A Study of Pirfenidone in Patients With Unclassifiable Progressive Fibrosing Interstitial Lung Disease

The purpose of this study is to evaluate the efficacy and safety of pirfenidone in participants with fibrosing interstitial lung disease (ILD) who cannot be classified with moderate or high confidence into any other category of fibrosing ILD by multidisciplinary team (MDT) review ("unclassifiable" ILD).

Study participants will be randomised to receive 801 mg pirfenidone or placebo three times daily for 24 weeks. The efficacy of pirfenidone versus placebo will be assessed by daily measurement of forced vital capacity using a handheld spirometer over the treatment period. Additionally, the study will assess the efficacy and safety of pirfenidone with and without concomitant mycophenolate mofetil treatment and in study participants with or without interstitial pneumonia with autoimmune features (IPAF). All study participants who attend the follow-up visit at Week 28 will be offered the opportunity to receive open-label pirfenidone within the trial protocol. In order to maintain blinding of the controlled period of the study, all study participants will discontinue treatment by Week 24 and return for a follow-up visit 4 weeks later. Study participants eligible to participate in the single-arm 12-month extension will be initiated on open-label pirfenidone during this visit (re-starting the dose titration from one capsule three times daily \[TID\]). During the long-term extension period, study participants will be monitored for safety, initially at monthly visits during the first 6 months and thereafter approximately every 3 months. A final follow-up visit will take place 4 weeks after the last dose of pirfenidone is taken.

Eligibility Criteria:
Inclusion Criteria:

* Age \>= 18-85 years
* Confirmed fibrosing ILD which, following multidisciplinary team review, cannot be classified with either high or moderate confidence as a specific idiopathic interstitial pneumonia or other defined ILD
* Progressive disease as considered by the investigator as participants deterioration within the last 6 months, which is defined as a rate of decline in forced vital capacity (FVC) \>5% or a significant symptomatic worsening not due to cardiac, pulmonary vascular or other causes
* Extent of fibrosis \>10% on high-resolution computed tomography
* Forced vital capacity \>= 45% of predicted value
* Diffusing capacity of the lung for carbon monoxide (DLco) \>= 30% of predicted value
* Forced expiratory volume in 1 second/FVC ratio \>= 0.7
* Able to do 6-minute walk distance (6MWD) \>= 150 meters
* For women of childbearing potential: agreement to remain abstinent or use a non-hormonal or hormonal contraceptive method with a failure rate of \< 1% per year during the treatment period and for at least 90 days after the last dose of pirfenidone
* For men, agreement to remain abstinent or use contraceptive measures, and agreement to refrain from donating sperm

Exclusion Criteria:

* Diagnosis with moderate or high confidence of nonspecific interstitial pneumonia and any ILD with an identifiable cause such as connective tissue disease-ILD, chronic hypersensitivity pneumonitis, or others
* Diagnosis of idiopathic pulmonary fibrosis independent of the confidence level
* History of unstable angina or myocardial infarction during the previous 6 months
* Treatment with high dose systemic corticosteroids, or any immunosuppressant other than mycophenolate mofetil/acid (MMF), at any time within the 4 weeks of the screening period. Participants being treated with MMF should be on a stable dose that is expected to remain stable throughout the trial and was started at least 3 months prior to screening
* Participants previously treated with pirfenidone or nintedanib
* Participants treated with N-acetyl-cysteine for fibrotic lung disease, at any time within the 4 weeks of the screening period
* Drug treatment for any type of pulmonary hypertension
* Participation in a trial of an investigational medicinal product within the last 4 weeks
* Significant other organ co-morbidity including hepatic or renal impairment
* Predicted life expectancy \< 12 months or on an active transplant waiting list
* Use of any tobacco product in the 12 weeks prior to the start of screening, or any unwillingness to abstain from their use through to the Follow-up Visit
* Illicit drug or alcohol abuse within 12 months prior to screening
* Planned major surgery during the trial
* Hypersensitivity to the active substance or to any of the excipients of pirfenidone
* History of angioedema
* Concomitant use of fluvoxamine
* Clinical evidence of any active infection
* Any history of hepatic impairment, elevation of transaminase enzymes, or liver function test results as: Total bilirubin above the upper limit of normal (ULN), Aspartate aminotransferase or alanine aminotransferase \>1.5 × ULN, and Alkaline phosphatase \>2.0 × ULN
* Creatinine clearance \< 30 milliliter (mL) per minute, calculated using the Cockcroft-Gault formula
* Any serious medical condition, clinically significant abnormality on an Electrocardiogram (ECG) at screening, or laboratory test results
* An ECG with a heart rate corrected QT interval using Fridericia's formula as \>= 500 milliseconds at screening, or a family or personal history of long QT syndrome