AntiCoagulant Effectiveness in Idiopathic Pulmonary Fibrosis

Study design: ACE-IPF was a double-blind, randomized, placebo-controlled trial of an oral warfarin dose adjusted to an international normalized ratio (INR) response of 2.0 to 3.0, compared with a sham dose-adjusted placebo. The trial was originally designed as an event-driven study with a treatment period of up to 144 weeks. Given the slow rate of recruitment and higher than anticipated event rates seen in another Idiopathic Pulmonary Fibrosis Clinical Research Network (IPFnet) trial, the protocol was modified to have a maximum treatment period of 48 weeks after eleven patients were enrolled in the study. Participants were to be seen at screening, baseline, and at 16, 32, and 48 weeks after enrollment. Outcome measures: The primary outcome was a composite endpoint based on the time to all-cause mortality; non-elective, non-bleeding hospitalization; or a decrease in the absolute FVC ≥10% from baseline value. Secondary outcome measures included rates of mortality, hospitalization, respiratory-related hospitalization, acute exacerbation, bleeding, cardiovascular events, and changes over time in FVC, six-minute walk test distance, diffusing capacity of lung for carbon monoxide (DLCO), plasma fibrin D-dimer levels, and quality of life (QOL) assessments. Data Analysis Continuous variables at baseline were expressed as means (standard deviations) and medians (25th and 75th percentiles). Categorical variables at baseline were expressed as counts and percentages. Unadjusted estimates of event rates for time-to-event variables were computed using the Kaplan-Meier estimator with comparisons based on the log-rank test statistic. The primary hypothesis was tested using a Cox proportional hazards regression model, comparing the treatment effect on the primary composite endpoint. Pre-specified covariates in this model included an indicator variable for the treatment group and the DLCO measurement from the baseline assessment. Randomization: Subjects were randomly assigned to study arms in a 1:1 ratio, using a permuted-block design with varying block sizes, to receive either warfarin or matched placebo. Subjects were stratified by clinical center and a DLCO threshold of 35% of predicted. Randomization lists were generated by the study data coordinating center (DCC) and provided to a phone- and web-enabled registration system (Almac Clinical Services, Inc.) that allowed sites to enroll subjects and receive study kits while keeping the study team and subjects blinded to treatment assignment. INR testing and monitoring: Study subjects were provided two strengths of warfarin tablets (1 mg and 2.5 mg) or matching placebos. Subjects measured their INR with encrypted meters (INRatio®, Alere, San Diego, CA) at least weekly. Home monitoring was validated by plasma INR measurement at the week 1 and 16 visits. Individual INR meters and test strips were replaced and subjects were reinstructed if meter INR readings varied by more than 30% from the laboratory INR. Efficacy of home INR measures were determined by time-in-target INR range of all patients, calculated on the basis of linear interpolation, 12 after excluding readings taken at baseline, during initial warfarin titration (until INR ≥ 2.0), study drug interruption, or following the discontinuation of study drug.