The objective of this study is to assess the pharmacokinetic (PK), immunogenicity, safety, and tolerability of ABBV-1451 after single ascending doses in healthy adult volunteers.

Inclusion Criteria:

• 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.

• Applies to Part 2 only:

• For Japanese participants:

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

• For Han Chinese participants:

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

Exclusion Criteria:

• 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.
• History of any clinically significant sensitivity or allergy to any medication or food.
• 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 treatment.