Multinational phase 2 study of imetelstat for relapsed or refractory myelofibrosis

A multinational phase 2 study randomized patients with intermediate-2 or high-risk myelofibrosis, R/R to Janus-associated kinase inhibitors, to receive imetelstat 9.4 mg/kg or 4.7 mg/kg intravenous every 3 weeks. Study enrolment was closed early, and patients treated with the lower dose were permitted to continue treatment with 9.4 mg/kg. At week 24, spleen response rate was 10.2% and symptom response rate was 32.2% in the 9.4 mg/kg arm. In this arm the median OS was 29.9 months. Biomarker and bone marrow fibrosis assessments suggested selective effects on the malignant clone. Most common adverse events were grade 3 or 4 reversible cytopenias.