The main inclusion criteria include but are not limited to the following: - Has a clinical diagnosis of PsA and fulfillment of the Classification Criteria for Psoriatic Arthritis (CASPAR) criteria at Screening, with symptom onset ≥6 months before Screening. - Has a diagnosis of active plaque psoriasis or documented history of plaque psoriasis. - Has history of biologic disease-modifying antirheumatic drug (bDMARD)-naïve or bDMARD-inadequate response/intolerant.

The main exclusion criteria include but are not limited to the following: - Has any arthritis with onset before age 17 years or current diagnosis of inflammatory joint disease other than PsA (such as, but not limited to, rheumatoid arthritis, systemic lupus erythematosus, systemic sclerosis, myositis, etc), or any other conditions that may, in the judgment of the investigator, interfere with the assessment of PsA. - Has a skin condition diagnosis, other than psoriasis that may, in the judgment of the investigator, interfere with the assessment of psoriasis. - Has a history of cancer (except fully treated nonmelanoma skin cancers or cervical carcinoma in situ after complete surgical removal) and is disease free for <5 years before Randomization. - Has any active infection. - Has known allergies, hypersensitivity, or intolerance to tulisokibart of its excipients.