Abstract
Ruxolitinib, a potent Janus kinase 1/2 inhibitor, has demonstrated durable improvements in patients with myelofibrosis. In this analysis of the Phase 3b JUMP study, which included patients aged ≥18 years with a diagnosis of primary or secondary myelofibrosis, we assessed the safety and efficacy of ruxolitinib in patients stratified by Dynamic International Prognostic Scoring System (DIPSS) risk categories. Baseline characteristic data were available to assess DIPSS status for 1844 of the 2233 enrolled patients; 60, 835, 755, and 194 in the low-, intermediate (Int)-1-, Int-2-, and high-risk groups, respectively. Ruxolitinib was generally well tolerated across all risk groups, with an adverse-event (AE) profile consistent with previous reports. The most common hematologic AEs were thrombocytopenia and anemia, with highest rates of Grade ≥3 events in high-risk patients. Approximately, 73% of patients experienced ≥50% reductions in palpable spleen length at any point in the ≤24-month treatment period, with highest rates in lower-risk categories (low, 82.1%; Int-1, 79.3%; Int-2, 67.1%; high risk, 61.6%). Median time to spleen length reduction was 5.1 weeks and was shortest in lower-risk patients. Across measures, 40%-57% of patients showed clinically meaningful symptom improvements, which were observed from 4 weeks after treatment initiation and maintained throughout the study. Overall survival (OS) was 92% at Week 72 and 75% at Week 240 (4.6 years). Median OS was longer for Int-2-risk than high-risk patients (253.6 vs. 147.3 weeks), but not evaluable in low-/Int-1-risk patients. By Week 240, progression-free survival (PFS) and leukemia-free survival (LFS) rates were higher in lower-risk patients (PFS: low, 90%; Int-1, 82%; Int-2, 46%; high risk, 15%; LFS: low, 92%; Int-1, 86%; Int-2, 58%; high risk, 19%). Clinical benefit was seen across risk groups, with more rapid improvements in lower risk patients. Overall, this analysis indicates that ruxolitinib benefits lower-risk DIPSS patients in addition to higher risk.