NCOG-07. SAFETY OF ONC201 TREATMENT IN PATIENTS WITH PREVIOUSLY TREATED H3 K27M-MUTANT GLIOMA: RESULTS FROM ONC028, AN ONGOING COMPASSIONATE USE PROGRAM

Abstract PURPOSE H3 K27M-mutant diffuse midline glioma (DMG) has a poor prognosis, with a median overall survival of 1 year and no proven treatments beyond radiotherapy. ONC201 (dordaviprone), a first-in-class imipridone, previously demonstrated durable responses in patients with recurrent H3 K27M-mutant DMG. The present analysis reports safety data from ONC028, a compassionate use program (CUP) for patients with previously treated H3 K27M-mutant glioma. METHODS ONC028 is an expanded access program that provides ONC201 monotherapy to patients with H3 K27M-mutant glioma. Eligible patients are adults or pediatric patients with H3 K27M-mutant glioma, prior therapy including at least radiation, and adequate organ function. Patients must be ineligible for enrollment in other ongoing clinical studies evaluating ONC201. ONC201 is administered orally once weekly at 625 mg or dose-equivalent based on body weight for pediatric patients. MRIs are performed every two 28-day cycles for the initial 12 months, thereafter every 2-3 cycles. Treatment continues until disease progression, unacceptable adverse events (AEs), or withdrawal of consent. Treatment may continue post-progression at the discretion of the treating physician. Bevacizumab use for radiation necrosis or symptom management is acceptable. AEs are assessed by NCI CTCAE v5.0 criteria. RESULTS The 422 enrolled patients include 191 adults (45.2%) and 231 children (54.7%); 87.1% had a performance score ≥60 and the most common tumor location was the pons (57.3%). Any-causality Grade ≥3 AEs have been reported in 200 patients (47.4%). Grade ≥3 treatment-related AEs (TR-AEs) were reported in 19 (4.5%) patients; the commonest was decreased lymphocyte count, occurring in 3 (0.7%) patients. Any-causality serious AEs (SAE) were reported in 43.1% (n=182) patients. There were 10 (2.4%) patients with reports of treatment-related SAEs, the commonest were ascites, nausea, vomiting, and seizure, each occurring in 2 patients (0.2%). CONCLUSIONS ONC028 provides expanded access to ONC201 treatment for patients with previously treated H3 K27M-mutant glioma who are ineligible for enrollment in ongoing trials of ONC201. ONC201 treatment remains well-tolerated.