pTVG-HP (PAP DNA vaccine) signals OS benefit in PSA-recurrent nonmetastatic prostate cancer vs placebo

pTVG-HP is a plasmid DNA vaccine encoding prostatic acid phosphatase (PAP), administered with GM-CSF, evaluated in a randomized Phase 2 trial in PSA-recurrent, nonmetastatic, noncastrate prostate cancer (NCT01341652). In long-term follow-up (median 4.1 years; range 0.1–13.8+), median OS was 13.4 years with pTVG-HP (n=48) vs 8.6 years with placebo/GM-CSF alone (n=49) (HR 0.42, 95% CI 0.20–0.90), despite the original primary endpoint (2-year MFS) being negative; at a single site with treatment-exposure data (n=59), OS attenuated after adjustment for baseline factors and subsequent therapies (adjusted HR 0.60, 95% CI 0.36–1.00), with later median time to ADT start (2.2 vs 1.4 years) and longer median time from ADT to next therapy for castration-resistant disease (4.7 vs 2.1 years). In this disease state, “standard” management is heterogeneous (observation vs salvage RT when feasible, and/or ADT often deferred until higher-risk kinetics), and historical natural-history estimates from BCR to metastasis/death can already span many years—so an ~4.8-year median OS delta in a small Phase 2 dataset is directionally notable but highly sensitive to post-protocol treatment imbalance and site-level follow-up completeness.