Equillium is a clinical-stage biotechnology company developing treatments for severe autoimmune and inflammatory diseases, focused on the gut and lungs. The company has two lead programs. EQ504 is an aryl hydrocarbon receptor (AhR) modulator — AhR being a protein that regulates inflammation and tissue barrier function — designed for local rather than systemic delivery, which Equillium argues may reduce side effects relative to existing immunosuppressants. EQ504 is being developed primarily for ulcerative colitis, with a Phase 1 healthy volunteer study planned for mid-2026. EQ302 is an oral inhibitor that selectively blocks two inflammation-driving proteins, IL-15 and IL-21, and is being developed for celiac disease, a condition with no approved drug treatment. EQ302 remains in preclinical development. Both compounds were acquired rather than internally discovered — EQ504 via the 2024 purchase of Ariagen, and EQ302 via the 2022 acquisition of Bioniz Therapeutics. Equillium has no approved products, no product revenue, no manufacturing operations, and only 14 employees. The company relies entirely on third-party contract manufacturers and funds operations through equity issuances. Equillium raised roughly $30M in 2025 and another ~$35M in early 2026 through private placements, which the company believes will fund operations into 2029.