The goal of this clinical trial is to learn if drug JKN2403 works to treat moderate-to-severe COPD in adults. It will also learn about the safety and pharmacokinetic characteristics of drug JKN2403. The main questions it aims to answer are:

Does drug JKN2403 reduce the incidence of AECOPD or improve the quality of life or alleviate symptoms related to COPD?

Researchers will compare drug JKN2403 to a placebo (a look-alike substance that contains no drug) to see if drug JKN2403 works to treat moderate-to-severe COPD.

Participants will:

Take drug JKN2403 or a placebo every day for 24 weeks Visit the clinic once every four weeks for checkups and tests Keep a diary of their symptoms and the number of times they use a rescue inhaler

Inclusion Criteria:

• Written informed consent; able and willing to comply with study procedures.
• Adults with documented COPD diagnosis and medical history consistent with guideline criteria.
• Relevant exposure history consistent with COPD (e.g., smoking).
• On stable, guideline-based maintenance COPD therapy prior to randomization, per investigator judgment.
• Protocol-defined exacerbation history, symptom burden, and lung function at screening.

Exclusion Criteria:

• Current or past asthma, or other clinically significant respiratory disease that may confound assessment.
• Clinically significant uncontrolled comorbidities that increase risk or interfere with participation/outcomes.
• Immunodeficiency/immune dysregulation, active autoimmune disease requiring systemic immunosuppression, or significant opportunistic infection history.
• Active clinically significant infection or recent infection requiring systemic therapy; recent protocol-defined COPD exacerbation.
• Current/recent malignancy (except low-risk, adequately treated cancers per protocol) or clinically significant abnormal screening labs.
• Prohibited recent vaccines or therapies, prior relevant biologic/targeted therapy exposure, severe hypersensitivity to biologics/IMP, - pregnancy/breastfeeding, or inability to comply (including substance abuse), per investigator judgment.