JAK1 and psoriasis: Tofacitinib, a pan-Jak inhibitor that predominantly targets Jak1 and Jak3, is currently approved for treatment of psoriatic arthritis at the dose of 5 mg twice daily; in phase 3 clinical trials for psoriasis, the 10 mg twice daily regimen was not inferior to etanercept [18,19], but FDA approval was declined based on long term safety issues.