Safety and efficacy of luspatercept for the treatment of anemia in patients with myelofibrosis.

The ACE-536-MF-001 trial enrolled patients with myelofibrosis (n = 95) into 4 cohorts: patients in cohorts 1 and 3A were non-transfusion dependent (NTD) and had anemia; patients in cohorts 2 and 3B were transfusion dependent (TD); patients in cohort 3A/3B had stable ruxolitinib treatment prior to and during the study. All patients received luspatercept (1.0-1.75 mg/kg, 21-day cycles). Treatment was extended if clinical benefit was observed at day 169. The primary endpoint was anemia response rate (NTD, ≥1.5 g/dL hemoglobin increase from baseline; TD, transfusion-independence) over any 12-week period during the primary treatment period (weeks 1-24). Overall, 14% of patients in cohorts 1 and 3A, 10% in cohort 2, and 26% in cohort 3B met the primary endpoint. In cohorts 1 and 3A (NTD), 27% and 50% of patients respectively had mean hemoglobin increase ≥1.5 g/dL from baseline. Among TD patients, ~50% had ≥50% reduction in transfusion burden. Reduction in total symptom score was observed in all cohorts, with the greatest response rate seen in cohort 3A. Overall, 94% of patients had ≥1 adverse event (AE); 47% had ≥1 treatment-related AE (TRAE; 11% grade ≥3), most frequently hypertension (18%), managed with medical intervention. One patient had a serious TRAE leading to luspatercept discontinuation. Nine patients died on treatment (unrelated to study drug). In most patients, ruxolitinib dose and spleen size remained stable. In patients with myelofibrosis, luspatercept improved anemia and transfusion burden across cohorts; the safety profile was consistent with previous studies. NCT03194542 clinicaltrials.gov.