RISK FACTORS

Investing in our common stock includes a high degree of risk. You should consider carefully the risks described below, together with the other information contained in this prospectus, including our financial statements and the related notes, before investing in our common stock. If any of the following risks actually occurs, our business, financial condition, results of operations and future prospects would likely be materially and adversely affected. This could cause the market price of our common stock to decline and could cause you to lose all or part of your investment.

Risks Related to our Business

We are heavily dependent on the success of CEM-101 and Taksta, which are still under clinical development. The FDA and foreign regulatory approval process is lengthy, time consuming and inherently unpredictable and if we are ultimately unable to obtain regulatory approval for CEM-101 or Taksta our business will be substantially harmed.

We have no products that have been approved for sale. Our near-term prospects are substantially dependent on our ability to develop and commercialize CEM-101 and Taksta. We cannot commercialize, market or sell either product in the U.S. without FDA approval. FDA approval, if received, is several years away at least. To commercialize CEM-101 outside of the U.S., we would need applicable foreign regulatory approval. The clinical development of CEM-101 and Taksta is susceptible to the risk of failure inherent in any stage of drug development, including failure to achieve efficacy across a broad population of patients, the occurrence of severe adverse events and the FDA or any applicable foreign regulatory authority determining that a drug product is not approvable.

The process required to obtain approval for commercialization from the FDA and similar foreign authorities is unpredictable, and typically takes many years following the commencement of clinical trials depending on numerous factors. In addition, approval policies, regulations, or the type and amount of clinical data necessary to obtain regulatory approval may change during the course of a product’s clinical development. We may fail to obtain regulatory approval for CEM-101, Taksta or any other product candidates for many reasons, including the following:

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This lengthy approval process as well as the unpredictability of future clinical trial results may prevent us from obtaining regulatory approval to market CEM-101, Taksta or any future product candidates, which would significantly harm our business, financial condition, results of operations and prospects.

Clinical trials involve a lengthy and expensive process with an uncertain outcome, and results of earlier studies and trials may not be predictive of future trial results.

Clinical testing is expensive, can take many years to complete and its outcome is highly uncertain. Failure can occur at any time during the clinical trial process due to inadequate performance of a drug or inadequate adherence by patients or investigators to clinical trial protocols. Pursuant to FDA guidelines, new drugs must show non-inferiority or superiority to existing approved treatments. We have conducted our CEM-101 and Taksta clinical trials pursuant to draft guidelines published by the FDA for drugs being developed for the treatment of CABP and ABSSSI, respectively. To date, our clinical trials demonstrate CEM-101 and Taksta are comparable to current standards of care. However, because the numbers of patients in our Phase 2 trial for the oral formulation of CEM-101 and our Phase 2 trial for Taksta were small, our results were not powered to show, and did not show, statistical non-inferiority. If in later clinical trials CEM-101 or Taksta fails to demonstrate superiority or non-inferiority according to FDA guidelines, the FDA will not approve that product candidate and we would not be able to commercialize it, which will have a material adverse effect on our business, financial condition, results of operations and prospects.

Our planned Phase 3 trials for CEM-101 may be more expensive and time consuming than we currently expect. FDA regulations require two Phase 3 trials for any drug for which an NDA is submitted. We believe that we will only need to conduct one Phase 3 trial for oral CEM-101 because of the overlapping nature of that trial and our two planned Phase 3 IV-to-oral trials, which should provide the necessary data to support our planned NDA and satisfy the FDA requirement. However, the FDA could insist that we conduct two Phase 3 trials for oral CEM-101, which would add to the time and cost of CEM-101’s development.

In addition, the results of pre-clinical studies and early clinical trials of product candidates may not be predictive of the results of later-stage clinical trials. A number of companies in the pharmaceutical and biotechnology industries, including those with greater resources and experience than us, have suffered significant setbacks in Phase 2 and Phase 3 clinical trials despite achieving successful results in earlier stage trials. The failure to obtain positive results in any of our Phase 2 or Phase 3 clinical trials could seriously impair the development prospects, and even prevent regulatory approval, of CEM-101 or Taksta or any candidate in our existing proprietary macrolide library.

We have no experience as a company in bringing a drug to regulatory approval.

As a company, we have never obtained regulatory approval for, or commercialized, a drug. It is possible that the FDA may refuse to accept any or all of our planned NDAs for substantive review or may conclude after review of our data that our application is insufficient to obtain regulatory approval of CEM-101, Taksta or any future product candidates. If the FDA does not accept or approve any or all of our planned NDAs, it may require that we conduct additional clinical, pre-clinical or manufacturing validation studies, which may be costly, and submit that data before it will reconsider our applications. Depending on the extent of these or any other FDA required studies, approval of any NDA or application that we submit may be significantly delayed, possibly for several years, or may require us to expend more resources than we have available. Any delay in obtaining, or an inability to obtain, regulatory approvals would prevent us from commercializing CEM-101 or Taksta, generating revenues and achieving and sustaining profitability. It is also possible that additional studies, if performed and completed, may not be considered sufficient by the FDA to approve any NDA we submit. If any of these outcomes occur, we may be forced to abandon our planned NDAs for either CEM-101 or Taksta or both, which would materially adversely affect our business and could potentially cause us to cease operations. We face similar risks for any approval in a foreign jurisdiction.

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Future legislation, and/or regulations and policies adopted by the FDA or other regulatory health authorities may increase the time and cost required for us to conduct and complete clinical trials for CEM-101, Taksta or other product candidates that we develop.

The FDA has established regulations, guidelines and policies to govern the drug development and approval process, as have foreign regulatory authorities. Any change in regulatory requirements due to the adoption by the FDA and/or foreign regulatory authorities of new legislation, regulations, or policies may require us to amend existing clinical trial protocols or add new clinical trials to comply with these changes. Such amendments to existing protocols and/or clinical trial applications or the need for new ones, may significantly impact the cost, timing and completion of the clinical trials.

In particular, drugs being developed for the treatment of CABP and ABSSSI, including CEM-101 and Taksta, are subject to draft guidelines published by the FDA in March 2009 and August 2010, respectively. We have conducted our clinical trials to date according to the standards established by these draft guidelines, but we expect the FDA will revise these draft guidelines before we submit our NDAs for CEM-101 and Taksta. Any new draft guidelines may require us to conduct additional clinical trials, re-run previously completed trials to gather data at different endpoints or according to different protocols, or otherwise materially alter our planned clinical development of CEM-101 and Taksta. Any such regulatory change may materially increase our costs, delay the completion of our clinical trials, and otherwise impact our ability to obtain regulatory approval for our product candidates.

In addition, increased scrutiny by the U.S. Congress of the FDA’s approval process, particularly in our areas of focus, may significantly delay or prevent regulatory approval, as well as impose more stringent product labeling and post-marketing testing and other requirements.

We might not successfully differentiate CEM-101 from telithromycin (Ketek ^® ), a macrolide found to cause severe side effects.

Ketek is a macrolide antibiotic that the FDA approved in 2004 for the treatment of multi-drug resistant pneumococci and other CABP bacteria. Soon after release, however, Ketek was found to cause reversible visual disturbances, exacerbate myasthenia gravis (a neurological disorder characterized by improper muscle regulation) and cause liver failure. These effects led the FDA to require the drug label for Ketek to include a strengthened warning section regarding specific drug-related adverse events and contributed to Ketek being withdrawn in 2007 for the treatment of all infections other than CABP. Our research suggests these side effects are likely caused by pyridine, which is a component of Ketek. CEM-101 and older generation macrolides, including azithromycin and clarithromycin, do not have a pyridine component. If our research is proven to be incorrect or if CEM-101 demonstrates similar side effects, the FDA might not approve CEM-101, or, if already approved, might withdraw approval or require warnings on product labeling, which would significantly harm our ability to generate revenues from CEM-101. Even if the FDA approves CEM-101, physicians may not be convinced that CEM-101 is a safe and effective treatment for CABP and other infections. If physicians believe CEM-101 demonstrates characteristics similar to Ketek, they might not prescribe CEM-101, which would negatively affect our revenues.

Bacteria might develop resistance to CEM-101 or Taksta, which would decrease the efficacy and commercial viability of that product.

Drug resistance is primarily caused by the genetic mutation of bacteria resulting from sub-optimal exposure to antibiotics where the drug does not kill all of the bacteria. While antibiotics have been developed to treat many of the most common infections, the extent and duration of their use worldwide has resulted in new mutated strains of bacteria resistant to current treatments. We are developing CEM-101 and Taksta to treat patients infected with drug-resistant bacteria. With respect to CEM-101, which is a next generation macrolide, resistance issues associated with earlier generations of macrolides have led to a decrease in their use for treating serious respiratory tract infections such as CABP. If physicians, rightly or wrongly, associate the resistance issues of earlier generation macrolides with CEM-101, physicians might not prescribe CEM-101 for treating a broad range of infections. Similarly, resistance to fusidic acid has developed outside the U.S. Our in vitro studies have shown that the reason for resistance to the oral formulation is that it was not dosed optimally. We believe that overuse of topical formulations of fusidic acid also contributed to development of resistance outside the U.S. If Taksta is improperly dosed, or if our studies incorrectly

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attributed an increase in resistance to inappropriate dosing, bacteria might develop resistance to Taksta in the U.S. If these bacteria develop resistance to CEM-101 or Taksta, the efficacy of these products would decline, which would negatively affect our potential to generate revenues from these products.

