Novel TYK2 Inhibitors with an N -(Methyl- d 3 )pyridazine-3-carboxamide Skeleton for the Treatment of Autoimmune Diseases.

Tyrosine kinase 2 (TYK2) mediates the interleukin-23 (IL-23), IL-12, and type I interferon (IFN)-driven signal responses that are critical in autoimmune diseases. Here, a series of novel derivatives with an -(methyl- )pyridazine-3-carboxamide skeleton that bind to the TYK2 pseudokinase domain were designed, synthesized, and evaluated. Among them, compound demonstrated more excellent inhibitory potency against STAT3 phosphorylation than the positive control deucravacitinib. In addition to JAK isoform selectivity, compound exhibited good and pharmacokinetic properties. Furthermore, compound was orally highly effective in both IL-23-driven acanthosis and anti-CD40-induced colitis models. Together, these findings support compound as a promising candidate for therapeutic applications in autoimmune diseases.