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`
`I
`
`Molecular Aspects
`of Monooxygenases
`and Bioactivation
`of Toxic Compounds
`
`Edited by
`Ernel Anne
`John B. Schenkrnan and
`Ernest Hodgson
`
`NATO ASI Series
`
`Series A: Life Sciences Vol. 202
`
`MYLAN PHARMS. INC. EXHIBIT 1118 PAGE 1
`
`

`

`'
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`
`NATO ASI Series
`
`Pliilii
`
`PUBLISHING CORPORATION
`
`PLENUM PUBLISHING CORPORATION
`New York • London
`
`ISBN 0·306·43823·2
`
`MYLAN PHARMS. INC. EXHIBIT 1118 PAGE 2
`
`

`

`Molecular Aspects
`of Monooxygenases
`and Bioactivation
`
`of Toxic Compounds
`
`MYLAN PHARMS. INC. EXHIBIT 1118 PAGE 3
`
`

`

`Molecular Aspects
`of Monooxygenases
`and Bioactivation
`of Toxic Compounds
`
`Edited by
`
`Emel Arinc
`Middle East Technical University
`Ankara, Turkey
`
`John B. Schenkman
`
`University of Connecticut Health Center
`Farmington, Connecticut
`
`and
`
`Ernest Hodgson
`North Carolina State University
`Raleigh, North Carolina
`
`Plenum Press
`New York and London
`
`Published in cooperation with NATO Scientific Affairs Division
`
`MYLAN PHARMS. INC. EXHIBIT 1118 PAGE 4
`
`

`

`NATO ASI Series
`Advanced Science Institutes Series
`
`A series presenting the results of activities sponsored by the NATO Science Committee,
`which aims at the dissemination of advanced scientific and technological knowledge,
`with a view to strengthening links between scientific communities.
`
`The series is published by an international board of publishers in conjunction with the
`NATO Scientific Affairs Division
`
`A
`B
`
`Lite Sciences
`Physics
`
`C Mathematical and Physical Sciences
`D Behavioral and Social Sciences
`E Applied Sciences
`
`F Computer and Systems Sciences
`G Ecological Sciences
`l-i Cell Biology
`l
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`
`Recent Volumes in this Series
`
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`Volume 196—Sensory Abilities of Cetaceans: Laboratory and Field Evidence
`edited by Jeanette A. Thomas and Ronald A. Kastelein
`
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`edited by Chryssostomos Chatgilialoglu and Klaus-Dieter Asmus
`
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`edited by G. E. Adams, A. Breccia, E. M. Fielden, and P. Wardman
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`edited by Gregory Gregoriadis, Anthony C. Allison, and George Poste
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`edited by Barbara L. Finlay, Giorgio lnnocenti, and Henning Scheich
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`Volume 202—Molecular Aspects of Monooxygenases and Bioactivation
`of Toxic Compounds
`edited by Emel Arinc, John B. Schenkman, and Ernest Hodgson
`
`5&5:
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`Series A: Life Scrences
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`MYLAN PHARMS. INC. EXHIBIT 1118 PAGE 5
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`

