Tyrosine Kinase 2 Inhibition With Zasocitinib (TAK-279) in Psoriasis: A Randomized Clinical Trial.

New, effective, and well-tolerated oral therapies are needed for treating psoriasis. Zasocitinib, a highly selective allosteric tyrosine kinase 2 (TYK2) inhibitor, is a potential new oral treatment for this disease. To assess the efficacy, safety, and tolerability of zasocitinib in patients with moderate to severe plaque psoriasis. This phase 2b, randomized, double-blind, placebo-controlled, multiple-dose randomized clinical trial was conducted from August 11, 2021, to September 12, 2022, at 47 centers in the US and 8 in Canada. The study included a 12-week treatment period and a 4-week follow-up period. Key eligibility criteria for participants included age 18 to 70 years; a Psoriasis Area and Severity Index (PASI) score of 12 or greater; a Physician's Global Assessment score of 3 or greater; and a body surface area covered by plaque psoriasis of 10% or greater. Of 287 patients randomized, 259 (90.2%) received at least 1 dose of study treatment. Patients were randomly assigned (1:1:1:1:1) to receive zasocitinib at 2, 5, 15, or 30 mg or placebo orally, once daily, for 12 weeks. The primary efficacy end point was the proportion of patients achieving 75% or greater improvement in PASI score (PASI 75) at week 12. Secondary efficacy end points included PASI 90 and 100 responses. Safety was also assessed. In total, 259 patients were randomized and received treatment (mean [SD] age, 47 [13] years; 82 women [32%]). At week 12, PASI 75 was achieved for 9 (18%), 23 (44%), 36 (68%), and 35 (67%) patients receiving zasocitinib at 2, 5, 15, and 30 mg, respectively, and 3 patients (6%) receiving placebo. PASI 90 responses were consistent with PASI 75. PASI 100 demonstrated a dose response at all doses, with 17 patients (33%) achieving PASI 100 with zasocitinib, 30 mg. Treatment-emergent adverse events occurred for 23 patients (44%) receiving placebo and 28 (53%) to 31 (62%) patients receiving the 4 different doses of zasocitinib, with no dose dependency and no clinically meaningful longitudinal differences in laboratory parameters. This randomized clinical trial found that potent and selective inhibition of TYK2 with zasocitinib at oral doses of 5 mg or more once daily resulted in greater skin clearance than placebo over 12 weeks. ClinicalTrials.gov Identifier: NCT04999839.