This is an open-label extension study for participants who were previously enrolled in and completed an Avalyn Pharma Sponsored study with an inhaled antifibrotic, such as AP01. Eligible participants will have their final dose of drug at the end of study visit from the lead-in study and first AP-LTE-008 study visit on the same day. All participants will receive 100 mg inhaled pirfenidone inhalation solution (AP01) taken twice daily using the eFlow Nebulizer System for until such a time that the drug is approved, the participant withdraws from the study, or the study is terminated. New patients will be trained to use the nebuliser at the first treatment visit. All patients will use the eFlow nebuliser to administer AP01. Hands on training for use and cleaning of the eFlow nebuliser will be performed by site personnel with patients using the study specific instructions for use and quick reference guide provided. The first treatment for new patients will be overseen by clinic personnel. A paper dosing diary will be used to monitor adherence along with returns of any unused investigational product.