`

`Proceedings of a NATO Advanced Study Institute on
`Molecular Aspects of Monooxygenases and Bioactivation of
`Toxic CompOunds,
`held August 27-September 7, 1989,
`in Cesme (Izmir), Turkey
`
`Library of Congress Cataloging-in-Publication Data
`___—__—__—_-——————
`
`cu. -- (NATO ASI series. Series A. Life sciences
`
`v.
`
`NATO Advanced Study Institute on Molecular Aspects of Monooxgenases
`and Bioactivation of Tox1c Compounds (1989
`Cesne. Turkey)
`Molecular aspects of uonooxgenases and bioactivation of
`toxic
`compounds / edited by Enel Arinc. John B. Schenknan. and Ernest
`Hoogson.
`p.
`202)
`"Proceedings of a NATO Advanced Study Institute on Molecular
`Aspects of Monooxygenases and Bioactivation of Toxrc Coupounds, held
`August 27-Septelber 7, 1969 In Ces-e (Izmir). Turkey"--T.p. verso.
`"Published in cooperation with NATO Scientific AFfairs DlVlSlOn
`Includes bibliographical references and INDEA.
`ISBN 0-306-43823-2
`2. Xenobiotics--Metabolic
`l. Monooxygenases-—Congresses.
`detoxrcation--Congresses.
`3. Cytochrome P-450--Congresses.
`I. Arinc. E-el.
`II. Schenklan. John 8.
`III. Hodgson. Ernest, 1932-
`IV North Atlantic Treaty Organization. Scientific Affairs
`Division.
`V. Title. VI. Series.
`2. Oxygenases-
`[DNLM 1. Biotransfornation--congresses.
`--etabolisn--congresses.
`3. Xenobiotlcs--netabolisn--congresses.
`4. Xenobiotics--toxicIty-—congresses.
`DU 120 N2795e 1989]
`0P603.M65N37
`1989
`615.9--dc20
`DM.M/DLC
`for Library of Congress
`
`91-3008CIP
`
`
`© 1991 Plenum Press, New York
`A DiVI3ion of Plenum Publishing Corporation
`233 Spring Street, New York, NY. 10013
`
`All rights reserved
`
`No part of this book may be reproduced, stored in a retrieval system, or transmitted
`in any form or by any means, electronic, mechanical, photocopying, microfilming,
`recording, or otherwise, without written permission from the Publisher
`Printed in the United States of America
`
`MYLAN PHARMS. INC. EXHIBIT 1118 PAGE 6
`
`

`

`CONTENTS
`
`Monooxygenase
`
`An Overview
`
`•••
`
`(EC 1.14.13.8)
`
`••••••
`
`P450-Dependent
`Cytochrome
`J. B. Schenkman
`Monooxygenase
`The Flavin-Containing
`E. Hodgson and P. E. Levi
`P450 : Comparison
`Multiple
`Forms of Rabbit Cytochrome
`of Chemical,
`Physical,
`Immunological
`and
`Biocatalytic
`Properties
`•••••••••••••••••• w ••••••••
`E. F. Johnson, T. Kronbach, A. S. Muerhoff,
`K. J. Griffin, U. R. Pendurthi and R. H. Tukey
`Primary Structures
`and Regulation
`of Cytochrome
`P450
`Isozymes 2 (lIB) and 5 (IVB) and the Flavin-
`Containing
`Monooxygenase
`in Rabbit Liver and
`Lung ••••••••••••••••••••••••••••••••••••••••••••••
`R. M. Philpot, R. Gasser and M. P. Lawton
`Insect Cytochrome
`P450 .•••••.••.•.••.•.••....••...•.••••
`E. Hodgson and R. Rose
`P450 : Elements
`I. Membrane Topology of Cytochromes
`and Measurement
`by Spectroscopic
`Techniques
`•••••••
`A. Stier, V. Krliger, T. Eisbein and S. A. E. Finch
`II. Membrane
`Topology of Cytochromes
`P450 : Oligomers
`and Cooperativity
`.•..•..•.....•..•...•.•.•..•.....
`A. Stier, V. Krliger, T. Eisbein and S. A. E. Finch
`NADPH-Dependent
`Cytochrome
`P450 Reductase
`•••••••••••••••
`A. Y. H. Lu
`Essential
`Features of NADH Dependent Cytochrome b5
`Reductase
`and Cytochrome
`b5 of Liver and Lung
`Microsomes
`E. Ar~ng
`b5 to Cytochrome
`from Cytochrome
`Electron Transfer
`P450
`••.•.•.•.•••.••.•..•.•.....•.•..•.•...•.••.••.
`C. Bonfils,
`J-L. Saldana, C. Balny and P. Maurel
`Functional
`Aspects of Protein-Protein
`Interactions
`of Cytochrome
`P450, Cytochrome
`b5 and
`Cytochrome
`P450 Reductase
`•••••••••••••••••••••••••
`J. B. Schenkman
`
`1
`
`11
`
`23
`
`55
`
`75
`
`93
`
`115
`
`135
`
`149
`
`171
`
`185
`
`vii
`
`MYLAN PHARMS. INC. EXHIBIT 1118 PAGE 7
`
`

