CTNI-54. RESPONSE BY RANO2.0 CRITERIA IN ONC201 (DORDAVIPRONE)-TREATED PATIENTS WITH RECURRENT H3 K27M-MUTANT DIFFUSE MIDLINE GLIOMA

Abstract PURPOSE Response assessment in neuro-oncology (RANO) 2.0 is a recently established response assessment for glial tumors that is agnostic to WHO grade. This updated response assessment includes quantitative evaluation of enhancing and non-enhancing disease and recommendations to account for pseudoprogression. This analysis evaluated response to ONC201 by RANO2.0 in recurrent, H3K27M-mutant diffuse midline glioma (DMG), which was previously assessed by RANO-HGG/RANO-LGG (Arrillaga-Romany, JCO, 2024). METHODS Fifty patients with recurrent H3 K27M-mutant DMG were selected based on criteria designed with input from regulators to evaluate objective response to ONC201 monotherapy. Patients had contrast-enhancing, measurable, progressive disease, and were ≥90 days from radiation, with adequate washout from other anti-cancer therapies. Diffuse intrinsic pontine glioma, primary spinal tumors, leptomeningeal spread, or CSF-disseminating tumors were ineligible. Response was assessed using RANO2.0 criteria by two-party blinded independent central review. RESULTS Best response by RANO2.0 included one complete response (CR, 2.0%), nine partial responses (PR, 18.0%), and four minor responses (MR, 8.0%). Overall response rate (CR+PR+MR) by RANO2.0 criteria was 28.0% (n=14; 95%CI, 16-42). Disease control rate (CR+PR+MR+SD) was 40.0% (n=20; 26-55). Median duration of response was 10.4 months (95%CI, 7.4-15.4). Median time to response was 4.6 months (range, 1.6-15.9). 6- and 12-month progression free survival rates were 32.0% (95%CI, 19-47) and 27.0% (15-41), respectively. RANO2.0 response as a time-varying covariate was significantly associated with overall survival in a multivariate analysis considering baseline performance score, multiple enhancing target lesions, enhancing tumor size, and number of prior recurrences (HR [95%CI], 0.22 [0.08–0.58]; p=0.0023). Patients with an objective response by RANO2.0 were more likely to be alive at 12 (100%) and 24 (86%) months, have reduced corticosteroid usage, and have improved performance status. Responses occurred at a higher rate among patients with a higher performance score and fewer target lesions. CONCLUSIONS RANO2.0 assessment of ONC201-treated patients suggests durable and clinically meaningful efficacy in recurrent H3K27M-mutant DMG.