Wadkins RM

References (21)

Title : Insights and Ideas Garnered from Marine Metabolites for Development of Dual-Function Acetylcholinesterase and Amyloid-beta Aggregation Inhibitors - Stoddard_2014_Mar.Drugs_12_2114
Author(s) : Stoddard SV , Hamann MT , Wadkins RM
Ref : Mar Drugs , 12 :2114 , 2014
Abstract : Due to the diversity of biological activities that can be found in aquatic ecosystems, marine metabolites have been an active area of drug discovery for the last 30 years. Marine metabolites have been found to inhibit a number of enzymes important in the treatment of human disease. Here, we focus on marine metabolites that inhibit the enzyme acetylcholinesterase, which is the cellular target for treatment of early-stage Alzheimer's disease. Currently, development of anticholinesterase drugs with improved potency, and drugs that act as dual acetylcholinesterase and amyloid-beta aggregation inhibitors, are being sought to treat Alzheimer's disease. Seven classes of marine metabolites are reported to possess anti-cholinesterase activity. We compared these metabolites to clinically-used acetylcholinesterase inhibitors having known mechanisms of inhibition. We performed a docking simulation and compared them to published experimental data for each metabolite to determine the most likely mechanism of inhibition for each class of marine inhibitor. Our results indicate that several marine metabolites bind to regions of the acetylcholinesterase active site that are not bound by the clinically-used drugs rivastigmine, galanthamine, donepezil, or tacrine. We use the novel poses adopted for computational drug design of tighter binding anticholinesterase drugs likely to act as inhibitors of both acetylcholinesterase activity and amyloid-beta aggregation inhibition.
ESTHER : Stoddard_2014_Mar.Drugs_12_2114
PubMedSearch : Stoddard_2014_Mar.Drugs_12_2114
PubMedID: 24714126

Title : Global and local molecular dynamics of a bacterial carboxylesterase provide insight into its catalytic mechanism - Yu_2012_J.Mol.Model_18_2869
Author(s) : Yu X , Sigler SC , Hossain D , Wierdl M , Gwaltney SR , Potter PM , Wadkins RM
Ref : J Mol Model , 18 :2869 , 2012
Abstract : Carboxylesterases (CEs) are ubiquitous enzymes responsible for the detoxification of xenobiotics. In humans, substrates for these enzymes are far-ranging, and include the street drug heroin and the anticancer agent irinotecan. Hence, their ability to bind and metabolize substrates is of broad interest to biomedical science. In this study, we focused our attention on dynamic motions of a CE from B. subtilis (pnbCE), with emphasis on the question of what individual domains of the enzyme might contribute to its catalytic activity. We used a 10 ns all-atom molecular dynamics simulation, normal mode calculations, and enzyme kinetics to understand catalytic consequences of structural changes within this enzyme. Our results shed light on how molecular motions are coupled with catalysis. During molecular dynamics, we observed a distinct C-C bond rotation between two conformations of Glu310. Such a bond rotation would alternately facilitate and impede protonation of the active site His399 and act as a mechanism by which the enzyme alternates between its active and inactive conformation. Our normal mode results demonstrate that the distinct low-frequency motions of two loops in pnbCE, coil_5 and coil_21, are important in substrate conversion and seal the active site. Mutant CEs lacking these external loops show significantly reduced rates of substrate conversion, suggesting this sealing motion prevents escape of substrate. Overall, the results of our studies give new insight into the structure-function relationship of CEs and have implications for the entire family of alpha/beta fold family of hydrolases, of which this CE is a member.
ESTHER : Yu_2012_J.Mol.Model_18_2869
PubMedSearch : Yu_2012_J.Mol.Model_18_2869
PubMedID: 22127613

Title : In silico design and evaluation of carboxylesterase inhibitors - Stoddard_2010_J.Pestic.Sci_35_240
Author(s) : Stoddard SV , Yu X , Potter PM , Wadkins RM
Ref : Journal of Pesticide Science , 35 :240 , 2010
Abstract : Carboxylesterases (CEs) are important enzymes that catalyze biological detoxification, hydrolysis of certain pesticides, and metabolism of many esterified drugs. The development of inhibitors for CE has many potential uses, including increasing drug lifetime and altering biodistrubution; reducing or abrogating toxicity of metabolized drugs; and reducing pest resistance to insecticides. In this review, we discuss the major classes of known mammalian CE inhibitors and describe our computational efforts to design new scaffolds for development of novel, selective inhibitors. We discuss several strategies for in silico inhibitor development, including structure docking, database searching, multidimensional quantitative structure-activity analysis (QSAR), and a newly-used approach that uses QSAR combined with de novo drug design. While our research is focused on design of specific inhibitors for human intestinal carboxylesterase (hiCE), the methods described are generally applicable to inhibitors of other enzymes, including CE from other tissues and organisms.
ESTHER : Stoddard_2010_J.Pestic.Sci_35_240
PubMedSearch : Stoddard_2010_J.Pestic.Sci_35_240

