Role of metabolites in drug-drug interactions.

A Decade in the MIST: Learnings from Investigations of Drug Metabolites in Drug Development under the "Metabolites in Safety Testing" Regulatory Guidance.

Seeing through the mist: abundance versus percentage. Commentary on metabolites in safety testing.

In 2008 the Food and Drug Administration (FDA) modified its standard for evaluating toxicity of drug metabolites defining metabolites of concern as those that are detected circulating at more than 10% of the systemic exposure level of the parent compound at steady state. GSK1018921, a novel glycine transporter 1 inhibitor, was extensively metabolized in humans, with parent compound accounting for 12% and 1% of circulating drug related material after single and repeat dose, respectively. Since the parent was present at low relative concentrations, all fifteen metabolites detected in human plasma, met the 10% metabolites in safety testing (MIST) criterion, and therefore might require extensive quantification and further evaluation. At least thirteen metabolites warranted non-clinical characterization since they were either observed at significantly greater levels in humans than in preclinical species or they were not detected in animals. However the application of alternative strategies to 2008 FDA MIST guidance, such as those suggested by scientific literature and by the recent revision of the International Conference of Harmonisation (ICH) M3 guidance which recommended providing safety coverage for metabolites greater than 10% of total drug related material, allowed us to focus on one metabolite for additional safety evaluation.

The regulatory guidances on metabolites in safety testing (MIST) by US Food and Drug Administration (FDA) and International Conference on Harmonisation (ICH) describe the necessity to assess exposures of major circulating metabolites in humans at steady state relative to exposures achieved in nonclinical safety studies prior to the initiation of large scale clinical trials. This comparison can be accomplished by measuring metabolite concentrations in animals and humans with validated bioanalytical methods. However, bioanalysis of metabolites in multiple species and multiple studies is resource intensive and may impact the timelines of clinical studies. A simple, reliable and accurate method has been developed for quantitative assessment of metabolite coverage in preclinical safety species by mixing equal volume of human plasma with blank plasma of animal species and vice versa followed by an analysis using LC-SRM or LC-HRMS. Here, we explored the reliability and accuracy of this method in several development projects at Genentech and compared the results to those obtained from validated bioanalytical methods. The mixed-matrix method provided comparable accuracy (within ±20%) to those obtained from validated bioanalysis but does not require authentic standards or radiolabeled compounds, which could translate to time and resource savings in drug development. Quantitative assessment of metabolite coverage in safety species can be made using mixed matrix method with similar accuracy and scientific rigor to those obtained from validated bioanalytical methods. Moving forward, we are encouraging the industry and regulators to consider accepting the mixed matrix method for assessing metabolite exposure comparisons between humans and animal species used in toxicology studies.

An Assessment of the In Vitro Inhibition of Cytochrome P450 Enzymes, UDP-Glucuronosyltransferases, and Transporters by Phosphodiester- or Phosphorothioate-Linked Oligonucleotides.

Chapter 14 - Metabolites in safety testing (MIST)

