TYK2/JAK1

Class

Oral TYK2/JAK1 inhibitor

TYK2 and JAK1 are members of the Janus kinase (JAK) family, enzymes that sit just inside the cell membrane and relay signals from cytokine receptors to the nucleus via the JAK-STAT pathway. When a cytokine binds its receptor, paired JAK enzymes phosphorylate each other and downstream STAT proteins, which then travel to the nucleus and switch on inflammatory genes. TYK2 is the principal JAK partner for interleukin-12, interleukin-23, and type I interferon receptors, cytokines central to psoriasis, psoriatic arthritis, and lupus. JAK1 partners with a broader set of receptors, including those for interleukin-4, interleukin-13, interleukin-6, and interferon-gamma, cytokines implicated in atopic dermatitis, rheumatoid arthritis, and other inflammatory diseases. An inhibitor that blocks both TYK2 and JAK1 dampens a wider swath of cytokine signaling than a TYK2-selective agent, extending potential efficacy across additional inflammatory pathways while remaining more selective than pan-JAK inhibitors that also hit JAK2 and JAK3. This positions dual TYK2/JAK1 inhibition as a middle ground: broader immunologic coverage than TYK2-only blockade, with an attempt to avoid some of the hematologic and infection-related liabilities associated with JAK2/JAK3 inhibition.