Diastereomer-Dependent Modulation of Atypical Chemokine Receptor 3 (ACKR3) in 3-Azabicyclo[3.1.0]hexane-Based Ligands

<jats:p>Atypical chemokine receptor 3 (ACKR3) is a β-arrestin-biased scavenger receptor that is involved in cancer and inflammatory diseases. Motivated by the clinical development of the ACKR3 ligand ACT-1004-1239 for multiple sclerosis (MS), we designed conformationally restricted analogues through scaffold rigidification to probe ACKR3 pharmacology, explore opportunities for improved ACKR3/hERG selectivity, and enable molecular modeling studies in the face of limited ACKR3 structural information. This strategy yielded a pair of bicyclic diastereomers, VUF26199 and VUF26200, with a remarkable 50-fold difference in ACKR3 affinity. The high affinity diastereomer VUF26200 (pIC50 = 7.3) acts as an inverse agonist and inhibits ACKR3-mediated CXCL12 uptake in a concentration-dependent manner. While rigidification did not improve ACKR3/hERG selectivity, these more rigid ligands constitute valuable probes for studying ACKR3 and uncovered a pronounced stereochemical determinant of receptor recognition. Molecular modeling with these compounds further provides new insight into ligand–receptor interactions within this series.</jats:p>