Recombinant Human Angiotensin-converting Enzyme 2 (rhACE2) as a Treatment for Patients With COVID-19

Inclusion Criteria: 1. Laboratory diagnosis: * Respiratory specimen is positive for SARS-CoV-2 nucleic acid by RT-PCR; OR, * The viral gene sequencing of the respiratory specimen is highly homologous to known novel coronavirus. 2. Fever: Axillary temperature \>37.3℃ 3. Respiratory variables (meets one of the following criteria): * Respiratory rate: RR ≥25 breaths/min * Oxygen saturation ≤93% at rest on room air * PaO2/FiO2 ≤300 mmHg（1 mmHg=0.133 KPa） * Pulmonary imaging showed that the lesions progressed more than 50% within 24-48 hours, and the patients were managed as severe 4. HBsAg negative, or HBV DNA ≤10\^4 copy/ml if HBsAg positive; anti-HCV negative; HIV negative two weeks prior to signed Informed Consent Form (ICF) 5. Appropriate ethics approval and 6. ICF Exclusion Criteria: * Age \<18 years; Age \>80 years * Pregnant or breast feeding woman or with positive pregnancy test result * P/F \<100 mmHg * Moribund condition (death likely in days) or not expected to survive for \>7 days * Refusal by attending MD * Not hemodynamically stable in the preceding 4 hours (MAP ≤65 mmHg, or SAP \<90 mmHg, DAP \<60 mmHg, vasoactive agents are required) * Patient on invasive mechanical ventilation or ECMO * Patient in other therapeutic clinical trial within 30 days before ICF * Receive any other ACE inhibitors (ACEI), angiotensin-receptor blockers (ARB) treatment within 7 days before ICF * Chronic immunosuppression: current autoimmune diseases or patients who received immunotherapy within 30 days before ICF * Hematologic malignancy (lymphoma, leukemia, multiple myeloma) * Other patient characteristics (not thought to be related to underlying COVID-19) that portend a very poor prognosis (e.g, severe liver failure, and ect) * Known allergy to study drug or its ingredients related to renin-angiotensin system (RAS), or frequent and/or severe allergic reactions with multiple medications * Other uncontrolled diseases, as judged by investigators * Body weight ≥85 kg