Title : Biochemical and molecular analysis of carboxylesterase-mediated hydrolysis of cocaine and heroin - Hatfield_2010_Br.J.Pharmacol_160_1916
Author(s) : Hatfield MJ , Tsurkan LG , Hyatt JL , Yu X , Edwards CC , Hicks LD , Wadkins RM , Potter PM
Ref : British Journal of Pharmacology , 160 :1916 , 2010
Abstract : BACKGROUND AND PURPOSE Carboxylesterases (CEs) metabolize a wide range of xenobiotic substrates including heroin, cocaine, meperidine and the anticancer agent CPT-11. In this study, we have purified to homogeneity human liver and intestinal CEs and compared their ability with hydrolyse heroin, cocaine and CPT-11. EXPERIMENTAL APPROACH: The hydrolysis of heroin and cocaine by recombinant human CEs was evaluated and the kinetic parameters determined. In addition, microsomal samples prepared from these tissues were subjected to chromatographic separation, and substrate hydrolysis and amounts of different CEs were determined. KEY RESULTS: In contrast to previous reports, cocaine was not hydrolysed by the human liver CE, hCE1 (CES1), either as highly active recombinant protein or as CEs isolated from human liver or intestinal extracts. These results correlated well with computer-assisted molecular modelling studies that suggested that hydrolysis of cocaine by hCE1 (CES1), would be unlikely to occur. However, cocaine, heroin and CPT-11 were all substrates for the intestinal CE, hiCE (CES2), as determined using both the recombinant protein and the tissue fractions. Again, these data were in agreement with the modelling results. CONCLUSIONS AND IMPLICATIONS: These results indicate that the human liver CE is unlikely to play a role in the metabolism of cocaine and that hydrolysis of this substrate by this class of enzymes is via the human intestinal protein hiCE (CES2). In addition, because no enzyme inhibition is observed at high cocaine concentrations, potentially this route of hydrolysis is important in individuals who overdose on this agent.
ESTHER : Hatfield_2010_Br.J.Pharmacol_160_1916
PubMedSearch : Hatfield_2010_Br.J.Pharmacol_160_1916
PubMedID: 20649590
Gene_locus related to this paper: human-CES1

Title : Improved, selective, human intestinal carboxylesterase inhibitors designed to modulate 7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin (Irinotecan\; CPT-11) toxicity - Hicks_2009_J.Med.Chem_52_3742
Author(s) : Hicks LD , Hyatt JL , Stoddard S , Tsurkan L , Edwards CC , Wadkins RM , Potter PM
Ref : Journal of Medicinal Chemistry , 52 :3742 , 2009
Abstract : CPT-11 is an antitumor prodrug that is hydrolyzed by carboxylesterases (CE) to yield SN-38, a potent topoisomerase I poison. However, the dose limiting toxicity delays diarrhea that is thought to arise, in part, from activation of the prodrug by a human intestinal CE (hiCE). Therefore, we have sought to identify selective inhibitors of hiCE that may have utility in modulating drug toxicity. We have evaluated one such class of molecules (benzene sulfonamides) and developed QSAR models for inhibition of this protein. Using these predictive models, we have synthesized a panel of fluorene analogues that are selective for hiCE, demonstrating no cross reactivity to the human liver CE, hCE1, or toward human cholinesterases, and have K(i) values as low as 14 nM. These compounds prevented hiCE-mediated hydrolysis of the drug and the potency of enzyme inhibition correlated with the clogP of the molecules. These studies will allow the development and application of hiCE-specific inhibitors designed to selectively modulate drug hydrolysis in vivo.
ESTHER : Hicks_2009_J.Med.Chem_52_3742
PubMedSearch : Hicks_2009_J.Med.Chem_52_3742
PubMedID: 19534556

