On December 11, 2022 GSK plc (LSE/NYSE:GSK) reported new 48-week data from the MOMENTUM phase III trial that showed a majority of patients treated with investigational momelotinib maintained their responses across key clinical measures including Total Symptom Score (TSS), Transfusion Independence (TI) rate, and Splenic Response Rate (SRR) in myelofibrosis patients previously treated with an approved Janus kinase (JAK) inhibitor (Press release, GlaxoSmithKline, DEC 11, 2022, View Source [SID1234625050]). Additionally, new analyses from MOMENTUM showed that TI response with momelotinib at week 24 was associated with overall survival. These data were presented at the 64th American Society of Hematology (ASH) (Free ASH Whitepaper) Annual Meeting and Exposition (10-13 December) in New Orleans.

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Hesham Abdullah, Senior Vice President, Global Head of Oncology Development, GSK, said: "Myelofibrosis patients have significant medical needs including progressive anemia resulting from the disease and often exacerbated by currently approved treatments. The data presented today reinforce the potential of momelotinib as a treatment option with a favorable impact on myelofibrosis symptoms and spleen volume, as well as on blood transfusions due to anemia."

MOMENTUM is a global, randomized, double-blind phase III clinical trial of momelotinib (MMB) versus danazol (DAN) in patients with myelofibrosis who were symptomatic and anemic and had been previously treated with an approved JAK inhibitor. The study was designed to evaluate the safety and efficacy of momelotinib for the treatment and reduction of the key manifestations of the disease: constitutional symptoms, blood transfusions (due to anemia) and enlarged spleen. Patients were randomized at 2:1 to receive either momelotinib or danazol (n=130 and n=65, respectively). After 24 weeks of treatment, patients on danazol were allowed to crossover to receive momelotinib. Early crossover to momelotinib was available for confirmed splenic progression.

Primary analysis at week 24 met the primary endpoint of TSS reduction of ≥50% over the 28 days immediately before the end of week 24 compared to baseline TSS, using the Myelofibrosis Symptom Assessment Form. It also met key secondary endpoints including TI rate for ≥12 weeks immediately before the end of week 24 with hemoglobin levels ≥8 g/dL and SRR based on splenic volume reduction of ≥35% at week 24 from baseline.

48-week follow-up data from MOMENTUM presented at ASH (Free ASH Whitepaper) demonstrated the following (oral presentation #627):

TSS response at week 24
and maintained below
baseline through week 48

TI response at week 24
and maintained response
through week 48

SRR response at week 24
and maintained below
baseline through week 48
MMB

31/32 (97%)*

36/40 (90%)

24/24 (100%)***

DAN with crossover to MMB at week 24

6/6 (100%)**

10/13 (77%)

2/2 (100%)

*12 of 61 (20%) non-responding patients who received momelotinib at week 24 had achieved a TSS response at week 48

**10 of 35 (29%) non-responding patients who received danazol and crossed over to momelotinib at week 24 achieved a new TSS response at week 48

***data available for 24 of 30 patients who received momelotinib and achieved splenic response at 24 weeks

In MOMENTUM, the most common Grade 3 or greater treatment emergent adverse events in the open-label period, similar to the double-blind period, were thrombocytopenia (9% for the continuous momelotinib treatment arm and 15% for the danazol to momelotinib treatment arm) and anemia (9% for the continuous momelotinib treatment arm and 2% for the danazol to momelotinib treatment arm). Additionally, these efficacy and safety results in patients with thrombocytopenia were consistent with the overall population.

An additional analysis from the MOMENTUM clinical trial evaluated the impact of TI response on overall survival (abstract #3028). As previously presented, patients receiving treatment with momelotinib were more likely to achieve transfusion independence during the study period than patients treated with danazol (TI response at week 24 of 31% and 20% for the momelotinib and danazol arms, respectively; non-inferiority p=0.0064). Momelotinib patients were also less likely to require a transfusion during the study period (35% of momelotinib patients had zero units transfused compared to 17% of danazol patients; odds ratio=2.7; p=0.0107), and more likely to reduce transfusion burden. Data presented at ASH (Free ASH Whitepaper) with additional survival follow up suggests that TI response with momelotinib at week 24 is associated with overall survival (HR=0.27 for TI vs. non-TI; CI 95% 0.09, 0.80) compared to patients who were not TI.

A New Drug Application and Marketing Authorization Application for momelotinib is currently under review with the US Food and Drug Administration (FDA) and European Medicines Agency (EMA), respectively. Momelotinib is not currently approved in any market.

About momelotinib
Momelotinib is an investigational oral treatment for myelofibrosis. Momelotinib not only inhibits the Janus kinase (JAK) 1 signalling pathway and JAK2 signalling pathways, but also activin A receptor type I (ACVR1).1,2,3,4 Inhibition of JAK1 and JAK2 may improve constitutional symptoms and splenomegaly.1,2,4 Additionally, direct inhibition of ACVR1 leads to a decrease in circulating hepcidin, which is often elevated in myelofibrosis and contributes to anemia.1,2,3,4

About myelofibrosis
Myelofibrosis is a rare and potentially fatal cancer characterized by the build-up of excessive scar tissue in the bone marrow, which interferes with the production of healthy blood cells and can lead to: severe low blood counts, including anemia and thrombocytopenia; constitutional symptoms such as weakness and fatigue; and splenomegaly or an enlarged spleen.5,6,7 Myelofibrosis affects about 1 in 500,000 people worldwide.8 At diagnosis, approximately 40% of patients are anemic and nearly all myelofibrosis patients will eventually develop anemia.9,10,11 Patients will often require blood transfusions, and more than 30% will discontinue treatment due to anemia.12 Anemia and transfusion dependence are strongly correlated with poor prognosis, reduced quality of life and shortened survival