CTIM-35. A PHASE II STUDY OF GITR AGONIST INCAGN01876 AND PD-1 INHIBITOR RETIFANLIMAB IN COMBINATION WITH STEREOTACTIC RADIOTHERAPY IN PATIENTS WITH RECURRENT GLIOBLASTOMA

Abstract BACKGROUND We evaluated the combination of retifanlimab, INCAGN01876, and FSRT in patients with recurrent GBM. METHODS Phase II, single-center, 2 cohort study (A: single-arm non-surgical cohort; B, two-arm neoadjuvant/surgical cohort). Cohort A received pre-FSRT one-time doses retifanlimab (500mg) INCAGN01876 (300mg), (8 Gy x 3 fractions), post-FSRT 28-day treatment cycles (retifanlimab, day 1; days 1, 15). B pre-surgery + INCAGN01876; subsequently, either went directly to resection (Sub-Arm 1) or followed by 2). All resumed immunotherapy post-operatively. Primary endpoint: ORR A. Data cut-off for this analysis was June 30, 2022. RESULTS Thirty-two evaluable patients: A, n=16; n=16 n=8, Sub-Arm 2, n=8). Median follow-up time: 13.6 months; 8.8 months. Forty-four percent women, median age 64 (IQR, 55–65), 56% MGMT unmethylated. Most common grade 3/4 treatment-related AEs included cerebral edema (25%), lymphopenia (16%), cognitive disturbance (13%). Efficacy A: no objective responses observed, best response stable disease achieved 9/16 (56%), PFS 3.9 months (95% CI 2.1 – 6.2 months), OS 9.8 8.3 not reached [NR]). B: NR, 15.1 8.5 NR). are longer compared 1 (PFS, NR vs. 2.2 months, p = 0.009; OS, p=0.026). Results tissue blood-based immune correlative analyses will be presented. CONCLUSIONS The is generally well-tolerated GBM when administered without surgical resection. Survival outcomes neoadjuvant encouraging, largely driven that FSRT.