Pembrolizumab + HSPPC-96 misses 1-year OS endpoint in newly diagnosed GBM

Pembrolizumab is an anti–PD-1 antibody, and HSPPC-96 is a personalized tumor-derived HSP96-peptide vaccine designed to broaden antigen presentation. In a multi-institutional Phase 2 randomized, placebo-controlled trial layered onto standard chemoradiation and adjuvant temozolomide in newly diagnosed GBM (NCT03018288), 32 of 90 screened patients were treated, with 26 evaluable for response; 1-year OS was 65.5% with vaccine vs 75% with placebo, and PFS/response differences were mild and not statistically significant. Safety was described as well tolerated without a new signal, but the efficacy miss is meaningful in a setting where TTFields + adjuvant temozolomide has already shown a median OS gain of ~20.9 vs 16.0 months.