`

`:
`
`199
`
`233
`
`by Phosphorylation
`Modification
`Post translational
`Control
`of Cytochrome
`P450 and Associated
`Enzymes
`•••••••••••••••••••••••••••••••••••••••••••
`W. pyerin and H. Taniguchi
`in
`Alterations
`Physiological
`and Pathophysiological
`Rat Hepatic Cytochrome
`P450 •••••••••••••••••••••••
`J. B. Schenkman,
`K. E. Thummel and L. V. Favreau
`Ontogenesis
`of Liver Cytochromes
`P450 •••••••••••••••••••
`255
`C. Bonfils,
`J. Combalbert,
`T. Pineau,
`C. Larroque,
`R. Lange and P. Maurel
`..................... 267
`Mechanism
`of Steroid Hormome Action
`A. Berkenstam
`and J-A Gustafsson
`Xenobiotic
`Regulation
`of Cytochrome
`P450 Gene
`Expression
`M. Gillner,
`J. Bergman and J-A Gustafsson
`Prostanoid
`Metabolism
`and Biologically
`Active
`Product Formation .................•...............
`D. Kupfer
`and
`P450 in the Anabolism
`Role of Cytochrome
`of Endobiotics
`•••••••••••••••••••••••••
`Catabolism
`H. Vanden Bossche,
`H. Moereels
`and P. A. J. Janssen
`Interactions
`of Estrogenic
`Pesticides
`with
`Cytochrome P45 0 •••••••••••••••••••••••••••••••••••
`D. Kupfer
`Metabolism
`on the P450-Dependent
`Effects
`of Inhibitors
`Compounds
`in Fungi, Protozoa,
`of Endogenous
`Plants and Vertebrates
`••••••••••••••••••••••••••••
`H. Vanden
`Bossche,
`P. Marichal
`G. Willensens
`and
`P. A. J. Janssen
`of Nitroimidozoles
`Activation
`Mechanism
`of Metabolic
`A. Y. H. Lu and P. G. wislocki
`Benzene Metabolism •...............•.....................
`R. Snyder and S. P. Chatterjee
`Mechanisms
`of Benzene Toxicity
`••••••••••••••••••••••••••
`S. P. Chatterjee
`and'R. Snyder
`Hematotoxicity,
`Leukemogenecity
`and Carcinogenecity
`of Chronic Exposure
`to Benzene
`••••••••••••••••••••
`M. Aksoy
`and Their Individual
`Isoenzymes
`Epoxide
`Hydrolase
`to the Control of Toxic
`Contribution
`Metabolites
`F. Oesch, L. Schladt,
`M. Knehr, J. Dohmer and
`H. Thomas
`
`•••• 365
`
`283
`
`293
`
`305
`
`331
`
`345
`
`375
`
`387
`
`415
`
`435
`
`viii
`
`MYLAN PHARMS. INC. EXHIBIT 1118 PAGE 8
`
`

`

`Basic and Recently Discovered
`Role of the Well-Known
`Acidic Glutathione
`S-Transferases
`in the
`Control of Genotoxic Metabolites
`••••••••••••••••••
`F. Oesch, I. Gath, T. Igarashi, H. Glatt and
`H. Thomas
`Characterisation
`transferases
`B. Burchell
`Molecular
`Cloning, Expression and Genetic Deficiencies
`of UDP-Glucuronosyltransferases
`•••••••••••••••••••
`B. Burchell
`Contributors
`Index ...................................................
`
`-
`
`and Regulation of UDP-Glucuronosyl-
`..•......•. '....••.•...•••••...••..•.••• 463
`
`447
`
`473
`
`489
`491
`
`ix
`
`MYLAN PHARMS. INC. EXHIBIT 1118 PAGE 9
`
`

