Evaluate the Efficacy and Safety of TQC2731 Injection in Patients With Severe Asthma.

This is a phase II, multicenter, double-blind, randomized, parallel group, placebo-controlled clinical study to evaluate the effect of three doses of TQC2731 on Annualized Asthma Exacerbation Rates(AAER) in adult subjects with poor control of severe asthma. It is estimated that 220 subjects will be included. The subjects will receive TQC2731 (70 mg Q4w, 210 mg Q4w, 420 mg Q4w) or placebo (Q4w) administered by Subcutaneous (SC) in the ratio of 1:1:1:1. The study comprised a 5 to 6-week screening period, a 52-week treatment period and a 12-week follow-up period. During the treatment period, the study drug will be administered from day 0 until week 48. The study drug was not administered at the 52nd week.