A Study to Evaluate the Safety, Tolerability, Pharmacokinetics (PK), and Pharmacodynamics (PD) of TAK-988 in Healthy Participants

The drug being tested in this study is called TAK-988. TAK-988 is being tested to evaluate safety, tolerability, PK, and PD of single and multiple oral doses in healthy non-Japanese and Japanese adult participants and HE participants. The study will enroll approximately 156 healthy participants. The study consists of 5 parts and up to 19 cohorts as mentioned below: * TAK-988, Part A: Single-rising dose (SRD) design to assess the safety, tolerability, and PK of TAK-988 and effect of food on the PK of the TAK-988 * TAK-988, Part B: MRD design to assess the safety, tolerability, PK and PD of TAK-988 * TAK-988, Part C: MRD design to assess the safety, tolerability, PK and PD of TAK-988 and also central nervous system penetration relative to plasma concentrations of TAK-988 * TAK-988, Part D: MRD design to assess the safety, tolerability, PK and PD of TAK-988 for HE participants * TAK-988, Part E: SRD and MRD design to assess the safety, tolerability, PK and PD of TAK-988 for Japanese origin participants Participants in each cohort will be randomized to receive treatment with TAK-988 or matching placebo which will remain undisclosed to the participant and study doctor during the study (unless there is an urgent medical need). This multi-center trial will be conducted in the United States. The overall duration of the study is approximately 10.5 months. Participants will make a final visit 7 days after receiving their last dose of study drug for a follow-up assessment.