Ctim-25. A Randomized Phase 3 Study of Nivolumab or Placebo Combined With Radiotherapy Plus Temozolomide in Patients With Newly Diagnosed Glioblastoma With Methylated MGMT Promoter: Checkmate 548

Abstract BACKGROUND Novel therapies are needed in newly diagnosed glioblastoma as nearly all patients experience recurrence following standard-of-care radiotherapy (RT) + temozolomide (TMZ), including patients with tumors with methylated MGMT promoter, a positive prognostic factor and predictor of benefit with TMZ. Here, we report the final analysis of progression-free survival (PFS), overall survival (OS), and safety from an international randomized, single-blind phase-3 study of nivolumab (NIVO)+RT+TMZ in patients with newly diagnosed glioblastoma with methylated/indeterminate MGMT promoter (CheckMate 548; NCT02667587). METHODS Patients (N=716) aged ≥ 18y were randomized 1:1 regardless of tumor PD-L1 expression to NIVO (240 mg Q2W×8, then 480 mg Q4W) + RT (60 Gy over 6 weeks) + TMZ (75 mg/m2 QD during RT, then 4-week break, then 150–200 mg/m2 QD on days 1–5 of every 28-day cycle for 6 cycles) or placebo (PBO)+RT+TMZ. The dual-primary endpoints were PFS by blinded independent central review and OS, both overall and without baseline corticosteroids. RESULTS As of December 22, 2020, median PFS was 10.6 months (95% CI, 8.9–11.8) with NIVO+RT+TMZ and 10.3 months (95% CI, 9.7–12.5) with PBO+RT+TMZ (HR, 1.06 95% CI, 0.90–1.25). Median OS was 28.9 months (95% CI, 24.4–31.6) with NIVO+RT+TMZ and 32.1 months (95% CI, 29.4–33.8) with PBO+RT+TMZ (HR, 1.10 95% CI, 0.91–1.33). Among patients without baseline corticosteroids, median OS was 31.3 months (95% CI, 28.6–34.8) with NIVO+RT+TMZ and 33.0 months (95% CI, 31.0–35.1) with PBO+RT+TMZ (HR, 1.12 95% CI, 0.87–1.43). Grade 3–4 treatment-related adverse events were 52.4% and 33.6% with NIVO+RT+TMZ and PBO+RT+TMZ, respectively. CONCLUSIONS NIVO added to RT+TMZ did not improve survival in patients with newly diagnosed glioblastoma with methylated/indeterminate MGMT promoter. No new safety signals were observed with NIVO. The role of immunotherapy in this treatment landscape remains an area for further investigation.