Title : Comparison of benzil and trifluoromethyl ketone (TFK)-mediated carboxylesterase inhibition using classical and 3D-quantitative structure-activity relationship analysis - Harada_2009_Bioorg.Med.Chem_17_149
Author(s) : Harada T , Nakagawa Y , Wadkins RM , Potter PM , Wheelock CE
Ref : Bioorganic & Medicinal Chemistry , 17 :149 , 2009
Abstract : Carboxylesterases are enzymes that hydrolyze a broad suite of endogenous and exogenous ester-containing compounds to the corresponding alcohol and carboxylic acid. These enzymes metabolize a number of therapeutics including the anti-tumor agent CPT-11, the anti-viral drug oseltamivir, and the anti-thrombogenic agent clopidogrel as well as many agrochemicals. In addition, carboxylesterases are involved in lipid homeostasis, including cholesterol metabolism and transport with a proposed role in the development of atherosclerosis. Several different scaffolds capable of inhibiting carboxylesterases have been reported, including organophosphates, carbamates, trifluoromethyl ketone-containing structures (TFKs), and aromatic ethane-1,2-diones. Of these varied groups, only the 1,2-diones evidence carboxylesterase isoform-selectivity, which is an important characteristic for therapeutic application and probing biological mechanisms. This study constructed a series of classical and 3D-QSAR models to examine the physiochemical parameters involved in the observed selectivity of three mammalian carboxylesterases: human intestinal carboxylesterase (hiCE), human carboxylesterase 1 (hCE1), and rabbit carboxylesterase (rCE). CoMFA-based models for the benzil-analogs described 88%, 95% and 76% of observed activity for hiCE, hCE1 and rCE, respectively. For TFK-containing compounds, two distinct models were constructed using either the ketone or gem-diol form of the inhibitor. For all three enzymes, the CoMFA ketone models comprised more biological activity than the corresponding gem-diol models; however the differences were small with described activity for all models ranging from 85-98%. A comprehensive model incorporating both benzil and TFK structures described 92%, 85% and 87% of observed activity for hiCE, hCE1 and rCE, respectively. Both classical and 3D-QSAR analysis showed that the observed isoform-selectivity with the benzil-analogs could be described by the volume parameter. This finding was successfully applied to examine substrate selectivity, demonstrating that the relative volumes of the alcohol and acid moieties of ester-containing substrates were predictive for whether hydrolysis was preferred by hiCE or hCE1. Based upon the integrated benzil and TFK model, the next generation inhibitors should combine the A-ring and the 1,2-dione of the benzil inhibitor with the long alkyl chain of the TFK-inhibitor in order to optimize selectivity and potency. These new inhibitors could be useful for elucidating the role of carboxylesterase activity in fatty acid homeostasis and the development of atherosclerosis as well as effecting the controlled activation of carboxylesterase-based prodrugs in situ.
ESTHER : Harada_2009_Bioorg.Med.Chem_17_149
PubMedSearch : Harada_2009_Bioorg.Med.Chem_17_149
PubMedID: 19062296

Title : Modifications of human carboxylesterase for improved prodrug activation - Hatfield_2008_Expert.Opin.Drug.Metab.Toxicol_4_1153
Author(s) : Hatfield JM , Wierdl M , Wadkins RM , Potter PM
Ref : Expert Opin Drug Metab Toxicol , 4 :1153 , 2008
Abstract : BACKGROUND: Carboxylesterases (CEs) are ubiquitous enzymes responsible for the hydrolysis of numerous clinically useful drugs. As ester moieties are frequently included in molecules to improve their water solubility and bioavailability, de facto they become substrates for CEs. OBJECTIVE: In this review, we describe the properties of human CEs with regard to their ability to activate anticancer prodrugs and demonstrate how structure-based design can be used to modulate substrate specificity and to increase efficiency of hydrolysis.
METHODS: A specific example using CPT-11 and a human liver CE is discussed. However, these techniques can be applied to other enzymes and their associated prodrugs.
RESULTS: Structure-guided mutagenesis of CEs can be employed to alter substrate specificity and generate novel enzymes that are efficacious at anticancer prodrug activation.
ESTHER : Hatfield_2008_Expert.Opin.Drug.Metab.Toxicol_4_1153
PubMedSearch : Hatfield_2008_Expert.Opin.Drug.Metab.Toxicol_4_1153
PubMedID: 18721110

