• Sierra Oncology’s differentiated momelotinib has the potential to address the critical unmet medical needs of myelofibrosis patients with anaemia
• Momelotinib complements GSK’s existing expertise in haematology, with Sierra Oncology anticipating US regulatory submission in Q2 this year and EU submission in the second half of 2022
• Sales contribution expected to start in 2023 with significant growth potential thereafter
• Supports development of strong portfolio of new specialty medicines and vaccines

GlaxoSmithKline plc (LSE/NYSE: GSK) and Sierra Oncology, Inc (Nasdaq: SRRA) today announced that the companies have entered into an agreement under which GSK will acquire Sierra Oncology, a California-based, late-stage biopharmaceutical company focused on targeted therapies for the treatment of rare forms of cancer, for $55 per share of common stock in cash representing an approximate total equity value of $1.9 billion (£1.5 billion).

Myelofibrosis is a fatal cancer of the bone marrow impacting the normal production of blood cells. Anaemia represents a high unmet medical need in patients with myelofibrosis. At diagnosis, approximately 40% of patients are already anaemic, and it is estimated that nearly all patients will eventually develop anaemia.[1]^,[2] Patients treated with the most commonly used JAK inhibitor will often require transfusions, and more than 30% will discontinue treatment due to anaemia.[3] Anaemia and transfusion dependence are strongly correlated with poor prognosis and decreased overall survival.[4]

Momelotinib has a differentiated mode of action with inhibitory activity along key signalling pathways. This activity may lead to beneficial treatment effects on anaemia and reduce the need for transfusions while also treating symptoms. In January 2022, Sierra Oncology announced positive topline results from the MOMENTUM phase III trial. The study met all its primary and key secondary endpoints, demonstrating that momelotinib achieved a statistically significant and clinically meaningful benefit on symptoms, splenic response, and anaemia.

Luke Miels, Chief Commercial Officer, GSK said: “Sierra Oncology complements our commercial and medical expertise in haematology. Momelotinib offers a differentiated treatment option that could address the significant unmet medical needs of myelofibrosis patients with anaemia, 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.”

Stephen Dilly, MBBS, PhD, President and Chief Executive Officer, Sierra Oncology said: “Uniting with GSK creates the best opportunity for Sierra Oncology to realise 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 complements GSK’s Blenrep (belantamab mafodotin), building on GSK’s commercial and medical expertise in haematology. 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.