• Volunteer to participate and sign the ICF.

• Male or female patients' age ≥ 18 years when signing the ICF.

• Patients with known or unknown etiology (except IPF) and clear pulmonary fibrosis on chest CT have undergone conventional clinical treatment (assessed by the investigator, including follow-up observation) for ≥ 3 months. At least two of the following criteria occurring within 12 months before screening without alternative explanation (such as infection, heart failure, etc.):

• i) Worsening respiratory symptoms like cough, shortness of breath. ii) Physiological evidence of disease progression (either of the following):

‣ absolute FVC (% of predicted) decline ≥ 5%.

‣ absolute DLco\[Hb corrected\] (% of predicted) decline ≥ 10%. iii) Radiological evidence of disease progression (one or more of the following):

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∙ Increased extent or severity of traction bronchiectasis and bronchiolectasis.

‣ New ground-glass opacity with traction bronchiectasis.

‣ New fine reticulation.

‣ Increased extent or increased coarseness of reticular abnormality.

‣ New or increased honeycombing.

‣ Increased lobar volume loss.

• Fibrosing lung disease on HRCT, defined as reticular abnormality with traction bronchiectasis with or without honeycombing, with disease extent of \>10% as confirmed by central readers.

• For patients with underlying connective tissue disease (CTD) should be in the stable status which is defined by no initiation of new therapy, treatment dose adjustment or withdrawal of therapy within 12 weeks prior to randomization.

• FEV1/FVC ≥ 0.7 before using bronchodilators.

• %FVC ≥ 45% predicted.

• Carbon Monoxide Diffusion Capacity (DLCO) corrected for Haemoglobin (Hb) ≥ 30% and ≤ 80% predicted of normal.

• Fertile female or male subjects agreed and promised to take effective contraception measures from signing the ICF till 30 days after last administration.

⁃ Subjects are willing and able to comply with the protocol requirements and attend visits assessed by the investigator.