LW402 was rapidly absorbed (median t<sub>max</sub>: 0.42-1.0 hours), with slightly super-proportional exposure and minimal accumulation, and preferentially inhibited JAK1-mediated signaling.<h4>Discussion</h4>LW402's favorable safety profile, predictable PK characteristics, and selective JAK1 inhibition collectively support its continued development for the treatment of autoimmune diseases.<h4>Clinical trial registration</h4>http://www.chinadrugtrials.org.cn, identifier CTR20201897. The gene discussed is JAK1; the disease is autoimmune disease.