Summary: TQC3721 suspension for inhalation is a PDE3/4 inhibitor developed by Chia Tai Tianqing Pharmaceutical Group Co., LTD., which can simultaneously achieve bronchial smooth muscle relaxation and anti-inflammatory effects. This is a randomized, double-blind, placebo-parallel, phase II trial of the efficacy and safety of inhaled TQC3721 suspension/placebo at different doses in patients with moderate to ...