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EASL 2018 FRI-352
Pharmacokinetic-pharmacodynamic modeling of Tenofovir
Exalidex in HBV subjects
R. Foster1, M. Conover1, C. Canizres1, D. Trepanier1, D. Ure1,
T. Matkovits1, P. Mayo2. 1ContraVir Pharmaceuticals, Inc., Drug
Development, Edison, United States; 2University of Alberta, Pharmacy
and Pharmaceutical Sciences, Edmonton, Canada
Email: [email protected]
Background and Aims: Tenofovir Exalidex (TXL), a lipid conjugate
of tenofovir (TFV), is designed to mimic lysophosphatidylcholine to
take advantage of natural lipid uptake pathways and achieve high
intrahepatic concentrations of TFV diphosphate (TFV-PP) while
reducing the peripheral TFV concentrations associated with kidney
and bone toxicities. As it is not routinely feasible to measure
intrahepatic TFV-PP concentrations in patients, a pharmacokineticpharmacodynamic
(PK-PD) modelwas developed to aid and optimize
further clinical development of TXL.
Method: TXL was administered to 50 HBV subjects (fasted) at doses
ranging from 10–100 mg/day orally. The 50 mg cohort (n = 10) was
used to derive PK-PD modeling, as this dose resulted in viral load (VL)
reductions (log10) that were not statistically different from Standard of-
Care (SOC, 300 mg, tenofovir disoproxil fumarate). Steady-state PK
modeling was generated using linear trapezoidal, linear interpolation,
Non-Compartmental Analysis for a 24 hour dosing interval
(NCA, PhoenixWinNonLin Ver. 7.0). A linked PK-PD non-linear mixed
effects (NLME, Monolix 3.2) model was employed, using an inhibitory
Emax model. PK data were also examined using model-dependent
analyses. Data after 28 days dosing was used for the current model.
Results: Maximum VL reductions of up to 3.9 log10 were observed
with 50 mg/day TXL dosing for 28 days. The prodrug, TXL, rapidly
disappeared from plasma, with mean (SD) Cmax, Tmax, AUClast, and
t1/2 values of 51.28 (39.9) ng/ml, 1.60 (0.7) h, 109.44 (84.9) ng.h/ml,
and 2.10 (2.0) h, respectively, at day 28. TFV mean (SD) values for
Cmax, Tmax, AUClast, and t1/2 were 8.51 (2.0) ng/ml, 4.95 (2.2) h,
136.35 (33.5) ng.h/ml, and 23.3 (3.4) hours, respectively. The VL IC50
on Day 29 was 2.92 ng/ml. Additionally, TXL could be described using
a one-compartment model, whereas for TFV the model of best-fit was
multi-exponential.
Conclusion: TXL 50 mg VL reductions were not statistically different
(p = 0.19) from SOC, TDF. The PK-PD relationship after dosing on Day
28 was described using a NCA and inhibitory Emax model for TFV.
TXL was rapidly cleared compared with TFV, and the clinical antiviral
reduction IC50 approximated 3 ng/ml. Modeling promises to be a
useful tool for the further clinical development and optimization
of TXL.
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