Delays in clinical trials are common and have many causes, and any such delays could result in increased costs to us and jeopardize or delay our ability to obtain regulatory approval and commence product sales as currently contemplated.

We may experience delays in clinical trials of our product candidates. Our planned clinical trials might not begin on time, might need to be redesigned, might not enroll a sufficient number of patients or might not be completed on schedule, if at all. Clinical trials can be delayed for a variety of reasons, including the following:

We were subject to such a delay in 2008 when the FDA placed a partial clinical hold on our Phase 2 clinical trial for oral CEM-101 over concern about possible toxicity related to CEM-101. At the time, the FDA had concerns that CEM-101, as a fluoroketolide, may have similar toxicity issues as Ketek. While we addressed the FDA’s concerns and were allowed to proceed with the trial, which we recently completed, the trial was delayed by approximately 12 months.

Patient enrollment, a significant factor in the timing of clinical trials, is affected by many factors, including the size and nature of the patient population, the proximity of patients to clinical sites, the eligibility criteria for the trial, the design of the clinical trial, competing clinical trials and clinicians’ and patients’ perceptions as to the potential advantages of the drug being studied in relation to other available therapies, including any new drugs that may be approved for the indications we are investigating. In addition, the timing of our clinical trials for CEM-101 is dependent on the onset, degree and timing of the CABP season, which tends to occur in the winter months in each hemisphere. We could encounter delays in our clinical trials of CEM-101 or Taksta if participating physician investigators encounter unresolved ethical issues associated with enrolling patients in clinical trials of CEM-101 or Taksta in lieu of prescribing approved antibiotics that have established safety and efficacy profiles. Any of these delays in completing our clinical trials could increase our costs, slow down our product development and approval process and jeopardize our ability to commence product sales and generate revenues.

We may be required to suspend or discontinue clinical trials due to adverse side effects or other safety risks that could preclude approval of CEM-101 or Taksta or any of our future product candidates.

Our clinical trials may be suspended at any time for a number of reasons. A clinical trial may be suspended or terminated by us, our collaborators, the FDA or other regulatory authorities due to a failure to conduct the clinical trial in accordance with regulatory requirements or our clinical protocols, presentation of unforeseen safety issues or adverse side effects, failure to demonstrate a benefit from using the investigational drug, changes in governmental regulations or administrative actions, lack of adequate funding to continue the clinical trial, or negative or equivocal findings of the DSMB or the Institutional Review Board for a clinical trial. We may voluntarily suspend or terminate our clinical trials if at any time we believe that they present an unacceptable risk to participants. In addition, regulatory agencies may order the temporary or permanent discontinuation of our clinical trials at any time if they believe the clinical trials are not being conducted in accordance with applicable regulatory requirements or present an unacceptable safety risk to participants. If we elect or are forced to suspend or terminate any clinical trial

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of any product candidates that we develop, the commercial prospects of such product candidates will be harmed and our ability to generate product revenues, if at all, from any of these product candidates will be delayed or eliminated. Any of these occurrences may harm our business, financial condition, results of operations and prospects significantly.

Taksta is not well absorbed in animals, which could impair our ability to obtain FDA approval.

As required by FDA regulations, we conducted pre-clinical studies of Taksta to determine its level of absorption in animals. The studies indicated that Taksta is not very well absorbed and has a short half-life in animals, resulting in minimum exposure levels which limited the ability to test Taksta in animal models. Fusidic acid, the active pharmaceutical ingredient in Taksta, has been used for several decades in humans outside the U.S. and we believe there is sufficient human clinical trial data for Taksta to overcome the lack of absorption in animal studies. Despite this human data, and while all of our pre-clinical tests were benign and indicated no safety or tolerability issues, our limited ability to test Taksta in animal models may adversely affect our ability to obtain FDA approval.

Even if the FDA approves CEM-101 for the treatment of CABP and Taksta for the treatment of ABSSSI, adverse effects discovered after approval could adversely affect the market for either.

If we obtain regulatory approval for CEM-101, Taksta or any other product candidate that we develop, and we or others later discover that our products cause adverse effects, a number of potentially significant negative consequences could result, including:

Any of these events could prevent us from maintaining market acceptance of the affected product candidate and could substantially increase the costs of, or prevent altogether, the commercialization of our product candidates.

If we fail to obtain additional financing, we may not be able to complete the development and commercialization of CEM-101 or Taksta.

We need substantial amounts of cash to complete the clinical development of CEM-101 and Taksta. We estimate that the net proceeds from this offering will be approximately $         million, assuming an initial public offering price of $         per share (the mid-point of the price range set forth on the cover page of this prospectus), after deducting estimated underwriting discounts and commissions and offering expenses payable by us. We expect that the net proceeds from this offering and our existing cash and cash equivalents, together with interest thereon, will be sufficient to fund our capital requirements into 201    . However, changing circumstances may cause us to consume capital significantly faster than we currently anticipate, and we may need to spend more money than currently expected because of circumstances beyond our control. For example, our clinical trials may encounter technical, enrollment or other issues that could cause our development costs to increase more than we expect and we may be required to conduct additional trials requested by the FDA that could increase our costs significantly. We would also need to raise additional funds sooner if we choose to initiate clinical trials more rapidly than we presently anticipate or if we elect to conduct additional trials for alternate indications. In any event, we will require significant amounts of additional capital to obtain regulatory approval of and to commercialize CEM-101 and Taksta.

We may raise additional capital from the issuance of equity and/or debt securities, collaborations with third parties, out-licensing of rights to our product candidates and other means, or a combination of any of the above. Securing additional financing, however, will require a substantial amount of time and attention from our management and may divert a disproportionate amount of their attention away from our day-to-day activities, which

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may adversely affect our management’s ability to conduct our day-to-day operations. In addition, we cannot guarantee that future financing will be available in sufficient amounts or on terms acceptable to us, if at all. If we are unable to raise additional capital when required or on acceptable terms, we may be required to:

If we are unable to raise additional capital in sufficient amounts or on terms acceptable to us, we will be prevented from pursuing discovery, development and commercialization efforts, and our ability to generate revenues and achieve or sustain profitability will be substantially harmed.

We rely on third parties to conduct our clinical trials. If these third parties do not successfully carry out their contractual duties or meet expected deadlines, we may be delayed in obtaining, or may ultimately not be able to obtain, regulatory approval for or commercialize CEM-101, Taksta or any other product candidates.

We have relied, and plan to continue to rely, on CROs to recruit patients, monitor and manage data for our on-going clinical programs for CEM-101 and Taksta, as well as for the execution of our pre-clinical and non-clinical studies, and we control only certain aspects of our CROs’ activities. Nevertheless, we are responsible for ensuring that each of our studies is conducted in accordance with the applicable protocol, legal, regulatory and scientific standards and our reliance on the CROs does not relieve us of our regulatory responsibilities. We and our CROs are required to comply with the FDA’s current good clinical practices, or cGCPs, which are regulations and guidelines enforced by the FDA for all of our products in clinical development. The FDA enforces these cGCPs through periodic inspections of trial sponsors, principal investigators and clinical trial sites. If we or our CROs fail to comply with applicable cGCPs, the clinical data generated in our clinical trials may be deemed unreliable, and the FDA may require us to perform additional clinical trials before approving our product candidates. We cannot assure you that, upon inspection, the FDA will determine that any of our clinical trials comply with cGCPs. In addition, to evaluate the safety and effectiveness of CEM-101 and Taksta to a statistically significant degree our clinical trials will require an adequately large number of test subjects. Any clinical trial that a CRO conducts abroad on our behalf is subject to similar regulation. Accordingly, if our CROs fail to comply with these regulations or recruit a sufficient number of patients, we may have to repeat clinical trials, which would delay the regulatory approval process.

In addition, our CROs are not our employees and we cannot control whether or not they devote sufficient time and resources to our on-going clinical, non-clinical and pre-clinical programs. Our CROs may also have relationships with other commercial entities, including our competitors, for whom they may also be conducting clinical studies or other drug development activities, which could impede their ability to devote appropriate time to our clinical programs. If our CROs do not successfully carry out their contractual duties or obligations or meet expected deadlines, if they need to be replaced, or if the quality or accuracy of the clinical data they obtain is compromised due to the failure to adhere to our clinical protocols or regulatory requirements, or for other reasons, our clinical trials may be extended, delayed or terminated, and we may not be able to obtain regulatory approval for or successfully commercialize CEM-101, Taksta or any other product candidates that we seek to develop. As a result, our financial results and the commercial prospects for CEM-101, Taksta or any other product candidates that we seek to develop would be harmed, our costs could increase and our ability to generate revenues could be delayed or ended.

