Abstract Body: Background: The clinical data suggest an association of autoantibodies (AAb) targeting angiotensin II type1 receptor (AT1R) and outcomes in heart failure (HF) and preeclampsia. Notably, patient’s risk increases 2 to 4-fold for heart diseases and hypertension. Although AT1R blockers (ARBs) have emerged as a key component in the therapeutic arsenal against CVD, we believe that rather than completely blocking AT1R signaling, maintaining a balanced signaling is crucial for cardiovascular homeostasis. Therefore, we posit that reducing AT1R overactivation and blocking AAb-mediated activation could benefit cardiac health and attenuate the progression of CVD. In our previous study (PMID:36440576), we identified small molecules capable of inhibiting AAb-induced AT1R signaling. Leveraging these observations, we have developed a novel AT1R allosteric ligand that inhibits autoantibody binding to AT1R while still retaining normal AT1R signaling.
Methods: Using computational and medicinal chemistry approaches, we designed a series of novel AT1R ligands and obtained compounds with >98% purity through chemical synthesis. Monoclonal antibodies mimicking AT1R-AAb have been generated. Serum samples from dilated cardiomyopathy (DCM) and preeclampsia (PE) patient cohorts were collected and presence of AT1R-AAb was determined using ELISA and epitope-peptide competition studies. Pharmacological characterization of compounds was performed using calcium mobilization, ^125I-AngII binding, ex vivo vasoconstriction, and ELISA assays.
Results: We identified an AT1R allosteric compound that reduced AngII-mediated calcium signaling with a 5-fold shift in EC₅₀. The IC₅₀ was determined to be 18 µM. It reduces the AngII-mediated vasoconstriction while blocking both monoclonal and patient-derived autoantibody binding with an IC₅₀ of 5 µM.
Conclusion: We have identified a novel AT1R allosteric ligand with negative allosteric modulator (NAM) properties, which has the potential to block autoantibodies and could serve as a new generation of ARBs. Uniquely, it retains beneficial AT1R signaling without competing with AngII, and its allosteric ligand property can be tailored to achieve optimal AT1R signaling.