Pharmacokinetics, metabolism and off-target effects in the rat of 8-[(1H- benzotriazol-1-yl)amino]octanoic acid, a selective inhibitor of human cytochrome P450 4Z1: β-oxidation as a potential augmenting pathway for inhibition

Abstract

1. 8‐[(1H‐1,2,3‐benzotriazol‐1‐yl)amino]octanoic acid (8-BOA) was recently identified as a selective and potent mechanism-based inactivator (MBI) of breast cancer-associated CYP4Z1 and exhibited favourable inhibitory activity in vitro, thus meriting in vivo characterization.

2. The pharmacokinetics and metabolism of 8-BOA in rats was examined after a single IV bolus dose of 10 mg/kg. A biphasic time-concentration profile resulted in relatively low clearance and a prolonged elimination half-life.

3. The major circulating metabolites identified in plasma were products of β-oxidation; congeners losing two and four methylene groups accounted for >50% of metabolites by peak area. The –(CH₂)₂ product was characterized previously as a CYP4Z1 MBI and so represents an active metabolite that may contribute to the desired pharmacological effect.

4. Ex vivo analysis of total CYP content in rat liver and kidney microsomes showed that off-target CYP inactivation was minimal; liver microsomal probe substrate metabolism also demonstrated low off-target inactivation. Standard clinical chemistries provided no indication of acute toxicity.

5. In silico simulations using the free concentration of 8-BOA in plasma suggested that the in vivo dose used here may effectively inactivate CYP4Z1 in a xenografted tumour.

Keywords:

• Cytochrome P450 4Z1
• mechanism-based inhibitor
• bioactivation
• breast cancer
• rat
• fatty acid
• β-oxidation
• leaky hosepipe

Acknowledgements

The authors thank Dale Whittington and Dr. J. Scott Edgar for mass spectrometry assistance and Dr. Brian Baer for useful drug metabolism discussions. The authors recognize Dr. Ellen Joy Plein, who throughout a long career contributed greatly to the University of Washington School of Pharmacy. The Plein endowed funds that were established have enabled many research opportunities, including the study presented here.

Disclosure statement

The authors report no conflict of interest.