A Study of the Drug Selinexor With Radiation Therapy in Patients With Newly-Diagnosed Diffuse Intrinsic Pontine (DIPG) Glioma and High-Grade Glioma (HGG)

PRIMARY OBJECTIVES: I. To define toxicities and estimate the maximum tolerated dose (MTD) and recommended Phase 2 dose (RP2D) of selinexor administered as an oral formulation in combination with standard of care radiation therapy (RT), to pediatric patients with newly diagnosed high-grade glioma (HGG) or diffuse intrinsic pontine glioma (DIPG). (Dose-finding phase/phase I) II. To estimate the event-free survival (EFS) distribution for diffuse midline glioma (DMG)/HGG patients and overall survival (OS) distribution for DIPG patients associated with selinexor plus RT, followed by selinexor in patients with newly diagnosed HGG (H3 K27M mutant DMG or H3 K27-wild type HGG) or DIPG, and to compare those outcomes to historical controls. (Efficacy phase/phase II) EXPLORATORY OBJECTIVE: I. To bank tumor specimens and body fluids (blood and cerebrospinal fluid) for future studies. OUTLINE: This is a phase I dose-escalation study of selinexor followed by a phase II study. (STRATUM DIPG AND STRATUM DMG CLOSED TO ACCRUAL 02/14/2025) CHEMORADIOTHERAPY: Patients receive standard of care radiation therapy 5 days per week for 5-7 weeks. Starting on day 4 or 5 of radiation therapy, patients receive selinexor orally (PO) on days 1, 8, 15, 22, 29, 36, 43, and 50 in the absence of disease progression or unacceptable toxicity. After a 2-week rest period, patients proceed to Maintenance. Patients undergo a magnetic resonance imaging (MRI) and may undergo a biopsy during screening. MAINTENANCE: Patients receive selinexor PO on days 1, 8, 15, and 22 of each cycle. Cycles repeat every 28 days for up to 24 cycles of maintenance therapy in the absence of disease progression or unacceptable toxicity. Patients undergo a MRI on study and during follow-up. After completion of study treatment, patients are followed every 3 months for year 1 (i.e., 3, 6, 9, 12 months), then every 6 months for years 2-3 (i.e., 18, 24, 30, 36 months), and finally once yearly for years 4-5 of this study.