Entheseal tissue signature in response to IL-17A inhibition in psoriatic arthritis: results from the EBIO entheseal biopsy study.

OBJECTIVES

Enthesitis, a hallmark of psoriatic arthritis (PsA), reflects the interplay between mechanical stress and immune dysregulation at tendon-bone interfaces. This study investigates the cellular and molecular responses in entheseal tissues following interleukin (IL)-17A inhibition in patients with active PsA.

METHODS

In this prospective, interventional phase 4 trial, we enrolled 10 patients with enthesitis of the lateral epicondyle, performed entheseal biopsies, and analysed tissues by imaging mass cytometry (IMC) and spatial transcriptomics before and after treatment.

RESULTS

Following 24 weeks of IL-17A inhibition, 9/10 patients of the cohort clinically responded to treatment as assessed by Disease Activity in Psoriatic Arthritis (DAPSA), Spondyloarthritis research consortium of canada (SPARCC) score, and power Doppler sonography. IMC analysis showed significant reductions of enthesitis-related immune cell populations, in particular IL-17-producing CD4, CD8, CD4neg/CD8neg T cells, granulocytes, and innate lymphoid cells type 3. Spatial transcriptomics revealed that CD200+DKK3+ fibroblasts and innate lymphoid cells type 2 expanded and formed an anti-inflammatory niche upon treatment. Notably, IL-17A inhibition led to decreased osteoblast differentiation markers, suggesting a potential mechanism to inhibit pathological bone formation.

CONCLUSIONS

These findings underline the pivotal role of IL-17A in enthesitis, showing that IL-17A inhibition profoundly modulates the tissue microenvironment of entheses in PsA.