Title : Analysis of mammalian carboxylesterase inhibition by trifluoromethylketone-containing compounds - Wadkins_2007_Mol.Pharmacol_71_713
Author(s) : Wadkins RM , Hyatt JL , Edwards CC , Tsurkan L , Redinbo MR , Wheelock CE , Jones PD , Hammock BD , Potter PM
Ref : Molecular Pharmacology , 71 :713 , 2007
Abstract : Carboxylesterases (CE) are ubiquitous enzymes that hydrolyze numerous ester-containing xenobiotics, including complex molecules, such as the anticancer drugs irinotecan (CPT-11) and capecitabine and the pyrethroid insecticides. Because of the role of CEs in the metabolism of many exogenous and endogenous ester-containing compounds, a number of studies have examined the inhibition of this class of enzymes. Trifluoromethylketone-containing (TFK) compounds have been identified as potent CE inhibitors. In this article, we present inhibition constants for 21 compounds, including a series of sulfanyl, sulfinyl, and sulfonyl TFKs with three mammalian CEs, as well as human acetyl- and butyrylcholinesterase. To examine the nature of the slow tight-binding inhibitor/enzyme interaction, assays were performed using either a 5-min or a 24-h preincubation period. Results showed that the length of the preincubation interval significantly affects the inhibition constants on a structurally dependent basis. The TFK-containing compounds were generally potent inhibitors of mammalian CEs, with Ki values as low as 0.3 nM observed. In most cases, thioether-containing compounds were more potent inhibitors then their sulfinyl or sulfonyl analogs. QSAR analyses demonstrated excellent observed versus predicted values correlations (r2 ranging from 0.908-0.948), with cross-correlation coefficients (q2) of approximately 0.9. In addition, pseudoreceptor models for the TKF analogs were very similar to structures and models previously obtained using benzil- or sulfonamide-based CE inhibitors. These studies indicate that more potent, selective CE inhibitors, containing long alkyl or aromatic groups attached to the thioether chemotype in TFKs, can be developed for use in in vivo enzyme inhibition.
ESTHER : Wadkins_2007_Mol.Pharmacol_71_713
PubMedSearch : Wadkins_2007_Mol.Pharmacol_71_713
PubMedID: 17167034

Title : Analysis of the inhibition of mammalian carboxylesterases by novel fluorobenzoins and fluorobenzils - Hicks_2007_Bioorg.Med.Chem_15_3801
Author(s) : Hicks LD , Hyatt JL , Moak T , Edwards CC , Tsurkan L , Wierdl M , Ferreira AM , Wadkins RM , Potter PM
Ref : Bioorganic & Medicinal Chemistry , 15 :3801 , 2007
Abstract : We have synthesized and assessed the ability of symmetrical fluorobenzoins and fluorobenzils to inhibit mammalian carboxylesterases (CE). The majority of the latter were excellent inhibitors of CEs however unexpectedly, the fluorobenzoins were very good enzyme inhibitors. Positive correlations were seen with the charge on the hydroxyl carbon atom, the carbonyl oxygen, and the Hammett constants for the derived K(i) values with the fluorobenzoins.
ESTHER : Hicks_2007_Bioorg.Med.Chem_15_3801
PubMedSearch : Hicks_2007_Bioorg.Med.Chem_15_3801
PubMedID: 17399985

Title : Selective inhibition of carboxylesterases by isatins, indole-2,3-diones - Hyatt_2007_J.Med.Chem_50_1876
Author(s) : Hyatt JL , Moak T , Hatfield MJ , Tsurkan L , Edwards CC , Wierdl M , Danks MK , Wadkins RM , Potter PM
Ref : Journal of Medicinal Chemistry , 50 :1876 , 2007
Abstract : Carboxylesterases (CE) are ubiquitous enzymes thought to be responsible for the metabolism and detoxification of xenobiotics. Numerous clinically used drugs including Demerol, lidocaine, capecitabine, and CPT-11 are hydrolyzed by these enzymes. Hence, the identification and application of selective CE inhibitors may prove useful in modulating the metabolism of esterified drugs in vivo. Having recently identified benzil (diphenylethane-1,2-dione) as a potent selective inhibitor of CEs, we sought to evaluate the inhibitory activity of related 1,2-diones toward these enzymes. Biochemical assays and kinetic studies demonstrated that isatins (indole-2,3-diones), containing hydrophobic groups attached at a variety of positions within these molecules, could act as potent, specific CE inhibitors. Interestingly, the inhibitory potency of the isatin compounds was related to their hydrophobicity, such that compounds with clogP values of <1.25 were ineffective at enzyme inhibition. Conversely, analogs demonstrating clogP values>5 routinely yielded Ki values in the nM range. Furthermore, excellent 3D QSAR correlates were obtained for two human CEs, hCE1 and hiCE. While the isatin analogues were generally less effective at CE inhibition than the benzils, the former may represent valid lead compounds for the development of inhibitors for use in modulating drug metabolism in vivo.
ESTHER : Hyatt_2007_J.Med.Chem_50_1876
PubMedSearch : Hyatt_2007_J.Med.Chem_50_1876
PubMedID: 17378546

