Discovery of WLB-89462, a New Drug-like and Highly Selective σ₂ Receptor Ligand with Neuroprotective Properties

The synthesis and pharmacological activity of a new series of isoxazolylpyrimidines as sigma-2 receptor (σ₂R) ligands are reported. Modification of a new hit retrieved in an HTS campaign allowed the identification of the compound WLB-89462 (20c) with good σ₂R affinity (K_i = 13 nM) and high selectivity vs both the σ₁R (K_i = 1777 nM) and a general panel of 180 targets. It represents one of the first σ₂R ligands with drug-like properties, linked to a good physicochemical and ADMET profile (good solubility, no CYP inhibition, good metabolic stability, high permeability, brain penetration, and high oral exposure in rodents). Compound 20c shows neuroprotective activity in vitro and improves short-term memory impairment induced by hippocampal injection of amyloid β peptide in rats. Together with the promising effects in the chronic models where 20c is currently being evaluated, these results pave the way toward its clinical development as a neuroprotective agent.