Sierra to Present SRA737 Preliminary Clinical Data and Potential Next Steps at ASCO

- SRA737 Phase 1/2 Monotherapy and SRA737+LDG (Low Dose Gemcitabine) trials selected for poster presentations on June 1^st -
- Sierra to hold Analyst & Investor Event at 6:00 am CT on June 3^rd featuring distinguished oncologists Professor Johann de Bono and Dr. Rebecca Kristeleit -

VANCOUVER, May 15, 2019 /PRNewswire/ - Sierra Oncology, Inc. (SRRA), a clinical stage drug development company focused on advancing targeted therapeutics for the treatment of patients with significant unmet needs in hematology and oncology, today announced that it will report preliminary clinical data from its Phase 1/2 SRA737 monotherapy study and its Phase 1/2 study of SRA737 in combination with low dose gemcitabine (SRA737+LDG) in two posters being presented on June 1^st at the 2019 Annual Meeting of the American Society of Clinical Oncology (ASCO) in Chicago, Illinois.

In addition, the company will be hosting an Analyst and Investor Event on Monday, June 3^rd, to discuss these clinical findings and potential next steps in the development strategy for SRA737.

The event will feature presentations by two distinguished oncologists:

• 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, will discuss the critical role of Chk1 in tumor cell survival during replication stress (RS), as well as describe potential opportunities to combine SRA737 with other therapeutic modalities including PARP inhibitors and immunotherapy agents.
• Dr. Rebecca Kristeleit, Clinical Senior Lecturer and Honorary Consultant Medical Oncologist at University College London (UCL) Cancer Institute & UCLH Dept. of Oncology, a leading expert in gynecological malignancies, will discuss her clinical experience with SRA737+LDG, and potential development opportunities for this novel combination in the treatment of anogenital cancers.

"We look forward to presenting preliminary data for these first-in-human studies of SRA737 and SRA737+LDG at ASCO, and to discussing the potential opportunities for further advancement of our differentiated Chk1 inhibitor that these clinical data provide," said Dr. Nick Glover, President and CEO of Sierra Oncology. "The two studies have enrolled patients across a range of tumor indications including a variety of prospectively selected genetic contexts, allowing us to broadly survey the cancer landscape for activity signals in response to administration of SRA737 alone and in combination with non-cytotoxic low dose gemcitabine. These preliminary data have also enabled us to correlate clinical findings with tumor origin and genetic signature, ascertain whether the exogenous induction of replication stress via low dose gemcitabine can enhance SRA737's activity, and determine potential next steps in the development path for SRA737."

SRA737 Analyst & Investor Event
Date and Time: June 3^rd, 6:00 – 7:00 am CT
Location: History event room, Marriot Marquis Hotel, 2121 S Prairie Ave, Chicago, Illinois.

Event registration and webcast information are available through the Sierra Oncology website at www.sierraoncology.com. An archive of the presentation will be accessible after the event through the Sierra Oncology website.

ASCO 2019 Poster Presentations
Title: A first-in-human phase I/II trial of SRA737 (a Chk1 Inhibitor) in subjects with advanced cancer.
Abstract: 3094
Poster #: 86
Poster Session: Developmental Therapeutics and Tumor Biology (Nonimmuno)
Date and Time: Saturday, June 1, 2019, 8:00 – 11:00 am CT
Location: McCormick Place, Event room: Hall A, 2301 S King Dr, Chicago, Illinois

Title: A phase I/II first-in-human trial of oral SRA737 (a Chk1 inhibitor) given in combination with low-dose gemcitabine in subjects with advanced cancer.
Abstract: 3095
Poster #: 87
Poster Session: Developmental Therapeutics and Tumor Biology (Nonimmuno)
Date and Time: Saturday, June 1, 2019, 8:00 – 11:00 am CT
Location: McCormick Place, Event room: Hall A, 2301 S King Dr, Chicago, Illinois

The posters will be available on June 1, 2019 on the company's website at www.sierraoncology.com

About SRA737 and SRA737+LDG
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 DNA Damage Response (DDR). Tumors with high levels of replication stress become reliant on Chk1 to mitigate the potentially catastrophic consequences of excess genomic instability.

Intrinsic sources of replication stress can include genetic alterations in tumor suppressors, oncogenes or DNA Damage Repair genes. Tumors harboring defects in these gene classes are hypothesized to have higher levels of intrinsic replication stress due to dysregulated cell cycle control, increased proliferation demands and increased genomic instability. 

SRA737+LDG is a novel drug combination, where non-cytotoxic low dose gemcitabine (LDG) acts as a potent extrinsic inducer of replication stress that potentiates SRA737's anti-tumor activity.  Preclinical models have demonstrated that only subtherapeutic levels of gemcitabine are needed to potentiate SRA737's anti-tumor effect. 

Phase 1/2 clinical trials of SRA737 as monotherapy (NCT02797964) and in combination with low dose gemcitabine (NCT02797977) in multiple solid tumors (ovarian, prostate, non-small cell lung, squamous (head & neck, anal), colorectal, small cell lung, sarcoma, cervical, anogenital) are ongoing. Sierra has also prepared for a potential clinical study of SRA737 in combination with a PARP inhibitor.

Sierra Oncology retains the global commercialization rights to SRA737.

About Sierra Oncology
Sierra Oncology is a clinical stage drug development company advancing targeted therapeutics for the treatment of patients with unmet medical needs in hematology and oncology. Our lead drug candidate, momelotinib, is a potent, selective and orally-bioavailable JAK1, JAK2 and ACVR1 inhibitor that has been investigated in two completed Phase 3 trials for the treatment of myelofibrosis and has demonstrated a potentially differentiated therapeutic profile encompassing anemia-related benefits, as well as achieving substantive splenic volume reduction and constitutional symptom control.

Sierra Oncology is also advancing SRA737 and SRA141. 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 DNA Damage Response (DDR). SRA141 is a potent, selective, orally bioavailable small molecule inhibitor of Cell division cycle 7 kinase (Cdc7). 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, 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, product candidates may not demonstrate safety and efficacy or otherwise produce positive results, Sierra Oncology may experience delays in the preclinical and anticipated clinical development of its product candidates, 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.

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SOURCE Sierra Oncology