An RCT of Mycophenolate Mofetil (MMF) in Fibrotic Hypersensitivity Pneumonitis

Inclusion Criteria: i. A diagnosis of fibrotic hypersensitivity pneumonitis according to the criteria proposed in the American Thoracic Society Guideline 2020 ii. Screening FVC at least 40% of the predicted value iii. Able to provide a written, informed consent for participation in the trial Exclusion Criteria: i. Baseline FVC \<40% predicted ii. Leucopenia (white blood cell count \<4·0 × 10\^9 per L), significant thrombocytopenia (platelet count \<100 × 10\^9 per L), or clinically significant anemia (hemoglobin \<10 g/dL) iii. Baseline liver transaminases (alanine aminotransferase and aspartate aminotransferase) or bilirubin more than 1·5 times the upper normal limit (except in the case of Gilbert's syndrome) iv. Serum creatinine higher than 2.0 mg/dL v. Uncontrolled congestive heart failure vi. Receipt of prednisolone (more than or equal to 10 mg/day, or equivalent), in the 4 weeks before randomization vii. Prior use of prednisolone (more than or equal to 10 mg/day, or equivalent), MMF, azathioprine, cyclophosphamide, cyclosporine or any other non-glucocorticoid immunosuppressant drug, or antifibrotic agents for more than 12 weeks in the previous year viii. Active infection (lung or elsewhere) whose management would be compromised by MMF or prednisolone ix. Other serious concomitant medical illness (eg, cancer), chronic debilitating illness (other than chronic HP), or drug abuse x. Pregnancy (documented by urine pregnancy test) or breastfeeding xi. Unwilling to participate in the study