1. RESEARCH Lymphatic Targeting of Tenofovir; Intracellular Pharmacokinetics and Viral Dynamics Arnold Fridland, Ph.D, William Lee, Ph.D. Gilead Sciences, Inc.

2. CONFIDENTIAL RESEARCH 2 Tenofovir and Tenofovir DF (Viread) Tenofovir intracellular t 1/2 ~ 50h once daily dosing good resistance profile Viread human % F = 40 Approved 11/01

3. CONFIDENTIAL RESEARCH 3 Human PK after IV infusion (1.0 mg/kg) of Tenofovir and PO (300 mg) Tenofovir DF (Viread) Time Post Dose (Hr) 0612 10 100 1000 5000 [Tenofovir] (ng/mL) 012243648 10 100 1000 PO No prodrug is observed in plasma following PO F = 40% IV

4. CONFIDENTIAL RESEARCH 4 Viread – What’s Not to Like? Good oral bioavailability > 40% Excellent efficacy, Viread/3TC/EFV result in > 70% patient below 50 copies/mL of HIV RNA @ wk 144 Safety comparable to placebo Available as combination pill w/FTC Leading selling NRTi

5. CONFIDENTIAL RESEARCH 5 Δ HIV RNA (day 7) vs Tenofovir Exposure After Tenofovir (iv) or Viread (po) in Patients Prodrug leads to higher intracellular levels of TPP

6. CONFIDENTIAL RESEARCH 6 Objectives for 2 nd Generation Tenofovir Prodrug Increased tissue exposure/decreased renal excretion Observable plasma levels of prodrug after p.o. Increased stability in blood compartment Preferential metabolism in lymphatic tissues

7. CONFIDENTIAL RESEARCH 7 In Vitro/In Vivo Criteria for Prodrug Selection EC 50 ag HIV-1 MT-2 cell extracts Plasma stability PLCE “Mono phenyl isopropylalaninyl mono amidate - (R,S,S)” GS-7340 Dog PK PBMC levels Tissue homogenates

8. CONFIDENTIAL RESEARCH 8 Stereochemistry at Phosphorus Determines Metabolic Stability and Antiviral Activity

9. CONFIDENTIAL RESEARCH 9 In vitro Activity & Metabolic Stability (t 1/2 ) of GS 7340

10. CONFIDENTIAL RESEARCH 10 HPLC Chromatograms after 1 hr Incubation of GS 7340 in Human Whole Blood Plasma PBMC GS-7340 GS-7161 PMPA 7161 PMPAp PMPApp min

11. CONFIDENTIAL RESEARCH 11 Plasma and PBMC Profiles of GS 7340 and tenofovir after iv infusion (0.5 mg/kg) and po (4.8 mg/kg) in dogs F PBMC = 15% F PLASMA = 23 %

12. CONFIDENTIAL RESEARCH 12 Plasma and PBMC AUC 0-24 After Tenofovir (s.c.) and Tenofovir Prodrugs (p.o.) in Dogs

13. CONFIDENTIAL RESEARCH 13 Distribution in Dogs After Administration of a Single Oral Dose of [ 14 C]-Tenofovir DF or [ 14 C]-GS-7340 Tissue/Fluid Tenofovir DFGS-7340 Tissue Conc. Ratio of GS-7340 to TDF % Dose Conc. (ug-eq/g) % Dose Conc. (ug-eq/g) Liver12.4038.3016.4552.941.4 Kidney4.5887.903.7880.210.9 Lungs0.030.530.344.338.2 Iliac Lymph Nodes0.000.510.015.4210.6 Axillary Lymph Nodes0.000.370.015.5414.8 Inguinal Lymph Nodes0.000.280.004.1215.0 Mesenteric Lymph Nodes0.001.200.046.885.7 Thyroid Gland0.000.300.004.7815.8 Pituitary Gland0.000.230.001.807.8 Salivary Gland (L+R)0.000.450.035.5412.3 Adrenal Gland0.001.900.003.471.8 Spleen0.000.630.178.1312.8 Pancrease0.000.570.013.516.2

14. CONFIDENTIAL RESEARCH 14 PK/PD Conclusions GS-7340-02 produces rapid achievement of high concentrations of GS-7340 in the plasma –Rapid distribution/elimination T1/2 ~ 20 - 40 minutes Sustained plasma concentrations of tenofovir –Lower tenofovir Cmax concentrations –AUC ~ proportional to tenofovir dose –Prolonged plasma T1/2 relative to TDF, greater accumulation to steady-state (150 mg 7340-02  300 mg TDF) Improved intracellular distribution of tenofovir to PBMCs –~ 6 to 20-fold higher concentrations relative to TDF 300 mg –No correlations between plasma or PBMC tenofovir exposure and antiviral activity