This clinical trial is a multicenter, randomized, double-blind, placebo-controlled, parallel-group dose-response phase 2 clinical trial study to evaluate the efficacy and safety of Bronpass Tab. in 96 patients with chronic obstructive pulmonary disease.

This study is to prove that Bronpass Tab. is superior in clinical efficacy and safety in improving COPD symptoms compared to placebo for 12 weeks in patients suffering from chronic obstructive pulmonary disease.

Inclusion Criteria:

1. 40 years ≤ age

2. Patients who are diagnosed as COPD (based on the definition in the Korean Society of Tuberculosis and Respiratory Diseases COPD Guidelines)

3. Patients who meet all of the following criteria at the screening test

   • FEV1/FVC < 0.70 after bronchodilator administration
   • 30% ≤ FEV1 < 80% predicted after bronchodilator administration
   • Cough or sputum-related score on the CAT ≥ 3

4. Current or former smokers with a smoking history of 10 pack-years or more at screening.

5. Patients who have listened to a detailed explanation of this clinical trial, fully understand it, and voluntarily provide written consent to participate.

Exclusion Criteria:

1. Patients with a current medical history of asthma (However, patients previously diagnosed as asthma who have recovered and currently have a diagnosis of COPD are eligible for participation.)
2. Patients with a medical history of respiratory diseases other than COPD
3. Patients who have undergone lung volume reduction surgery.
4. Patients with a history of lung transplantation.
5. Patients with a history of respiratory infections within 4 weeks prior to screening
6. Patients with a history of moderate or severe acute exacerbation within 4 weeks prior to screening.
7. Pregnant or lactating women.
8. Patients who are considered ineligible for this clinical trial due to other reasons as judged by the investigator.