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.