Biologics targeting OX40 and OX40L for treatment of atopic dermatitis have distinct inhibitory binding mechanisms

Summary: Abstract Body: Atopic dermatitis (AD) is a chronic inflammatory skin disorder affecting ~200 million individuals worldwide, with children and adolescents commonly affected. Although AD pathogenesis is multi-faceted, the heterotrimeric immune checkpoint molecules OX40 and OX40L play a critical role. Recent clinical trials demonstrated the OX40-targeting antibodies rocatinlimab (KHK4083/AMG-451) and telazorlimab (GBR-830/ISB-830), as well as the OX40L-targeting antibody amlitelimab (KY1005), significantly improve AD signs and symptoms. However, the structural mechanisms of how these antibodies disrupt downstream OX40-OX40L signaling, such as antibody epitope properties, remain unknown. Thus, we computationally modeled the antibody-protein complexes and biochemically characterized their binding interfaces. We performed molecular dynamics simulations to evaluate antibody-target complex stability. The cognate OX40-OX40L heterotrimeric complex has two distinct OX40-OX40L interaction interfaces, as well as a symmetric OX40L-OX40L interface. Rocatinlimab is predicted to have 37% overlap with the two OX40L binding sites, binding the highly conserved OX40 residue T85. Contrarily, telazorlimab showed minimal overlap with the OX40L binding sites but disrupted the critical salt bridge between R65 of OX40 and E82 of OX40L. Amlitelimab demonstrated 75% overlap with one of the OX40 binding sites, where it binds the highly conserved OX40L residue N166, as well as 16% overlap with the physiologic OX40L trimer interface. Our results provide initial prediction and analysis of the epitopes of OX40 and OX40L targeted biologics emerging for AD treatment. Rocatinlimab and amlitelimab appear to directly inhibit OX40-OX40L interactions via steric occlusion, with amlitelimab also possibly inhibiting OX40L trimer formation, whereas telazorlimab more specifically disrupts a critical intermolecular interaction. Kelsey Nolden¹, Yuanjun Shi², Christopher G. Bunick³ 1. Biochemistry, Medical College of Wisconsin, Milwaukee, WI, United States. 2. Chemistry, Yale University, New Haven, CT, United States. 3. Dermatology, Yale University School of Medicine, New Haven, CT, United States. Translational Studies: Cell and Molecular Biology