This study is a randomized, double-blind, placebo-controlled, multi-center phase II clinical study conducted in China to compare the efficacy and safety of two different dose groups of AK3280 in IPF patients compared to the placebo control group.

This study is a randomized, double-blind, placebo-controlled, multi-center phase II clinical study conducted in China to compare the efficacy and safety of two different dose groups of AK3280 in IPF patients compared to the placebo control group. One hundred and five IPF patients who have completed the screening assessment and meet the enrollment requirements will participate in this study and be randomized into 3 treatment groups in a 1:1:1 (35:35:35) ratio: AK3280 200 mg group, AK3280 100 mg group and placebo group; the frequency of medication for each treatment group is twice a day (BID).

This study is divided into a main study and an extension study. The main study includes a 4-week screening period, a 24-week medication observation period, and a 4-week safety follow-up period. The extension study includes a 24-week medication observation period and a 4-week safety follow-up period.

Inclusion Criteria:

• 1. Patients who sign the informed consent form before participating in the study.

  2. Patients who understand the importance of complying with the study medication regulations and completing all assessments on time during the entire study process, and agree to strictly abide by the protocol regulations, including the restrictions on concomitant medication during the study process.

  3. Patients aged ≥40 years and ≤80 years at the time of enrollment. 4. Patients diagnosed with IPF within five years before screening (but at least 6 months before the first medication) who meet the standards of the latest American Thoracic Society/European Respiratory Society/Japanese Respiratory Society/Latin American Thoracic Association (ATS/ERS/JRS/ALAT) 2018 guidelines. The diagnosis of IPF needs to be reconfirmed during the screening assessment.

  5. Patients who have completed the HRCT central review assessment during the screening period or completed the HRCT central assessment within 12 months before screening to confirm the diagnosis of IPF. If the patient is unable to provide pulmonary surgical biopsy pathology, the HRCT image must conform to usual interstitial pneumonia to confirm the diagnosis of IPF. Patients who have undergone pulmonary surgical biopsy as part of the initial diagnosis must submit their pathological slices for central review and assessment.

  6. Patients who cannot tolerate pirfenidone or nintedanib and have received no more than 8 consecutive weeks of regular nintedanib or pirfenidone treatment, or patients who, the investigator considers, are not suitable to receive pirfenidone or nintedanib treatment, or patients who refuse to receive pirfenidone or nintedanib treatment.

  7. Patients with %FVC between 50% and 90% (inclusive) at screening, and hemoglobin-corrected %DLco between 30% and 90% (inclusive).

  8. Patients with relatively stable basic lung function, manifested by a <10% relative difference in FVC values at the screening day and the day before administration. The calculation formula is: (FVC value (L) at screening - FVC value (L) one day before administration) )/(FVC value (L) at screening )× 100% And patients who have no other clinically significant acute exacerbations of IPF determined by the investigators at the screening day and the day before administration.

  9. Patients whose 6MWT distance is ≥100 m without auxiliary support.

Exclusion Criteria:

• 1. Patients suffering from interstitial pneumonia of other known causes.

  2. Patients who plan to undergo lung transplantation within 6 months after screening.

  3. Patients suffering from other clinically significant lung diseases (such as asthma, chronic obstructive pulmonary disease, etc.) in addition to IPF.

  4. Patients suffering from any disease whose life expectancy is less than 12 months other than IPF; or patients requiring long-term medical care, or with limited self-care ability, or the investigator believes that it may affect the patient's participation in the completion of this clinical study, or completion of study-related examinations, or affect safety assessments or efficacy assessments.

  5. Patients who have any evidence or clinically significant adverse physical conditions or abnormal examinations (physical examination, vital signs, ECG or laboratory test abnormalities, etc.) that the investigator believes may affect patient safety or the study endpoint assessments.

  6. Patients with forced expiratory volume in the first second (FEV1)/FVC ratio <0.7 after the use of bronchodilators at screening.

  7. Patients with a positive bronchodilation test, manifested as a ≥ 12% increase in FEV1 and an absolute increase≥200 mL in FEV1 after the use of bronchodilators.

  8. Patients with peripheral capillary blood oxygen saturation (SpO2) at rest <88%.

  9. Patients suffering from any clinically diagnosed connective tissue disease, including but not limited to scleroderma, polymyositis/dermatomyositis, systemic lupus erythematosus, and rheumatoid arthritis.

  10. Patients with New York Heart Association (NYHA) heart function classification of Class III-IV.

  11. Renal insufficiency or a history of kidney injury; or creatinine clearance <60 mL/min, calculated using the Cockcroft-Gault formula; or patients with end-stage renal disease requiring dialysis.

