Efficacy and safety of ruxolitinib in Asian patients with myelofibrosis.

Myelofibrosis is characterized by progressive cytopenias, bone marrow fibrosis, splenomegaly and severe constitutional symptoms. In the phase 3 Controlled Myelofibrosis Study with Oral JAK Inhibitor Treatment (COMFORT) studies, ruxolitinib, a potent Janus kinase 1 (JAK1)/JAK2 inhibitor, provided substantial improvements in splenomegaly, symptoms, quality-of-life measures and overall survival compared with placebo or best available therapy. No assessments of the efficacy and safety of ruxolitinib have been conducted in Asian patients. Here, we describe results from an open-label, single-arm, phase 2 trial evaluating ruxolitinib in Asian patients with myelofibrosis (n = 120). The primary endpoint was met, with 31.7% of patients achieving a ≥ 35% reduction from baseline spleen volume at week 24. As measured by the 7-day Myelofibrosis Symptom Assessment Form v2.0, 49% of patients achieved a ≥ 50% reduction from baseline in total symptom score. Adverse events were consistent with those seen in the COMFORT studies. Ruxolitinib was well tolerated in Asian patients with myelofibrosis and provided substantial reductions in splenomegaly and improvements in symptoms.