Drug-Drug Interaction (DDI) Study for TD-9855

Inclusion Criteria: * Willing and able to give written, signed informed consent * Male subjects 19 to 55 years of age (inclusive) * Body mass index 19 to 32 kg/m2 (inclusive), and weigh at least 55 kg * No clinically important abnormal physical findings as determined by the Principal Investigator (PI) at the screening and Day -1 examinations * Negative for hepatitis B virus (HBV), hepatitis C virus (HCV), and human immunodeficiency virus (HIV) antibody at screening. * No clinically important laboratory abnormalities as determined by the PI * Ability to communicate effectively with the Investigator and to comply with all study requirements, restrictions, and direction of the clinic staff * Male subjects must abstain from sexual intercourse or use a highly effective method of birth control * Male smokers: Subjects who self-report to have smoked \> 9 cigarettes per day for at least 6 month prior to screening as confirmed by urine cotinine test at screening and Day -1. * Male smokers: Subjects must be willing to continue consistent use of their tobacco products throughout the study. * Additional inclusion criteria apply Exclusion Criteria: * Positive for hepatitis B virus (HBV), hepatitis C virus (HCV), and human immunodeficiency virus (HIV) antibody at screening. * History or presence of clinically significant respiratory, gastrointestinal, renal, hepatic, hematologic, neurologic (including history of seizure and insomnia), cardiovascular (including postural orthostatic hypotension or tachycardia), psychiatric (including depression and known addictive disorders), musculoskeletal, genitourinary (including urinary retention), immunologic, or dermatologic disorder. * Any other condition that, in the opinion of the PI, would confound or interfere with study participation; evaluation of safety, tolerability, or PK of the investigational drug; or prevent compliance with the study protocol * Any history of suicide attempts/ideation or current suicidal ideation. * Have participated in another clinical trial of an investigational drug (or medical device) within 30 days (or 5 half-lives of the investigational drug if longer than 30 days) prior to Screening, or are currently participating in another trial of an investigational drug (or medical device), or intending to participate in another trial of an investigational drug (or medical device) before completion of all scheduled safety evaluations in this trial * Additional inclusion criteria apply