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Fan, Yun (2007) THE IN VITRO METABOLISM OF THREE ANTICANCER DRUGS. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Etoposide is a widely used topoisomerase II inhibitor particularly useful in the clinic for treatment of disseminated tumors, including childhood leukemia. However, its use is associated with the increased risk of development of secondary acute myelogenous leukemias. The mechanism behind this is still unclear. It was hypothesized that etoposide ortho-quinone, a reactive metabolite previously shown to be generated in vitro by myeloperoxidase, the major oxidative enzyme in the bone marrow cells from which the secondary leukemias arise, might be a contributor to the development of treatment-related secondary leukemias. Experiments showed that the glutathione adduct of etoposide ortho-quinone was formed in myeloperoxidase-expressing human myeloid leukemia HL60 cells treated with etoposide, that its formation was enhanced by addition of the myeloperoxidase substrate hydrogen peroxide, and that the glutathione adduct level was dependent on myeloperoxidase. Both the normoisotopic and a stable isotope-labeled version of the glutathione adduct were synthesized. The latter was used for liquid chromatography-mass spectrometry-based quantitative analyses of the adduct formed by the cells. Discodermolide and dictyostatin are two strucuturally related natural products that possess potent microtubule stabilizing activity. Discodermolide advanced to Phase II clinical trials, but the trials were halted for unannounced reasons. Here, both agents were found to be extensively metabolized by human liver microsomes in vitro. In order to determine the metabolic soft spots in the molecules, the chemical structures of the metabolites of discodermolide and dictyostatin were elucidated by liquid chromatography-mass spectrometry. At least eight metabolites of discodermolide and six metabolites of dictyostatin were formed in human liver microsomes in vitro. The terminal diene groups on discodermolide and dictyostatin were found to be the metabolic soft spots. Results from these studies can be used in future medicinal chemistry design and synthesis work to decrease metabolic rate and improve drug metabolism and pharmacokinetic properties, therefore decreasing the doses needed and perhaps even the toxicity.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Fan, Yunyuf8@pitt.eduYUF8
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairDay, Billy Wbday@pitt.eduBDAY
Committee MemberYalowich, Jack Cyalowich@pitt.eduYALOWICH
Committee MemberZemaitis, Michael Amaz@pitt.eduMAZ
Committee MemberVenkataramanan, Ramanrv@pitt.eduRV
Committee MemberPoloyac, Samuel Mpoloyac@pitt.eduPOLOYAC
Date: 17 April 2007
Date Type: Completion
Defense Date: 23 March 2007
Approval Date: 17 April 2007
Submission Date: 29 March 2007
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Institution: University of Pittsburgh
Schools and Programs: School of Pharmacy > Pharmaceutical Sciences
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: anticancer drugs; In vitro metabolism
Other ID:, etd-03292007-222254
Date Deposited: 10 Nov 2011 19:33
Last Modified: 15 Nov 2016 13:37


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