Conditions: Psoriasis
Allocation: RANDOMIZED | Intervention model: PARALLEL
Enrollment: 200
Healthy volunteers: no

Brief summary:
The study objectives are the following:

1. To evaluate the efficacy of 3 doses of XP23829 compared to placebo for the treatment of moderate-to-severe chronic plaque-type psoriasis.
2. To evaluate the safety and tolerability of XP23829 in subjects with psoriasis.
3. To evaluate the pharmacodynamics (PD) of XP23829 through immunological analysis of peripheral blood samples.

Detailed description:
Study Design : This is a , multi-center, double blind, placebo-controlled, phase 2 (dose-finding) efficacy and safety study in which subjects with moderate-to- severe chronic plaque-type psoriasis will be randomized in a 1:1:1:1 allocation ratio to 1 of 3 active doses of XP23829 or placebo. Approximately 50 subjects will be enrolled into each treatment group.

Study Periods: The study includes a 4-week screening phase, a 12-week treatment phase (with 9 weeks of XP23829 or placebo at the maintenance dose), and a 4-week observational post-treatment follow-up phase. A treatment-free follow-up period is designed to evaluate safety and disease relapse and rebound.

Specifically, the study periods are as follows:

1. Screening Phase: Weeks -4 through 0
2. Treatment phase included:

   1. Titration Phase: Weeks 1 through 3
   2. Double-Blind Maintenance Phase: Weeks 4 through 12
3. Post-treatment follow-up: Weeks 13 through 16

Efficacy assessments will be performed in the clinic at Baseline (Visit 2) and at the end of Weeks 2, 4, 8, 12, 14, and 16.

Patient-reported outcome measures will be assessed in the clinic at Baseline and at Week 12.

Blood samples for pharmacodynamic (PD) assessments will be collected at Baseline and at Weeks 4, 8, 12 and 16. PD assessments will be conducted in all subjects, with the intent of evaluating psoriasis-associated inflammatory markers.

Arms:
arm 1: After 4-week screening period, eligible subjects will be randomized to XP23829 400 mg QD for 12 weeks including titration period arm 2: After 4-week screening period, eligible subjects will be randomized to XP23829 800 mg QD for 12 weeks including titration period arm 3: After 4-week screening period, eligible subjects will be randomized to XP23829 400 mg BID for 12 weeks including titration period arm 4: After 4-week screening period, eligible subjects will be randomized to Placebo for 12 weeks

Interventions: intervention 1: XP23829 400 mg QD intervention 2: XP 23829 800 mg QD intervention 3: XP23829 400 mg BID intervention 4: Placebo
Intervention descriptions: intervention 1: active dose 1 intervention 2: active dose 2 intervention 3: active dose 3 intervention 4: control

Protocol document: