Lymphatic Targeting of Tenofovir; Intracellular Pharmacokinetics and Viral Dynamics

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Lymphatic Targeting of Tenofovir Intracellular
Pharmacokinetics and Viral Dynamics

• Arnold Fridland, Ph.D, William Lee, Ph.D.
• Gilead Sciences, Inc.

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Tenofovir and Tenofovir DF (Viread)

• Tenofovir
• intracellular t 1/2 50h
• once daily dosing
• good resistance profile

• Viread
• human F 40
• Approved 11/01

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Human PK after IV infusion (1.0 mg/kg) of
Tenofovir and PO (300 mg) Tenofovir DF (Viread)
5000
1000
IV
PO
1000
F 40
Tenofovir (ng/mL)
100
100
10
10
0
6
12
0
12
24
36
48
Time Post Dose (Hr)

• No prodrug is observed in plasma following PO

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Viread Whats Not to Like?

• Good oral bioavailability gt 40
• Excellent efficacy, Viread/3TC/EFV result in gt
  70 patient below 50 copies/mL of HIV RNA _at_ wk
  144
• Safety comparable to placebo
• Available as combination pill w/FTC
• Leading selling NRTi

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? HIV RNA (day 7) vs Tenofovir Exposure After
Tenofovir (iv) or Viread (po) in Patients

• Prodrug leads to higher intracellular levels of
  TPP

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Objectives for 2nd GenerationTenofovir 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

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In Vitro/In Vivo Criteria for Prodrug Selection

• EC50 ag HIV-1
• MT-2 cell extracts
• Plasma stability
• PLCE

• Dog PK
• PBMC levels
• Tissue homogenates

Mono phenyl isopropylalaninyl mono amidate -
(R,S,S) GS-7340
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Stereochemistry at Phosphorus Determines
Metabolic Stability and Antiviral Activity
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In vitro Activity Metabolic Stability (t1/2) of
GS 7340
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HPLC Chromatograms after 1 hr Incubation of GS
7340 in Human Whole Blood
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Plasma and PBMC Profiles of GS 7340 and tenofovir
after iv infusion (0.5 mg/kg) and po (4.8 mg/kg)
in dogs
FPBMC 15
FPLASMA 23
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Plasma and PBMC AUC0-24 After Tenofovir (s.c.)
and Tenofovir Prodrugs (p.o.) in Dogs
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Distribution in Dogs After Administration of a
Single Oral Dose of 14C-Tenofovir DF or
14C-GS-7340
Tissue/Fluid Tenofovir DF Tenofovir DF GS-7340 GS-7340 Tissue Conc. Ratio of GS-7340 to TDF
Tissue/Fluid Dose Conc. (ug-eq/g) Dose Conc. (ug-eq/g) Tissue Conc. Ratio of GS-7340 to TDF
Liver 12.40 38.30 16.45 52.94 1.4
Kidney 4.58 87.90 3.78 80.21 0.9
Lungs 0.03 0.53 0.34 4.33 8.2
Iliac Lymph Nodes 0.00 0.51 0.01 5.42 10.6
Axillary Lymph Nodes 0.00 0.37 0.01 5.54 14.8
Inguinal Lymph Nodes 0.00 0.28 0.00 4.12 15.0
Mesenteric Lymph Nodes 0.00 1.20 0.04 6.88 5.7
Thyroid Gland 0.00 0.30 0.00 4.78 15.8
Pituitary Gland 0.00 0.23 0.00 1.80 7.8
Salivary Gland (LR) 0.00 0.45 0.03 5.54 12.3
Adrenal Gland 0.00 1.90 0.00 3.47 1.8
Spleen 0.00 0.63 0.17 8.13 12.8
Pancrease 0.00 0.57 0.01 3.51 6.2
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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