The clinical benefit of ruxolitinib across patient subgroups: Analysis of a placebo-controlled, Phase III study in patients with myelofibrosis

Myelofibrosis (MF) patients can present with a wide spectrum of disease characteristics. We analysed the consistency of ruxolitinib efficacy across patient subgroups in the COntrolled MyeloFibrosis Study With ORal JAK Inhibitor Treatment (COMFORT-I,) a double-blind trial, where patients with intermediate-2 or high-risk MF were randomized to twice-daily oral ruxolitinib (n=155) or placebo (n=154). Subgroups analysed included MF subtype (primary, post-polycythaemia vera, post-essential thrombocythaemia), age (≤65, >65years), International Prognostic Scoring System risk group, baseline Eastern Cooperative Oncology Group performance status (0, 1, ≥2), JAK2 V617F mutation (positive, negative), baseline haemoglobin level (≥100, <100g/l), baseline platelet count (100-200×10⁹/l, >200×10⁹/l), baseline palpable spleen size (≤10, >10cm), and baseline quartile of spleen volume and Total Symptom Score (TSS; Q1=lowest, Q4=highest). Mean percentage change from baseline to week 24 in spleen volume and TSS were calculated for ruxolitinib and placebo in each subgroup. Overall survival was estimated by Kaplan-Meier method according to original randomization group. In ruxolitinib-treated patients, reductions in spleen volume and TSS and evidence of improved survival relative to placebo across subgroups were consistent with those seen in the COMFORT-I population, confirming that ruxolitinib is an effective therapy for the spectrum of MF patients studied in COMFORT-I.