2017 FDA Guidance: Many In Vitro DDI Evaluations Should Precede FIH Studies

Published:  06 December 2018

Dr. Brian Ogilvie, Andrea Wolff
While the 2017 FDA DDI guidance contains many important changes, the earlier timing of drug-drug interaction studies is perhaps the most daunting. This is especially true for developers with drugs in the later clinical stages. Does this guidance mean sponsors are required to backtrack, and if so, how far? This article outlines the implications of these new timing requirements and best practices for negotiating them efficiently and effectively moving forward...

Chapter 6: Biotransformation of Xenobiotics

Published:  19 November 2018

Andrew Parkinson, Brian W. Ogilvie, David B. Buckley, Faraz Kazmi and Oliver Parkinson
This book chapter will be part of Casarett and Doull's Toxicology: The Basic Science of Poisons, 9th Edition, Edited by Curtis Klaassen. McGraw-Hill Medical Pub. Division, New York. ISBN-13: 978-1-259-86374-5.
Due to copyright law, we are unable to distribute an electronic version of this reprint. The "download publication" button below will redirect you to where you can request a printed copy be sent to you once available.

Strategies to improve the prediction accuracy of hepatic intrinsic clearance of three antidiabetic drugs: Application of the extended clearance concept and consideration of the effect of albumin on CYP2C metabolism and OATP1B-mediated hepatic uptake

Published:  01 October 2018

Ryo Fujino, Kenta Hashizume, Shinsuke Aoyama, Kazuya Maeda, Kiyomi Ito, Kota Toshimoto, Wooin Lee, Shin-ichi Ninomiya, Yuichi Sugiyama

The antidiabetic drugs glibenclamide, repaglinide, and nateglinide are well-known substrates for hepatic uptake transporters of the organic anion transporting polypeptide (OATP) family and metabolizing enzymes of the cytochrome P450 (CYP) 2C subfamily. The systemic exposure of these drugs varies substantially among individuals, impacted by genetic polymorphisms of transporters and metabolizing enzymes as well as drug-drug interactions. The use of the conventional in vitro-in vivo extrapolation (IVIVE) method was found to underestimate their hepatic intrinsic clearance (CLint,all); the clinically observed CLint,all values were ≥10-fold higher than the predicted values from in vitro data. In order to improve the accuracy in predicting CLint,all of these drugs, the following modifications were implemented; i) the extended clearance concept was applied during IVIVE processes, ii) albumin was added to metabolic assays using human liver microsomes (to minimize the impact of intrinsic inhibitors on kinetic parameters for CYP2C-mediated metabolism) and to hepatic uptake assays (to accommodate the enhanced hepatic uptake observed with albumin-bound drugs), and iii) differing rates of efflux and influx via diffusion were used. The IVIVE method with these modifications yielded the predicted CLint,all values from in vitro data in closer agreement with the CLint,all values observed in vivo; the fold differences between the predicted and observed CLint,all values reduced from 13–15 to 5.9–6.7. Our current approach offers an improvement in the prediction of CLint,all and further investigations are warranted to enhance the prediction accuracy of IVIVE.

To GLP, or Not To GLP?

Published:  01 October 2018

Scott Hickman, Dr. Brian Ogilvie, Tim Patterson
In vitro drug interaction studies do not necessarily need to be performed under GLP conditions. To learn more — and probably save time and considerable money — read this article...

Challenges & Solutions in Today’s In Vitro Transporter Research

Published:  30 August 2018

Dr. Joanna Barbara

In vitro drug transport assays are performed throughout drug development and range from simple permeability screens to kinetic assessments in complex assay formats. Sometimes interpreting transporter assay results is straightforward, and sometimes applying the data to make smart decisions is challenging. Furthermore, the current regulatory landscape has presented new considerations for interpreting transporter assay results...

Considerations from the IQ Induction Working Group in Response to Drug-Drug Interaction Guidances from Regulatory Agencies: Focus on CYP3A4 mRNA in vitro response thresholds, variability, and clinical relevance

Published:  29 June 2018

Jane R Kenny, Diane Ramsden, David B Buckley, Shannon Dallas, Conrad Fung, Michael Mohutsky, Heidi J Einolf, Liangfu Chen, Joshua G Dekeyser, Maria Fitzgerald, Theunis C Goosen, Y Amy Siu, Robert L Walsky, George Zhang, Donald Tweedie and Niresh Hariparsad
Drug Metabolism and Disposition June 29, 2018, dmd.118.081927; DOI: https://doi.org/10.1124/dmd.118.081927

