According to a study, patients with myelofibrosis (MF) who presented with low baseline platelet counts achieved spleen responses and reduced symptom burden with using the inhibitor fedratinib, whether used first-line or as salvage therapy after ruxolitinib failure. The findings were published in the SOHO 2019 Meeting Proceedings Supplement in Clinical Lymphoma, Myeloma and Leukemia.
In this study, which reported the efficacy and safety of fedratinib in JAKARTA and JAKARTA2 studies, researchers assessed 96 patients who received a starting fedratinib dose of 400 mg QD. The key endpoint was defined as spleen volume response rate (SVRR; ≥35% reduction in spleen volume from baseline to end of cycle 6 [EOC6]). The Symptom response rate (RR) included patients with at least 50% reduction from baseline total symptom score on the modified MFSAF at EOC6.
According to the results of the study, in JAKARTA, 15% of patients on fedratinib 400 mg cohort had a baseline platelet count of 50 to <100×109/L; SVRR was 36% (95% CI, 11% to 61%). For those with platelet counts ≥100×109/L (n=82), SVRR was 49% (38% to 60%). Symptom RR was 31% (95%, CI 6%to 56%) and 42% (31%-53%) in the 50 to <100×109/L and ≥100×109/L platelet count groups, respectively.
In JAKARTA2, median prior ruxolitinib treatment duration for all patients was 10.7 months. Among 33/97 patients (34%) with baseline platelet counts of 50 to <100×109/L, SVRR was 36% (95% CI, 20% to 55%). SVRR for patients with platelet counts ≥100×109/L was 28% (18%-41%). Symptom RRs were 39% (95% CI, 22% to 58%) and 20% (11% to 33%) in the 50 to <100×109/L and ≥100×109/L platelet count groups, respectively.
“Adverse events were generally similar between platelet count groups across both studies, with the exception of a higher frequency of expected grade 3 to 4 hematologic events among patients with baseline platelet counts of 50 to <100×109/L,” the authors wrote.
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