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Han, Hyo Kyung; Vrueh, Remco L. A. de; Rhie, Julie K.; Covitz, Kuang Ming Y.; Smith, Philip L.; Lee, Chao Pin; Oh, Doo Man; Sadée, Wolfgang; Amidon, Gordon L.

doi:10.1023/a:1011919319810

Cited by 289 publications

(101 citation statements)

References 25 publications

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“…While BPHL has relatively high K m values, it exhibits a catalytic efficiency comparable to that of carboxylesterase against some widely used synthetic substrates (28 (10) demonstrated that more than 90% of the drug in the receiver compartment was ACV rather than the prodrug, indicating extensive intracellular VACV hydrolysis during cellular transport. This result suggests that one or more VACV-hydrolyzing enzymes, including BPHL in Caco-2 cells, are efficient at hydrolyzing VACV during mucosal cell transport.…”

Section: Discussionmentioning

confidence: 99%

“…The HPLC system consisted of a reversed-phase column (Ultrasphere, C-18, 5 m, 4.6 ϫ 250 mm, Beckman), Waters 515 pump; 996 Photodiode Array UV detector; and WISP model 712 autosampler (Waters, Milford, MA). The remaining prodrugs D/L-valacyclovir (D-VACV, VACV), glycyl ester acyclovir (Gly-ACV), and L-valyl ester AZT (Val-AZT) and production of parent drugs were assayed by HPLC as previously described (10). Briefly, prodrugs and their parent drugs except VGCV were separated and eluted by 2-8% acetonitrile in 40 mM ammonium formate buffer, pH 3.5, at a flow rate of 1 ml/min with detection at 254 nm.…”

Section: Methodsmentioning

confidence: 99%

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Identification of a Human Valacyclovirase

Kim¹,

Chu²,

Kim³

et al. 2003

Journal of Biological Chemistry

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Valacyclovir is the 5-valyl ester prodrug of acyclovir, an effective anti-herpetic drug. Systemic availability of acyclovir in humans is three to five times higher when administered orally as the prodrug. The increased bioavailability of valacyclovir is attributed to carrier-mediated intestinal absorption, via the hPEPT1 peptide transporter, followed by the rapid and complete conversion to acyclovir. The one or more human enzymes responsible for in vivo activation of the prodrug to the active drug and its conversion sites, however, have not been identified. In this report, we describe the purification, identification, and characterization of a human enzyme that activates valacyclovir to acyclovir. A protein with significant hydrolytic activity toward valacyclovir, the 5-glycyl ester of acyclovir, and the 5-valyl ester of zidovudine (AZT), was purified from Caco-2 cells derived from human intestine. Using a non-redundant data base search, the N-terminal 19-amino acid sequence of the purified 27-kDa, basic protein revealed a perfect match within the N terminus of a serine hydrolase, Biphenyl hydrolase-like (BPHL, gi:4757862) protein, previously cloned from human breast carcinoma. Recombinant BPHL exhibited significant hydrolytic activity for both valacyclovir and valganciclovir with specificity constants (k cat /K m ), 420 and 53.2 mM ؊1 ⅐s ؊1 , respectively. We conclude that BPHL may be an important enzyme activating valacyclovir and valganciclovir in humans and an important new target for prodrug design.Prodrugs of therapeutically active agents have been used to improve pharmaceutical, biopharmaceutical, and pharmacokinetic properties of numerous active therapeutic agents. Prodrugs are designed to be inactive until in vivo activation to the parent drug, and hence reliable in vivo activation of the prodrug is considered critical for their pharmacological activity (1). Identification of the mechanism of in vivo activation of prodrugs is important for prodrug design and for investigating clinical applications. Furthermore, design and development of prodrugs for humans has been significantly hampered by the unknown species differences in the activating enzymes. Thus, identification of the one or more prodrug-activating enzymes will significantly aid in the selection of animal models for human drug development.The participation of peptidases or esterases in prodrug activation will depend on the pro-moiety, its linker to the parent drug, as well as the parent drug. For several prodrugs, their in vivo activation mechanism has been studied in more detail. For example, the anti-cancer prodrug, CPT-11 (irinotecan), a carbamate derivative of 7-ethyl-10-hydroxycamptothecin, is converted to its active metabolite, 7-ethyl-10-hydroxycamptothecin by human carboxylesterases. The efficiency of hydrolysis varies depending on isoforms such that carboxylesterase 2 (hCE2) 1 and intestinal carboxylesterase (hiCE) are more efficient activators than human liver carboxylesterase 1 (hCE1) (2-4). The angiotensin-converting enzyme inhibitor...