We plan to maintain our relationships with existing CROs and enter into agreements with additional CROs to obtain additional resources and expertise in an attempt to accelerate our progress with regard to on-going clinical, non-clinical and pre-clinical programs and specifically, the compilation of clinical trial data for submission with an NDA for each of CEM-101 and Taksta. Switching or entering into new relationships with CROs involves substantial cost and requires extensive management time and focus. In addition, there is a natural transition period when a new CRO commences work. As a result, delays occur, which can materially impact our ability to meet our desired

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clinical development timelines. Although we try to carefully manage our relationships with our CROs, there can be no assurance that we will not encounter challenges or delays in the future or that these delays or challenges will not have a material adverse impact on our business, financial condition, results of operations or prospects.

Our dependence upon third parties for the manufacture and supply of CEM-101, Taksta and any future product candidates may cause delays in, or prevent us from, successfully developing and commercializing our products.

We do not currently have nor do we plan to build the infrastructure or capability internally to manufacture CEM-101 or Taksta for use in the conduct of our clinical trials. We employ the services of Wockhardt Limited, or Wockhardt, to supply the active pharmaceutical ingredient, or API, and finished oral and IV product for CEM-101. We do not have long-term contracts for the commercial supply of CEM-101. We intend to eventually pursue agreements with Wockhardt or transfer the manufacturing to other larger manufacturers. However, we may not be able to negotiate such agreements on acceptable terms, if at all.

We employ the services of Ercros, S.A., or Ercros, to produce Taksta’s API and intend to utilize a third-party manufacturer to produce the finished dosing formulation of Taksta. We have a long-term exclusive supply arrangement with Ercros to produce the fusidic acid used in Taksta in which Ercros agrees to exclusively supply us with fusidic acid in the U.S., and we agree to obtain our supply of fusidic acid for commercial sale exclusively from Ercros, subject to a right to develop a second source for limited supply quantities. We believe Ercros is one of only two currently known manufacturers that can produce fusidic acid compliant with the purity required for human use. The second manufacturer is not available as a supplier to us. Fusidic acid is difficult to produce at these purity levels because of its complex fermentation process. As such, there are underlying risks associated with its manufacture, which could include cost overruns, new impurities, difficulties in scaling up or reproducing manufacturing processes and lack of timely availability of raw materials. We have yet to identify a viable second source of fusidic acid but continue to research alternatives. If Ercros cannot supply sufficient quantities of fusidic acid to make clinical supplies of Taksta, it would harm our ability to develop Taksta. We may not be able to locate a second manufacturer or, if we do, we may not be able to negotiate an agreement on favorable terms, if at all.

In addition, regulatory requirements could pose barriers to the manufacture of our API and finished product for CEM-101 and Taksta. Our third-party manufacturers are required to comply with the FDA’s good manufacturing practices, or cGMP, regulations. As a result, the facilities used by Wockhardt, Ercros, and any of our future manufacturers to manufacture CEM-101 and Taksta must be approved by the FDA after we submit our NDA to the FDA and before approval of CEM-101 and Taksta. Similar regulations apply to manufacturers of our products for use or sale in foreign countries. We do not control the manufacturing process of CEM-101 or Taksta and are completely dependent on these third party manufacturing partners for compliance with the applicable regulatory requirements for the manufacture of CEM-101 and Taksta API and their finished product. If our manufacturers cannot successfully manufacture material that conforms to our specifications and the strict regulatory requirements of the FDA and any applicable foreign regulatory authority, they will not be able to secure the applicable approval for their manufacturing facilities. If these facilities are not approved for the commercial manufacture of CEM-101 or Taksta, we may need to find alternative manufacturing facilities, which would result in significant delays of up to several years in obtaining approval for CEM-101 or Taksta. In addition, our manufacturers will be subject to ongoing periodic unannounced inspections by the FDA and corresponding state and foreign agencies for compliance with cGMPs and similar regulatory requirements.

Finally, we also could experience manufacturing delays if our third-party manufacturers give greater priority to the supply of other products over our product candidates or otherwise do not satisfactorily perform according to the terms of the agreement between us.

If Wockhardt, Ercros, or any alternate supplier of API or finished drug product for CEM-101 or Taksta experiences any significant difficulties in its respective manufacturing processes, does not comply with the terms of the agreement between us or does not devote sufficient time, energy and care to providing our manufacturing needs, we could experience significant interruptions in the supply of CEM-101 or Taksta, which could impair our ability to supply CEM-101 or Taksta at the levels required for our clinical trials and commercialization and prevent or delay their successful development and commercialization.

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The timing of the milestone and royalty payments we are required to make to Optimer Pharmaceuticals, Inc. is uncertain and could adversely affect our cash flows and results of operations.

In March 2006, we entered into a Collaborative Research and Development and License Agreement with Optimer Pharmaceuticals, Inc., or Optimer, pursuant to which we acquired an exclusive license to certain patent applications and other intellectual property related to a series of compounds, including CEM-101, to develop and commercialize licensed products outside of the Association of South East Asian Nations, or ASEAN, countries (Brunei Darussalam, Cambodia, Indonesia, Laos, Malaysia, Myanmar (Burma), the Philippines, Singapore, Thailand and Vietnam). We have an obligation to make additional payments upon achievement of specified development, regulatory and commercialization milestones. The aggregate amount of such milestone payments we may need to pay is based in part on the number of products developed under the agreement. The aggregate amount would be $27.5 million if four products are developed and gain FDA approval. Additional limited milestone payments would be due if we develop more than four products. We will also pay tiered mid-single-digit royalties based on the amount of annual net sales of CEM-101, if and when approved by regulatory authorities. We have already paid a $0.5 million milestone in 2010. The next potential milestone payment payable to Optimer is in the amount of $1.0 million and will become due and payable upon completion of our end of Phase 2 meeting with the FDA for oral CEM-101 if the FDA indicates that the data is reasonably sufficient to support our planned Phase 3 trial for oral CEM-101. Optimer can elect to receive that payment in cash or in shares of our common stock having an equivalent fair market value. The timing of our achievement of these events and corresponding milestone payments to Optimer is subject to factors relating to the clinical and regulatory development and commercialization of CEM-101, many of which are beyond our control. We may become obligated to make a milestone payment when we do not have the cash on hand to make such payment, which could require us to delay our clinical trials, curtail our operations, scale back our commercialization and marketing efforts or seek funds to meet these obligations on terms unfavorable to us. We are obligated to use our diligent efforts to develop and commercialize products licensed from Optimer. We have other obligations to Optimer under the license related to progress reporting, payment terms and confidentiality. Optimer may terminate the agreement in the event of our material breach of the agreement, subject to prior notice and the opportunity to cure. In the event of such termination, Optimer has the right to retain its license and other rights under the agreement, subject to continuing royalties and other obligations. Our material breach of the agreement, including non-payment of any milestone payment, and Optimer’s subsequent termination of the agreement, could result in the loss of our rights to develop and commercialize CEM-101, which would seriously harm our ability to generate revenues or achieve profitability.

The commercial success of CEM-101, Taksta and any other product candidates that we develop, if approved in the future, will depend upon attaining significant market acceptance of these products among physicians and payors.

As a company, we have never commercialized a product candidate for any indication. Even if CEM-101, Taksta or any other product candidates that we develop are approved by the appropriate regulatory authorities for marketing and sale, physicians may not prescribe our approved products, which would prevent us from generating revenues or becoming profitable. Market acceptance of CEM-101, Taksta and any other product candidates that we develop by physicians, patients and payors will depend on a number of factors, many of which are beyond our control, including:

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Even if the medical community accepts that CEM-101 and Taksta are safe and efficacious for their approved indications, physicians may not immediately be receptive to the use or may be slow to adopt CEM-101 as an accepted treatment for CABP and Taksta as an accepted treatment for ABSSSI. While we believe each of CEM-101 and Taksta has significant advantages, we cannot assure you that any labeling approved by the FDA will permit us to promote CEM-101 and Taksta as being superior to competing products. If either or both of CEM-101 or Taksta are approved but do not achieve an adequate level of acceptance by physicians and payors, we may not generate sufficient or any revenues from these products and we may not become profitable. In addition, our efforts to educate the medical community and third-party payors on the benefits of CEM-101 and Taksta may require significant resources and may never be successful.

If approved, CEM-101 and Taksta will face significant competition from branded and generic antibiotics and our operating results will suffer if we fail to compete effectively.

