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.

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.

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.

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

The sPGA is an assessment by the investigator of the overall disease severity at the time of evaluation. Erythema (E), induration (I), and desquamation (D) are scored on a 5-point scale ranging from 0 (none) to 4 (severe). The sPGA composite score ranges from 0 to 4 and is calculated as Clear (0) = 0 for all three; Almost clear (1) = mean greater than (\>) 0, less than (\<) 1.5; Mild (2) = mean \>= 1.5, \<2.5; Moderate (3) = mean \>=2.5, \<3.5; and Severe (4) = mean \>=3.5. The percentage of participants achieving an sPGA of Clear (0) or Almost Clear (1) with a \>= 2-point decrease from baseline at Week 16 will be reported.

The PASI is a measure of the average redness, thickness and scaliness of psoriatic skin lesions (each graded on a 0 to 4 scale; 0 = none to 4 = very severe), weighted by the area of involvement (head, upper extremities, trunk, and lower extremities). The PASI score ranges from 0 to 72, with higher PASI scores denoting more severe disease activity (less than or equal to \[\<=\] 3 representing mild disease, \>= 3 to 15 representing moderate disease, and \>= 15 indicating severe disease). The PASI-75 is defined as 75% improvement from baseline in PASI score. The percentage of participants achieving \>= 75% improvement from baseline in PASI score at Week 16 will be reported.

Cmax of zasocitinib in plasma will be assessed.

Tmax of zasocitinib in plasma will be assessed.

AUC0-Last of zasocitinib in plasma will be assessed.

PASI is a measure of the average erythema, induration/infiltration, and desquamation/scaling of psoriatic skin lesions (each graded on a 0 to 4 scale; 0 = none to 4 = very severe), weighted by the area of involvement (head, upper extremities, trunk, and lower extremities). The PASI produces a numeric score that can range from 0 to 72 (less than or equal to \[\<=\] 3 representing mild disease, greater than or equal to \[\>=3\] to 15 representing moderate disease, and \>=15 indicating severe disease) with higher PASI scores denoting more severe disease activity. Percentage of participants showing 100 percentage (%) improvement in PASI score relative to baseline PASI score will be reported.

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 percent (%) 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 psoriatic arthritis (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 ACR20 response at Week 16 for zasocitinib Dose A and B compared to placebo will be reported.

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. A TEAE is defined as any event emerging or manifesting at or after the initiation of treatment with a trial intervention or medicinal product or any existing event that worsens in either intensity or frequency after exposure to the trial intervention. 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.

HiSCR75 is defined as at least a 75% reduction in the total abscess and inflammatory nodule (AN) count with no increase in abscess or draining tunnel count relative to baseline.

The vitiligo area scoring index (VASI) is a validated scoring method used to assess the areas of depigmentation due to vitiligo. The F-VASI includes contributions from the face, with a possible range from 0 to 3.5, with higher scores indicating more severe disease. Negative changes from baseline indicate improvement. This is recorded as either Yes (achieved \>= 75% improvement) or No (did not achieve).

TEAE is defined as any event emerging or manifesting at or after the initiation of treatment with a study intervention or medicinal product or any existing event that worsens in either intensity or frequency following exposure to the study intervention or medicinal product. 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.

Vital sign values include body temperature, respiratory rate, sitting blood pressure (systolic and diastolic, resting more than 5 minutes), pulse (beats per minute). Clinical significance of vital signs will be determined at the investigator's discretion.

Laboratory parameters include hematology, clinical chemistry and urinalysis. Clinical significance of laboratory values will be determined at the investigator's discretion.

ECGs will be performed with the participant in the supine or semi-supine position and after resting comfortably for at least 5 minutes. Clinical significance of 12-lead ECG values will be determined at the investigator's discretion.