Baseline IL-22 expression in patients with atopic dermatitis stratifies tissue responses to fezakinumab

Background: IL-22 is potentially a pathogenic cytokine in patients with atopic dermatitis (AD), but the molecular effects of IL-22 antagonism have not been defined in human subjects. Objective: We sought to evaluate the cellular and molecular effects of IL-22 blockade in tissues from patients with moderate-to-severe AD. Methods: We assessed lesional and nonlesional skin from 59 patients with moderate-to-severe AD treated with anti–IL-22 (fezakinumab) versus placebo (2:1) using transcriptomic and immunohistochemistry analyses. Results: Greater reversal of the AD genomic profile was seen with fezakinumab versus placebo, namely 25.3% versus 10.5% at 4 weeks (P = 1.7 × 10⁻⁵) and 65.5% versus 13.9% at 12 weeks (P = 9.5 × 10⁻¹⁹), respectively. Because IL-22 blockade showed clinical efficacy only in patients with severe AD, we used baseline median IL-22 mRNA expression to stratify for high (n = 30) and low (n = 29) IL-22 expression groups. Much stronger mean transcriptomic improvements were seen with fezakinumab in the IL-22–high drug-treated group (82.8% and 139.4% at 4 and 12 weeks, respectively) than in the respective IL-22–high placebo-treated group (39.6% and 56.3% at 4 and 12 weeks) or the IL-22–low groups. Significant downregulations of multiple immune pathways, including T_H1/CXCL9, T_H2/CCL18/CCL22, T_H17/CCL20/DEFB4A, and T_H22/IL22/S100A's, were restricted to the IL-22–high drug group (P <.05). Consistently, tissue predictors of clinical response were mostly genes involved in T-cell and dendritic cell activation and differentiation. Conclusions: This is the first report showing a profound effect of IL-22 blockade on multiple inflammatory pathways in AD. These data, supported by robust effects in patients with high IL-22 baseline expression, suggest a central role for IL-22 in AD, indicating the need for a precision medicine approach for improving therapeutic outcomes in patients with AD.