Controlling newly emerging drugs, such as synthetic cannabinoid receptor agonists (SCRAs), remains a never-ending challenge. They are typically abused for their psychoactive effects, related to their cannabinoid 1 (CB1) receptor activity. To evade control measures, for instance the 2021 Chinese class-wide ban, SCRAs with previously unknown structural features have appeared on the recreational drug market, e.g. the recently detected ADB-FUBIATA and “OXIZID” SCRAs. Both are not covered by this new ban, as ADB-FUBIATA carries an additional methylene group between the core and the linker and the OXIZIDS carry a previously unknown oxoindolin core. This study is the first to pharmacologically characterize these compounds at both cannabinoid receptors (CB1 & CB2). Furthermore, 2 samples seized by the Belgian customs and confirmed to contain ADB-FUBIATA and BZO-4en-POXIZID, were analytically and pharmacologically characterized.

Live cell-based assays were used to evaluate potency and efficacy. In short, activation of the receptor, fused to an inactive subunit of a split nanoluciferase, results in recruitment of the intracellular protein βarr2, linked to the other subunit. This leads to functional complementation of the enzyme and a measurable luminescent signal. The seized samples containing either ADB-FUBIATA and BZO-4en-POXIZID were characterized using multiple analytical techniques such as LC-QTOF-MS, GC-MS, HLPC-DAD, FTIR and NMR.

All compounds activated CB1. Focusing on the OXIZID SCRAs, the n-hexyl OXIZID analog BZO-HEXOXIZID was the least potent and efficacious of the set. Shortening the tail structure to a pentyl tail (BZO-POXIZID and its fluorinated counterpart 5F-BZO-POXIZID) resulted in increased potency and efficacy at both CB1 and CB2, however this increase was far less pronounced in case of an unsaturated pentenyl tail (BZO-4en-POXIZID). Overall, the cyclohexyl methyl analog BZO-CHMOXIZID had the highest potency and relative efficacy at both receptors. All OXIZID SCRAs were found to have a preference for CB2. On the other hand, ADB-FUBIATA had a moderate potency and efficacy at CB1. Interestingly, it failed to activate CB2, but showed antagonistic properties at high concentrations. Based on the activity data, compared to the respective reference standard, a high purity of the seized samples could be assumed. Analytical characterization revealed that the ADB-FUBIATA powder contained an impurity, of which the exact chemical structure could not be fully identified. The presence of the fluorophenyl indole structure, also present in ADB-FUBIATA, was confirmed by NMR but the identity of the head group could not be determined.

This characterization of previously unknown SCRAs will contribute to a broader insight into the properties of recently detected substances. It remains difficult to predict to what extent these compounds will become popular on the recreational drug market, but it is expected that more SCRAs containing unexpected never-seen-before structural features will sooner or later make their appearance. The information provided in this study will be of value for different fields, as it may allow to prioritize legal responses and informs about potential harms.