First-in-Human Study With Single and Multiple Doses of TS-161 in Healthy Participants

Inclusion Criteria: * Healthy adult male and female participants between 18 and 55 years of age, inclusive * Body weight ≥ 45 kg * Body Mass Index (BMI) 18 - 30 kg/m\^2, inclusive Exclusion Criteria: * Significant history or presence of medical disorders or condition capable of significantly affecting the absorption, metabolism, or elimination of drugs * History or presence of psychiatric or neurologic disease or condition * History of seizures * Abnormal EEG observed at screening * Abnormal blood pressure * Breast cancer within the past 10 years, or any other malignancies within the past 5 years * Clinically significant abnormal results in electrocardiogram, blood and urine test * History or presence of liver disease * Participants using medication or supplements within 14 days prior to dosing * Use of N-methyl-D-aspartate (NMDA) receptor modulators (example: dextromethorphan, ketamine, amantadine, memantine) within 90 days of screening * Loss of blood or blood products in excess of 450 mL within 60 days prior to screening * Used any investigational drug within 60 days prior to screening * Recent history of alcohol or drug abuse * Any participant who currently uses or has used tobacco products or nicotine-containing products (cigarettes, pipes, e-cigarettes, nicotine patches, etc.) for one month or more prior to screening Exclusion Criteria for Part B only: * Significant abnormalities in lumbar spine * History of clinically significant back pain, back pathology, and/or back injury * History of migraines, and/or frequent, severe headaches * History or presence of significant active bleeding or coagulation disorder or use of non-steroidal anti-inflammatory drugs or other drugs that affect coagulation or platelet function within 14 days prior to lumbar catheter insertion * Allergy to lidocaine (Xylocaine®) or related drugs * History of adverse reaction to lumbar puncture or epidural procedure