`

`METABOLISM
`ON THE P450-DEPENDENT
`EFFECTS OF INHIBITORS
`COMPOUNDS IN FUNGI, PROTOZOA,
`PLANTS AND VERTEBRATES
`
`OF ENDOGENOUS
`
`Hugo Vanden Bossche, Patrick Marichal, Gustaaf Willensens
`and Paul A.J. Janssen
`Janssen Research Foundation
`B2340 Beerse, Belgium
`
`INTRODUCTION
`A great number of the present antifungal agents belong to the class
`of nitrogen heterocycle
`derivatives.
`Examples are the pyrimidine
`antifungals, triarimol
`, fenarimol and nuarimol, the pyridine derivative,
`buthiobate , the imidazoles,
`miconazole
`,clotrimazole
`, econazole,
`imazalil , tioconazole,
`bifonazole,
`sulconazole and ketoconazole
`and
`finally the triazole
`antifungals,
`azaconazole, propiconazole,
`terconazole, fluconazole,
`itraconazole and saperconazole.
`All these
`antifungal agents have been shown to inhibit ergosterol synthesis
`(the
`main sterol in most yeasts and fungi) by interacting with the cytochrome
`P450-dependent
`14a-demethylation
`(P45014DM) of lanosterol in e.g.
`Saccharomyces cerevisiae or of 24-methylenedihydrolanosterol
`in most
`fungal cells
`(for reviews see refs. 1-4).
`It is not surprising
`that nitrogen heterocycles affect cytochromes
`P450 (P450).
`Indeed in 1972, Wilkinson et al. (5) described a long list
`~f i~idazole derivatives
`as potent inhibitors of p450-dependent
`reactions
`~n l~ver microsomes.
`Each of the imidazoles investigated exhibited a
`type II difference
`spectrum with a peak at 430-431 nm and a trough at
`390-393 nm.
`This suggests that the unhindered nitrogen
`(N3 in the
`imidazole ring) binds to the catalytic heme iron atom at the site
`Occupied by the exchangeable
`sixth ligand (6).
`It is of great interest .that a number of the 14a-demethylase
`inhibitors
`(DMIs) listed above show much higher affinity for the fungal P45014DM than
`for P450 isozymes of the hosts (1).
`It is the aim of this paper to review the interaction, of some of
`~he above listed antifungals,
`with ergosterol synthesis in fungal cells
`,nd P450-dependent
`metabolic
`systems in the host.
`Compounds that
`~nterfere with P450 isozymes in steroid hormone biosynthesis, and plant
`growth regulators
`are also included.
`14a-DEMETHYLASE
`INHIBITORS
`Ragsdale and Sisler
`(7-9) were the first to prove that the
`~yrimidine derivative
`triarimol
`(Fig.1), inhibited ergosterol synthesis
`an U
`st~lago maydis, a fungal pathogen of maize (bl~ster smut.
`r~ar~mo
`"
`')
`T'
`,
`,
`~s effective in controlling
`powdery mildews.
`In triarimol-treated
`sPoridia of U. maydis reduced levels of ergosterol coincided with the
`accumulation
`of 24-methylenedihydrolanosterol,
`obtusifoliol and 14a-
`methyl-8,24 (28) ergosterol,
`indicating an inhibition of the 14a-
`demethylase
`(10).
`Studies of Kato et al. (reviewed in ref. 11) showed
`that the pyridyl derivative,
`buthiobate
`(Fig. 1), has a similar
`
`1
`
`and Bioactivation of Toxic Compounds
`~~olecular Aspects of Monooxygenases
`lied by E. Anne et al., Plenum Press, New York,
`
`345
`
`MYLAN PHARMS. INC. EXHIBIT 1118 PAGE 10
`
`

