Todorova and colleagues [58] enhanced the DNA vaccine efficacy by heterologous prime-boost regimen in a Phase I/II study. Prostate cancer patients were prime-boosted with alternate injections of recombinant adenoviral vector expressing PSMA and plasmid DNA encoding PSMA and CD86 alongside receiving GM-CSF proteins as adjuvants. After 36-month observation period from the first vaccine injection, 86% of participants developed anti-PSMA antibody.