act, the FDA may grant orphan drug designation to a drug intended to treat a rare disease or condition, which is generally a disease or condition that affects fewer than 200,000 individuals in the U.S., or more than 200,000 individuals in the U.S. and for which there is no reasonable expectation that the cost of developing and making available in the U.S. a drug for this type of disease or condition will be recovered from sales in the U.S. for that drug. Orphan drug designation must be requested before submitting an NDA or BLA. After the FDA grants orphan drug designation, the identity of the therapeutic agent and its potential orphan use will be disclosed publicly by the FDA; the posting will also indicate whether a drug is no longer designated as an orphan drug. More than one product candidate may receive an orphan drug designation for the same indication. Orphan drug designation does not convey any advantage in or shorten the duration of the regulatory review and approval process.

If a product that has orphan drug designation subsequently receives the first FDA approval for the disease for which it has such designation, the product is entitled to seven years of orphan product exclusivity. Orphan product exclusivity means that the FDA cannot approve another sponsor’s marketing application for the same product for the same indication, except in very limited circumstances. For example, the FDA may approve a subsequent application for the same product in the same indication if the product is clinically superior to the previously approved drug. Orphan drug exclusivity could block the approval of one of our products for seven years if a competitor obtains approval of the same drug as defined by the FDA and we are not able to show the clinical superiority of our drug or if our product candidate is determined to be contained within the competitor’s product for the same indication or disease. The FDA continues to periodically provide additional clarification, and in July 2018 published a final guidance entitled, “Clarification of Orphan Designation of Drugs and Biologics for Pediatric Subpopulations of Common Diseases.”

Mirvetuximab has been granted orphan drug designation by the FDA in the United States, and orphan medicinal product status by the European Medicines Agency (EMA) in the European Union for the treatment of ovarian cancer. Pivekimab has been granted orphan drug designation by the FDA for the treatment of AML and BPDCN and by the EMA for the treatment of BPDCN. In the U.S., if mirvetuximab receives FDA marketing approval for the use for which the orphan drug status was granted, we could be entitled to seven years of market exclusivity that would begin on the date of approval. In the EU, orphan designation could provide us with ten years of market exclusivity that would begin after mirvetuximab receives marketing authorization for the use for which it was granted. We may pursue these designations for other indications for other product candidates intended for qualifying patient populations.

Expedited Review and Approval; Breakthrough Therapy Designation

The FDA has various programs, including Fast Track and accelerated approval, that are intended to expedite or simplify the process for reviewing drugs, and/or provide for approval on the basis of surrogate endpoints. Even if a drug qualifies for one or more of these programs, the FDA may later decide that the drug no longer meets the conditions for qualification or that the time period for FDA review or approval will not be shortened. Generally, drugs that may be eligible for these programs are those for serious or life-threatening conditions, those with the potential to address unmet medical needs, and those that offer meaningful benefits over existing treatments. For example, Fast Track is a process designed to facilitate the development, and expedite the review, of drugs to treat serious diseases and fill an unmet medical need. The request may be made at the time of IND submission and generally no later than the pre-BLA or pre-NDA meeting. The FDA will respond within 60 calendar days of receipt of the request. Although Fast Track does not affect the standards for approval, the FDA will attempt to facilitate early and frequent meetings with a sponsor of a Fast Track designated drug.

Breakthrough Therapy designation is designed to expedite the development and review of drugs that are intended to treat a serious condition where preliminary clinical evidence indicates that the drug may demonstrate substantial improvement over available therapy on a clinically significant endpoint(s). A sponsor may request Breakthrough Therapy designation at the time that the IND is submitted, or no later than at the end-of-Phase 2 meeting.

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The FDA will respond to a Breakthrough Therapy designation request within sixty days of receipt of the request. A drug that receives Breakthrough Therapy designation is eligible for all fast track designation features, intensive guidance on an efficient drug development program, beginning as early as Phase I, and commitment from the FDA involving senior managers. In October 2020, we announced that the FDA granted Breakthrough Therapy designation for pivekimab for the treatment of patients with relapsed or refractory BPDCN.

Accelerated approval provides an earlier approval of drugs to treat serious diseases, and that fill an unmet medical need based on a surrogate endpoint that is reasonably likely to predict clinical benefit. The FDA may grant accelerated approval to a product designed to treat a serious or life-threatening condition that demonstrates an effect on a surrogate endpoint is a marker, such as a laboratory measurement, radiographic image, physical sign, or other measure that is thought to predict clinical benefit, but is not itself a measure of clinical benefit or on an intermediate clinical endpoint that is reasonably likely to predict an effect on irreversible morbidity, mortality, or other clinical benefit. Discussions with the FDA about the feasibility of an accelerated approval typically begin early in the development of the drug in order to identify, among other things, an appropriate endpoint. Accelerated approval does not change the standards for approval, but may expedite the approval process. As a condition of approval, the FDA may require that a sponsor of a drug receiving accelerated approval perform post-marketing clinical trials to confirm the appropriateness of the surrogate marker trial. Failure to conduct required post-approval studies, confirm a clinical benefit during post-marketing studies, or dissemination of false or misleading promotional materials would allow the FDA to withdraw the product from the market on an expedited basis. All promotional materials for therapeutic candidates approved under accelerated regulations are subject to prior review by the FDA. Based on the results of SORAYA, we expect to submit an application for accelerated approval of mirvetuximab in the applicable patient population to the FDA. If we receive accelerated approval, we plan to seek full approval on the basis of the confirmatory Phase 3 MIRASOL trial.

Post-Approval Requirements

Once an approval is granted, the sponsor will be required to comply with all post-approval regulatory requirements as well as any specific post-approval commitments that the sponsor has undertaken as part of the approval process. After approval, some types of changes to the approved product, such as adding new indications, certain manufacturing changes, additional labeling claims, and required additional testing are subject to further FDA review and approval. Drug manufacturers and other entities involved in the manufacture and distribution of approved drugs are required to register their establishments with the FDA and certain state agencies and are subject to periodic unannounced inspections by the FDA and certain state agencies for compliance with cGMP and other laws and regulations. We rely, and expect to continue to rely, on third parties for the production of clinical and commercial quantities of our products. Future inspections by the FDA and other regulatory agencies may identify compliance issues at the facilities of our contract manufacturers that may disrupt production or distribution or require substantial resources to correct.

Any drug products manufactured or distributed by us or our partners pursuant to FDA approvals are subject to continuing regulation by the FDA, including, among other things, record-keeping requirements, reporting of adverse experiences with the drug, providing the FDA with updated safety and efficacy information, drug sampling and distribution requirements, complying with certain electronic records and signature requirements, and complying with FDA promotion and advertising requirements. Compliance with these requirements will require us to expend significant time, money, and effort.

FDA strictly regulates labeling, advertising, promotion, and other types of information on products that are placed on the market. Drugs may be promoted only for the approved indications and in accordance with the provisions of the approved label. If a company, including any agent of the company or anyone speaking on behalf of the company, is found to have promoted the drug for an indication that is not in the approved label, the company may become subject to adverse public relations and administrative and judicial enforcement by the FDA, the Department of Justice, or the Office of the Inspector General of the Department of Health and Human Services, as well as state authorities. This could subject a company to a range of penalties that could have a significant commercial impact, including civil and criminal fines and agreements that materially restrict the manner in which a company promotes or distributes drug products. The federal government has levied large civil and criminal fines against companies for alleged improper promotion and has also requested that companies enter into consent decrees or permanent injunctions under which specified promotional conduct is changed or curtailed.

The FDA may withdraw an approval if compliance with regulatory standards is not maintained or if problems occur after the product reaches the market. Later discovery of previously unknown problems with a product, including adverse events of unanticipated severity or frequency, or with manufacturing processes, may result in revisions to the approved labeling to add new safety information, requirements to conduct post-market studies or clinical trials to assess

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new safety risks, or imposition of distribution or other restrictions under a REMS. Other potential consequences include, among other things:

From time to time, legislation is drafted, introduced, and passed in Congress that could significantly change the statutory provisions governing the approval, manufacturing, and marketing of products regulated by the FDA. It is impossible to predict whether further legislative changes will be enacted, or FDA regulations, guidance, or interpretations changed, or what the impact of such changes, if any, may be.

Other Healthcare Laws

In the U.S., activities of pharmaceutical manufacturers are subject to numerous other federal, state, and local laws designed to, for example, prevent fraud and abuse; promote transparency in interactions with others in the healthcare industry; protect the privacy of individual information; and ensure integrity of research or protect human subjects involved in research. These laws are enforced by various federal and state enforcement authorities.

Although we currently have no products approved for commercial sale, if we obtain marketing approval for any product candidates in the future, we may be subject to various federal and state laws pertaining to health care “fraud and abuse,” including anti-kickback laws (which typically prohibit soliciting, offering, receiving, or paying anything of value to generate healthcare business), and false claims laws (which generally prohibit anyone from knowingly and willingly presenting, or causing to be presented, any false or fraudulent claims for payment for reimbursed drugs or services to third-party payors (including Medicare and Medicaid)). Laws and regulations have also been enacted by the federal government and various states to regulate the sales and marketing practices of pharmaceutical manufacturers with marketed products, including laws that require manufacturers to adopt certain compliance standards or to disclose financial interactions with health care providers to the government and public. Although the specific provisions of these laws vary, their scope is generally broad and there may not be regulations, guidance, or court decisions that apply the laws to particular industry practices.

Given the lack of clarity in laws and their implementation, any future activities (if we obtain approval and/or reimbursement from federal healthcare programs for our product candidates) could be subject to challenge.

We may be subject to privacy and security laws in the various jurisdictions in which we operate, obtain, or store personally identifiable information. Numerous U.S. federal and state laws govern the collection, use, disclosure, and storage of personal information. See “Risk Factors - Risks Related to Our Business and Industry”.

If our operations are found to be in violation of any of such laws or any other governmental regulations that apply to us, we may be subject to penalties, including, without limitation, administrative, civil and criminal penalties, damages, fines, disgorgement, the curtailment or restructuring of our operations, exclusion from participation in federal and state healthcare programs, and imprisonment, any of which could adversely affect our ability to operate our business and our financial results.

Foreign Regulation

In addition to regulations in the U.S., we will be subject to a variety of foreign regulations governing clinical trials and commercial sales and distribution of our products. Whether or not we obtain FDA approval for a product, we must obtain approval by the comparable regulatory authorities of foreign countries or economic areas, such as the European Union, before we may commence clinical trials or market products in those countries or areas. The approval process and requirements governing the conduct of clinical trials, product licensing, pricing, and reimbursement vary greatly from place to place, and the time may be longer or shorter than that required for FDA approval.

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Under European Union regulatory systems, a company may submit marketing authorization applications either under a centralized or decentralized procedure. The centralized procedure, which is compulsory for medicinal products produced by biotechnology or those medicinal products containing new active substances for specific indications such as the treatment of AIDS, cancer, neurodegenerative disorders, diabetes, viral diseases, and designated orphan medicines, and optional for other medicines which are highly innovative. Under the centralized procedure, a marketing application is submitted to the EMA where it will be evaluated by the Committee for Medicinal Products for Human Use. A favorable opinion typically results in the grant by the EMA of a single marketing authorization that is valid for all European Union member states within 67 days of receipt of the opinion. The initial marketing authorization is valid for five years, but once renewed is usually valid for an unlimited period. The decentralized procedure provides for approval by one or more “concerned” member states based on an assessment of an application performed by one member state, known as the “reference” member state. Under the decentralized approval procedure, an applicant submits an application, or dossier, and related materials to the reference member state and concerned member states. The reference member state prepares a draft assessment and drafts of the related materials within 120 days after receipt of a valid application. Within 90 days of receiving the reference member state’s assessment report, each concerned member state must decide whether to approve the assessment report and related materials. If a member state does not recognize the marketing authorization, the disputed points are eventually referred to the EMA, whose decision is binding on all member states.

As in the U.S., we may apply for designation of a product as an orphan drug for the treatment of a specific indication in the European Union before the application for marketing authorization is made. Orphan drugs in Europe enjoy economic and marketing benefits, including up to 10 years of market exclusivity for the approved indication unless another applicant can show that its product is safer, more effective, or otherwise clinically superior to the orphan-designated product.

Reimbursement

Significant uncertainty exists regarding the coverage and reimbursement status of products approved by the FDA and other government authorities. Sales of our products will depend, in part, on the availability of coverage and the adequacy of reimbursement from third-party payors.

