Our lead drug candidate, momelotinib, is a potent, selective and orally-bioavailable JAK1, JAK2 & ACVR1 inhibitor with a differentiated therapeutic profile in myelofibrosis encompassing a range of meaningful anemia benefits, including eliminating or reducing the need for frequent blood transfusions, as well as achieving substantive spleen and constitutional symptom control. Momelotinib has been investigated in two completed Phase 3 trials for the treatment of myelofibrosis demonstrating robust clinical activity. More than 1,200 subjects have received momelotinib since clinical studies began in 2009.
Sierra Oncology wholly owns momelotinib. We are also advancing SRA737 and SRA141. SRA737, is a potent, highly selective, orally bioavailable small molecule inhibitor of Checkpoint kinase 1 (Chk1). Chk1 is a key regulator of cell cycle progression and the DDR replication response. In cancer cells, intrinsic replication stress (RS) 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. Replication stress can also be induced by certain exogeneous factors, such as the use of low dose gemcitabine (LDG). In general, 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 immuno-oncology agents, 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.
We are pursuing an innovative development plan for SRA737, which is currently being evaluated in two Phase 1/2 clinical trials in patients with advanced cancer. SRA737-01 is intended to evaluate SRA737’s potential to induce synthetic lethality as monotherapy, while SRA737-02 is intended to evaluate the combination of SRA737 potentiated by subtherapeutic, LDG. Concurrently, we are conducting preclinical research evaluating SRA737 in combination with other DDR-targeted agents, including poly ADP ribose polymerase (PARP) inhibitors, as well as with immuno-oncology therapeutics, that may guide a potential next wave of clinical development for our asset, possibly further broadening its therapeutic utility.
SRA141, 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 potential treatment across a broad range of tumor types. An Investigational New Drug Application (IND) submission to the U.S. Food and Drug Administration (FDA) has been completed in order to commence clinical trials with this drug candidate.
Sierra Oncology retains the global commercialization rights to both SRA737 and SRA141.