Bioanalytical challenges and strategies for accurately measuring acyl glucuronide metabolites in biological fluids

Abstract

Bioanalysis of unstable compounds such as acyl glucuronide metabolites represents a great analytical challenge owing to poor analyte stability in biological matrices. The primary goal for bioanalytical assay development is to minimize the breakdown of acyl glucuronide metabolite into its parent aglycone during sample collection, transportation, storage and analysis. Samples need to be stabilized ex vivo immediately after sample collection to minimize potential breakdown and thus to ensure accurate concentration measurement of both acyl glucuronide metabolite and its parent aglycone. In this review paper, formation of acyl glucuronide metabolites, the importance of establishing acyl glucuronide exposure measurement and safety coverage, optimization of sample pretreatment to stabilize the acyl glucuronide metabolites, current analytical strategy of assaying them as well as considerations for regulatory filings are discussed. It is important to identify acyl glucuronide metabolites that are capable of undergoing hydrolysis and pH‐dependent intra‐molecular migration as well as covalently binding to plasma and tissue proteins which can cause toxicity in vivo in the early stages of drug development. Carefully planning analytical experiments, identifying structures of acyl glucuronides and monitoring their concentrations in early drug development can help assess the risks associated with their exposures and potentially predict their concentrations in human circulation.

Personalized Therapy for Mycophenolate: Consensus Report by the International Association of Therapeutic Drug Monitoring and Clinical Toxicology

“…Unfortunately, ex vivo investigation on AcMPAG effects is complicated because of its limited stability in blood samples. 31 Importantly, local concentrations in gut rather than plasma concentrations are more likely to account for gastrointestinal toxicity. 32 Therefore, the current evidence available does not justify the measurement of AcMPAG concentration in routine practice.…”

Mass Spectrometry Imaging of Diclofenac and Its Metabolites in Tissues Using Nanospray Desorption Electrospray Ionization.

“…The pH-dependent degradation and difficulties of characterizing acyl glucuronides have been previously explored in the literature. 58 Regardless, both experiments generally agree that HD is present in higher abundance in kidney than AG. Meanwhile AG is in higher abundance than HD in liver for both the LC-MS/MS and nano-DESI analyses.…”

Absorption, Distribution, Metabolism, and Excretion of [14C]iptacopan in Healthy Male Volunteers and in In Vivo and In Vitro Studies

“…Samples were pooled across all subjects to give single representative samples. Profiles of radioactive parent and metabolites in plasma, including key parameters [e.g., area under the concentration-time curve from time 0 to 48 h (AUC 0-48 ), AUC inf , and T 1/2 ] where possible, were performed in acidified plasma (1) to prevent acyl migration of acyl glucuronide metabolites (Patel, 2020) and (2) because there was no significant difference in the PK of iptacopan obtained in acidified and non-acidified samples.…”