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

Abstract

IntroductionSynthetic cannabinoid receptor agonists (SCRAs) are a diverse class of new psychoactive substances that have been associated with multiple instances and types of toxicity. Some SCRAs appear to carry a greater toxicological burden than others, or compared to the prototypical cannabis-derived agonist Δ9-tetrahydrocannabinol (Δ9-THC), despite a common primary mechanism of action via cannabinoid 1 (CB1) receptors. “Off-target” (i.e., non-CB1 receptor) effects could underpin this differential toxicity, although there are limited data around the activity of SCRAs at such targets.MethodsA selection of 7 SCRAs (AMB-FUBINACA, XLR11, PB-22, AKB-48, AB-CHMINICA, CUMYL-PINACA, and 4F-MDMB-BUTINACA), representing several distinct chemotypes and toxicological profiles, underwent a 30 μM single-point screen against 241 G protein-coupled receptor (GPCR) targets in antagonist and agonist mode using a cellular β-arrestin recruitment assay. Strong screening “hits” at specific GPCRs were followed up in detail using concentration-response assays with AMB-FUBINACA, a SCRA with a particularly notable history of toxicological liability.ResultsThe single-point screen yielded few hits in agonist mode for any compound aside from CB1 and CB2 receptors, but many hits in antagonist mode, including a range of chemokine receptors, the oxytocin receptor, and histamine receptors. Concentration-response experiments showed that AMB-FUBINACA inhibited most off-targets only at the highest 30 μM concentration, with inhibition of only a small subset of targets, including H1 histamine and α2B adrenergic receptors, at lower concentrations (≥1 μM). AMB-FUBINACA also produced concentration-dependent CB1 receptor signaling disruption at concentrations higher than 1 μM, but did not produce overt cytotoxicity beyond CP55,940 or Δ9-THC in CB1 expressing cells.DiscussionThese results suggest that while some “off-targets” could possibly contribute to the SCRA toxidrome, particularly at high concentrations, CB1-mediated cellular dysfunction provides support for hypotheses concerning on-target, rather than off-target, toxicity. Further investigation of non-GPCR off-targets is warranted.

Evaluating signaling bias for synthetic cannabinoid receptor agonists at the cannabinoid CB2 receptor

“…Systematic structural comparison of SCRAs for both in vitro and in vivo activity has thus far failed to reveal a clear link between molecular pharmacology and toxicity, even in cases of significant bias, 14,19–21,24,41,63,64,66–70 although this does not rule out the involvement of CB 1 and CB 2 in the toxicity of SCRAs. Off‐target activity is also being explored as contributors to the complex side‐effect profile of SCRAs, with confirmed interactions with the 5‐HT (namely subtypes 1A, 2B, 2C, and 6), GABA, GPR18, GPR55 and muscarinic acetylcholine receptors, 71–74 and T‐type calcium channels 17,75 . Additional considerations in the enhanced toxicity of SCRAs include the formation of toxic thermal degradants 76,77 and active metabolites 78–80 …”

“…Studies thus far have mainly focused on the pharmacology of SCRAs at CB 1 , as this receptor is considered primarily responsible for the psychoactive effects of cannabinoids in humans. However, the extensive array of behavioral and physiological effects encountered upon SCRA abuse, including cardiac, gastro‐intestinal, and respiratory symptoms, suggests the involvement of other targets 17,18 . Many SCRAs possess an affinity for CB 2 that is equivalent or higher than for CB 1 , questioning the involvement of this receptor in SCRA toxicity 14,19–24 .…”

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

“…24 As such, the effect of n-hexyl substitution on cannabinoid receptor activity is relevant not only to the recently detected NPSs but also to divergent chemotypes currently appearing. The modification of related n-pentyl tail homologues (MDMB-PINACA, 7) has given rise to n-pentenyl bearing species such as MDMB-4en-PINACA (8), a problematic SCRA associated with multiple fatalities, and as such, the examination of the n-hexenyl tail in this context is also necessary (Figure 2). 26−36 CB 1 is the most abundant G protein-coupled receptor (GPCR) in the human central nervous system and plays an integral role in neuronal homeostasis via retrograde signaling to modulate excitatory and inhibitory neurotransmission.…”

“…Synthetic cannabinoid receptor agonists (SCRAs) continue to appear as a major class of new psychoactive substances (NPSs). Designed to emulate the functional effects of Δ 9 -tetrahydrocannabinol (THC, 1 ), SCRAs accounted for 130 of the total 618 NPS on the market in 2021 worldwide, and over half (24/41) of the total NPSs detected in the European Union in 2022. − SCRAs account for over 8300 individual seizures reported to the United Nations Office on Drugs and Crime between 2011 and 2023, with the class comprising over 350 detected compounds. , Unlike THC, many SCRAs act as high-potency and high-efficacy agonists of cannabinoid receptors 1 (CB 1 ) and 2 (CB 2 ), with central activation of CB 1 thought to be primarily responsible for the toxicological profiles associated with use of these substances. − Rapid structural iteration of SCRAs remains a global issue, with a significant uptick in chemical diversity since 2021. , This is associated with increased restrictions placed on the manufacture of typical SCRA chemotypes such as N -alkyl-indole-, indazole-, and 7-azaindole-3-carboxamides by the Government of the People’s Republic of China . While scheduling changes have impacted the discovery and/or popularization of novel SCRA scaffolds, detections of older chemotypes, in particular, indole- and indazole-3-carboxamides, remain a feature of the current SCRA landscape. − …”

“…45 As such, Figure 1. Cannabinoid receptor ligands Δ 9 -tetrahydrocannabinol (1), JWH-018 (2), MDMB-BUTINACA (3), EDMB-PINACA (4), ADB-HEXINACA (5), BZO-HEXOXIZID (6), MDMB-PINACA (7), and MDMB-4en-PINACA (8). investigation of potential SCRAs as cannabinoid receptor agonists offers insights into their differential CB 1 activating potential and may inform future efforts in the understanding of cannabinoid receptor activity.…”