Interactions of the Dipeptide Ester Prodrugs of Acyclovir with the Intestinal Oligopeptide Transporter: Competitive Inhibition of Glycylsarcosine Transport in Human Intestinal Cell Line-Caco-2

Abstract

The oligopeptide transporter may be exploited to enhance the absorption of drugs by synthesizing their dipeptide ester prodrugs, which may be recognized as its substrates. Various dipeptide esters of acyclovir (ACV), an antiviral nucleoside analog, were synthesized. Enzymatic hydrolysis and affinity of the prodrugs toward the human intestinal peptide transporter hPEPT1 were studied using the human intestinal Caco-2 cell line. Affinity studies were performed by inhibiting the uptake of [ 3 H]glycylsarcosine by the prodrugs. The uptake of glycylsarcosine was found to be saturable at higher concentrations and was competitively inhibited by the prodrugs of ACV. All prodrugs except Tyr-Gly-ACV demonstrated a higher affinity (1.41-4.96 mM) toward hPEPT1 than cephalexin (8.19 Ϯ 2.12 mM), which was used as a positive control. Two prodrugs, Gly-Val-ACV and Val-Val-ACV, showed comparable affinity to Val-ACV, an amino acid prodrug of ACV recognized by PEPT1/PEPT2. The permeability of Gly-Val-ACV (2.99 Ϯ 0.59 ϫ 10 Ϫ6 cm/s) across Caco-2 was comparable with that of Val-ACV (3.01 Ϯ 0.21 ϫ 10 Ϫ6 cm/s) and was significantly inhibited (63%) in presence of glycylsarcosine. The transport of GVACV across Caco-2 was saturable at higher concentrations, and the parameters were calculated as K m 3.16 Ϯ 0.31 mM and V max 0.014 Ϯ 0.00058 nmol cm Ϫ2 min Ϫ1 . Overall, the results suggest that the dipeptide prodrugs of ACV have a high affinity toward the intestinal oligopeptide transporter hPEPT1 and therefore seem to be promising candidates in the treatment of ocular and oral herpesvirus infections, because cornea and intestinal epithelia seem to express the oligopeptide transporters.

Pharmacokinetics of Novel Dipeptide Ester Prodrugs of Acyclovir after Oral Administration: Intestinal Absorption and Liver Metabolism

“…This method gave rapid and reproducible results. HPLC conditions for the other prodrugs have been reported previously (Anand et al, 2003). The limits of quantification were found to be ACV, 25 ng/ml; VACV, 50 ng/ml; GVACV, 100 ng/ml; VVACV, 125 ng/ml; VYACV, 250 ng/ml; and YACV, 250 ng/ml.…”

“…Results indicated that the dipeptide ester prodrugs of ACV exhibited high affinity toward the intestinal oligopeptide transporter, and the uptake of these prodrugs was efficiently mediated by hPEPT1 as suggested by significant inhibition of uptake of glycylsarcosine. These prodrugs hydrolyzed readily to regenerate the active parent drug, acyclovir (Anand et al, 2003). In this report, we describe pharmacokinetics and the bioavailability of these prodrugs after oral administration in Sprague-Dawley rats.…”

Ocular pharmacokinetics of acyclovir amino acid ester prodrugs in the anterior chamber: Evaluation of their utility in treating ocular HSV infections

“…Enzymatic and chemical processes are known to play an important role in the hydrolysis of prodrugs and it is well known that enzymatic processes frequently play a dominant role than the chemical process (Anand et al, 2003). The rank order of esterase activity in ocular tissues can be arranged in the following order; iris-ciliary body > cornea > aqueous humor ≫ lens (Lee et al, 1982;Lee et al, 1985).…”

Nonpolymeric nanoassemblies for ocular administration of acyclovir: Pharmacokinetic evaluation in rabbits

“…It is well known that esterases are present in several ocular structures, and their activity is the main factor responsible for the bioreversion of amino acid prodrugs of acyclovir [19], [39] and [42]. Our study employed a lipophilic prodrug of ACV, obtained by conjugation with 1,1′,2-trisnorsqualenoic acid, as has been proposed by Sarpietro et al [33] and [43].…”

“…We selected a prodrug that would increase the lipophilic character of acyclovir, optimizing its permeation through the cornea, and simultaneously the appropriate nanotechnology to provide prolonged release of acyclovir at the absorption site. Each of these approaches has been widely studied: macromolecular complex, amino acid ester, and dipeptide prodrugs of acyclovir were found to be more stable, more soluble, and capable of improving the bioavailability of ACV after oral and ocular administration [17], [19], [20], [21], [38] and [39], and colloidal carriers have been widely exploited to enhance corneal permeation, control drug release at the absorption site, and obtain a selective target of acyclovir [35], [40] and [41].…”