UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

 

 

FORM 8-K

 

 

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): February 27, 2018

 

 

SIERRA ONCOLOGY, INC.

(Exact name of registrant as specified in its charter)

 

 

 

Delaware   001- 37490   20-0138994

(State or other jurisdiction

of incorporation)

 

(Commission

File Number)

 

(IRS Employer

Identification No.)

c/o 2150 – 885 West Georgia Street

Vancouver, British Columbia, Canada

  V6C 3E8
(Address of principal executive offices)   (Zip Code)

(604) 558-6536

(Registrant’s telephone number, including area code)

N/A

(Former name or former address, if changed since last report)

 

 

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

 

☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

 

☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

 

☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

 

☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company  ☒

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act.  ☒

 

 

 

Item 2.02. Results of Operations and Financial Condition.

On February 27, 2018, Sierra Oncology, Inc. (the “Company”) reported its financial results for the year ended December 31, 2017. A copy of the press release issued by the Company is furnished as Exhibit 99.1 to this report.

The information furnished with Item 2.02 of this report, including Exhibit 99.1, shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference into any other filing under the Exchange Act or under the Securities Act of 1933, as amended, except as expressly set forth by specific reference in such a filing.

 

Item 8.01. Other Events.

On February 27, 2018, the Company issued a press release reporting the expansion of its clinical development programs. The Company also issued a press release reporting that Janssen Research & Development, LLC will supply PARP inhibitor niraparib for the Company’s Phase 1b/2 combination trial with SRA737.

Copies of the press releases are filed as Exhibits 99.2 and 99.3 to this Current Report on Form 8-K.

 

Item 9.01. Financial Statements and Exhibits.

 

Exhibit

Number

  

Description

99.1    Press release dated February 27, 2018 (financial results).
99.2    Press release dated February 27, 2018 (program update).
99.3    Press release dated February 27, 2018 (PARPi supply).

 

2

SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

 

    SIERRA ONCOLOGY, INC.
Date: February 27, 2018     By:  

/s/ Sukhi Jagpal

      Sukhi Jagpal
      Chief Financial Officer

 

3

Exhibit 99.1

 

LOGO

Sierra Oncology Reports 2017 Year End Results

- Janssen supply agreement for ZEJULA® (niraparib) facilitates novel PARPi combination trial with SRA737 in prostate cancer -

- SRA737 clinical development program significantly expanded -

- SRA737 clinical studies expected to report preliminary data in the fourth quarter of 2018 -

Vancouver, British Columbia – February  27, 2018. Sierra Oncology, Inc. (Nasdaq: SRRA), a clinical stage drug development company focused on advancing next generation DNA Damage Response (DDR) therapeutics for the treatment of patients with cancer, today reported its financial and operational results for the year ended December 31, 2017.

“During 2017, we made substantial progress advancing our portfolio of promising next generation DDR therapeutics. In particular, emerging preclinical and clinical data continue to reinforce the fundamental biological role of Chk1 in regulating cancer-driven replication stress associated with genomic instability, a hallmark of cancer with potentially broad therapeutic relevance. Accordingly, during the year we significantly advanced and expanded the development program for our potential best-in-class Chk1 inhibitor, SRA737, which will now be evaluated across ten cancer indications in two ongoing Phase 1/2 trials, targeting aggregate enrollment of approximately 200 genetically-selected patients. We look forward to reporting preliminary data from these trials, expected in the fourth quarter of 2018,” said Dr. Nick Glover, President and CEO of Sierra Oncology. “We also announced, subsequent to the end of the year, the advancement of a promising third development opportunity for SRA737 with the signing of an agreement with Janssen to supply us with ZEJULA® (niraparib). This agreement facilitates the advancement of a novel Chk1i/PARPi combination trial in prostate cancer that we plan to initiate in the fourth quarter of 2018, which will be led by Professor Johann de Bono, Regius Professor of Cancer Research at The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust.

2017 Highlights :

 

  •   In January 2017, we relaunched as Sierra Oncology with a stated focus on developing oncology drugs targeting the DNA Damage Response (DDR) network.

 

  •   Also in January, we successfully transferred sponsorship of the two ongoing Phase 1/2 clinical trials for our lead DDR drug candidate, SRA737, from the Cancer Research UK Centre for Drug Development, enabling us to submit protocol amendments aimed at enhancing these studies to include cohort expansions of prospectively selected patients with tumors identified to have genetic aberrations hypothesized to confer sensitivity to Chk1 inhibition via synthetic lethality.

 

  •   In February, we raised net proceeds of US$27.4 million to further advance our programs.

 

  •   In April, our collaborator, the Institute of Cancer Research (ICR), London, UK, reported preclinical results for SRA737 in a poster at the American Association of Cancer Research (AACR) Annual Meeting, supporting our genetically-driven clinical development strategy for SRA737.

