Author
Keith Hoffmaster
Other affiliations: Pfizer, University of North Carolina at Chapel Hill
Bio: Keith Hoffmaster is an academic researcher from Novartis. The author has contributed to research in topics: Excretion & Drug development. The author has an hindex of 18, co-authored 27 publications receiving 4285 citations. Previous affiliations of Keith Hoffmaster include Pfizer & University of North Carolina at Chapel Hill.
Topics: Excretion, Drug development, Hepatocyte, Metabolite, Analyte
Papers
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University of California, San Francisco1, Food and Drug Administration2, University of North Carolina at Chapel Hill3, Merck & Co.4, Abbott Laboratories5, Eli Lilly and Company6, Novartis7, German Cancer Research Center8, University of Western Ontario9, Pfizer10, University of Helsinki11, GlaxoSmithKline12, University of Tokyo13, University of Maryland, Baltimore14, Genentech15, University of Arizona16
TL;DR: Overall, it is advised that the timing of transporter investigations should be driven by efficacy, safety and clinical trial enrolment questions, as well as a need for further understanding of the absorption, distribution, metabolism and excretion properties of the drug molecule, and information required for drug labelling.
Abstract: Membrane transporters can be major determinants of the pharmacokinetic, safety and efficacy profiles of drugs. This presents several key questions for drug development, including which transporters are clinically important in drug absorption and disposition, and which in vitro methods are suitable for studying drug interactions with these transporters. In addition, what criteria should trigger follow-up clinical studies, and which clinical studies should be conducted if needed. In this article, we provide the recommendations of the International Transporter Consortium on these issues, and present decision trees that are intended to help guide clinical studies on the currently recognized most important drug transporter interactions. The recommendations are generally intended to support clinical development and filing of a new drug application. Overall, it is advised that the timing of transporter investigations should be driven by efficacy, safety and clinical trial enrolment questions (for example, exclusion and inclusion criteria), as well as a need for further understanding of the absorption, distribution, metabolism and excretion properties of the drug molecule, and information required for drug labelling.
2,879 citations
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TL;DR: This review summarizes sulfation, glucuronidation, and glutathione conjugation reactions, as well as recent progress in elucidating the hepatic transport mechanisms responsible for the excretion of these conjugates from the liver, and focuses on alterations of metabolism and transport by chemical modulators, and disease states.
246 citations
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TL;DR: In vitro tools to address key questions in drug development, including vesicle‐ and cell‐based systems, are discussed and how these methods can be used to assess the liability of compounds for transporter‐based drug–drug interactions in vivo is explored.
Abstract: This white paper addresses current approaches and knowledge gaps concerning methods to assess the role of transport proteins in drug/metabolite disposition in humans. The discussion focuses on in vitro tools to address key questions in drug development, including vesicle- and cell-based systems. How these methods can be used to assess the liability of compounds for transporter-based drug-drug interactions (DDIs) in vivo is also explored. Existing challenges and approaches to examine the involvement of transporters in drug disposition are discussed.
228 citations
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TL;DR: An experimental model is described that captures complex liver physiology through incorporation of heterotypic cell–cell interactions, 3D architecture and perfused flow and is demonstrated how heterotypes can be manipulated to recreate an inflammatory environment and apply the model to test compounds that potentially exhibit idiosyncratic drug toxicity.
Abstract: Assessment of drug–liver interactions is an integral part of predicting the safety profile of new drugs. Existing model systems range from in vitro cell culture models to FDA-mandated animal tests....
150 citations
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TL;DR: Treatment with SHP099, the recently discovered small-molecule inhibitor of SHP2, in combination with the ALK tyrosine kinase inhibitor (TKI) ceritinib halted the growth of resistant PDCs through preventing compensatory RAS and ERk1 and ERK2 (ERK1/2) reactivation.
