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

Schadt, Heiko S.; Bister, Bojan; Chowdhury, Swapan K.; Funk, Christoph; Hop, Cornelis E. C. A.; Humphreys, W. Griffith; Igarashi, Fumihiko; James, Alexander David; Kagan, Mark; Khojasteh, S. Cyrus; Nedderman, Angus N. R.; Prakash, Chandra; Runge, Frank; Scheible, Holger; Spracklin, Douglas K.; Swart, Piet; Tse, Susanna; Yuan, Josh; Obach, R. Scott

doi:10.1124/dmd.117.079848

Cited by 93 publications

(66 citation statements)

References 66 publications

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“…Despite the recommendations in the guidance 3 and the extensive literature reviews, [7][8][9][10]12,13,15 shortcomings in the understanding of circulating metabolites are still apparent in recent regulatory submissions and have been identified in a number of applications for new marketing authorizations during the past 10 years. The reasons for this are varied but can often be attributed to deficiencies in the knowledge normally gained from the mass balance study and range from the complete absence of a human mass balance study to poorly designed, or incomplete studies, or to unexpected findings in the study confounding the interpretation of the results, e.g., if the radiolabel is found to be in a metabolically labile position.…”

Section: Issues With Plasma Metabolite Identification In Dossiers Formentioning

confidence: 99%

“…It is now nearly 10 years since the ICH M3 (R2) guideline 2 came into force at the end of 2009, and reviews of the decade of use have already been discussed in at least two articles. 12,13 According to the European Medicines Agency (EMA) guideline, 3 the results of a mass balance study should generally be available before starting phase III clinical trials. In general, during the past 10 years, there has been a shift to conduct the human mass balance study earlier in clinical development, 11 i.e., before the demonstration of efficacy.…”

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confidence: 99%

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The Importance of the Human Mass Balance Study in Regulatory Submissions

Coppola¹,

Andersson

Cole³

2019

CPT Pharmacom & Syst Pharma

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The human mass balance study is a key study in the Clinical Pharmacology package of new drug applications. This study, along with the mass balance studies in toxicology species, provides essential information on the exposure of the parent compound and metabolites. Despite current regulatory guidance and previous publications, a lack of this study, or deficiencies in the study, are still seen in regulatory submissions today. This restricts the assessment of the benefit/risk in all populations and on the potential for drug–drug interactions leading to unnecessary precautions in the label. A review of new drug applications identifies a number of examples of inadequate characterization of circulating drug‐related components or of elimination pathways, with questions raised during the regulatory review. In light of this, new insight is given on what is required from the mass balance study and on how to ensure sufficient information is captured.

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Section: Issues With Plasma Metabolite Identification In Dossiers Formentioning

confidence: 99%

mentioning

confidence: 99%

The Importance of the Human Mass Balance Study in Regulatory Submissions

Coppola¹,

Andersson

Cole³

2019

CPT Pharmacom & Syst Pharma

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“…12,13 Lastly, the demethylation of caffeine by CYP1A2 increases with age, as in newborns caffeine is almost completely excreted by renal clearance of the parent drug, while in adults caffeine is many metabolically cleared. 14,15 As in general the metabolites differ in terms of efficacy and toxicity, 16 knowledge on metabolite profiles in children is crucial for applying effective and safe pediatric drug therapy.…”

Section: How Might This Change Clinical Pharma-cology or Translationamentioning

confidence: 99%

“…Metabolite profiles are typically generated by human radiolabeled ADME studies, by analyzing plasma, urine, or feces samples with liquid chromatography with fraction collectors, followed by offline radioactivity detection using liquid scintillation counting. 16 For this latter technique, a high radioactive dose of 100 microcurie (µCi) in humans is needed. Just recently, advances mainly in analytical technology have enabled new approaches to ADME studies with less radioactivity exposure.…”

Section: How Might This Change Clinical Pharma-cology or Translationamentioning

confidence: 99%

Proof of Concept: First Pediatric [¹⁴C]microtracer Study to Create Metabolite Profiles of Midazolam

