A Study to Assess Relative Bioavailability and Food Effect of ABBV-668 Extended-Release Formulations in Adult Participants

* BMI is ≥ 18.0 to ≤ 32.0 kg/m\^2 after rounding to the tenths decimal at screening. * A condition of general good health, based upon the results of a medical history, physical examination, vital signs, laboratory profile and a 12-lead ECG.

* History of any clinically significant sensitivity or allergy to any medication or food. * History of any investigational drug within 30 days or 5 half-lives of the drug (whichever is longer) prior to the first dose of study drug or is currently enrolled in another clinical study or was previously enrolled in this study. * History of epilepsy, any clinically significant cardiac, respiratory (except mild asthma as a child), renal, hepatic, gastrointestinal, hematologic or psychiatric disease or disorder, or any uncontrolled medical illness. * Participant using any medication, vitamins and/or herbal supplements (including traditional Chinese medicine), with the exception of hormonal replacement therapies for females, on a regular basis. * Any use of tobacco or nicotine-containing products within 180 days prior to the first dose of study drug.