BioanalysisVol. 3, No. 24 CommentaryThe use of accelerator MS in support of MISTAngus NeddermanAngus NeddermanDepartment of Pharmacokinetics, Dynamics & Metabolism, Pfizer Worldwide Research & Development, Ramsgate Road, Sandwich, Kent, CT13 9NJ, UK; Unilabs York Bioanalytical Solutions, Discovery Park, Ramsgate Road, Sandwich, CT13 9NJ, UK. Search for more papers by this authorEmail the corresponding author at angus.nedderman@yorkbio.comPublished Online:20 Dec 2011https://doi.org/10.4155/bio.11.269AboutSectionsView ArticleView Full TextPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareShare onFacebookTwitterLinkedInRedditEmail View articleKeywords: accelerator MSmetabolitesmetabolites in safety testingMISTsafetyReferences1 Baillie TA, Cayen MN, Fouda H et al. Drug metabolites in safety testing. Toxicol. App. Pharmacol.182,188–196 (2002).Crossref, Medline, CAS, Google Scholar2 Smith DA, Obach RS. 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Accelerator mass spectrometry (AMS): recent experience of its use in a clinical study and the potential future of the technique. Xenobiotica31,619–632 (2001).Crossref, Medline, CAS, Google Scholar12 Garner RC, Goris I, Laenen AAE et al. Evaluation of accelerator mass spectrometry in a human mass balance and pharmacokinetic study – experience with 14C-labelled (R)-6-[Amino(4-chlorophenyl)(1-methyl-1H-imidazol-5-yl)methyl]-4-(3-chlorophenyl)-1-methyl-2(1H)-quinolinone (R115777), a farnesyl transferase inhibitor. Drug Metab. Disp.30,823–830 (2002).Crossref, Medline, CAS, Google Scholar13 Comezoglu SN, Ly VT, Zhang D et al. Biotransformation profiling of [14C]ixabepilone in human plasma, urine and feces samples using accelerator mass spectrometry (AMS). Drug Metab. Pharmacokinet.24,511–522 (2009).Crossref, Medline, CAS, Google Scholar14 Prakash C, Shaffer CL, Nedderman A. Analytical strategies for identifying drug metabolites. Mass Spectrom. Rev.26,340–369 (2007).Crossref, Medline, CAS, Google Scholar15 Lappin G, Seymour M, Young G, Higton D, Hill HM. An AMS method to determine analyte recovery from pharmacokinetic studies with concomitant extravascular and intravenous administration. Bioanalysis3(4),407–410 (2011).Link, CAS, Google Scholar16 Young GC, Ellis WJ. AMS in drug development at GSK. Nuc. Inst. Methods Phys. Res. B259,752–757 (2007).Crossref, CAS, Google Scholar17 Lappin G, Seymour M. Addressing metabolite safety during first-in-man studies using 14C-labeled drug and accelerator mass spectrometry. Bioanalysis2(7),1315–1324 (2010).Link, CAS, Google Scholar101 US FDA guidance for industry. Safety testing of drug metabolites (2008). www.fda.gov/downloads/Drugs/GuidanceComplianceRegulatoryInformation/Guidances/ucm079266.pdfGoogle Scholar102 ICH topic M3 (R2) (2009): non-clinical safety studies for the conduct of human clinical trials and marketing authorization for pharmaceuticals. www.ema.europa.eu/docs/en_GB/document_library/Scientific_guideline/2009/09/WC500002720.pdfGoogle ScholarFiguresReferencesRelatedDetailsCited By“MIST” AND OTHER METABOLITE GUIDELINES IN THE CONTEXT OF INDUSTRIAL DRUG METABOLISM11 July 2016METABOLITE TECHNOLOGY11 July 2016Application of a tiered approach to the validation of accelerator MS assaysDavid Higton & Mark Seymour12 March 2014 | Bioanalysis, Vol. 6, No. 5The early estimation of circulating drug metabolites in humans10 June 2012 | Expert Opinion on Drug Metabolism & Toxicology, Vol. 8, No. 8Conference Report: The 19th International Reid Bioanalytical ForumHoward Hill20 December 2011 | Bioanalysis, Vol. 3, No. 24 Vol. 3, No. 24 Follow us on social media for the latest updates Metrics Downloaded 223 times History Published online 20 December 2011 Published in print December 2011 Information© Future Science LtdKeywordsaccelerator MSmetabolitesmetabolites in safety testingMISTsafetyFinancial & competing interests disclosureThe author has no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.No writing assistance was utilized in the production of this manuscript.PDF download

HPLC detector technology has advanced dramatically over the past 20 years, with a range of highly sensitive and specific detectors becoming available. What is still missing from the bioanalyst's armoury, however, is a highly sensitive detector that gives an equimolar response independent of the compound. This would allow for quantification of compounds without the requirement for a synthetic standard or a radiolabeled analogue. In particular, such a detector applied to metabolism studies would establish the relative significance of the various metabolic routes. The recently issued US FDA guidelines on metabolites in safety testing (MIST) focus on the relative quantitation of human metabolites being obtained as soon as feasible in the drug-development process. In this article, current detector technology is reviewed with respect to its potential for quantitation without authentic standards or a radiolabel and put in the context of the MIST guidelines. The potential for future developments are explored.

Withdrawals from the market due to unforeseen adverse events have triggered changes in the way therapeutics are discovered and developed. This has resulted in an emphasis on truly understanding the efficacy and toxicity profile of new chemical entities (NCE) and the contributions of their metabolites to on-target pharmacology and off-target receptor-mediated toxicology. Members of the pharmaceutical industry, scientific community and regulatory agencies have held dialogues with respect to metabolites in safety testing (MIST); and both the US FDA and International Conference on Harmonisation have issued guidances with respect to when and how to characterize metabolites for human safety testing. This review provides a brief overview of NMR spectroscopy as applied to the structure elucidation and quantification of drug metabolites within the drug discovery and development process. It covers advances in this technique, including cryogenic cooling of detection circuitry for enhanced sensitivity, hyphenated LC-NMR techniques, improved dynamic range through new solvent-suppression pulse sequences and quantitation. These applications add to the already diverse NMR toolkit and further anchor NMR as a technique that is directly applicable to meeting the requirements of MIST guidelines.

