Sierra Oncology Launches Campaign Exploring Non-Dilutive Strategic Options to Support Development of its DDR Assets

- Corporate prioritization of portfolio to focus resources on advancement of momelotinib -
- Exploring non-dilutive options to support future continued development of SRA737 and SRA141 -

VANCOUVER, June 27, 2019 /PRNewswire/ - Sierra Oncology, Inc. (SRRA), a late-stage drug development company focused on advancing targeted therapeutics for the treatment of patients with significant unmet needs in hematology and oncology, today announced plans to prioritize its existing resources on the development of momelotinib, its differentiated Phase 3 drug candidate for the treatment of patients with myelofibrosis. Sierra also announced it has launched a campaign exploring non-dilutive strategic options to support the future continued development of its portfolio of potent and selective DDR (DNA Damage Response) assets, consisting of SRA737 (Chk1 inhibitor) and SRA141 (Cdc7 inhibitor).

"We recently reported compelling proof-of-concept clinical efficacy data for SRA737 at the 2019 ASCO Annual Meeting, demonstrating that this drug candidate has notable anti-cancer activity in multiple indications and a defined clinical path forward towards potential initial registration for the treatment of anogenital cancer, an indication with considerable unmet need. For SRA141, we have demonstrated a potentially novel mechanism of cytotoxicity and successfully completed the IND process with the FDA enabling the commencement of clinical trials," said Dr. Nick Glover, President and CEO of Sierra Oncology. "While we continue to advance the assets in our DDR portfolio and view them as promising oncology drug candidates that warrant further development, we are prioritizing our resources on our lead drug, momelotinib. To support the continued development of SRA737 and SRA141 in the future, we intend to seek non-dilutive strategic options."

About Sierra's DDR assets: SRA737 (targeting Chk1) and SRA141 (targeting Cdc7)
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. SRA737+LDG is a novel drug combination, where non-cytotoxic low dose gemcitabine (LDG) acts as a potent extrinsic inducer of replication stress.

At the 2019 ASCO Annual meeting, Sierra reported preliminary efficacy data for SRA737 including a 30% Overall Response Rate in patients with anogenital cancer treated with SRA737+LDG , an indication for which the second line metastatic setting represents a significant unmet medical need with no approved therapies and very poor life expectancy. Additionally, subjects whose tumors harbored FA/BRCA gene network mutations displayed favorable outcomes across multiple indications, with an Overall Response Rate of 25% and Disease Control Rate of 81%.

Sierra has conducted preclinical research demonstrating SRA737 synergy in combination with other DDR-targeted agents including poly ADP-ribose polymerase (PARP) inhibitors, as well as with immuno-oncology therapeutics. Sierra has an agreement with Janssen Research & Development, LLC (Janssen), under which Janssen has agreed to supply the PARP inhibitor niraparib, facilitating the potential initiation of a combination trial with SRA737 that Sierra has designed for the treatment of prostate cancer. Sierra reported preclinical data in a late-breaking poster presented at the AACR Annual Meeting 2019 demonstrating that SRA737+LDG activates innate immune signaling and establishes an anti-tumor immune microenvironment that profoundly synergizes with immune checkpoint inhibitors. Sierra has reported having management support from a major immuno-oncology company to potentially supply their leading immunotherapeutic agent to run a combination study with SRA737.

SRA141 is a potent, selective, orally bioavailable small molecule inhibitor of Cell division cycle 7 kinase (Cdc7). Sierra reported preclinical data in a late-breaking poster presented at the AACR Annual Meeting 2019 highlighting a possible novel mechanism of cytotoxicity for SRA141 that is distinct from other agents, in which SRA141 alters DNA replication dynamics and delays cell cycle progression, leading to apoptotic tumor cell death. This differentiated mechanism of action may support a unique spectrum of clinical opportunities for SRA141 as both monotherapy and in combination with pro-apoptotic and mitotic disrupting agents. Sierra has successfully completed the IND process with the U.S. Food and Drug Administration (FDA) for SRA141 and has designed a potential Phase 1/2 trial with this drug candidate.

Sierra Oncology retains the global commercialization rights to SRA737 and SRA141.

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.

Momelotinib, Sierra's lead drug candidate, is a potent, selective and orally-bioavailable JAK1, JAK2 & ACVR1 inhibitor with a differentiated therapeutic profile in myelofibrosis encompassing robust constitutional symptom improvements, a range of meaningful anemia benefits, including eliminating or reducing the need for frequent blood transfusions, and comparable spleen control to ruxolitinib. More than 1,200 subjects have received momelotinib since clinical studies began in 2009, including more than 800 subjects treated for myelofibrosis.

Sierra plans to launch the MOMENTUM Phase 3 clinical trial in Q4 2019 to support potential registration of the momelotinib on a global basis. The randomized double-blind trial is designed to enroll 180 myelofibrosis patients who are symptomatic, anemic and have been treated previously with a JAK inhibitor. Dr. Srdan Verstovsek, MD, PhD, Chief, Section for Myeloproliferative Neoplasms, Department of Leukemia, Division of Cancer Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas, has been named Chief Investigator of the MOMENTUM trial.

Momelotinib is wholly owned by Sierra Oncology and is covered by patents anticipated to provide potential exclusivity to 2040 in the U.S. The FDA has granted Fast Track designation to momelotinib for the treatment of patients with intermediate/high-risk myelofibrosis who have previously received a JAK inhibitor.

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, expected timing of the execution of, and expected results from, non-dilutive strategic options, expected timing of the initiation of MOMENTUM, 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

Related Links

https://www.sierraoncology.com/

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