 

  •   In May, we were issued a patent providing SRA737 with protection in the United States to 2033, before any potential patent term extensions.

 

  •   In June, having received clearance for our protocol amendments, we presented these innovative SRA737 Phase 1 clinical designs in two Trials in Progress posters at the 2017 American Society of Clinical Oncology (ASCO) Annual Meeting. We concurrently reported encouraging initial progress from the two ongoing trials; SRA737 was well-tolerated and a maximum tolerated dose (MTD) had not yet been reached in the dose escalation phase of the monotherapy trial.

 

  •   In August, we established a DDR Advisory Committee composed of leading experts in DDR biology, chemistry and medicine. We also held two Key Opinion Leader (KOL) events, in September and October 2017, which featured members from our Advisory Committee who shared their insights on emerging DDR biology and the potential of Chk1 inhibition in oncology, providing further support for our programs.

  •   In October, we presented a poster at the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics, reporting on preclinical data demonstrating that sub-therapeutic, non-cytotoxic doses of gemcitabine induce replication stress and hence potentiate the anti-tumor activity of SRA737. These data support the design of our ongoing Phase 1/2 clinical trial which is specifically evaluating this combination.

 

  •   We appointed Dr. Andrew Allen to our Board of Directors, effective October 23, 2017. Dr. Allen is the co-founder of Gritstone Oncology and was the co-founder of Clovis Oncology (Nasdaq: CLVS).

Subsequent Events:

On February 27, 2018, we provided an update on the SRA737 and SRA141 development programs:

 

  •   For the SRA737 Monotherapy Phase 1/2 trial, we reported that the Dose Escalation Phase 1 portion of the study was in the final stages of optimizing the SRA737 dose regimen and the Cohort Expansion Phase 2 portion of the study was ongoing. The Cohort Expansion Phase 2 portion of the study was being expanded to include more patients, including a sixth indication ( CCNE1 -driven ovarian cancer), and would in aggregate target enrollment of 120 patients across six genetically-defined cohorts. We also reported that we plan to expand the number of sites recruiting patients into the trial from three active sites (as of the third quarter of 2017) to fifteen leading centers across the United Kingdom. The Cohort Expansion Phase 2 portion of the study is expected to report preliminary data in the fourth quarter of 2018.

 

  •   For the SRA737 Low-Dose Gemcitabine Phase 1/2 Combination trial, we reported that the Standard-Dose Triplet Combo Dose Escalation Phase 1 was complete and that the Low-Dose Gemcitabine Combo Dose Escalation Phase 1 had made significant progress. In addition, the Low-Dose Gemcitabine Combo Cohort Expansion Phase 2 was anticipated to commence in the second quarter of 2018 and would be expanded to target enrollment of 80 genetically-selected patients across four indications. An update on the study is expected to be reported in the fourth quarter of 2018.

 

  •   We reported signing a supply agreement with Janssen Research & Development, LLC where they will supply TESARO’s ZEJULA® (niraparib), an orally administered poly ADP-ribose polymerase (PARP) inhibitor, facilitating the initiation of a combination trial of niraparib with SRA737 in patients with prostate cancer in the fourth quarter of 2018. The trial is to be led by Professor Johann de Bono, Regius Professor of Cancer Research, Head of the Division of Clinical Studies and Professor in Experimental Cancer Medicine at The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust.

 

  •   We presented emerging evidence of biological synergy between immune checkpoint blockade and Chk1 inhibition. Sierra is currently designing a clinical study for this combination, which potentially could be submitted to regulatory authorities in the fourth quarter of 2018.

 

  •   We reported supportive preclinical research for SRA141 demonstrating noteworthy anti-cancer activity in two independent oncology models, generated in preparation for an Investigational New Drug (IND) filing expected in the second half of 2018.

2017 Financial Results (all amounts reported in U.S. currency)

Research and development expenses were $30.2 million for the year ended December 31, 2017, compared to $33.9 million for the year ended December 31, 2016. The decrease is primarily due to expenses incurred in 2016, including $9.0 million related to the SRA737 license agreement, a $0.9 million upfront payment for the exclusive license of SRA141, and a $2.3 million restructuring charge related to close-out expenses for PNT2258. These decreases were partially offset by increases of $4.6 million in third-party manufacturing costs, $2.6 million in research and other costs related to SRA737 and SRA141, and $1.0 million in clinical trial costs. Research and development expenses included non-cash stock-based compensation of $4.0 million and $3.6 million for the years ended December 31, 2017 and 2016, respectively.

General and administrative expenses were $12.5 million for the year ended December 31, 2017 compared to $14.2 million for the year ended December 31, 2016. The decrease is primarily due to a $1.1 million decrease in business development expenses and a $0.5 million decrease in restructuring costs as compared to 2016. General and administrative expenses included non-cash stock-based compensation of $1.9 million for both the year ended December 31, 2017 and the year ended December 31, 2016.