In previous papers, we have offered a strategic framework regarding metabolites of drugs in humans and the need to assess these in laboratory animal species (also termed Metabolites in Safety Testing or MIST; Smith and Obach, Chem. Res. Toxicol. (2006) 19, 1570-1579). Three main tenets of this framework were founded in (i) comparisons of absolute exposures (as circulating concentrations or total body burden), (ii) the nature of the toxicity mechanism (i.e., reversible interaction at specific targets versus covalent binding to multiple macromolecules), and (iii) the biological matrix in which the metabolite was observed (circulatory vs excretory). In the present review, this framework is expanded to include a fourth tenet: considerations for the duration of exposure. Basic concepts of pharmacology are utilized to rationalize the relationship between exposure (to parent drug or metabolite) and various effects ranging from desired therapeutic effects through to severe toxicities. Practical considerations of human ADME (absorption-distribution-metabolism-excretion) data, to determine which metabolites should be further evaluated for safety, are discussed. An analysis of recently published human ADME studies shows that the number of drug metabolites considered to be important for MIST can be excessively high if a simple percentage-of-parent-drug criterion is used without consideration of the aforementioned four tenets. Concern over unique human metabolites has diminished over the years as experience has shown that metabolites of drugs in humans will almost always be observed in laboratory animals, although the proportions may vary. Even if a metabolite represents a high proportion of the dose in humans and a low proportion in animals, absolute abundances in animals frequently exceed that in humans because the doses used in animal toxicology studies are much greater than therapeutic doses in humans. The review also updates the enzymatic basis for the differences between species and how these relate to MIST considerations.

Importance of the field: The FDA and the International Conference on Harmonization (ICH) recently issued regulatory guidance on metabolites in safety testing (MIST). One of the key differences between these two types of guidance is the threshold for a major metabolite: > 10% of AUC of the parent drug at steady-state (the FDA) versus > 10% of drug-related exposure (ICH). The FDA agreed to adopt the ICH M3 threshold in 2010. Both guidance require metabolite profiling in humans during early clinical development which have presented significant challenges from two aspects: i) how to balance the recommendation of front-loading of metabolism studies with the need to invest resources appropriately according to the stage of drug development and ii) how to fully utilize alternative bioanalytical approaches to generate reliable data for enabling prompt and informed decisions, without always resorting to resource-intensive good laboratory practices bioanalysis.Areas covered in this review: This review summarizes current thinking in the pharmaceutical industry on these two aspects.What the reader will gain: This review aims to provide the reader with a clear understanding of the importance and timing of various metabolism studies and an overview of the latest bioanalytical approaches of quantitation of metabolites in the absence of reference standards.Take home message: The approaches outlined are not intended to be universal solutions to MIST. The researcher still has to consider a case-by-case approach with scientific justification to comply with the MIST guidance.

The Forum, initiated over 30 years ago by Eric Reid of the University of Surrey, after whom the Forum is now named, is held in Guildford at the University of Surrey every 2 years. This year's forum was the 18th in the series. There were over 30 oral presentations and more than 20 posters, together with suppliers' exhibitions on Tuesday and Wednesday. At its inception, the title of Forum, maintained over the years, was chosen to emphasize the interactive nature of the meeting; somewhere that practical issues could be discussed and successes and failures, 'tricks' of the trade, surprises and problems where logic (initially) fails are shared. The on-campus format and evening social events provide plenty of opportunity to discuss unresolved problems in a 'convivial' atmosphere. There were three major themes to this year's Forum: interpreting and implementing 'metabolites in safety testing'; quantification of biologicals (proteins and peptides, whether they be drugs, antidrug antibodies or biomarkers) in biological matrices using LC-MS/MS; and the use of dried blood spots. Interspersed among these were the core topics of the Forum, case histories illustrating the problem-solving skills of the bioanalyst and their ability to cope with surprises.

Active drug metabolites in drug development.

The Use of Transporter Probe Drug Cocktails for the Assessment of Transporter-Based Drug–Drug Interactions in a Clinical Setting—Proposal of a Four Component Transporter Cocktail

Drug discovery and development is the process of generating compounds and evaluating all their properties to determine the feasibility of selecting one new chemical entity to become a safe and efficacious drug. Metabolism by the host organism is one of the most important determinants of the pharmacokinetic profile of a drug. After administration, a drug is usually converted in the liver by various enzymes to a variety of metabolites. Formation of active or toxic metabolites will have an impact on the pharmacological and toxicological outcomes. There is also potential for drug-drug interactions with co-administered drugs due to inhibition or induction of drug metabolism pathways. Hence, optimisation of the metabolic liability and drug-drug interaction potential of the new chemical entities are some of the most important steps during the drug discovery process. Improved technology has allowed better identification and quantification of metabolites, raising new issues to be addressed during the course of drug development. Recently, a lot of effort has been applied to develop predictive methods to aid the optimisation process during drug discovery and development. This article reviews the role of drug metabolism in drug discovery and development.