  12. Patients with diabetes that is not stably controlled at the time of screening (glycated hemoglobin [HbA1c]> 10%).

  13. Patients hospitalized due to acute exacerbation of IPF within 4 weeks before screening or during the screening period.

  14. Patients currently suffering from malignant tumors or who have been assessed to possibly have malignant tumors (except for localized basal cell carcinoma of the skin or cervical cancer in situ).

  15. Local or systemic infection requiring: i. Hospitalization for ≥24 hours within 4 weeks before screening or during the screening period ii. Use of antibiotics (intravenous, intramuscular injection, oral or inhalation) within 4 weeks before screening or during the screening period

  16. Acute phase of severe lung infection

  17. Active tuberculosis requiring treatment within 12 months before screening

  18. Patients with known immunodeficiency, including but not limited to HIV infection

  19. Patients with acute or chronic hepatitis or patients with known liver cirrhosis

  20. Any of the following circumstances: i. Aspartate aminotransferase (AST) ≥ 2 × upper limit of normal ii. Alanine aminotransferase (ALT) ≥ 2 × upper limit of normal iii. Alkaline phosphatase (ALP) ≥ 2 × upper limit of normal iv. Total bilirubin ≥1.5 × upper limit of normal v. Severe liver damage or end-stage liver disease

  21. Patients who have received any of the following chronic treatment within 4 weeks before randomization or within 5 half-lives (whichever is longer): i. Immunosuppressive or immunomodulatory therapy (such as azathioprine, cyclosporine A, cyclophosphamide, D-penicillamine, interferon, tumor necrosis factor-α antagonist) ii. Cytotoxic drugs (such as colchicine) iii. Pirfenidone iv. Tyrosine kinase inhibitors (such as nintedanib) v. Treatment of pulmonary hypertension (such as endothelin receptor antagonists, phosphodiesterase type-5 inhibitors, riociguat, prostacyclin or prostacyclin analogs) vi. N-acetylcystine vii. Other investigational drug viii. Any unapproved drugs for the treatment of IPF, such as interferon-γ, penicillamine, cyclosporine, and mycophenolate

  22. Patients who have received standardized corticosteroid treatment (oral corticosteroids ≤ 10 mg/day are acceptable) within 4 weeks before screening or during the screening period or who require this treatment during the study period.

  23. Patients who have used P-glycoprotein inhibitors or the substrates of transporters OAT1（Organic Anion Transporter 1）, OAT3（Organic Anion Transporter 3）, OCT2（organic cation transporter 2）, MATE2-K（multidrug and toxin extrusion 2-K）, and MATE1（multidrug and toxin extrusion 1）, with a time interval from the first treatment with the study drug less than five half-lives of the above drugs.

  24. Patients with a history of drinking, drug or chemical abuse, which the investigator judges may harm or affect the patient's complete participation in this study.

  25. Patients with known or suspected peptic ulcers, or patients with palsy, esophageal stenosis, or difficulty swallowing drugs.

  26. Patients who smoked within 3 months before screening or are unwilling to quit smoking during the study period.

  27. Patients whose 12-lead ECG results show QTcF（QT interval corrected using Fridericia's formula） interval > 450 msec in men and QTcF interval> 460 msec in women at screening; or patients with a family or personal history of QT interval prolongation syndrome.

  28. Pregnant or breast-feeding women.

  29. Women and men of childbearing age who are unwilling to use effective contraceptive methods during the study period or at least 3 months after the last administration of the investigational drug.

High-efficiency contraceptive methods for female patients include:

1. Complete abstinence
2. Female sterilization operation (bilateral oophorectomy with or without hysterectomy, total hysterectomy or tubal ligation) at least 6 weeks before receiving study treatment.
3. Male sterilization (at least 6 months before screening). For female patients in the study, the male partners who have undergone vasectomy should be their only partners.
4. Use of oral contraceptives (estrogen and progesterone), and female patients should have used the same contraceptives steadily for at least 3 months before receiving study treatment.
5. Injection or implantation of hormonal contraception or placement of intrauterine device (IUD) or intrauterine system (IUS), or other forms of hormonal contraception with similar efficacy (failure rate <1%), such as hormonal vaginal ring or transdermal hormonal contraception.

High-efficiency contraceptive methods for male patients include:

1. Vasectomy (a post-vasectomy record proves that there are no sperm in the ejaculation).
2. Having sex with a fertile female who uses the aforementioned high-efficiency contraceptive methods.