TYK2

Class

TYK2 inhibitor

TYK2 (tyrosine kinase 2) is a member of the Janus kinase (JAK) family, a group of enzymes that sit just inside the cell membrane and relay signals from cytokine receptors to the nucleus. TYK2 specifically partners with receptors for interleukin-12 (IL-12), interleukin-23 (IL-23), and type I interferons—cytokines that drive many of the inflammatory and autoimmune processes seen in psoriasis, psoriatic arthritis, inflammatory bowel disease, and lupus. When these cytokines bind their receptors, TYK2 helps activate STAT transcription factors, which switch on genes that sustain inflammation. Blocking TYK2 dampens this signaling cascade, reducing the downstream inflammatory output without shutting down cytokine signaling entirely elsewhere in the body. What distinguishes many newer TYK2 inhibitors is that they bind a regulatory region of the enzyme called the pseudokinase (JH2) domain rather than its catalytic site, allowing selective inhibition of TYK2 while sparing closely related JAK1, JAK2, and JAK3, which govern blood cell production, growth factor signaling, and broader immune function. This selectivity is the biological rationale for developing TYK2-specific agents: it aims to preserve efficacy against IL-12/23 and interferon-driven disease while avoiding some of the broader immunosuppressive and hematologic effects associated with less selective JAK inhibition.