`

`Cl
`
`CLr\-C~
`
`\J;-~\d-
`
`N.......,N
`
`Triarimol
`
`CHO
`I
`NH rrr»;
`I
`I
`,
`HC-N
`\.--I
`I
`CCIa
`
`CHO
`I
`NH
`I
`N-CH
`I
`CCI3
`
`Triforine
`
`Buthiobate
`
`c)
`O'-b-O'
`-OCI
`
`-
`
`I
`
`1,#
`
`Clotrimazole
`
`c)
`I~
`
`CI
`
`bH¢2-CH_O~ICH2-< }CI
`
`,#
`CI
`Miconazole
`
`Fig. 1- Chemical
`
`structures
`
`Ketoconazole
`of some ergosterol
`
`biosynthesis
`
`inhibitors
`
`346
`
`MYLAN PHARMS. INC. EXHIBIT 1118 PAGE 11
`
`

`

`of
`
`N-
`
`that
`and Yoshida (12) proved
`Aoyama
`as triarimol.
`mode of action
`to P45014DM
`from Saccharomyces
`buthiobate
`specifically
`bound
`cerevisiae
`system
`and inhibited
`lanosterol
`14a-demethylation
`in a reconstituted
`from S.
`consisting
`of P45014DM
`and NADPH-P450
`reductase,
`both purified
`in the
`cerevisiae microsomes.
`The addition
`of buthiobate
`to P45014DM
`causing
`oxidized
`form caused
`a type II spectral
`change
`(12).
`Compounds,
`this kind of spectral
`changes,
`bind to the 6th coordination
`position
`of
`the heme iron.
`The spectral
`change
`was saturated
`when one mole of
`buthiobate
`was bound
`to one mole of P450,
`indicating
`that buthiobate
`formed ono-to-one
`complexes
`with oxidized
`P45014DM
`(12).
`Addition
`Na2S204
`to the buthiobate-P45014DM
`complex
`changed
`the absorption
`spectrum
`to that of a buthiobate-ferrous
`P45014DM
`complex;
`brief bubbling
`of carbon
`monoxide
`converted
`the buthiobate
`complex
`to the reduced
`-CO
`compound,
`showing
`maximum
`absorption
`at 447 nm
`(12).
`This suggests
`that
`the pyridine
`fungicide
`has lower affinity
`for the heme
`iron complex
`than
`CO.
`As shown by Wilkinson
`et al. (5, 13) the imidazole-liver
`P450 complex
`was also easily
`replaced
`by CO.
`However,
`the latter
`investigators
`used
`relatively
`small
`1-arylimidazoles.
`Therefore
`it is possible
`that these
`compounds
`bind
`only slightly
`to the apoprotein
`moiety
`of the cytochrome.
`Buthiobate
`is not inhibiting
`the ~22-desaturation
`of ergosta-S,7-
`dien-3B-ol,
`the last step in ergosterol
`synthesis
`(14).
`This hydrocarbon
`dehydrogenase
`requires
`NADPH
`and molecular
`oxygen,
`and is inhibited
`by CO
`and metyrapone.
`This
`indirect
`evidence
`suggests
`that the reaction
`is
`catalyzed
`by a P4S0
`(P45022-DS)
`(15).
`Further
`studies
`showed
`that the
`~22-desaturation
`is not blocked
`by rabbit
`antibodies
`against
`P45014DM,
`indicating
`that P45022-DS
`is different
`from P45014DM
`(15).
`of 7-
`Buthiobate
