This is a Phase 1, first in human, randomized, four-part study to investigate the safety, tolerability, and pharmacokinetics of ABBV-CLS-616 after oral dosing in healthy volunteers.

Inclusion Criteria:

• Part 2 only: Participant must have normal platelet count at screening and upon initial confinement.
• Part 2 only: Participant must not have known or suspected coagulopathy, or prothrombin time (PT)/activated partial thromboplastin time (aPTT)/international normalized ratio (INR) values outside of normal range at screening.
• A condition of general good health, based upon the results of a medical history, physical examination, vital signs, neurological examination, ophthalmic examination (Part 2 only) laboratory profile and a 12-lead Electrocardiogram.

Exclusion Criteria:

• Part 2 only: Clinically significant active or recurrent ocular disease.
• Part 2 only: History of lumbar puncture and/or collection of cerebrospinal fluid within 30 days prior to Screening.
• Part 2 only: History of current condition of chronic lower back pain.
• Evidence of conditions that might preclude the subject from undergoing a lumbar puncture.
• History of clinically significant neurological epilepsy, any clinically significant cardiac, respiratory (except mild asthma as a child), renal, hepatic, gastrointestinal, hematologic or psychiatric disease or disorder, coagulopathy, or any uncontrolled medical illness.
• History of suicidal ideation within one year prior to study drug administration as evidenced by answering "yes" to questions 4 or 5 on the suicidal ideation portion of the Columbia Suicide Severity Rating Scale completed at Screening, or any history of suicide attempts within the last two years.