Sierra Oncology Reports Favorable Long-Term Safety and Dose Intensity Data for Momelotinib

- Data presented at the 25th European Hematology Association (EHA) Virtual Congress further demonstrate the potential anemia benefits and favorable hematological safety profile of momelotinib -
- Long-term tolerability facilitates sustained dose intensity and prolonged clinical activity; longest ongoing treatment now extends to 10 years -

VANCOUVER, BC, June 12, 2020 /CNW/ - Sierra Oncology, Inc. (NASDAQ: SRRA), a late-stage drug development company focused on the registration and commercialization of momelotinib, a JAK1, JAK2 & ACVR1 inhibitor with a potentially differentiated therapeutic profile for the treatment of myelofibrosis, announced that Long-Term Safety and Dose Intensity data for momelotinib are being presented today in two posters at the 25th European Hematology Association (EHA) Virtual Congress.

More than 820 patients with myelofibrosis have received momelotinib during its development, including a number of patients who remain on treatment since the start of the original Phase 2 studies initiated a decade ago. One of these patients will reach a major milestone this week, having received momelotinib therapy for 10 years, highlighting the relevance of the long-term dosing and safety data for momelotinib being presented this week at EHA. The data presented at EHA draw from more than 550 patients across the two previously conducted SIMPLIFY Phase 3 studies and their subsequent ongoing extended treatment periods. More than 90 SIMPLIFY-1 and SIMPLIFY-2 patients continued to receive momelotinib for 3.5 years or longer.

"Consistent with prior data, and reflecting momelotinib's differentiated pharmacological profile, our new long-term safety analyses continue to show a rapid and sustained increase in hemoglobin levels during momelotinib therapy, in contrast to the significant decrease in hemoglobin for patients receiving ruxolitinib. Patients treated with momelotinib also experienced significantly higher mean platelet counts compared to those receiving ruxolitinib. Importantly, patients who switched from ruxolitinib to momelotinib also achieved a sustained improvement in both hemoglobin and platelets," said Prof. Claire Harrison, Guy's and St. Thomas' NHS Foundation Trust, London, United Kingdom. "In addition to an absence of significant rates of high-grade hematological toxicities, long-term tolerability was favorable with no new safety signals or evidence of cumulative toxicity. Notably, this was achieved with most patients receiving full-dose momelotinib."

"Momelotinib's safety profile and durable anemia benefits facilitated sustained dose intensity across the continuum of JAK inhibitor naïve and previously JAK inhibitor treated myelofibrosis patients. While the starting doses for ruxolitinib were often attenuated due to low platelets, further reductions in dose intensity were also commonly required for ruxolitinib. In contrast, momelotinib was initiated at full dose for all subjects enrolled to the SIMPLIFY studies and high dose intensity was maintained in the majority over extended durations," said Dr. Vikas Gupta, Princess Margaret Cancer Centre, Toronto, Canada. "The ability to safely dose momelotinib sustainably at high dose intensity likely facilitates its ability to durably control the cardinal features of myelofibrosis, namely anemia, constitutional symptoms, and splenomegaly. Furthermore, patients who switch from ruxolitinib to momelotinib saw an immediate and sustained improvement in dose intensity, suggesting a link to the corresponding improvements in hemoglobin and platelets noted by Prof. Harrison. These data suggest that momelotinib may be an optimal therapy in myelofibrosis patients, in particular those experiencing hematological toxicity and disease-related myelosuppression, which are significant unmet needs in this disease."

The SIMPLIFY-1 trial was conducted in JAKi-naïve myelofibrosis patients (n=432) randomized 1:1 to momelotinib or ruxolitinib for 24 weeks. The SIMPLIFY-2 trial was conducted in prior ruxolitinib-treated myelofibrosis patients with hematological toxicity (n=156) randomized 2:1 to momelotinib or best available therapy (consisting of ruxolitinib in 88% of patients) for 24 weeks. All patients were then subsequently allowed to receive momelotinib for an extended treatment period including those who did not receive momelotinib initially, as they were eligible to cross-over to momelotinib at the end of the 24-week randomized treatment period in both studies.

About the Posters:
Please visit www.sierraoncology.com to view Prof. Harrison and Dr. Gupta present the momelotinib Long-Term Safety and Dose Intensity posters. Both e-posters are available through the on-demand EHA Virtual Congress platform at https://ehaweb.org/

Title: Long term Safety of Momelotinib in JAKi Naïve and Previously JAKi Treated Intermediate/High Risk Myelofibrosis Patients
Lead Author: Prof. Claire Harrison, Guy's and St. Thomas' NHS Foundation Trust, London, United Kingdom
Session Title: Myeloproliferative neoplasms - Clinical
Poster No.: EP1113

Title: Momelotinib Dose-Intensity is Maintained in JAKi Naïve and Previously JAKi Treated Intermediate/High Risk Myelofibrosis Patients
Lead Author: Dr. Vikas Gupta, Princess Margaret Cancer Centre, Toronto, ON, Canada
Session Title: Myeloproliferative neoplasms - Clinical
Poster No.: EP1103

About Sierra Oncology
Sierra Oncology is a late stage drug development company focused on achieving the successful registration and commercialization of momelotinib, a potent, selective and orally-bioavailable JAK1, JAK2 & ACVR1 inhibitor with a targeted mechanism of action that enables it to address all three key drivers of myelofibrosis. Momelotinib's differentiated therapeutic profile encompasses robust constitutional symptom improvements, a range of meaningful anemia benefits, including eliminating or reducing the need for frequent blood transfusions, and comparable spleen control to ruxolitinib. More than 1,200 subjects have received momelotinib since clinical studies began in 2009, including more than 820 patients treated for myelofibrosis.

Sierra has launched MOMENTUM, a randomized double-blind Phase 3 clinical trial designed to enroll 180 myelofibrosis patients who are symptomatic and anemic, and who have been treated previously with a JAK inhibitor. The U.S. Food and Drug Administration has granted Fast Track designation to momelotinib. Momelotinib is protected by patents anticipated to provide potential exclusivity to 2040 in the United States and Europe (inclusive of potential Patent Term Extension or Supplementary Protection Certificate).

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 expectations from current data, anticipated clinical development activities, 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.

SOURCE Sierra Oncology

For further information: James Smith, Vice President, Corporate Affairs, Sierra Oncology, 604.558.6536, investors@sierraoncology.com