D1.240 - ATH-409, a selective and covalent ITK inhibitor, protects against atopic dermatitis in preclinical models

Atopic dermatitis (AD) is the most common chronic inflammatory skin disease caused by the dysfunction of the skin barrier and Th2-dominant immune dysregulation. Targeting Th2 cytokines and downstream signals has been demonstrated solid clinical efficacy. However, there still remain unmet medical needs for exploring novel therapy strategies, due to inefficient efficacy and adverse effects of current typical and systemic drugs. ITK, a member of Tec family, plays a crucial role in TCR signals to promote T cell survival and differentiation. ITK knockout mice displayed a defect in Th2 differentiation, but retained the ability of Th1 differentiation. Double knockout of ITK and RLK furtherly disrupts T cell development and differentiation to multiple subtypes, resulting in a loss of normal T cell function. Thus, selective inhibition of ITK emerges as an attractive treatment for AD.

ADP-GLO based biochemical assays were performed to determine the enzymatic effect and selectivity. The target engagement was evaluated by anti-CD3-induced pPLCγ in Jurkat cells and IL-2 production in PBMC. In vivo efficacy was assessed by oxazolone or DNFB-induced model in female Balb/c mice. Ears were collected post last dose 2h for the measurement of thickness, weight, cytokines (ELISA or MSD) and histopathology. Spleens were collected for ITK occupancy test.

ATH-409 is a highly selective, covalent ITK inhibitor with an IC₅₀ of 3.7 nM and more than 300-fold selectivity against RLK and at least 100-fold selectivity against the ten cysteine-containing kinases. In the 430 kinases panel assay, ATH-409 exhibits inhibitory activity against 5 kinases, with selectivity of at least 60-fold. ATH-409 potently suppresses pPLCγ1 and IL2 release at nanomolar levels. In the DNFB-induced acute model, ATH-409 significantly improved ear swelling, accompanied by a decrease in IL-1β and TNFα in ears and full ITK occupancies in spleens. In an oxazolone-induced chronic model, ATH-409 dose-dependently inhibited the ear swelling, reduced cytokine expressions, such as IgE, IL-4, IL-13 and IL-6, and significantly alleviated inflammatory cell infiltration into ears. 

ATH-409 is a novel and highly selective ITK inhibitor and demonstrated robust efficacy in preclinical atopic dermatitis models. These results indicate a potential application of ATH-409 to atopic dermatitis therapy.