Putative Synthetic Cannabinoids MEPIRAPIM, 5F-BEPIRAPIM (NNL-2), and Their Analogues Are T-Type Calcium Channel (Ca_V3) Inhibitors

Abstract

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.

Defining Steric Requirements at CB1 and CB2 Cannabinoid Receptors Using Synthetic Cannabinoid Receptor Agonists 5F-AB-PINACA, 5F-ADB-PINACA, PX-1, PX-2, NNL-1, and Their Analogues

“…Similarly, pyrrolidine derivatives 5F-PY-PICA ( 32 ) and 5F-PY-PINACA ( 33 ) were sold as NPS but found to have negligible cannabimimetic activity in vitro and in mice . Most recently, piperazine analogues MEPIRAPIM ( 34 ) and 5F-BEPIRAPIM ( 35 ) demonstrated minimal activity as CB 1 agonists in vitro, but possessed unexpected off-target activity at T-type calcium channels . It is worth noting that relatively little is known about the potential off targets of most SCRAs and the relevance of such polypharmacology for the in vivo profiles of SCRAs.…”

“…72 Most recently, piperazine analogues MEPIRAPIM (34) and 5F-BEPIRAPIM (35) demonstrated minimal activity as CB 1 agonists in vitro, but possessed unexpected off-target activity at T-type calcium channels. 82 It is worth noting that relatively little is known about the potential off targets of most SCRAs and the relevance of such polypharmacology for the in vivo profiles of SCRAs. For selected SCRAs, confirmed interactions with noncannabinoid targets include various 5-HT receptors (1A, 2B, 2C, and 6), 37,83 GPR18 and GPR55, 20,24 M1, 37 GABA-A, 37 hERG channels, 37 and T-type calcium channels.…”

Off-target pharmacological profiling of synthetic cannabinoid receptor agonists including AMB-FUBINACA, CUMYL-PINACA, PB-22, and XLR-11

“…JWH-030, an early-generation partial CB1 and CB2 receptor agonist, inhibits hERG channel current, albeit with relatively low affinity, and may prolong cardiac QT intervals in rats, leading to arrhythmia ( 43 ). Moreover, some putative SCRAs related to MEPIRAPIM inhibit voltage-gated T-type calcium (Ca V 3) channels ( 44 ). Other actions such as enzyme induction and inhibition also require further consideration and investigation, particularly in combination with common medications that may be susceptible to adverse pharmacokinetic interactions.…”

MEPIRAPIM-derived synthetic cannabinoids inhibit T-type calcium channels with divergent effects on seizures in rodent models of epilepsy

“…Several endogenous, plant-derived, and synthetic cannabinoids inhibit T-type channels in vitro suggesting that cannabinoid ligands provide promising scaffolds with which to design novel Ca v 3 inhibitors ( Chemin et al, 2001 ; Mirlohi et al, 2021 ; Mirlohi et al, 2022 ). MEPIRAPIM, a putative synthetic cannabinoid receptor agonist (SCRA), and its analogues were recently described as inhibitors of Ca v 3 subtypes ( Kevin et al, 2022 ). An issue with most SCRAs is that they have potent effects on cannabinoid CB 1 receptors leading to central and peripheral toxicities ( Courts et al, 2016 ; Alipour et al, 2019 ).…”

“…An issue with most SCRAs is that they have potent effects on cannabinoid CB 1 receptors leading to central and peripheral toxicities ( Courts et al, 2016 ; Alipour et al, 2019 ). However, we recently made the surprising discovery that MEPIRAPIM and several analogues display negligible activity at CB 1 receptors, thus opening the possibility that this chemical scaffold could be exploited to develop novel, selective Ca v 3 inhibitors ( Kevin et al, 2022 ).…”