Synthesis and Functional Evaluation of Synthetic Cannabinoid Receptor Agonists Related to ADB-HEXINACA

ADB-HEXINACA has been recently reported as a synthetic cannabinoid receptor agonist (SCRA), one of the largest classes of new psychoactive substances (NPSs). This compound marks the entry of the n-hexyl tail group into the SCRA landscape, which has continued in the market with recent, newly detected SCRAs. As such, a proactive characterization campaign was undertaken, including the synthesis, characterization, and pharmacological evaluation of ADB-HEXINACA and a library of 41 closely related analogues. Two in vitro functional assays were employed to assess activity at CB₁ and CB₂ cannabinoid receptors, measuring G_βγ-coupled agonism through a fluorescence-based membrane potential assay (MPA) and β-arrestin 2 (βarr2) recruitment via a live cell-based nanoluciferase complementation reporter assay. ADB-HEXINACA was a potent and efficacious CB₁ agonist (CB₁ MPA pEC₅₀ = 7.87 ± 0.12 M; E_max = 124 ± 5%; βarr2 pEC₅₀ = 8.27 ± 0.14 M; E_max = 793 ± 42.5), as were most compounds assessed. Isolation of the heterocyclic core and alkyl tails allowed for the comprehensive characterization of structure-activity relationships in this compound class, which were rationalized in silico via induced fit docking experiments. Overall, most compounds assessed are possibly emerging NPSs.