Phase I Trial of Selinexor in Pediatric Recurrent/Refractory Solid and CNS Tumors (ADVL1414): A Children's Oncology Group Phase I Consortium Trial

Selinexor is a first-in-class, central nervous system (CNS)-penetrant, oral inhibitor of exportin 1 (XPO1), the main nuclear exporter of many key tumor suppressors. We report a phase I trial of selinexor in children and adolescents with recurrent CNS and solid tumors (NCT02323880).

A rolling six design was used to evaluate the maximum tolerated dose (MTD) and first dose pharmacokinetics of selinexor administered once (35-45 mg/m2) or twice (20-35 mg/m2) weekly during a 28-day cycle (part A). Ten additional patients with high-grade glioma (HGG) were treated at the MTD administered once weekly (part B).

In part A, 49 patients were enrolled. Continuous twice weekly dosing was limited by extended hematologic toxicity. The MTD on a twice weekly schedule for 3 weeks on/1 week off (twice weekly 3/1) was 20 mg/m2/dose. Dose-limiting toxicities (DLTs) on this schedule included fatigue, acute reversible neurologic changes, neutropenia, thrombocytopenia, and aspartate aminotransferase/alanine aminotransferase increase. On a continuous once weekly schedule, the MTD was 35 mg/m2/dose; DLTs included seizure and thrombocytopenia. In part B (HGG expansion), there were no additional DLTs observed. Non-DLTs included lymphopenia, leukopenia, neutropenia, thrombocytopenia, anorexia, fatigue, hypophosphatemia, nausea, and vomiting. There were no objective responses. The median number of cycles received was 1 (range, 1-9); eight of 59 patients (13.5%) received 5 to 9 cycles, five of whom had HGG.

Selinexor-related toxicities were primarily hematologic and neurologic, requiring dose or dose-frequency reduction. The MTD and recommended initial phase II dose of selinexor in children and adolescents with recurrent solid and CNS tumors is 35 mg/m2/dose once weekly.