Study to Evaluate the Safety and Efficacy of Jaktinib in Adults With Alopecia Areata

This is a multi-center Phase 3 study to evaluate the safety and effectiveness of an investigational study drug (called Jaktinib) in adults (≥18 years and \<65 years) who have 50% or greater scalp hair loss. The study is placebo-controlled, meaning that some patients entering the study will not receive active study drug but will receive tablets with no active ingredients (a placebo). It is double-blinded, meaning that the Sponsor, the study doctors, the staff, and the patients will not know whether a patient is on active study drug (or the dose) or placebo.