Efficacy of pacritinib versus momelotinib in patients with thrombocytopenic myelofibrosis: a matching-adjusted indirect treatment comparison

Background Thrombocytopenia is a prognostic marker in patients with myelofibrosis, associated with increased morbidity and reduced survival. We conducted a matching-adjusted-indirect-comparison (MAIC) of pacritinib-vs-momelotinib for treatment of patients with thrombocytopenic myelofibrosis.Research design and methods Data were from Phase 3 randomized controlled trials of patients with thrombocytopenic myelofibrosis treated with pacritinib 200 mg BID (PERSIST-2 [NCT02055781]) with baseline platelet count 24‒99 × 109/L matched on prognostic indicators with patients on momelotinib 200 mg QD (pooled post-hoc analysis of patients with platelet count < 100 × 109/L (MOMENTUM [NCT04173494]; SIMPLIFY-1 [NCT01969838]). Week-24 endpoints included % of patients achieving: ≥50% total symptom score reduction (TSS-50), ≥35% spleen volume reduction (SVR-35) and red-blood-cell-transfusion-independence (RBC-TI). Reweighted effects were compared with momelotinib using logistic regression/odds ratio (OR [95% confidence interval, CI]) and Cox regression/hazard ratio (HR [95% CI]) for overall survival (OS).Results After matching, baseline characteristics balanced; 76‒81% of matched pacritinib patients had moderate thrombocytopenia (50‒99 × 109/L platelet count). All outcomes favored pacritinib on ORs (95% CI) for TSS-50: 1.75 (0.60, 5.09); SVR-35: 1.40 (0.32, 6.04); RBC-TI: 1.19 (0.36, 3.97); and OS: HR (95% CI) 0.35 (0.12, 1.05); however, none had statistical significance.Conclusions This MAIC revealed consistent, nominal trends toward pacritinib efficacy benefits and OS in patients with myelofibrosis, most with moderate thrombocytopenia.