This study is designed to assess the pharmacokinetic properties, safety, tolerability, and immunogenicity of ABBV-142 and determine whether predicted efficacious exposures can be safely achieved in humans.

Inclusion Criteria:

All Parts:

• Volunteers in general good health.

Part 3, ONLY:

HAN CHINESE Participants:

• Participant must be first- or second-generation Han Chinese of full Chinese parentage (both parents of Han Chinese descent), residing outside of China. Participants must be in general good health.
• First-generation participants will have been born in China to two parents and four grandparents, who were also born in China, and are of full Chinese descent.
• Second-generation participants born outside of China must have two parents and four grandparents born in China and are of full Chinese descent.

OR

JAPANESE Participants:

• Participant must be first- or second-generation Japanese parentage (both parents of Japanese descent), residing outside of Japan. Participants must be in general good health.
• First-generation participants will have been born in Japan to two parents and four grandparents born in Japan and are of full Japanese descent.
• Second-generation participants born outside of Japan must have two parents and four grandparents born in Japan and are of full Japanese descent.

Exclusion Criteria:

• 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.
• Use of tobacco or nicotine-containing products within 180 days prior to the first dose of study drug.
• History of clinically significant (per investigator's judgment) drug or alcohol abuse within the last 6 months.