Evaluation of Changes in Laboratory Parameters from a Phase 2b Trial of Zasocitinib (TAK-279), an Oral, Selective TYK2 Inhibitor, in Patients with Moderate-to-Severe Plaque Psoriasis

Background: Zasocitinib (TAK-279) is an oral, allosteric, and highly selective tyrosine kinase 2 inhibitor. In a recent phase 2b trial (NCT04999839), more patients with moderate-to-severe plaque psoriasis treated with zasocitinib 15 and 30 mg once daily achieved 75% improvement in the psoriasis area and severity index at Week 12 (primary endpoint) than those receiving placebo (PBO; p < 0.001). Here we report an assessment of laboratory parameters from this study. Methods: In this randomized, multicenter, double-blinded, PBO-controlled study, adults with moderate-to-severe plaque psoriasis were randomized 1:1:1:1:1 to receive oral zasocitinib (2, 5, 15 or 30 mg) or PBO once daily for 12 weeks. The safety analysis set included all patients who received ≥1 dose of the assigned study treatment. Laboratory parameters assessed throughout the trial included creatine kinase (CK), as well as hematologic (neutrophils, lymphocytes, hemoglobin, platelets), hepatic and renal (alanine aminotransferase, aspartate aminotransferase, bilirubin, creatinine, estimated glomerular filtration rate), and lipid (cholesterol, triglycerides) parameters. Results: In total, 259 patients were included in the safety analysis set. Longitudinal changes in all laboratory parameters were generally similar in the PBO and zasocitinib groups. Mean values of most laboratory parameters remained within normal ranges during the study. There was no relationship between zasocitinib treatment and cytopenia. Some CK elevations were observed in both the PBO and zasocitinib groups, but most were transient or reversible and of Common Terminology Criteria for Adverse Events Grade 1 or 2 (Grade ≥2 events occurred in 2 [3.8%], 2 [4.0%], 6 [11.5%], 4 [7.5%] and 3 [5.8%] patients, in the PBO, and 2, 5, 15 and 30 mg groups, respectively), and were not associated with rhabdomyolysis. Mean triglyceride values were slightly higher than normal ranges at baseline and Week 12 in all treatment groups, including PBO, and were mainly asymptomatic, mild-to-moderate elevations. These changes were not accompanied by increases in serum cholesterol levels. Conclusion: Zasocitinib treatment did not result in adverse changes in hematologic, hepatic, renal or lipid parameters that are associated with Janus kinase (JAK) inhibition, suggesting that the mechanism of action of zasocitinib is distinct from that of JAK1/2/3 inhibition. Further phase 3 studies of zasocitinib in psoriasis are ongoing to confirm these observations (NCT06088043; NCT06108544).