Bomedemstat in essential thrombocythemia: Phase II study

Results from an open-label, single-arm, phase II trial (NCT04254978) evaluating bomedemstat in 73 patients with essential thrombocythemia (ET) who had an inadequate response to or were intolerant of ≥1 standard therapy were published in Blood Advances by Gill et al. The primary endpoints were safety and response, defined as a reduction in platelet count to ≤400 × 10⁹/L without new thromboembolic events. 

Key data: At Week 24, 77% of evaluable patients achieved a response (n = 64; 95% confidence interval [CI], 64.3–86.2; p < 0.0001), with a median time to first response of 71 days. During the overall treatment period, 10% of patients achieved a complete response (CR), while 68% of patients achieved a partial response (PR). A durable reduction in platelet and white blood cell counts was observed in 72% and 85% of patients, respectively. During the overall treatment period, 5% of patients experienced ≥1 thrombotic event and 32% experienced ≥1 hemorrhagic event. A decrease in variant allele frequency (VAF) of CALR, JAK2, or MPL was observed in 85% of evaluable patients (n = 46). Grade 3/4 adverse events (AEs) and serious AEs (SAEs) occurred in 47% and 37% of patients, respectively. 

Key learning: Bomedemstat demonstrated clinically relevant hematologic activity in patients with ET; however, the single-arm design and limited follow-up preclude definitive conclusions, and randomized trials are warranted.