Sierra Oncology Announces Momelotinib Data for Intermediate / High-risk Myelofibrosis Patients with Lower Baseline Platelet Counts

--Retrospective analyses of the Phase 3 SIMPLIFY studies demonstrate safety and activity profile are not impacted by baseline platelet count--    

VANCOUVER, BC, Dec. 7, 2020 /PRNewswire/ - Sierra Oncology, Inc. (SRRA), a late-stage biopharmaceutical company on a quest to deliver targeted therapies that treat rare forms of cancer, today reported an updated efficacy analyses of momelotinib in myelofibrosis patients with thrombocytopenia. The data were presented in a poster presentation at the 2020 American Society of Hematology Annual Meeting by Jean-Jacques Kiladjian, MD, PhD, Consultant Hematologist, Head, Clinical Investigation Center, Saint Louis Hospital, Paris, France.

"This retrospective analysis of the two Phase 3 SIMPLIFY studies demonstrate that the relative benefit-risk profile of momelotinib and ruxolitinib is influenced by baseline platelet count. What we show in this analysis is that momelotinib's safety and activity profile do not appear to be affected by baseline platelet count, while in contrast, activity with ruxolitinib declined in patients with lower baseline platelet counts," said Dr. Kiladjian. "These updated data analyses complement previous findings that demonstrate the ability to initiate and maintain near-maximal momelotinib dose intensity regardless of baseline platelet count, suggesting that this durable dosing contributes to its efficacy profile."

"These exciting data provide a novel insight into a patient population where momelotinib's unique receptor inhibition profile—JAK1, JAK2 & ACVR1—may be particularly relevant. The observation of preserved activity in patients with reduced platelet counts is provocative and potentially differentiating. The wealth of information contained in the SIMPLIFY studies will enable further analyses and potentially identify additional populations of interest to be presented at future scientific meetings," said Stephen Dilly, MBBS, PhD, Chief Executive Officer at Sierra Oncology. "We now look forward to completing enrollment in the pivotal Phase 3 MOMENTUM study and subsequent topline data to support our plan to file for regulatory approval of momelotinib for the treatment of myelofibrosis."

Momelotinib's Spleen, Symptom and Anemia Efficacy is Maintained in Intermediate/High Risk Myelofibrosis Patients with Thrombocytopenia (Abstract #3086)

Dr. Kiladjian presented comparative efficacy data for momelotinib and ruxolitinib in patients with low platelets from the SIMPLIFY-1 (S1) and SIMPLIFY-2 (S2) Phase 3 studies. Results from the updated analyses include:

• In S1 (JAKi-naïve), patients whose baseline platelet counts were:
• <150 x 10⁹/L, momelotinib achieved substantially higher TI (62% vs. 42%) and splenic response rates (23% vs. 4%) and a similar symptomatic response (28% vs. 33%) relative to ruxolitinib
• 150-300 x 10⁹/L, generally similar splenic (35% vs. 32%) and symptom response rates (33% vs. 41%) and a higher TI response rate (72% vs. 54%) were achieved with momelotinib relative to ruxolitinib
• >300 x 10⁹/L, ruxolitinib achieved higher splenic (44% vs. 19%) and symptom response rates (46% vs. 23%) at week 24 than with momelotinib; the Week 24 TI rate remained higher with momelotinib (63% vs. 51%)
• In S2 (JAKi-exposed patients):
• Momelotinib's response rates for the 3 response parameters remain very consistent with overall ITT response rates in patients whose baseline platelets were <150 x 10⁹/L
• Momelotinib's symptomatic and anemia benefit were also preserved in patients whose baseline platelet counts were <50 and >50-100 x 10⁹/L
• In both S1 and S2, rates of TEAEs on momelotinib were generally similar between the overall safety population and subjects with baseline platelets <150 x 10⁹/L

Patients were randomized 1:1 (S1) and 2:1 (S2) to receive momelotinib (200 mg QD) versus ruxolitinib (20 mg BID) or best available therapy (88.5% RUX/RUX+) for 24 weeks followed by extended momelotinib treatment. A baseline platelet limit of >50 x 10⁹/L was required in S1 while there was not lower platelet limit for S2. Both trials had primary endpoints of Splenic Response Rate and secondary endpoints of Total Symptom Score and Transfusion Independence Rate.

About Momelotinib

Momelotinib is a selective and orally bioavailable JAK1, JAK2 and ACVR1 inhibitor currently under investigation for the treatment of myelofibrosis. Myelofibrosis results from dysregulated JAK-STAT signaling and is characterized by constitutional symptoms, splenomegaly (enlarged spleen) and progressive anemia.

Momelotinib is currently under investigation in the MOMENTUM clinical trial, a global, randomized, double-blind Phase 3 study for symptomatic and anemic myelofibrosis patients. Top-line data are anticipated in H1 2022. The U.S. Food & Drug Administration has granted Fast Track designation for momelotinib.

About Sierra Oncology

Sierra Oncology is a late-stage biopharmaceutical company on a quest to deliver targeted therapies that treat rare forms of cancer. We harness our deep scientific expertise to identify compounds that target the root cause of disease to advance targeted therapies with assets on the leading edge of cancer biology. Our team takes an evidence-based approach to understand the limitations of current treatments and explore new ways to change the cancer treatment paradigm. Together we are transforming promise into patient impact.

For more information, 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 and success of enrollment of MOMENTUM and potential benefits of momelotinib. 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's cash resources may be insufficient to fund its current operating plans and it may be unable to raise additional capital when needed, the risk that disruptions and impacts of COVID-19 will be significant and lengthy, Sierra Oncology may be unable to successfully develop and commercialize momelotinib, momelotinib may not demonstrate safety and efficacy or otherwise produce positive results, Sierra Oncology may experience delays in the clinical development of momelotinib, 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 may be unable to obtain and enforce intellectual property protection for its technologies and momelotinib 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.

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SOURCE Sierra Oncology