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Identification of a Human Valacyclovirase

Kim¹,

Chu²,

Kim³

et al. 2003

Journal of Biological Chemistry

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“…Involvement of PEPT1 may explain the difference in bioavailability between valacyclovir (PEPT1 substrate) and acyclovir (non-substrate) in humans. 5,6) We have recently reported that rab8-null mice, which exhibit minimal expression of PEPT1 on apical membranes of small intestine, lack saturable uptake of a prototypical PEPT1 substrate glycylsarcosine (Gly-Sar).7) This may indicate a predominant role of PEPT1 in the peptide absorption. In addition to small intestine, PEPT1 is functionally expressed in some human cancer cell lines [8][9][10] and therefore would be a promising target for tumor detection.…”

mentioning

confidence: 99%

Direct Evidence for Efficient Transport and Minimal Metabolism of L-Cephalexin by Oligopeptide Transporter 1 in Budded Baculovirus Fraction

Mitsuoka

Tamai

Morohashi

et al. 2009

Biological & Pharmaceutical Bulletin

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The oligopeptide transporter PEPT1 (SLC15A1) accepts di-and tripeptides as endogenous substrates 1,2) and also transports various peptide-mimetic therapeutic agents (e.g., cephalexin).3) PEPT1 is primarily expressed in apical membrane of small intestinal epithelial cells. 4) PEPT1 is thought to be involved in gastrointestinal absorption of its substrates. Involvement of PEPT1 may explain the difference in bioavailability between valacyclovir (PEPT1 substrate) and acyclovir (non-substrate) in humans. 5,6) We have recently reported that rab8-null mice, which exhibit minimal expression of PEPT1 on apical membranes of small intestine, lack saturable uptake of a prototypical PEPT1 substrate glycylsarcosine (Gly-Sar).7) This may indicate a predominant role of PEPT1 in the peptide absorption. In addition to small intestine, PEPT1 is functionally expressed in some human cancer cell lines [8][9][10] and therefore would be a promising target for tumor detection. Indeed, a positron emitting probe targeted to PEPT1, 11 C-glycylsarcosine, was recently demonstrated to be able to distinguish between tumor and inflamed tissues. . 12-14) This D-cephalexin is now clinically used for chemotherapy. PEPT1 is presumably responsible for membrane permeation of D-cephalexin in small intestine, because small intestinal uptake of D-cephalexin assessed with an everted sac method was greatly reduced in rab8-null mice.15) The L-diastereomer of cephalexin (Lcephalexin) is also probably transported by PEPT1 in Caco-2 cells.16) However, intact L-cephalexin was not found in vesicles or proteoliposomes prepared from brush border membrane of intestinal epithelial cells. 17) Although, L-cephalexin was not detected, and the hydrolysis product, 7-aminodesacetoxycephalosporanic acid (7-ADCA), appeared very rapidly in serum and urine after oral administration in rats.18) This observation suggests that L-cephalexin can be absorbed from gastrointestinal tract. However, there has been no direct demonstration that L-cephalexin is transported by PEPT1 protein.We recently proposed that orally administered Lcephalexin might be transported and metabolized by PEPT1.13) Indeed, hydrolysis of L-cephalexin was markedly increased by exogenous transfection of PEPT1 gene into cultured cell lines, and metabolism of cephalexin was observed even in membrane-permeabilized cells expressing PEPT1, in which intracellular accumulation of L-cephalexin was negligible.13) This observation may imply that L-cephalexin hydrolysis is mediated by PEPT1 itself, although possible involvement of endogenous peptidases cannot be excluded, because these experimental systems utilized mammalian cells.The purpose of the present study was to clarify whether or not PEPT1 transports and/or metabolizes L-cephalexin. We performed L-cephalexin metabolism and uptake experiments using a highly purified PETP1 protein-expressing system, budded baculovirus 19) which lacks endogenous mammalian metabolic enzymes. MATERIALS AND METHODS MaterialsThe L-diastereoisomer of cephalexin was ob- The oligopepti...

