Challenges. Benefits. Control of viral load in plasma. Drug-drug interactions. Adverse effects/drug toxicities. Delay in HIV drug resistance

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2 Benefits Challenges Control of viral load in plasma Drug-drug interactions Delay in HIV drug resistance Longer life expectancy Adverse effects/drug toxicities Drug resistant HIV strains

3 Raltegravir

4 Structural/pharmacokinetic/pharmacodynamic parameters of Raltegravir Chemical structure: Dosing IC mg bid 16 ng/ml Protein binding 83% Metabolism UGT1A1 Molecular formula: C 20 H 21 FN 6 O 5 Molecular weight: Excretion Feces (51%); Urine (32%) C max, C min and AUC Half-life (T 1/2 ) C max : 2 µg/ml, C min : 67 ng/ml AUC: 7 µg/ml.h ~9 hours CSF to plasma ratio Semen to plasma ratio Kassahun et al, Drug Meta Dis. 35: (2007); Adams et al., Curr Opin HIV AiIDS 7: (2012); Barau et al., 2010; Yilmaz et al, 2009)

5 Raltegravir UGT1A1 Interactions between ARVs: Raltegravir and NRTIs, NNRTIs, PIs, CCR5 NRTIs Tenofovir RAL AUC: 49% NNRTIs Efavirenz RAL AUC: 36% PIs Atazanavir RAL AUC: 72% Atazanavir (RTV) RAL AUC: 41% Tipranavir RAL AUC: 24% Darunavir RAL AUC: 29% CCR5 Maraviroc RAL AUC: 37%???? Adams et al. Curr. Opin. HIV AIDS 7: (2012); Kis et al. Trends Pharmacol.Sci. 31: (2010); Iwamoto, et al., Clin Infect Dis 47: (2008); Panel on Antiretroviral Guidelines for Adults and Adolescents. (2011) DHHS, DOI:1-166 (

6 Efflux pump PIs, NRTIs CCR5-antagonist NRTIs PIs NRTIs Out P-gp Plasma BCRP membrane MRP1 ATP ADP+Pi In Wide-range of substrate specificity including many xenobiotics and ARVs substrate gradient Expressed in different tissues such as small intestine, liver, kidney, brain, etc. Uptake carrier Petrovic et al. Mol. Interv. 7: (2007); Kis et al. Trends Pharmacol.Sci. 31: (2010)

7 Rationale At present, limited in vitro data are available on the potential interaction between raltegravir and drug efflux/influx transporters. Recently, clinical studies demonstrated several raltegravir interactions with ARV drugs. Although some of these interactions are demonstrated to be regulated by UGT1A1, others remain unexplained and we propose they could be mediated by drug transporters.

8 Hypothesis Raltegravir can act as an inhibitor, substrate and/or inducer of drug efflux and /or influx transporters, thus resulting in drug-drug interactions which could compromise anti-hiv pharmacotherapy in the clinic.

9 Objectives To assess in vitro, potential interactions of raltegravir with drug efflux transporters in transporter overexpressing cell culture systems. To investigate in vitro, the permeability of raltegravir, at human blood-tissue barriers by using specific cell cultures models well characterized in our laboratory for each anatomical site (e.g., blood-brain barrier, bloodtestes barrier, blood-intestinal barrier). To evaluate mechanisms of drug-drug interactions observed in the clinic.

10 WT (MDA-WT) P-gp overexpressing (MDA-MDR1) WT (HEK-WT) BCRP overexpressing (HEK-ABCG2) WT (HeLa-WT) MRP1 overexpressing (HeLa-MRP1 ) Research Plan P-gp BCRP MRP1 P-gp overexpressing (MDA-MDR1) BCRP overexpressing (HEK-ABCG2) MRP1 overexpressing (HeLa-MRP1) Raltegravir inhibitor properties Rhodamine-6G (R-6G) [ 3 H]-Mitoxantrone BCECF PSC833 Cyclosporine A (CSA) kda Raltegravir P-gp 100 [ 3 H] substrate properties BCRP (170 kda) 72 (72 kda) 225 Actin (42 kda) Ko Actin (42 kda) Fumitremorgin 35 C kda (FTC) kda MK571 Reversan MRP1 (190 kda) Actin (42 kda)

11 No inhibitor With inhibitor Wild Type Overexpressing

12 Raltegravir is not an inhibitor but a substrate of P-gp P-gp overexpressing * * n=3; p <0.001 n=3; p <0.001 n=3; p <0.001

13 Raltegravir is not an inhibitor but a substrate of BCRP BCRP overexpressing * * n=3; n=3; p <0.001 p <0.001 n=3; p <0.001

14 Raltegravir is not an inhibitor or substrate of MRP1 MRP1 overexpressing n=3; p <0.001 n=3

15 Summary and future directions Raltegravir does not inhibit P-gp, MRP1 and BCRP mediated transport. Raltegravir can serve as a substrate of drug efflux transporters, P-gp and BCRP but not of MRP1. Ongoing studies are focussed on investigating the permeability of raltegravir, at human blood-tissue barrier sites, using in vitro representative cell culture systems (e.g., hcmec/d3, Caco2, Sertoli cells). Reported clinical raltegravir interactions with the following ARV drugs: tenofovir, efavirenz, darunavir and maraviroc cannot not be explained through UGT1A1-mediated metabolic pathways. However, these drugs are known to be substrates and/or inhibitors of several efflux/influx transporters (i.e.,p-gp and BCRP) and could potentially interact at this level with raltegravir. Future in vitro and in situ studies will investigate this hypothesis.

16 Acknowledgements Dr. Reina Bendayan Dr Maria Fabiana De Rosa Monica Zhang Olena Kis and Rest of the lab members Merck Canada Inc.