Multi-peptide Vaccination and Bispecific PSMAxCD3 Antibody Treatment in Patients With Prostate Cancer

CC-1 contains a PSMA binder with particular reactivity in PC and also binds to tumor vessels, thereby allowing for a dual mode of anti-cancer action. CC-1 was developed in a novel format which not only prolongs serum half-life, but most importantly reduces off-target T cell activation with expected fewer side effects. The multi-peptide vaccine VAC-XS15-PC01 is composed of 10 HLA-restricted antigens, comprising immunopeptidome-defined PC-associated epitopes, adjuvanted with the TLR1/2 ligand XS15 emulsified in Montanide ISA 51 VG. The study entails three-arms: (1) the multi-peptide vaccine VAC-XS15-PC01 alone, (2) PSMAxCD3 bispecific antibody CC-1 alone and (3) combinatorial treatment of CC-1 and VAC-XS15-PC01. Up to 84 patients are recruited (n = up to 28 per arm) and patients are randomly assigned 1:1:1 (drop-out rate of 15% anticipated). A translational research program comprising, among others, a strict evaluation of prostate specific antigen (PSA) course integrated with analysis of CC-1 induced immune response and immunogenicity of VAC-XS15-PC01 serves to detect early signs of efficacy. Furthermore, safety of the investigational medical products is evaluated, and tolerability of their combination are assessed.