Institute for Scientific Exchange, Inc. Presents:

DDI – 2008

11^th International Conference on Drug-Drug Interactions:

Scientific and Regulatory Updates and DDI Technologies in Depth: Enzyme Inhibition, Enzyme Induction and Drug-Transporter Interactions

June 2-4, 2008

Pre-Conference Workshop: Current Practice: Time-dependent inhibition (TDI) of drug metabolism in drug development

June 2, 2008

Seattle, WA, USA

Featuring experts from the following institutions: Actelion; Amgen Inc.; APSciences/IVAL; Array Biopharma; AstraZeneca; CellzDirect, Inc.; Johnson & Johnson Biotechnology, Immunology & Oncology; Lilly Research Labs; Millennium Pharmaceuticals, Inc.; University of Washington; XenoTech, LLC.

ISE, Inc.

8775 Centre Park Drive

#713

Columbia MD 21045

(410) 869-9166

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PARTICIPATING EXHIBITORS:

Scientific Concepts of Time-dependent P450 Inactivation (Magang Shou, Amgen Inc.; Thousand Oaks, CA) Drug-drug interactions (DDIs) represent a serious concern in the discovery and development of new drugs. Mechanism-based CYP inhibition (MBI) is a common cause of the DDIs via a significant change in the exposure of one drug (victim) caused by a second drug (perpetractor). In this presentation the concepts and experimental approaches of MBI, screening of new chemical entities (NCEs) and prediction of the human DDIs from in vitro MBI data at pharmaceutical settings will be reviewed.

Recombinant CYP and liver microsomal time-dependent inhibition assays (Chuang Lu, Millennium Pharmaceuticals, Inc.; Cambridge, MA) Basic concepts and experimental procedures will be discussed for the evaluation of time-dependent inhibition potential of drug candidates. It is important to choose different methods for different compounds, such as for strong or weak TDI, TDI which also show reversible inhibition, etc. Mechanistic studies using recombinant CYPs will also be presented.

Time Dependent Inhibition Studies Using Human Hepatocytes (Dermot McGinnity, AstraZeneca; Loughborough, Leics, England) Primary human hepatocytes in culture are commonly used to evaluate CYP induction via an enzyme activity endpoint. However, time-dependent P450 inhibition (TDI) can confound data interpretation in this system. In our laboratory, TDI has been characterised using cultured human hepatocytes and the data compared to results generated in recombinant P450s and human liver microsomes. Together with a P450‑selective substrate cassette approach, cultured human hepatocytes provide a sensitive system for studying TDI. In this lecture, the use of hepatocytes for studying TDI as well as the implications for P450 induction studies will be discussed.

Cytotoxicity of Time-dependent Inhibitors in Human Hepatocytes (Albert P. Li, APSciences, Inc. and IVAL, LLC.; Columbia, MD) Human hepatocytes represent an experimental system with which P450 inhibition can be studied. The presence of an intact plasma membrane and complete, uninterrupted enzyme pathways and cofactors allow the generation of data more relevant to humans in vivo than data using cell fractions such as liver microsomes. As the hepatocytes are living cells, it is necessary to study P450 inhibition under conditions which would not lead to cytotoxicity, as a decrease in cell viability will lead to a decrease in P450 activities. The routine assay procedures for cell viability determination and the cytotoxicity of known time-dependent P450 inhibitors under various experimental conditions (e.g. incubation time; solvents) will be presented.

NMEs Approved in 2007-2008 (Carol Collins, University of Washington; Seattle, WA) This presentation will discuss information found in the NDA and product labeling pertinent to drug interactions for drugs approved in 2007-2008. Emphasis will be placed on FDA comments extracted from the NDAs that address issues not covered in the draft guidance, Drug Interaction Studies-Study Design, Data Analysis, and Implications for Dosing and Labeling (http://www.fda.gov/cder/guidance/6695dft.pdf). We will also evaluate prescribing information regarding drug interactions in the context of the therapeutic use of the product.

Literature review 2007-2008: Clinical Studies (Houda Hachad, University of Washington; Seattle, WA) This presentation will provide an update on the literature on drug interactions in 2007-2008. This large body of articles will be classified according to the following categories: metabolism versus transport-based interactions; new substrates, inhibitors and inducers; most represented therapeutic classes and disease entities; largest AUC effects; advances in methodology; noteworthy case reports; challenging and unexplained drug interactions.

