BACKGROUND Ruxolitinib, a selective JAK1 and JAK2 inhibitor, has clinically significant activity in myelofibrosis. METHODS In a double-blind trial, patients with intermediate-2 or high-risk myelofibrosis were randomized to twice-daily oral ruxolitinib (n=155) or placebo (n=154). The primary endpoint was the proportion of patients with ≥35% spleen volume reduction at 24 weeks assessed by magnetic resonance imaging. Secondary endpoints included durability of response, changes in symptom burden (assessed by Total Symptom Score [TSS]), and overall survival. RESULTS In the ruxolitinib group, 41.9% achieved the primary endpoint versus 0.7% in the placebo group (P<0.001). Spleen response was maintained while taking ruxolitinib: 67% of responding patients maintained response for ≥48 weeks. A ≥50% improvement in TSS at 24 weeks was achieved by 45.9% of ruxolitinib-treated versus 5.3% of placebo-treated patients (P<0.001). Thirteen deaths occurred in the ruxolitinib and 24 in the placebo group (hazard ratio, 0.50; 95% CI, 0.25–0.98; P=0.04). Discontinuations for adverse events were similar between groups (11% each). Among ruxolitinib-treated patients, anemia and thrombocytopenia were the most common adverse events, but rarely led to discontinuation (1 patient for each event). Two patients underwent transformation to acute myeloid leukemia (AML), both in the ruxolitinib group. CONCLUSIONS Ruxolitinib provided significant clinical benefits in patients with myelofibrosis by reducing spleen size, improving debilitating myelofibrosis-related symptoms, and improving overall survival. Improvement came at a cost of more frequent anemia and thrombocytopenia in the early part of the treatment period. The imbalance in AML transformation requires attention in further studies. (Funded by Incyte Corporation; ClinicalTrials.gov, NCT00952289)

BackgroundThe randomized, double-blind, placebo-controlled, phase 3 COMFORT-I trial evaluated the JAK1/JAK2 inhibitor ruxolitinib in patients with intermediate-2/high-risk myelofibrosis. The primary and planned 3-year analyses of COMFORT-I data demonstrated that ruxolitinib—the first myelofibrosis-approved therapy—reduced splenomegaly and prolonged overall survival versus placebo. Here, we present the final 5-year results.MethodsPatients managed in Australia, Canada, and the USA were randomized centrally (interactive voice response system) 1:1 to oral ruxolitinib twice daily (15 or 20 mg per baseline platelet counts) or placebo. Investigators and patients were blinded to treatment. The secondary endpoints evaluated in this analysis were durability of a ≥35% reduction from baseline in spleen volume (spleen response) and overall survival, evaluated in the intent-to-treat population. Safety was evaluated in patients who received study treatment.ResultsPatients were randomized (September 2009–April 2010) to ruxolitinib (n = 155) or placebo (n = 154). At termination, 27.7% of ruxolitinib-randomized patients and 25.2% (28/111) who crossed over from placebo were on treatment; no patients remained on placebo. Patients randomized to ruxolitinib had a median spleen response duration of 168.3 weeks and prolonged median overall survival versus placebo (ruxolitinib group, not reached; placebo group, 200 weeks; HR, 0.69; 95% CI, 0.50–0.96; P = 0.025) despite the crossover to ruxolitinib. The ruxolitinib safety profile remained consistent with previous analyses. The most common new-onset all-grade nonhematologic adverse events starting <12 versus ≥48 months after ruxolitinib initiation were fatigue (29.0 vs 33.3%) and diarrhea (27.8 vs 14.6%). New-onset grade 3 or 4 anemia and thrombocytopenia both primarily occurred within the first 6 months, with no cases after 42 months. The most common treatment-emergent adverse event-related deaths in the ruxolitinib-randomized group were sepsis (2.6%), disease progression (1.9%), and pneumonia (1.9%).ConclusionThe final COMFORT-I results continue to support ruxolitinib as an effective treatment for patients with intermediate-2/high-risk MF.Trial registrationClinicalTrials.gov, NCT00952289

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