A Study to Assess Pharmacokinetics, Safety, and Tolerability of ABBV-903 in Healthy Japanese and Han Chinese Participants

Inclusion Criteria: \- Healthy Japanese or Han Chinese male or female; age is between 18 and 65 years, inclusive at the time of screening. * Han Chinese subject must be first-generation Han Chinese of full Chinese parentage residing outside of China. Subjects must maintain a typical Chinese lifestyle, including consuming a typical Chinese diet. OR * Japanese subject must be first- or second generation Japanese of full Japanese parentage. First-generation subjects will have been born in Japan to two parents and four grandparents also born in Japan of full Japanese descent. Second-generation subjects born outside of Japan must have two parents and four grandparents born in Japan of full Japanese descent. All subjects must maintain a typical Japanese lifestyle, including consuming a typical Japanese diet. * Body Mass Index (BMI) is \>= 18.0 to \<= 30.0 kg/m2 after rounding to the tenths decimal, at screening and upon initial confinement. BMI is calculated as weight in kg divided by the square of height measured in meters. Exclusion Criteria: * History of any clinically significant illness/infection/major febrile illness, hospitalization, as determined by the investigator, or any surgical procedure within 30 days prior to the first dose of study drug. * Evidence of dysplasia or history of malignancy (including lymphoma and leukemia) other than successfully treated non-metastatic cutaneous squamous cell, basal cell carcinoma orlocalized carcinoma in situ of the cervix.