Significance of Time-Dependent P450 Inhibition in Drug-drug Interactions and Drug Toxicity (Larry Wienkers, Amgen Inc.; Seattle, WA) The inhibition of cytochrome P450 can be reversible or irreversible. Mechanism-based inhibition (MBI) is an irreversible inhibition where a covalent bond is formed between a reactive metabolite and the active site of the enzyme, resulting in drug–drug interactions or if the reactive intermediate is released toxicity. In this instance, metabolic activation of a relatively inert functional group to reactive electrophilic intermediates is required for MBI. As a consequence, a thorough examination of the biochemical reactivity of functional groups in a drug candidate is essential from a development perspective. In the current presentation, experimental strategies in the detection and characterization of reactive intermediates in P450 MBIs will be discussed.

Time-dependent and Non-time Dependent P450 Inhibition Assays with Intact Human Hepatocytes (Dermot McGinnity, AstraZeneca; Loughborough, Leics, England) Human hepatocytes have been used for the study of both reversible and time-dependent inhibition of CYPs but it is notable that investigations of inhibitory mechanisms remain under represented compared to studies on metabolism and induction. This is likely due to the relative accessibility of rCYPs and their overall applicability in predicting clinically relevant DDI. As primary hepatocytes provide the closest in vitro model to human liver they may offer advantages when predicting clinical DDI. There is, however, little published comparative data of inhibition constants generated in rCYPs and human hepatocytes and the use of such data for predicting DDI. Data generated in this laboratory demonstrates IC_50, _unboundvalues generated in human hepatocytes, using probe substrates specific to the CYP isoform, were similar to those determined using the respective recombinant CYP with some notable exceptions. Primary human hepatocytes in culture are commonly used to evaluate CYP induction via an enzyme activity endpoint. However, time-dependent P450 inhibition (TDI) can confound data interpretation in this system. In our laboratory, TDI has been characterised using cultured human hepatocytes and the data compared to results generated in recombinant P450s and human liver microsomes.

Difficulties Associated with the Interpretation of CYP34A Time-Dependent Inhibition Data (Michael Schrag, Array Biopharma; Boulder, CO) It is standard industry practice that compounds in discovery and development are screened for the potential to cause drug-drug interactions via time dependent inhibition (TDI). Since CYP3A4 plays a prominent role in drug oxidation, TDI of this enzyme is often assessed early in the discovery process. One assay that is frequently used to screen for TDI is the dilution assay. This talk will focus on the difficulties of interpreting CYP3A4 TDI data in early screens.

Prediction of CYP3A4 Induction Mediated Drug-Drug Interactions from In Vitro Data (Magang Shou, Amgen Inc.; Thousand Oaks, CA) CYP induction is not generally a concern for safety and however can yield serous therapeutic failures, particularly those with a narrow therapeutic index. To date, little has been known for prediction of CYP3A4 induction mediated DDIs from in vitro approaches (e.g. primary hepatocytes). In this presentation, the predictive models, prediction and in vitro in vivo correlation of in vivo CYP3A4 induction from in vitro data will be described and the factors that possibly limit the prediction will be discussed.

Consideration of Intrahepatic Free and Bound Drug Concentrations in IVIVC (Chuang Lu, Millennium Pharmaceuticals, Inc.; Cambridge, MA) The use of either free or total drug concentrations in in vitro – in vivo correlation (IVIVC) dependents solely on the compound and study conditions. The concept of free intrahepatic concentration will be discussed. Examples of application of either free or total concentration to predict clinical drug-drug interactions will be presented.

