• The subject or their legally acceptable representative (LAR) has voluntarily signed the informed consent form (ICF) prior to any study-related procedures, and the subject is willing and able to comply with all study requirements, restrictions, and procedures. If consent is provided by an LAR for a subject with limited or no capacity to consent, re-consenting may be performed if the subject regains capacity.

• Aged 18 to 85 years.

• Diagnosis of CAP

• Prior to screening, the subject has been receiving standard-of-care treatment for pneumonia in a medical institution, including at least 3 days of intravenous (IV) anti-infective therapy, with no clinical improvement.

• Chest CT showing multi-lobar infiltrates, and for subjects not receiving invasive mechanical ventilation, an oxygenation index (PaO2/FiO2 ratio) between 100 and 300 mmHg.

• Expected to require continued hospitalization for at least 7 days from the time of signing the ICF.

• Baseline NIAID-OS 8-point scale score of 5 points and transcutaneous oxygen saturation ≤ 93% without oxygen inhalation, 6 points or 7points. (5 points refer to hospitalization with oxygen therapy; 6 points refer to hospitalization with high flow oxygen therapy or non-invasive mechanical ventilation. 7 points refer to hospitalization with invasive mechanical ventilation).High oxygen flow refers to ≥ 4 L/min.)

• With ≥ 1 high risk factors including chronic obstructive pulmonary disease (COPD), pulmonary fibrosis, type 2 diabetes, chronic kidney disease, coronary heart disease, age ≥ 65 years, moderate obesity (body mass index\>32.5kg/m2), etc.

• Participants of women of childbearing potential(WOCBP) and male participants with WOCBP partners must agree to use one or more effective contraceptive methods during the treatment period and until 90 days after the last administration.