“The current state for the treatment of myelofibrosis relies on JAK2,” said Ruben Mesa, MD, of the Mays Cancer Center at the UT Health San Antonio MD Anderson Cancer Center.
“Momelotinib is a JAK1 and JAK2 inhibitor.” However, in the early days of studying momelotinib,“it became clear that there was also potentially an improvement in anemia,” which may be related to the additional inhibition of ACVR1, he explained.
Data suggest that the ability to curb anemia in anemic myelofibrosis patients prolongs their lives for up to 8 years, Dr. Mesa added.
Previous studies, notably the phase 3 SIMPLIFY study, showed that momelotinib was associated with comparable effects on spleen volume, transfusion, and total symptom scores from baseline that were similar to ruxolitinib.
In the current study, known as MOMENTUM, a daily dose of momelotinib was compared to danazol for treatment of symptomatic and anemic myelofibrosis (MF) patients who had previously received standard JAK-inhibitor therapy.
In the study, the researchers randomized 130 patients to momelotinib and 65 to danazol. After 24 weeks, those in the danazol group were allowed to cross over to momelotinib. The primary endpoint of the study was total symptom score (TSS) response after 24 weeks. Secondary endpoints included transfusion independence and splenic response at 24 weeks. The median age of the patients in the momelotinib group was 71 years, 60.8% were male, and 82% were white. The baseline demographics were not significantly different in the danazol group.
Overall, 24.6% of momelotinib patients responded with improved total symptom scores at 24 weeks vs. 9.2% of the danazol group. Spleen response also was significantly higher in the momelotinib group; 40% of patients showed a 25% reduction and 23% showed a 35% reduction, compared with 6.2% and 3.1%, respectively, of patients in the danazol group. Transfusion independence at week 24 also was higher for momelotinib patients, compared with danazol patients (31% vs. 20%, respectively, P = 0064).
Adverse events of grade 3 or higher occurred in 53.8% of momelotinib patients and 64.6% of danazol patients, and serious adverse events occurred in 34.6% and 40.0%, respectively. Nearly all patients had anemia, but only 27.7% and 26.2% of the momelotinib and danazol groups, respectively, had thrombocytopenia of grade 3 or higher. The most common nonhematologic adverse events were diarrhea, nausea, and increased blood creatinine. A total of 27.7% of the patients in the momelotinib group discontinued treatment; 16 of whom did so because of an adverse event.
Also, at 24 weeks, patients in the momelotinib group showed a trend towards increased overall survival, compared with danazol (HR, 0.506, P = 0.719).
With momelotinib, there is a consistent thrombocytopenic profile across subgroups, the data on which were presented separately at ASCO (poster 7061), Dr. Mesa added.
“We feel that these findings support the future use of momelotinib as an effective treatment in MF patients, especially those with anemia,” he concluded.
Cytopenia data are exciting
The key finding in the current study is that “momelotinib leads to important endpoints including significant improvement in symptoms and spleen reduction,” said Dr. Gabriela Hobbs of Harvard Medical School, Boston, who served as the discussant for the study.
“I think a novel finding of momelotinib that is definitely exciting from the treatment perspective is that momelotinib can also lead to improvement in cytopenias,” she said. “We often have to decide between treating the symptoms of the spleen at the expense of blood counts,” in MF patients, she noted.
The study was sponsored by Sierra Oncology. Dr. Mesa disclosed relationships with companies including Constellation Pharmaceutical, La Jolla Pharma, and study sponsor Sierra Oncology, as well as funding from AbbVie, Celgene, Constellation Pharmaceuticals, CTI, Genentech, Incyte, Mays Cancer Center, NCI, Promedior, and Samus. Dr. Hobbs had no financial conflicts to disclose.
This article was updated 06/14/2022.