Within the U.S., third-party payors include government authorities or government healthcare programs, such as Medicare and Medicaid (which provides prescription drug benefits to low income individuals), and private entities, such as managed care organizations, private health insurers and other organizations. Third-party payors may limit coverage of certain drug products or may manage utilization of a particular product (e.g., by requiring pre-approval (known as “prior authorization”) for coverage of particular prescriptions (to allow the payor to assess medical necessity)). A third-party payor's decision to provide coverage for a drug product does not mean that an adequate reimbursement rate will be approved. Adequate third-party reimbursement may not be available to enable us to maintain net price levels sufficient to realize an appropriate return on our investment in product development. Additionally, coverage and reimbursement for drug products can differ significantly from payor to payor. One third-party payor’s decision to cover a particular drug product or service does not ensure that other payors will also provide coverage for the medical product or service or will provide coverage at an adequate reimbursement rate.

Third-party payors are increasingly challenging the price and examining the cost-effectiveness of new products and services in addition to their safety and efficacy. To obtain or maintain coverage and reimbursement for any drug product for which we obtain approval, we may need to collect real world evidence and conduct pharmacoeconomic studies to demonstrate the medical necessity and cost-effectiveness of our product. These studies will be in addition to the studies required to obtain or maintain regulatory approvals. If third-party payors do not consider a product to be cost-effective compared to other available therapies, they may not cover the product or, if they do, the level of payment may not be sufficient to allow sale of a product at a profit. Thus, obtaining and maintaining reimbursement status is complex and costly.

Within the U.S., for any approved products, we may be required to provide discounts or rebates under government healthcare programs or to certain government and private purchasers in order to obtain coverage under federal healthcare programs such as Medicare and Medicaid or to sell products to government purchasers.

In the U.S., there have been ongoing efforts by federal and state governments to reform delivery of, or payment for, health care, which include initiatives to reduce the cost of healthcare and drugs specifically. See “Risks Related to Government Regulation - Unfavorable pricing regulations, third-party reimbursement practices, or healthcare reform initiatives applicable to our product candidates could limit our potential product revenue.” Healthcare reform efforts or any future legislation or regulatory actions aimed at controlling and reducing healthcare costs, including through measures designed to limit reimbursement, restrict access, or impose unfavorable pricing modifications on

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pharmaceutical products, could impact our ability to obtain or maintain coverage and adequate reimbursement for our product candidates, if approved, which could materially harm our business and financial results.

In addition, in some foreign countries, the proposed pricing for a drug must be approved before it may be lawfully marketed. The requirements governing drug pricing vary widely from country to country. For example, the European Union provides options for its member states to restrict the range of medicinal products for which their national health insurance systems provide reimbursement and to control the prices of medicinal products for human use. A member state may approve a specific price for the medicinal product, or it may instead adopt a system of direct or indirect controls on the profitability of the company placing the medicinal product on the market. There can be no assurance that any country that has price controls or reimbursement limitations for pharmaceutical products will allow favorable reimbursement and pricing arrangements for any of our products. Historically, products launched in the European Union do not follow price structures of the U.S. and generally tend to be significantly lower.

Manufacturing

We contract with third-party contract manufacturers (CMOs) for the manufacture of our product candidates for both our clinical and potential commercial needs. Our CMO network manufactures antibody, linker, and payload, and conjugates the foregoing to create bulk drug substance of our product candidates and processes the bulk drug substance into vialed and labeled drug product for use in humans. Although we are reliant on third parties to manufacture our product candidates, we have personnel with extensive manufacturing experience to oversee the relationships with our CMOs.

CMOs are subject to extensive governmental regulations, and we depend on them to manufacture our product candidates in accordance with cGMP. We have an established quality assurance program designed to ensure that the CMOs involved in the manufacture of product candidates do so in accordance with cGMP and other applicable U.S. and foreign regulations. We believe that our current CMO network complies with such regulations.

Information about our Executive Officers

ImmunoGen’s executive officers are appointed by the Board of Directors at the first meeting of the Board following the annual meeting of shareholders or at other Board meetings as appropriate and hold office until the first Board meeting following the next annual meeting of shareholders and until a successor is chosen, subject to prior death, resignation, or removal. Information regarding our executive officers is presented below. Ages are as of December 31, 2021.

Mark J. Enyedy, age 58, joined ImmunoGen in 2016, and has served as our President and Chief Executive Officer since that time. Prior to joining ImmunoGen, he served in various executive capacities at Shire PLC, a pharmaceutical company, from 2013 to 2016, including as Executive Vice President and Head of Corporate Development from 2014 to 2016, where he led Shire’s strategy, M&A, and corporate planning functions and provided commercial oversight of Shire’s pre-Phase 3 portfolio. Prior to joining Shire, he served as Chief Executive Officer and a director of Proteostasis Therapeutics, Inc., a biopharmaceutical company, from 2011 to 2013. Prior to joining Proteostasis, he served for 15 years at Genzyme Corporation, a biopharmaceutical company, most recently as President of the Transplant, Oncology, and Multiple Sclerosis divisions. Mr. Enyedy holds a JD from Harvard Law School and practiced law prior to joining Genzyme. Mr. Enyedy is also a director of LogicBio Therapeutics, Inc., Ergomed PLC, the Biotechnology Innovation Organization (BIO), and The American Cancer Society of Eastern New England. Within the past five years, he also served as a director of Akebia Therapeutics, Inc., Fate Therapeutics, Inc., and Keryx Biopharmaceuticals, Inc.

Susan Altschuller, PhD, age 40, joined ImmunoGen in July 2020, and has served as our Senior Vice President and Chief Financial Officer since that time. Dr. Altschuller joined ImmunoGen from Alexion Pharmaceuticals, where she served as Head of Investor Relations, and later, Head of Enterprise Finance. Prior to joining Alexion, Dr. Altschuller was Head of Investor Relations at Bioverativ, where she served as the primary interface with Wall Street and led all investor-related activities for the launch of the Biogen spin-off in 2017. Early in her career, Dr. Altschuller held positions at Biogen in various functions of increasing responsibility, including investor relations, corporate finance, and commercial finance. Dr. Altschuller holds a PhD in Biomedical Engineering from the Illinois Institute of Technology and an MBA from the MIT Sloan School of Management. Dr. Altschuller also serves as a director of Vestaron Corporation.

Anna Berkenblit, MD, age 52, joined ImmunoGen in 2015, and has served as our Senior Vice President and Chief Medical Officer since 2019. Prior to that, she served as our Vice President and Chief Medical Officer from 2015 to 2019. Prior to joining ImmunoGen, she served as Senior Vice President and Head of Clinical Research at H3 Biomedicine Inc., a pharmaceutical company, from 2013 to 2015. Dr. Berkenblit holds a Doctor of Medicine degree

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from Harvard Medical School and a master’s degree from the Harvard/MIT Health & Sciences clinical investigator training program. Dr. Berkenblit is also a director of Surrozen, Inc.

Stacy Coen, age 51, joined ImmunoGen in June 2020, and has served as our Senior Vice President and Chief Business Officer since that time. Ms. Coen joined ImmunoGen from Editas Medicine, a biopharmaceutical company, where she served as Vice President of Business Development, from 2017 to 2020. Prior to that, she spent twenty years in roles of increasing responsibility in the area of business development at Sanofi Genzyme, a pharmaceutical company, from 1997 to 2017. Ms. Coen holds an MBA, Business Management, Finance, and Healthcare, from the University of Virginia, Darden Graduate School of Business Administration. Ms. Coen currently serves as a member of the board of directors of FibroBiologics and as a member of the Board of Trustees of the Huntington’s Disease Society of America.

Kristen Harrington-Smith, age 49, joined ImmunoGen in November 2021, and has served as our Senior Vice President and Chief Commercial Officer since that time. Ms. Harrington-Smith joined ImmunoGen from Novartis Pharmaceuticals, a pharmaceutical company, where she served as Vice President and US Commercial Head of Hematology from 2020 to 2021. In this role, she led the commercial teams responsible for a broad portfolio of therapies in both benign and malignant hematologic diseases. In her previous role at Novartis, Ms. Harrington-Smith was the Vice President and US Commercial Head of CAR-T from 2016 to 2020, launching KYMRIAH^®, the first chimeric antigen receptor (CAR) T-cell therapy, building management, sales, marketing, and market access teams. Ms. Harrington-Smith received a BA from Williams College and an MBA from the Kenan-Flagler Business School at the University of North Carolina. Ms. Harrington-Smith also serves as a member of the board of directors of eFFECTOR Therapeutics.

Theresa G. Wingrove, PhD, age 64, joined ImmunoGen in 2011, and has served as our Senior Vice President, Regulatory Affairs and Quality since 2018. Prior to that she served as our Vice President, Regulatory Affairs and Quality from 2017 to 2018, and prior to that as our Vice President, Regulatory Affairs for more than five years. Dr. Wingrove holds a PhD in biochemical toxicology from the University of Rochester School of Medicine and Dentistry and completed her postdoctoral work at the University of Rochester Medical Center.

Human Capital Resources

As of December 31, 2021, we had 106 full-time employees, of whom 75 were engaged in research and development activities. Of the 75 research and development employees, 56 employees hold post-graduate degrees, of which 20 hold Ph.D. degrees and 4 hold M.D. degrees. We consider our relations with our employees to be good. None of our employees is covered by a collective bargaining agreement. We have entered into confidentiality agreements with all of our employees, members of our board of directors, and consultants. Further, we have entered into assignment of invention agreements with all of our employees.

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Our key human capital management objectives are to attract, retain, and develop the highest quality talent. To support these objectives, our human resources programs are designed to acquire talent to create a high-performing and diverse workforce; develop employees to prepare them for critical roles and leadership positions for the future; reward and support employees through competitive pay and benefits; and enhance our culture through efforts aimed at making the workplace more engaging and inclusive. At ImmunoGen, prejudice, racism, and intolerance are unacceptable. We are committed to diversity, equity, and inclusion across all aspects of our organization, including in our hiring, promotion, and development practices.

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Corporate Information

We were organized as a Massachusetts corporation in March 1981. Our principal offices are located at 830 Winter Street, Waltham, Massachusetts 02451, and our telephone number is (781) 895-0600. Our internet address is www.immunogen.com. Our annual reports on Form 10-K, quarterly reports on Form 10-Q and current reports on Form 8-K, and all amendments to those reports, are available to you free of charge through the “Investors & Media – Financials & Filings - SEC Filings” section of our website as soon as reasonably practicable after those materials have been electronically filed with, or furnished to, the Securities and Exchange Commission. Please note that the information contained on the web site is not a part of this annual report on Form 10-K.

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Additional funding may not be available to us in sufficient amounts, on favorable terms, or at all. We may raise additional funds through public or private financings, collaborative arrangements, or other arrangements. Any additional fundraising efforts may divert our management from their day-to-day activities, which may adversely affect our ability to develop and commercialize our product candidates. Volatility in the financial markets has generally made equity and debt financing more difficult to obtain and may have a material adverse effect on our ability to meet our fundraising needs. Moreover, the terms of any financing may adversely affect the holdings or the rights of our shareholders and the issuance of additional securities, whether equity or debt, by us, or the possibility of such issuance, may cause the market price of our shares to decline. Debt financing, if available, may involve covenants that could restrict our business activities. If we are unable to raise additional funds through equity or debt financing when needed, we may be required to delay, scale back, or eliminate expenditures for some of our development programs, including restructuring our operations, refinancing or restructuring our debt, or grant rights to develop and market product candidates that we would otherwise prefer to internally develop and market. If we are required to grant such rights, the ultimate value of these product candidates to us may be reduced.

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Our ability to use our net operating loss carryforwards and certain other tax attributes to offset future taxable income may be limited.

Under Sections 382 and 383 of the Internal Revenue Code of 1986, as amended, a corporation that undergoes an “ownership change,” is subject to limitations on its ability to use its pre-change net operating loss carryforwards (NOLs), and other pre-change tax attributes (such as research tax credits) to offset its post-change income or taxes. For these purposes, an ownership change generally occurs where the equity ownership of one or more shareholders or groups of shareholders who own at least 5% of a corporation’s stock increases its ownership by more than 50 percentage points over its lowest ownership percentage within a three-year period. We may have experienced such ownership changes in the past, and we may experience shifts in our stock ownership, some of which are outside ImmunoGen’s control. These ownership changes may subject our existing NOLs or credits to substantial limitations under Sections 382 and 383. Accordingly, we may not be able to utilize a material portion of our NOLs or credits. As of December 31, 2021, we had federal NOLs of $471.6 million available to reduce federal taxable income, if any, that begin to expire in 2028 through 2037, and $536.6 million of federal NOLs that can be carried forward indefinitely. As of December 31, 2021, we also had $77.9 million of federal credit carryforwards that expire beginning in 2023. Limitations on our ability to utilize those NOLs to offset U.S. federal taxable income could potentially result in increased future tax liability to us. In addition, at the state level, there may be periods during which the use of NOLs is suspended or otherwise limited, which could accelerate or permanently increase state taxes owed.

