To evaluate the efficacy, safety and tolerability of STSA-1002 injection in patients with acute respiratory distress syndrome

Inclusion Criteria:

1. 18 years old ≤ ≤ 85 years old;
2. laboratory tests results indicate respiratory viral infection;
3. Fulfills the diagnostic criteria for A New Global Definition of Acute Respiratory Distress Syndrome ;
4. The time from the onset of respiratory infection-related symptoms to randomization is ≤ 12 days (for patients without invasive mechanical ventilation)/)/≤ 14 days (for patients with invasive mechanical ventilation); Or worsening of respiratory infection-related symptoms within ≤7 days from randomization;
5. PaO2/FiO2≤200mmHg;
6. The subjects (including their partners) have no plans to have children during the trial and within 3 months after the last dose, and agree to take appropriate and effective contraceptive measures (such as contraceptive pills, condoms, etc.);
7. Volunteer to participate in the trial and sign the informed consent form.

Exclusion Criteria:

1. ECMO before the first dose;
2. According to the comprehensive judgment of the investigator, the patient's condition improved within 48 hours before the first dose;
3. The expected survival period is no more than 24 hours or cardiac arrest occurred 4 weeks before the first dosedose;
4. Patients with stroke or acute coronary syndrome within 3 months before randomization;
5. Patients with cardiogenic pulmonary edema, which is the main cause of respiratory failure; New York Heart Classification III-IV patients;
6. Severe chronic respiratory failure;
7. Known active pulmonary tuberculosis;
8. Combined with liver insufficiency
9. Long-term dialysis and/or known severe renal impairment Cytomegalovirus infection;
10. Known HIV infection with CD4+ T-lymphocyte count < 200 cells/μL;
11. Organ transplant patients;
12. Patients who received radiotherapy and chemotherapy in the past 1 years or the malignant tumor is still in the active phase;
13. Septic shock
14. Absolute neutrophil count is less than 0.5×109/L;
15. Hemoglobin is less than 60g/L, or the researcher judges that there is active gastrointestinal bleeding;
16. Severe underlying diseases with poor compliance with basic treatment;17. Pregnant or lactating women;

18. Participated in new drug clinical trials and medication within 3 months before screening; 19. Allergic or allergic to any component of the trial drug and its excipients (such as allergic to two or more drugs); 20. Other diseases or conditions that the investigator considers unsuitable for participation in this trial.