The IQ induction working group presents an assessment of best practice for data interpretation of in vitro induction, specifically, response thresholds, variability, application of controls and translation to clinical risk assessment with focus on CYP3A4 mRNA. Single concentration control data and Emax/EC50 data for prototypical CYP3A4 inducers were compiled from many human hepatocyte donors in different laboratories. Clinical CYP3A induction and in vitro data were gathered for 51 compounds, 16 of which were proprietary. A large degree of variability was observed in both the clinical and in vitro induction responses, yet analysis confirmed in vitro data are able to predict clinical induction risk. Following extensive examination of this large dataset, the following recommendations are proposed. (a) CYP induction should continue to be evaluated in three separate human donors in vitro. (b) In light of empirically divergent responses in rifampicin control and most test inducers, normalization of data to percent positive control appears to be of limited benefit. (c) Two-fold induction, with concentration dependence, is an acceptable threshold for positive identification of in vitro CYP3A4 mRNA induction. (d) To reduce the risk of false positives, in the absence of a concentration dependent response, induction o ≥ 2-fold should be observed in more than one donor to classify a compound as an in vitro inducer. (e) If qualifying a compound as negative for CYP3A4 mRNA induction, the magnitude of maximal rifampicin response in that donor should be o ≥10-fold. (f) Inclusion of a negative control adds no value beyond that of the vehicle control...

An assessment of the in vitro inhibition of cytochrome P450 enzymes (CYP), UDP-glucuronsyltransferases (UGT) and transporters by phosphodiester- or phosphorothioate-linked oligonucleotides

Published:  07 May 2018

Faraz Kazmi, Phyllis Yerino, Chase McCoy, Andrew Parkinson, David B Buckley and Brian W Ogilvie

Oligonucleotides represent an expanding class of pharmacotherapeutics in development for various indications. Typically, oligonucleotides are developed with phosphorothioate linkages for the improvement of biological stability; however limited data are available on the potential of these molecules to cause drug-drug interactions (DDIs). In the present study, two non therapeutic oligonucleotides with either phosphodiester (PD-GP and PD-Ac) or phosphorothioate (PT-GP and PT-Ac) linkages were evaluated in vitro for their potential to inhibit P450s and UGTs in both human liver microsomes (HLM) and cryopreserved human hepatocytes (CHH) and to inhibit select transporters in expression systems. PD-GP and PD-Ac had little-to-no inhibitory effect on any P450 or UGT enzymes in HLM and CHH except for PD-Ac in HLM for CYP2C19 (IC50 = 29 μM). Conversely, PT-GP and PT-Ac caused direct inhibition of almost all P450 and UGT enzymes, with CYP1A2 (IC50 values 0.8-4.2 μM), CYP2C8 (IC50 values 1.1-12 μM) and UGT1A1 (IC50 values 4.5-5.4 μM) inhibited to the greatest extent. There was evidence of possible time-dependent inhibition (TDI) of CYP enzymes with PT-GP and PT-Ac for CYP2B6, CYP2C8, CYP2C19, CYP2C9, CYP2D6 and CYP3A4/5; however, this TDI was reversible. In contrast to HLM, there was little-to-no direct CYP inhibition by any oligonucleotide in CHH (except for PD-Ac with CYP2C19 [IC50 = 36 μM] and TDI by PT-GP with CYP2C8), demonstrating test system-dependent outcomes. Inhibition was observed for the organic anion uptake transporters OATP1B1, OATP1B3, OAT1, OAT3, and OCT2 (IC50 values 12-29 μM) but not OCT1 or the efflux transporters BCRP and P-gp by the phosphorothioate oligonucleotides.

Direct and cytokine‐mediated effects of albumin‐fused growth hormone, TV‐1106, on CYP enzyme expression in human hepatocytes in vitro

Published:  16 April 2018

Maciej Czerwiński, Immaculate Amunom, Victor Piryatinsky, Hussein Hallak, Yousif Sahly, Oren Bar‐Ilan, Paul Bolliger, Merav Bassan

Some biologics can modulate cytokines that may lead to changes in expression of drug‐metabolizing enzymes and cause drug‐drug interactions (DDI). DDI potential of TV‐1106—an albumin‐fused growth hormone (GH)—was investigated. In this study, human blood was exposed to recombinant human growth hormone (rhGH) or TV‐1106, followed by isolation of the plasma and its application to human hepatocytes. While the treatment of blood with rhGH increased multiple cytokines, treatment of blood with TV‐1106 had no effect on any of the nine cytokines tested. The interleukin (IL)‐6 concentration was higher in the rhGH then in the TV‐1106‐treated plasma (P< .05). While rhGH had little or no effect on CYP1A2 or CYP2C19 mRNA but increased CYP3A4 mRNA twofold, TV‐1106 had little or no effect on cytochrome P450 (CYP) mRNAs in hepatocytes. Although the plasma from rhGH‐treated blood lowered CYP1A2 activity, the TV‐1106 plasma had no effect on CYP activities. The CYP1A2 activity was lower in the rhGH‐ then in the TV‐1106‐plasma treated hepatocytes (P < .05). The results indicated that fusing GH with albumin made TV‐1106 an unlikely participant of CYP1A2, CYP2C19 or CYP3A4‐facilitated, direct or cytokine‐driven DDI.