Equillium (EQ) Status update summary

Mechanistic insights into AhR and miR-124 axis

• AhR is a ligand-activated transcription factor involved in detoxification, immune modulation, anti-inflammatory cytokine production, antioxidant protein expression, and barrier repair, with responses varying by ligand and cell type.

• AhR activation induces both genomic and non-genomic pathways, including immune regulation and barrier function, with regulatory microRNAs such as miR-124 being key downstream effectors.

• miR-124 is induced downstream of AhR activation in immune cells, but not in epithelial cells, and acts as a negative regulator of AhR; overexpression decreases AhR and promotes inflammation, while inhibition increases AhR and reduces inflammation.

• Dietary AhR ligands favor immune regulation and barrier repair, while xenobiotics drive detoxification pathways.

• AhR antagonism blocks induction of miR-124, CYP1A1, IL-10, and IL-22, highlighting pathway dependency and the centrality of AhR signaling in immune and epithelial homeostasis.

ABX464 and EQ504 as AhR modulators

• ABX464 is a moderately potent AhR modulator binding the PAS-B domain, while its glucuronidated form (ABX464-N-Glu) does not bind or modulate AhR.

• Pharmacophore and docking analyses show ABX464 shares structural features with other AhR modulators and docks into the PAS-B pocket via conserved π-π stacking.

• EQ504 and ABX464 are confirmed AhR modulators that induce miR-124 and anti-inflammatory cytokines, with EQ504 designed for high colon tissue and low systemic exposure.

• AhR antagonism with GNF-351 blocks ABX464-induced AhR activation, confirming direct, on-target activity.

Functional and translational findings

• ABX464 and EQ504 induce miR-124 and suppress pro-inflammatory cytokines (IL-6, IL-17, TNF-α, IL-23, IL-12, IL-1β) in PBMCs, CD4+ T cells, and M1 macrophages in an AhR-dependent manner.

• Both compounds reduce IL-17a+ cells in CD4+ T cells and inhibit IL-6, TNFα, IL-23, IL-12, and IL-1β in M1 macrophages.

• EQ504, but not ABX464, significantly induces anti-inflammatory IL-22 in PBMCs.

• In regulatory T cells and M2 macrophages, ABX464 and EQ504 induce CYP1A1, miR-124, IL-10, and IL-22 in an AhR-dependent manner; antagonism blocks these effects.

• Both compounds decrease AhR expression in regulatory T cells and enhance wound healing and barrier integrity in intestinal epithelial cells via AhR activation.