A Phase 1, Multiple Intravenous Dose Study to Examine Safety, Tolerability, and PK of Intravenous TD-8954, a 5-HT4 Receptor Agonist, in Healthy Subjects

Inclusion Criteria: 1. For Cohorts 1: adult males and females age 18 to 45 years, inclusive; for Cohorts 2 and 3, adult males and females 65 to 85 years of age, inclusive; for Cohort 4, adult males and females 18 to 45 or 65 to 85 years of age, inclusive. 2. Body mass index (BMI)between 18 to 36 kg/m2, inclusive. 3. Average frequency of ≥ 3 bowel movements per week. Exclusion Criteria: 1. Persistent symptoms of functional GI disorder (such as irritable bowel syndrome, functional constipation, functional dyspepsia, or other symptom-based GI disorders unexplained by a pathologically based disorder) during the 6 months prior to screening, including a history of major surgery of the GI tract, excluding cholecystectomy and appendectomy. 2. History or presence of clinically significant respiratory, GI, renal, hepatic, endocrine, hematological, neurological (including chronic headache, current or prior psychiatric disease/condition, stroke), cardiovascular, psychiatric, musculoskeletal, genitourinary, immunological, or dermatological disorders. Subjects with mild, chronic, stable disease (e.g., controlled hypertension, controlled hypercholesterolemia, non insulin-dependent diabetes, osteoarthritis) may be enrolled if the condition is well controlled and not anticipated to interfere with the objectives of the study.