Sierra Oncology to Report Clinical Data at ASH 2018 from Translational Biology Study of Momelotinib in Transfusion Dependent Patients

– Biomarker data obtained from 41 transfusion dependent patients support ACVR1 mechanism of action for momelotinib's anemia benefit in myelofibrosis –

– 34% of patients achieved RBC transfusion-independence ≥12 weeks at any time on study –

– 39% of patients achieved ≥8 weeks of RBC transfusion independence –

VANCOUVER, Nov. 1, 2018 /PRNewswire/ - 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 that clinical data from a translational biology study of momelotinib in 41 transfusion dependent patients with myelofibrosis (MF) will be reported in a poster at ASH 2018. The impact of momelotinib on serum hepcidin, along with markers of iron storage and availability, erythropoiesis and inflammation were investigated to explore the biological mechanisms underlying the favorable effects of momelotinib on MF-associated anemia.

"The results from this translational biology clinical study provide further evidence for momelotinib's unique anemia benefit," said Dr. Christian Hassig, Chief Scientific Officer of Sierra Oncology. "Moreover, the findings provide clinical evidence that reinforce the differentiated profile of momelotinib as a potent inhibitor of ACVR1, a principal driver of hepcidin production in the liver. As with many inflammatory diseases associated with chronic anemia, myelofibrosis is characterized by high hepcidin, resulting in functional iron deficiency. In myelofibrosis, high levels of hepcidin are inversely correlated with survival. The observed reduction in hepcidin and restoration of iron homeostasis, coupled with net increases in various measures of erythropoiesis, provide important translational biomarker data accounting for the compelling transfusion-independence rates of 34-39% achieved in this transfusion dependent study population."

"As noted in our recent KOL call* featuring Dr. Srdan Verstovsek, one of the investigators in this clinical study, almost every myelofibrosis patient develops anemia and it typically becomes worse over time, often leading to transfusion dependency, yet there are no approved therapies to treat this facet of the disease," stated Dr. Nick Glover, President and Chief Executive Officer of Sierra Oncology. "Momelotinib inhibits JAK1, JAK2 and ACVR1, and is therefore uniquely positioned to address disease-related cytopenia in myelofibrosis, including anemia and transfusion dependency, while also improving splenomegaly and constitutional symptoms."

Sierra is currently preparing for discussions with regulators to determine the registration path for momelotinib and anticipates reporting next steps in the first half of 2019.

*KOL call featuring Dr. Srdan Verstovsek:
http://investor.sierraoncology.com/events-and-webcasts?item=30

About the study (ClinicalTrials.gov Identifier NCT02515630):
In this Phase 2 open-label, translational biology study 41 transfusion-dependent (TD; ≥4 units red blood cells [RBC] transfusion in the 8 weeks prior to first dose of momelotinib) patients with primary or post-ET/PV MF (platelets ≥50 K) received 200 mg momelotinib once daily for 24 weeks.

• By week 24, 14 (34.1%, 90% CI: 22.0–48.1%) patients had a ≥12-week transfusion-independent response (TI-R) and 39.0% had no RBC transfusion for ≥8 weeks at any time (90% CI: 26.2-53.1%).
• At every study visit, median blood hepcidin decreased 6 hours after dosing with momelotinib. Serum iron, transferrin, hemoglobin, reticulocytes, and hematocrit increased at week 2 in patients with TI-R. Following this peak, serum iron decreased while hemoglobin, hematocrit and platelet count increased through week 24.
• Adverse events (AEs) were consistent with previous studies of momelotinib in myelofibrosis, with cough, diarrhea, nausea, and fatigue as the most common. AEs ≥Gr 3 were experienced by 21 patients, most commonly anemia and neutropenia.

Title: Hepcidin Suppression by Momelotinib Is Associated with Increased Iron Availability and Erythropoiesis in Transfusion-Dependent Myelofibrosis Patient

Authors: Stephen T. Oh, Moshe Talpaz, Aaron T. Gerds, Vikas Gupta, Srdan Verstovsek, Ruben Mesa, Carole Miller, Candido Rivera, Angela Fleischman, Swati Goel, Mark Heaney, Casey O'Connell, Murat Arcasoy, Yafeng Zhang, Jun Kawashima, Tomas Ganz, Carrie Baker Brachmann

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 spleen 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 is also preparing 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, use and adequacy of existing cash and cash equivalents, 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