FDA approves GSK JAK inhibitor for blood cancer

Sept. 18, 2023

After a three month delay to review data, the U.S. FDA has approved GSK’s JAK inhibitor to treat intermediate- or high-risk myelofibrosis in adults with anemia.

Momelotinib, branded Ojjaara, is a once-a-day, oral JAK1/JAK2 and activin A receptor type 1 (ACVR1) inhibitor. According to GSK, it is the only approved medicine for both newly diagnosed and previously treated myelofibrosis patients with anaemia that addresses the key manifestations of the disease — anaemia, constitutional symptoms and splenomegaly (enlarged spleen).

The vast majority of patients with myelofibrosis, a rare blood cancer where scar tissue forms in the bone marrow, eventually develop anaemia, causing them to discontinue treatments and require transfusions.

GSK snapped up the drug, which already had positive phase 3 trial data at the time, in a $1.9 billion purchase of Sierra Oncology in April 2022. By August 2022, the FDA had accepted the drug's NDA, assigning a PDUFA date of June 16, 2023. However, when the June deadline came around, the agency had to extend the review time by three months, citing the need to review data that had recently been submitted.

The approval was based on two phase 3 trials, MOMENTUM and SIMPLIFY-1. The SIMPLIFY trial, which delivered mixed results, was designed to evaluate the efficacy and safety of Ojjaara vs. Incyte's Jakafi for myelofibrosis patients who had not received a prior JAK inhibitor. Regulators were able to evaluate safety and efficacy results based upon a subset of patients with anaemia.