Abstract: Most anaplastic lymphoma kinase (ALK)-rearranged non-small-cell lung tumors initially respond to small-molecule ALK inhibitors, but drug resistance often develops. Of tumors that develop resistance to highly potent second-generation ALK inhibitors, approximately half harbor resistance mutations in ALK, while the other half have other mechanisms underlying resistance. Members of the latter group often have activation of at least one of several different tyrosine kinases driving resistance. Such tumors are not expected to respond to lorlatinib-a third-generation inhibitor targeting ALK that is able to overcome all clinically identified resistant mutations in ALK-and further therapeutic options are limited. Herein, we deployed a shRNA screen of 1,000 genes in multiple ALK-inhibitor-resistant patient-derived cells (PDCs) to discover those that confer sensitivity to ALK inhibition. This approach identified SHP2, a nonreceptor protein tyrosine phosphatase, as a common targetable resistance node in multiple PDCs. SHP2 provides a parallel survival input downstream of multiple tyrosine kinases that promote resistance to ALK inhibitors. Treatment with SHP099, the recently discovered small-molecule inhibitor of SHP2, in combination with the ALK tyrosine kinase inhibitor (TKI) ceritinib halted the growth of resistant PDCs through preventing compensatory RAS and ERK1 and ERK2 (ERK1/2) reactivation. These findings suggest that combined ALK and SHP2 inhibition may be a promising therapeutic strategy for resistant cancers driven by several different ALK-independent mechanisms underlying resistance.
150 citations
Cited by
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University of California, San Francisco1, Food and Drug Administration2, University of North Carolina at Chapel Hill3, Merck & Co.4, Abbott Laboratories5, Eli Lilly and Company6, Novartis7, German Cancer Research Center8, University of Western Ontario9, Pfizer10, University of Helsinki11, GlaxoSmithKline12, University of Tokyo13, University of Maryland, Baltimore14, Genentech15, University of Arizona16
TL;DR: Overall, it is advised that the timing of transporter investigations should be driven by efficacy, safety and clinical trial enrolment questions, as well as a need for further understanding of the absorption, distribution, metabolism and excretion properties of the drug molecule, and information required for drug labelling.
Abstract: Membrane transporters can be major determinants of the pharmacokinetic, safety and efficacy profiles of drugs. This presents several key questions for drug development, including which transporters are clinically important in drug absorption and disposition, and which in vitro methods are suitable for studying drug interactions with these transporters. In addition, what criteria should trigger follow-up clinical studies, and which clinical studies should be conducted if needed. In this article, we provide the recommendations of the International Transporter Consortium on these issues, and present decision trees that are intended to help guide clinical studies on the currently recognized most important drug transporter interactions. The recommendations are generally intended to support clinical development and filing of a new drug application. Overall, it is advised that the timing of transporter investigations should be driven by efficacy, safety and clinical trial enrolment questions (for example, exclusion and inclusion criteria), as well as a need for further understanding of the absorption, distribution, metabolism and excretion properties of the drug molecule, and information required for drug labelling.
2,879 citations
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TL;DR: This gut-on-a-chip recapitulates multiple dynamic physical and functional features of human intestine that are critical for its function within a controlled microfluidic environment that is amenable for transport, absorption, and toxicity studies, and hence it should have great value for drug testing as well as development of novel intestinal disease models.
Abstract: Development of an in vitro living cell-based model of the intestine that mimics the mechanical, structural, absorptive, transport and pathophysiological properties of the human gut along with its crucial microbial symbionts could accelerate pharmaceutical development, and potentially replace animal testing. Here, we describe a biomimetic ‘human gut-on-a-chip’ microdevice composed of two microfluidic channels separated by a porous flexible membrane coated with extracellular matrix (ECM) and lined by human intestinal epithelial (Caco-2) cells that mimics the complex structure and physiology of living intestine. The gut microenvironment is recreated by flowing fluid at a low rate (30 μL h−1) producing low shear stress (0.02 dyne cm−2) over the microchannels, and by exerting cyclic strain (10%; 0.15 Hz) that mimics physiological peristaltic motions. Under these conditions, a columnar epithelium develops that polarizes rapidly, spontaneously grows into folds that recapitulate the structure of intestinal villi, and forms a high integrity barrier to small molecules that better mimics whole intestine than cells in cultured in static Transwell models. In addition, a normal intestinal microbe (Lactobacillus rhamnosus GG) can be successfully co-cultured for extended periods (>1 week) on the luminal surface of the cultured epithelium without compromising epithelial cell viability, and this actually improves barrier function as previously observed in humans. Thus, this gut-on-a-chip recapitulates multiple dynamic physical and functional features of human intestine that are critical for its function within a controlled microfluidic environment that is amenable for transport, absorption, and toxicity studies, and hence it should have great value for drug testing as well as development of novel intestinal disease models.
