A Study of Zasocitinib in Adults With Psoriatic Arthritis Who Have Not Taken Biologic Medicines

Inclusion Criteria:

Age:

1. The participant is aged 18 years or older at the time of signing the informedconsent form (ICF). In South Korea, the age requirement for adult participants is >=19 years of age. Disease Characteristics:

2. The participant has had signs and symptoms consistent with PsA for at least 3months.

3. The participant meets the Classification Criteria for Psoriatic Arthritis (CASPARcriteria).

4. The participant has active arthritis as shown by a minimum of >=3 tender joints inTJC68 and >=3 swollen joints in SJC66 at the screening and baseline (Day 1) visits.

5. The participant has at least 1 active lesion of plaque PsO >=2 cm in diameter, orany nail or nail bed changes characteristic of PsO. Medications for PsA:

6. The participant has had at least one of the following:

7. Inadequate response to a nonsteroidal anti-inflammatory drug (NSAID), OR

8. Inadequate response to a conventional synthetic disease-modifying antirheumaticdrug (csDMARD).

Exclusion Criteria:

PsA and PsO:

1. The participant has other disease(s) that might confound the evaluations of benefitof zasocitinib therapy, including but not limited to rheumatoid arthritis, axialspondyloarthritis, systemic lupus erythematosus, Lyme disease, gout, orfibromyalgia.

2. The participant has a concomitant comorbid skin condition that, in the opinion ofthe investigator, would interfere with the study assessments, such as evidence ofnon-plaque PsO (erythrodermic, pustular, predominately guttate PsO, inverse, ordrug-induced PsO).