Real-world analysis of ruxolitinib in myelofibrosis: interim results focusing on patients who were naive to JAK inhibitor therapy treated within the JAKoMo non-interventional, phase IV trial

Ruxolitinib (RUX) is a Janus kinase 1/2 inhibitor (JAKi) approved in the EU for treating disease-related splenomegaly or symptoms in adults patients with myelofibrosis (MF). This is an interim analysis of JAKoMo, a prospective, non-interventional, phase IV study in MF. Between 2012-2019 (cutoff March 2021), 928 patients (JAKi-naive and -pretreated) enrolled from 122 German centers. This analysis focuses on JAKi-naive patients. RUX was administered according to the Summary of Product Characteristics. Compared to the COMFORT-I, -II, and JUMP trials, patients in JAKoMo were older (median 73 years), had poorer Eastern Cooperative Oncology Group (ECOG) performance statuses (16.5% had ECOG >= 2), and were more transfusion dependent (48.5%). JAKoMo represents the more challenging patients with MF encountered outside of interventional studies. However, patients with low-risk International Prognostic Scoring System (IPSS) scores or without palpable splenomegaly were also included. Following RUX treatment, 82.5% of patients experienced rapid (<= 1 month), significant decreases in palpable spleen size, which remained durable for 24 months (60% patients). Symptom assessment scores improved significantly in Month 1 (median -5.2) up to Month 12 (-6.2). Common adverse events (AEs) were anemia (31.2%) and thrombocytopenia (28.6%). At cutoff, 54.3% of patients had terminated the study due to, death, AEs, or deterioration of health. No new safety signals were observed. Interim analysis of the JAKoMo study confirms RUX safety and efficacy in a representative cohort of real-world, elderly, JAKi-naive patients with MF. Risk scores were used in less than half of the patients to initiate RUX treatment.Trial registration: NCT05044026; September 14, 2021.

Automated summary

This study provides evidence for the safety and efficacy of ruxolitinib in elderly JAKi-naive patients with myelofibrosis in a real-world setting. The results show that ruxolitinib treatment leads to a reduction in spleen size and significant improvement in symptoms. Common adverse events include anemia and thrombocytopenia. Overall, ruxolitinib is a safe and effective treatment option for JAKi-naive patients with myelofibrosis.