Title : Planarity and constraint of the carbonyl groups in 1,2-diones are determinants for selective inhibition of human carboxylesterase 1 - Hyatt_2007_J.Med.Chem_50_5727
Author(s) : Hyatt JL , Wadkins RM , Tsurkan L , Hicks LD , Hatfield MJ , Edwards CC , Ross CR, 2nd , Cantalupo SA , Crundwell G , Danks MK , Guy RK , Potter PM
Ref : Journal of Medicinal Chemistry , 50 :5727 , 2007
Abstract : Carboxylesterases (CE) are ubiquitous enzymes responsible for the detoxification of xenobiotics, including numerous clinically used drugs. Therefore, the selective inhibition of these proteins may prove useful in modulating drug half-life and bioavailability. Recently, we identified 1,2-diones as potent inhibitors of CEs, although little selectivity was observed in the inhibition of either human liver CE (hCE1) or human intestinal CE (hiCE). In this paper, we have further examined the inhibitory properties of ethane-1,2-diones toward these proteins and determined that, when the carbonyl oxygen atoms are cis-coplanar, the compounds demonstrate specificity for hCE1. Conversely, when the dione oxygen atoms are not planar (or are trans-coplanar), the compounds are more potent at hiCE inhibition. These properties have been validated in over 40 1,2-diones that demonstrate inhibitory activity toward at least one of these enzymes. Statistical analysis of the results confirms the correlation (P < 0.001) between the dione dihedral angle and the preferential inhibition of either hiCE or hCE1. Overall, the results presented here define the parameters necessary for small molecule inhibition of human CEs.
ESTHER : Hyatt_2007_J.Med.Chem_50_5727
PubMedSearch : Hyatt_2007_J.Med.Chem_50_5727
PubMedID: 17941623

Title : Carboxylesterases--detoxifying enzymes and targets for drug therapy - Potter_2006_Curr.Med.Chem_13_1045
Author(s) : Potter PM , Wadkins RM
Ref : Curr Med Chem , 13 :1045 , 2006
Abstract : Carboxylesterases (CE) are ubiquitous enzymes responsible for the detoxification of xenobiotics. Many therapeutically useful drugs are metabolized by these proteins which impacts upon the efficiency of drug treatment. In some instances, CEs convert inactive prodrugs to active metabolites, a process that is essential for biological activity. Such compounds include the anticancer agents CPT-11 (3) and capecitabine (4), the antibiotics Ceftin (9) and Vantin, as well as the illicit street drug heroin (6). However, more commonly, CEs hydrolyze many esterified drugs to inactive products that are then excreted. Agents such as flestolol (11), meperidine (5), lidocaine (8) and cocaine (7), are all hydrolyzed and inactivated by these enzymes. Therefore the efficacy of esterified drugs will be dependent upon the distribution and catalytic activity of different CEs. In this review, we examine the structural aspects of CEs and their roles in drug detoxification and propose that modulation of CE activity may allow for improvements in, and potentiation of, drug efficacy.
ESTHER : Potter_2006_Curr.Med.Chem_13_1045
PubMedSearch : Potter_2006_Curr.Med.Chem_13_1045
PubMedID: 16611083

Title : Inhibition of acetylcholinesterase by the anticancer prodrug CPT-11 - Hyatt_2005_Chem.Biol.Interact_157-158_247
Author(s) : Hyatt JL , Tsurkan L , Morton CL , Yoon KJ , Harel M , Brumshtein B , Silman I , Sussman JL , Wadkins RM , Potter PM
Ref : Chemico-Biological Interactions , 157-158 :247 , 2005
Abstract : CPT-11 (irinotecan, 7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin) is an anticancer prodrug that has been approved for the treatment of colon cancer. It is a member of the camptothecin class of drugs and activation to the active metabolite SN-38, is mediated by carboxylesterases (CE). SN-38 is a potent topoisomerase I poison and is highly effective at killing human tumor cells, with IC50 values in the low nM range. However, upon high dose administration of CPT-11 to cancer patients, a cholinergic syndrome is observed, that can be rapidly ameliorated by atropine. This suggests a direct interaction of the drug or its metabolites with acetylcholinesterase (AChE). Kinetic studies indicated that CPT-11 was primarily responsible for AChE inhibition with the 4-piperidinopiperidine moiety, the major determinant in the loss of enzyme activity. Structural analogs of 4-piperidinopiperidine however, did not inhibit AChE, including a benzyl piperazine derivate of CPT-11. These results suggest that novel anticancer drugs could be synthesized that do not inhibit AChE, or alternatively, that novel AChE inhibitors could be designed based around the camptothecin scaffold.
ESTHER : Hyatt_2005_Chem.Biol.Interact_157-158_247
PubMedSearch : Hyatt_2005_Chem.Biol.Interact_157-158_247
PubMedID: 16257398

