Patient description: A 57-year-old man was admitted to the clinic because of weight loss and persistent dry cough 4 months ago. Chest computed topography showed bilateral multiple infiltrates in the upper lobes and thickened bronchial walls. There is a documented positive serum MPO-ANCA in his medical record. Transbronchial biopsy revealed necrotic granulomas with multinucleated giant cells and the Wegener's granulomatosis was diagnosed for him. He is treating with corticosteroid and cyclophosphamides since 4 months ago. His Birmingham Vasculitis Activity Score (BVAS) is above 4 since the beginning of his disease. His last physical exam and lab study was performed yesterday and showed the results bellow: A wellbeing, well-nourished man, non-icteric, cooperative and alert Weight: 73 kg Height: 177 BP: 120/80 HR: 90/min RR: 22/min Hgb: 13 g/dl WBC: 8000 /mm3 (Neutrophil: 2700/mm3) Plt: 300000 /ml AST: 40 U/L ALT: 56 U/L Alk P: 147 U/L Bill total: 1.2 mg/dl ESR: 120 mm/hr MPO-ANCA: 153 EU

Clinical trial eligibility criteria: eligible ages (years): 18.0-999.0,  Pulmonary Fibrosis Age > 18 years Presence of anti-MPO antibody (ELISA) at or during pulmonary fibrosis follow-up and/or diagnosis of anti-MPO associated vasculitis according to the 2012 Revised International Chapel Hill Consensus Conference definitions Definite or possible Usual Interstitial Pneumonia or Non Specific Interstitial Pneumonia based on high-resolution computed tomography Presence of pulmonary fibrosis, defined as a range of 50 to 90% of the %FVC and a range of 30 to 90% of the %DLCO Pulmonary fibrosis refractory (according to the investigator's judgment) to a conventional regimen used for anti-MPO associated vasculitis when a treatment against vasculitis has been used Have the ability to understand the requirements of the study, provide written informed consent (including consent for the use and disclosure of research-related health information) and comply with the study protocol procedures (including required study visits) Have affiliation with a mode of social security (profit our being entitled)  Other type of systemic vasculitis Active vasculitis defined by Birmingham Vasculitis Activity Score >3 (BVAS)  Contraindication to Pirfenidone Unable to perform pulmonary function test (PFT) Pregnancy or lactation. Women of childbearing capacity are required to have a negative serum pregnancy test before treatment and must agree to maintain highly effective contraception by practicing abstinence or by using an effective method of birth control from the date of consent through the end of the study : implants of levonorgestrel; injectable progesterone; any intrauterine device (IUD) with a documented failure rate of less than 1% per year; oral contraceptives (either combined or progesterone only); double barrier method (condom, cervical cap or diaphragm with spermicidal agent); transdermal contraceptive patch; male partner who is sterile prior to the female subject's entry into the study and is the sole sexual partner for the female subject Any of the following liver function test above specified limits: total bilirubin above 1,5 times the upper limit of normal (ULN), excluding patients with Gilbert's syndrome; aspartate (AST)/Glutamate Oxaloacétique Transaminase (SGOT) or alanine aminotransferase (ALT)/Glutamate Pyruvate Transaminase (SGPT), (AST/SGOT or ALT/SGPT) >3 × ULN; alkaline phosphatase >2.5 × ULN Creatinine clearance (CrCl<30) mL/min, calculated using the Cockcroft-Gault formula at screening Current treatment with Nintedanib or past treatment with Nintedanib in the last 12 months Current treatment with Fluvoxamine or past treatment with Fluvoxamine in the last 28 days before screening Prior use of Pirfenidone or known hypersensitivity to any of the components of study treatment