Background
CheckMate 548 was a phase III randomized double-blind placebo-controlled trial evaluating nivolumab (anti-PD-1) added to standard STUPP chemoradiation (temozolomide + RT) in patients with newly diagnosed MGMT-promoter–methylated GBM. MGMT-methylated GBM comprises ~40% of GBM cases and has a more favorable prognosis with STUPP (~20–26 months mOS). CheckMate 548 tested whether adding PD-1 blockade to the standard regimen (which already benefits from TMZ) could further improve outcomes in this molecularly favorable subgroup, where immune priming by TMZ-induced tumor cell death might synergize with checkpoint inhibition.
Interventions and follow up
Arm A: Standard STUPP + placebo: radiation 60 Gy + concurrent TMZ 75 mg/m² → adjuvant TMZ × 6 cycles + placebo
Arm B: Standard STUPP + nivolumab 240 mg q2w concurrent and maintenance
Primary endpoint: PFS; key secondary OS
mFollow up: 28.1 months
Arm B: Standard STUPP + nivolumab 240 mg q2w concurrent and maintenance
Primary endpoint: PFS; key secondary OS
mFollow up: 28.1 months
Results
mOS: 21.2 months (nivo+TMZ) vs 20.0 months (TMZ), HR 0.97, 95% CI 0.79–1.18 (NS)
mPFS: 10.6 vs 10.3 months, HR 0.86, 95% CI 0.71–1.04 (NS)
ORR: 33.9% vs 30.0% (NS)
Biomarkers: PD-L1, TMB, and other biomarkers — no subgroup demonstrated benefit with nivolumab
mPFS: 10.6 vs 10.3 months, HR 0.86, 95% CI 0.71–1.04 (NS)
ORR: 33.9% vs 30.0% (NS)
Biomarkers: PD-L1, TMB, and other biomarkers — no subgroup demonstrated benefit with nivolumab
Adverse events
Grade ≥3 AEs: 51.9% (nivo) vs 39.9% (placebo)
Immune-mediated AEs (all grades): hypothyroidism 18.3%, rash 11.8%, hepatitis 6.9%, pneumonitis 4.9%
Grade ≥3 immune-mediated: 16.9%
Grade ≥3 neutropenia: 6.6% vs 7.9%
Grade ≥3 thrombocytopenia: 8.0% vs 8.2%
Discontinuation due to AEs: 21.1% vs 7.8% (substantially higher with nivolumab)
Immune-mediated AEs (all grades): hypothyroidism 18.3%, rash 11.8%, hepatitis 6.9%, pneumonitis 4.9%
Grade ≥3 immune-mediated: 16.9%
Grade ≥3 neutropenia: 6.6% vs 7.9%
Grade ≥3 thrombocytopenia: 8.0% vs 8.2%
Discontinuation due to AEs: 21.1% vs 7.8% (substantially higher with nivolumab)
Conclusions
Nivolumab added to standard temozolomide chemoradiation did not improve PFS or OS compared to placebo in newly diagnosed MGMT-methylated GBM (mOS 21.2 vs 20.0 months, HR 0.97), with substantially higher immune-related adverse events and discontinuation rates, completing the set of negative nivolumab trials across the GBM spectrum and establishing that PD-1 blockade does not benefit GBM patients in any first-line setting.
Key Limitations
Double-blind design strengthened interpretation vs CheckMate 498; high baseline steroid use a confound as in all GBM IO trials; MGMT-methylated GBM may have a different immunobiology than MGMT-unmethylated — both subgroups failed IO; 21.1% treatment discontinuation in nivolumab arm due to AEs (vs 7.8% placebo) is a significant tolerability signal; no benefit in any biomarker subgroup; IDH mutation status not collected at enrollment (effect on tumor immunobiology); the CeTeG/NOA-09 trial showing benefit of lomustine+TMZ in MGMT-methylated GBM provides an alternative intensification strategy that is positive; TTFields not used in either arm.
Clinical Context
CheckMate 548 completes the trilogy of negative nivolumab GBM trials (CheckMate 143: recurrent, CheckMate 498: 1L MGMT-unmethylated, CheckMate 548: 1L MGMT-methylated). No PD-1/PD-L1 inhibitor has demonstrated benefit in any GBM setting. For MGMT-methylated newly diagnosed GBM, options include STUPP ± TTFields and lomustine+TMZ (CeTeG/NOA-09). The DCVax-L results have re-opened debate about active immunotherapy in GBM. Emerging strategies include personalized peptide vaccines (GAPVAC-101, NeoVax), mRNA neoantigen vaccines (mRNA-4157/V940 with pembrolizumab), oncolytic herpes virus (G47Δ), and EGFR-targeted CAR-T cells. The GBM immunotherapy landscape remains a major unmet need.