Primary Objective: To evaluate the safety and tolerability of human umbilical cord mesenchymal stem cell injection in the treatment of moderate/severe acute respiratory distress syndrome.Secondary Objectives: To explore the efficacy and appropriate dosage of human umbilical cord mesenchymal stem cell injection in the treatment of moderate/severe acute respiratory distress syndrome.Exploratory Objective: To explore the immunogenicity and pharmacokinetic/pharmacodynamic (PK/PD) characteristics of a single dose of human umbilical cord mesenchymal stem cell injection in patients with moderate/severe acute respiratory distress syndrome.
Male or female patients aged 18 to 80 years (inclusive).
Diagnosis of moderate or severe Acute Respiratory Distress Syndrome (ARDS) according to A New Global Definition of Acute Respiratory Distress Syndrome, with an infectious etiology.
No improvement after 24 hours of conventional clinical treatment (defined as a persistent PaO₂/FiO₂ ratio ≤200 mmHg or a decrease from >200 mmHg to ≤200 mmHg after 24 hours of conventional supportive therapy; for severe ARDS, this assessment period may be shortened to 8 hours).
Ability to fully understand the nature of the study and voluntarily provide written informed consent.
Patients with ARDS caused by COVID-19 infection.
Patients currently suffering from hepatitis B, hepatitis C, active or latent tuberculosis, AIDS, syphilis, immunodeficiency disorders, or other immune system diseases.
Presence of severe cardiovascular diseases at screening, including:Cardiac function classification of NYHA class III or higher.Uncontrolled myocarditis or valvular disease.Malignant arrhythmia requiring pharmacological treatment.
Abnormal liver or renal function at screening meeting any of the following criteria:ALT or AST ≥ 5 × ULN, or total bilirubin ≥ 3 × ULN.Serum creatinine ≥ 3 × ULN, or patients currently undergoing renal replacement therapy (CRRT).