Risks Related to Our Business and Industry

A pandemic, epidemic, or outbreak of an infectious disease, such as the COVID-19 pandemic, may materially and adversely affect our business and our financial results.

The spread of COVID-19 has affected the global economy, our operations, clinical trial activities, and supply chain and may continue to do so. The current outbreak of COVID-19 has spread worldwide, including countries where we are currently conducting our clinical trials, including our MIRASOL trial. The COVID-19 pandemic is still evolving, and to date has led to the implementation of various responses, including government-imposed quarantines, travel restrictions, and other public health safety measures, as well as reported adverse impacts on healthcare resources, facilities, and providers across the United States, and in other countries worldwide. The continued impact of COVID-19 may result in a period of business disruption, including delays in our clinical trials or delays or disruptions in our supply chain.

The continued impact of COVID-19 globally could adversely affect our clinical trial operations in the United States and elsewhere, including our ability to recruit and retain patients, principal investigators, and site staff who, as healthcare providers, may have heightened exposure to COVID-19. For example, COVID-19 slowed site activation and patient enrollment for both SORAYA and MIRASOL, which resulted in a limited delay in patient accrual for each of these studies. Even with the approval of vaccines for COVID-19, the pandemic may further delay enrollment in trials due to prioritization of hospital resources toward the pandemic, restrictions on travel, and some patients may be unwilling to enroll in our trials or be unable to comply with clinical trial protocols if quarantines or travel restrictions impede patient movement or interrupt healthcare services, which would delay our ability to conduct clinical trials or release clinical trial results. In addition, there could be a potential effect of COVID-19 to the business at FDA or other health authorities, which could result in delays of reviews and approvals, including with respect to our product candidates. COVID-19 may also affect employees of third-party contract research organizations located in affected geographies that we rely upon to carry out our clinical trials. The continuation of the COVID-19 pandemic, including the development of new variants of the virus, or the spread of another infectious disease, could also negatively affect the

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operations at our third-party manufacturers, which could result in delays or disruptions in the supply of our product candidates if we need additional materials. Additionally, interruption in the manufacture and/or global shipping affecting the transport of clinical trial materials, such as patient samples, product candidates, and other supplies used in our clinical trials may negatively affect our trials.

The trading prices for our common stock and other biotechnology companies have also been highly volatile as a result of the COVID-19 pandemic. We, therefore, may face difficulties raising capital through sales of our common stock or equity linked to our common stock, or such sales may be on unfavorable terms or unavailable.

We cannot presently predict the scope and severity of any additional potential business shutdowns or disruptions as a result of the COVID-19 pandemic, including due to new variants of COVID-19. If we or any of the third parties with whom we engage, however, were to experience further shutdowns or other business disruptions, our ability to conduct our business in the manner and on the timelines presently planned could be materially and negatively affected, which could have a material adverse impact on our business and our results of operation and financial condition.

If our Antibody-Drug Conjugate technology does not produce safe, effective, and commercially viable products or if such products fail to obtain or maintain FDA approval, our business will be severely harmed.

Our ADC technology yields novel product candidates for the treatment of cancer. To date, only one ADC using our technology, KADCYLA, has obtained marketing approval. Our ADC product candidates and/or our collaborators’ ADC product candidates may not prove to be safe, effective, or commercially viable treatments for cancer and as a result, our ADC technology may not result in any future meaningful benefits to us or for our current or potential collaborators. Furthermore, we are aware of only a limited number of other compounds that are based on technology similar to our ADC technology that have obtained marketing approval by the FDA. If our ADC technology fails to generate product candidates that are safe, effective, and commercially viable treatments for cancer or such product candidates fail to obtain or maintain FDA approval, our business will be severely harmed. 

Clinical trials for our product candidates and those of our collaborators will be lengthy and expensive, and their outcome is uncertain.

Before obtaining regulatory approval for the commercial sale of any product candidates, we and our collaborators must demonstrate through clinical testing that our product candidates are safe and effective for use in humans. Conducting clinical trials is a time-consuming, expensive, and uncertain process and typically requires years to complete. In our industry, the results from preclinical studies and early clinical trials often are not predictive of results obtained in later-stage clinical trials. Some compounds that have shown promising results in preclinical studies or early clinical trials subsequently fail to establish sufficient safety and efficacy data necessary to obtain regulatory approval. For example, despite encouraging results from earlier clinical trials of mirvetuximab, our FORWARD I Phase 3 clinical trial evaluating mirvetuximab compared to chemotherapy in women with FRα-positive, platinum-resistant ovarian cancer, did not meet the primary endpoint in either the entire treatment population or the pre-specified high FRα expression population. Based on post hoc exploratory analyses of the FORWARD I results and consultations with the FDA, we implemented two new trials of mirvetuximab, SORAYA and MIRASOL, to support the potential approval of mirvetuximab as a monotherapy. We reported positive top-line data from our SORAYA trial, however, results from our ongoing MIRASOL study may not show positive results consistent with our SORAYA trial, post hoc exploratory analyses of the FORWARD I results, or earlier successful trials of mirvetuximab as monotherapy which would cause significant harm to our business and future prospects.

Before we can commence clinical trials for a therapeutic candidate, we must conduct extensive preclinical testing and studies and submit an IND to FDA. We cannot be sure that submission of an IND will result in the FDA allowing our clinical trials to begin on the timelines we expect, if at all, as FDA may require additional preclinical, toxicology, or other in vivo or in vitro data to support the IND. Additionally, at any time during the clinical trials, we, our collaborators, or the FDA or other regulatory authority might delay or halt any clinical trials of our product candidates for various reasons, including:

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Any failure or substantial delay in successfully completing clinical trials and obtaining regulatory approval for our product candidates or our collaborators’ product candidates could severely harm our business.

Interim, top-line, or preliminary data from our clinical trials that we announce may change as more patient data become available and are subject to audit and verification procedures that could result in material changes in the final data.

From time to time, we have publicly disclosed, and in the future will disclose, preliminary or top-line data from our preclinical studies and clinical trials, which are based on preliminary analyses of then- available data, and the results and related findings and conclusions are subject to change following a more comprehensive review of the data related to the particular study or trial. We also make assumptions, estimations, calculations, and conclusions as part of our analyses of data, and we may not have received or had the opportunity to fully and carefully evaluate all data. Therefore, final results from the studies may differ from the top-line results initially reported, and the final results may indicate different conclusions once additional data have been evaluated. As such, top-line data should be viewed with caution until the final data are available.

From time to time, we may also disclose interim data from our preclinical studies and clinical trials. Interim data from clinical trials that we may complete are subject to the risk that one or more of the outcomes may materially change as patient enrollment continues and more data become available. Adverse differences between top-line, preliminary, or interim data, on the one hand, and final data, on the other, could significantly harm our business prospects. Further, disclosure of interim data by us or by our competitors could result in volatility in the price of our common stock.

Further, others, including regulatory agencies, may not accept or agree with our assumptions, estimates, calculations, conclusions, or analyses, or may interpret or weigh the importance of data differently, which could negatively affect the approvability or commercialization of the particular product candidate.

In addition, the information we choose to publicly disclose regarding a particular study or clinical trial is based on what is typically extensive information, and you or others may not agree with what we determine is material or otherwise appropriate information to include in our disclosure. If the final results differ from the interim, top-line, or preliminary data, or if others, including regulatory authorities, disagree with the conclusions reached, our ability to obtain approval for, and to commercialize, our product candidates may be harmed, which may negatively affect our business, financial condition, results of operations, and prospects.

If our product candidates or those of our collaborators do not gain market acceptance, our business will suffer.

Even if clinical trials demonstrate the safety and efficacy of our product candidates, including mirvetuximab, and those of our collaborators, and the necessary regulatory approvals are obtained, our and our collaborators’ products may not gain market acceptance among physicians, patients, healthcare payers, and other members of the medical community. The degree of market acceptance of any products that we or our collaborators develop will depend on a number of factors, including:

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Physicians may not prescribe any of our future products until such time as clinical data or other factors demonstrate the safety and efficacy of those products as compared to conventional drugs and other treatments. Even if the clinical safety and efficacy of our products are established, physicians may elect not to recommend the therapies for any number of other reasons, including whether the physicians are already using competing products that satisfy their treatment objectives. If our products do not achieve significant market acceptance and use, we will not be able to recover the significant investment we have made in developing such products and our business will be severely harmed.

We currently do not have the direct sales, marketing, or distribution capabilities necessary to successfully commercialize our products on a large scale and may be unable to establish such capabilities.

We currently intend to commercialize mirvetuximab ourselves in the United States and the European Union. We may choose to rely on third parties to market and sell mirvetuximab outside of the United States and the European Union, either through distributor or outlicensing arrangements. For example, in October 2020, we entered into a collaboration and license agreement with Huadong under which Huadong will exclusively develop and commercialize mirvetuximab in Greater China. We retain all rights to mirvetuximab in the rest of the world. At this time, we do not have any significant direct sales, marketing, or distribution capabilities. In addition, arrangements with third parties to develop and commercialize mirvetuximab or other future potential products could significantly limit the revenues we derive from these compounds, and these third parties, including Huadong, may fail to commercialize our compounds successfully.

We face product liability risks and may not be able to obtain adequate insurance.

The use of our product candidates during testing or after approval entails an inherent risk of adverse effects, which could expose us to product liability claims. Regardless of their merit or eventual outcome, product liability claims may result in:

We may not have sufficient resources to satisfy any liability resulting from these claims. While we currently have product liability insurance for products that are in clinical testing, our coverage may not be adequate in scope to protect us in the event of a successful product liability claim. Further, we may not be able to maintain our current insurance, increase our insurance coverage as may be needed, or obtain general product liability insurance on reasonable terms and at an acceptable cost if we or our collaborators begin commercial production of our proposed product candidates, including mirvetuximab. This insurance, even if we can obtain and maintain it, may not be sufficient to provide us with adequate coverage against potential liabilities. If we are unable to maintain sufficient insurance coverage at an acceptable cost or to otherwise protect against potential product liability claims, it could prevent or inhibit the development and commercial production and sale of our proposed product candidates, which could severely harm our business.

We may be unable to compete successfully.

The markets in which we compete are well-established and intensely competitive. We may be unable to compete successfully against our current and future competitors. Our failure to compete successfully may result in lower volume sold, pricing reductions, reduced gross margins, and failure to achieve market acceptance for our potential products, including mirvetuximab. Our competitors include research institutions, pharmaceutical companies, and biotechnology companies, such as Pfizer, Seattle Genetics, Roche, Astellas, AstraZeneca, Daiichi Sankyo, GlaxoSmithKline, AbbVie, and the Menarini Group. For example, pivekimab is in development for the treatment of BPDCN and, if approved, would compete with the Menarini Group’s ELZONRIS^® (tagraxofusp), which is approved by the U.S. FDA for sale in the United States and by the EMA for sale in the European Union for the treatment of BPDCN. Many of our competitors have substantially more experience and more capital, research and development, regulatory, manufacturing, human, and other resources than we do. As a result, they may:

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A number of pharmaceutical and biotechnology companies are currently developing products targeting the same types of cancer that we target, and some of our competitors’ products have entered clinical trials or already are commercially available.

Our product candidates, including mirvetuximab, if approved and commercialized, will also compete against well-established, existing therapeutic products that are currently reimbursed by government healthcare programs, private health insurers, and health maintenance organizations. In addition, if our product candidates are approved and commercialized, we may face competition from biosimilars. The ACA, which included the BPCIA, amended the Public Health Service Act to create an abbreviated approval pathway for two types of “generic” biologics—biosimilars and interchangeable biologic products. The BPCIA establishes a pathway for the FDA approval of follow-on biologics and provides twelve years data exclusivity for reference products and an additional six-month exclusivity period if pediatric studies are conducted. In Europe, the EMA has issued guidelines for approving products through an abbreviated pathway, and biosimilars have been approved in Europe. If a biosimilar version of one of our potential products were approved in the United States or Europe, it could have a negative effect on sales and gross profits of the potential product and our financial condition.

We face and will continue to face intense competition from other companies for collaborative arrangements with pharmaceutical and biotechnology companies, for relationships with academic and research institutions, and for licenses to proprietary technology. In addition, we anticipate that we will face increased competition in the future as new companies enter our markets and as scientific developments surrounding antibody-based therapeutics for cancer continue to accelerate. While we will seek to expand our technological capabilities to remain competitive, research and development by others may render our technology or product candidates obsolete or noncompetitive or result in treatments or cures superior to any therapy developed by us.