The biotechnology and pharmaceutical industries are intensely competitive and subject to rapid and significant technological change. If CEM-101 or Taksta is approved, we will have competitors both in the U.S. and internationally, including major multinational pharmaceutical companies, established biotechnology companies, specialty pharmaceutical and generic drug companies. Many of these companies have greater financial and other resources, such as larger research and development staffs and more experienced marketing and manufacturing organizations. As a result, these companies may obtain regulatory approval more rapidly and may be more effective in selling and marketing their products. They also may invest heavily to accelerate discovery and development of novel compounds or to in-license novel compounds that could make CEM-101, Taksta or any other product candidates that we develop obsolete. As a result, our competitors may succeed in commercializing antibiotics before we do. Smaller or early-stage companies may also prove to be significant competitors, particularly through collaborative arrangements with large, established companies.

If approved, both CEM-101 and Taksta will face competition from currently commercially available antibiotics, as well as any competing products that may be developed in the future. Existing approved products that will compete with CEM-101 include azithromycin (sold under the brand name Zithromax ^® by Pfizer Inc. and available as a generic), clarithromycin (sold under the brand name Biaxin ^® by Abbott Laboratories and available as a generic), moxifloxacin (sold under the brand name Avelox ^® by Bayer AG), levofloxacin (sold under the brand name Levaquin by Johnson & Johnson and available as a generic), linezolid (sold under the brand name Zyvox by Pfizer Inc.), ceftriaxone (sold under the brand name Rocephin ^® by F. Hoffman-La Roche Ltd and available as a generic) and ceftaroline (sold under the brand name Teflaro ^® by Forest Laboratories, Inc.). Existing approved products that will compete with Taksta include vancomycin (available as a generic), linezolid (sold under the brand name Zyvox by Pfizer Inc.), daptomycin (sold under the brand name Cubicin by Cubist Pharmaceuticals, Inc.), quinupristin/dalfopristin (sold under the brand name Synercid ^® by Sanofi-Aventis and Monarch Pharmaceuticals, Inc.), tigecycline (sold under the brand name Tygacil ^® by Pfizer Inc.), telavancin (sold under the brand name Vibativ ^® by Theravance, Inc. and Astellas Pharma, Inc.) and ceftaroline (sold under the brand name Teflaro by Forest Laboratories, Inc.). Generic antibiotics are typically sold at lower prices than branded antibiotics and are generally preferred by managed care providers of health services.

If we are unable to demonstrate the advantages of CEM-101 or Taksta over competing drugs and drug candidates, we will not be able to successfully commercialize CEM-101 or Taksta and our results of operations will suffer.

Reimbursement may not be available for CEM-101, Taksta or any other product candidates that we develop, which could make it difficult for us to sell our products profitably.

Market acceptance and sales of CEM-101, Taksta or any other product candidates that we develop will depend on reimbursement policies and may be affected by health care reform measures. Government authorities and third-

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party payors, such as private health insurers and health maintenance organizations, decide which drugs they will pay for and establish reimbursement levels. We cannot be sure that reimbursement will be available for CEM-101, Taksta or any other product candidates that we develop. Also, we cannot be sure that the amount of reimbursement available, if any, will not reduce the demand for, or the price of, our products. If reimbursement is not available or is available only at limited levels, we may not be able to successfully commercialize CEM-101, Taksta or any other product candidates that we develop.

Specifically, in both the U.S. and some foreign jurisdictions, there have been a number of legislative and regulatory proposals to change the health care system in ways that could affect our ability to sell our products profitably. In the U.S., the Medicare Prescription Drug, Improvement, and Modernization Act of 2003, also called the Medicare Modernization Act, or MMA, changed the way Medicare covers and pays for pharmaceutical products. The legislation expanded Medicare coverage for drug purchases by the elderly and introduced a new reimbursement methodology based on average sales prices for physician-administered drugs. In addition, this legislation provided authority for limiting the number of drugs that will be covered in any therapeutic class. As a result of this legislation and the expansion of federal coverage of drug products, we expect that there will be additional pressure to contain and reduce costs. These cost reduction initiatives and other provisions of this legislation could decrease the coverage and price that we receive for any approved products and could seriously harm our business. While the MMA applies only to drug benefits for Medicare beneficiaries, private payors often follow Medicare coverage policies and payment limitations in setting their own reimbursement rates, and any reduction in reimbursement that results from the MMA may result in a similar reduction in payments from private payors.

In March 2010, the Patient Protection and Affordable Care Act, as amended by the Health Care and Education Affordability Reconciliation Act, or collectively, PPACA, became law in the U.S. The goal of PPACA is to reduce the cost of health care and substantially change the way health care is financed by both governmental and private insurers. While we cannot predict what impact on federal reimbursement policies this legislation will have in general or on our business specifically, the PPACA may result in downward pressure on pharmaceutical reimbursement, which could negatively affect market acceptance of CEM-101 or Taksta or any future products. Members of the U.S. Congress and some state legislatures are seeking to overturn at least portions of the legislation and we expect they will continue to review and assess this legislation and possibly alternative health care reform proposals. We cannot predict whether new proposals will be made or adopted, when they may be adopted or what impact they may have on us if they are adopted.

The availability of numerous generic antibiotics at lower prices than branded antibiotics, such as CEM-101 or Taksta if either were approved for commercial introduction, may also substantially reduce the likelihood of reimbursement for such products. We expect to experience pricing pressures in connection with the sale of CEM-101, Taksta and any other products that we develop, due to the trend toward managed health care, the increasing influence of health maintenance organizations and additional legislative proposals. If we fail to successfully secure and maintain reimbursement coverage for our products or are significantly delayed in doing so, we will have difficulty achieving market acceptance of our products and our business will be harmed.

We currently have no marketing and sales organization and have no experience as a company in marketing drug products. If we are unable to establish our own marketing and sales capabilities, or enter into agreements with third parties, to market and sell our products after they are approved, we may not be able to generate product revenues.

We do not have a sales organization for the marketing, sales and distribution of any drug products. In order to commercialize any products, we must develop these capabilities on our own or make arrangements with third parties for the marketing, sales and distribution of our products. The establishment and development of our own sales force would be expensive and time consuming and could delay any product launch, and we cannot be certain that we would be able to successfully develop this capability. As a result, we may seek one or more licensing partners to handle some or all of the sales and marketing of CEM-101 for CABP in the U.S. and elsewhere and Taksta for ABSSSI in the U.S. There also may be certain markets within the U.S. for CEM-101 for which we may seek a co-promotion arrangement. However, we may not be able to enter into arrangements with third parties to sell CEM-101 or Taksta on favorable terms or at all. In the event we are unable to develop our own marketing and sales

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force or collaborate with a third-party marketing and sales organization, we would not be able to commercialize CEM-101, Taksta or any other product candidates that we develop, which would negatively impact our ability to generate product revenues. Further, whether we commercialize products on our own or rely on a third party to do so, our ability to generate revenue will be dependent on the effectiveness of the sales force. In addition, to the extent we rely on third parties to commercialize our approved products, we will likely receive less revenues than if we commercialized these products ourselves.

If we are not successful in attracting and retaining highly qualified personnel, we may not be able to successfully implement our business strategy.

Our ability to compete in the highly competitive biotechnology and pharmaceuticals industries depends in large part on our ability to attract and retain highly qualified managerial, scientific and medical personnel. In order to induce valuable employees to remain with us, we have provided stock options that vest over time. The value to employees of stock options will be significantly affected by movements in our stock price that we cannot control and may at any time be insufficient to counteract more lucrative offers from other companies.

Our scientific team has expertise in many different aspects of drug discovery and development. We conduct our operations at our facility in Chapel Hill, North Carolina, which is part of the Research Triangle consisting of Raleigh, Durham and Chapel Hill. This region is headquarters to other biopharmaceutical companies and many academic and research institutions and, as a result, at any given time there may be a shortage of experienced scientists and medical personnel. Competition for skilled personnel in our area and elsewhere in the U.S. is very intense and competition for experienced scientists may limit our ability to hire and retain highly qualified personnel on acceptable terms or at all.

Despite our efforts to retain valuable employees, members of our management, scientific and medical teams may terminate their employment with us on short notice. We do not have employment agreements with Prabhavathi Fernandes, our Chief Executive Officer, Mark W. Hahn, our Chief Financial Officer, any of the key employees identified under “Management” or any other employee. As a result, all employees are employed on an at-will basis, which means that any of these employees could leave our employment at any time, with or without notice, and may go to work for a competitor. The loss of the services of any of our executive officers or other key employees could potentially harm our business, operating results or financial condition. Our success also depends on our ability to continue to attract, retain and motivate highly skilled scientific and medical personnel.

Other biotechnology and pharmaceutical companies with which we compete for qualified personnel have greater financial and other resources, different risk profiles and longer histories than we do. They also may provide more diverse opportunities and better chances for career advancement. Some of these characteristics may be more appealing to high quality candidates than what we offer. If we are unable to continue to attract and retain high quality personnel, our ability to discover, develop and commercialize drug candidates will be limited.

