Ruxolitinib vs best available therapy for ET intolerant or resistant to hydroxycarbamide

Treatments for high-risk essential thrombocythemia (ET) address thrombocytosis, disease-related symptoms, as well as risks of thrombosis, hemorrhage, transformation to myelofibrosis and leukemia. Patients resistant/intolerant to hydroxycarbamide (HC) have a poor outlook. MAJIC (ISRCTN61925716) is a randomized phase II trial of ruxolitinib (JAK1/2 inhibitor) vs Best Available Therapy (BAT) in ET and polycythemia vera (PV) patients resistant or intolerant to HC. Here findings of MAJIC-ET are reported, where the modified intention-to-treat population included 58 & 52 patients randomized to receive ruxolitinib or BAT respectively. There was no evidence of improvement in complete response within 1 year reported in 27 (46.6%) patients treated with ruxolitinib vs 23 (44.2%) with BAT (P=.40). At 2 years rates of thrombosis, hemorrhage and transformation were not significantly different, however some disease-related symptoms improved in patients receiving ruxolitinib relative to BAT. Molecular responses were uncommon; there were two complete molecular responses (CMR) and one partial molecular response (PMR) in CALR positive ruxolitinib-treated patients. Transformation to myelofibrosis occurred in one CMR patient, presumably due to the emergence of a different clone raising questions about the relevance of CMR in ET patients. Grade 3&4 anemia occurred in 19% & 0% of ruxolitinib vs 0% (both grades) BAT arm, grade 3&4 thrombocytopenia in 5.2% & 1.7% of ruxolitinib vs 0% (both grades) of BAT treated patients. Rates of discontinuation or treatment switching did not differ between the two trial arms. The MAJIC-ET trial suggests that ruxolitinib is not superior to current second-line treatments for ET.