For the year ended December 31, 2017, Sierra incurred a net loss of $42.0 million compared to a net loss of $47.9 million for the year ended December 31, 2016.

Cash and cash equivalents totaled $100.3 million as of December 31, 2017, compared to $107.8 million as of September 30, 2017, and $109.0 million as of December 31, 2016. The company believes that its existing cash and cash equivalents will be sufficient to fund current operating plans through approximately mid-2019.

At December 31, 2017, there were 52,395,223 shares of common stock issued and outstanding, and stock options to purchase 7,470,601 shares of common stock issued and outstanding.

About Sierra Oncology

Sierra Oncology is a clinical stage drug development company advancing next generation DNA Damage Response (DDR) therapeutics for the treatment of patients with cancer. Our lead drug candidate, SRA737, is a potent, highly selective, orally bioavailable small molecule inhibitor of Checkpoint kinase 1 (Chk1), a key regulator of cell cycle progression and the DDR replication stress response. SRA737 is currently being investigated in two Phase 1/2 clinical trials in patients with advanced cancer: SRA737-01, a monotherapy study evaluating SRA737 in patients with tumors identified to have genetic aberrations hypothesized to confer sensitivity to Chk1 inhibition via synthetic lethality; and SRA737-02, a drug combination study evaluating SRA737 potentiated by low-dose gemcitabine. Sierra is also preparing clinical studies for SRA737 in combination with other agents where there is a strong biological rationale for synergy with Chk1 inhibition, such as immune oncology therapeutics and other DDR inhibitors including PARP inhibitors.

Sierra Oncology is also advancing SRA141, a potent, selective, orally bioavailable small molecule inhibitor of Cell division cycle 7 kinase (Cdc7) undergoing preclinical development. Cdc7 is a key regulator of DNA replication and is involved in the DDR network, making it a compelling emerging target for the potential treatment of a broad range of tumor types. For more information, please visit www.sierraoncology.com .

Cautionary Note on Forward-Looking Statements

This press release contains forward-looking statements within the meaning of the “safe harbor” provisions of the Private Securities Litigation Reform Act of 1995, including, but not limited to, statements regarding Sierra Oncology’s market and industry position, expectations from current data, anticipated clinical development activities, expectations regarding when trial data may be reported, use and adequacy of existing cash and cash equivalents, and potential benefits of Sierra Oncology’s product candidates. All statements other than statements of historical fact are statements that could be deemed forward-looking statements. These statements are based on management’s current expectations and beliefs and are subject to a number of risks, uncertainties and assumptions that could cause actual results to differ materially from those described in the forward-looking statements. Such forward-looking statements are subject to risks and uncertainties, including, among others, the risk that Sierra Oncology may be unable to successfully develop and commercialize product candidates, SRA737 and SRA141 are at early stages of development and may not demonstrate safety and efficacy or otherwise produce positive results, Sierra Oncology may experience delays in the preclinical and anticipated clinical development of SRA737 or SRA141, Sierra Oncology may be unable to acquire additional assets to build a pipeline of additional product candidates, Sierra Oncology’s third-party manufacturers may cause its supply of materials to become limited or interrupted or fail to be of satisfactory quantity or quality, Sierra Oncology’s cash resources may be insufficient to fund its current operating plans and it may be unable to raise additional capital when needed, Sierra Oncology may be unable to obtain and enforce intellectual property protection for its technologies and product candidates and the other factors described under the heading “Risk Factors” set forth in Sierra Oncology’s filings with the Securities and Exchange Commission from time to time. Sierra Oncology undertakes no obligation to update the forward-looking statements contained herein or to reflect events or circumstances occurring after the date hereof, other than as may be required by applicable law.

SIERRA ONCOLOGY, INC.

Condensed Consolidated Balance Sheets

(unaudited)

(in thousands)

 

     December 31,
2017 		    December 31,
2016 		 

ASSETS

    

CURRENT ASSETS:

    

Cash and cash equivalents

   $ 100,348     $ 109,007  

Prepaid expenses and other current assets

     1,377       1,343  
  

 

 

   

 

 

 

Total current assets

     101,725       110,350  

Property and equipment, net

     154       400  

Other assets

     319       223  
  

 

 

   

 

 

 

TOTAL ASSETS

   $ 102,198     $ 110,973  
  

 

 

   

 

 

 

LIABILITIES AND STOCKHOLDERS’ EQUITY

    

CURRENT LIABILITIES:

    

Accrued liabilities

   $ 6,133     $ 5,121  

Accounts payable

     1,339       2,604  
  

 

 

   

 

 

 

Total current liabilities

     7,472       7,725  
  

 

 

   

 

 

 

TOTAL LIABILITIES

     7,472       7,725  
  

 

 

   

 

 

 

STOCKHOLDERS’ EQUITY:

    

Common stock

     52       30  

Additional paid-in capital

     718,751       685,272  

Accumulated deficit

     (624,077 )      (582,054 ) 
  

 

 

   

 

 

 

TOTAL STOCKHOLDERS’ EQUITY

     94,726       103,248  
  

 

 

   

 

 

 

TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY

   $ 102,198     $ 110,973  
  

 

 

   

 

 

 

SIERRA ONCOLOGY, INC.

