Putative Synthetic Cannabinoids MEPIRAPIM, 5F-BEPIRAPIM (NNL-2), and Their Analogues Are T-Type Calcium Channel (CaV3) Inhibitors

ACS Chem Neurosci. 2022 May 4;13(9):1395-1409. doi: 10.1021/acschemneuro.1c00822. Epub 2022 Apr 20.


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 (CaV3) 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 CaV3 assays. Several compounds showed micromolar affinities for CB1 and/or CB2, with several functioning as low potency agonists of CB1 and CB2 in a membrane potential assay. 5F-BEPIRAPIM and four other derivatives were identified as potential CaV3 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 CB1 receptor activity.

Keywords: BEPIRAPIM; MEPIRAPIM; NNL; calcium channel; cannabinoid; pharmacology.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calcium Channels, T-Type*
  • Cannabinoid Receptor Agonists / pharmacology
  • Cannabinoids* / chemistry
  • Cannabinoids* / pharmacology
  • Hypothermia*
  • Indazoles / pharmacology
  • Mice
  • Receptor, Cannabinoid, CB1
  • Receptor, Cannabinoid, CB2
  • Receptors, Cannabinoid


  • Calcium Channels, T-Type
  • Cannabinoid Receptor Agonists
  • Cannabinoids
  • Indazoles
  • Receptor, Cannabinoid, CB1
  • Receptor, Cannabinoid, CB2
  • Receptors, Cannabinoid