Title : Identification and characterization of novel benzil (diphenylethane-1,2-dione) analogues as inhibitors of mammalian carboxylesterases - Wadkins_2005_J.Med.Chem_48_2906
Author(s) : Wadkins RM , Hyatt JL , Wei X , Yoon KJ , Wierdl M , Edwards CC , Morton CL , Obenauer JC , Damodaran K , Beroza P , Danks MK , Potter PM
Ref : Journal of Medicinal Chemistry , 48 :2906 , 2005
Abstract : Carboxylesterases (CE) are ubiquitous enzymes responsible for the metabolism of xenobiotics. Because the structural and amino acid homology among esterases of different classes, the identification of selective inhibitors of these proteins has proved problematic. Using Telik's target-related affinity profiling (TRAP) technology, we have identified a class of compounds based on benzil (1,2-diphenylethane-1,2-dione) that are potent CE inhibitors, with K(i) values in the low nanomolar range. Benzil and 30 analogues demonstrated selective inhibition of CEs, with no inhibitory activity toward human acetylcholinesterase or butyrylcholinesterase. Analysis of structurally related compounds indicated that the ethane-1,2-dione moiety was essential for enzyme inhibition and that potency was dependent on the presence of, and substitution within, the benzene ring. 3D-QSAR analyses of these benzil analogues for three different mammalian CEs demonstrated excellent correlations of observed versus predicted K(i) (r(2) > 0.91), with cross-validation coefficients (q(2)) of 0.9. Overall, these results suggest that selective inhibitors of CEs with potential for use in clinical applications can be designed.
ESTHER : Wadkins_2005_J.Med.Chem_48_2906
PubMedSearch : Wadkins_2005_J.Med.Chem_48_2906
PubMedID: 15828829

Title : The 3D structure of the anticancer prodrug CPT-11 with Torpedo californica acetylcholinesterase rationalizes its inhibitory action on AChE and its hydrolysis by butyrylcholinesterase and carboxylesterase - Harel_2005_Chem.Biol.Interact_157-158_153
Author(s) : Harel M , Hyatt JL , Brumshtein B , Morton CL , Wadkins RM , Silman I , Sussman JL , Potter PM
Ref : Chemico-Biological Interactions , 157-158 :153 , 2005
Abstract : The anticancer prodrug CPT-11 is a highly effective camptothecin analog that has been approved for the treatment of colon cancer. The 2.6 angstroms resolution crystal structure of its complex with Torpedo californica acetylcholinesterase (TcAChE) demonstrates that CPT-11 binds to TcAChE and spans its gorge similarly to the Alzheimer drug, Aricept. The crystal structure clearly reveals the interactions, which contribute to the inhibitory action of CPT-11. Modeling of the complexes of CPT-11 with mammalian butyrylcholinesterase and carboxylesterase, both of which are known to hydrolyze the drug, shows how binding to either of the two enzymes yields a productive substrate-enzyme complex.
ESTHER : Harel_2005_Chem.Biol.Interact_157-158_153
PubMedSearch : Harel_2005_Chem.Biol.Interact_157-158_153
PubMedID: 16289500
Gene_locus related to this paper: torca-ACHE

Title : The crystal structure of the complex of the anticancer prodrug 7-ethyl-10-[4-(1-piperidino)-1-piperidino]-carbonyloxycamptothecin (CPT-11) with Torpedo californica acetylcholinesterase provides a molecular explanation for its cholinergic action - Harel_2005_Mol.Pharmacol_67_1874
Author(s) : Harel M , Hyatt JL , Brumshtein B , Morton CL , Yoon KJ , Wadkins RM , Silman I , Sussman JL , Potter PM
Ref : Molecular Pharmacology , 67 :1874 , 2005
Abstract : The anticancer prodrug 7-ethyl-10-[4-(1-piperidino)-1-piperidino-]carbonyloxycamptothecin (CPT-11) is a highly effective camptothecin analog that has been approved for the treatment of colon cancer. It is hydrolyzed by carboxylesterases to yield 7-ethyl-10-hydroxycamptothecin (SN-38), a potent topoisomerase I poison. However, upon high-dose intravenous administration of CPT-11, a cholinergic syndrome is observed that can be ameliorated by atropine. Previous studies have indicated that CPT-11 can inhibit acetylcholinesterase (AChE), and here, we provide a detailed analysis of the inhibition of AChE by CPT-11 and by structural analogs. These studies demonstrate that the terminal dipiperidino moiety in CPT-11 plays a major role in enzyme inhibition, and this has been confirmed by X-ray crystallographic studies of a complex of the drug with Torpedo californica AChE. Our results indicate that CPT-11 binds within the active site gorge of the protein in a fashion similar to that observed with the Alzheimer drug donepezil. The 3D structure of the CPT-11/AChE complex also permits modeling of CPT-11 complexed with mammalian butyrylcholinesterase and carboxylesterase, both of which are known to hydrolyze the drug to the active metabolite. Overall, the results presented here clarify the mechanism of AChE inhibition by CPT-11 and detail the interaction of the drug with the protein. These studies may allow the design of both novel camptothecin analogs that would not inhibit AChE and new AChE inhibitors derived from the camptothecin scaffold.
ESTHER : Harel_2005_Mol.Pharmacol_67_1874
PubMedSearch : Harel_2005_Mol.Pharmacol_67_1874
PubMedID: 15772291
Gene_locus related to this paper: torca-ACHE