We will need to grow our organization, and we may experience difficulties in managing this growth, which could disrupt our operations.

As of September 30, 2011, we had 15 employees. As our development and commercialization plans and strategies develop, we expect to expand our employee base for managerial, operational, financial and other resources and, depending on our commercialization strategy, we may further expand our employee base for sales and marketing resources. Future growth would impose significant added responsibilities on members of management, including the need to identify, recruit, maintain, motivate and integrate additional employees. Also, our management may need to divert a disproportionate amount of its attention away from their day-to-day activities and devote a substantial amount of time to managing these growth activities. We may not be able to effectively manage the expansion of our operations which may result in weaknesses in our infrastructure, give rise to operational mistakes, loss of business opportunities, loss of employees and reduced productivity among remaining employees. Our expected growth could require significant capital expenditures and may divert financial resources from other projects, such as the development of additional product candidates. If our management is unable to effectively manage our expected growth, our expenses may increase more than expected, our ability to generate and/or grow revenues could be reduced and we may not be able to implement our business strategy. Our future financial performance and our ability to commercialize CEM-101, Taksta and our other product candidates and compete effectively will depend, in part, on our ability to effectively manage any future growth in our organization.

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Even if we obtain FDA approval of CEM-101, or any other product candidate, we may never obtain approval or commercialize our products outside of the U.S., which would limit our ability to realize their full market potential. If foreign approval is obtained, there are risks in conducting business in international markets.

In order to market CEM-101 or any other products outside of the U.S., we must establish and comply with numerous and varying regulatory requirements of other countries regarding safety and efficacy. Clinical trials conducted in one country may not be accepted by regulatory authorities in other countries, and regulatory approval in one country does not mean that regulatory approval will be obtained in any other country. Approval procedures vary among countries and can involve additional product testing and validation and additional administrative review periods. Seeking foreign regulatory approvals could result in significant delays, difficulties and costs for us and require additional pre-clinical studies or clinical trials which would be costly and time consuming. Regulatory requirements can vary widely from country to country and could delay or prevent the introduction of our products in those countries. Satisfying these and other regulatory requirements is costly, time consuming, uncertain and subject to unanticipated delays. In addition, our failure to obtain regulatory approval in the U.S. or any foreign country may delay or have negative effects on the process for regulatory approval in other countries. We do not have any product candidates approved for sale in the U.S. or any foreign country and we do not have experience as a company in obtaining regulatory approval in international markets. If we fail to comply with regulatory requirements in a foreign country or to obtain and maintain required approvals, our potential market for CEM-101 or other products will be reduced and our ability to realize the full market potential of our products will be harmed. We do not intend to commercialize Taksta outside the U.S. because of the widespread use of fusidic acid in Europe and Australia.

If approved for commercialization in a foreign country, we intend to enter into agreements with third parties to market CEM-101 whenever it may be approved and wherever we have the right to market it. Consequently, we expect that we will be subject to additional risks related to entering into international business relationships, including:

These and other risks may materially adversely affect our ability to attain or sustain revenue from international markets.

Our employees may engage in misconduct or other improper activities, including noncompliance with regulatory standards and requirements and insider trading.

We are exposed to the risk of employee fraud or other misconduct. Misconduct by employees could include intentional failures to comply with FDA regulations, provide accurate information to the FDA, comply with federal and state health care fraud and abuse laws and regulations, report financial information or data accurately or disclose unauthorized activities to us. In particular, sales, marketing and business arrangements in the health care industry are subject to extensive laws and regulations intended to prevent fraud, misconduct, kickbacks, self-dealing and other abusive practices. These laws and regulations may restrict or prohibit a wide range of pricing, discounting,

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marketing and promotion, sales commission, customer incentive programs and other business arrangements. Employee misconduct could also involve the improper use of information obtained in the course of clinical trials, which could result in regulatory sanctions and serious harm to our reputation. We have adopted a Code of Conduct, but it is not always possible to identify and deter employee misconduct, and the precautions we take to detect and prevent this 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 to be in compliance with these 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, including the imposition of significant fines or other sanctions.

We have incurred significant operating losses since inception and anticipate that we will incur continued losses for the foreseeable future.

As of June 30, 2011, we had an accumulated deficit of approximately $84.3 million. We have funded our operations to date from the private sale of equity and debt securities. We expect to incur substantial additional losses over the next several years as our research, development, pre-clinical testing, and clinical trial activities increase, especially those related to CEM-101 and Taksta. In addition, we will incur additional costs operating as a public company. The amount of future losses and when, if ever, we will achieve profitability are uncertain.

To raise additional funds to support our business operations, we may issue equity or debt securities. Debt securities could contain restrictive covenants that may adversely impact the operation of our business. The issuance of equity securities or convertible debt securities would result in dilution to our stockholders.

The incurrence of indebtedness would result in increased fixed payment obligations and could also result in certain restrictive covenants, such as limitations on our ability to incur additional debt, limitations on our ability to acquire, sell or license intellectual property rights and other operating restrictions that could adversely impact our ability to conduct our business. For example, the August 2011 Notes contain restrictive covenants that prohibit us from incurring new indebtedness in excess of $0.5 million in the aggregate and granting a security interest on any of our material assets without the consent of the holders of at least a majority of the aggregate outstanding principal amount of the August 2011 Notes. In addition, the sale of equity securities or convertible debt securities would result in the issuance of additional shares of our capital stock, which would result in dilution to our stockholders.

Our independent registered public accounting firm, in their audit report related to our financial statements for the three years ended December 31, 2010, expressed substantial doubt about our ability to continue as a going concern.

As a result of our continued losses, our independent registered public accounting firm has included an explanatory paragraph in its report on our financial statements for the three fiscal years ended December 31, 2010, expressing substantial doubt as to our ability to continue as a going concern. The inclusion of a going concern explanatory paragraph in the report of our independent registered public accounting firm may make it more difficult for us to secure additional financing or enter into strategic relationships on terms acceptable to us, if at all, and may materially and adversely affect the terms of any financing that we might obtain.

Our limited operating history makes it difficult to evaluate our business and prospects.

We began operations in 2006. Our operations to date have been limited to financing and staffing our company, conducting product development activities for CEM-101 and Taksta and performing research and development with respect to our proprietary macrolide library. We have not yet demonstrated an ability as a company to obtain regulatory approval for or commercialize a product candidate. Consequently, the ability to predict our future performance may not be as accurate as they could be if we had a history of successfully developing and commercializing pharmaceutical products.

Risks Related to Our Industry

We are subject to extensive and costly government regulation.

Antibiotics, including those we are developing and plan to develop in the future, are subject to extensive and rigorous domestic government regulation including regulation by the FDA, the Centers for Medicare and Medicaid

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Services, other divisions of the U.S. Department of Health and Human Services, the U.S. Department of Justice, state and local governments and their respective foreign equivalents. The FDA regulates the research, development, pre-clinical and clinical testing, manufacture, safety, effectiveness, record keeping, reporting, labeling, storage, approval, advertising, promotion, sale, distribution, import and export of pharmaceutical products. If any products we develop are tested or marketed abroad, they will also be subject to extensive regulation by foreign governments, whether or not we have obtained FDA approval for a given product and its uses. Such foreign regulation may be equally or more demanding than corresponding U.S. regulation.

Government regulation substantially increases the cost and risk of researching, developing, manufacturing and selling products. Our failure to comply with these regulations could result in significant fines or the inability of our product candidates to obtain and maintain regulatory approval, which would have a materially adverse effect on our business, financial condition, results of operations and prospects.

Even if we obtain regulatory approval for CEM-101, Taksta or any of our future product candidates, we will still face extensive regulatory requirements and our products may face future development and regulatory difficulties.

Even if regulatory approval in the U.S. is obtained, the FDA may still impose significant restrictions on a product’s indicated uses or marketing or impose ongoing requirements for potentially costly post-approval studies or post-market surveillance. For example, the labeling ultimately approved for CEM-101 and/or Taksta if any, may include restrictions on use. CEM-101, Taksta or any of our other product candidates will also be subject to ongoing FDA requirements governing the labeling, packaging, storage, distribution, safety surveillance, advertising, promotion, record keeping and reporting of safety and other post-market information. The holder of an approved NDA is subject to obligations to monitor and report adverse events and instances of the failure of a product to meet the specifications in the NDA. Application holders must submit new or supplemental applications and obtain FDA approval for certain changes to the approved product, product labeling or manufacturing process. Application holders must also submit advertising and other promotional material to the FDA and report on ongoing clinical trials. Legal requirements have also been enacted to require disclosure of clinical trial results on publicly available databases.

