Evaluation of immunological efficacy of Japanese herbal medicine, hochu-ekki-to and keishi-bukuryo-gan, in patients with castration-resistant prostate cancer under personalized peptide vaccination.

Abstract

e16584 Background: This randomized phase II study investigated the immunological efficacy of herbal medicines (HMs) using Hochu-ekki-to and Keishi-bukuryo-gan, in combination with personalized peptide vaccination (PPV) for castration-resistant prostate cancer (CRPC). Methods: Seventy patients with CRPC were randomly assigned (1:1) to receive PPV plus HMs, or PPV alone. PPV treatment used a maximum of four peptides chosen from 31 peptides derived from cancer antigens according to human leukocyte antigen types and antigen-specific humoral immune responses before PPV, for 8 subcutaneous weekly injections. Peptide-specific cytotoxic T lymphocyte (CTL), immunoglobulin G (IgG), regulatory T cells (Treg), monocytic myeloid-derived suppressor cells (Mo-MDSC) and interleukin-6 (IL-6) responses were measured before and 8th vaccination. Clinical outcomes were also analyzed. Results: The combination therapy of PPV with HMs was well tolerated without severe adverse events but had no significant impact on antigen-specific IgG and CTL, Treg and clinical outcomes. The combination therapy of PPV with HMs stabilized the frequency of M0-MDSCs (1.91% to 1.92%, p = 0.96) and serum levels of IL-6 (19.2 pg/ml to 16.1 pg/ml, p = 0.63). On the other hand, the frequency of Mo-MDSC and levels of IL-6 in the PPV alone were significantly increased (0.91% to 1.49% for Mo-MDSC and 9.2 pg/ml to 19.4 pg/ml for IL-6, respectively). Conclusions: These results suggested that the combination usage of HMs reveals a potential to prevent the immunosuppression induced by Mo-MDSC or IL-6 during the immunotherapy. More research is needed to validate the findings of the present study. Clinical trial information: 000010290.