Title : Inhibition of carboxylesterases by benzil (diphenylethane-1,2-dione) and heterocyclic analogues is dependent upon the aromaticity of the ring and the flexibility of the dione moiety - Hyatt_2005_J.Med.Chem_48_5543
Author(s) : Hyatt JL , Stacy V , Wadkins RM , Yoon KJ , Wierdl M , Edwards CC , Zeller M , Hunter AD , Danks MK , Crundwell G , Potter PM
Ref : Journal of Medicinal Chemistry , 48 :5543 , 2005
Abstract : Benzil has been identified as a potent selective inhibitor of carboxylesterases (CEs). Essential components of the molecule required for inhibitory activity include the dione moiety and the benzene rings, and substitution within the rings affords increased selectivity toward CEs from different species. Replacement of the benzene rings with heterocyclic substituents increased the K(i) values for the compounds toward three mammalian CEs when using o-nitrophenyl acetate as a substrate. Logarithmic plots of the K(i) values versus the empirical resonance energy, the heat of union of formation energy, or the aromatic stabilization energy determined from molecular orbital calculations for the ring structures yielded linear relationships that allowed prediction of the efficacy of the diones toward CE inhibition. Using these data, we predicted that 2,2'-naphthil would be an excellent inhibitor of mammalian CEs. This was demonstrated to be correct with a K(i) value of 1 nM being observed for a rabbit liver CE. In addition, molecular simulations of the movement of the ring structures around the dione dihedral indicated that the ability of the compounds to inhibit CEs was due, in part, to rotational constraints enforced by the dione moiety. Overall, these studies identify subdomains within the aromatic ethane-1,2-diones, that are responsible for CE inhibition.
ESTHER : Hyatt_2005_J.Med.Chem_48_5543
PubMedSearch : Hyatt_2005_J.Med.Chem_48_5543
PubMedID: 16107154

Title : Discovery of novel selective inhibitors of human intestinal carboxylesterase for the amelioration of irinotecan-induced diarrhea: synthesis, quantitative structure-activity relationship analysis, and biological activity - Wadkins_2004_Mol.Pharmacol_65_1336
Author(s) : Wadkins RM , Hyatt JL , Yoon KJ , Morton CL , Lee RE , Damodaran K , Beroza P , Danks MK , Potter PM
Ref : Molecular Pharmacology , 65 :1336 , 2004
Abstract : The dose-limiting toxicity of the highly effective anticancer agent 7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxy-camptothecin (irinotecan; CPT-11) is delayed diarrhea. This is thought to be caused by either bacteria-mediated hydrolysis of the glucuronide conjugate of the active metabolite 7-ethyl-10-hydroxycamptothecin (SN-38) or direct conversion of CPT-11 to SN-38 by carboxylesterases (CE) in the small intestine. After drug administration, a very high level of CPT-11 is present in the bile; this is deposited into the duodenum, the region of the gut with the highest levels of CE activity. Hence, it is likely that direct conversion of the drug to SN-38 is partially responsible for the diarrhea associated with this agent. In an attempt to ameliorate this toxicity, we have applied Target-Related Affinity Profiling to identify novel CE inhibitors that are selective inhibitors of the human intestinal enzyme (hiCE). Seven inhibitors, all sulfonamide derivatives, demonstrated greater than 200-fold selectivity for hiCE compared with the human liver CE hCE1, and none was an inhibitor of human acetylcholinesterase or butyrylcholinesterase. Quantitative structure-activity relationship (QSAR) analysis demonstrated excellent correlations with the predicted versus experimental Ki values (r2 = 0.944) for hiCE. Additionally, design and synthesis of a tetrafluorine-substituted sulfonamide analog, which QSAR indicated would demonstrate improved inhibition of hiCE, validated the computer predictive analyses. These and other phenyl-substituted sulfonamides compounds are regarded as lead compounds for the development of effective, selective CE inhibitors for clinical applications.
ESTHER : Wadkins_2004_Mol.Pharmacol_65_1336
PubMedSearch : Wadkins_2004_Mol.Pharmacol_65_1336
PubMedID: 15155827

