Characterization of Cytochrome P450-Mediated Metabolism of Δ8-tetrahydrocannabinol in vitro
- 1University of Washington
Abstract
{Delta}-tetrahydrocannabinol ({Delta}8-THC) is a pharmacologically active isomer of {Delta}9-THC, the main psychoactive component of cannabis. {Delta}8-THC use has increased rapidly, but the metabolism of {Delta}8-THC has been incompletely characterized. This study identified metabolites of {Delta}8-THC formed by cytochrome P450 (CYP) enzymes in human liver microsomes (HLM), assigned the main CYPs responsible for the metabolic pathways, and evaluated the impact of genetic polymorphisms on {Delta}8-THC metabolism in vitro. Five monohydroxylated {Delta}8-THC metabolites, identified as 11-OH-{Delta}8-THC, two aliphatic side-chain hydroxylated products (M1, M2), and two ring hydroxylated products (M3, M4) were detected in HLM. 11-OH-{Delta}8-THC was the most abundant metabolite. Unbound binding constants for metabolite formation in HLM ranged from 3.6 nM to >121 nM, suggesting multiple enzymes contribute to {Delta}8-THC metabolism. The contributing enzymes were identified using recombinant CYPs, inhibition studies, and correlation analyses. 11-OH-{Delta}8-THC was predominantly formed by CYP2C9 with a minor contribution from CYP2C19. CYP2C9 genotype-based activity scores across donors correlated with 11-OH-{Delta}8-THC formation (p = 0.0315). An 80% decrease in 11-OH-{Delta}8-THC formation clearance was predicted in CYP2C9*3/*3 carriers. The ring-hydroxylated M3 and M4 were mainly formed by CYP3A. CYP2D6, CYP1A2, and CYP3A4 activities were associated with formation of the pentyl side-chain oxidized metabolites M1 and M2. Although C11 hydroxylation appeared more important metabolic pathway for {Delta}8-THC than for {Delta}9-THC, the catalytic efficiency of CYP2C9 towards {Delta}8-THC was lower than towards {Delta}9-THC. In the presence of CYP2C9 inhibitors or genetic polymorphisms, {Delta}8-THC clearance is likely mediated by CYP3A4 and CYP2C19. This study shows that 11-OH-{Delta}8-THC, a psychoactive metabolite, is the primary oxidation product of {Delta}8-THC in HLM and that CYP2C9 predominantly catalyzes its formation. This work expands the limited literature on {Delta}8-THC metabolism, and shows that reduced-function CYP2C9 variants substantially impair formation of 11-OH-{Delta}8-THC. The characterization of {Delta}8-THC metabolism in HLM provides the foundation for risk assessment of drug-drug interactions and establishes the metabolic profile of {Delta}8-THC in the human liver.
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BibTeX
@misc{simon2026characterization,
title = {{Characterization of Cytochrome P450-Mediated Metabolism of Δ8-tetrahydrocannabinol in vitro}},
author = {K. Simon and Y. W. Wen and Y. E. Dong and A. Authement and J. Chen and K. E. Thummel and N. Isoherranen},
howpublished = {bioRxiv},
year = {2026},
month = oct,
doi = {10.64898/2026.10.12.758575},
url = {https://www.biorxiv.org/content/10.64898/2026.10.12.758575v1},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - Characterization of Cytochrome P450-Mediated Metabolism of Δ8-tetrahydrocannabinol in vitro
AU - K. Simon
AU - Y. W. Wen
AU - Y. E. Dong
AU - A. Authement
AU - J. Chen
AU - K. E. Thummel
AU - N. Isoherranen
PY - 2026
DA - 2026/10/12
PB - bioRxiv
DO - 10.64898/2026.10.12.758575
UR - https://www.biorxiv.org/content/10.64898/2026.10.12.758575v1
AB - {Delta}-tetrahydrocannabinol ({Delta}8-THC) is a pharmacologically active isomer of {Delta}9-THC, the main psychoactive component of cannabis. {Delta}8-THC use has increased rapidly, but the metabolism of {Delta}8-THC has been incompletely characterized. This study identified metabolites of {Delta}8-THC formed by cytochrome P450 (CYP) enzymes in human liver microsomes (HLM), assigned the main CYPs responsible for the metabolic pathways, and evaluated the impact of genetic polymorphisms on {Delta}8-THC metabolism in vitro. Five monohydroxylated {Delta}8-THC metabolites, identified as 11-OH-{Delta}8-THC, two aliphatic side-chain hydroxylated products (M1, M2), and two ring hydroxylated products (M3, M4) were detected in HLM. 11-OH-{Delta}8-THC was the most abundant metabolite. Unbound binding constants for metabolite formation in HLM ranged from 3.6 nM to >121 nM, suggesting multiple enzymes contribute to {Delta}8-THC metabolism. The contributing enzymes were identified using recombinant CYPs, inhibition studies, and correlation analyses. 11-OH-{Delta}8-THC was predominantly formed by CYP2C9 with a minor contribution from CYP2C19. CYP2C9 genotype-based activity scores across donors correlated with 11-OH-{Delta}8-THC formation (p = 0.0315). An 80% decrease in 11-OH-{Delta}8-THC formation clearance was predicted in CYP2C9*3/*3 carriers. The ring-hydroxylated M3 and M4 were mainly formed by CYP3A. CYP2D6, CYP1A2, and CYP3A4 activities were associated with formation of the pentyl side-chain oxidized metabolites M1 and M2. Although C11 hydroxylation appeared more important metabolic pathway for {Delta}8-THC than for {Delta}9-THC, the catalytic efficiency of CYP2C9 towards {Delta}8-THC was lower than towards {Delta}9-THC. In the presence of CYP2C9 inhibitors or genetic polymorphisms, {Delta}8-THC clearance is likely mediated by CYP3A4 and CYP2C19. This study shows that 11-OH-{Delta}8-THC, a psychoactive metabolite, is the primary oxidation product of {Delta}8-THC in HLM and that CYP2C9 predominantly catalyzes its formation. This work expands the limited literature on {Delta}8-THC metabolism, and shows that reduced-function CYP2C9 variants substantially impair formation of 11-OH-{Delta}8-THC. The characterization of {Delta}8-THC metabolism in HLM provides the foundation for risk assessment of drug-drug interactions and establishes the metabolic profile of {Delta}8-THC in the human liver.
ER -