Discovery of Selective Small-Molecule CD80 Inhibitors

Protein-protein interactions are widely found in biological systems controlling diverse cellular events. Because these interactions are implicated in many diseases such as autoimmunity and cancer, regulation of protein-protein interactions provides ideal targets for drug intervention. The CD80-CD28 costimulatory pathway plays a critical role in regulation of the immune response and thus constitutes an attractive target for therapeutic manipulation of autoimmune diseases. The objective of this study is to identify small compounds disrupting these pivotal protein-protein interactions. Compounds that specifically blocked binding of CD80 to CD28 were identified using a strategy involving a cell-based scintillation proximity assay as the initial step. Secondary screening (e.g., by analyzing the direct binding of these compounds to the target immobilized on a biosensor surface) revealed that these compounds are highly selective CD80 binders. Screening of structurally related derivatives led to the identificatio...