Antiproliferative Effects of Telotristat Ethyl in Patients with Neuroendocrine Tumors: The TELEACE Real-World Chart Review Study

Purpose Neuroendocrine tumors (NETs) associated with carcinoid syndrome (CS) overproduce serotonin, mediated by tryptophan hydroxylase-1 (TPH1). The TPH inhibitor telotristat ethyl (TE) reduces peripheral serotonin and relieves CS symptoms. We conducted a real-world clinical practice study to explore the effects of TE on tumor growth in patients with NETs and CS. Patients and methods Single-arm, pre/post chart review study of patients with advanced NETs who received TE for ≥6 months and had ≥2 radiological scans within 12 months before and ≥1 scan after TE initiation. Linear regression and longitudinal analyses assessed changes in tumor size controlling for background NET treatment. Results Two hundred patients were enrolled, most (61%) had well-differentiated gastrointestinal NETs (61%) and received TE for an average of 12 months (SD, 7.3). Mean reduction in tumor size after TE initiation was 0.59 cm (p=0.006). Longitudinal analysis showed an 8.5% reduction in tumor size (p=0.045) from pre- to post-TE periods. Documented NET treatment prior to initiating TE and time between scans were not significant predictors of changes in tumor size. Results were consistent in a subgroup of patients with the same documented NET treatment before and after initiating TE. Conclusion TE may have antitumor effects consistent with serotonin overproduction in tumor growth.