Phase I clinical trial of cell division associated 1 (CDCA1) peptide vaccination for castration resistant prostate cancer

Cell division associated 1 (CDCA1) was screened as an oncogene that is overexpressed on several cancers, including prostate cancer. A highly immunogenic HLA‐A*2402‐restricted epitope peptide corresponding to part of the CDCA1 protein was also identified. A phase I clinical trial was conducted for patients with castration resistant prostate cancer (CRPC) using a CDCA1 peptide vaccination. Twelve patients having HLA‐A*2402 with CRPC after failure of docetaxel chemotherapy were enrolled. They received subcutaneous administration of the CDCA1 peptide as an emulsion with Montanide ISA51VG once a week in a dose‐escalation manner (doses of 1.0 or 3.0 mg/body, six patients received each dose). The primary endpoint was safety, and the secondary endpoints were the immunological and clinical responses. Vaccination with CDCA1 peptide was well tolerated without any serious adverse events. Peptide‐specific cytotoxic T lymphocyte (CTL) responses using ELISPOT assay and dextramer assay were observed in three patients receiving the 1.0 mg dose and five patients receiving the 3.0 mg dose. The median overall survival time was 11.0 months and specific CTL reacting to CDCA1 peptide were recognized in long‐surviving patients. CDCA1‐derived peptide vaccine treatment was tolerable and might effectively induce peptide‐specific CTLs for CRPC patients. This novel peptide vaccine therapy for CRPC appears promising. (ClinicalTrials.gov number, NCT01225471).