Lag-3 and Gemcitabine for Treatment of Advanced Pancreas Cancer

This is a phase I, single center, open label, non-randomized, dose-escalation phase I study performed in the ambulatory setting in patients receiving first line chemotherapy for unresectable pancreas cancer with gemcitabine weekly and the investigational agent IMP321. IMP321 will be given at D2 and D16 of a 4-week cycle, for a period of 6 months. The hypothesis of this study is that IMP321 is safe for human administration. Additionally we hypothesize that IMP321 elicits an immunomodulatory effect that is therapeutic in the treatment of pancreas cancer. Primary Objectives * To evaluate the safety and tolerability of repeated IMP321 subcutaneous injections in patients being treated with gemcitabine for advanced pancreas cancer. * To determine any dose limiting toxicities of IMP321 in patients being treated with gemcitabine for advanced pancreas cancer. Secondary Objectives * To describe the pharmacokinetics of the last IMP321 subcutaneous injection compared to the first one, in a limited number of patients. * To determine the pharmacodynamics of IMP321 therapy by: * Quantify peripheral blood Treg (CD4+CD25+FoxP3+ T cells) in pancreatic cancer patients before and during treatment with IMP321 by flow cytometry. * Evaluate the B- and T-cell responses to the pancreatic cancer-expressed antigen, mesothelin, by testing for antibodies and T-cell response by ELISpot. * To evaluate the clinical response and time to disease progression with computed tomography examinations at two month intervals (current standard of care in gemcitabine-treated patients).