Condensed Consolidated Statements of Operations

(unaudited)

(in thousands, except share and per share data)

 

     Three Months Ended
December 31, 		    Year Ended
December 31, 		 
     2017     2016     2017     2016  

Operating expenses:

        

Research and development

   $ 7,550     $ 5,821     $ 30,157     $ 33,895  

General and administrative

     3,255       3,412       12,462       14,180  
  

 

 

   

 

 

   

 

 

   

 

 

 

Total operating expenses

     10,805       9,233       42,619       48,075  
  

 

 

   

 

 

   

 

 

   

 

 

 

Loss from operations

     (10,805 )      (9,233 )      (42,619 )      (48,075 ) 

Other income

     254       92       760       351  
  

 

 

   

 

 

   

 

 

   

 

 

 

Loss before provision for income taxes

     (10,551 )      (9,141 )      (41,859 )      (47,724 ) 

Provision for income taxes

     48       107       156       143  
  

 

 

   

 

 

   

 

 

   

 

 

 

Net loss

   $ (10,599 )    $ (9,248 )    $ (42,015 )    $ (47,867 ) 
  

 

 

   

 

 

   

 

 

   

 

 

 

Net loss per share, basic and diluted

   $ (0.20 )    $ (0.30 )    $ (0.84 )    $ (1.58 ) 
  

 

 

   

 

 

   

 

 

   

 

 

 

Weighted-average shares used in computing net loss, basic and diluted

     52,330,334       30,365,713       49,899,299       30,240,258  
  

 

 

   

 

 

   

 

 

   

 

 

 

Contact:

James Smith

Vice President of Corporate Affairs

Sierra Oncology

604.558.6536

investors@sierraoncology.com

Exhibit 99.2

 

LOGO

Sierra Oncology Significantly Expands Clinical Development Program

– Ongoing SRA737 clinical studies expanded to target aggregate enrollment of 200 patients across ten cancer indications –

– Adding new SRA737 monotherapy cohort for CCNE1 -driven ovarian cancer –

– SRA141 IND submission planned in H2 2018 –

Vancouver, British Columbia – February  27, 2018. Sierra Oncology, Inc. (Nasdaq: SRRA), a clinical stage drug development company focused on advancing next generation DNA Damage Response (DDR) therapeutics for the treatment of patients with cancer, today reported significant progress in the advancement of its strategic pipeline of drug assets.

The company announced noteworthy progress in the Dose Escalation Phase 1 portions for both of its ongoing Phase 1/2 clinical trials evaluating its potential best-in-class Chk1 inhibitor, SRA737. The company announced expansion of the efficacy-oriented Phase 2 portions of both trials, which will now target aggregate enrollment of approximately 200 patients across ten cancer indications. The company also announced it is planning to initiate a Phase 1b/2 clinical trial in the fourth quarter of 2018 that will evaluate SRA737 in combination with ZEJULA ® (niraparib) for the treatment of metastatic castration-resistant prostate cancer (mCRPC).

In addition, the company announced it is planning to submit an Investigational New Drug (IND) for its Cdc7 inhibitor, SRA141, in the second half of 2018 in order to initiate a Phase 1/2 clinical trial, focused initially on the treatment of colorectal cancer.

Sierra is hosting a Program Update event today at 10:00 am ET in New York where it will provide an update on the progress of its portfolio of assets, with specific reference to its clinical development program for SRA737. The Sierra management team will be joined by Dr. Udai Banerji, Chief Investigator for the company’s ongoing SRA737 Phase 1/2 clinical trials, and Dr. Alan D’Andrea, a member of Sierra’s DDR Advisory Committee. A live webcast of the event will be available at www.sierraoncology.com.

“We are pleased to report encouraging progress in the advancement of both of our next generation DDR assets. In particular, SRA737 has demonstrated an emerging preclinical and clinical profile which appears competitively differentiated in comparison to other clinical stage Chk1 inhibitors, which gives us confidence to significantly expand its development program both as monotherapy and in a variety of combination settings,” said Dr. Nick Glover, President and CEO of Sierra Oncology. “In support of this expansion, we are adding further clinical centers in 2018, with the goal of reporting preliminary clinical data in the fourth quarter of 2018.”