Title : Structural constraints affect the metabolism of 7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin (CPT-11) by carboxylesterases - Wadkins_2001_Mol.Pharmacol_60_355
Author(s) : Wadkins RM , Morton CL , Weeks JK , Oliver L , Wierdl M , Danks MK , Potter PM
Ref : Molecular Pharmacology , 60 :355 , 2001
Abstract : 7-Ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin [CPT-11 (irinotecan)] is a water-soluble camptothecin-derived prodrug that is activated by esterases to yield the potent topoisomerase I poison SN-38. We identified a rabbit liver carboxylesterase (CE) that was very efficient at CPT-11 metabolism; however, a human homolog that was more than 81% identical to this protein activated the drug poorly. Recently, two other human CEs have been isolated that are efficient in the conversion of CPT-11 to SN-38, yet both demonstrate little homology to the rabbit protein. To understand this phenomenon, we have characterized a series of esterases from human and rabbit, including several chimeric proteins, for their ability to metabolize CPT-11. Computer predictive modeling indicated that the ability of each enzyme to activate CPT-11 was dependent on the size of the entrance to the active site. Kinetic studies with a series of nitrophenyl and naphthyl esters confirmed these predictions, indicating that activation of CPT-11 by a CE is constrained by size-limited access of the drug to the active site catalytic amino acid residues.
ESTHER : Wadkins_2001_Mol.Pharmacol_60_355
PubMedSearch : Wadkins_2001_Mol.Pharmacol_60_355
PubMedID: 11455023

Title : Water soluble 20(S)-glycinate esters of 10,11-methylenedioxycamptothecins are highly active against human breast cancer xenografts - Wadkins_1999_Cancer.Res_59_3424
Author(s) : Wadkins RM , Potter PM , Vladu B , Marty J , Mangold G , Weitman S , Manikumar G , Wani MC , Wall ME , Von Hoff DD
Ref : Cancer Research , 59 :3424 , 1999
Abstract : Water-soluble 20(S)-glycinate esters of two highly potent 10,11-methylenedioxy analogues of camptothecin (CPT) have been synthesized and evaluated for their ability to eradicate human breast cancer tumor xenografts. The glycinate ester moiety increases the water solubility of the 10,11-methylenedioxy analogues 4-16-fold. However, in contrast to CPT-11, a water-soluble CPT analogue that was recently approved for second line treatment of colorectal cancer, the 20(S)-glycinate esters do not require carboxylesterase for conversion to their active forms. The glycinate esters are hydrolyzed to their parent, free 20(S)-hydroxyl active analogues in phosphate buffer (pH 7.5) and in mouse and human plasma. The glycinate esters are also 20-40-fold less potent than CPT-11 in inhibiting human acetylcholinesterase. In vivo, we examined 20(S)-glycinate-10,11-methylenedioxycamptothecin, 20(S)-glycinate-7-chloromethyl-10,11-methylenedioxycamptothecin, and CPT-11. We found that the two 10,11-methylenedioxy analogues had antitumor activity against breast cancer xenografts that was comparable to that of CPT-11. Our results indicate that water-soluble 20(S)-glycinate esters of highly potent CPT analogues provide compounds that maintain biological activity, do not require interactions with carboxylesterases, and do not inhibit human acetylcholinesterase.
ESTHER : Wadkins_1999_Cancer.Res_59_3424
PubMedSearch : Wadkins_1999_Cancer.Res_59_3424
PubMedID: 10416605

Title : The anticancer prodrug CPT-11 is a potent inhibitor of acetylcholinesterase but is rapidly catalyzed to SN-38 by butyrylcholinesterase - Morton_1999_Cancer.Res_59_1458
Author(s) : Morton CL , Wadkins RM , Danks MK , Potter PM
Ref : Cancer Research , 59 :1458 , 1999
Abstract : Patients treated with high doses of CPT-11 rapidly develop a cholinergic syndrome that can be alleviated by atropine. Although CPT-11 was not a substrate for acetylcholinesterase (AcChE), in vitro assays confirmed that CPT-11 inhibited both human and electric eel AcChE with apparent K(i)s of 415 and 194 nM, respectively. In contrast, human or equine butyryl-cholinesterase (BuChE) converted CPT-11 to SN-38 with K(m)s of 42.4 and 44.2 microM for the human and horse BuChE, respectively. Modeling of CPT-11 within the predicted active site of AcChE and BuChE corroborated experimental results indicating that, although the drug was oriented correctly for activation, the constraints dictated by the active site gorge were such that CPT-11 would be unlikely to be activated by AcChE.
ESTHER : Morton_1999_Cancer.Res_59_1458
PubMedSearch : Morton_1999_Cancer.Res_59_1458
PubMedID: 10197614