Retifanlimab (INCMGA00012) and Telotristat Ethyl for the Treatment of Advanced Neuroendocrine Tumors and Carcinoid Syndrome

This phase II trial studies the effect of retifanlimab and telotristat ethyl in treating patients with neuroendocrine tumors that have spread to other places in the body (advanced) and carcinoid syndrome. Retifanlimab is a monoclonal antibody that may interfere with the ability of tumor cells to grow and spread. Telotristat ethyl is a drug used to reduce side effects of carcinoid syndrome. Giving retifanlimab and telotristat ethyl may help to control neuroendocrine tumors in patients who also have carcinoid syndrome.