707 Background: A previous phase II/III trial using a single cancer peptide vaccine derived from vascular endothelial growth factor receptor (VEGFR)2 for patients with advanced pancreatic cancer did not demonstrate the overall survival (OS) benefit (Yamaue et al. Cancer Sci 2015). However, for the next trial, we conducted a multicenter phase II study using multipeptide cocktail vaccine named OCV-C01 derived from a novel higher immunogenic antigen KIF20A, VEGFR1 and VEGFR2 combined with gemcitabine in postoperative adjuvant setting. Methods: A single-arm multicenter phase II study was performed on 30 patients with pancreatic ductal carcinoma who underwent pancreatectomy. At each 28-day treatment cycle, patients received weekly subcutaneous injection of OCV-C01 for 48 weeks, and gemcitabine was administered intravenously at 1,000 mg/m2 on days 1, 8, and 15 for 24 weeks. Patients were followed for 18 months. The primary endpoint was disease-free survival (DFS) and secondary endpoints included safety, OS and immunological assays on peptide-specific cytotoxic T lymphocyte (CTL) activity and KIF20A expression in resected pancreatic cancer. Results: The median DFS was 15.8 months (95% confidence interval (CI), 11.1-20.6), and the DFS rate at 18 months was 34.6% (95% CI, 18.3-51.6). The median OS was not reached and the OS rate at 18 months was 69.0% (95% CI, 48.8-82.5). The administration of OCV-C01 was well tolerated. In the per protocol set, there were significant differences in DFS between patients with and without KIF20A-specific CTL responses (p = 0.027), and between patients with and without KIF20A expression in resected pancreatic cancer tissues (p = 0.014). In addition, all four patients who underwent R0 resection with KIF20A expression had no recurrence of pancreatic cancer with KIF20A-specific CTL responses. Conclusions: OCV-C01 combined with gemcitabine was tolerable with a favorable median DFS of 15.8 months. In cancer vaccine treatment, positive expression of targeted antigen was essential, and postoperative adjuvant setting was more suitable than advanced state of cancer. Clinical trial information: UMIN000007991.
Predictive biomarkers for the efficacy of peptide vaccine treatment: based on the results of a phase II study on advanced pancreatic cancer