We have a limited number of authorized and unreserved shares available for future issuance, which may impair our ability to conduct future financings and other transactions.

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Our restated articles of organization, as amended, currently authorizes us to issue up to 300,000,000 shares of common stock and 5,000,000 shares of preferred stock. Following the closing of our December 2021 public offering of common stock, we have a limited number of authorized shares of common stock available for future issuance that are not already issued or reserved for issuance.

If we are unable to enter into new arrangements to issue shares of our common stock or securities convertible or exercisable into shares of our common stock because we do not have a sufficient number of authorized, unissued, and unreserved shares of common stock, our ability to complete equity-based financings or other transactions that involve the potential issuance of our common stock or securities convertible or exercisable into our common stock, will be limited. In lieu of issuing common stock or securities convertible into our common stock in any future equity financing transactions, we may need to issue some or all of our authorized but unissued shares of preferred stock, which would likely have superior rights, preferences, and privileges to those of our common stock, or we may need to issue debt that is not convertible into shares of our common stock, which may require us to grant security interests in our assets and property and/or impose covenants upon us that restrict our business. If we are unable to issue additional shares of common stock or securities convertible or exercisable into our common stock, our ability to enter into strategic transactions such as acquisitions of companies or technologies, may also be limited. If we propose to amend our restated articles of organization, as amended, to increase our authorized shares of common stock, such a proposal would require the approval by the holders of a majority of the shares of our common stock outstanding and entitled to vote, and we cannot assure you that such a proposal would be adopted. If we are unable to complete financing, strategic, or other transactions due to our inability to issue additional shares of common stock or securities convertible or exercisable into our common stock, our financial condition and business prospects may be materially harmed.

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Risks Related to Our Dependence on Third Parties

If our collaborators fail to perform their obligations under our agreements with them or determine not to continue with clinical trials for particular product candidates, our business could be severely affected.

The development and commercialization of our product candidates depends, in part, upon the formation and maintenance of collaborative arrangements. Collaborations provide an opportunity for us to:

If we fail to secure or maintain successful collaborative arrangements, the development and marketing of compounds that use our technology may be delayed, scaled back, or otherwise may not occur. In addition, we may be unable to negotiate other collaborative arrangements or, if necessary, modify our existing arrangements on acceptable terms. We cannot control the amount and timing of resources our collaborators may devote to our product candidates. Our collaborators may separately pursue competing product candidates, therapeutic approaches, or technologies to develop treatments for the diseases targeted by us or our collaborative efforts, or may decide, for reasons that may not be known to us or with which we may disagree, to discontinue development of product candidates under our agreements with them. Any of our collaborators may slow or discontinue the development of a product candidate covered by a collaborative arrangement for reasons that include, but are not limited to:

Even if our collaborators continue their collaborative arrangements with us, they may nevertheless determine not to actively pursue the development or commercialization of any resulting products. Also, our collaborators may fail to perform their obligations under the collaborative agreements or may be slow in performing their obligations. Our collaborators can terminate our collaborative agreements under certain conditions. The decision to advance a product that is covered by a collaborative agreement through clinical trials and ultimately to commercialization is, in some cases, at the discretion of our collaborators. If any collaborative partner were to terminate or breach our agreements, fail to complete its obligations to us in a timely manner, or decide to discontinue its development of a product candidate, our anticipated revenue from the agreement and the development and commercialization of the products could be severely limited or eliminated. If we are not able to establish additional collaborations or any or all of our existing collaborations are terminated and we are not able to enter into alternative collaborations on acceptable terms, or at all, our continued development, manufacture, and commercialization of our product candidates could be delayed or scaled back as we may not have the funds or capability to continue these activities. If our collaborators fail to successfully develop and commercialize ADC compounds, our business prospects could be severely harmed.

If our product requirements for clinical trials or commercialization are significantly higher than we estimated, the inability to procure additional antibody production, conjugation, or fill/finish services in a timely manner could impair our ability to initiate or advance our clinical trials or commercialization of mirvetuximab or any other product candidates.

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We rely on third-party suppliers to manufacture antibodies used in our own proprietary compounds. Due to the specific nature of the antibody and availability of production capacity, there is significant lead time required by these suppliers to provide us with the needed materials. If our antibody requirements for clinical or commercial materials to be manufactured are significantly higher than we estimated, we may not be able to readily procure additional antibody which would impair our ability to advance our clinical trials currently in process or initiate additional trials or commercialize mirvetuximab or any other product candidates. We also rely on third parties to manufacture bulk drug substance and convert it into filled and finished vials of drug product for clinical use. If our product requirements are significantly higher than we estimated, we may not be able to readily procure slots to manufacture bulk drug substance or to convert drug substance into filled and finished vials of drug product for clinical or commercial use. There can be no assurance that we will not have supply problems that could delay or stop our clinical trials, hinder our commercialization efforts, or otherwise could have a material adverse effect on our business.

We are currently contractually required to obtain all of the DM4 used in mirvetuximab from a single third-party manufacturer, and any delay or interruption in such manufacturer’s operations could impair our ability to advance preclinical and clinical trials and commercialization of our product candidates and our collaborators’ products candidates.

We rely on a sole third-party supplier, Società Italiana Corticosteroidi S.r.l, to manufacture the DM4 used in mirvetuximab. Any delay or interruption in the operations of our sole third-party supplier and/or our supply of DM4 could lead to a delay or interruption in our manufacturing operations, preclinical studies, clinical trials, and commercialization of our product candidates and our collaborators’ product candidates, which could negatively affect our business.

We currently rely on, and expect to continue to rely on, third-party manufacturers to produce our antibodies, linkers, payloads, drug substance, and drug product, and any delay or interruption in such manufacturers’ operations could impair our ability to advance clinical trials and commercialization of our product candidates.

We rely on third-party contract manufacturers to produce sufficiently large quantities of drug materials that are and will be needed for clinical trials and commercialization of our potential products. We have established relationships with third-party manufacturers to provide materials for our clinical trials and are developing relationships with these and other third-party manufacturers that we believe will be necessary to continue the development of our product candidates and to supply commercial quantities of these product candidates if they are approved. Third-party manufacturers may not be able to meet our needs with respect to timing, quantity, or quality of materials. If we are unable to contract for a sufficient supply of needed materials on acceptable terms, or if we should encounter delays or difficulties in our relationships with manufacturers, our clinical trials may be delayed, thereby delaying the submission of applications for regulatory approval and the market introduction and subsequent commercialization of our potential products. Any such delays may lower our revenues and potential profitability.

The facilities used to manufacture our product candidates (drug substance and drug product) must be inspected by the FDA (and other similar regulatory agencies outside the United States depending on where marketing authorizations are filed) before marketing authorizations are approved. Often, but not always, these inspections are triggered by marketing authorization submissions. In the United States, if we want to change manufacturers or add additional manufacturers after our product candidate is approved, the FDA must approve a supplemental BLA. We are completely dependent on our contract manufacturers for compliance with cGMPs in connection with the manufacture of our product candidates. If our contract manufacturers cannot successfully manufacture material that conforms to our specifications and the regulatory requirements of the FDA or others, we will not be able to use the products produced at their manufacturing facilities. In addition, we have no control over the ability of our contract manufacturers to maintain adequate quality control, quality assurance, and qualified personnel. If the FDA or a comparable foreign regulatory authority finds that these facilities do not comply with cGMP, we may need to find alternative manufacturing facilities, which would significantly impact our ability to develop, obtain marketing approval for, or market our product candidates, if approved. Further, our failure, or the failure of our third-party manufacturers, to comply with these or other applicable regulations could result in sanctions being imposed on us, including clinical holds, fines, injunctions, civil penalties, delays, suspension or withdrawal of approvals, license revocation, seizures or recalls of product candidates or drugs, if approved, operating restrictions and criminal prosecutions, any of which could significantly and adversely affect our business and supplies of our product candidates.

We depend on a small number of collaborators for a substantial portion of our revenue. The loss of, or a material reduction in activity by, any one of these collaborators could result in a substantial decline in our revenue.

We have and will continue to have collaborations with a limited number of companies. As a result, our financial performance depends, in part, on the efforts and overall success of these companies. Also, the failure of any one of our

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collaborators to perform its obligations under its agreement with us, including making any royalty, milestone, or other payments to us, could have an adverse effect on our financial condition. Further, any material reduction by any one of our collaborators in its level of commitment of resources, funding, personnel, and interest in continued development under its agreement with us could have an adverse effect on our financial condition. If a present or future collaborator of ours were to be involved in a business combination, the collaborator’s continued pursuit and emphasis on our product development program could be delayed, diminished, or terminated.

We depend on our collaborators for the determination of royalty payments. We may not be able to detect errors, and payment calculations may call for retroactive adjustments.

The royalty payments we may receive are determined by our collaborators based on their reported net sales. Each collaborative partner’s calculation of the royalty payments is subject to and dependent upon the adequacy and accuracy of its sales and accounting functions, and errors may occur from time to time in the calculations made by a collaborative partner. Our agreement with Genentech provides us the right to audit the calculations and sales data for the associated royalty payments related to sales of KADCYLA; however, such audits may occur many months following our recognition of the royalty revenue, may require us to adjust our royalty revenues in later periods and generally require audit-related costs on our part.

Royalty rates under our license agreements with our collaborators may vary over the royalty term depending on our intellectual property rights and the existence of certain third-party competing products.

Most of our license agreements with our collaborators provide that the royalty rates are subject to downward adjustment in the absence of ImmunoGen patent rights covering various aspects of the manufacture, use, or sale of the products developed under such licenses, or if certain third-party products compete with the particular product covered by the license agreement.

Risks Related to Our Intellectual Property

If we are unable to protect our intellectual property rights adequately, the value of our technology and our product candidates could be diminished.

Our success depends in part on obtaining, maintaining, and enforcing our patents and other proprietary rights and our ability to avoid infringing the proprietary rights of others. We seek to protect our proprietary position by filing patent applications in the United States and in foreign countries that cover our novel product candidates and their uses, pharmaceutical formulations and dosages, and processes for the manufacture of them. Our patent portfolio currently includes both patents and patent applications. Patent law relating to the scope of claims in the biotechnology field in which we operate is still evolving, is surrounded by a great deal of uncertainty, and involves complex legal, scientific, and factual questions. To date, no consistent policy has emerged regarding the breadth of claims allowed in biotechnology patents. Accordingly, our pending patent applications may not result in issued patents or in patent claims as broad as in the original applications. Although we own numerous patents, the issuance of a patent is not conclusive as to its validity or enforceability. Through litigation, a third party may challenge the validity or enforceability of a patent after its issuance. In addition, the patent prosecution process is expensive and time-consuming. We may not be able to file and prosecute all necessary or desirable patent applications at a reasonable cost or in a timely manner. We may choose not to seek patent protection for certain innovations and may choose not to pursue patent protection in certain jurisdictions. Under the laws of certain jurisdictions, patents or other intellectual property rights may be unavailable or limited in scope. It is also possible that we will fail to identify patentable aspects of our research and development before it is too late to obtain patent protection.

Patents and patent applications owned or licensed by us may become the subject of inter partes review, post-grant review, ex parte reexamination, interference, opposition, nullity, or other proceedings in a court or patent office in the United States or in a foreign jurisdiction to determine validity, enforceability, or priority of invention, which could result in substantial cost to us. An adverse decision in such a proceeding may result in our loss of rights under a patent or patent application. It is unclear how much protection, if any, will result from our patents if we attempt to enforce them or if they are challenged in court or in other proceedings. A competitor may successfully invalidate our patents, or a challenge could result in limitations of the patents’ coverage. The courts continue to interpret various aspects of patent-related laws and related agency rules in ways that we cannot predict, potentially making it easier for competitors and other interested parties to challenge our patents, which, if successful, could have a material adverse effect on our business and prospects. In addition, the cost of litigation or patent office proceedings to uphold the validity of patents can be substantial. If we are unsuccessful in these proceedings, third parties may be able to use our patented technology and may be able to do so without paying us licensing fees or royalties. Moreover, competitors may infringe our patents or successfully avoid them through design innovation. To prevent infringement or unauthorized use, we may need to file

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infringement claims, which are expensive and time-consuming. In an infringement proceeding, a court may decide that a patent of ours is not valid. Even if the validity of our patents were upheld, a court may refuse to stop the other party from using the technology at issue on the ground that its activities are not covered by our patents or that the facts surrounding the other party’s use of our technology do not satisfy the legal requirements to grant such an injunction.

