 This is a dose escalationdose finding, double-blind, placebo-controlled, parallel study of GSK2126458 in subjects with IPF. The study is designed to explore a number of doses of GSK2126458 for engagement of pharmacology after short term dosing. It is anticipated that approximately 24 subjects will be enrolled in this study. Actual number of cohorts in this study could vary up to a maximum of 6 cohorts n4cohort; 3 on active and 1 on placebo. 