A Study to Assess the Safety, Tolerability and How Single Ascending Doses of ABBV-859 Moves Through the Body of Healthy Adult Participants

Inclusion Criteria:

* Participants must voluntarily sign and date an informed consent, approved by an Independent Ethics Committee (IEC)/Institutional Review Board (IRB), prior to the initiation of any screening or study-specific procedures.
* Body Mass Index (BMI) is \>= 18.0 to \<= 32 kg/m2 after rounding to the tenths decimal at screening. BMI is calculated as weight in kg divided by the square of height measured in meters.
* A condition of general good health, based upon the results of a medical history, physical examination, vital signs, laboratory profile and a 12-lead Electrocardiogram (ECG).

Exclusion Criteria:

* History of epilepsy, any clinically significant cardiac, respiratory (except mild asthma as a child), renal, hepatic, gastrointestinal, hematologic, endocrine, immunological, pulmonary, metabolic, neurological or psychiatric disease or disorder, or any uncontrolled medical illness.
* History of any clinically significant sensitivity or allergy to any medication or food.
* History of or active medical condition(s) or surgical procedure(s) that might affect gastrointestinal motility, pH, or absorption \[e.g., Crohn's disease, celiac disease, gastroparesis, short bowel syndrome, gastric surgery (except pyloromyotomy for pyloric stenosis during infancy), cholecystectomy, vagotomy, bowel resection, etc.\].
* Evidence of dysplasia or history of malignancy (including lymphoma and leukemia) other than successfully treated non-metastatic cutaneous squamous cell, basal cell carcinoma or localized carcinoma in situ of the cervix.
* History or evidence of active Tuberculosis disease or latent Tuberculosis infection.