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GSK’s Omjjara (Momelotinib) Receives Approval in Japan for Myelofibrosis Treatment | 2024 | iPharmaCenter

GSK announced that Japan's Ministry of Health, Labour and Welfare (MHLW) has approved Omjjara (momelotinib) for treating myelofibrosis. Omjjara is an oral, once-daily JAK1/JAK2 and activin A receptor type 1 (ACVR1) inhibitor.


The approval is supported by data from the pivotal phase III MOMENTUM and SIMPLIFY-1 trials.


The MOMENTUM trial was designed to assess the safety and efficacy of momelotinib compared to danazol in patients with myelofibrosis who were symptomatic, anaemic, and had previously been treated with a licensed JAK inhibitor. The SIMPLIFY-1 trial evaluated the efficacy and safety of momelotinib versus ruxolitinib in myelofibrosis patients who had not previously received JAK inhibitor therapy.


MOMENTUM, a global, multicenter, randomized, double-blind study, investigated momelotinib versus danazol in 195 symptomatic and anaemic myelofibrosis patients previously treated with a licensed JAK inhibitor. The trial aimed to evaluate momelotinib's safety and efficacy in addressing key disease aspects: symptoms, blood transfusions due to anaemia, and splenomegaly.

The MOMENTUM trial met all its primary and key secondary endpoints, showing statistically significant improvements in constitutional symptoms, spleen size reduction, and transfusion independence in patients treated with momelotinib compared to danazol.


Significant outcomes included a 50% or greater reduction in Total Symptom Score (25% for momelotinib vs. 9% for danazol), a 35% or greater reduction in spleen volume (22% for momelotinib vs. 3% for danazol), and no transfusions with all haemoglobin values ≥8 g/dL during the 12 weeks before week 24 (30% for momelotinib vs. 20% for danazol). The most common non-hematological adverse events in momelotinib-treated patients were diarrhea (26%) and asthenia (16%), while the most common grades 3 and 4 adverse events were thrombocytopenia (19%) and anaemia (11%).


SIMPLIFY-1, a multicenter, randomized, double-blind, phase III study, compared momelotinib's safety and efficacy to ruxolitinib in myelofibrosis patients without prior JAK inhibitor treatment (215 for momelotinib and 217 for ruxolitinib).

The trial met its primary endpoint, showing momelotinib's non-inferiority to ruxolitinib in spleen volume reduction by 35% or more, with a difference of 9%. Additionally, momelotinib showed significant improvements in transfusion independence rates (66.5% for momelotinib vs. 49.3% for ruxolitinib), an 18% difference. The most common grade 3 or higher hematologic abnormalities were thrombocytopenia and anaemia.


Momelotinib's unique mechanism of action involves inhibiting three key signaling pathways: JAK1, JAK2, and ACVR1. Inhibiting JAK1 and JAK2 can alleviate constitutional symptoms and splenomegaly, while ACVR1 inhibition may reduce circulating hepcidin levels, potentially addressing anaemia-related issues.


This approval marks the fourth major regulatory endorsement for GSK's momelotinib in treating myelofibrosis, following approvals under the brand name Ojjaara by the US Food and Drug Administration, and under the name Omjjara by the European Commission and the Medicines and Healthcare products Regulatory Agency in the UK.


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