Groen

Duijn²,

Vries³

et al. 2020

Clin Pharma and Therapeutics

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Growth and development affect drug‐metabolizing enzyme activity thus could alter the metabolic profile of a drug. Traditional studies to create metabolite profiles and study the routes of excretion are unethical in children due to the high radioactive burden. To overcome this challenge, we aimed to show the feasibility of an absorption, distribution, metabolism, and excretion (ADME) study using a [14C]midazolam microtracer as proof of concept in children. Twelve stable, critically ill children received an oral [14C]midazolam microtracer (20 ng/kg; 60 Bq/kg) while receiving intravenous therapeutic midazolam. Blood was sampled up to 24 hours after dosing. A time‐averaged plasma pool per patient was prepared reflecting the mean area under the curve plasma level, and subsequently one pool for each age group (0–1 month, 1–6 months, 0.5–2 years, and 2–6 years). For each pool [14C]levels were quantified by accelerator mass spectrometry, and metabolites identified by high resolution mass spectrometry. Urine and feces (n = 4) were collected up to 72 hours. The approach resulted in sufficient sensitivity to quantify individual metabolites in chromatograms. [14C]1‐OH‐midazolam‐glucuronide was most abundant in all but one age group, followed by unchanged [14C]midazolam and [14C]1‐OH‐midazolam. The small proportion of unspecified metabolites most probably includes [14C]midazolam‐glucuronide and [14C]4‐OH‐midazolam. Excretion was mainly in urine; the total recovery in urine and feces was 77–94%. This first pediatric pilot study makes clear that using a [14C]midazolam microtracer is feasible and safe to generate metabolite profiles and study recovery in children. This approach is promising for first‐in‐child studies to delineate age‐related variation in drug metabolite profiles.

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“…From a research perspective, these case examples provide interesting opportunities to probe the diversity of P450 function. From a drug discovery and development perspective, an unexpected metabolite adds to uncertainties and associated risks of a candidate molecule upon its first administration to human subjects (Schadt et al, 2018). Therefore, understanding reaction mechanisms, structural requirements, and specific isoform(s) responsible for these reactions is critical to anticipate and mitigate metabolic liabilities.…”

Section: Dmd # 90019mentioning

confidence: 99%

Novel Homodimer Metabolites of GDC-0994 via Cytochrome P450–Catalyzed Radical Coupling

Takahashi¹,

Grandner²,

Bobba³

et al. 2020

Drug Metab Dispos

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Two novel homodimer metabolites were identified in rat samples collected during the in vivo study of GDC-0994. In this study, we investigated the mechanism of the formation of these metabolites. We generated and isolated the dimer metabolites using a biomimetic oxidation system for NMR structure elucidation to identify a symmetric dimer formed via carbon-carbon bond between two pyrazoles, and an asymmetric dimer formed via an aminopyrazole-nitrogen to pyrazole-carbon bond. In vitro experiments demonstrated formation of these dimers was catalyzed by cytochrome P450 enzymes with CYP3A4/5 being the most efficient. Using Density Functional Theory (DFT), we determined these metabolites share a mechanism of formation, initiated by an N-H hydrogen atom abstraction by the catalytically active iron-oxo of CYPs. Molecular modeling studies also show these dimer metabolites fit in the CYP3A4 binding site in low energy conformations with minimal protein rearrangement. Collectively, the results of these experiments suggest that formation of these two homodimer metabolites is mediated by CYP3A, likely involving activation of two GDC-0994 molecules by a single P450 enzyme and proceeding through a radical coupling mechanism.

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

Cited by 93 publications

References 66 publications

The Importance of the Human Mass Balance Study in Regulatory Submissions

The Importance of the Human Mass Balance Study in Regulatory Submissions

Proof of Concept: First Pediatric [¹⁴C]microtracer Study to Create Metabolite Profiles of Midazolam

Novel Homodimer Metabolites of GDC-0994 via Cytochrome P450–Catalyzed Radical Coupling

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

Cited by 93 publications

References 66 publications

The Importance of the Human Mass Balance Study in Regulatory Submissions

The Importance of the Human Mass Balance Study in Regulatory Submissions

Proof of Concept: First Pediatric [14C]microtracer Study to Create Metabolite Profiles of Midazolam

Novel Homodimer Metabolites of GDC-0994 via Cytochrome P450–Catalyzed Radical Coupling

Contact Info

Product

Resources

About

Proof of Concept: First Pediatric [¹⁴C]microtracer Study to Create Metabolite Profiles of Midazolam