In addition, manufacturers of drug products and their facilities are subject to continual review and periodic inspections by the FDA and other regulatory authorities for compliance with cGMP regulations. If we or a regulatory agency discovers previously unknown problems with a product, such as adverse events of unanticipated severity or frequency, or problems with the facility where the product is manufactured, a regulatory agency may impose restrictions on that product, the manufacturing facility or us, including requiring recall or withdrawal of the product from the market or suspension of manufacturing. Advertising and promotional materials must comply with FDA rules in addition to other potentially applicable federal and state laws. The distribution of product samples to physicians must comply with the requirements of the Prescription Drug Marketing Act. Sales, marketing and scientific/educational grant programs must comply with the anti-fraud and abuse provisions of the Social Security Act, the False Claims Act and similar state laws, each as amended. Pricing and rebate programs must comply with the Medicaid rebate requirements of the Omnibus Budget Reconciliation Act of 1990 and the Veteran’s Health Care Act of 1992, each as amended. If products are made available to authorized users of the Federal Supply Schedule of the General Services Administration, additional laws and requirements apply. All of these activities are also potentially subject to federal and state consumer protection and unfair competition laws. If we or our third party collaborators fail to comply with applicable regulatory requirements, a regulatory agency may:

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The occurrence of any event or penalty described above may force us to expend significant amounts of time and money and may significantly inhibit our ability to bring to market or continue to market our products and generate revenues. Similar regulations apply in foreign jurisdictions.

Product liability lawsuits could divert our resources, result in substantial liabilities and reduce the commercial potential of our products.

We face an inherent risk of product liability as a result of the clinical testing of our product candidates despite obtaining appropriate informed consents from our clinical trial participants, and will face an even greater risk if we commercialize CEM-101 or Taksta in the U.S. or other additional jurisdictions or if we engage in the clinical testing of new product candidates or commercialize any additional products. For example, we may be sued if any product we develop allegedly causes injury or is found to be otherwise unsuitable during clinical testing, manufacturing, marketing or sale. Any such product liability claims may include allegations of defects in manufacturing, defects in design, a failure to warn of dangers inherent in the product, negligence, strict liability or a breach of warranties. Claims could also be asserted under state consumer protection acts. If we cannot successfully defend ourselves against product liability claims, we may incur substantial liabilities or be required to limit commercialization of our product candidates. Even successful defense would require significant financial and management resources. Regardless of the merits or eventual outcome, liability claims may result in:

Although we maintain general liability insurance of up to $2.0 million in the aggregate and clinical trial liability insurance of $5.0 million in the aggregate for each of CEM-101 and Taksta, this insurance may not fully cover potential liabilities. The cost of any product liability litigation or other proceeding, even if resolved in our favor, could be substantial. In addition, inability to obtain or maintain sufficient insurance coverage at an acceptable cost or to otherwise protect against potential product liability claims could prevent or inhibit the development and commercial production and sale of our products, which could adversely affect our business, financial condition, results of operations, and prospects.

If we use hazardous and biological materials in a manner that causes injury or violates applicable law, we may be liable for damages.

Our research and development activities involve the controlled use of potentially hazardous substances, including chemical, biological and radioactive materials and viruses. In addition, our operations produce hazardous waste products. Federal, state and local laws and regulations in the U.S. govern the use, manufacture, storage, handling and disposal of hazardous materials. Although we believe that our procedures for use, handling, storing and disposing of these materials comply with legally prescribed standards, we may incur significant additional costs to comply with applicable laws in the future. We also cannot predict the impact on our business of new or amended environmental laws or regulations, or any changes in the way existing and future laws and regulations are interpreted or enforced. Also, even if we are in compliance with applicable laws, we cannot completely eliminate the risk of contamination or injury resulting from hazardous materials, and we may incur liability as a result of any such contamination or injury. In the event of an accident, we could be held liable for damages or penalized with fines, and the liability could exceed our resources or liability insurance coverage. If we fail to comply with applicable requirements, we could incur substantial costs, including civil or criminal fines and penalties, clean-up

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costs, or capital expenditures for control equipment or operational changes necessary to achieve or maintain compliance. Compliance with applicable environmental laws and regulations is expensive, and current or future environmental regulations may impair our research, development and production efforts, which adversely affect our business, financial condition, results of operations, and prospects.

Risks Related to our Intellectual Property

Our ability to pursue the development and commercialization of CEM-101 depends upon the continuation of our license from Optimer.

Our agreement with Optimer provides us with a worldwide exclusive license to develop and sell CEM-101 outside of ASEAN countries. If we are unable to make the required milestone and royalty payments under the agreement, if we do not continue to use diligent efforts to develop and commercialize CEM-101 or if we otherwise materially breach the agreement, our rights to develop and commercialize CEM-101 would terminate and revert to Optimer. In addition, either we or Optimer may terminate the agreement upon the uncured material breach of the agreement. If our agreement with Optimer is terminated by Optimer, we would lose our rights to develop and commercialize CEM-101, which would adversely affect our business, financial condition, results of operations, and prospects.

Another party could develop a fusidic acid product for treatment of ABSSSI and achieve FDA regulatory exclusivity in the U.S. before we do, preventing our ability to commercialize Taksta.

We will rely partly on FDA regulatory exclusivity to protect our proprietary rights for Taksta, our fusidic acid product, in the U.S. Fusidic acid has been approved and sold for several decades in Europe and other countries outside the U.S., but it has never been approved in the U.S. We believe this was due to the lack of regulatory exclusivity that was available for the molecule until the passage of Public Law 110-379 on October 8, 2008, which allowed old antibiotics such as fusidic acid to obtain five-year new chemical entity, or NCE, exclusivity upon NDA approval. We are developing Taksta to treat ABSSSI. Exclusivity will be granted to the first NDA approval for a fusidic acid product treating ABSSSI. Although we are not aware of another party currently developing fusidic acid for the treatment of ABSSSI, if another party were to develop fusidic acid and obtain NDA approval before we do, we would not be able to obtain approval for Taksta until after any period of regulatory exclusivity and we would not be able to feasibly commercialize Taksta. Our inability to commercialize Taksta would harm our ability to generate revenue and achieve profitability.

If our efforts to protect the proprietary nature of the intellectual property related to CEM-101, Taksta, and our other product candidates are not adequate, we may not be able to compete effectively in our market.

Our commercial success will depend in part on our ability to obtain additional patents and protect our existing patent position as well as our ability to maintain adequate protection of other intellectual property for CEM-101, Taksta and any future products in the U.S. and other countries. If we do not adequately protect our intellectual property, competitors may be able to use our technologies and erode or negate any competitive advantage we may have, which could harm our business and ability to achieve profitability. The patent positions of pharmaceutical companies are highly uncertain. The legal principles applicable to patents are in transition due to changing court precedent and legislative action and we cannot assure you that the historical legal standards surrounding questions of validity will continue to be applied or that current defenses relating to issued patents in these fields will be sufficient in the future. Changes in patent laws in the U.S. such as the recently adopted America Invents Act of 2011 may affect the scope, strength and enforceability of our patent rights or the nature of proceedings which may be brought by us related to our patent rights. In addition, the laws of some foreign countries do not protect our proprietary rights to the same extent as the laws of the U.S., and we may encounter significant problems in protecting our proprietary rights in these countries. We will be able to protect our proprietary rights from unauthorized use by third parties only to the extent that our proprietary technologies, CEM-101, Taksta and any future products are covered by valid and enforceable patents or are effectively maintained as trade secrets.

These risks include the possibility that:

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While we apply for patents covering both our technologies and products CEM-101 and Taksta, as we deem appropriate, many biopharmaceutical companies and university and research institutions already have filed patent applications or have received patents in our areas of product development. These entities’ applications, patents and other intellectual property rights may conflict with patent applications to which we have rights and could prevent us from obtaining patents or could call into question the validity of any of our patents, if issued, or could otherwise adversely affect our ability to develop, manufacture or commercialize antibiotic candidates. In addition, if third parties file patent applications in the technologies that also claim technology to which we have rights, we may have to participate in interference, derivation or other proceedings with the U.S. Patent and Trademark Office, or USPTO, or applicable foreign patent regulatory authorities, as applicable, to determine our rights in the invention, which may be time-consuming and expensive. Moreover, issued patents may be challenged during post-grant proceedings brought by a third party or the USPTO, or in foreign countries, or in the courts. These proceedings may result in loss of patent claims or adverse changes to the scope of the claims.

If we or our licensors or partners fail to obtain and maintain patent protection for our product candidates, or our proprietary technologies and their uses, companies may be dissuaded from collaborating with us. In such event, our ability to commercialize CEM-101, Taksta and our other product candidates may be threatened, we could lose our competitive advantage and the competition we face could increase, all of which could adversely affect on our business, financial condition, results of operations, and prospects.

If we are sued for infringing intellectual property rights of third parties, litigation will be costly and time consuming and could prevent us or delay us from developing or commercializing our product candidates.

