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Novel hepatotrophic prodrugs of the antiviral nucleoside 9-(2-phosphonylmethoxyethyl)adenine with improved pharmacokinetics and antiviral activity

E. A. L. BIESSEN^*1, A. R. P. M. VALENTIJN, R. L. A. DE VRUEH^*, E. VAN DE BILT^*, L. A. J. M. SLIEDREGT^*, P. PRINCE^*, M. K. BIJSTERBOSCH^*, J. H. VAN BOOM, G. A. VAN DER MAREL, P. J. ABRAHAMS and T. J. C. VAN BERKEL^*

^* Division of Biopharmaceutics, LACDR,
Department of Bio-Organic Chemistry, LIC, Leiden University; and
Department of Radiation Genetics and Chemical Mutagenesis, Leiden University Medical Center, Leiden, The Netherlands

¹Correspondence: Division of Biopharmaceutics, Leiden/Amsterdam Center for Drug Research, Sylvius Laboratories, Wassenaarseweg 72, Leiden, The Netherlands. E-mail: biessen{at}lacdr.leidenuniv.nl

The device of new hepatotrophic prodrugs of the antiviral nucleoside 9-(2-phosphonylmethoxyethyl)adenine (PMEA) with specificity for the asialoglycoprotein receptor on parenchymal liver cells is described. PMEA was conjugated to bi- and trivalent cluster glycosides (K(GN)₂ and K₂(GN)₃, respectively) with nanomolar affinity for the asialoglycoprotein receptor. The liver uptake of the PMEA prodrugs was more than 10-fold higher than that of the parent drug (52±6% and 62±3% vs. 4.8±0.7% of the injected dose for PMEA) and could be attributed for 90% to parenchymal cells. Accumulation of the PMEA prodrugs in extrahepatic tissue (e.g., kidney, skin) was substantially reduced. The ratio of parenchymal liver cell-to-kidney uptake—a measure of the prodrugs therapeutic window—was increased from 0.058 ± 0.01 for PMEA to 1.86 ± 0.57 for K(GN)₂-PMEA and even 2.69 ± 0.24 for K₂(GN)₃-PMEA. Apparently both glycosides have a similar capacity to redirect (antiviral) drugs to the liver. After cellular uptake, both PMEA prodrugs were converted into the parent drug, PMEA, during acidification of the lysosomal milieu (t_1/2100 min), and the released PMEA was rapidly translocated into the cytosol. The antiviral activity of the prodrugs in vitro was dramatically enhanced as compared to the parent drug (5- and 52-fold for K(GN)₂-PMEA and K₂(GN)₃-PMEA, respectively). Given the 15-fold enhanced liver uptake of the prodrugs, we anticipate that the potency in vivo will be similarly increased. We conclude that PMEA prodrugs have been developed with greatly improved pharmacokinetics and therapeutic activity against viral infections that implicate the liver parenchyma (e.g., HBV). In addition, the significance of the above prodrug concept also extends to drugs that intervene in other liver disorders such as cholestasis and dyslipidemia.—Biessen, E. A. L., Valentijn, A. R. P. M., de Vrueh, R. L. A., van de Bilt, E., Sliedregt, L A. J. M., Prince, P., Bijsterbosch, M. K., van Boom, J. H., van der Marel, G. A., Abrahams, P. J., van Berkel, T. J. C. Novel hepatotrophic prodrugs of the antiviral nucleoside 9-(2-phosphonylmethoxyethyl)adenine with improved pharmacokinetics and antiviral activity.

Key Words: asialoglycoprotein • HBV • HSV-1 • drug targeting • liver