INVESTORS
Sierra Oncology to Report Chk1 Inhibitor SRA737 Preclinical Data at AACR-NCI-EORTC 2017

- Chk1 inhibitor SRA737 demonstrates chemical synthetic lethality with replication stress-inducing agents, including potentiation by novel low-dose gemcitabine combination, in preclinical models of cancer -

VANCOUVER, Oct. 16, 2017 /CNW/ - 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 that it will report preclinical data supporting the clinical development strategy for its Chk1 inhibitor, SRA737, in a poster to be presented at the upcoming AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics, being held from October 26 - 30, 2017 in Philadelphia, Pennsylvania. SRA737 is currently being investigated in two Phase 1 clinical trials in patients with advanced cancers; as a monotherapy, and in combination with low-dose gemcitabine.

Title: The Chk1 inhibitor, SRA737, demonstrates chemical synthetic lethality with replication stress-inducing agents, including novel low-dose gemcitabine, in preclinical models of cancer.

Poster #181; Abstract #B181:
Session: Poster Session B; Therapeutic Agents: Small-Molecule Kinase Inhibitors
Date and Time: Sunday, October 29, 2017, 12:30 PM4:00 PM
Location: Hall E, Pennsylvania Convention Center

The Poster will be available October 29, 2017 on the company's website at www.sierraoncology.com.

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 important cell cycle checkpoints and central mediator of the DDR network. SRA737 is currently being investigated in two Phase 1 clinical trials in patients with advanced cancer: a monotherapy study evaluating SRA737 in cancer patients with tumors identified to have genetic aberrations hypothesized to confer sensitivity to Chk1 inhibition via synthetic lethality, and a study evaluating the combination of 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 immuno-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.

SOURCE Sierra Oncology

For further information: James Smith, Vice President of Corporate Affairs, Sierra Oncology, 604.558.6536, investors@sierraoncology.com