Putative Synthetic Cannabinoids MEPIRAPIM, 5F-BEPIRAPIM (NNL-2), and Their Analogues Are T-Type Calcium Channel (Ca V 3) Inhibitors.

Synthetic cannabinoid receptor agonists (SCRAs) are a large and growing class of new psychoactive substances (NPSs). Two recently identified compounds, MEPIRAPIM and 5F-BEPIRAPIM (NNL-2), have not been confirmed as agonists of either cannabinoid receptor subtype but share structural similarities with both SCRAs and a class of T-type calcium channel (Ca V 3) inhibitors under development as new treatments for epilepsy and pain. In this study, MEPIRAPIM and 5F-BEPIRAPIM and 10 systematic analogues were synthesized, analytically characterized, and pharmacologically evaluated using in vitro cannabinoid receptor and Ca V 3 assays. Several compounds showed micromolar affinities for CB 1 and/or CB 2 , with several functioning as low potency agonists of CB 1 and CB 2 in a membrane potential assay. 5F-BEPIRAPIM and four other derivatives were identified as potential Ca V 3 inhibitors through a functional calcium flux assay (>70% inhibition), which was further confirmed using whole-cell patch-clamp electrophysiology. Additionally, MEPIRAPIM and 5F-BEPIRAPIM were evaluated in vivo using a cannabimimetic mouse model. Despite detections of MEPIRAPIM and 5F-BEPIRAPIM in the NPS market, only the highest MEPIRAPIM dose (30 mg/kg) elicited a mild hypothermic response in mice, with no hypothermia observed for 5F-BEPIRAPIM, suggesting minimal central CB 1 receptor activity.