Study of TJ003234 (Anti-GM-CSF Monoclonal Antibody) in Subjects With Severe Coronavirus Disease 2019 (COVID-19)

Inclusion Criteria: * Age: 18 years or older (including 18 years); male or female * Laboratory-confirmed SARS-CoV-2 or COVID-19 infection as determined by polymerase chain reaction (PCR) or other commercial or public health assay. * Bilateral lung infection confirmed by imaging. * Severe disease that meets one of the following conditions: (i) At rest, finger blood oxygen saturation ≤ 93% or PaO2/FiO2 ≤ 300 mmHg; (ii) Requiring non-invasive or invasive mechanical ventilation; OR (iii) Requiring high flow oxygen ≥ 15L/min * Hospitalized for no more than 5 calendar days at the time of screening Exclusion Criteria: * Any previous and/or current clinically significant disease or condition that has not been stable within 3 months prior to enrollment, or acute illness, planned medical/ surgical procedure, or any trauma that occurred within 2 weeks prior to enrollment. * Chronic obstructive pulmonary disease (COPD) patients requiring inhaled corticosteroid, long-acting beta-adrenergic agonists, long-acting anticholinergics, or long-term oxygen therapy (Part 1 only). * Pulmonary interstitial disease, pulmonary alveolar proteinosis, and pulmonary granulomatosis. * Cardiovascular event in the 3 months prior to study drug administration: acute myocardial infarction or unstable angina pectoris, severe arrhythmia (multiple sources of frequent ventricular premature beat, ventricular tachycardia and ventricular fibrillation); New York Heart Association Classification (NYHA): Class III-Class IV. * Blood system disorders or routine blood analysis test abnormalities: Hemoglobin \< 8 g/dL; Absolute neutrophil count (ANC) \<1500 × 109/L; Platelets \< 50 × 109/L. * Dependence on glucocorticoid treatment equivalent to methylprednisolone 2 mg/kg/ day or more or long-term use of anti-rejection or immunomodulatory drugs. * Subjects that have been on invasive mechanical ventilation for ≥120 hours at the time of dosing * Subjects that require ECMO. * Pregnant or breastfeeding females.