Structural Constraints Affect the Metabolism of 7-Ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin (CPT-11) by Carboxylesterases

Wadkins, Randy M.; Morton, Christopher L.; Weeks, James K.; Oliver, LaGora; Wierdl, Monika; Danks, Mary K.; Potter, Philip M.

doi:10.1124/mol.60.2.355

Cited by 61 publications

(92 citation statements)

References 23 publications

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“…This difference could be due to size-limited access of the bulky everolimus, as the active site of CES1 is smaller than that of CES2 (35). The inhibitory effects of everolimus were also different between human CES1 and mouse Ces1c, possibly reflecting a similar size-access difference, although little is known about Ces1c structure.…”

Section: Discussionmentioning

confidence: 82%

P-Glycoprotein, CYP3A, and Plasma Carboxylesterase Determine Brain and Blood Disposition of the mTOR Inhibitor Everolimus (Afinitor) in Mice

Tang

Sparidans

Cheung

et al. 2014

Clinical Cancer Research

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Section: Discussionmentioning

confidence: 82%

P-Glycoprotein, CYP3A, and Plasma Carboxylesterase Determine Brain and Blood Disposition of the mTOR Inhibitor Everolimus (Afinitor) in Mice

Tang

Sparidans

Cheung

et al. 2014

Clinical Cancer Research

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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%

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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“…22,26 However, a series of hCE1 mutants containing changes in residues that form the side door did not alter CPT-11 activation (data not shown). Since we have previously reported that the entrance to the active site significantly influences substrate hydrolysis, 31 we examined these domains in the crystal structures of rCE and hCE1. In rCE, the loops that formed the active site entrance were missing, suggesting considerable flexibility of these regions of the protein.…”

Section: Discussionmentioning

confidence: 99%

An improved human carboxylesterase for enzyme/prodrug therapy with CPT-11

et al. 2008

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CPT-11 is a potent antitumor agent that is activated by carboxylesterases (CE) and intracellular expression of CEs that can activate the drug results in increased cytotoxicity to the drug. As activation of (1-piperidino)-1-piperidino]carbonyloxycamptothecin) by human CEs is relatively inefficient, we have developed enzyme/prodrug therapy approaches based on the CE/CPT-11 combination using a rabbit liver CE (rCE). However, the in vivo application of this technology may be hampered by the development of an immune response to rCE. Therefore, we have developed a mutant human CE (hCE1m6), based on the human liver CE hCE1, that can activate CPT-11 approximately 70-fold more efficiently than the wild-type protein and can be expressed at high levels in mammalian cells. Indeed, adenoviral-mediated delivery of hCE1m6 with human tumor cells resulted in up to a 670-fold reduction in the IC 50 value for CPT-11, as compared to cells transduced with vector control virus. Furthermore, xenograft studies with human tumors expressing hCE1m6 confirm the ability of this enzyme to activate CPT-11 in vivo and induce antitumor activity. We propose that this enzyme should likely be less immunogenic than rCE and would be suitable for the in vivo application of CE/CPT-11 enzyme/prodrug therapy.

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Structural Constraints Affect the Metabolism of 7-Ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin (CPT-11) by Carboxylesterases

Cited by 61 publications

References 23 publications

P-Glycoprotein, CYP3A, and Plasma Carboxylesterase Determine Brain and Blood Disposition of the mTOR Inhibitor Everolimus (Afinitor) in Mice

P-Glycoprotein, CYP3A, and Plasma Carboxylesterase Determine Brain and Blood Disposition of the mTOR Inhibitor Everolimus (Afinitor) in Mice

Identification of a Human Valacyclovirase

An improved human carboxylesterase for enzyme/prodrug therapy with CPT-11

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