Policing unauthorized use of our intellectual property is difficult, and we may not be able to prevent misappropriation of our proprietary rights, particularly in countries where the laws may not protect such rights as fully as in the United States.

In addition to our patent rights, we also rely on unpatented technology, trade secrets, know-how, and confidential information. Third parties may independently develop substantially equivalent information and techniques or otherwise gain access to or disclose our technology. We may not be able to effectively protect our rights in unpatented technology, trade secrets, know-how, and confidential information. We require each of our employees, consultants, and corporate partners to execute a confidentiality agreement at the commencement of an employment, consulting, or collaborative relationship with us. Further, we require that all employees enter into assignment of invention agreements as a condition of employment. However, these agreements may not provide effective protection of our information, or, in the event of unauthorized use or disclosure, they may not provide adequate remedies. If we are unable to prevent material disclosure of the trade secrets and other intellectual property related to our technologies to third parties, we may not be able to establish or maintain the competitive advantage that we believe is provided by such intellectual property, adversely affecting our market position and business and operational results.

We may incur substantial costs as a result of litigation or other proceedings relating to patent and other intellectual property rights held by third parties and we may be unable to protect our rights to, or to commercialize, our product candidates.

Patent litigation is very common in the biotechnology and pharmaceutical industries. Third parties may assert patent or other intellectual property infringement claims against us with respect to our technologies, products, or other matters. From time to time, we have received correspondence from third parties alleging that, or inquiring whether, we infringe their intellectual property rights. Any claims that might be brought against us alleging infringement of patents may cause us to incur significant expenses and, if successfully asserted against us, may cause us to pay substantial damages and limit our ability to use the intellectual property subject to these claims. Even if we were to prevail, any litigation would be costly and time-consuming and could divert the attention of our management and key personnel from our business operations. Furthermore, as a result of a patent infringement suit, we may be forced to stop or delay developing, manufacturing, or selling potential products that incorporate the challenged intellectual property unless we enter into royalty or license agreements. There may be third-party patents, patent applications, and other intellectual property relevant to our potential products that may block or compete with our products or processes of which we are currently unaware with claims that cover the use or manufacture of our drug candidates or the practice of our related methods. Because patent applications can take many years to issue, there may be currently pending patent applications that may later result in issued patents that our drug candidates may infringe. In addition, we sometimes undertake research and development with respect to potential products even when we are aware of third-party patents that may be relevant to our potential products, on the basis that such patents may be challenged or licensed by us or that the Safe Harbor under 35 U.S.C. 271(e) applies. If our subsequent challenge to such patents were not to prevail, we may not be able to commercialize our potential products after having already incurred significant expenditures unless we are able to license the intellectual property on commercially reasonable terms. We may not be able to obtain such license agreements on terms acceptable to us, if at all. Even if we were able to obtain licenses to such technology, some licenses may be non-exclusive, thereby giving our competitors access to the same technologies licensed to us. Ultimately, we may be unable to commercialize some of our potential products or may have to cease some of our business operations, which could severely harm our business.

Any inability to license proprietary technologies or processes from third parties that we use in connection with the development and manufacture of our product candidates may impair our business.

Other companies, universities, and research institutions have or may obtain patents that could limit our ability to use, manufacture, market, or sell our product candidates or impair our competitive position. As a result, we would have to obtain licenses from other parties before we could continue using, manufacturing, marketing, or selling our potential products. Any necessary licenses may not be available on commercially acceptable terms, if at all. If we do not obtain the required licenses, we may not be able to market our potential products at all or we may encounter significant delays in product development while we redesign products or methods that are found to infringe the patents held by others.

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Risks Related to Government Regulation

We expect to file for approval for mirvetuximab from the FDA through the use of accelerated approval pathways. If unable to obtain approval under an accelerated pathway, we may be required to conduct additional preclinical studies or clinical trials beyond those that we currently contemplate, which could increase the expense of obtaining, and delay the receipt of, necessary marketing approvals. Even if we receive accelerated approval from the FDA, if our confirmatory trials do not verify clinical benefit, or if we do not comply with rigorous post-marketing requirements, the FDA may seek to withdraw accelerated approval.

We are seeking approval for mirvetuximab for the treatment of FRα-high platinum-resistant epithelial ovarian, primary peritoneal, or fallopian tube cancer with one to three prior lines of therapy under the accelerated approval pathway.

The FDA may not accept our application for accelerated approval, may not grant such approval on a timely basis, or may not grant approval at all. The FDA or foreign regulatory authorities may determine that results from the SORAYA trial do not demonstrate an improvement over available therapies or address an unmet need or may otherwise find that our application does not meet the conditions for accelerated approval, including due to insufficient duration or response or unacceptable toxicities, and could require us to conduct further studies prior to considering our application or granting approval of any type. We might not be able to fulfill the FDA’s requirements in a timely manner, which would cause delays, or approval might not be granted because our submission is deemed incomplete by the FDA. A failure to obtain accelerated approval or any other form of expedited development, review, or approval for mirvetuximab would result in a longer time period to commercialization of mirvetuximab, would increase the cost of development of mirvetuximab, and would harm our competitive position in the marketplace.

Moreover, even if we receive accelerated approval from the FDA, we will be subject to rigorous post-marketing requirements, including the completion of confirmatory post-market clinical trial(s) to verify the clinical benefit of mirvetuximab, and submission to the FDA of all promotional materials 30-120 days prior to their dissemination. Products that receive accelerated approval may be subject to expedited withdrawal procedures if post-marketing studies fail to verify the predicted clinical benefit. The FDA could seek to withdraw accelerated approval for multiple reasons, including if we fail to conduct any required post-market study, a post-market study does not confirm the predicted clinical benefit, other evidence shows that the product is not safe or effective under the conditions of use, or we disseminate promotional materials that are found by the FDA to be false or misleading.

Side effects, serious adverse events, or other undesirable properties could arise from the use of mirvetuximab or our other clinical product candidates and, in turn, could delay or halt clinical trials, delay or prevent its regulatory approval, limit the commercial profile of its labeling, if approved, or result in significant negative consequences following any marketing approval.

Undesirable side effects or serious adverse events caused by mirvetuximab or our other clinical product candidates could cause us or regulatory authorities to interrupt, delay, or halt respective clinical trials and could result in a restrictive label or the delay or denial of regulatory approval by the FDA or other comparable foreign regulatory authorities.

Any related drug-side effects or serious adverse events in our clinical trials could affect clinical trial patient recruitment or the ability of enrolled patients to complete the clinical trial or result in potential product liability claims.

In our Phase 3 SORAYA trial evaluating the safety and efficacy of mirvetuximab monotherapy in patients with FRα-high platinum-resistant epithelial ovarian, primary peritoneal, or fallopian tube cancer who had been previously treated with Avastin® (bevacizumab), the most commonly reported treatment-related adverse events included ocular events and low grade gastrointestinal events. Treatment-related adverse events leading to drug discontinuation occurred in 7% of patients.

In the randomized Phase 3 FORWARD I trial evaluating mirvetuximab compared to chemotherapy in women with FRα-positive, platinum-resistant epithelial ovarian, primary peritoneal, or fallopian tube cancer, the most common drug-related adverse events included nausea, blurred vision, and keratopathy.

In the Phase 1b FORWARD II study, doublet combinations of mirvetuximab with carboplatin and with bevacizumab were studied, as well as a triplet of mirvetuximab with carboplatin and bevacizumab. In these combinations, no new safety signals were seen; adverse events observed with the combinations were as expected based on the side effect profiles of each agent and duration of therapy.

Additionally, if mirvetuximab receives marketing approval, and we or others later identify undesirable side

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effects or serious adverse events caused by mirvetuximab, a number of potentially significant negative consequences could result, including:

Any of these events could prevent us from achieving or maintaining market acceptance of mirvetuximab, if approved.

We have received orphan drug designation for mirvetuximab and other product candidates for specified indications; we may seek additional orphan drug designation for additional indications and for our other drug candidates. However, we may be unsuccessful in obtaining or may be unable to maintain the benefits associated with orphan drug designation, including the potential for market exclusivity.

Mirvetuximab has been granted orphan drug designation by the FDA in the United States, and orphan medicinal product status by the EMA in the European Union for the treatment of ovarian cancer. Pivekimab has been granted orphan drug designation by the FDA for the treatment of AML and for the treatment of BPDCN, and by the EMA for the treatment of BPDCN. As part of our business strategy, we may seek orphan drug designation for our other drug candidates; however, we may be unsuccessful.

Generally, if a product with an orphan drug designation subsequently receives the first marketing approval for the indication for which it has such designation, the product is entitled to a period of marketing exclusivity, which precludes the EMA or the FDA from approving another marketing application for the same drug or biologic for that time period. Even if we obtain orphan drug exclusivity for a drug, that exclusivity may not effectively protect the designated drug from competition because different drugs can be approved for the same condition. Even after an orphan drug is approved, the FDA can subsequently approve another product that meets the definition of a “same drug” under 21 C.F.R. 316.3 for the same condition if the FDA concludes that the later product is clinically superior by evidence that it is safer, more effective, or makes a major contribution to patient care. In addition, a designated orphan drug may not receive orphan drug exclusivity if it is approved for a use that is broader than the indication for which it received orphan drug designation. Moreover, orphan drug exclusive marketing rights in the United States may be lost if the FDA later determines that the request for designation was materially defective or if the manufacturer is unable to assure sufficient quantity of the drug to meet the needs of patients with the rare disease or condition. Orphan drug designation neither shortens the development time or regulatory review time of a drug nor gives the drug any advantage in the regulatory review or approval process. While we intend to seek additional orphan drug designation for our other drug candidates, we may never receive such designations. Even if we receive orphan drug designation for any of our drug candidates, there is no guarantee that we will enjoy the benefits of those designations or obtain orphan drug exclusivity.

We and our collaborators are subject to extensive government regulations and we and our collaborators may not be able to obtain necessary regulatory approvals.

We and our collaborators may not receive the regulatory approvals necessary to commercialize our product candidates, which would cause our business to be severely harmed. Pharmaceutical product candidates, including those in development by us and our collaborators, are subject to extensive and rigorous government regulation. The FDA regulates, among other things, the development, testing, manufacture, safety, record-keeping, labeling, storage, approval, advertising, promotion, sale, and distribution of pharmaceutical products. If our potential products or our collaborators’ potential products are marketed outside of the United States, they will also be subject to extensive regulation by foreign governments. The regulatory review and approval process, which includes preclinical studies and clinical trials of each product candidate, is lengthy, complex, expensive, and uncertain. Securing regulatory approval requires the submission

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of extensive preclinical and clinical data and supporting information to the authorities for each indication to establish the product candidate’s safety and efficacy. Data obtained from preclinical and other nonclinical studies and clinical trials are susceptible to varying interpretation, which may delay, limit, or prevent regulatory approval. The approval process may take many years to complete and may involve ongoing requirements for post-marketing studies. FDA may approve our product for indications that are significantly more limited than what we apply for or require labeling statements that limit the use of our products, such as a boxed warning or the addition of labeling statements, including warnings, contra-indications, or precautions. FDA may also require a REMS, which could include physician communication plans or restricted distribution methods, such as training, certification, or other requirements for prescribers, pharmacies, or patients. Any FDA or other regulatory approvals of our or our collaborators’ product candidates, once obtained, may be withdrawn or limited. Any of these actions could diminish the usage of the product or otherwise limit the commercial success of our products. The effect of government regulation may be to:

We may encounter delays or rejections in the regulatory approval process because of additional government regulation from future legislation or administrative action or changes in regulatory policy during the period of product development, clinical trials, and regulatory review. Failure to comply with applicable regulatory requirements may result in criminal prosecution, civil penalties, recall or seizure of products, total or partial suspension of production or injunction, as well as other regulatory action against our product candidates or us. In addition, we are, or may become, subject to various federal, state, and local laws, regulations, and recommendations relating to safe working conditions, laboratory and manufacturing practices, the experimental use of animals, and the use and disposal of hazardous substances, including radioactive compounds and infectious disease agents, used in connection with our research work. If we fail to comply with the laws and regulations pertaining to our business, we may be subject to sanctions, including the temporary or permanent suspension of operations, product recalls, marketing restrictions, and civil and criminal penalties.

Our and our collaborators’ product candidates will remain subject to ongoing regulatory review even if they receive marketing approval. If we or our collaborators fail to comply with regulations applicable to approved products, these approvals could be lost and the sale of our or our collaborators’ products could be suspended.

