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J Anal Toxicol. 2014 Sep;38(7):427-31. doi: 10.1093/jat/bku049. Epub 2014 Jun 7.

Enzyme-linked immunosorbent assay (ELISA) for the detection of use of the synthetic cannabinoid agonists UR-144 and XLR-11 in human urine.

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  • 1The Center for Forensic Science Research and Education, Willow Grove, PA, USA.
  • 2NMS Labs, Willow Grove, PA 18901, USA.
  • 3Tulip Biolabs, Inc., West Point, PA 19486, USA.
  • 4The Center for Forensic Science Research and Education, Willow Grove, PA, USA NMS Labs, Willow Grove, PA 18901, USA


Ongoing changes in the synthetic cannabinoid drug market create the need for relevant targeted immunoassays for rapid screening of biological samples. We describe the validation and performance characteristics of an enzyme-linked immunosorbent assay designed to detect use of one of the most prevalent synthetic cannabinoids in urine, UR-144, by targeting its pentanoic acid metabolite. Fluorinated UR-144 (XLR-11) has been demonstrated to metabolize to this common product. The assay has significant cross-reactivity with UR-144-5-OH, UR-144-4-OH and XLR-11-4-OH metabolites, but <10% cross-reactivity with the parent compounds, and no measurable cross-reactivity with other synthetic cannabinoids and their metabolites at concentrations of <1,000 ng/mL. The assay's cutoff is 5 ng/mL relative to the pentanoic acid metabolite of UR-144, which is used as the calibrator. The method was validated with 90 positive and negative control urine samples for UR-144, XLR-11 and its metabolites tested versus liquid chromatography-tandem mass spectrometry. The accuracy, sensitivity and specificity were determined to be 100% for the assay at the specified cutoff.

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