This is a randomized, double-blind, placebo-controlled clinical study to evaluate the safety and efficacy of 2 doses of AP01 versus placebo on top of standard of care in subjects with Progressive Pulmonary Fibrosis (PPF) over 52 weeks. Subjects will participate in the study for up to 58 weeks, inclusive of a Screening Period of up to 4 weeks, a 52-week Treatment Period, and a 2-week Follow-up Period that includes a Follow-up telephone call (TC) 2 weeks post final dose. Up to 300 eligible subjects will be randomized in a 2:1:2 ratio to 1 of 3 treatment arms: AP01 100 mg twice daily (BID), AP01 50 mg BID, or placebo BID (8 mL; two 4 mL blow-fill-seal [BFS] ampoules BID).