Discovery of a Lead Brain-Penetrating Gonadotropin-Releasing Hormone Receptor Antagonist with Saturable Binding in Brain

ChemMedChem. 2020 Sep 3;15(17):1624-1628. doi: 10.1002/cmdc.202000256. Epub 2020 Aug 10.

Abstract

We report the synthesis, radiosynthesis and biological characterisation of two gonadotropin-releasing hormone receptor (GnRH-R) antagonists with nanomolar binding affinity. A small library of GnRH-R antagonists was synthesised in 20-67 % overall yield with the aim of identifying a high-affinity antagonist capable of crossing the blood-brain barrier. Binding affinity to rat GnRH-R was determined by autoradiography in competitive-binding studies against [125 I]buserelin, and inhibition constants were calculated by using the Cheng-Prusoff equation. The radioligands were obtained in 46-79 % radiochemical yield and >95 % purity and with a molar activity of 19-38 MBq/nmol by direct nucleophilic radiofluorination. Positron emission tomography imaging in rat under baseline conditions in comparison to pretreatment with a receptor-saturating dose of GnRH antagonist revealed saturable uptake (0.1 %ID/mL) into the brain.

Keywords: GnRH; GnRH−R; PET; elagolix; fluorine-18.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Binding Sites / drug effects
  • Brain / drug effects*
  • Brain / metabolism
  • Dose-Response Relationship, Drug
  • Drug Discovery*
  • Fluorine Radioisotopes
  • Hydrocarbons, Fluorinated / chemical synthesis
  • Hydrocarbons, Fluorinated / chemistry
  • Hydrocarbons, Fluorinated / pharmacology*
  • Molecular Structure
  • Positron-Emission Tomography
  • Pyrimidines / chemical synthesis
  • Pyrimidines / chemistry
  • Pyrimidines / pharmacology*
  • Radiopharmaceuticals / chemical synthesis
  • Radiopharmaceuticals / chemistry
  • Radiopharmaceuticals / pharmacology*
  • Rats
  • Receptors, LHRH / antagonists & inhibitors*
  • Receptors, LHRH / metabolism
  • Structure-Activity Relationship

Substances

  • Fluorine Radioisotopes
  • Hydrocarbons, Fluorinated
  • Pyrimidines
  • Radiopharmaceuticals
  • Receptors, LHRH
  • elagolix