Open-label Study to Assess the Effectiveness of Pirfenidone in Participants With Idiopathic Pulmonary Fibrosis (IPF).

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