Longitudinal Assessment of Transfusion Intensity in Patients With JAK Inhibitor–Naive or –Experienced Myelofibrosis Treated With Momelotinib

Purpose: Anemia is a cardinal feature of myelofibrosis often managed with red blood cell (RBC) transfusions, which may contribute to negative prognostic, quality-of-life, and healthcare-related economic impacts. The Janus kinase (JAK) 1/JAK2/activin A receptor type 1 inhibitor momelotinib was approved for the treatment of patients with myelofibrosis and anemia based on clinical trial evidence of anemia, spleen, and symptom benefits illustrated using binomial response/nonresponse endpoints. In the present post hoc, descriptive analyses, the impact of momelotinib on RBC transfusion burden over time was further characterized across JAK inhibitor–naive and –experienced patients. Methods: All RBC units transfused were collected during the baseline and 24-week treatment periods, initially in a single-arm phase 2 study as proof-of-concept analysis, and then versus comparators (ruxolitinib, best available therapy [BAT], and danazol) in the phase 3 SIMPLIFY-1, SIMPLIFY-2, and MOMENTUM studies, respectively. Results: In the phase 2 study, mean transfusion requirement changed by −1.5 units/28 days, with 85% of patients (35/41) achieving numeric transfusion reduction. Across SIMPLIFY-1, SIMPLIFY-2, and MOMENTUM, mean transfusion requirements decreased with momelotinib (−0.1, −0.36, and −0.86 units/28 days), while mean requirements with ruxolitinib, BAT, and danazol changed by +0.39, 0, and ‒0.28 units/28 days, respectively. Overall, 87% (185/213), 77% (79/103), and 85% (110/130) of patients had improved or stable transfusion intensities with momelotinib versus 54% (117/216), 62% (32/52), and 63% (41/65) with ruxolitinib, BAT, and danazol. Conclusion: These novel time-dependent transfusion burden analyses demonstrate that momelotinib is associated with anemia-related benefits in most patients and greater transfusion burden reduction versus comparators. Trial registration: ClinicalTrials.gov identifiers: NCT02515630, NCT01969838, NCT02101268, NCT04173494.