Continuation Study of Zasocitinib in Adults With Psoriatic Arthritis

Number of Participants With Treatment-emergent Adverse Events (TEAEs) and Serious Adverse Events (SAEs)

Timeframe: From start of study drug administration up to follow-up (up to Week 108)

An adverse event (AE) is any untoward medical occurrence in a clinical study participant, temporally associated with the use of the trial intervention, whether or not the occurrence is considered related to the trial intervention. TEAE is defined as any AE emerging or manifesting at or after the initiation of treatment in the LTE study with a trial intervention or medicinal product or any existing AE that worsens in either intensity or frequency following exposure to the trial intervention or medicinal product. SAE is any untoward medical occurrence that results in death, is life-threatening, requires inpatient hospitalization or prolongation of hospitalization, results in persistent or significant disability/incapacity, results in a congenital abnormality/birth defect, or is an important medical event.

Number of Participants With Adverse Events of Special Interest (AESI)

Timeframe: From start of study drug administration up to follow-up (up to Week 108)

An AESI is an adverse event of scientific and medical concern specific to the compound or program, for which ongoing monitoring and rapid communication by the investigator may be appropriate.

Number of Participants With Clinically Significant Changes in Vital Sign Values

Timeframe: From start of study drug administration up to follow-up (up to Week 108)

Vital signs will include measurement of body temperature, respiratory rate, sitting blood pressure and pulse rate. Any clinically significant change in vital signs will be determined at the investigator's discretion.

Number of Participants With Clinically Significant Changes in Clinical Laboratory Values

Timeframe: From start of study drug administration up to follow-up (up to Week 108)

Laboratory parameters will include hematology, chemistry and urinalysis. Any clinically significant change in laboratory values will be determined at the investigator's discretion.

Percentage of Participants Achieving American College of Rheumatology (ACR20) Response at Weeks 24, 48, and 104

Timeframe: At Weeks 24, 48, and 104

ACR responses are the numerical measurement of improvement in multiple disease assessment criteria. It is a composite clinical outcome assessment (COA) measure that includes both clinician-reported outcome assessments (ClinROs) and patient-reported outcomes (PROs). An ACR20 response is defined as greater than or equal to (\>=) 20 percentage (%) improvement from baseline in both swollen joint count 66 joints (SJC66) and tender joint count 68 joints (TJC68), and \>=20% improvement from baseline in 3 of the following 5 assessments: Patient's global assessment (PtGA) of PsA pain; PtGA of PsA; physician's global assessment of disease activity (PGA) of PsA; participant's assessment of physical function as measured by health assessment questionnaire-disability index (HAQ-DI); high-sensitivity C-reactive protein (hsCRP).

Percentage of Participants Achieving ACR50 at Weeks 24, 48, and 104

Timeframe: At Weeks 24, 48, and 104

ACR responses are the numerical measurement of improvement in multiple disease assessment criteria. It is a composite COA measure that includes both ClinROs) and PROs. An ACR50 response is defined as \>=50% improvement from baseline in both SJC66 and TJC68, and \>=50% improvement from baseline in 3 of the following 5 assessments: PtGA of PsA pain; PtGA of PsA; PGA of PsA; participant's assessment of physical function as measured by HAQ-DI; hsCRP.

Percentage of Participants Achieving ACR70 at Weeks 24, 48, and 104

Timeframe: At Weeks 24, 48, and 104

ACR responses are the numerical measurement of improvement in multiple disease assessment criteria. It is a composite COA measure that includes both ClinROs) and PROs. An ACR70 response is defined as \>=70% improvement from baseline in both SJC66 and TJC68, and \>=70% improvement from baseline in 3 of the following 5 assessments: PtGA of PsA pain; PtGA of PsA; PGA of PsA; participant's assessment of physical function as measured by HAQ-DI; hsCRP.

Percentage of Participants Achieving Minimal Disease Activity (MDA) Status at Weeks 24, 48, and 104

Timeframe: At Weeks 24, 48, and 104

The MDA is defined as a composite outcome measure of 7 ClinROs and PROs used in PsA. Participants are classified as achieving MDA if they fulfil 5 of 7 outcome measures: TJC68 less than or equal to (\<=) 1, SJC66 \<=1, psoriasis area and severity index (PASI) score \<=1 or body surface area (BSA) affected by psoriasis (PsO) \<=3%, PtGA of PsA Pain score \<=15, PtGA of PsA score \<=20, HAQ-DI \<=0.5, and Leeds Enthesitis Index (LEI) \<=1.

Percentage of Participants Achieving >=75 % Improvement From Baseline in PASI Score at Weeks 24, 48, and 104

Timeframe: At Weeks 24, 48, and 104

A PASI-75 response is defined as \>=75% improvement in the PASI score from baseline. It is a ClinRO used to measure PsO severity, combining the percentage of surface area of skin affected with the severity of erythema, induration, and desquamation across four body regions: head, upper extremities, trunk, and lower extremities. Severity is scored on a 0-4 scale, with 0 indicating a complete lack of cutaneous involvement and 4 indicating the severest possible involvement. PASI scores range from 0 to 72, with \<=3 representing mild disease, \>=3 to 15 representing moderate disease, and \>=15 indicating severe disease.