Sierra Oncology Granted US and EU Patents for Chk1 inhibitor SRA737

VANCOUVER, May 30, 2017

VANCOUVER, May 30, 2017 /PRNewswire/ - 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 it has been issued a selection patent for its Chk1 inhibitor, SRA737, from the U.S. Patent and Trademark Office. The patent explicitly covers SRA737 and extends its protection out to 2033 in the U.S., before any patent term extensions.

The company also reported that a similar European Patent (No. 2855448) was previously issued for SRA737 on February 8, 2017. SRA737 is currently being evaluated in two Phase 1 clinical trials.

"These issuances further build on our intellectual property position for SRA737 and establish a solid foundation for the potential future commercialization of this promising drug candidate," said Dr. Nick Glover, President and CEO of Sierra Oncology. "We anticipate generating additional intellectual property claims as we advance our DDR-focused research activities and our innovative genetics-driven clinical programs."

U.S. Patent No. 9,663,503 pertains to SRA737, pharmaceutical compositions comprising such compounds, and the use of such compounds and compositions, both in vitro and in vivo, to inhibit Chk1 kinase function, and in the treatment of diseases and conditions that are mediated by Chk1, including proliferative conditions such as cancer. The patent also covers the use of SRA737 in combination with other agents.

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:

• SRA737-01, a Monotherapy trial prospectively enrolling patients with tumors identified to have genetic aberrations hypothesized to confer sensitivity to Chk1 inhibition via synthetic lethality into five indication-specific cohorts: colorectal, ovarian, non-small cell lung, prostate, and head and neck cancers. In cancer cells, replication stress induced by oncogenes (e.g., MYC or RAS) or genetic mutations in DNA repair machinery (e.g., BRCA1 or FA) combined with loss of function in tumor suppressors (e.g., TP53 or ATM) results in persistent DNA damage and genomic instability leading to an increased dependency on Chk1 for survival. Targeted inhibition by SRA737 may therefore be synthetically lethal to these cancer cells and have utility as a monotherapy in a range of tumor indications.
  
  
• SRA737-02, a Chemotherapy Combination trial evaluating SRA737 in combination with low-dose gemcitabine in indication-specific cohorts of prospectively-selected, genetically-defined subjects with bladder or pancreatic cancer. Profound mechanistic potentiation has been reported when Chk1 inhibition is combined with DNA damaging cytotoxic agents or radiation. The widely-used chemotherapy gemcitabine is a strong exogenous inducer of replication stress and preclinical modeling demonstrates robust synergistic anti-tumor activity for SRA737 potentiated by gemcitabine.

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.