The Safety and Tolerability of Pirfenidone for BOS After HCT

Inclusion Criteria: 1. Age \> 18 years at randomization 2. Clinical symptoms (e.g., dyspnea or cough) consistent with BOS of ≥ 2 months duration 3. Presence of cGVHD in an organ other than lung 4. Subjects must have had recent pulmonary function test (PFTs) measured for at least 3 months prior to study enrollment that show: 1. A decrease in %FVC and/or %FEV1 ≥ 20% at Screening compared with pre-transplant baseline. 2. Bronchodilator response on PFT testing that results in an FEV1 \< 75% 5. Diagnosis of BOS by one of the following criteria: 1. Transbronchial or surgical lung biopsy demonstrating the obliterative bronchiolitis lesion 2. Volumetric CT scan with lung density analysis with ≥ 28% air trapping (1). 3. NIH-based PFT criteria for the diagnosis of BOS: FEV1/FVC \<0.7 and FEV1 \< 75% 4. Evidence of clinical improvement after treatment for BOS has been initiated. 6. No features supporting an alternative diagnosis by transbronchial biopsy, bronchoalveolar lavage (BAL), surgical lung biopsy, culture and non-culture based data, if performed 7. Adequate organ and marrow function including: liver function as defined by a total bilirubin below the upper limit of normal (ULN), excluding patients with Gilbert's syndrome; AST/SGOT or ALT/SGPT \< 3 x ULN; alkaline phosphatase \< 2.5 x ULN; renal function as defined by a CrCl \> 30 mL/min, calculated using the Cockcroft-Gault formula; cardiac electrophysiologic stability as defined by an electrocardiogram (ECG) with a QTc interval \< 500 msec at Screening; and bone marrow function as defined by a white blood cell count \> 3 K/µL, an absolute neutrophil count \> 15 K/µL and a platelet count \> 20 K/µL 8. Life expectancy \> 6 months 9. Participants must be able to understand and sign a written informed consent form and understand the importance of adherence to study treatment and protocol. In addition, participants must demonstrate a willingness to follow all study requirements, including the concomitant medication restrictions, throughout the study Exclusion Criteria: 1. Any condition that, in the opinion of the investigator, might be significantly exacerbated by the known side effects associated with the administration of pirfenidone e.g., presence of active GVHD of the gastrointestinal tract as manifested by rising liver function tests (LFTs) prior to initiation of study treatment 2. Uncontrolled infection 3. Major surgery within the past 2 months 4. The use of another investigational drug within the previous 30 days. 5. Inability to attend scheduled clinic visits 6. Inability to perform pulmonary function testing 7. Significant clinical change in health in the past 30 days 8. Body mass index (BMI) \< 17.5 9. Life expectancy \< 6 months due to any condition other than BOS that, in the opinion of the investigator, is likely to result in the death of the patient. 10. History of unstable or deteriorating cardiac or pulmonary disease (other than BOS) within the previous 6 months, including but not limited to the following: 1. Unstable angina pectoris or myocardial infarction 2. Congestive heart failure requiring hospitalization 3. Uncontrolled clinically significant arrhythmias 11. Pregnancy or lactation. 12. Family or personal history of long QT syndrome 13. Investigational therapy, defined as any drug that has not been approved for marketing for any indication in cGVHD will be restricted from the study 14. The following medications may significantly increase the level of Pirfenidone and should not be taken concurrently including: fluvoxamine, ciprofloxacin \> 500mg twice daily, systemically administered aminolevulinic acid, vemurafenib and enoxacin. Any other strong inhibitors of P450 isoenzymes CYP1A2, CYP2C9, 2C19, 2D6, and 2E1 should be avoided. Participants that cannot take alternative medications to those listed above will be excluded from this study. Laboratory Exclusions 1. Any of the following LFT criteria above specified limits: total bilirubin above the upper limit of normal (ULN), excluding patients with Gilbert's syndrome; aspartate or alanine aminotransferase (AST/SGOT or ALT/SGPT) \>3 × ULN; alkaline phosphatase \>2.5 × ULN 2. Creatinine clearance (CrCl) \<30 mL/min, calculated using the Cockcroft-Gault formula 3. Electrocardiogram (ECG) with a QTc interval \>500 msec at Screening Medication Exclusions 1\. Prior use of pirfenidone or known hypersensitivity to any of the components of study treatment.