Receptor Antagonist
A molecule that binds to a receptor without activating it, blocking the natural ligand from binding and preventing the receptor's biological response. Peptide antagonists such as GnRH antagonists and the bradykinin antagonist icatibant are used to inhibit specific hormonal or inflammatory pathways.
Technical Context
Competitive antagonists bind reversibly to the same receptor site as the natural ligand, with their effect depending on the relative concentrations of agonist and antagonist. Non-competitive antagonists bind irreversibly or at allosteric sites, reducing maximal receptor response regardless of agonist concentration. In peptide therapeutics, GnRH antagonists (cetrorelix, ganirelix, degarelix, relugolix, elagolix) provide immediate gonadotropin suppression without flare. Icatibant competitively antagonises bradykinin B2 receptors. The choice between agonist and antagonist strategies depends on the target biology — GnRH agonists exploit downregulation while antagonists exploit direct blockade.