Simultaneous Assessment of Induction and Time-dependent Inhibition in Cultures of Primary Human Hepatocytes (Stephen S. Ferguson, Christopher B. Black, Edward L. LeCluyse¹ CellzDirect, Inc., Durham, NC) Primary human hepatocytes are recognized as the “gold standard” model system for the assessment of cytochrome P450 induction potential in humans. This is due primarily to their characteristic under appropriate culture conditions of retaining the appropriate molecular signaling pathways involved in the control of CYP450 expression levels in human liver. These cultures represent a dynamic, responsive cellular system that has been shown to effectively model drug metabolism, induction, and inhibition in vitro. We have utilized this model system to simultaneously assess mRNA expression, protein content, and enzymatic activity with several classes of xenobiotics known to cause pharmacodynamic interactions in humans (e.g. inducers, inhibitors, time-dependent inhibitors, dual inhibitor/inducers). By using time as a tool to distinguish the relative contributions of inhibition and induction to CYP450 expression and enzymatic activity, we have characterized these various classes of effectors, and this has revealed interesting dynamics in their effects on CYP450 expression and metabolic activity. We further demonstrate that compounds known to induce and inhibit CYP450s may have differential effects on individual isozymes, therefore, classification of induction pathways and modes of inhibition is important for effective prediction of induction and/or inhibition potential. These findings have implications on our understanding of the dynamic and simultaneous processes of inhibition and induction in the liver, and outline a useful in vitro approach to more effectively characterize compounds that are found to be dual inducers and inhibitors of CYP450 activity.

Kinetic Evaluation of Compounds as Substrates or Inhibitors for Transporters with Cell-based Assays and its Application (Steven Louie, PKDM, Amgen; Thousand Oaks, CA) In 2006 the FDA issued a draft guideline in utilizing possible cell-based models for evaluating compounds as substrates or inhibitors of the P-glycoprotein (P-gp) transporter to assess risk of drug-drug interactions (DDIs) in humans. Cell lines include Caco-2 and MDR1-overexpressing LLC-PK1 or MDCK. However, no specific experimental details were described to accurately measure the kinetic parameters (Km, Vmax, IC50, and Ki), which makes prediction of in vivo DDI magnitude difficult. This presentation will discuss approaches to generating these kinetic parameters with cell-base transwell assays and how these data apply to early stage drug discovery screening.

Mechanistic Evaluation of Phase II Metabolite Excretion Pathways: Kinetic Consequences of Active Transport Inhibition on Exposure. (Maciej J. Zamek-Gliszczynski, Lilly Research Labs; Indianapolis, IN) Hydrophilic glucuronide and sulfate metabolites are excreted from both the site(s) of formation and the body via active transport. Bcrp and Mrp-2, -3, and -4 have been identified as transporters involved in this process using both gene-deficient animal models and in vitro systems. Ablation of a given transport pathway was shown to increase exposure to polar metabolites by a factor of 1/(1-f_e), where f_e is the fraction excreted via the intact pathway. This relationship is an important consideration for drug-drug interactions involving pharmacologically-active and toxic metabolites, as well as parent drugs cleared predominantly by active excretion.

University of Washington Metabolism and Transport Drug Interaction Database Team

Genetic Variation in Transport Proteins and Drug Response (Reinhold Kerb, AstraZeneca; Stuttgart, Germany and Dr. Margarete Fischer-Bosch-Institute for Clinical Pharmacology, Stuttgart and Clinical Pharmacology, University of Tübingen, Germany)The emerging role of hereditary polymorphisms in efflux and uptake transport proteins for drug efficacy, - safety and tolerability is highlighted suggesting these need to be considered in drug discovery and development to better understand variability in drug disposition and response and drug-drug interactions.

Non-P-gp Transporters in Drug-Drug Interactions and Toxicity: Advantages and Limitations of Current Experimental Approaches (Alexander Treiber, Actelion Pharmaceuticals Ltd, Basel, Switzerland) Over the last years, the awareness of the importance of transport processes in our understanding of drug disposition has grown beyond the long-established role of P-gp. Hepatocytes in various culture conditions and heterologously expressed drug transport proteins are among the most commonly used in vitro system for mechanistic studies on drug transport. The presentation will review the existing experimental toolbox in light of its utility for understanding and predicting transporter-mediated drug-drug interactions and toxicity.

Answering the Transporter Question Earlier (Greg Loewen, XenoTech; Lenexa, KS) Uptake and efflux transporters play a pivotal role in the absorption, distribution, metabolism and excretion (ADME) of drugs. Compounds that interact with transporters can cause drug-drug interactions by altering the clearance, efficacy and toxicity of co-administered drugs. New technologies are expanding the range and increasing the speed at which these drug-transporter interactions can be investigated. This presentation will review established technologies and new developments in assessing drug-transporter interactions.

