A Study to Evaluate How the Study Drug Moves Through the Body, Adverse Events, and How the Body Tolerates ABBV-547 Injections

A First-in-Human, Phase 1a/b, Single-Dose Study of ABBV-547 to Evaluate the Pharmacokinetics, Immunogenicity, Safety, and Tolerability in Adult Participants and Efficacy in Adult Participants

The purpose of this study is to assess how safe, effective, and tolerable ABBV-547 is in adult participants in the United States and Japan.

There will be 2 parts to this study. In Part 1, participants are placed in one of 7 groups where they will receive ABBV-547 at different doses or placebo. There is a 1 in 4 chance participants will receive placebo. In Part 2, participants are placed in one of 3 groups where they will receive ABBV-547 at different doses or placebo. There is a 1 in 7 chance participants will receive placebo. Approximately 121 adult participants will be enrolled at approximately 21 sites in the United States and Japan.

Participants will be administered one dose of ABBV-547 or placebo.

There may be higher treatment burden for participants in this trial compared to their standard of care. Participants will attend regular visits during the study at a hospital or clinic. The effect of the treatment will be checked by medical assessments, blood tests, checking for side effects and completing questionnaires.

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 electrocardiogram (ECG).
• Part 1: BMI is >= 18.0 to <= 29.9 kg/m^2 after rounding to the tenths decimal at Screening. BMI is calculated as weight in kg divided by the square of height measured in meters.
• Part 2: must have discontinued use of phototherapy (e.g., UVA or UVB) at least 2 weeks prior to the baseline visit (Day 1) and PUVA phototherapy at least 4 weeks prior to the baseline visit (Day 1).

Exclusion Criteria:

• History of any clinically significant sensitivity or allergy to any medication or food.
• Part 2: uses any herbal supplements within the 2-week period prior to study treatment administration.
• Part 2: received any biologics including investigational agents within 2.5 half-lives prior to Baseline.