Generalisability of pharmaceutical randomised controlled trial eligibility criteria for progressive pulmonary fibrosis

BACKGROUND: Progressive pulmonary fibrosis (PPF) is of substantial interest for novel pharmacotherapy discovery, but little is known about clinical trial eligibility criteria. We evaluated eligibility criteria of PPF randomised controlled trials, their representativeness in registry patients, and forced vital capacity changes and mortality according to trial eligibility. METHODS: A systematic search was used to identify completed and in-progress phase 2 and 3 PPF randomised controlled trials. Common clinical trial eligibility criteria used in ≥60% of previous PPF randomised controlled trials were identified. The most common criteria for PPF used in randomised controlled trials ("trial-PPF criteria") and the clinical practice guideline definition of PPF ("guideline-PPF criteria") were both applied to patients enrolled in a prospective multicentre Canadian registry. Common trial eligibility criteria were tested for their frequency and association with health outcomes in registry patients who met trial-PPF and guideline-PPF criteria. RESULTS: 10 different definitions of PPF were used in 16 randomised controlled trials. At the time of meeting PPF definitions, 50% of 864 patients with trial-PPF and 44% of 408 patients with guideline-PPF met the common trial eligibility criteria. For both definitions, trial-eligible patients had more rapid 1-year decline in forced vital capacity but better transplant-free survival than trial-ineligible patients. Patients with unclassifiable interstitial lung disease had a higher proportion of trial exclusion compared to those with connective tissue disease-associated interstitial lung disease and fibrotic hypersensitivity pneumonitis. Annual forced vital capacity decline (trial-PPF: -67 to -21 mL; guideline-PPF: -116 to -41 mL) and 1-year transplant-free survival (trial-PPF: 90.5-97.5%; guideline-PPF: 87-96.2%) varied in trial-eligible patients across interstitial lung disease subtypes. CONCLUSIONS: Existing randomised controlled trials use a variety of definitions for PPF with eligibility criteria that have limited representativeness. Forced vital capacity decline and transplant-free survival vary according to trial eligibility and interstitial lung disease subtypes.