Even if we or our collaborators receive regulatory approval to market a particular product candidate, the approval could be conditioned on us or our collaborators conducting costly post-approval studies or could limit the indicated uses included in product labeling. Moreover, the product may later cause adverse effects that limit or prevent its widespread use, force us or our collaborators to withdraw it from the market, or impede or delay our or our collaborators’ ability to obtain regulatory approvals in additional countries. In addition, the manufacturer of the product and its facilities will continue to be subject to regulatory review and periodic inspections to ensure adherence to applicable regulations. After receiving marketing approval, the manufacturing, labeling, packaging, adverse event reporting, storage, advertising, promotion, and record-keeping related to the product remain subject to extensive regulatory requirements. We do not have prior experience complying with regulations pertaining to products that have already received marketing approval and, therefore, we may be unable or slow to comply with existing regulations, including changes in existing regulatory requirements, or new regulations. Furthermore, our collaborators may be slow to adapt, or may never adapt, to changes in existing regulatory requirements or adoption of new regulatory requirements pertaining to products that have already received approval.

The FDA closely regulates the post-approval marketing and promotion of drugs and biologics to ensure they are marketed only for the approved indications and in accordance with the provisions of the approved labeling. If we market our products outside of their approved indications, we may be subject to enforcement action for off-label promotion. Violations of the FDA’s restrictions relating to the promotion of prescription drugs may also lead to investigations alleging violations of federal and state health care fraud and abuse laws, as well as state consumer protection laws.

If we or our collaborators fail to comply with the regulatory requirements of the FDA and other applicable U.S. and foreign regulatory authorities, or if previously unknown problems with our or our partners’ products, manufacturers, or manufacturing processes are discovered, we could be subject to administrative or judicially imposed sanctions, including:

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Any one of these could have a material adverse effect on our business or financial condition.

The FDA, EMA, or comparable foreign regulatory authorities could require the clearance or approval of a companion diagnostic device as a condition of approval for our product candidates, which would require substantial financial resources and could delay regulatory approval.

The FDA has indicated that approval of a companion diagnostic device may be necessary for some of our product candidates, including mirvetuximab. We may face significant delays or obstacles in obtaining approval of our product candidates as the FDA may take the position that a companion diagnostic device is required prior to granting approval of the marketing application. In addition, we may be dependent on the sustained cooperation and effort of third-party collaborators with whom we may partner in the future to develop companion diagnostics. We and our current, potential, and future collaborators may encounter difficulties in developing such tests, including issues relating to the selectivity and/or specificity of the diagnostic, analytical validation, reproducibility, or clinical validation, or in obtaining regulatory clearance or approval for such companion diagnostic. For example, the FDA has indicated that a companion diagnostic will be required for mirvetuximab and we have partnered with Ventana Medical Systems to develop the FRα companion diagnostic. The PMA for the companion diagnostic will be submitted concurrently with the BLA for mirvetuximab to allow for contemporaneous FDA review of the BLA and PMA. Any delay or failure by us or our potential and future collaborators to develop or obtain regulatory clearance or approval of such companion diagnostics, if necessary, could delay or prevent approval of our product candidates.

Unfavorable pricing regulations, third-party reimbursement practices, or healthcare reform initiatives applicable to our product candidates could limit our potential product revenue.

Regulations governing drug pricing and reimbursement vary widely from country to country. Some countries require approval of the sales price of a drug before it can be marketed. Some countries restrict the physicians that can authorize the use of more expensive medications. Some countries establish treatment guidelines to help limit the use of more expensive therapeutics and the pool of patients that receive them. In some countries, including the United States, third-party payers frequently seek discounts from list prices and are increasingly challenging the prices charged for medical products. Because our product candidates are in the development stage, we do not know the level of reimbursement, if any, we will receive for any products that we are able to successfully develop. If the reimbursement for any of our product candidates is inadequate in light of our development and other costs, our ability to achieve profitability would be affected. See “Regulatory Matters – Reimbursement”.

In the U.S., federal and state governments continue to propose and pass legislation designed to reform delivery of, or payment for, health care, which include initiatives to reduce the cost of healthcare generally and drugs specifically. For example, in March 2010, the U.S. Congress enacted the Patient Protection and Affordable Care Act and the Health Care and Education Reconciliation Act (the “ACA”), which expanded health care coverage through Medicaid expansion and the implementation of the individual mandate for health insurance coverage and which included changes to the coverage and reimbursement of drug products under government healthcare programs. Since its enactment, there have been and likely will be judicial, administrative, executive, and legislative challenges to certain aspects of the ACA. For example, tax reform legislation was enacted at the end of 2017 that eliminates the tax penalty for individuals who do not maintain sufficient health insurance coverage beginning in 2019 (the so-called “individual mandate”). More recently, on June 17, 2021, the U.S. Supreme Court dismissed the latest judicial challenge to the ACA brought by several states

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without specifically ruling on the constitutionality of the ACA. Changes resulting from any successful challenges or other future modifications may have a material impact on our business.

Beyond the ACA, there are ongoing and widespread federal and state health care reform efforts, a number of which have focused on regulation of prices or payment for drug products, including legislation on drug importation and legislation and regulation revising the Medicaid drug rebate program. Recent state legislative efforts to address drug costs have generally focused on increasing transparency around drug costs or limiting drug prices.

Healthcare reform efforts have been and may continue to be subject to scrutiny and legal challenge. For example, courts temporarily enjoined regulations that would implement a new “most favored nation” payment model for select drugs covered under Medicare Part B that was to take effect on January 1, 2021 and would limit payment based on international drug price and CMS subsequently issued a notice of proposed rulemaking to rescind and remove the regulations. As another example, revisions to regulations under the federal anti-kickback statute would remove protection for traditional Medicare Part D discounts offered by pharmaceutical manufacturers to pharmacy benefit managers and health plans. Pursuant to court order, the removal was delayed, and recent legislation imposed a moratorium on implementation of the rule until January 1, 2026.

Health care reform at the federal or state level could affect demand for, or pricing of, our product candidates if approved for sale. We cannot, however, predict the ultimate content, timing, or effect of any federal and state reform efforts. There is no assurance that federal or state health care reform will not adversely affect our future business and financial results.

As our business grows, we will become increasingly subject to additional healthcare regulation and enforcement by various government entities, and our failure to strictly adhere to these regulatory regimes could have a detrimental impact on our business.

In the United States, pharmaceutical manufacturers and their products are subject to extensive regulation at the federal and state level, including laws intended to prevent fraud and abuse in the healthcare industry. These laws, some of which will apply only if and when we have an approved product, include:

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Ensuring compliance is time-consuming and costly. Given the breadth of the laws and regulations, limited guidance for certain laws and regulations, and evolving government interpretations of the laws and regulations, governmental authorities may possibly conclude that our business practices are non- compliant. If our operations are found to be in violation of any of the laws described above or any other government regulations that apply to us, we may be subject to penalties, including civil and criminal penalties, damages, fines, exclusion from participation in government health care programs, such as Medicare and Medicaid, imprisonment, and the curtailment or restructuring of our operations, any of which could adversely affect our business, financial condition, results of operations, and prospects.

If we fail to comply with environmental, health, and safety laws and regulations that apply to us, we could become subject to fines or penalties or incur costs that could harm our business.

We are subject to numerous federal, state, and local environmental, health, and safety laws and regulations, including those governing the manufacture and transportation of hazardous materials and pharmaceutical compounds. Although we believe that our contracted research, development, and manufacturer safety procedures for handling and disposing of these materials comply with the standards prescribed by applicable laws and regulations, we cannot completely eliminate the risk of accidental contamination or injury from these materials. In the event of such an accident, we could be held liable for any resulting damages, and any liability could exceed our resources. We may be required to incur significant costs to comply with these laws in the future, including civil or criminal fines and penalties, which we may not be able to afford.

In addition, we may incur substantial costs in order to comply with current or future environmental, health, and safety laws and regulations applicable to us. These current or future laws and regulations may impair our research, development, or production efforts or impact the research activities we pursue, particularly with respect to research involving human subjects or animal testing. Our failure to comply with these laws and regulations also may result in substantial fines, penalties, or other sanctions, which could cause our financial condition to suffer.

Failure to comply with the Foreign Corrupt Practices Act and other similar anti-corruption laws and anti-money laundering laws, as well as export control laws, customs laws, sanctions laws, and other laws governing our operations could subject us to significant penalties and damage our reputation.

We are subject to the Foreign Corrupt Practices Act (FCPA), which generally prohibits U.S. companies and intermediaries acting on their behalf from offering or making corrupt payments to “foreign officials” for the purpose of obtaining or retaining business or securing an improper business advantage. The FCPA also requires companies whose securities are publicly listed in the United States to maintain accurate books and records and to maintain adequate internal accounting controls. We are also subject to other similar anti-corruption laws and anti-money laundering laws, as well as export control laws, customs laws, sanctions laws, and other laws that apply to our activities in the countries where we operate. Certain of the jurisdictions in which we conduct or expect to conduct business have heightened risks for public corruption, extortion, bribery, pay-offs, theft, and other fraudulent practices. In many countries, health care professionals who serve as investigators in our clinical studies or may prescribe or purchase any of our product candidates if they are approved, are employed by a government or an entity owned or controlled by a government. Dealings with these investigators, prescribers, and purchasers are subject to regulation under the FCPA. Under these laws and regulations, as well as other anti-corruption laws, anti-money-laundering laws, export control laws, customs laws, sanctions laws, and other laws governing our operations, various government agencies may require export licenses, may seek to impose modifications to business practices, including cessation of business activities in sanctioned countries or with sanctioned persons or entities and modifications to compliance programs, which may increase compliance costs, and may subject us to fines, penalties, and other sanctions.

Inadequate funding for the FDA, the Securities and Exchange Commission, and other government agencies could hinder their ability to hire and retain key leadership and other personnel, prevent new products and services from being developed or commercialized in a timely manner, or otherwise prevent those agencies from performing normal business functions, which could negatively affect our business.

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The ability of the FDA to review and approve new products can be affected by a variety of factors, including government budget and funding levels, ability to hire and retain key personnel and accept the payment of user fees, and statutory, regulatory, and policy changes. Average review times at the agency have fluctuated in recent years as a result. In addition, government funding of the U.S. Securities and Exchange Commission (SEC) and other government agencies on which our operations may rely, including those that fund research and development activities is subject to the political process, which is inherently fluid and unpredictable.

Disruptions at the FDA and other agencies may also slow the time required for new drugs to be reviewed and/or approved by necessary government agencies, which would adversely affect our business. For example, the U.S. government has shut down several times, including December 22, 2018 to January 25, 2019, and certain regulatory agencies, such as the FDA and the SEC, have had to furlough employees and stop critical activities. If a prolonged government shutdown or a series of shutdowns occurs, it could significantly affect the ability of the FDA to timely review and process our regulatory submissions, which could have a material adverse effect on our business. Further, future government shutdowns could impact our ability to gain access to the public markets and obtain necessary capital in order to properly capitalize and continue our operations.

We may be subject to, or may in the future become subject to, U.S. federal and state and foreign laws and regulations imposing obligations on how we collect, use, disclose, store, and process personal information. Our actual or perceived failure to comply with such obligations could result in liability or reputational harm and adversely affect our business. Ensuring compliance with such laws could also impair our efforts to maintain and expand our customer base, and thereby decrease our revenue.

In many activities, including the conduct of clinical trials, we are subject to laws and regulations governing data privacy and the protection of health-related and other personal information. These laws and regulations govern our processing of personal data, including the collection, access, use, analysis, modification, storage, transfer, destruction, and disposal of personal data. They also impose requirements with respect to notification and remediation of security breaches involving personal data. We must comply with laws and regulations associated with the international transfer of personal data based on the location in which the personal data originates and the location in which such data are processed. While we strive to comply with all applicable privacy and security laws and regulations, legal standards for privacy continue to evolve and any failure or perceived failure to comply may result in proceedings or actions against us by government entities or others, or could cause reputational harm, which could have a material adverse effect on our business.

The legislative and regulatory landscape for privacy and data security continues to evolve. For example, the EU General Data Protection Regulation (GDPR), which was effective as of May 25, 2018, introduced new data protection requirements in the European Union relating to the consent of the individuals to whom the personal data relate, the information provided to the individuals, the documentation we must retain, the security and confidentiality of the personal data, data breach notification, and the use of third party processors in connection with the processing of personal data. The GDPR has increased our responsibility and potential liability in relation to personal data that we process, and we may be required to put in place additional mechanisms to ensure compliance with the GDPR. However, our ongoing efforts related to compliance with the GDPR may not be successful and could increase our cost of doing business. In addition, data protection authorities of the different EU member states may interpret the GDPR differently, and guidance on implementation and compliance practices are often updated or otherwise revised, which adds to the complexity of processing personal data in the European Union.

