Tyrosine kinase 2 (TYK2) is an intracellular tyrosine kinase protein that plays a vital role in immune responses in both innate and adaptive immunity. TYK2 as a target has significant effects on both IL-12/23 pathway and type Ⅰ interferon pathway. Both pathways have been implicated in various immune-mediated diseases. Targeting inhibition of TYK2 and its associated cytokine pathways has been validated in treating autoimmune diseases including psoriasis, systemic lupus erythematosus, etc.

AC-201, an allosteric TYK2/JAK1 inhibitor binding to JH2 domain, effectively inhibits TYK2/JAK1 activity through allosteric mechanisms. In Phase I study, AC-201 was safe and well-tolerated with no serious adverse events in healthy subjects. Phase II clinical trial of AC-201 in patients with moderate to severe plaque psoriasis is currently undergoing.