Epacadostat and Pembrolizumab in Patients With GIST

Primary objective is to assess the efficacy of combined Indoleamine 2,3-dioxygenase (IDO) and PD-1 inhibition in a single arm phase II trial of epacadostat and pembrolizumab in patients with advanced imatinib-refractory GIST, using a primary endpoint of overall response rate. Secondary objectives are to evaluate the progression free survival (PFS), the overall survival (OS), the response rate and to evaluate the safety and tolerability of combined epacadostat and pembrolizumab treatment. The investigator hypothesizes that treatment with epacadostat and pembrolizumab will increase the response rate compared to what has been historically achieved with salvage tyrosine kinase inhibitors.