In the United States, California adopted the California Consumer Privacy Act of 2018 (CCPA), which became effective in January 2020. The CCPA has been characterized as the first “GDPR-like” privacy statute to be enacted in the United States because it mirrors a number of the key provisions of the EU GDPR. The CCPA establishes a new privacy framework for covered businesses by creating an expanded definition of personal information, establishing new data privacy rights for consumers in the State of California, imposing special rules on the collection of consumer data from minors, and creating a new and potentially severe statutory damages framework for violations of the CCPA and for businesses that fail to implement reasonable security procedures and practices to prevent data breaches. The California Privacy Rights Act will impose additional obligations on companies processing personal information of California residents beyond those found in the CCPA when it takes effect in January 2023.

We expect to be subject to additional privacy laws at both the U.S. state level and abroad as many jurisdictions worldwide in addition to those examples discussed above have either recently passed data privacy legislation or are considering enacting such legislation.

Risks Related to Our Key Personnel and Other Service Providers

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We depend on our key personnel, and we must continue to attract and retain key employees and consultants.

We depend on our key scientific and management personnel. Our ability to pursue the development of our current and future product candidates depends largely on retaining the services of our existing personnel and hiring additional qualified scientific personnel to perform research and development. Although we have entered into employment agreements with our executive officers, each of them may terminate their employment with us at any time. We do not maintain “key person” insurance for any of our executives or other employees. In addition, we rely on consultants and advisors, including scientific and clinical advisors, to assist us in formulating our research and development and commercialization strategy. Our consultants and advisors may be employed by employers other than us and may have commitments under consulting or advisory contracts with other entities that may limit their availability to us. If we are unable to continue to attract and retain high-quality personnel, our ability to pursue our growth strategy will be limited. We will also need to hire personnel with expertise in clinical testing, government regulation, manufacturing, sales, marketing, distribution, and finance. Attracting and retaining qualified personnel will be critical to our success. We may not be able to attract and retain personnel, or, in the event key personnel leave, suitable replacements for such personnel, on acceptable terms given the competition for such personnel among biotechnology, pharmaceutical, and healthcare companies, universities, and non-profit research institutions. Failure to retain our existing key management and scientific personnel or to attract additional highly qualified personnel could delay the development of our product candidates and harm our business.

Our employees, independent contractors, principal investigators, CROs, consultants, and collaborators may engage in misconduct or other improper activities, including noncompliance with regulatory standards and requirements and insider trading.

We are exposed to the risk that our employees, independent contractors, principal investigators, third-party contract research organizations (CROs), consultants, and collaborators may engage in fraudulent conduct or other illegal activity. Misconduct by these parties could include intentional, reckless and/or negligent conduct or unauthorized activities that violate: (1) laws or regulations in jurisdictions where we are performing activities in relation to our product candidates, including those laws requiring the reporting of true, complete, and accurate information to such authorities; (2) manufacturing regulations and standards; (3) applicable laws prohibiting the promotion of a medical product for a use that has not been cleared or approved; (4) fraud and abuse, anti-corruption, and anti-money laundering laws, as well as similar laws and regulations and other laws; or (5) laws that require the reporting of true and accurate financial information and data. In particular, sales, marketing, and business arrangements in the healthcare industry are subject to laws intended to prevent fraud, bias, misconduct, kickbacks, self-dealing, and other abusive practices, and these laws may differ substantially from country to country. Misconduct by these parties could also include the improper use of information obtained in the course of clinical trials or performing other services, which could result in investigations, sanctions, and serious harm to their or our reputation. It is not always possible to identify and deter misconduct by these parties, and the precautions and procedures we currently take or may establish in the future as our operations and employee, CRO, consultant, and collaborator base expands to detect and prevent this type of activity may not be effective in controlling unknown or unmanaged risks or losses or in protecting us from governmental investigations or other actions or lawsuits stemming from a failure by these parties to comply with such laws or regulations. If any such actions are instituted against us, and we are not successful in defending ourselves or asserting our rights, those actions could have a significant impact on our business and results of operations, including the imposition of significant fines or other sanctions. In addition, we have limited experience with respect to laws governing the commercial sale of pharmaceutical products. We will need to implement measures to maintain compliance with these laws if any of our product candidates are approved. The failure to adequately implement and maintain these measures could negatively affect our sales and marketing activities and our business.

Risks Related to Our Technology Systems

Our business and operations could suffer in the event of system failures.

We utilize information technology systems and networks to process, transmit, and store electronic information in connection with our business activities. As use of digital technologies has increased, cyber incidents, including deliberate attacks and attempts to gain unauthorized access to computer systems and networks, have increased in frequency and sophistication. These threats pose a risk to the security of our systems and networks and the confidentiality, availability, and integrity of our data. There can be no assurance that we will be successful in preventing cyber-attacks or successfully mitigating their effects.

Despite the implementation of security measures, our internal computer systems, and those of our CROs and other contractors and consultants, are vulnerable to damage from cyber-attack, computer viruses, unauthorized access, natural disasters, terrorism, war, and telecommunication and electrical failures. Furthermore, we have little or no control

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over the security measures and computer systems of our third-party CROs and other contractors and consultants. While we have not experienced any such system failure, accident, or security breach to date, if such an event were to occur and cause interruptions in our operations, it could result in a material disruption of our programs. For example, the loss of clinical trial data for our product candidates could result in delays in our marketing approval efforts and significantly increase our costs to recover or reproduce the data. To the extent that any disruption or security breach results in a loss of or damage to our data or applications or other data or applications relating to our technology or product candidates, or inappropriate disclosure of confidential or proprietary information, we could incur liabilities and the further development of our product candidates could be delayed.

Risks Related to the Ownership of Our Common Stock

Our stock price may be volatile and fluctuate significantly and results announced by us and our collaborators or competitors could cause our stock price to decline.

Our stock price could fluctuate significantly due to the risks listed in this section, business developments announced by us and by our collaborators and competitors, or as a result of market trends and daily trading volume. The business developments that could affect our stock price include disclosures related to clinical findings with compounds that make use of our ADC technology, new collaborations, clinical advancement, or discontinuation of product candidates that make use of our ADC technology or product candidates that compete with our compounds or those of our collaborators, and regulatory approvals for our product candidates, if any, or product candidates that compete with our compounds or those of our collaborators. Our stock price could also fluctuate significantly with the level of overall investment interest in small-cap biotechnology stocks or for other reasons unrelated to our business.

Our operating results have fluctuated in the past and are likely to continue to do so in the future. Our revenue is unpredictable and may fluctuate due to the timing of non-recurring licensing fees, decisions of our collaborators with respect to our agreements with them, and the achievement of milestones and our receipt of the related milestone payments under new and existing licensing and collaboration agreements. Revenue historically recognized under our prior collaboration agreements may not be an indicator of revenue from any future collaboration. In addition, our expenses are unpredictable and may fluctuate from quarter to quarter due to the timing of expenses, which may include obligations to manufacture or supply product or payments owed by us under licensing or collaboration agreements. It is possible that our quarterly and/or annual operating results will not meet the expectations of securities analysts or investors, causing the market price of our common stock to decline. We believe that quarter-to-quarter and year-to-year comparisons of our operating results are not good indicators of our future performance and should not be relied upon to predict the future performance of our stock price.

The potential sale of additional shares of our common stock may cause our stock price to decline.

We may seek additional capital due to market conditions or strategic considerations even if we believe we have sufficient funds for our current or future operating plans through a variety of means, including through private and public equity offerings and debt financings. To the extent that we raise additional capital through the sale of equity or convertible debt securities, ownership interest of existing shareholders will be diluted, and the price of our stock may decline. The price of our common stock may also decline if the market expects us to raise additional capital through the sale of equity or convertible debt securities whether or not we actually plan to do so.

We do not intend to declare or pay cash dividends on our common stock in the foreseeable future.

We have not declared or paid cash dividends on our common stock since our inception and do not intend to declare or pay cash dividends in the foreseeable future. We currently intend to retain all of our future earnings, if any, to finance the growth and development of our business. Therefore, shareholders will have to rely solely on appreciation in our stock price, if any, in order to achieve a gain on an investment.

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combination and expect to initiate expansion cohorts in relapsed and frontline patients this year.

In addition, we are advancing our earlier-stage pipeline programs. IMGC936 is an ADC in co-development with MacroGenics, Inc. that is designed to target ADAM9, an enzyme over-expressed in a range of solid tumors and implicated in tumor progression and metastasis. IMGC936 incorporates a number of innovations, including antibody engineering to extend half-life, site-specific conjugation with a fixed drug-antibody ratio to enable higher dosing, and a next-generation linker and payload designed for improved stability and bystander activity. We continue to enroll patients in the Phase 1 study for this program and expect initial data in 2022.

IMGN151 is our next generation anti-FRα product candidate in preclinical development. This ADC integrates innovation in each of its components, which we believe may enable IMGN151 to address patient populations with lower levels of FRα expression, including tumor types outside of ovarian cancer. In January 2022, we submitted an IND application to evaluate IMGN151 in a planned Phase 1 clinical trial in patients with recurrent endometrial cancer and recurrent, high-grade serous epithelial ovarian, primary peritoneal, or fallopian tube cancers. In February 2022, the FDA placed a clinical hold on our IND application pending the resolution of certain chemistry, manufacturing, and controls, or CMC, information requests. We are generating data responsive to the requests and anticipate filing these responses mid-year, which we believe will enable us to proceed with the study in due course thereafter.

We have selectively licensed restricted access to our ADC platform technology to other companies to expand the use of our technology and to provide us with cash to fund our own product programs. These agreements typically provide the licensee with rights to use our ADC platform technology with its antibodies or related targeting vehicles to a defined target to develop products. The licensee is generally responsible for the development, clinical testing, manufacturing, registration, and commercialization of any resulting product candidate. As part of these agreements, we are generally entitled to receive upfront fees, potential milestone payments, and royalties on the sales of any resulting products. For more information concerning these relationships, including their ongoing financial and accounting impact on our business, please read Note C, “Significant Collaborative Agreements,” to our consolidated financial statements included in this report.

To date, we have not generated revenues from commercial sales of internal products, and we expect to continue to incur substantial operating losses for at least the near term as we incur significant operating expenses related to research and development and the potential commercialization of our portfolio. As of December 31, 2021, we had $478.8 million in cash and cash equivalents compared to $293.9 million as of December 31, 2020.

Critical Accounting Policies and Estimates

We prepare our consolidated financial statements in accordance with accounting principles generally accepted in the U.S. The preparation of these financial statements requires us to make certain estimates and judgments that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the consolidated financial statements, and the reported amounts of revenues and expenses during the reported periods. These items are monitored and analyzed by management for changes in facts and circumstances, and material changes in these estimates could occur in the future. Changes in estimates are reflected in reported results for the period in which the change occurs. We base our estimates on historical experience and various other assumptions that we believe to be reasonable under the circumstances. Actual results may differ from our estimates if past experience or other assumptions do not turn out to be substantially accurate.

We believe that our application of the following accounting policies, each of which requires significant judgments and estimates on the part of management, are the most critical to aid in fully understanding and evaluating our reported financial results:

Our accounting policies are more fully described in the Notes to our consolidated financial statements, including Note B, “Summary of Significant Accounting Policies,” included in this Annual Report on Form 10-K.

Managing the Impact of the COVID-19 Pandemic

Since the first quarter of 2020, we have continued to move our clinical studies forward while adapting to meet the evolving challenges of the COVID-19 pandemic. We implemented business continuity plans in March 2020 that enabled our workforce to remain productive while working from home until mid-September 2021, at which time our workforce returned to the office. From a manufacturing and supply chain perspective, we believe we have sufficient

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inventory on hand for all of our ongoing and near-term studies and to support the launch of mirvetuximab, if approved. From a regulatory perspective, since the beginning of the pandemic, we have received timely reviews of our submissions to the FDA and other health authorities covering our clinical trial applications.

The impact of COVID-19 slowed site activation and patient enrollment for both SORAYA and MIRASOL, which resulted in a limited delay in patient accrual for each of these studies.

Results of Operations

For a discussion related to the results of operations for 2020 compared to 2019, refer to Part II, Item 7, "Management's Discussion and Analysis of Financial Condition and Results of Operations – Results of Operations" in our Annual Report on Form 10–K for the year ended December 31, 2020 filed with the SEC on March 1, 2021.

Revenues

For 2021, our total revenues decreased to $69.9 million compared to $132.3 million for 2020, driven by decreases in license and milestone fees and non-cash royalty revenue, both of which are discussed further below.

