This is a randomized, multicenter, double-blind, placebo-controlled, parallel-designed phase 2 clinical trial to evaluate the efficacy, safety and pharmacokinetic (PK) characteristics of HW091077 in Chinese adult subjects with refractory chronic cough or unexplained chronic cough (RCC/UCC).

Inclusion Criteria:

• Aged between 18 and 80 years;
• Diagnosed with refractory chronic cough or unexplained chronic cough, with a cough lasting for ≥1 year;
• Chest CT at screening shows no abnormalities that the investigator believes may lead to chronic cough;
• Cough severity VAS score ≥40 mm ;
• Female participants of childbearing potential must have a negative pregnancy test and must not be breastfeeding; male and female participants must have no plans for pregnancy during the entire clinical trial and within 6 months after the last dose, and agree to use medically accepted reliable contraceptive methods during the trial and within 6 months after the last dose;
• Fully understand the study, voluntarily sign the informed consent form, and be able to comply with the study procedures and follow-up requirements.

Exclusion Criteria:

• Currently smoking, or having quit smoking within 12 months prior to screening;
• A smoking history of >20 pack-years;
• Ongoing exposure to inhaled toxic substances within 12 months prior to screening or currently;
• A history of drug abuse or alcoholism (weekly alcohol consumption of 14 units of alcohol: 1 unit = 285 mL of beer, or 25 mL of spirits, or 100 mL of wine);
• Diagnosed with chronic obstructive pulmonary disease (COPD), chronic bronchitis, cystic fibrosis, pulmonary sarcoidosis, idiopathic pulmonary fibrosis, bronchial asthma (except for cough variant asthma), or other airway/respiratory diseases that may affect coughing;
• Respiratory tract infection or significant changes in lung status within 4 weeks prior to screening;
• FEV1/FVC)<60%;
• Clinically significant electrocardiogram abnormalities, such as QTc interval ≥450 ms, long QT syndrome, etc.;
• Use of angiotensin-converting enzyme inhibitors (ACEIs) within 3 months prior to screening;
• Plans to initiate new treatment for RCC/UCC during the trial period;
• Taste disturbance within 1 month prior to screening;
• Use of any P2X3 receptor antagonist within 1 year prior to screening;