INVESTORS
Sierra Oncology Announces Late-Breaking Oral and Poster Presentations at AACR 2019 for SRA737 and SRA141 Preclinical Data

- Late-breaking oral presentation to report preclinical mechanistic and efficacy data for immunotherapy combined with SRA737 + LDG, its Chk1 inhibitor plus low dose gemcitabine (LDG), in small cell lung cancer models -
- Late-breaking abstract reporting preclinical efficacy for Cdc7 inhibitor, SRA141, selected for poster presentation -

VANCOUVER, Feb. 27, 2019 /CNW/ - Sierra Oncology, Inc. (Nasdaq: 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 an abstract reporting preclinical data for SRA737 + LDG, its Chk1 inhibitor plus low dose gemcitabine (LDG), in combination with immunotherapy, has been selected for a late-breaking oral presentation at the American Association of Cancer Research (AACR) Annual Meeting 2019, to be held in Atlanta, Georgia from March 29 to April 3.

In addition, a late-breaking abstract reporting preclinical data for Sierra's Cdc7 inhibitor, SRA141, has been selected for a poster presentation at AACR 2019.

"We previously reported that SRA737 activated the innate immune signaling STING pathway and demonstrated significant synergistic anti-tumor activity with immunotherapy in an immunotherapy-refractory small cell lung cancer (SCLC) model. SRA737 + LDG is a novel drug combination, where gemcitabine acts as a potent inducer of replication stress that potentiates SRA737's activity. These new studies reveal a striking immunomodulatory effect of SRA737 + LDG that results in some of the most profound synergistic activity with anti-PD-L1 therapy that we have observed in this model," said Dr. Lauren Byers, Associate Professor at the University of Texas MD Anderson Cancer Center, Houston, Texas. "We are excited by the potential clinical translatability of these findings and their possible broader impact on immune checkpoint blockade strategies."

"The selection of these preclinical studies for late-breaking oral and poster presentation at AACR 2019 reflects the robust and differentiated findings of this research conducted by our world-class collaborators.  Both programs, one investigating the combination of SRA737 + LDG with immunotherapy and the other evaluating our novel Cdc7 inhibitor SRA141, have generated compelling data highlighting potential additional clinical pathways for these pipeline assets," said Dr. Christian Hassig, Chief Scientific Officer, Sierra Oncology.  "The data for SRA141 reinforces Cdc7's fundamental role in cancer progression and its potential utility as a differentiated anti-cancer agent, providing further support for SRA141's optimal clinical development.  The dramatic enhancement of immunotherapy anti-tumor activity in combination with SRA737 + LDG provides a strong preclinical rationale for the potential of this replication stress targeting strategy to broaden the limited clinical efficacy of immunotherapy observed in certain cancers, such as SCLC."

SRA737 AACR Late-Breaking Oral Presentation:

Date/Time: Monday, April 1st from 3:00 to 5:00 pm ET.
Session: Minisymposium: Late-Breaking Research 2
Title: Combination treatment of the CHK1 inhibitor, SRA737, and low dose gemcitabine demonstrates profound synergy with anti-PD-L1 inducing durable tumor regressions and modulating the immune microenvironment in small cell lung cancer
Authors: Triparna Sen, Carminia M. Della Corte, Snezana Milutinovic, Lixia Diao, Robert J Cardnell, Ryan J. Hansen, Bryan Strouse, Michael P. Hedrick, Christian Hassig, Jing Wang, Lauren A Byers.
Location: Georgia World Congress Center, Room B404

SRA141 AACR Late-Breaking Poster:

Date/Time: Wednesday, April 3rd from 8:00 am to 12:00 pm ET.
Session: Late-Breaking Research: Molecular and Cellular Biology / Genetics 2
Title: CDC7 kinase inhibition by SRA141 induces a potentially novel caspase-dependent tumor cell apoptosis associated with altered DNA replication and cell cycle dynamics.
Authors: Veena Jagannathan, Snezana Milutinovic, Ryan J. Hansen, Bryan Strouse, Christian Hassig and Eric J. Brown.
Location: Georgia World Congress Center, Exhibit Hall B, Poster Section 41, Poster #5

The presentation and poster will be made available on the company's website at www.sierraoncology.com.

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 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). SRA737 is currently being investigated in two Phase 1/2 clinical trials primarily focused on patients with ovarian cancer: SRA737-01, a monotherapy study, and SRA737-02, a drug combination study evaluating SRA737 potentiated by low dose gemcitabine. Sierra has also prepared for a potential clinical study of SRA737 in combination with a PARP inhibitor. 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 timing, expectations regarding when trial data may be reported 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.

SOURCE Sierra Oncology

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