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“…[7][8][9] Enhanced bioavailabilities of the amino acid prodrugs is attributed to carrier mediated intestinal absorption via intestinal transporters such as a human peptide transporter hPept1 or an amino acid transporter ATB 0,ϩ . 4,[10][11][12] Nucleoside antiviral and anticancer agents are important class of drugs for the fight against viral diseases and cancer. However, they often exhibit poor pharmaceutical and absorption, distribution, metabolism and excretion (ADME) properties.…”

mentioning

confidence: 99%

“…[1][2][3][4][5][6] Valine prodrugs of acyclovir and ganciclovir, valacyclovir and valganciclovir, respectively, exhibit 3-5 times higher systemic exposure than the parent compounds. [7][8][9] Enhanced bioavailabilities of the amino acid prodrugs is attributed to carrier mediated intestinal absorption via intestinal transporters such as a human peptide transporter hPept1 or an amino acid transporter ATB 0,ϩ .…”

mentioning

confidence: 99%

Interaction of Intestinal Nucleoside Transporter hCNT2 with Amino Acid Ester Prodrugs of Floxuridine and 2-Bromo-5,6-dichloro-1-.BETA.-D-ribofuranosylbenzimidazole

Shin

Kim

Vig

et al. 2006

Biological & Pharmaceutical Bulletin

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Targeting a specific molecule toward transporters by designing its prodrugs may be used to improve oral bioavailability or to reduce systemic toxicity. [1][2][3][4][5][6] Valine prodrugs of acyclovir and ganciclovir, valacyclovir and valganciclovir, respectively, exhibit 3-5 times higher systemic exposure than the parent compounds. [7][8][9] Enhanced bioavailabilities of the amino acid prodrugs is attributed to carrier mediated intestinal absorption via intestinal transporters such as a human peptide transporter hPept1 or an amino acid transporter ATB 0,ϩ . 4,[10][11][12] Nucleoside antiviral and anticancer agents are important class of drugs for the fight against viral diseases and cancer. However, they often exhibit poor pharmaceutical and absorption, distribution, metabolism and excretion (ADME) properties. Prodrug approaches that can potentially improve their pharmaceutical and ADME properties can be of great benefit in realizing the full potential of these agents.Clinically important nucleoside drugs such as cladribine, dideoxyinosine, fludarabine, acyclovir, ganciclovir, and abacavir, gemcitabine, azidothymidine, FUdR, cytarabine, zalcitabine and stavudine are known to interact with nucleoside transporters, which can influence their ADME properties. [13][14][15] A sodium-dependent concentrative nucleoside transporter hCNT2 has been cloned from human intestine. [16][17][18] The hCNT2 is abundantly expressed in the intestinal tissues, and is involved in transport of both naturally occurring nucleosides and clinically relevant nucleoside analogs. 13,18) Of the subtypes of concentrative nucleoside transporter hCNT1-3, hCNT2 exhibits a preference for purine nucleosides over pyrimidine nucleosides. 13,19) FUdR is a fluorinated pyrimidine nucleoside drug extensively used in the treatment of colon cancer. Although the mechanism of action and therapeutic effectiveness of FUdR are well understood, it has various side effects in gastrointestinal and bone marrow tissues. 20) Hence, FUdR is administered parenterally due to its poor oral bioavailability. Recently, benzimidazole nucleosides such as BDCRB, maribavir, and GW275175X have also been developed as a new class of antiviral drugs. [21][22][23] Although BDCRB was found to be a potent and selective inhibitor of human cytomegavirus (HCMV) replication, it had a poor pharmacokinetics profile with a very short plasma half-life and cytotoxicity. 24,25) In this regard, we attempted to develop amino acid ester prodrugs of FUdR and BDCRB to improve their pharmacokinetic properties. Although considerable progress has been made in the development of amino acid or dipeptide nucleoside prodrugs, little is known about the nucleoside transporters involved in the intestinal absorption of the prodrugs. In a previous report, 18) we demonstrated that FUdR and BDCRB were potent inhibitors of intestinal nucleoside transporter hCNT2. This suggests that hCNT2 may play an important role in the uptake of nucleoside compounds from the intestine. Therefore, it is relevant to characterize ho...

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Abstract: This study demonstrates that L-amino acid-nucleoside chimeras can serve as prodrugs to enhance intestinal absorption via the PEPT1 transporter, providing a novel strategy for improving oral therapy of nucleoside drugs.

Cited by 289 publications

References 25 publications

Identification of a Human Valacyclovirase

Identification of a Human Valacyclovirase

Direct Evidence for Efficient Transport and Minimal Metabolism of L-Cephalexin by Oligopeptide Transporter 1 in Budded Baculovirus Fraction

Interaction of Intestinal Nucleoside Transporter hCNT2 with Amino Acid Ester Prodrugs of Floxuridine and 2-Bromo-5,6-dichloro-1-.BETA.-D-ribofuranosylbenzimidazole

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