A phase II study of personalized peptide vaccination combined with gemcitabine for non-resectable pancreatic cancer patients

Abstract

We evaluated the safety of, and clinical and immune responses to personalized peptide vaccination with gemcitabine (GEM) as the first line therapy in patients with non-resectable pancreatic cancer. Pre-vaccination peripheral blood mononuclear cells (PBMCs) and plasma were prepared to examine cellular and humoral responses to 14 and 16 peptides in human leukocyte antigen (HLA)-A24+ or -A2+ patients, respectively. Only the reactive peptides (maximum of 4) were administered weekly at 3 mg/peptide. GEM was administered at 1000 mg/m(2) per week for 3 weeks, followed by 1 week of rest. Twenty-one patients with untreated and non-resectable pancreatic cancer were enrolled. The combination therapy was generally well tolerated. Boosting of cellular and humoral responses to the vaccinated peptides was observed in the post-vaccination (eighth) PBMCs and plasma from 14 of 18 and 13 of 18 patients tested, respectively. The best clinical responses were 7 cases of partial response, 9 cases of stable disease, and 5 cases of progressive disease. Median survival time of all 21 patients was 9.0 months (95% CI, 6-15.5 months) with a one year survival rate of 38%. Immune boosting in both cellular and humoral responses was well correlated with overall survival with a hazard ratio of 0.2 (95% CI, 0.06-0.73; log-rank p=0.0239). These results suggest a potential clinical benefit of this combination therapy for non-resectable pancreatic cancer patients as the first line therapy. Further exploration of this approach is warranted.