Novel Allosteric Ligands Of The Angiotensin Receptor At1r As Autoantibody Blockers

While orthosteric ligands of the angiotensin II (AngII) type 1 receptor (AT1R) are available for clinical and research applications, allosteric ligands are not known for this important G protein-coupled receptor (GPCR). Allosteric ligands are useful tools to modulate receptor phar-macology and subtype selectivity. Here, we report AT1R allosteric ligands for a potential application to block autoimmune antibodies. The epitope of autoantibodies for AT1R is outside the orthosteric pocket in the extracellular loop 2. A molecular dynamics simulation study of AT1R structure reveals the presence of a druggable allosteric pocket encompassing the autoantibody epitope. Small molecule bind-ers were then identified for this pocket using structure-based high-throughput virtual screening. The top 18 hits obtained inhibited the binding of antibody to AT1R and modulated agonist-induced calcium response of AT1R. Two compounds out of 18 studied in detail exerted a negative allosteric modulator effect on the functions of the natural agonist AngII. They blocked antibody-enhanced calcium response and reactive oxygen species production in vascular smooth muscle cells as well as AngII-induced constriction of blood vessels, demonstrating their efficacy in vivo. Our study thus demonstrates the feasibility of discovering inhibitors of the disease-causing autoantibodies for GPCRs. Specifically, for AT1R, we anticipate development of more potent allosteric drug candidates for intervention in autoimmune mal-adies such as preeclampsia, bilateral adrenal hyperplasia, and the re-jection of organ transplants.