Pharmacogenetics of Pgp in Patients with Leukemia: Implications for DDI and Opportunity for Individualized Therapy. (Rodney Ho, University of Washington; Seattle, WA)Hepatocytes and other epithelial cells expressing drug transport proteins are commonly used as in vitro systems for preclinical evaluating of potential drug-drug interactions (DDI) due to drug transports. The functional impact of pharmacogenetics of Pgp on DDI could be a challenge for CNS drugs. The results of clinical correlation studies are often not supported by in vitro functional studies of Pgp. We have developed a number of cell platforms to elucidate functional significance of Pgp sequence variations in leukemia patients. The results suggest that functional impact due to genetic variations is substrate dependent and could vary over 10 fold in cytotoxicity of cancer drugs. Given inhibitors of Pgp exhibit broad tissue toxicity and sequence variations lead to substrate dependent response, this presentation will highlight potential how integration of DDI knowledge could provide foundation for therapeutic optimization.

An Overview of Drug-Drug Interactions (DDI) for Therapeutic Proteins and Small Molecule Combinations (Sandhya Girish, Genentech, Inc.;
South San Francisco, CA) Therapeutic proteins such as monoclonal antibodies are increasingly being combined with small molecules and/or with other therapeutic proteins. However, little is known about the DDI risk for such combinations with respect to shared pathways of clearance (PK DDI potential) and/or shared mechanism of action (PD DDI potential). Moreover, based on our current knowledge of DDI with therapeutic proteins and clinical relevance of such interactions, is there a need to place an equal emphasis on assessment PK and PD DDI potential? This presentation will focus on quantitative pharmacological methods and strategies to discern DDI potential of therapeutic proteins during clinical development.

About the Institute for Scientific Exchange

The mission of The Institute for Scientific Exchange, Inc. is to advance science via communication – (i. e. symposia, training courses, publications). The events held by the Institute are highly selective, timely, and of the highest professional caliber. One major goal of the Institute, as exemplified by this symposium, is to foster communication among industrial, regulatory, and academic practitioners. Please visit our web site at www.isciencex.com.

Poster Presentations are always encouraged. Please submit your poster abstract for approval by the organizing board by May 15^th. Poster size should be no larger than 3 feet high by 7 feet long. Abstracts of posters will be included in the participant binder and in the ISE website. There is no formal poster presentation scheduled. All posters will remain displayed throughout the conference. Please be prepared to display your poster during registration on Monday, June 19^th or before the first session begins on Tuesday, June 20^th. Poster presenters will have ample time for discussion during breaks and the Panel discussions. Submit posters abstracts for approval to Nola Mahaney, VP, Operations; ISE, Inc.; 8775 Centre Park Drive, #713, MD 21045 or fax at (410) 869-9560 or email file attachment to nola@isciencex.com. Approved poster presenters are responsible for completing a conference attendance registration form and payment of fee (visit www.isciencex.com/register.htm) and for the shipping of the poster itself. Please contact Nola Mahaney for any questions or concerns. Please refer to “Travel Information” for hotel address and shipping information.

General Information: Conveniently located in downtown Seattle, The Red Lion Hotel on Fifth Avenue offers an upscale, boutique hotel experience, personal, award-winning service, first-class meeting space, and - perhaps most importantly - breathtaking views of the Cascade Mountains, Elliott Bay, the Puget Sound and the Emerald City itself. Whether you're planning a family trip, coming to town on business, or just looking to take a little time off from the hustle and bustle of your daily life, we guarantee you'll find The Red Lion Hotel on Fifth Avenue to be an excellent choice of accommodations. http://redlion.rdln.com/HotelLocator/HotelOverview.aspx?metaID=32

Payment

Payment may be made by check or credit card. Checks should be made in US $, payable to Institute for Scientific Exchange, Inc. Mail to: ISE, Inc., 8775 Center Park Drive; #713, Columbia, MD 21045, USA

Cancellation Policy

All cancellations are subjected to a $250.00 cancellation fee. Longer than 30 days, 100% refund (less cancellation fee). Less than 30 days, no refund but registration may be transferred to another person. All refund requests must be in writing. All refunds will be issued after the meeting has occurred. No refunds requests will be accepted after May 2, 2008. Please submit cancellation and refund requests including transferring of registration to:

Email to nola@isciencex.com with remittance to: ISE, Inc. 8775 Centre Park Drive; #713, Columbia, MD 21045, USA; FAX No: (410) 869-9560. Payment may be made by check in US$, payable to Institute for Scientific Exchange, Inc. or by credit card.