Gastrointestinal bleeding during anti-angiogenic peptide vaccination in combination with gemcitabine for advanced pancreatic cancer.

Most pancreatic cancer patients are diagnosed at the advanced stages, and no therapy is superior to gemcitabine alone. To confirm the feasibility and efficacy of a novel clinical intervention using tumor vessel-specific anti-angiogenic peptide vaccination, we conducted a clinical phase I/II trial using HLA-A2402/A0201-restricted vascular endothelial growth factor receptor type 1 (VEGFR1)-derived peptide vaccination in combination with gemcitabine for advanced pancreatic cancer (http://www.clinical-trials.gov; NCT00683358 and NCT00683085). Four of the enrolled patients (n = 2 for HLA-A2402 and n = 2 for HLA-A0201 protocol, respectively), defined as having progressive disease according to the Response Evaluation Criteria in Solid Tumors version 1.0 (RECIST v.1.0), failed to respond to the therapy. Another two patients enrolled in HLA-A2402 protocol dropped out of the study due to rapid disease progression. Grade 2-3 hematologic toxicities were observed in all cases, but the treatment was well tolerated with minimal systemic adverse events. One case in HLA-A2402 protocol and another case in HLA-A*0201 protocol suffered complicated gastrointestinal (GI) bleeding during vaccination. The causal relationship between GI bleeding and VEGFR1-peptide vaccination is unclear according to the pathologic examination. These studies terminated prematurely because of the advanced stage of the disease in the enrolled patients on entry to the study. Despite GI bleeding, peptide vaccination provides a feasible treatment option for many advanced pancreatic cancer patients.