The objective of this study is to evaluate the safety, tolerability, immunogenicity and pharmacokinetics (PK ) properties following a single dose of ABBV-277 in healthy adult participants.

Inclusion Criteria:

• Body weight ≥ 35 kg
• Body Mass Index (BMI) is ≥ 18.0 to ≤ 32.0 kg/m^2 after rounding to the tenths decimal.
• A condition of general good health, based upon the results of a medical history, physical examination, vital signs, laboratory profile neurological examination, and a 12-lead ECG

Exclusion Criteria:

• History of epilepsy, any clinically significant cardiac, respiratory (except mild asthma as a child), endocrine, metabolic, renal, hepatic, gastrointestinal, hematologic or psychiatric disease or disorder, or any uncontrolled medical illness.
• Participant must meet pregnancy/conception/partner considerations criteria as detailed in the eligibility section.
• Participants using any medications, vitamins and/or herbal supplements within the 14-day period prior to study drug administration or within 5 half-lives of the respective medication, whichever is longer.
• History of any clinically significant illness/infection/major febrile illness, hospitalization, or any surgical procedure within 30 days prior to the first dose of study drug.
• History of suicidal ideation currently or 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 C - SSRS completed at screening, or any history of suicide attempts within the last two years.