Prime-boost Immunotherapeutic Trial in Men With Biochemical Recurrence After Definitive Local Therapy for Prostate Cancer

This is a multi-center Phase 1/2 clinical trial to evaluate safety, PSA response, and immunogenicity of the VTP850 prime-boost immunotherapeutic in men with biochemical recurrence of prostate cancer (PCa) after definitive local therapy for PCa. VTP-850 consists of 2 components: ChAdOx1-PCAQ and MVA-PCAQ. All participants will receive ChAdOx1-PCAQ on Day 1 (prime) and MVA-PCAQ on Days 29 and 57 (boosts; Intervention Period). Participants will be followed for 6 months or until start of new therapy such as Androgen Deprivation Therapy (ADT) or until development of unequivocal metastatic PCa (Short-term Follow-up Period). Participants who have a prostate-specific antigen (PSA) response, defined as ≥50% reduction in serum PSA compared to baseline at any time, measured twice consecutively, at least 2 weeks apart, during the 6 months follow up will be followed for an additional 18 months, up to 24 months from first dose, or until start of new therapy such as ADT or development of unequivocal metastatic PCa (Long-term Follow-up Period). Phase 1 (15-18 participants) will follow a 3+3 design to determine the recommended phase 2 regimen (RP2R; dose level of both ChAdOx1-PCAQ and MVA-PCAQ, and route of administration of MVA-PCAQ (IM or IV)) that will be used in Phase 2. Phase 2 will consist of 2 sequential stages. In Stage 1 of Phase 2, 19 additional participants will be enrolled at the chosen Phase 2 regimen. If 4 or more of the 25 participants at the RP2R (including the Phase 1 participants who received the same dose regimen) have a PSA response, Stage 2 will be opened to enrolment of up to 100 additional participants.