Final analysis of a phase I/IIa study with CV9103, an intradermally administered prostate cancer immunotherapy based on self-adjuvanted mRNA.

4535 Background: CV9103 is a prostate cancer (PCA) vaccine that contains the four antigens PSA (prostate specific antigen), PSCA, PSMA and STEAP1 as self-adjuvanted full-length mRNAs. Methods: Patients with castrate resistant PCA with rising PSA and predominantly existing metastases (> 80%) were enrolled into a first-in-man phase I/IIa study. The primary endpoint was safety, the secondary immunogenicity. Three different dose levels (256µg, 640µg and 1280µg total mRNA) were tested in the phase I. Patients were vaccinated intradermally in weeks 1, 3, 7, 15 and 23. Blood samples were taken before the first and two weeks after the 2nd to 4th vaccination. Immune responses were assessed by ELISPOT (IFN-g), intracellular cytokine staining (IFN-g, TNFa), tetramer analysis (all ex vivo) or ELISA (PSA). Results: Three patients each were accrued at the low and medium dose level. One dose limiting toxicity, urinary retention, was observed at the high dose level which was expanded to six patients. A maximum tolerated ...