Fenethylline, also known by the trade name Captagon, is a synthetic psychoactive stimulant that has recently been linked to a substance-use disorder and ‘pharmacoterrorism’ in the Middle East1,2,3,4. Although fenethylline shares a common phenethylamine core with other amphetamine-type stimulants, it also incorporates a covalently linked xanthine moiety into its parent structure5,6. These independently active pharmacophores are liberated during metabolism, resulting in the release of a structurally diverse chemical mixture into the central nervous system7,8,9. Although the psychoactive properties of fenethylline have been reported to differ from those of other synthetic stimulants, the in vivo chemical complexity it manifests upon ingestion has impeded efforts to unambiguously identify the specific species responsible for these effects10,11. Here we develop a ‘dissection through vaccination’ approach, called DISSECTIV, to mitigate the psychoactive effects of fenethylline and show that its rapid-onset and distinct psychoactive properties are facilitated by functional synergy between theophylline and amphetamine. Our results demonstrate that incremental vaccination against a single chemical species within a multi-component mixture can be used to uncover emergent properties arising from polypharmacological activity. We anticipate that DISSECTIV will be used to expose unidentified active chemical species and resolve pharmacodynamic interactions within other chemically complex systems, such as those found in counterfeit or illegal drug preparations, post-metabolic tissue samples and natural product extracts.
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This work was supported by a grant from the NIH (DA024705-06). We thank M. Gooyit for supplying reagents, B. Ellis for assistance with tissue collection and M. Taffe for providing DEA licensing (RT0485537). This is manuscript 29481 from The Scripps Research Institute.
The authors declare no competing financial interests.
Reviewer Information Nature thanks P. Kenny, M. Pravetoni and the other anonymous reviewer(s) for their contribution to the peer review of this work.
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Extended data figures and tables
Extended Data Figure 1 General schematic demonstrating the concept behind using DISSECTIV to isolate CNS activity of single chemical species within a complex chemical mixture that elicits psychoactive effects.
Mixtures of known (solid) and unknown (dashed) chemical species are frequently observed due to active metabolite generation from a parent compound, within natural products, toxins or their extracts, and in counterfeit or clandestine production of synthetic drugs. In DISSECTIV, incremental vaccination against individual known chemical species can identify effects due to the actions of those species (A/B), effects emerging from the interaction of multiple known species (C), effects due to actions of unknown species (D) or effects emerging from the interaction of known and unknown species (E). Furthermore, while five discrete ‘all or nothing’ effects are listed here for clarity, the approach can also be used to determine the impact of each compound in altering the magnitude of each discrete effect.
a, BSA (m/z 66,134–66,284; ESI+ m/z 66,431). b, FEN–BSA (m/z 70,031–70,106). c, THEO–BSA (m/z 69,424–71,275). d, 1-A1–BSA (m/z 70,727–71,058). e, AMPH–BSA (m/z 69,563). Representative data shown for BSA, FEN–BSA, THEO–BSA and 1-A1–BSA; two replicates.
Extended Data Figure 3 Standard curves used to quantify the concentrations of drugs in biological tissue samples.
a, b, Standard curves for fenethylline (solid circles) at low (a, slope = 44,941 ± 1,026; r2 = 0.9806) and high (b, slope = 45,929 ± 143.1; r2 = 0.9998) concentrations in the presence of fenethylline-d3 (open circles) as an internal standard. c, d, Standard curve for theophylline (solid triangles) at low (c, slope = 93,380 ± 844.4; r2 = 0.9970) and high (d, slope = 83,746 ± 1,406; r2 = 0.9954) concentrations in the presence of theophylline-d6 (open triangles) as an internal standard. e, f, Standard curve for amphetamine (solid squares) at low (e, slope = 299,394 ± 1,980; r2 = 0.9995) and high (f, slope = 254,747 ± 16,197; r2 = 0.9898) concentrations in the presence of amphetamine-d11 (open squares) as an internal standard. All lines fit through the origin.
Extended Data Figure 4 Vaccination with FEN–KLH blunts the behavioural effects of amphetamine and methamphetamine.
a, Amphetamine (2 mg kg−1) locomotor behaviour in animals vaccinated with KLH or FEN–KLH (Pinteraction < 0.0001; F30,240 = 3.70); *P < 0.01 versus KLH, Bonferroni correction). n = 5, repeated-measures two-way ANOVA. b, Methamphetamine (2 mg kg−1) locomotor behaviour in animals vaccinated with KLH (n = 9) or FEN–KLH (n = 11) (Pinteraction = 0.0385; F30,540 = 1.52; *P < 0.01 versus KLH, Bonferroni correction). Repeated-measures two-way ANOVA. c, EPM in KLH-vaccinated animals following saline (n = 9), amphetamine (A., 2 mg kg−1, n = 10) or methamphetamine (M., 2 mg kg−1, n = 10) administration. One-way ANOVA (P = 0.1325; F2,26 = 2.187). d, EPM in FEN–KLH-vaccinated animals following saline (n = 9), amphetamine (2 mg kg−1, n = 10) or methamphetamine (2 mg kg−1, n = 10) administration. One-way ANOVA (P = 0.9588; F2,26 = 0.042). a, b, Data are presented as mean ± s.e.m. c, d, Data are shown as median with quartiles ± 10–90% CI; +, mean.
a, Midpoint titres, day 35. Dotted line is mean 1-A1–KLH titre (n = 6). b, AMPH–KLH serum binding to AMPH–BSA with competing fenethylline or amphetamine. Data are pooled from n = 6, two replicates. Dotted line is mean 1-A1–KLH + amphetamine binding. c, Total hyperlocomotion (90 min) due to fenethylline (20 mg kg−1) in KLH-vaccinated (n = 6) and AMPH–KLH-vaccinated (n = 6) animals. Dotted line is mean 1-A1–KLH + fenethylline 20 mg kg−1 locomotor response, t-test (P = 0.3584, d.f. = 9). a, c, Data are shown as median with quartiles ± 10–90% CI; +, mean). b, Data are presented as mean ± s.e.m.
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Wenthur, C., Zhou, B. & Janda, K. Vaccine-driven pharmacodynamic dissection and mitigation of fenethylline psychoactivity. Nature 548, 476–479 (2017). https://doi.org/10.1038/nature23464
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