`only partially
`inhibited
`the O-deethylation
`ethoxycoumarin
`by rat liver microsomes
`and neither
`the benzphetamine
`demethylation
`nor the p-nitrosoanisole
`O-demethylation
`were inhibited
`(16). These
`studies
`certainly
`prove that buthiobate
`is a selective
`inhibitor
`of the 14a-demethy1ase.
`However,
`buthiobate
`is an almost
`equipotent
`inhibitor
`of the 14a-demethylases
`in both S. cerevisiae
`rat liver microsomes
`(16).
`is the piperazine
`inhibitor
`biosynthesis
`An interesting
`ergosterol
`differs
`from triarimol
`and
`Triforine
`derivative,
`triforine
`(Fig.1).
`buthiobate
`in having
`its heterocyclic
`nitrogen
`atoms
`substituted.
`Triforine
`inhibits
`ergosterol
`synthesis
`with concomitant
`accumulation
`14-methylated
`sterols,
`similar
`to those
`found after
`treatment
`of fungi
`with triarimol
`(17).
`Triarimol-resistant
`mutants
`of Cladosporium
`showed
`cross
`resistance
`to triforine.
`(11).
`However,
`Cucumerinum
`r14Cj-mevalonate
`triforine
`did not block
`the synthesis
`of ergosterol
`from
`(18).
`This suggests
`that in
`in a cell-free
`system
`of S. cerevisiae
`An other
`intact
`cells
`triforine
`is metabolized
`to an active
`form.
`is that triforine
`is inactive
`possibility
`against
`the S. cerevisiae
`P45014DM,
`which
`uses lanosterol
`instead
`of 24-methylenedihydrolanosterol
`as substrate.
`As menti9ned
`before,
`24-methylenedihydrolanosterol
`is the
`substrate
`for P45014DM
`of most
`fungal cells.
`has improved
`antifungals
`The introduction
`of imidazole
`and triazole
`the treatment
`of plant
`pathogens
`and the imidazoles,
`miconazole
`(Fig.1)
`and clotrimazole
`(Fig. 1) ameliorated
`topical
`antifungal
`treatment.
`However
`topical
`treatment
`is often inconvenient
`and several
`forms of
`dermatomycosis
`and systemic
`mycoses
`are not controlled
`by conventional
`drug therapy.
`Therefore
`the introduction
`of the orally
`active
`imidazole
`derivative,
`ketoconazole
`(Fig. 1), represented
`a major
`important
`advance
`in antifungal
`chemotherapy.
`As will be discussed
`further
`on,
`p-450
`ketoconazole
`was also of great
`help in the study of cytochrome
`isozymes.
`in U. avenae by the triazole
`The inhibition
`of ergosterol
`synthesis
`fungicide,
`triadimefon
`(19) together
`with the effect
`of triarimol
`(20)
`biosynthesis
`in rat liver led
`and N-dodecylimidazole
`(21) on cholesterol
`
`and
`
`of
`
`347
`
`MYLAN PHARMS. INC. EXHIBIT 1118 PAGE 12
`
`

