An S100A8/A9 Neutralizing Antibody Potently Ameliorates Contact Hypersensitivity and Atopic Dermatitis Symptoms

Contact hypersensitivity and atopic dermatitis are pervasive inflammatory skin diseases with similar symptoms, and their global prevalence is steadily increasing. Many compounds and biotics have been developed to target molecules critical to the etiology or pathogenesis of contact hypersensitivity and atopic dermatitis. However, these molecules are sometimes ineffective or lose their potency during the therapeutic course. Therefore, innovative medicines are still needed for the treatment of intractable cases. We focused on S100A8/A9, a heterodimer complex of S100A8 and S100A9 that is abundant in the extracellular milieu of inflammatory skin lesions. Although S100A8/A9 is primarily recognized as a diagnostic marker protein, we have previously shown that it also plays a crucial role in contact hypersensitivity and atopic dermatitis progression. This insight inspired us to develop its inhibitory antibody, leading to the ground-breaking Ab45. In this study, we demonstrated that Ab45 effectively prevented disease symptoms in various models and that its disease-ameliorating activity likely involved the downregulation of several disease-relevant molecules, including Il-23a, Il-36g, S100a8, and S100a9. We also created a humanized version of Ab45, HuAb45, which exhibited similar effectiveness. These antibodies show great promise for the treatment of contact hypersensitivity and atopic dermatitis and possibly for other inflammatory skin diseases.