DRUG-DRUG INTERACTIONS IN VIVO AND IN VITRO STUDIES: Focus on Transporters

1. DRUG-DRUG INTERACTIONS IN VIVO AND IN VITRO STUDIES: Focus on Transporters Background:Focus on P-gp Other Transporters Questions:

2. Multiple Membrane Transporters in Hepatocyte Work in Concert With Enzymes to Mediate Drug Elimination SLC DME Drug Metabolite ABC

3. Drug Interactions with P-gp Mizuno, 2003

4. Drug Interactions with P-gp Mizuno, 2003

5. Inhibitors of P-gp That Have Been Associated with a Known Clinical Drug-Drug Interaction* Valspodar Cyclosporin Erythromycin Itraconazole Verapamil Quinidine Ketoconazole Propafenone Clarithromycin Talinolol Ritonavir Nelfinavir Diltiazem Atorvastatin * Mechanism may be more complicated than simple P-gp inhibition

6. Substrates of P-gp That Have Altered Pharmacokinetic Properties in Humans in the Presence of P-gp Inhibitors* Digoxin Paclitaxel Dexamethasone Atorvastatin Talinolol Fexofenadine Saquinavir Cyclosporine Quinidine Docetaxal Etoposide Tacrolimus Azithromycin * Mechanism may be more complicated than simple P-gp inhibition

7. If an NME is an inhibitor of P-gp in vitro, there is a need to conduct a clinical study. Yes or No • What defines an inhibitor? • What clinical study?

8. If an NME is an inhibitor of P-gp in vitro, there is a need to conduct a clinical study. Yes or No • What defines an inhibitor? High Ratio of Therapeutic Unbound Concentration/Ki • Range of Ki values for drugs that have known clinical • drug-drug inhibition interactions with P-gp: • 0.18 to 280 µM. • Especially recommend that study be performed if • therapeutic drug concentrations (unbound) of • “P-gp inhibitor” is in the range of its in vitro Ki.

9. If an NME is an inhibitor of P-gp in vitro, there is a need to conduct a clinical study. Yes or No • What defines an inhibitor? • What clinical study?

10. If an NME is an inhibitor of P-gp in vitro, there is a need to conduct a clinical study. Yes or No What clinical study? • Study with digoxin • Other possibilities

11. Multiple Levels of Evidence that P-gp is Important in Digoxin Pharmacokinetics (Poorly metabolized) • Evidence in cell culture (digoxin is a substrate, Km 50 µM) • Evidence in mdr1 knockout mouse (i.e. quinidine increases • digoxin levels in normal mice, but not P-glycoprotein • knockout mice; digoxin levels in brain increase in mdr1 knockout • mice). • Clinical evidence of a quinidine-digoxin interaction • Clinical evidence that rifampin/St. John’s Wort reduce • digoxin levels (and increase P-gp expression in intestiine).

12. Multiple Levels of Evidence Suggesting That P-gp is Important in Digoxin Pharmacokinetics Digoxin Levels (ng/ml) Quinidine Dose

13. If an NME is an inhibitor of P-gp in vitro, there is a need to conduct a clinical study. Yes or No What clinical study? • Study with digoxin • Other possibilities Consider clinical use of drug

14. Substrates of P-gp That Have Altered Pharmacokinetic Properties in Humans in the Presence of P-gp Inhibitors* Digoxin Paclitaxel Dexamethasone Atorvastatin Talinolol Fexofenadine Saquinavir Cyclosporine Quinidine Docetaxal Etoposide Tacrolimus Azithromycin * Mechanism may be more complicated than simple P-gp inhibition

15. 3. If an NME is a substrate of P-gp and CYP3A4 in vitro, then a clinical study with a multi-inhibitor should be conducted. Yes or No Consider clinical use of drug Other: Demonstrate proof of concept

16. Inhibitors of P-gp That Have Been Associated with a Known Clinical Drug-Drug Interaction* Valspodar Cyclosporin Erythromycin Itraconazole Verapamil Quinidine Ketoconazole Propafenone Clarithromycin Talinolol Ritonavir Nelfinavir Diltiazem Atorvastatin * Mechanism may be more complicated than simple P-gp inhibition

17. 3. If an NME is a substrate of P-gp and not a substrate of CYP3A4 in vitro, then a clinical study with a P-gp inhibitor should be conducted. Yes or No

18. Inhibitors of P-gp That Have Been Associated with a Known Clinical Drug-Drug Interaction* Valspodar Cyclosporin Erythromycin Itraconazole Verapamil Quinidine Ketoconazole Propafenone Clarithromycin Talinolol Ritonavir Nelfinavir Diltiazem Atorvastatin * Mechanism may be more complicated than simple P-gp inhibition

19. Inducers of P-gp That Have Been Associated with a Known Clinical Drug-Drug Interaction* Rifampicin Induction Study

20. Other transporters… during drug development?

21. Other Transporters

22. Other Transporters: OAT1 and OAT3

23. Other Transporters: OCT1 and OCT2

24. Selected Clinical Examples of Cyclosporin-Statin Interactions with OATP1B1 (OATP-C) and CYPs Genetic evidence for OATP1B1 variants and pravastatin

25. Recommendation: If NME is substrate of OATP1B1, consider the following study: Cyclosporin effect on PK of NME If NME is inhibitor of OATP1B1, consider the following study: NME effect on PK of pravastatin

26. Selected Clinical Examples of Renal Drug-Drug Interactions at OATs R. Bendayan M. Dresser et al. Y. Shitara et al.

27. Selected Clinical Examples of Renal Drug-Drug Interactions at OCTs R. Bendayan M. Dresser et al. Y. Shitara et al.

28. Renal Organic Anion Transporters (OATs) If NME is secreted (i.e., Clrenal > fu*GFR), has a low therapeutic index, and substrate of OATs, consider a probenecid-NME interaction study. If NME is secreted (i.e., Clrenal > fu*GFR), has low therapeutic index, and substrate of OCTs, consider a trimethoprim-NME interaction study.

29. Some Selective Inhibitors of Renal Organic Anion Transporters (OATs) Inhibitors of OAT1 and OAT3 Probenecid Ketoprofen Indomethacin Ki values below therapeutic concentrations of unbound drug.

30. DRUG-DRUG INTERACTIONS IN VIVO AND IN VITRO STUDIES: Focus on Transporters Background:Focus on P-gp Other Transporters Questions:

31. Kinetic Values of Substrates of P-gp From Jiunn Lin

32. Substrates of P-gp Cyclosporin Digoxin Indinavir Ivermectin Nelfinavir Paclitaxel Quinidine Saquinavir Tacrolimus Verapamil Vinblastine