Prostate Cancer Immunotherapy – Strategy with a Synthetic GnRH Based Vaccine Candidate

Previous studies with Gonadotropin Releasing Hormone (GnRH/LHRH) vaccines have demonstrated the usefulness of immunization against this hormone in prostate cancer. To this purpose, we generated the completely synthetic GnRHm1-TT peptide which has been validated in a proof of concept formulated together with Montanide ISA 51 adjuvant. Such vaccine preparation induced a significant anti-GnRH immune response and correspondingly reduced testosterone to castration levels and thus produce a biological response in hormonedependent tumors. As a novel strategy the GnRHm1-TT peptide has been also emulsified with the adjuvant combination Montanide ISA 51 and VSSP. The use of this candidate in healthy animal models showed a significant increase in the anti GnRH immune response in comparison with the previous candidates, including their advantages regarding prostate and its testicle atrophy. Moreover, the use of the GnRHm1-TT/Montanide ISA 51/VSSP vaccine candidate produced a significant inhibition of tumor growth in mice transplanted with hormone-sensitive murine tumor Shionogi SC-115. The development of a Phase I clinical trial in patients with advanced prostate cancer using GnRHm1-TT/Montanide/VSSP vaccine, demonstrated the safety of using this candidate in humans as well as the therapeutic elements which must be demonstrated more widely in future clinical trials.