This is a Phase 2a, randomized, double-blind, multi-center, placebo-controlled, parallel-design, 2-arm study. This study will be conducted in approximately 20 centers globally, in subjects with IPF. Participation will last for about 18 weeks and include about 12 study clinic visits with the Study Doctor and/or study staff. This study will take place over approximately a year. The study will investigate a single dose level of GRI-0621 of 4.5mg compared with placebo, following once daily oral administration for 12 weeks. Approximately 36 subjects with IPF will be randomized in a 2:1 ratio for GRI-0621 4.5mg or Placebo. The study consists of a Screening Period, a Treatment Period and a Safety Follow-Up Period. The Screening Period will be conducted within 4 weeks prior to randomization, and is comprised of at least two separate in-clinic visits to assess eligibility.
Concurrently, a BAL Sub-Study will be conducted, for up to 12 eligible subjects (across various centers). The objective of the Sub-Study is to examine the role of NKT cells in fibrotic lung disease.

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.