In vitro Phase I metabolism of indazole carboxamide synthetic cannabinoid MDMB-CHMINACA via human liver microsome incubation and high-resolution mass spectrometry

Abstract

Synthetic cannabinoids have proliferated over the last decade and have become a major public health and analytical challenge, critically impacting the clinical and forensic communities. Indazole carboxamide class synthetic cannabinoids have been particularly rampant, and exhibit severe toxic effects upon consumption due to their high binding affinity and potency at the cannabinoid receptors (CB₁ and CB₂ ). MDMB-CHMINACA, methyl 2-[1-(cyclohexylmethyl)-1H-indazole-3-carboxamido]-3,3-dimethylbutanoate, a compound of this chemical class, has been identified in forensic casework and is structurally related to several other synthetic cannabinoids. This study presents the first extensive report on the Phase I metabolic profile of MDMB-CHMINACA, a potent synthetic cannabinoid. The in vitro metabolism of MDMB-CHMINACA was determined via incubation with human liver microsomes and high-resolution mass spectrometry. The accurate masses of precursor and fragments, mass error (ppm), and chemical formula were obtained for each metabolite. Twenty-seven metabolites were identified, encompassing twelve metabolite types. The major biotransformations observed were hydroxylation and ester hydrolysis. Hydroxylations were located predominantly on the cyclohexylmethyl (CHM) moiety. Ester hydrolysis was followed by additional biotransformations, including dehydrogenation; mono- and dihydroxylation and ketone formation, each with dehydrogenation. Minor metabolites were identified and reported. The authors propose that CHM-monohydroxylated metabolites specific to MDMB-CHMINACA are the most suitable candidates for implementation into bioanalytical assays to demonstrate consumption of this synthetic cannabinoid. Due to the structural similarity of MDMB-CHMINACA and currently trending synthetic cannabinoids whose metabolic profiles have not been reported, the results of this study can be used as a guide to predict their metabolic pathways.

Keywords: MDMB-CHMINACA; drug metabolism; forensic toxicology; high-resolution mass spectrometry; synthetic cannabinoids.