La Jolla, California-based Equillium (Nasdaq: EQ) has received Australian clearance for a first-in-human trial of EQ504, an oral aryl hydrocarbon receptor (AhR) modulator being developed for ulcerative colitis. Dosing in healthy volunteers is expected by early November 2026, with the study designed to assess safety and whether the drug produces its intended biological effects in the gut.
AhR regulates immune responses and helps maintain the intestinal barrier, making it a potential target for addressing both inflammation and tissue damage in ulcerative colitis. EQ504 uses a colon-targeted, delayed-release formulation intended to deliver the drug locally. Equillium describes its mechanism as non-immunosuppressive, although its clinical effects remain unproven.
The randomized, double-blind, placebo-controlled Phase I study (NCT07869225) will assess single and multiple ascending doses, alongside a separate evaluation of food effects. Gastrointestinal mucosal biopsies will measure tissue biomarkers, including CYP1A1 expression, to assess local AhR activity alongside blood measurements of drug exposure.
Those tissue measurements could provide an early indication of whether EQ504 engages the intended pathway at tolerated doses. The healthy-volunteer study will not establish whether that activity translates into symptom improvement or mucosal healing in ulcerative colitis.