Discovery of CaSR Peptide Agonists via Multistage Screening: In Silico Design, In Vitro Validation, and In Vivo Efficacy

Human calcium-sensing receptor (CaSR) is a class C G protein–coupled receptor (GPCR) that directly regulates parathyroid hormone release and maintains calcium homeostasis. The discovery of potent CaSR agonists with computer-aided drug design (CADD) has been appealing. Herein, we report the discovery of a series of new CaSR agonists by enhancing the molecular binding affinity through the replacement of key residues via the iCVETide platform. Ac-_D-Cys(_L-Cys)-_D-Arg-_D-(3-Gu)-Phe-_D-Abu-_D-Arg-_D-Ala-_D-Arg-NH₂ (compound 6g) with an outstanding activity and a satisfactory ADME profile is discovered, and the interaction mode between 6g and CaSR is elucidated through molecular docking and molecular dynamics simulations, showing hydrogen bonds, salt bridges, and π–π stacking. In addition, 6g is capable of activating human CaSR as a calcimimetic positive allosteric modulator. Our results provide a viable alternative to approved calcimimetics and a novel protocol for the discovery of CaSR agonists.