On November 15, 2018 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 reported preclinical data for its novel oral Chk1 inhibitor, SRA737, in a poster presented at the 30th EORTC-NCI-AACR (Free EORTC-NCI-AACR Whitepaper) Symposium held in Dublin, Ireland (Press release, Sierra Oncology, NOV 15, 2018, View Source [SID1234531379]).
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"Oncogene-driven high-grade serous ovarian cancers (HGSOC) with CCNE1 (gene encoding cyclin E) and MYCN pathway activation exhibit defective cell cycle checkpoint control and replicative stress. The DNA damage response effector kinase, Chk1, modulates the cellular response to replicative stress and has been shown to be upregulated in these subtypes of HGSOC," said Dr. Clare Scott, Professor at The Walter and Eliza Hall Institute of Medical Research, Parkville, Australia. "Our pre-clinical results show that the Chk1 inhibitor SRA737 has impressive efficacy in our most aggressive models of ovarian cancer."
As detailed in the poster, the efficacy of single agent SRA737 was explored in two cyclin E overexpressing HGSOC patient-derived xenografts (PDX), and also compared to olaparib, a PARP inhibitor recently approved for HGSOC. Both PDX models had pronounced amplification of CCNE1; one also harbored a MYCN amplification. Both PDX models were insensitive to standard platinum-based therapy and did not harbor BRCA1/2 or related gene mutations. Treatment with SRA737 resulted in significant and differentiated anti-cancer activity, including dose dependent tumor regression. As anticipated, the PARP inhibitor olaparib was inactive.
"Sierra’s ongoing SRA737-01 monotherapy and SRA737-02 low dose gemcitabine combination studies were recently prioritized for CCNE1-enriched HGSOC, a promising potential indication for Chk1 inhibition," stated Dr. Barbara Klencke, Chief Development Officer, Sierra Oncology. "We look forward to reporting clinical data from these studies in the first half of 2019."
The poster will be presented on Thursday, November 15th from 10:00 am – 5:30 pm (GMT).
Title: SRA737, a novel Chk1 inhibitor, shows efficacy in CCNE1-amplified and MYCN-overexpressing high-grade serous ovarian cancer patient-derived xenograft models
Authors: G.Y. Ho, H. Barker, C. Vanderberg, O. Kondrashova, E. Kyran, E. Lieschke, O. McNally, A. Hamilton, V. Heong, R. Hansen, S. Milutinovic, B. Strouse, M. Hedrick, C. Hassig, D. Bowtell, W. Matthew, C. Scott
About SRA737
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). In cancer cells, intrinsic replication stress is induced by factors such as oncogenes (e.g., CCNE1 or MYC), genetic mutations in DNA repair machinery (e.g., BRCA1 or FANCA), genetic mutations leading to a dysregulated cell cycle (e.g., TP53 or RAD50) or other genomic alterations. This replication stress results in persistent DNA damage and genomic instability leading to an increased dependency on Chk1 for survival. Targeted inhibition of Chk1 by SRA737 may therefore be synthetically lethal to cancer cells with elevated intrinsic replication stress and have utility as a monotherapy in a range of tumor indications. The combination of SRA737 with other modalities, such as other agents that target the DDR network and certain chemotherapeutics, may also provide synergistic anti-tumor activity via a variety of potential biological mechanisms. Importantly, the oral bioavailability of SRA737 may afford greater dosing flexibility for both monotherapy and combination therapy settings than is possible with intravenously administered agents.
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