Telotristat Ethyl for the Treatment of Carcinoid Heart Disease in Patients With Metastatic Neuroendocrine Tumor

PRIMARY OBJECTIVE: I. To estimate the percent change in N-terminal pro B-type natriuretic peptide (NT-proBNP) at 6 month visit from baseline after initiation of study drug in each arm and to compare the percent change between the two study arms. SECONDARY OBJECTIVES: I. To evaluate the change in functional capacity from baseline at 3 and 6 month visits as assessed by a 6 minute walk test (6MWT) in each arm. II. To evaluate changes in echocardiographic parameters (Carcinoid Valvular Heart Disease \[CVHD\] score, global longitudinal myocardial strain assessment of the left and right ventricle/tricuspid annular plane systolic excursion \[TAPSE\]) from baseline to 3 and 6 month visits in each arm. III. To evaluate the change from baseline to 3 and 6 month visits in plasma 5-hydroxyindoleacetic acid (5-HIAA) levels in each arm. IV. To evaluate the change from baseline to 3 and 6 month visits in high sensitivity troponin T in each arm. V. To evaluate the change from baseline to 3 and 6 month visits in health related quality of life with using the MD Anderson Symptom Inventory (MDASI) in each arm. VI. To evaluate compliance of medications. OUTLINE: Patients are randomized to 1 of 2 arms. ARM A: Patients receive telotristat ethyl orally (PO) three times daily (TID) and somatostatin analog therapy (SSA) for 6 months in the absence of disease progression or unacceptable toxicity. ARM B: Patients receive placebo PO TID and SSA for 6 months in the absence of disease progression or unacceptable toxicity. After completion of study treatment, patients are followed up for 30 days.