This study is a national, multicenter, interventional, non-randomized, non-controlled, open-label study to assess the effectiveness of pirfenidone in participants with IPF in Russian clinical practice.

Inclusion Criteria:

• Clinical symptoms consistent with IPF of ≥ 6months duration
• Participants could have both "confident" or "consistent" with UIP diagnosis of IPF based on clinical, radiologic and pathologic data according to 2011 American Thoracic Society/European Respiratory Society (ATS/ERS) guidelines at the Screening. HRCT scan performed within 24 months before the start of the Screening may be used, if it meets all image acquisition guideline
• No features supporting an alternative diagnosis on transbronchial biopsy, bronchoalveolar lavage (BAL), or surgical lung biopsy, if performed. Results of the surgical lung biopsy performed within the last 4 years must be confirmed by central review
• Participants with %FVC ≥ 40 % at the Screening
• Participants with %Carbon monoxide diffusing capacity (DLCO) ≥ 30 % at the Screening
• Ability to walk ≥ 100 m during the 6-minute walk test at the Screening
• Eligible participants must discontinue all prohibited medications at least 28 days before the Screening
• Female participants of childbearing potential must have negative urine pregnancy test at the Screening and before first dosing on Day 1

Exclusion Criteria:

• Significant clinical worsening of IPF between Screening and Day 1, in the opinion of the investigator
• Relevant airways obstruction (i.e. pre-bronchodilator forced expiratory volume (FEV)1/FVC < 0.7)
• Cigarette smoking within 28 days before the start of treatment or unwilling to avoid tobacco products throughout the study
• History of clinically significant environmental exposure known to cause pulmonary fibrosis (PF), including but not limited to drugs (such as amiodarone), asbestos, beryllium, radiation, and domestic birds
• Known explanation for interstitial lung disease, including but not limited to radiation, drug toxicity, sarcoidosis, hypersensitivity pneumonitis, bronchiolitis obliterans organizing pneumonia, human immunodeficiency virus (HIV), viral hepatitis, and cancer
• Clinical diagnosis of any connective tissue disease, including but not limited to scleroderma, polymyositis/ dermatomyositis, systemic lupus erythematosus, and rheumatoid arthritis
• During baseline analysis of HRCT, significant coexistent emphysema (emphysema extent greater than extent of fibrosis) confirmed by central review
• Planned lung transplantation during the study
• Clinical evidence of active infection, including but not limited to bronchitis, pneumonia, sinusitis, urinary tract infection, or cellulitis
• Unable to perform 6MWT or to undergo pulmonary function test
• Any history of malignancy likely to result in significant disability or likely to require significant medical or surgical intervention within the next 1 years. This does not include minor surgical procedures for localized cancer (e.g., basal cell carcinoma)
• History of severe hepatic impairment or end-stage liver disease
• History of end-stage renal disease requiring dialysis
• History of unstable or deteriorating cardiac or pulmonary disease (other than IPF) within the previous 6 months
• Pregnancy or lactation, or intention to become pregnant during the study. Women of childbearing capacity are required to have a negative urine pregnancy test before treatment and must agree to maintain highly effective contraception
• Liver function test outside specified limits at the Screening: total bilirubin above the upper limit of normal (ULN); aspartate or alanine aminotransferase (AST or ALT) > 3 × ULN; alkaline phosphatase > 2.5 × ULN
• Creatinine clearance < 30 mL/min, calculated using the Cockcroft-Gault formula
• Electrocardiogram (ECG) with a QT interval corrected according to Fridericia's formula (QTcF) > 500 msec at the Screening

CT images of lungs, forced vital capacity (FVC) measurements, post-hoc analysis