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  • Membrane Transporters in Drug

    Development

    Dr Raymond EversMerck & CoDrug Metabolism and PharmacokineticsP.O. Box 2000Rahway, NJ 08816Raymond_Evers@merck.com

  • 2

    Outline

    Part 1 Overview of the ITC Transporters covered by the ITC Decision trees

    Part 2 Case Studies

    OATP-mediated DDIs Digoxin-Rifampin DDI

  • 3

    Transporters and the FDA (Critical Path Initiative)

  • 4

    Goals of the International Transporter Consortium

    Provide an update on the current thinking on transporters

    For in vitro studies, provide a focus on studies that can have a translational clinical interpretation Limit raising red flags with in vitro studies that cannot be addressed

    in vivo in the clinic

    Explore gaps and suggest ways forward

    Provide a coordinated approach: academia, industry and regulatory

    Help to move the science forward Decision trees to assist drug development and regulatory agencies Consensus on current scientific status Gather support to move the ADME transport area forward

  • 5

    International Transporter Consortium

    WorkshopBethesda North Marriott

    October 2nd and 3rd, 2008

    Sponsored by FDA Critical Path

    Workshop organized by Drug Information Association (DIA)

    Co-sponsorship by AAPS, ISSX, PhRMA

    Provide a focus to initiate a White Paper for completion in 2009

  • 6

    White Paper: Nature Reviews Drug Discovery 2010

    Vol 9, p. 215-236

    Basic Introduction and Summary of Transporter Highlights what we know

    Methods for Studying Transporters Current solutions and future prospects

    Drug Development Issues Decision trees

    Membrane Transporters in Drug DevelopmentThe International Transporter Consortium, ITC

    Corresponding authors: K. Giacomini, S-M. Huang and D. Tweedie

  • 7

    White Paper What It Is and What It Is Not

    A consensus view on the current thinking What is known about the relative

    importance of transporters? Where should one put effort?

    The known unknowns What facts are known to be untrue

    (dispelling myths)? Where are our gaps in knowledge

    (where should we increase our knowledge)?

    A guideline (not a guidance/rules)towards what should be considered during development. Whitepaper biased toward NDA

    submission

    A complete literature review. A prescriptive guidance on what to

    do and how to do it, with a clear description of what it will mean.

    A consensus document that everyone agrees to.

    A description of all of the exceptions. Your experience is important and

    we would certainly appreciate you sharing that with the scientific community.

    Decision trees are not definitive. Included to help move the science

    forward by acting as templates for discussion

    Not must dos

    What it is.. and what it is not..

  • 8

    Transporters

    Two Families of Transporters (400+ members) 30 Contribute to the efficacy and safety of drugs

    ABC Transporters ATP-binding cassette Present in tissue barriers and excretory organs, can move

    compounds against a concentration gradient P-glycoprotein (P-gp, ABCB1) Breast cancer resistance protein (BCRP, ABCG2) Multidrug resistance proteins (MRP Family)

    SLC transporters Organic Solute Carrier Transporters Found throughout the body, play a role in cellular homeostasis

    and distribution of nutrients. OATs (OAT1 - SLC22A6), OAT3 - SLC22A8) OCT/OCTNs (OCT2 SLC22A2) OATPs (OATP1B1- SLCO1B1, OATP1B3-SLCO1B3)

    2

  • 9

    Expression of Transporters in Major Human Organs

    Nature Reviews Drug Discovery, 2010

  • 10

    Transporters Selected for Evaluation in Drug Development

  • 11

    Transporter Information in Drug Labeling

    P-gp Aliskiren, ambrisentan, [aprepitant], clarithromycin, colchicine, [dexvenafaxine], dronedarone, [eltrombopag], everolimus,fexofenadine, [fosaprepitant], [ixabepilone], lapatinib, maraviroc, nilotinib, paliperidone, posaconazole, [prasugrel], [[propafenone]], propranolol, ranolazine, saxagliptin, silodosin, sirolimus, sitagliptin, tipranavir**, tolvaptan, topotecan, [vorinostat]

    OATP1B1 Atorvastatin, cyclosporine, eltrombopag***, lapatinib, valsartan

    OATP Ambrisentan

    OAT Sitagliptin (OAT3)

    OCT Metformin, pramipexole, [saxagliptin], [sitagliptin], varenicline (OCT2)

    BCRP Lapatinib, topotecan

    MRP Mycophenolate (MRP2), [ixabepilone] (MRP1),valsartan (MRP2)

    *Not an extensive list: data based on a preliminary survey of electronic PDR and Drugs@FDA on September 18, 2009. They are substrates, inhibitors, both substrates and inhibitors, [not a substrate or an inhibitor], or [[not studies as a substrate or an inhibitor]]; **:Tipranavir is also a P-gp inducer *** an inhibitor; its labeling contains a list of OATP1B1 substrates

  • 12

    Use of Decision Trees

    Pros Evolution of concept Generate discussion points Offers flexibility

    Cons Rigid interpretation: prescriptive and overly cautious Insufficient knowledge to populate the decision points Lack of selective substrates and inhibitors Not fully vetted

    The evolution and appropriate application of the decision trees will require constant monitoring

  • 13

    Pgp/BCRP Substrate Decision Tree

    Needs calibration withPositive controls

    Many drugs that are efflux substrates are extensively absorbed Factors contributing to efflux limited absorption are:

    high Km, Vmax low solubility low permeability metabolic stability low dose.