`

`Matolscy et al. (22) to propose sterol biosynthesis as a potential target
`for antifungal action of the triazole antifungals.
`Ergosterol synthesis is not only inhibited by the pyrimidine,
`pyridine and triazole antifungals of use in plant protection, also
`imidazole derivatives, active against a long list of yeasts and fungi,
`pathogenic to plants, animals or man, have been found to interfere with
`ergosterol synthesis and specially with P45014DM.
`Examples are
`clotrimazole
`(23), N-dodecyl-imidazole
`(24), econazole (23), imazalil
`(Fig. 1) (25), ketoconazole
`(26). miconazole
`(27), parconazole (28),
`tioconazole (23), all imidazole derivatives.
`Examples of triazole
`derivatives are etaconazole (29), propiconazole(30),
`terconazole (31)
`and fluconazole (32).
`As expected from the studies of Wilkinson et al. (5), all these
`azoles have been found to yield type II spectra and/or to compete with
`carbon monoxide for binding to the sixth coordination position of the
`reduced heme iron in P450(s) present in yeast or fungal microsomes.
`Examples are the azole agricultural fungicides, azaconazole, penconazole,
`propiconazole and imazalil (4) and the medicinal azole antifungals,
`miconazole, clotrimazole, bifonazole, ketoconazole
`(4), parconazole and
`terconazole (25).
`Using a purified preparation of S. cerevisiae P450l4DM, Yoshida and
`Aoyama (33) proved that ketoconazole, as l-methylimidazole, interacted
`with the heme iron of P450l4DM at the sixth coordination position.
`Titration of P450l4DM with ketoconazole indicated the stoiChiometric
`binding of the fungicide to this P450 with very high affinity.
`upon
`addition of hydrosulfite, the ketoconazole-P450l4DM
`complex was reduced
`to the corresponding ferrous complex.
`Addition of co to the reduced
`complex showed a slow replacement of ketoconazole by co (32). Similar
`results were obtained by using microsomal preparations of Candida
`albicans (34). Furthermore, this reactivity of the reduced azole-
`P45014DM complex was not affected by replacing the imidazole moiety in
`ketoconazole by a triazole ring (34).
`The low reactivity of the ketoconazole-P45014DM
`complex with CO and
`the fact that the imidazole can be replaced by a triazole moiety,
`indicate that ketoconazole not only binds to the heme iron, but, that the
`large N-l substituent of ketoconazole also binds to the apoprotein moeity
`and that the composition of this non-ligand part determines the
`interaction with the apoprotein.
`Indeed, this interaction was much less
`with the much smaller buthiobate molecule and the I-methylimidazole-
`P45014DM complex was promptly converted to the reduced CO-complex (33).
`It is obvious that compounds that bind simultaneously to hydrophobic
`domains of the protein and to the heme iron are more active than those
`that bind to the iron atom only.
`This is illustrated by the fact that
`imidazole (binding to the 6th coordination position of the heme iron
`only) is a weak inhibitor of the P450-dependent aldrin epoxidation in rat
`liver microsomes (IC50-value=3.6mM), whereas phenylimidazole is a much
`more potent inhibitor (IC50-value= 1.5 ~) (35).
`Yoshida and Aoyama also proved that ketoconazole inhibited
`lanosterol 14a-demethylase activity of a reconstituted system consisting
`of P450l4DM and NADPH-P450 reductase, purified from S. cerevisiae
`microsomes (2, 33).
`The inhibition was linearly dependent on the amount
`of ketoconazole and reached 100% when an equal amount of ketoconazole to
`P45014DM was added.
`This further proves that ketoconazole inactivates
`the 14a-demethylase system by forming a stoichiometric complex with
`P45014DM.
`That azole antifungals are extremely potent inhibitors of the
`14a-demethylase system in yeasts and fungi can also be deduced from its
`effects on ergosterol synthesis by intact cells.
`For example, when
`ketoconazole was added to exponentially growing Candida albicans or
`Aspergillus fumigatus, 50% inhibition of ergosterol synthesis was reached
`after one hour of contact with 4 nM and 58 nM, respectively (36). With
`the topically active imidazole derivative, miconazole, 50% inhibition of
`ergosterol synthesis, by exponentially growing C. albicans, was already
`reached at 0.7 nM (27).
`
`348
`
`MYLAN PHARMS. INC. EXHIBIT 1118 PAGE 13
`
`

