Effect of Hepatic Impairment on the Pharmacokinetics of a Single Dose of TD-9855

This is a multicenter, non-randomized, open label, parallel group, single dose, 2-part study being conducted in adult subjects with mild, moderate, or severe HI (Child-Pugh Class A, B, and C), and in matching healthy subjects. The healthy matching group will be comparable to the corresponding hepatic impairment groups by matching subjects by weight (±20% of group mean), age (±10 years of group mean), and sex (equal ratios across groups). The study will be conducted in two sequential parts: In Part A, following a 28-day screening period, 6 subjects each with mild or moderate HI and 6 matching healthy subjects who meet eligibility criteria will be enrolled and administered a single Dose A (Day 1). In Part B, following a 28-day screening period, 6 subjects with severe hepatic impairment will receive a single Dose A (Day 1). Furthermore, the Sponsor may choose to enroll up to 6 additional healthy subjects in Part B to ensure matching of subjects across all groups for weight, age, and sex is maintained.