“The safety profile for SRA737 has been highly promising, both as monotherapy and in combination with low dose gemcitabine. These observations are entirely consistent with the asset’s mechanism-of-action and preclinical toxicology data, supporting a broad potential therapeutic window for SRA737,” Dr. Barbara Klencke, Chief Development Officer, Sierra Oncology. “The Phase 2 efficacy-oriented portion of the monotherapy trial is also underway and focuses on cancers that are driven by genetic mutations that result in high replication stress, which have been associated with synthetic lethality to Chk1 inhibition.”

“Given our continued understanding of Chk1 biology, we are also adding a CCNE1 -driven ovarian cancer cohort to the monotherapy study,” added Dr. Mark Kowalski, Chief Medical Officer, Sierra Oncology. “Women with tumors harboring this genetic profile have limited therapeutic options; they typically become resistant to platinum-based chemotherapy and do not commonly harbor mutations in BRCA1/2 genes. However, given the key role of CCNE1 in driving replication stress, SRA737 may be effective in these tumor types. We are encouraged by preclinical data we have generated that reinforce this potential utility.”

SRA737-01 Phase 1/2 Monotherapy Trial: Trial Update and Expansion Plans

This trial consists of two phases, a safety-oriented Dose Escalation Phase 1 in unselected ‘all-comer’ patients and an efficacy-oriented Cohort Expansion Phase 2 in patients with genetically-defined tumors that harbor genomic alterations linked to increased replication stress and hypothesized to be more sensitive to Chk1 inhibition. The company will provide an update on the Dose Escalation Phase 1 portion today.

 

  •   Dose Escalation has proceeded through multiple dose levels and SRA737 has been well-tolerated from 20 mg QD to 1000 mg QD as monotherapy.

 

  •   The majority of reported adverse events (AEs) have been Grade 1 or Grade 2 in severity.

 

  •   Most commonly observed AEs ( ³ 20%; all reported causalities) were fatigue and GI events (diarrhea, nausea, vomiting).

 

  •   Grade 3 adverse events have included neutropenia (2 patients), nausea (2 patients), and diarrhea (1 patient).

 

  •   Serious Adverse Events (at least possibly related by Investigator assessment) included Grade 3 neutropenia (probably related; one patient) and Grade 3 heart failure/cardiomyopathy (possibly related) in a single patient with rapid disease progression.

 

  •   Two Dose Limiting Toxicities (DLTs) were reported at 1300 mg QD (inability to receive 75% of the planned SRA737 dose due to GI intolerability).

 

  •   No evidence of emergent or cumulative toxicity and/or declining tolerability was observed with up to 8 cycles of drug administered, supportive of potential for extended dosing.

 

  •   Dose escalation is now complete; 1000 mg QD & 500 mg BID cohorts are currently being compared in order to optimize the SRA737 dose regimen.

The Cohort Expansion Phase 2 portion of the trial is enrolling genetically-defined patients into indication specific cohorts, including advanced or metastatic:

 

  •   castration-resistant prostate cancer (mCRPC);

 

  •   high grade serous ovarian cancer (HGSOC);

 

  •   non-small cell lung cancer (NSCLC);

 

  •   head and neck squamous cell carcinoma (HNSCC) or squamous cell carcinoma of the anus (SCCA); and

 

  •   colorectal cancer (mCRC).

The company announced today the addition of a sixth indication specific cohort, CCNE1 -driven HGSOC. During the Program Update, the company will present preclinical data demonstrating that SRA737 has significant anti-tumor activity and a profound survival benefit in CCNE1 -driven HGSOC preclinical models.

Sierra is also expanding the number of sites recruiting patients into the trial from three active sites (as of the third quarter of 2017) to a planned fifteen active sites at leading centers across the

United Kingdom, to support its increased enrollment to 20 patients in each of the six genetically-defined cohorts. In total, 120 patients are expected to be enrolled into the Phase 2 portion of the trial. The company reported that 20 patients had been enrolled into this portion of the study to date and that enrollment was in line with the anticipated prevalence of the gene mutations targeted. The Cohort Expansion Phase 2 portion of the study is expected to report preliminary clinical data in the fourth quarter of 2018.

SRA737-02 Phase 1/2 Low Dose Gemcitabine Combination Trial: Trial Update and Expansion Plans

This clinical trial consists of three phases:

 

1. A Standard-Dose Triplet Combo Dose Escalation Phase 1 evaluating a combination of SRA737 with standard-dose gemcitabine and cisplatin in patients with solid tumors.

The company reported that this phase has concluded.

 

2. A Low Dose Gemcitabine (LDG) Combo Dose Escalation Phase 1 evaluating safety in ‘all-comer’ non-selected patients, where cohorts of 3 to 6 patients are being administered escalating doses of SRA737 on an intermittent schedule in addition to low dose gemcitabine (5-10% of the standard gemcitabine dose) until the combination maximum tolerated dose (MTD) is reached.

