Evaluate the Safety and Pharmacokinetics/Pharmacodynamics of HS-20118

The study will be conducted in 2 parts (SAD for Part 1 and MAD for Part2). Part 1 is a single-center, randomized, double-blind, placebo-controlled, SAD study to evaluate the safety, tolerability, immunogenicity, and PK of HS-20118 after a single oral dose in healthy participants. Part 1 will consist of 5 cohorts, i.e., X1 mg, X2 mg, X3 mg, X4 mg, and X5 mg dose cohorts (each cohort will include 3 participants to receive placebo). There will be no restriction on the male-to-female ratio. Each cohort will include 12 participants (HS-20118:placebo = 9:3), with a total of 60 participants. Participants will undergo PK blood sampling, ADA blood sampling, PD blood sampling and safety examinations during the study. Part 2 is a multi-center, randomized, double-blind, placebo-controlled, MAD study to evaluate the safety, tolerability, immunogenicity, PK, and PD of HS-20118 after multiple oral doses in patients with moderate to severe plaque psoriasis. Part 2 will tentatively consist of 6 cohorts ( HS-20118 vs placebo = 9:3), i.e., (1) A1 mg, (2) A2 mg, (3) A3 mg, (4) A4 mg, (5) A5 mg, (6) A6 mg. Each cohort will include 12 participants (HS-20118:placebo = 9:3), with a total of 72 participants. There will be no restriction on the male-to-female ratio. Participants will undergo PK blood sampling, ADA blood sampling, PD blood sampling and safety examinations during the study.