La Jolla, California-based Equillium (Nasdaq: EQ) has received Australian regulatory and ethics clearance to begin a first-in-human Phase I trial of EQ504, an oral aryl hydrocarbon receptor (AhR) modulator being developed for ulcerative colitis. Dosing in healthy participants is expected to start by early November 2026.
The randomized, double-blind, placebo-controlled study will assess safety, tolerability, pharmacokinetics and pharmacodynamics across single and multiple ascending doses, alongside a food-effect cohort. Gastrointestinal mucosal biopsies in the multiple-dose portion will assess tissue-specific biomarkers to help establish proof of mechanism.
EQ504 is intended to address both inflammation and damage to the intestinal lining. AhR regulates immune responses and barrier tissue function, and Equillium’s preclinical studies suggest the compound can promote anti-inflammatory signalling while supporting epithelial repair. The Phase I study’s gastrointestinal biopsies will help determine whether the drug engages this pathway in human tissue.
The programme joins a growing effort to translate AhR biology into bowel disease treatments. Allianthera and Dr. Falk Pharma are developing ATB102, a gut-enriched AhR agonist that was in Phase I when their partnership was announced in July 2025. The target is already established in dermatology through Dermavant Sciences' Vtama (tapinarof), although that topical drug’s approval does not establish efficacy for oral AhR modulation in ulcerative colitis.