The company reported that significant progress has been made in the LDG Combo Dose Escalation Phase 1, and the combination regimen has been very well-tolerated.

 

  •   The majority of reported AEs have been Grade 1 or Grade 2 in severity.

 

  •   Most commonly observed AEs ( ³ 20%; all reported causalities) were diarrhea, anemia, thrombocytopenia, fatigue, influenza-like illness, nausea, neutropenia and vomiting.

 

  •   Only one Grade 3 treatment related AE (neutropenia) was observed, at 40 mg SRA737/300 mg/m 2 gemcitabine.

 

  •   Related SAEs included a Grade 1 fever (possibly related) and a Grade 2 DVT (possibly related).

 

  •   No evidence of emergent or cumulative toxicity and/or declining tolerability was observed with up to 5 cycles of drug administered, supportive of potential for extended dosing.

 

  •   No DLTs have been reported in any LDG dose escalation cohort and dose escalation continues.

 

3. A Low Dose Gemcitabine Combo Cohort Expansion Phase 2, that will explore the preliminary efficacy of SRA737 plus low-dose gemcitabine in prospectively enrolled genetically-defined patients with tumors that harbor genomic alterations hypothesized to confer sensitivity to Chk1 inhibition via synthetic lethality.

The company reported that this phase is anticipated to commence in the second quarter of 2018 and has been expanded to target enrollment of 80 genetically-selected patients across four indications, including advanced or metastatic:

 

  •   urothelial carcinoma;

 

  •   small cell lung cancer (SCLC);

 

  •   soft tissue sarcoma;

 

  •   cervical/anogenital cancer.

An update on the study is expected to be provided in the fourth quarter of 2018.

SRA737 PARPi Combination Program Initiation and Supply Agreement

The company also announced execution of a supply agreement with Janssen Research & Development, LLC for the supply of TESARO’s ZEJULA ® (niraparib), an orally administered poly ADP-ribose polymerase (PARP) inhibitor, facilitating the initiation of a combination trial of SRA737 with niraparib in patients with prostate cancer, expected in the fourth quarter of 2018.

The trial is to be led by Professor Johann de Bono, Regius Professor of Cancer Research, Head of the Division of Clinical Studies and Professor in Experimental Cancer Medicine at The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust.

During the Program Update today, the company will present preclinical data supporting SRA737’s synergistic activity in combination with PARPi in a model of PARPi acquired resistance. Additional preclinical data supporting this combination will be presented at the American Association of Cancer Research (AACR) Annual Meeting 2018.

SRA737 Combination with Immuno-Oncology

During the Program Update today, the company will also present preclinical data providing evidence of biological synergy between SRA737 and immune checkpoint blockade. Sierra is currently designing a clinical study for this combination, which potentially could be submitted to regulatory authorities in the fourth quarter of 2018.

SRA141 Program Update

The company continues to advance SRA141, its potent, selective, orally bioavailable small molecule inhibitor of Cell division cycle 7 kinase (Cdc7), an emerging DDR target with exciting potential in cancer. During the Program Update today, the company will present supportive preclinical research for SRA141 demonstrating noteworthy anti-cancer activity in oncology models, generated in preparation for an IND submission expected in the second half of 2018, with an initial clinical focus on the treatment of colorectal cancer.

About Sierra Oncology

Sierra Oncology is a clinical stage drug development company advancing next generation DNA Damage Response (DDR) therapeutics for the treatment of patients with cancer. Our lead drug candidate, SRA737, is a potent, highly selective, orally bioavailable small molecule inhibitor of Checkpoint kinase 1 (Chk1), a key regulator of cell cycle progression and the DDR Replication Stress response. SRA737 is currently being investigated in two Phase 1/2 clinical trials in patients with advanced cancer: SRA737-01, a monotherapy study evaluating SRA737 in patients with tumors identified to have genetic aberrations hypothesized to confer sensitivity to Chk1 inhibition via synthetic lethality; and SRA737-02, a drug combination study evaluating SRA737 potentiated by low-dose gemcitabine. Sierra is also preparing for potential clinical studies of SRA737 in combination with other agents where there is a strong biological rationale for synergy with Chk1 inhibition, such as immune oncology therapeutics and other DDR inhibitors including PARP inhibitors.

Sierra Oncology is also advancing SRA141, a potent, selective, orally bioavailable small molecule inhibitor of Cell division cycle 7 kinase (Cdc7) undergoing preclinical development. Cdc7 is a key regulator of DNA replication and is involved in the DDR network, making it a compelling emerging target for the potential treatment of a broad range of tumor types. For more information, please visit www.sierraoncology.com .

