Ipilimumab and Gemcitabine for Advanced Pancreatic Cancer: A Phase Ib Study

Background Pancreatic ductal adenocarcinoma (PDAC) remains resistant to chemotherapy and immunotherapy individually because of its desmoplastic stroma and immunosuppressive tumor microenvironment. Synergizing cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) immune checkpoint blockade with chemotherapy could overcome these barriers. Here we present results of a phase Ib trial combining ipilimumab and gemcitabine in advanced PDAC. Materials and Methods This was a single-institution study with a 3 + 3 dose-escalation design. The primary objective was to determine the maximum tolerated dose (MTD). Secondary objectives included determining the toxicity profile, objective response rate (ORR), median progression-free survival (PFS), and overall survival (OS). Results Twenty-one patients were enrolled, 13 during dose escalation and 8 at the MTD. The median age was 66 years, 62% were female, 95% had stage IV disease, and 67% had received at least one prior line of therapy. The primary objective to establish the MTD was achieved at doses of ipilimumab 3 mg/kg and gemcitabine 1,000 mg/m(2). The most common grade 3 or 4 adverse events were anemia (48%), leukopenia (48%), and neutropenia (43%). The ORR was 14% (3/21), and seven patients had stable disease. Median response duration for the three responders was 11 months, with one response duration of 19.8 months. Median PFS was 2.78 months (95% confidence interval [CI], 1.61-4.83 months), and median OS was 6.90 months (95% CI, 2.63-9.57 months). Conclusion Gemcitabine and ipilimumab is a safe and tolerable regimen for PDAC with a similar response rate to gemcitabine alone. As in other immunotherapy trials, responses were relatively durable in this study. Implications for Practice Gemcitabine and ipilimumab is a safe and feasible regimen for treating advanced pancreatic cancer. Although one patient in this study had a relatively durable response of nearly 20 months, adding ipilimumab to gemcitabine does not appear to be more effective than gemcitabine alone in advanced pancreatic cancer.