Selinexor plus ruxolitinib in JAK inhibitor–naïve patients with myelofibrosis: a multicenter, open-label, phase 1 study

ABSTRACT: The phase 1 portion of SENTRY/XPORT-MF-034 (NCT04562389) evaluated the exportin 1 inhibitor selinexor (40 mg/60 mg once weekly) plus ruxolitinib in JAK inhibitor-naïve patients with myelofibrosis (n = 24). Primary end points were maximum tolerated selinexor dose, recommended clinical trial dose, and safety. No dose-limiting toxicities were reported. Common adverse events were nausea, fatigue, anemia, thrombocytopenia, constipation, vomiting, and headache. Nausea was transient, mainly grade 1, and managed by prophylactic antiemetics. Four deaths occurred, all unrelated to study treatment. Selinexor 60 mg in combination with ruxolitinib was identified as the recommended phase 3 dose based on safety, efficacy, and exposure-response analyses. Overall safety profiles and grades of clinically significant adverse events were similar and generally manageable regardless of selinexor dose. A greater proportion of patients achieved spleen volume reduction of ≥35% (SVR35) and total symptom score reduction of ≥50% (TSS50) at week 24 in the selinexor 60-mg group (79% and 58%) than the 40-mg group (38% and 25%). Among evaluable patients who received suboptimal ruxolitinib ≤5 mg twice daily in the selinexor 60-mg group, SVR35 was observed in 100% (6/6) and TSS50 in 75% (3/4) of patients. The trial was registered at ClinicalTrials.gov as NCT04562389.