Our commercial success depends, in part, on our not infringing the patents and proprietary rights of other parties and not breaching any collaboration or other agreements we have entered into with regard to our technologies and products. Numerous third-party U.S. and non-U.S. issued patents and pending applications exist in the areas of antibacterial treatment, including compounds, formulations, and treatment methods. We cannot provide assurances that we or our partners will be free to market our product candidates as planned, or that we or our licensors’ and partners’ patents will not be opposed or litigated by third parties.

There is a substantial amount of litigation involving intellectual property in the biopharmaceutical industry generally. If a third party asserts that we infringe its patents or other proprietary rights, we could face a number of risks that could adversely affect our business, financial condition, results of operations, and prospects, including:

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Although we are not currently party to any legal proceedings relating to our intellectual property, in the future, third parties may file claims asserting that our technologies or products infringe on their intellectual property. We cannot predict whether third parties will assert these claims against us or our partners or against the licensors of technology licensed to us, or whether those claims will harm our business. In addition, the outcome of intellectual property litigation is subject to uncertainties that cannot be adequately quantified in advance. If we or our partners were to face infringement claims or challenges by third parties relating to our product candidates, an adverse outcome could subject us to significant liabilities to such third parties, and force us or our partners to curtail or cease the development of some or all of our product candidates, which could adversely affect our business, financial condition, results of operations, and prospects.

We may be required to file lawsuits or take other actions to protect or enforce our patents or the patents of our licensors, which could be expensive and time consuming.

Competitors may infringe our patents or the patents of our licensors. To counter infringement or unauthorized use, we may be required to file infringement claims, which can be expensive and time-consuming. Moreover, there can be no assurance that we will have sufficient financial or other resources to file and pursue such infringement claims, which typically last for years before they are concluded. The legal systems of certain countries, particularly certain developing countries, do not favor the enforcement of patents and other intellectual property protection, particularly those relating to biopharmaceuticals, which could make it difficult for us to stop the infringement of our patents or marketing of competing products in violation of our proprietary rights generally.

In addition, in an infringement proceeding, a court may decide that a patent of ours or our licensors is not valid or is unenforceable, or may refuse to stop the other party from using the technology at issue on the grounds that our patents, or those of our licensors, do not cover the technology in question. An adverse result in any litigation or defense proceedings could put one or more of our patents, or those of our licensors, at risk of being invalidated, held unenforceable or interpreted narrowly and could put our patent applications, or those of our licensors, at risk of not issuing. Moreover, we may not be able to prevent, alone or with our licensors, misappropriation of our proprietary rights, particularly in countries where the laws may not protect those rights as fully as in the U.S. Furthermore, because of the substantial amount of discovery required in connection with intellectual property litigation, there is a risk that some of our confidential information could be compromised by disclosure during this type of litigation. In addition, if securities analysts or investors perceive public announcements of the results of hearings, motions or other interim proceedings or developments to be negative, the price of our common stock could be adversely affected. The occurrence of any of the above could adversely affect our business, financial condition, results of operations, and prospects.

The intellectual property protection for our products is dependent on third parties.

With respect to patent applications relating to CEM-101 or other compounds licensed from Optimer, Optimer retains rights in ASEAN countries. Generally, we do not have the right to prosecute and maintain any applications in those countries, unless Optimer elects not to file, prosecute or maintain any or all of such patents. Our potential future licensors also may retain the right to prosecute and maintain the patent rights that they license to us. If Optimer or other licensors fail to appropriately prosecute and maintain patent protection for any of our product candidates in those countries controlled by them, our ability to develop and commercialize those products may be adversely affected and we may not be able to prevent competitors from making, using and selling competing products in those countries.

With respect to inventions that are jointly made by us and one of our licensors, partners or potential partners, we would need to determine, with our licensors, partners or potential partners, who would be responsible for the

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prosecution of patents relating to any joint inventions should they arise. In addition, we may be required to cede control of prosecution of our patents to partners or potential partners in order to consummate a partnering transaction. If any of our licensors or partners fails to appropriately prosecute and maintain patent protection for any of our product candidates in those countries controlled by them, our ability to develop and commercialize those products may be adversely affected and we may not be able to prevent competitors from making, using and selling competing products in those countries.

If we are unable to protect the confidentiality of certain information, the value of our products and technology could be materially adversely affected.

We also rely on trade secrets, know-how and continuing technological advancement to develop and maintain our competitive position. To protect this competitive position, we regularly enter into confidentiality and proprietary information agreements with third parties, including employees, independent contractors, suppliers and collaborators. We cannot, however, ensure that these protective arrangements will be honored by third parties, and we may not have adequate remedies if these arrangements are breached. In addition, enforcement of claims that a third party has illegally obtained and is using trade secrets, know-how and technological advancements is expensive, time consuming and uncertain. Non-U.S. courts are sometimes less willing than U.S. courts to protect this information. Moreover, our trade secrets, know-how and technological advancements may otherwise become known or be independently developed by competitors in a manner providing us with no practical recourse against the competing parties. If any such events were to occur, they could adversely affect our business, financial condition, results of operations, and prospects.

We have not yet registered our trademarks in all of our potential markets, and failure to secure those registrations could adversely affect our business.

The USPTO has allowed our trademark applications for our mark “Taksta”, and, if we submit statements of use to the USPTO in a timely manner, the USPTO will issue trademark registrations, subject to unforeseen circumstances that arise. Although we are not currently aware of any oppositions to or cancellations of our registered trademarks or pending applications, it is possible that one or more of the applications could be subject to opposition or cancellation after the marks are registered. The registrations will be subject to use and maintenance requirements. We have not yet registered all of our trademarks in all of our potential markets and there are names or symbols other than “Cempra” that may be protectable marks for which we have not sought registration. Failure to secure those registrations could adversely affect our business. We cannot assure you that opposition or cancellation proceedings will not be filed against our trademarks or that our trademarks would survive such proceedings.

We may be subject to claims that our employees have wrongfully used or disclosed alleged trade secrets of their former employers.

As is common in the biotechnology and pharmaceutical industries, we employ individuals who were previously employed at other biotechnology or pharmaceutical companies, including our competitors or potential competitors. We may be subject to claims that these employees, or we, have inadvertently or otherwise used or disclosed trade secrets or other proprietary information of their former employers. Litigation may be necessary to defend against these claims. Such claims may lead to material costs for us, or an inability to protect or use valuable intellectual property rights, which could adversely affect our business, financial condition, results of operations, and prospects.

Risks Related to this Offering and Ownership of Our Common Stock

There is no existing market for our common stock and we do not know if one will develop to provide you with adequate liquidity.

Prior to this offering, there has not been a public market for our common stock. We cannot assure you that an active trading market for our common stock will develop following this offering, or if it does develop, it may not be maintained. You may not be able to sell your shares quickly or at the market price if trading in our common stock is not active. The initial public offering price for the shares will be determined by negotiations between us and representatives of the underwriters and may not be indicative of prices that will prevail in the trading market.

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The market price of our common stock may be highly volatile, and you could lose all or part of your investment.

The trading price of our common stock is likely to be volatile. This volatility may prevent you from being able to sell your shares at or above the price you paid for your shares. Our stock price could be subject to wide fluctuations in response to a variety of factors, which include:

In addition, the stock market in general, and the NASDAQ Global Market and the stock of biotechnology companies in particular, have experienced extreme price and volume fluctuations that have often been unrelated or disproportionate to the operating performance of these companies. Broad market and industry factors may negatively affect the market price of our common stock, regardless of our actual operating performance.

Our principal stockholders and management own a significant percentage of our stock and will be able to exert significant control over matters subject to stockholder approval.

At September 30, 2011, our executive officers, directors, holders of 5% or more of our stock and their affiliates beneficially owned approximately 87.9% of our voting stock on an as-if converted basis and, after giving effect to the corporate conversion and upon completion of this offering, will hold approximately     % of our outstanding voting stock (assuming no exercise of the underwriters’ over-allotment option and an initial public offering price of

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$         (the mid-point of the price range set forth on the cover page of this prospectus)). Therefore, even after this offering, these stockholders will continue to have the ability to influence us through their ownership position. These stockholders may be able to determine the outcome of all matters requiring stockholder approval. For example, these stockholders may be able to control elections of directors, amendments of our organizational documents, or approval of any merger, sale of assets, or other major corporate transaction. This may prevent or discourage unsolicited acquisition proposals or offers for our common stock that you may feel are in your best interest as one of our stockholders.

We have broad discretion in the use of the net proceeds from this offering and may not use them effectively.

Our management will have broad discretion in the application of the net proceeds from this offering, including for any of the purposes described in the section entitled “Use of Proceeds,” and you will not have the opportunity as part of your investment decision to assess whether the net proceeds are being used appropriately. Our management may not apply our net proceeds in ways that ultimately increase the value of your investment. Because of the number and variability of factors that will determine our use of the net proceeds from this offering, their ultimate use may vary substantially from their currently-intended use. Pending their use, we may invest the net proceeds from this offering in short-term, investment-grade, interest-bearing securities. These investments may not yield a favorable return to our stockholders. If we do not invest or apply the net proceeds from this offering in ways that enhance stockholder value, we may fail to achieve expected financial results, which could cause the price of our common stock to decline.