Cautionary Note on Forward-Looking Statements

This press release contains forward-looking statements within the meaning of the “safe harbor” provisions of the Private Securities Litigation Reform Act of 1995, including, but not limited to, statements regarding Sierra Oncology’s market and industry position, expectations from current data, anticipated clinical development and potential benefits of Sierra Oncology’s product

candidates. All statements other than statements of historical fact are statements that could be deemed forward-looking statements. These statements are based on management’s current expectations and beliefs and are subject to a number of risks, uncertainties and assumptions that could cause actual results to differ materially from those described in the forward-looking statements. Such forward-looking statements are subject to risks and uncertainties, including, among others, the risk that Sierra Oncology may be unable to successfully develop and commercialize product candidates, SRA737 and SRA141 are at early stages of development and may not demonstrate safety and efficacy or otherwise produce positive results, Sierra Oncology may experience delays in the preclinical and anticipated clinical development of SRA737 or SRA141, Sierra Oncology may be unable to acquire additional assets to build a pipeline of additional product candidates, Sierra Oncology’s third-party manufacturers may cause its supply of materials to become limited or interrupted or fail to be of satisfactory quantity or quality, Sierra Oncology’s cash resources may be insufficient to fund its current operating plans and it may be unable to raise additional capital when needed, Sierra Oncology may be unable to obtain and enforce intellectual property protection for its technologies and product candidates and the other factors described under the heading “Risk Factors” set forth in Sierra Oncology’s filings with the Securities and Exchange Commission from time to time. Sierra Oncology undertakes no obligation to update the forward-looking statements contained herein or to reflect events or circumstances occurring after the date hereof, other than as may be required by applicable law.

Contact:

James Smith

Vice President, Corporate Affairs

Sierra Oncology, Inc.

604.558.6536

investors@sierraoncology.com

Exhibit 99.3

 

LOGO

Sierra Oncology and Janssen Sign Supply Agreement for Prostate Cancer Study

- Janssen to supply PARP inhibitor niraparib for Sierra’s Phase 1b/2 combination trial with Chk1 inhibitor SRA737 -

Vancouver – February  27 , 201 8 . Sierra Oncology, Inc. (Nasdaq: SRRA), a clinical stage drug development company focused on advancing next generation DNA Damage Response (DDR) therapeutics for the treatment of patients with cancer, today announced the signing of a clinical supply agreement with Janssen Research & Development, LLC. (Janssen) for access to TESARO’s ZEJULA ® (niraparib), an orally administered poly (ADP-ribose) polymerase (PARP) inhibitor undergoing clinical development by Janssen for patients with prostate cancer. Sierra intends to evaluate its Chk1 inhibitor, SRA737, in combination with niraparib in patients with metastatic castration-resistant prostate cancer (mCRPC). The scientific rationale for the combination was supported by translational research conducted at The Institute of Cancer Research, London.

Professor Johann de Bono, Regius Professor of Cancer Research at The Institute of Cancer Research, London, and Consultant Medical Oncologist at The Royal Marsden NHS Foundation Trust, will be the Chief Investigator of the new study. He noted: “I look forward to supporting Sierra’s investigation of this combination. Research has demonstrated the potential benefit of PARP inhibitor therapy in prostate cancer patients with defects in HRR, and clinical trials are under way evaluating niraparib in these patients. However, the combination of Chk1 inhibition with PARP inhibition potentially may expand the application of niraparib to patients with HRR proficient tumors or re-sensitize patients who have developed PARP inhibitor resistance.”

“Preclinical studies have demonstrated synergy between PARP inhibitors and SRA737, including in contexts where PARP inhibitors have minimal activity such as HRR proficient and PARP inhibitor resistant settings,” added Dr. Nick Glover, President and CEO of Sierra Oncology. “PARP inhibitors impede the repair of single-strand DNA breaks, resulting in stalled DNA replication forks and double strand breaks that make the cell highly reliant on HRR, which is regulated by Chk1. The combined inhibition of both pathways is the basis for Sierra’s drug combination strategy of SRA737 with niraparib.”

“This supply agreement with Janssen is significant strategically in the continued advancement of SRA737 as it enables the exploration of a novel and independent development path for our Chk1 inhibitor, supported by both a promising scientific and a compelling commercial rationale,” added Dr. Angie You, Chief Business & Strategy Officer and Head of Commercial at Sierra.

Sierra plans to conduct an open-label, multicenter Phase 1b/2 dose-ranging study to assess the safety, tolerability, pharmacokinetics, and preliminary antitumor activity of SRA737 in combination with niraparib in patients with mCRPC. The study is intended to determine the maximum tolerated dose and schedule of SRA737 in combination with niraparib and to propose a recommended Phase 2 dose (RP2D) and schedule of the combination. Data will be analyzed

to examine specific hypotheses regarding the relationship between clinical response and alterations in genes regulating cell cycle progression and DNA damage response.

Janssen will provide Sierra with niraparib, while Sierra will conduct and control the study, which is anticipated to commence in the fourth quarter of 2018. Preclinical studies evaluating the combination of SRA737 and niraparib are ongoing.

