GlaxoSmithKline (GSK) is acquiring Sierra Oncology, which is focused on targeted therapies addressing rare cancers, for approximately $1.9 billion. Sierra’s lead product, momelotinib, is for myelofibrosis patients with anemia—a main segment of this market.
Luke Miels, Chief Commercial Officer for GSK said, “Sierra Oncology complements our commercial and medical expertise in hematology. Momelotinib offers a differentiated treatment option that could address the significant unmet medical needs of myelofibrosis patients with anemia, the major reason patients discontinue treatment. With this proposed acquisition, we have the opportunity to potentially bring meaningful new benefits to patients and further strengthen our portfolio of specialty medicines.”
Myelofibrosis is a fatal cancer of the bone marrow impacting the normal production of blood cells. At diagnosis, approximately 40% of patients are already anemic, and it is estimated that nearly all will eventually develop anemia. Patients treated with the most commonly used therapy, a JAK inhibitor, will often require transfusions. More than 30% of these patients will have to discontinue treatment due to anemia, which is strongly correlated with poor prognosis and decreased overall survival. The median survival for all patients with myelofibrosis is approximately 6 years but is considerably worse for high-risk patients.
Stephen Dilly, president and chief executive officer of Sierra said, “Uniting with GSK creates the best opportunity for Sierra Oncology to realize its mission of delivering targeted therapies that treat rare forms of cancer while also delivering compelling and certain value for our stockholders. Now we have a partner with a global infrastructure and oncology expertise that enables us to deliver momelotinib to patients as quickly as possible and on a global scale.”
Momelotinib can improve anemia and reduce the need for transfusions while also treating symptoms, according to earlier studies. The drug has inhibitory activity along three key signaling pathways: Janus kinase (JAK) 1, JAK2, and activin A receptor, type I (ACVR1)/activin receptor-like kinase-2 (ALK2). Studies suggest the drug can improve anemia and reduce transfusion dependence while treating myelofibrosis symptoms and splenic response.
In January 2022, Sierra Oncology announced positive topline results from the MOMENTUM phase III trial of momelotinib. The study met all its primary and key secondary endpoints, demonstrating the drug achieved a statistically significant and clinically meaningful benefit on symptoms, splenic response, and anemia.
MOMENTUM met the primary endpoint of total symptom score (TSS) reduction of ≥50% with 25% in the momelotinib arm versus 9% in the control arm (p=0.0095). Additionally, the trial met its secondary endpoints of transfusion independence (TI) with 31% in the momelotinib arm versus 20% in the control arm (one-sided p=0.0064; non-inferiority) and SRR based on splenic volume reduction of ≥35% with 23% in the momelotinib arm versus 3% in the control arm (p=0.0006). Grade 3 or worse adverse events in the randomized treatment period were 54% in the momelotinib arm and 65% in the control arm. Serious treatment-emergent adverse events were 35% in the momelotinib arm and 40% in the control arm.
Momelotinib complements GSK’s Blenrep (belantamab mafodotin), building on the big pharma’s commercial and medical expertise in hematology. The proposed acquisition aligns with GSK’s strategy of building a strong portfolio of new specialty medicines and vaccines. If the transaction is completed and momelotinib is approved by regulatory authorities, GSK expects momelotinib will contribute to GSK’s growing specialty medicines business, with sales expected to begin in 2023, with significant growth potential and a positive benefit to the Group’s adjusted operating margin in the medium term.
In addition to momelotinib, Sierra’s pipeline consists of two drug candidates in phase I SRA515 and SRA737. SRA515 is a selective bromodomain-containing protein 4 (BRD4) bromodomain and extra-terminal domain (BET) inhibitor with a novel bivalent binding mode that inhibits both protein bromodomains, and SRA737 is a novel checkpoint kinase 1 (CHK1) inhibitor.