We will incur significant increased costs as a result of operating as a public company and our management will be required to devote substantial time to new compliance initiatives.

As a public company, we will incur significant legal, accounting and other expenses that we did not incur as a private company. The Sarbanes-Oxley Act of 2002, or the Sarbanes-Oxley Act, as well as rules subsequently implemented by the Securities and Exchange Commission, or SEC, and the NASDAQ Global Market have imposed various requirements on public companies. Our management and other personnel will need to devote a substantial amount of time to these compliance initiatives. Moreover, we anticipate that compliance with these rules and regulations will increase our legal, accounting and financial compliance costs substantially, may make related activities more difficult, time-consuming and costly and may also place undue strain on our personnel, systems and resources. If these requirements divert the attention of our management and personnel from other business concerns, they could have a material adverse effect on our business, financial condition and results of operations. For example, we expect these rules and regulations to make it more difficult and more expensive for us to obtain director and officer liability insurance, and we may be required to incur substantial costs to maintain our current levels of such coverage. We cannot predict or estimate the amount or timing of additional costs we may incur to respond to these requirements.

If we fail to establish and maintain proper internal controls, our ability to produce accurate financial statements or comply with applicable regulations could be impaired.

Pursuant to Section 404 of the Sarbanes-Oxley Act, our management will be required to deliver a report that assesses the effectiveness of our internal control over financial reporting for the year ending December 31, 2013. Unless we qualify for an exemption as a non-accelerated filer, under current SEC rules, our independent registered public accounting firm will also be required to deliver an attestation report on the effectiveness of our internal control over financial reporting beginning with the year ending December 31, 2013. Prior to becoming a public company, we were not required to comply with Section 404 of the Sarbanes-Oxley Act, and, as a result, we have not yet evaluated our compliance with its provisions.

If we conclude that our internal control over financial reporting is not effective, we cannot be certain as to the timing of completion of our evaluation, testing and remediation actions or their effect on our operations because there is presently no precedent available by which to measure compliance adequacy. As a consequence, we may not be able to complete our remediation process in time to meet our deadline for compliance with Section 404 of the Sarbanes-Oxley Act. Also, there can be no assurance that we will not identify one or more material weaknesses in our internal controls in connection with evaluating our compliance with Section 404 of the Sarbanes-Oxley Act. The presence of material weaknesses could result in financial statement errors which, in turn, could require us to restate our operating results.

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If we are unable to conclude that we have effective internal control over financial reporting or if our independent auditors are unwilling or unable to provide us with an attestation report on the effectiveness of internal control over financial reporting as required by Section 404 of the Sarbanes-Oxley Act, investors may lose confidence in our operating results, our stock price could decline and we may be subject to litigation or regulatory enforcement actions. In addition, if we are unable to meet the requirements of Section 404 of the Sarbanes-Oxley Act, we may not be able to remain listed on the NASDAQ Global Market.

If you purchase our common stock in this offering, you will incur immediate and substantial dilution in the book value of your shares.

The initial public offering price is substantially higher than the net tangible book value per share of our common stock. Investors purchasing common stock in this offering will pay a price per share that substantially exceeds the book value of our tangible assets after subtracting our liabilities. As a result, investors purchasing common stock in this offering will incur immediate dilution of $         per share, assuming an initial public offering price of $         per share (the mid-point of the price range set forth on the cover page of this prospectus). Further, investors purchasing common stock in this offering will contribute approximately     % of the total amount invested by stockholders since our inception, but will own only approximately     % of the shares of common stock outstanding.

This dilution is due to our investors who purchased shares prior to this offering having paid substantially less for their shares than the price offered to the public in this offering. In addition, as of September 30, 2011, options to purchase 6,903,791 shares of our common stock at a weighted average exercise price of $0.21 per share were outstanding. Further, assuming the corporate conversion and the completion of this offering had occurred on September 30, 2011, warrants exercisable for up to              shares of our common stock at an exercise price of $         per share were outstanding, assuming an initial public offering price of $         (the mid-point of the price range set forth on the cover page of this prospectus). The exercise of any of these options or warrants would result in additional dilution. As a result of the dilution to investors purchasing shares in this offering, investors may receive significantly less than the purchase price paid in this offering, if anything, in the event of our liquidation.

Sales of a substantial number of shares of our common stock in the public market by our existing stockholders could cause our stock price to decline.

Sales of a substantial number of shares of our common stock in the public market or the perception that these sales might occur, could depress the market price of our common stock and could impair our ability to raise capital through the sale of additional equity securities. We are unable to predict the effect that sales may have on the prevailing market price of our common stock.

Substantially all of our existing stockholders are subject to lock-up agreements with the underwriters of this offering that restrict the stockholders’ ability to transfer shares of our common stock for at least 180 days from the date of this prospectus. The lock-up agreements limit the number of shares of common stock that may be sold immediately following the public offering. Subject to certain limitations, approximately              of our total outstanding shares will be eligible for sale upon expiration of the lock-up period. In addition, shares issued or issuable upon exercise of options and warrants vested as of the expiration of the lock-up period will be eligible for sale at that time. Sales of stock by these stockholders could have a material adverse effect on the trading price of our common stock.

Certain holders of shares of our common stock are entitled to rights with respect to the registration of their shares under the Securities Act of 1933, as amended, or the Securities Act, subject to the 180-day lock-up arrangement described above. Registration of these shares under the Securities Act would result in the shares becoming freely tradable without restriction under the Securities Act, except for shares held by our affiliates as defined in Rule 144 under the Securities Act. Sales of stock by these stockholders could have a material adverse effect on the trading price of our common stock.

If securities or industry analysts do not publish research or publish inaccurate or unfavorable research about our business, our stock price and trading volume could decline.

The trading market for our common stock will depend in part on the research and reports that securities or industry analysts publish about us or our business. Securities and industry analysts do not currently, and may never,

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publish research on our company. If no securities or industry analysts commence coverage of our company, the trading price for our stock would likely be negatively impacted. In the event securities or industry analysts initiate coverage, if one or more of the analysts who cover us downgrade our stock or publish inaccurate or unfavorable research about our business, our stock price would likely decline. If one or more of these analysts cease coverage of us or fail to publish reports on us regularly, we could lose visibility in the financial markets, which might cause our stock price and trading volume to decline.

Our ability to use our net operating loss carry-forwards and certain other tax attributes may be limited.

Under Section 382 of the Internal Revenue Code of 1986, as amended, referred to as the Internal Revenue Code, if a corporation undergoes an “ownership change” (generally defined as a greater than 50% change (by value) in its equity ownership over a three-year period), the corporation’s ability to use its pre-change net operating loss carry-forwards and other pre-change tax attributes (such as research tax credits) to offset its post-change income may be limited. We believe that, with this offering, our August 2011 private placement and other transactions that have occurred over the past three years, we may have triggered an “ownership change” limitation. We may also experience ownership changes in the future as a result of subsequent shifts in our stock ownership, including as a result of the completion of this offering. As a result, if we earn net taxable income, our ability to use our pre-change net operating loss carry-forwards to offset U.S. federal taxable income may be subject to limitations, which potentially could result in increased future tax liability to us.

We do not intend to pay dividends on our common stock so any returns will be limited to the value of our stock.

We have never declared or paid any cash dividend on our common stock. We currently anticipate that we will retain future earnings for the development, operation and expansion of our business and do not anticipate declaring or paying any cash dividends for the foreseeable future. Any return to stockholders will be limited to the value of their stock.

Some provisions of our charter documents and Delaware law may have anti-takeover effects that could discourage an acquisition of us by others, even if an acquisition would be beneficial to our stockholders and may prevent attempts by our stockholders to replace or remove our current management.

Provisions in our certificate of incorporation and bylaws, as well as provisions of Delaware law, could make it more difficult for a third party to acquire us or increase the cost of acquiring us, even if an acquisition would benefit our stockholders, and could also make it more difficult to remove our current management. These provisions include:

These provisions may frustrate or prevent any attempts by our stockholders to replace or remove our current management by making it more difficult for stockholders to replace members of our board of directors, which is responsible for appointing the members of our management. In addition, we are subject to Section 203 of the Delaware General Corporation Law, which generally prohibits a Delaware corporation from engaging in any of a broad range of business combinations with an interested stockholder for a period of three years following the date on which the stockholder became an interested stockholder, unless such transactions are approved by the board of directors. This provision could have the effect of discouraging, delaying or preventing someone from acquiring us or merging with us, whether or not it is desired by or beneficial to our stockholders. Any provision of our certificate of incorporation or bylaws or Delaware law that has the effect of delaying or deterring a change in control could limit the opportunity for our stockholders to receive a premium for their shares of our common stock and could also affect the price that some investors are willing to pay for our common stock.

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