- Viral vector-based immunotherapy, PROSTVAC with or without granulocyte-macrophage-colony-stimulating factor (GM-CSF), was safe and well tolerated in patients with asymptomatic or minimally symptomatic metastatic castration-resistant prostate cancer (mCRPC), but it has no OS or event-free survival benefit.
- The trial was terminated because of futility.
Why this matters
- The PSA-targeted immunotherapy extended OS in phase 2 study, and it is being explored in combination therapy in clinical trials.
- Phase 3, double-blind, randomized study of 1297 patients with asymptomatic or minimally symptomatic mCRPC.
- Patients were randomly assigned 1:1:1 to PROSTVAC (n=432), PROSTVAC+GM-CSF (n=432), or placebo (n=433).
- Primary endpoint: OS
- Funding: Bavarian Nordic; the Institute of Cancer Research.
- Compared with placebo, median OS was not significantly different with PROSTVAC (34.3 vs 34.4 months; HR, 1.01; P=.47) or PROSTVAC+GM-CSF (34.3 vs 33.2 months; HR, 1.02; P=.59).
- 6-month event-free survival was not significantly different with PROSTVAC (OR, 0.96; 95% CI, 0.71-1.29) and PROSTVAC+GM-CSF (OR, 0.89; 95% CI, 0.66-1.20) vs placebo.
- Overall, 91% of patients experienced adverse events; most common were injection site reactions (62%-72%) and fatigue (21%-24%).
- Grade ≥3 adverse events occurred in 21%-23% of patients.
- Early termination because of futility.