Sivelestat for Acute Respiratory Distress Syndrome Due to COVID-19

Inclusion Criteria: * Age ≥18 years old * Confirmed SARS-CoV-2 infection as determined by Polymerase Chain Reaction (PCR) in sputum, nasopharyngeal swabs, or oropharyngeal swabs * Diagnosis of acute respiratory distress syndrome (ARDS) according to the Berlin Definition criteria * Onset of ARDS less than 72 hours before randomization * Written informed consent Exclusion Criteria: * ARDS potentially caused by extra-pulmonary reasons, including non-pulmonary sepsis, pancreatitis, multiple trauma and massive transfusion, etc. * Leukopenia (leukocyte count \<4,000/μL/) and/or thrombocytopenia (platelet count \<100,000/μL) * Significant hepatic dysfunction, defined as elevated AST and ALT ≥ 3 times the normal limits, or total bilirubin ≥ 1.5 mg/dL * Severe renal insufficiency with serum creatinine \> 3.0 mg/dL * History of moderate to severe chronic lung disease requiring home-based oxygen therapy, including chronic obstructive pulmonary disease (COPD), interstitial lung disease (ILD), asthma and bronchiectasis, etc. * Pre-existing peripheral nerve injury, spinal cord trauma, or neuromuscular disorder that may impair spontaneous ventilation (e.g., high cervical spinal cord injury, Guillain-Barré Syndrome, and myasthenia gravis, etc.) * Current diagnosis of pulmonary embolism * Coexisting multi-organ failure, affecting more than 3 systems * Combined with burn injury * Life expectancy less than 6 months (e.g., due to an an end-stage malignant disease) * Moribund and expected to die within 48 hours * Known allergy to sivelestat or any of the study drug excipients * Pregnancy or lactation, or the possibility of conception * Current or recent (last 3 months) participation in any other clinical trial