License and milestone fees

The amount of license and milestone fees we earn is directly related to the number of our collaborators, the collaborators’ advancement of the product candidates, and the overall success in clinical trials of the product candidates. As such, the amount of license and milestone fees may vary widely from quarter to quarter and year to year. Total revenue recognized from license and milestone fees for the years ended 2021 and 2020 was $22.7 million and $63.7 million, respectively. In 2020, we recognized $60.5 million of previously deferred license revenue upon Jazz’s opt-out of its right to the last remaining license under its collaboration and option agreement, which drove the decrease in license and milestone fee revenue in 2021 compared to 2020. Partially offsetting this decrease, we recorded $7.4 million of revenue related to partner milestones achieved in 2021 and, pursuant to our license agreement with Huadong executed in October 2020, upon delivery of initial clinical supply in 2021, we recorded $14.6 million of the $40.0 million upfront payment previously deferred.

Deferred revenue of $92.1 million as of December 31, 2021 includes $28.5 million related to the collaboration with Huadong and $57.6 million related to the sale of our residual rights to receive royalty payments on commercial sales of KADCYLA in 2019, with the remainder of the balance primarily representing consideration received from our other collaborators pursuant to our license agreements that we have yet to earn pursuant to our revenue recognition policy.

Non-cash royalty revenue related to the sale of future royalties

KADCYLA is a marketed ADC resulting from one of our development and commercialization licenses with Roche, through its Genentech unit. We receive royalty reports and payments related to sales of KADCYLA from Roche one quarter in arrears. We sold our rights to receive royalty payments on the net sales of KADCYLA through two separate transactions in 2015 and 2019. In accordance with our revenue recognition policy, $46.8 million and $68.5 million of non-cash royalties on net sales of KADCYLA were recorded and included in royalty revenue for 2021 and 2020, respectively. The decrease in non-cash royalty revenue in 2021 compared to 2020 is a result of the aggregate royalty threshold, as outlined in the 2015 royalty purchase agreement, being met in the second quarter of 2021, effectively reducing the royalty payments under the 2015 transaction from 100% to 15% of KADCYLA royalty payments received over the remaining royalty term. Pursuant to the terms of these agreements, we expect to recognize less non-cash royalty revenue in 2022 and subsequent years as compared to 2021 and prior years. See further details regarding these agreements in Note F, “Liability Related to Sale of Future Royalties,” of the Consolidated Financial Statements.

Research and Development Expenses

Our research and development expenses relate to (i) research to evaluate new targets and to develop and evaluate new antibodies, linkers, and cytotoxic agents, (ii) preclinical testing of our own and, in certain instances, our collaborators’ product candidates, and the cost of our own clinical trials, (iii) development related to clinical and commercial manufacturing processes, (iv) regulatory activities, and (v) external manufacturing operations.

Clinical trial and regulatory approval processes for our product candidates that have advanced or that we intend to advance to clinical testing are lengthy, expensive, and uncertain in both timing and outcome. As a result, the pace and timing of the clinical development of our product candidates is highly uncertain and may never result in approved products. Completion dates and development costs will vary significantly for each product candidate and are difficult to predict. A variety of factors, many of which are outside our control, could cause or contribute to the prevention or delay

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of the successful completion of our clinical trials, or delay or prevent our obtaining necessary regulatory approvals. The costs to take a product through clinical trials are dependent upon, among other factors, the clinical indications, the timing, size, and design of each clinical trial, the number of patients enrolled in each trial, and the speed at which patients are enrolled and treated. Product candidates may be found to be ineffective or to cause unacceptable side effects during clinical trials, may take longer to progress through clinical trials than anticipated, may fail to receive necessary regulatory approvals, or may prove impractical to manufacture in commercial quantities at reasonable cost or with acceptable quality.

The lengthy process of securing FDA approvals for new drugs requires the expenditure of substantial resources. Any failure by us to obtain, or any delay in obtaining, regulatory approvals, could materially adversely affect our product development efforts and our business overall. Accordingly, we cannot currently estimate, with any degree of certainty, the amount of time or money that we will be required to expend in the future on our product candidates prior to their regulatory approval, if such approval is ever granted.

Research and development expense was $151.1 million and $114.6 million for 2021 and 2020, respectively, with increased expenses related to personnel, third-party staffing costs, contract services, external manufacturing costs, and clinical trial costs, which are discussed further below.

We do not track our research and development costs by project. Since we use our research and development resources across multiple research and development projects, we manage our research and development expenses within each of the categories listed in the following table and described in more detail below (in thousands):

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Preclinical and clinical testing

Preclinical and clinical testing includes expenses related to preclinical testing of our own, and, in certain instances, our collaborators’ product candidates, regulatory activities, and the cost of clinical trials. Such expenses include those related to personnel, third-party staffing, patient enrollment at our clinical testing sites, consultant fees, contract services, and facilities. Preclinical and clinical testing expenses increased to $100.0 million for 2021 compared to $75.4 million for 2020. This increase is primarily the result of increased clinical trial, personnel, and third-party staffing costs related to advancing the MIRASOL, SORAYA, PICCOLO, and IMGC936 studies and increased third-party service fees in support of commercial readiness.

Process and product development

Process and product development expenses include costs for development of clinical and commercial manufacturing processes for our own and collaborator compounds. Such expenses include the costs of personnel, third-party staffing, contract services, and facility expenses. Process and product development expenses increased to $7.0 million for 2021 compared to $5.4 million for 2020, due primarily to increased personnel and third-party staffing costs.

Manufacturing operations

Manufacturing operations expense includes costs to have preclinical and clinical materials manufactured for our product candidates and quality control and quality assurance activities. Such expenses include personnel, third-party staffing, raw materials for our preclinical studies and clinical trials, non-pivotal and pivotal development costs with contract manufacturing organizations, and facility expenses. Manufacturing operations expense increased $10.4 million to $44.1 million for 2021 compared to 2020. The increase in 2021 is principally due to increases in external manufacturing activity across our programs, and to a lesser extent, increases in personnel and third-party staffing costs.

Manufacturing operations expense also includes antibody development and supply expense in support of commercial validation and in anticipation of potential future clinical trials, as well as our ongoing trials, was $20.6 million and $20.2 million for 2021 and 2020, respectively. The process of antibody production is lengthy due in part to the lead time to establish a satisfactory production process at a vendor. Accordingly, costs incurred related to antibody production and development have fluctuated from period to period and we expect these cost fluctuations to continue in the future.

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General and Administrative Expenses

General and administrative expenses increased $5.2 million to $43.8 million for 2021 due primarily to increases in professional services and personnel expenses, including $2.0 million of greater stock-based compensation driven largely by expense recorded in 2021 related to certain performance stock options becoming probable of vesting.

Restructuring Charges

During 2020, we recorded $1.5 million of restructuring charges, primarily incremental retention benefits, related to the restructuring of the business in 2019. No similar expense was recorded in 2021.

Investment Income, net

Investment income for 2021 and 2020 was $0.1 million and $0.7 million, respectively. The decrease in 2021 was driven by a decrease in interest rates.

Non-Cash Interest Expense on Liability Related to Sale of Future Royalty

In 2015, IRH purchased our right to receive 100% of the royalty payments on commercial sales of KADCYLA arising under our development and commercialization license with Genentech, subject to a residual cap. In January 2019, OMERS purchased IRH’s right to the royalties the Company previously sold in 2015. As described in Note F, “Liability Related to Sale of Future Royalties,” to our Consolidated Financial Statements, this royalty sale transaction has been recorded as a liability that amortizes over the estimated royalty payment period as KADCYLA royalties are remitted directly to the purchaser. During 2021 and 2020, we recorded $13.1 million and $23.1 million, respectively, of non-cash interest expense, which includes amortization of deferred financing costs. The decrease in 2021 was a result of a lower average royalty liability balance for the year and the KADCYLA royalty threshold being met in the second quarter of 2021, effectively reducing the royalty payments under the 2015 transaction from 100% to 15% of KADCYLA royalty payments received over the remaining royalty term.

We record interest expense at the imputed interest rate, which we currently estimate to be 19.5%. There are a number of factors that could materially affect the estimated interest rate in the future, in particular, the estimated amount and timing of royalty payments from future net sales of KADCYLA. We assess this estimate on a periodic basis and any resulting change in interest rate will be adjusted prospectively.

Other (Expense) Income, net

Other (expense) income, net for 2021 and 2020 was $(1.1) million and $0.5 million, respectively, consisting of foreign currency exchange (losses) gains related to obligations with non-U.S. dollar-based suppliers and Euro cash balances maintained to fulfill them during the respective periods.

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Cash Flows

We require cash to fund our operating expenses, including the advancement of our clinical programs, and to make capital expenditures. Historically, we have funded our cash requirements primarily through equity and convertible debt financings in private and public markets and payments from our collaborators, including license fees, milestones, research funding, and royalties. We also monetized our rights to receive royalties on KADCYLA for upfront consideration. As of December 31, 2021, we had $478.8 million in cash and cash equivalents. Net cash used for operating activities was $169.4 million and $78.6 million during 2021 and 2020, respectively. The principal use of cash in operating activities for these periods was to fund our net loss, adjusted for non-cash items, with 2020 benefiting from a $40.0 million upfront payment from Huadong pursuant to a collaboration and license agreement.

Net cash (used for) provided by investing activities was $(1.4) million and $0.5 million for 2021 and 2020, respectively, and represent cash outflows from capital expenditures, net of proceeds generated from the sale of capital assets. Capital expenditures for all periods presented consisted primarily of furniture and improvements related to COVID-19 safety measures, computer and office equipment, and dedicated equipment at third-party manufacturing vendors. During 2020, as a result of our restructuring of the business in 2019, we sold excess equipment generating proceeds of $1.5 million.

Net cash provided by financing activities was $355.7 million and $195.7 million for 2021 and 2020, respectively. In December 2021, pursuant to a public offering, we issued and sold 17.5 million shares of common stock and issued pre-funded warrants to purchase 27.4 million shares of common stock, resulting in aggregate net proceeds of $277.6 million. In August 2021, pursuant to a Securities Purchase Agreement with RA Capital Healthcare Fund, L.P., we issued a pre-funded warrant to purchase up to approximately 5.4 million shares of common stock, resulting in net proceeds of $29.8 million. Additionally, during 2021, we sold 6.7 million shares of our common stock under our Open Market Sale Agreement^SM (Sale Agreement) with Jefferies, LLC as sales agent, dated December 18, 2020, generating net proceeds of $45.8 million. Pursuant to the Sale Agreement, we may offer and sell, from time to time, shares of our common stock having an aggregate offering price of up to $150.0 million. As of December 31, 2021, $102.7 million remains available under the Sale Agreement. In connection with entering into the Sale Agreement, we filed a prospectus supplement to the prospectus included in our registration statement on Form S-3 (No. 333-251502), which became effective upon filing on December 18, 2020, with the SEC relating to the offer and sale of the up to $150.0 million of our common stock under the Sale Agreement.

In January 2020, pursuant to a public offering, we issued and sold 24.5 million shares of common stock, resulting in net proceeds of $97.7 million. Additionally in September 2020, we entered into an Open Market Sale Agreement^SM with Jefferies, LLC as sales agent, pursuant to which we could offer and sell, from time to time, shares of our common stock in 2020 having an aggregate offering price of up to $100.0 million. Under the September Sale Agreement, we offered and sold approximately 20.0 million shares of our common stock resulting in net proceeds of $96.5 million.

Net cash provided by financing activities for 2021 and 2020 also include proceeds from the exercise of stock options and sale of shares through our ESPP.

Future Capital Requirements

We have significant future capital requirements including:

We anticipate that our current capital resources will enable us to meet our operational expenses and capital requirements for more than twelve months after the date of this report. We may raise additional funds through equity, debt, and other financings or generate revenues from collaborators through a combination of upfront license payments,

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milestone payments, royalty payments, and research funding. We cannot provide assurance that we will be able to obtain additional debt, equity, or other financing or generate revenues from collaborators on terms acceptable to us or at all. Should we or our partners not meet some or all of the terms and conditions of our various collaboration agreements or if we are not successful in securing future collaboration agreements, we may elect or be required to secure alternative financing arrangements, and/or defer or limit some or all of our research, development, and/or clinical projects.

Recent Accounting Pronouncements

The information set forth under Note B to the consolidated financial statements under the caption “Recently Adopted Accounting Pronouncements” is incorporated herein by reference.

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/s/ Ernst & Young LLP

We have served as the Company’s auditor since 2001.

Boston, Massachusetts

February 28, 2022  

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The accompanying notes are an integral part of the consolidated financial statements.

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