This study will see if the experimental medicine MTX-463 can slow or stop idiopathic pulmonary fibrosis (IPF) from worsening in people at least 40 years of age or older. Participants will receive either MTX-463 or a placebo (which contains no active drug) through an intravenous infusion once every 4 weeks, for a total of 6 infusions. Overall, participants will attend a total of 9 visits over the course of approximately 32 weeks, or roughly 8 months.

The purpose of this study is to learn more about interstitial lung disease through collection of information and blood samples to be used in future research projects. Basic information and a blood sample will be collected in conjunction with clinical care for this study, approximately every 3 months.