An Open-Label Drug-Drug Interaction Study of Telotristat Etiprate and Fexofenadine in Healthy Subjects

Inclusion Criteria: * Healthy adult subjects aged ≥18 to ≤55 years of age at screening * Body mass index ≥18.0 to ≤32.0 kg/m\^2 * Acceptable vital signs at Screening: Systolic blood pressure = 90-140 mm Hg, Diastolic blood pressure = 50-90 mm Hg, Heart rate = 40-100 beats per minute * Willingness to adhere to the restrictions outlined in the protocol * Able to comprehend and sign the Informed Consent Form Exclusion Criteria: * Presence of any clinically significant physical, laboratory, or ECG finding that may interfere with the study in the opinion of the Investigator * Use of any medications, herbal tea, energy drink, herbal products, or supplements within 14 days of Day 1 * Receipt of any investigational agent or study drug within 30 days or 5 half-lives prior to Screening * Receipt of any protein- or antibody-based therapeutic agent within 3 months of Screening * Prior exposure to telotristat etiprate * Use of tobacco, smoking cessation products, or nicotine products within 3 months prior to Screening * History of major surgery within 6 months prior to Screening * History of any GI surgery that may induce malabsorption * History of any serious adverse reaction or hypersensitivity to any component of fexofenadine * History of renal disease, or significantly abnormal glomerular filtration rate (\<90 mL/min as calculated using the Cockcroft-Gault equation) at Screening * History of hepatic disease, or significantly abnormal liver function tests at Screening * History of any clinically significant psychiatric, renal, hepatic, pancreatic, cardiovascular, neurological, endocrinologic, hematological, or GI abnormality * History of any active infection within 14 days prior to first dosing * History of alcohol or substance abuse within 2 years prior to Screening * Positive hepatitis panel (including hepatitis B surface antigen and hepatitis C virus antibody) or positive human immunodeficiency virus antibody screens * Concurrent conditions that could interfere with safety and/or tolerability measurements * Donation or loss of \>500 mL of blood or blood product within 3 months prior to Screening * Women who are breastfeeding or are planning to become pregnant during the study * Positive serum pregnancy test (females only) * Positive urine screen for selected drugs of abuse and cotinine * Consumption of alcohol within 48 hours prior to study start * Consumption of caffeine- and/or xanthine-containing products within 72 hours of study start * Consumption of grapefruit, Seville oranges, and grapefruit- or Seville orange-containing products within 72 hours prior to study start * Unable or unwilling to communicate or cooperate with the Investigator for any reason * Use of any drugs or substances that are known to be substrates, inducers, or inhibitors of CYP3A4 within 30 days prior to the first dose