About Sierra’s Chk1 inhibitor, SRA737

SRA737, is a potent, highly selective, orally bioavailable small molecule inhibitor of Checkpoint kinase 1 (Chk1), a key regulator of cell cycle progression and the DDR Replication Stress response. SRA737 is currently being investigated in two Phase 1/2 clinical trials in patients with advanced cancer: SRA737-01, a monotherapy study evaluating SRA737 in patients with tumors identified to have genetic aberrations hypothesized to confer sensitivity to Chk1 inhibition via synthetic lethality; and SRA737-02, a drug combination study evaluating SRA737 potentiated by low-dose gemcitabine. Sierra is also preparing for potential clinical studies of SRA737 in combination with other agents where there is a strong biological rationale for synergy with Chk1 inhibition, such as immune oncology therapeutics and other DDR inhibitors including PARP inhibitors.

About niraparib

Janssen Biotech, Inc. maintains a worldwide collaboration, license and supply agreement with TESARO, Inc., for exclusive rights to the investigational compound niraparib in prostate cancer for all geographies except Japan. Janssen is conducting a Phase 2 study (NCT02854436) of niraparib in patients with mCRPC who have DNA-repair anomalies and a Phase 1 study (NCT02924766) of niraparib in combination with an androgen receptor-targeted therapy in mCRPC.

Niraparib (ZEJULA) was approved by the Food and Drug Administration (FDA) on March 27, 2017 and is marketed by TESARO in the United States and Europe. ZEJULA is an oral, once-daily poly (ADP-ribose) polymerase (PARP) 1/2 inhibitor that is indicated in the U.S. for the maintenance treatment of adult patients with recurrent epithelial ovarian, fallopian tube, or primary peritoneal cancer who are in a complete or partial response to platinum-based chemotherapy. The National Comprehensive Cancer Network (NCCN) added ZEJULA to the NCCN Clinical Practice Guidelines in Oncology Ovarian Cancer version 1.2017—April 12, 2017—as maintenance therapy for patients with platinum-sensitive disease who are in partial or complete response after completion of two or more lines of platinum-based chemotherapy. In preclinical studies, ZEJULA concentrates in the tumor relative to plasma, delivering greater than 90% durable inhibition of PARP 1/2 and a persistent antitumor effect.

About Sierra Oncology

Sierra Oncology is a clinical stage drug development company advancing next generation DNA Damage Response (DDR) therapeutics for the treatment of patients with cancer. Our lead drug candidate, SRA737, is a potent, highly selective, orally bioavailable small molecule inhibitor of Checkpoint kinase 1 (Chk1), currently being investigated in two Phase 1/2 clinical trials in patients with advanced cancer. Sierra Oncology is also advancing SRA141, a potent, selective, orally bioavailable small molecule inhibitor of Cell division cycle 7 kinase (Cdc7) undergoing preclinical development. Cdc7 is a key regulator of DNA replication and is involved in the DDR network, making it a compelling emerging target for the potential treatment of a broad range of tumor types. For more information, please visit www.sierraoncology.com .

Cautionary Note on Forward-Looking Statements

This press release contains forward-looking statements within the meaning of the “safe harbor” provisions of the Private Securities Litigation Reform Act of 1995, including, but not limited to, statements regarding Sierra Oncology’s expectations from current data, anticipated clinical

development activities and timelines, and potential benefits of Sierra Oncology’s product candidates. All statements other than statements of historical fact are statements that could be deemed forward-looking statements. These statements are based on management’s current expectations and beliefs and are subject to a number of risks, uncertainties and assumptions that could cause actual results to differ materially from those described in the forward-looking statements. Such forward-looking statements are subject to risks and uncertainties, including, among others, the risk that Sierra Oncology may be unable to successfully develop and commercialize product candidates, SRA737 and SRA141 are at early stages of development and may not demonstrate safety and efficacy or otherwise produce positive results, Sierra Oncology may experience delays in the preclinical and anticipated clinical development of SRA737 or SRA141, Sierra Oncology may be unable to acquire additional assets to build a pipeline of additional product candidates, Sierra Oncology’s third-party manufacturers may cause its supply of materials to become limited or interrupted or fail to be of satisfactory quantity or quality, Sierra Oncology’s cash resources may be insufficient to fund its current operating plans and it may be unable to raise additional capital when needed, Sierra Oncology may be unable to obtain and enforce intellectual property protection for its technologies and product candidates and the other factors described under the heading “Risk Factors” set forth in Sierra Oncology’s filings with the Securities and Exchange Commission from time to time. Sierra Oncology undertakes no obligation to update the forward-looking statements contained herein or to reflect events or circumstances occurring after the date hereof, other than as may be required by applicable law.

Contact:

James Smith

Vice President of Corporate Affairs

Sierra Oncology

604.558.6536

investors@sierraoncology.com