Evaluation of the Inhaled TQC3721 Suspension in Patients With Moderate-to-Severe Chronic Obstructive Pulmonary Disease

Inclusion Criteria: Cohort A: * Subjects who have completed the TQC3721-III-01 clinical trial, demonstrated good medication compliance during the 24-week treatment period as required by the protocol (with no major protocol deviations related to medication compliance), and experienced no treatment-related SAEs. * Sign the informed consent form and fully understand the trial content, procedures, and potential adverse reactions. * Willing and able to comply with the trial arrangements and to use the nebulizer correctly. * Subjects have no pregnancy plans from screening until at least 1 month after the last dose of the investigational drug and voluntarily adopt effective contraception measures. * Patients with a clear clinical history and related symptoms of COPD (meeting the diagnostic criteria for COPD as outlined in the Chinese Guidelines for the Diagnosis and Management of Chronic Obstructive Pulmonary Disease (2021 Revised Edition)). Cohort B: * Sign the informed consent form prior to screening and fully understand the trial content, procedures, and potential adverse reactions. * Willing and able to comply with the trial arrangements and to use the nebulizer correctly. * Aged between 40 and 80 years (inclusive), both male and female subjects are eligible. * Subjects have no pregnancy plans from screening until at least 1 month after the last dose of the investigational drug and voluntarily adopt effective contraception measures. * Patients with a clear clinical history and related symptoms of COPD prior to screening (meeting the diagnostic criteria for COPD as outlined in the Chinese Guidelines for the Diagnosis and Management of Chronic Obstructive Pulmonary Disease (2021 Revised Edition)). * At the screening visit (V1), post-bronchodilator (salbutamol 4 puffs) lung function shows an FEV1/FVC ratio \<0.7, and 30% predicted value ≤ FEV1 \< 80% predicted value. * A modified Medical Research Council (mMRC) dyspnea scale score of ≥1 at screening (V1). * Subjects on single or dual bronchodilator background therapy (with or without an Inhaled Corticosteroid component) must have been on stable treatment for at least 2 weeks prior to screening. * Clinically stable COPD (no moderate or severe COPD exacerbations) within 4 weeks prior to the screening visit (Visit V1). * Smoking history of ≥10 pack-years (pack-years: packs per day \* years of smoking, e.g., 1 pack of 20 cigarettes per day for 10 years, or 10 cigarettes per day for 20 years) OR a history of exposure to biomass fuels. Exclusion Criteria: Cohort A: * History of life-threatening chronic obstructive pulmonary disease (COPD) (e.g., prior intensive care unit admission or requiring intubation). * Presence of other clinically significant respiratory diseases, such as alpha-1 antitrypsin deficiency, active pulmonary infection, bronchiectasis, interstitial lung disease, pulmonary arterial hypertension, or asthma. * Any other systemic disease deemed by the investigator to be clinically significant and not adequately controlled at present. * History or current evidence of clinically significant cardiovascular or cerebrovascular disease, specifically including: Myocardial infarction, unstable angina, or stroke within the past 6 months; Unstable or life-threatening arrhythmia requiring intervention within the past 3 months; New York Heart Association (NYHA) Functional Class III or IV heart failure. * Poorly controlled hypertension despite medication (systolic blood pressure ≥160 mmHg and/or diastolic blood pressure ≥100 mmHg). * Poorly controlled type 2 diabetes mellitus (e.g., fasting blood glucose \>10 mmol/L). * Planned surgery before the end of the study. * History of malignancy in any organ system within the past 5 years (except for non-metastatic basal cell or squamous cell carcinoma of the skin, or carcinoma in situ of the cervix, with complete remission for \>5 years prior to screening). * Clinically significant laboratory abnormalities at the screening visit (V1) as determined by the investigator, including alanine aminotransferase (ALT) or aspartate aminotransferase (AST) \>2 × upper limit of normal (ULN), alkaline phosphatase \>2 × ULN, or total bilirubin \>1.5 × ULN. * Female subjects who are pregnant, breastfeeding, or planning to become pregnant during the study. * Any other condition considered by the investigator as unsuitable for participation in the study. Cohort B: * History of life-threatening COPD (e.g., prior intensive care unit admission or requiring intubation). * Experienced a COPD exacerbation requiring systemic corticosteroids within 3 months prior to the screening visit (V1). * One or more hospitalizations due to COPD exacerbation or pneumonia within 3 months prior to screening. * Presence of other clinically significant respiratory diseases, as specified in Criterion A.2. * Chest computed tomography (CT) scan showing clinically significant abnormalities not attributable to COPD and judged by the investigator to potentially affect trial evaluation or subject safety. * Use of oral theophylline or its derivatives for COPD treatment within 1 week prior to the screening visit (V1). * Prior treatment with TQC3721. * Any other systemic disease deemed by the investigator to be clinically significant and not adequately controlled at present. * History or current evidence of clinically significant cardiovascular or cerebrovascular disease, as specified in Criteria A.4. * Poorly controlled hypertension, as specified in Criterion A.5. * Poorly controlled type 2 diabetes mellitus, as specified in Criterion A.6. * Major surgery (requiring general anesthesia) within 8 weeks prior to the screening visit (V1) with incomplete recovery, or planned surgery before the end of the study. * Clinically significant laboratory abnormalities at screening, as specified in Criterion A.9. * Requirement for long-term daily oxygen therapy (defined as cumulative use \>12 hours per day). * Female subjects who are pregnant, breastfeeding, o