    Not needed in the caseof transfected cells

    Not needed in the caseof transfected cells

  • 14

    Decision Tree for Pgp Inhibitor Interactions

    [I1] is steady-state total Cmax at the highest clinical dose [I2] is the GI concentration calculated at dose (mg)/250 mL

    Needs calibration byestablishing ivivc

  • 15

    OATP Substrate Decision Tree

    Transporterphenotypingneeded

    Integrate preclinical and clinical data

  • 16

    Relative Expression and Activity Factors

    OATP1B1OATP1B1,

    OATP1B1Hep,OATP1B1

    Exp

    ExpREF

    OATP1B3OATP1B3,

    OATP1B3Hep,OATP1B3

    Exp

    ExpREF

    CCK8OATP1B3,

    CCK8Hep,OATP1B3

    CL

    CLRAF

    OATP1B1 OATP1B3 OATP1B1 OATP1B3

    E-sulE-sul CCK-8 CCK-8

    Hepatocytes MDCKII-OATP1B1 cells MDCKII-OATP1B3 cells

    ESulOATP1B1,

    ESulHep,OATP1B1

    CL

    CLRAF

    Relative Expression Factor (REF) Relative Activity Factor (RAF)

    Shitara et al., 2006

  • 17

    REF for OATP1B1 and OATP1B3

    REFOATP1B1 = ExpHep,OATP1B1 / ExpOATP1B1, OATP1B1 = 16.9

    0

    0.5

    1

    1.5

    2

    2.5

    3

    3.5

    0 10 20 30 40protein amount (ug/lane)

    band

    den

    sity

    (rel

    ativ

    e va

    lue) MDCKII/OATP1B1

    Human Hepatocytes

    MDCK MDCK/OATP1B1 Human Hepatocytes30ug 10ug 20ug 30ug 10ug 20ug 30ug

    OATP1B1

    MDCK MDCK/OATP1B3 Human Hepatocytes30ug 10ug 20ug 30ug 10ug 20ug 30ug

    OATP1B3

    0

    0.2

    0.4

    0.6

    0.8

    1

    1.2

    1.4

    1.6

    0 10 20 30 40

    protein amount (ug/lane)

    band

    den

    sity

    (rel

    ativ

    e va

    lue) MDCKII/OATP1B3

    Human Hepatocytes

    REFOATP1B3 = ExpHep,OATP1B3 / ExpOATP1B3, OATP1B3 = 2.8

    OATP1B1 OATP1B3

  • 18

    CCK-8 uptake into human hepatocytes

    0

    10

    20

    30

    40

    50

    60

    70

    0 5 10 15 20 25 30[CCK-8] uM

    CC

    K-8

    initi

    al u

    ptak

    e ra

    te(p

    mol

    e/10

    ^6ce

    lls/m

    in)

    Total UptakePassive diffusionActive UptakeObserved data

    RAF for OATP1B1 and OATP1B3

    CCK-8 uptake into MDCKII-OATP1B3 cells

    0.05.0

    10.015.020.025.030.035.0

    0 5 10 15 20 25 30[CCK-8] uM

    OA

    TP

    1B3-

    med

    iate

    d C

    CK

    -8

    upta

    ke ra

    te (p

    mol

    e/10

    ^6 c

    ells

    /min

    )

    Vmax / Km= 3.9 (l /106 cells/min)

    E-sul uptake into human hepatocytes

    0

    200

    400

    600

    800

    1000

    0 5 10 15 20 25 30[E-sul] uM

    E-su

    l ini

    tial u

    ptak

    e ra

    te

    (pm

    ol/1

    0^6c

    ells

    /min

    )

    Total UptakePassive diffusionActive UptakeObserved data

    E-sul uptake into MDCKII-OATP1B1 cells

    0.0

    1.0

    2.0

    3.0

    4.0

    5.0

    6.0

    7.0

    0 2 4 6 8 10 12[E-sul] uM

    OA

    TP1B

    1-m

    edia

    ted

    E-s

    ul

    upta

    ke ra

    te (p

    mol

    e/10

    ^6 c

    ells

    /min

    )

    Vmax / Km= 18.3(l / 106 cells/min) Vmax / Km= 295.6

    (l /106 cells/min)

    Vmax / Km = 13.0 (l / 106cells/min)

    RAFOATP1B1 = CLHep,E-sul / CLOATP1B1, E-sul = 16.2

    RAFOATP1B3 = CLHep,CCK-8 / CLOATP1B3, CCK-8 = 3.4

  • 19

    Relative Contribution of OATPs to Pitavastatin

    Uptake Clearance

    OATP1B1 is the major transporter for the hepatic uptake of pitavastatin in human hepatocytes

    Data obtained by RAF and REF methods are comparable

    Transporter Km(uM)

    Vmax(pmole/min/10^6cells)

    CLint(ul/min/10^6cells)

    OATP1B1 4.51.2 18.81.3 4.2

    OATP1B3 6.53.2 9.31.7 1.4

    Transporter Clint(ul/min/10^6c

    ells)

    RAF Estimated CLint from

    RAF

    Relative contribution

    (%)

    REF Estimated CLint from

    REF

    Relative contribution

    (%)

    OATP1B1 4.2 16.2 67.5 93.4 16.9 70.8 94.7

    OATP1B

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