Meeting Report: Metabolites in Safety Testing (MIST) Symposium—Safety Assessment of Human Metabolites: What’s REALLY Necessary to Ascertain Exposure Coverage in Safety Tests?

Abstract

Abstract. In the 2012 AAPS metabolites in safety testing (MIST) symposium held in Chicago, IL, USA, on October 15, 2012, regulatory experts and industrial scientists joined together to discuss their perspectives and strategies in addressing contemporary MIST recommendations (FDA 2008, International Conference on Harmonization (ICH) M3(R2), ICH M(R2) Q&A). Overall, these regulatory guidances indicate that metabolites identified in human plasma should circulate at similar or greater concentrations in at least one of the animal species used in nonclinical safety assessment of the parent drug. However, synthetic standards for the metabolites often do not exist or they are intractable to synthesize, thus introducing multiple challenges in drug development for the quantitative comparison of metabolites between human and animals. A tiered bioanalytical strategy for metabolite analysis is a prevalent approach to demonstrate coverage in animals. Recent developments in bioanalytical methodology have yielded several time-and resource-sparing strategies to provide fit-for-purpose approaches that can enable critical decisions related to metabolite quantification and monitoring in plasma. This report summarizes the presentations and panel discussions at the symposium.KEY WORDS: MIST; safety assessment of human metabolites; metabolite exposure coverage in safety test; ICH M3(R2); LC/MS/MS.

A decade of drug metabolite safety testing: industry and regulatory shared learning

“…The FDA has provided helpful recommendations on a case-by-case basis, especially when metabolite standards are not available and when metabolite exposure estimates must be limited to fit-for-purpose bioanalytical approaches [20]. Although many sponsors have become familiar with metabolite safety testing guidelines over more than a decade, only proactive and ongoing communication with regulators can prevent delays.…”

Late-occurring and Long-circulating Metabolites of GABAAα2,3 Receptor Modulator AZD7325 Involving Metabolic Cyclization and Aromatization: Relevance to MIST Analysis and Application for Patient Compliance

“…Since 2008, quantitative assessment of exposure coverage of human metabolites in safety testing animals has been recommended by regulatory agencies (Gao et al, 2013;Timmerman et al, 2016), apparently derived from an earlier initiative by the pharmaceutical industry on drug metabolites in safety testing (MIST; Baillie et al, 2002). Both the revised guidance by the US Food and Drug Administration in 2016 (https://www.fda.gov/downloads/drugs/guidancecomplianceregulatoryinformation/guidances/ucm079266.pdf) and the ICH guideline M3(R2) that was previously adopted by the European Medicines Agency (http://www.ema.europa.eu/docs/en_GB/ document_library/Scientific_guideline/2009/09/WC500002720.pdf) have recommend an adequate exposure coverage in preclinical animal species for human metabolites observed at exposures greater than 10% of the total drug-related exposure.…”

“…Various analytical approaches alternate to quantitative bioanalysis have been practiced for MIST by pharmaceutical industry laboratories. LC-MS-based approaches without the need of metabolite standards have been nicely summarized in the literature (Ma and Chowdhury, 2011;Gao et al, 2013). One approach adjusts the LC-MS signal of a metabolite with its MS signal response factor relative to the parent drug, as determined by correlating the MS and radiochromatographic signal responses in radiolabeled metabolite studies (Yu et al, 2007;Yi and Luffer-Atlas, 2010).…”

“…Instead, some interesting findings arise from the analysis of drug metabolites of AZD7325 after repeated doses, i.e., the MIST analysis at steady state as recommend by the United States regulatory agency (Gao et al, 2013). It has been known in the literature that the level and ratio of metabolites at steady state may be different from that after a single dose (Griffini et al, 2010;Gong et al, 2016).…”

“…O-Glucuronidation and O-sulfation reactions make a metabolite more water soluble and pharmacologically inactive, thus these conjugate metabolites do not need to be further evaluated across species (Gao et al, 2013). LC-MS chromatographic profiles of the conjugate metabolites are still presented to provide a little more comprehensive picture of the AZD7325 metabolism (Figs.…”