1,247 citations
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University of Düsseldorf1, Goethe University Frankfurt2, Vrije Universiteit Brussel3, University of Freiburg4, Leipzig University5, Dow Chemical Company6, University of Tübingen7, Durham University8, University of Turin9, Seoul National University10, University of Jena11, Charité12, University of Valencia13, Heidelberg University14, University of Paris15, French Institute for Research in Computer Science and Automation16, University of Liverpool17, University of Groningen18, Lund University19, University of Manchester20, South Valley University21, University Hospital Regensburg22, Merck KGaA23, Musashino University24, University of Kansas25, Ludwig Maximilian University of Munich26, Fresenius Medical Care27, University of Regensburg28, Merck & Co.29
TL;DR: This review encompasses the most important advances in liver functions and hepatotoxicity and analyzes which mechanisms can be studied in vitro and how closely hepatoma, stem cell and iPS cell–derived hepatocyte-like-cells resemble real hepatocytes.
Abstract: This review encompasses the most important advances in liver functions and hepatotoxicity and analyzes which mechanisms can be studied in vitro. In a complex architecture of nested, zonated lobules, the liver consists of approximately 80 % hepatocytes and 20 % non-parenchymal cells, the latter being involved in a secondary phase that may dramatically aggravate the initial damage. Hepatotoxicity, as well as hepatic metabolism, is controlled by a set of nuclear receptors (including PXR, CAR, HNF-4α, FXR, LXR, SHP, VDR and PPAR) and signaling pathways. When isolating liver cells, some pathways are activated, e.g., the RAS/MEK/ERK pathway, whereas others are silenced (e.g. HNF-4α), resulting in up- and downregulation of hundreds of genes. An understanding of these changes is crucial for a correct interpretation of in vitro data. The possibilities and limitations of the most useful liver in vitro systems are summarized, including three-dimensional culture techniques, co-cultures with non-parenchymal cells, hepatospheres, precision cut liver slices and the isolated perfused liver. Also discussed is how closely hepatoma, stem cell and iPS cell-derived hepatocyte-like-cells resemble real hepatocytes. Finally, a summary is given of the state of the art of liver in vitro and mathematical modeling systems that are currently used in the pharmaceutical industry with an emphasis on drug metabolism, prediction of clearance, drug interaction, transporter studies and hepatotoxicity. One key message is that despite our enthusiasm for in vitro systems, we must never lose sight of the in vivo situation. Although hepatocytes have been isolated for decades, the hunt for relevant alternative systems has only just begun.
1,085 citations
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TL;DR: The most comprehensive exploration of genetic loci influencing human metabolism thus far, comprising 7,824 adult individuals from 2 European population studies, is reported, reporting genome-wide significant associations at 145 metabolic loci and their biochemical connectivity with more than 400 metabolites in human blood.
Abstract: Genome-wide association scans with high-throughput metabolic profiling provide unprecedented insights into how genetic variation influences metabolism and complex disease. Here we report the most comprehensive exploration of genetic loci influencing human metabolism thus far, comprising 7,824 adult individuals from 2 European population studies. We report genome-wide significant associations at 145 metabolic loci and their biochemical connectivity with more than 400 metabolites in human blood. We extensively characterize the resulting in vivo blueprint of metabolism in human blood by integrating it with information on gene expression, heritability and overlap with known loci for complex disorders, inborn errors of metabolism and pharmacological targets. We further developed a database and web-based resources for data mining and results visualization. Our findings provide new insights into the role of inherited variation in blood metabolic diversity and identify potential new opportunities for drug development and for understanding disease.
985 citations
01 Jan 1909
TL;DR: Application of Principles of Steady-State Kinetics to the Estimation of Brain Acetyicholine Turnover Rate: Effects of Oxotremorine and Physostigmine and the Relationship between Nitro Group Reduction and the Intestinal Microflora.
774 citations