Sierra Oncology, Inc. (NASDAQ: SRRA), a late-stage biopharmaceutical company on a mission to deliver targeted therapies that treat rare forms of cancer, today announced new retrospective analyses of the momelotinib Phase 3 SIMPLIFY studies will be presented at the 63^rd American Society of Hematology (ASH) Annual Meeting being held virtually and in Atlanta, GA December 11-14, 2021.

Baseline Serum Ferritin Differentially Predicts W24 Transfusion Independence Response for Momelotinib and Ruxolitinib in Patients with Myelofibrosis

Myelofibrosis is characterized by the presentation of constitutional symptoms, splenomegaly and anemia, with the degree of anemia and transfusion dependence being among the most important predictors of overall survival. Prior analyses demonstrate patients randomized to momelotinib who achieve Week 24 Transfusion Independence Response (TI-R) have increased overall survival compared to non-TI responders. The new analyses to be presented by Stephen Oh, MD, PhD, Washington University School of Medicine in St. Louis and Siteman Cancer Center, expand on these findings, demonstrating that the TI-R treatment effect of momelotinib versus ruxolitinib was greater in patients with baseline serum ferritin >90ng/mL versus <90ng/mL in both JAK inhibitor-naïve and in ruxolitinib-experienced patients. These data suggest that pre-treatment serum ferritin level may be an important biomarker for the treatment effect of momelotinib versus ruxolitinib on the clinically important Week 24 TI-R endpoint.

Presentation Details

Abstract: 3638

Title: Baseline Serum Ferritin Differentially Predicts W24 Transfusion Independence Response for Momelotinib and Ruxolitinib in Patients with Myelofibrosis

Presenter: Stephen Oh, MD, PhD

Session Name: 634. Myeloproliferative Syndromes: Clinical and Epidemiological: Poster III

Date and Time: Monday, December 13, 2021, 6:00 pm – 8:00 pm ET

Location: Georgia World Congress Center, Hall B5

About Momelotinib

Momelotinib is a selective and orally bioavailable JAK1, JAK2 and ACVR1 / ALK2 inhibitor for the potential 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 by February 2022. Assuming positive results, Sierra Oncology plans to file a New Drug Application with the US Food & Drug Administration (FDA) in the second quarter of 2022. Momelotinib has been granted Fast Track Designation by the FDA.

About Sierra Oncology

Sierra Oncology is a late-stage biopharmaceutical company on a mission 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 suggestion that pre-treatment serum ferritin level may be an important biomarker for the treatment effect of momelotinib versus ruxolitinib, the expected timing for top-line data in the MOMENTUM clinical trial and the expected timing of filing a New Drug Application with the US Food & Drug Administration. 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 not be able to successfully develop, obtain regulatory approval for and commercialize momelotinib or experience significant delays in doing so, Sierra Oncology may not be able to demonstrate acceptable safety and efficacy of momelotinib and momelotinib in combination with SRA515, the risk that disruptions and impacts of COVID-19 will be significant and lengthy, Sierra Oncology’s ability to continue as a going concern, 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 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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