`

`Selectivity
`with P450 isozymes
`could interfere
`antifungals
`applied
`Topically
`clotrimazole
`has been shown to inhibit
`For example,
`present
`in the skin.
`hydroxylase
`the P450-dependent
`aryl hydrocarbon
`(AHR) activity in human
`source of human epithelial
`tissue
`hair follicles,
`a readily
`available
`(37).
`Fifty per cent inhibition
`(IC50-value) was achieved at about 1 ~.
`Topically
`applied
`clotrimazole
`also inhibited AHH activity
`in epidermal
`microsomes
`prepared
`from neonatal
`rats pretreated
`with solvent
`(acetone),
`coal tar, aroclor
`or 3-methylcholanthrene
`(38).
`The IC50-values
`were
`0.12, 0.16, 0.26 and 0.24 ~,
`respectively
`(38).
`Clotrimazole
`was also
`found to be in vitro an inhibitor
`of epoxide hydrolase
`activity
`in rat
`epidermal
`microsomes,
`with a 50% inhibition
`at 0.1 roM (38).
`Furthermore,
`topical
`application
`of clotrimazole
`to the skin of Balb/c mice
`substantially
`increased
`the latent period for the develpoment
`of skin
`tumors by 3-methylcholanthrene
`(38).
`Miconazole
`and ketoconazole
`inhibit
`(IC50-values
`are 10 ~
`and 0.65 ~,
`respectively)
`the p450-dependent
`metabolism
`of retinoic
`acid in epidermal microsomes
`from neonatal
`rats
`(39) .
`Topical
`application
`of ketoconazole,
`at doses of 1, 5 and 10 mg/kg,
`on neonatal
`Wistar rats, 1h before application
`of retinoic acid (1
`mg/rat)
`results
`in a dose-dependent
`inhibition
`of retinoic acid
`metabolism
`by epidermal
`microsomes
`isolated 24h later
`(39).
`Topical
`administration
`of ketoconazole
`to the scalp of human volunteers
`decreased
`in some of them the P450-dependent
`7-ethoxyresorufin-O-deethy1ase
`activity
`in human hair roots
`(40).
`However,
`following
`daily oral
`administration
`of 200 mg ketoconazole
`(5 days), a substantial
`decrease
`(from 2.73±0.71
`to 0.7l±0.26
`pmol resorufin/30min/20
`human hair roots)
`Occurred
`(40).
`These results indicate that some azole antifungals
`might
`be useful
`in inhibiting
`P450-dependent
`reactions
`in the skin that are
`able to transform
`harmless
`compounds
`into carcinogens.
`These results
`also focus attention
`on the fact that orally active antifungal
`agents
`whose activity
`is baised on interaction
`with the P450-dependent
`14a-
`demethylation,
`should be tested for their effects on mammalian
`and plant
`P450 isozymes.
`It is obvious that the first candidate to be tested is the P45014DM
`involved
`in cholesterol
`synthesis.
`To obtain 50% inhibition
`of the 14a-
`demethylation
`of lanosterol
`in phytohemagglutinin
`(PHA) stimulated
`human
`10-7 M of ketoconazole
`peripheral
`lymphocytes,
`is needed
`(3).
`When
`macrophages
`(J774G8) were incubated
`for 48h in the presence
`of [14C]_
`acetate
`and ketoconazole,
`50% inhibition
`of the incorporation
`of l4C into
`cholesterol
`was obtained
`at 1.5 ~
`(41).
`Fifty % inhibition
`of chole~
`sterol
`synthesis
`in subcellular
`fractions of male rat liver is reached at
`2 ~
`ketoconazole
`and 6 ~
`miconazole
`(42).
`It should be noted that 50 %
`inhibition
`of ergosterol
`synthesis by a subcellular
`fraction of C.
`was observed
`at 0.07 ~
`and 0.09 ~
`(42) of ketoconazole
`and
`albicans
`miconazole,
`respectively.
`Ergosterol
`synthesis
`inhibition
`in macro-
`infected
`with Leishmania
`phages
`amastigotes
`mexicana
`mexicana
`[Leishmania
`is known
`to synthesize
`ergosterol
`(43)] was achieved at 0.2 ~
`(41).
`As
`shown
`above, ketoconazole
`inhibits ergosterol
`synthesis
`in intact
`cells for 50% at 4nM, and complete depletion
`of ergosterol
`is
`C.albicans
`achieved
`at 7.5 nM (44).
`and colleagues, using the already mentioned
`reconstituted
`system
`Yoshida
`found
`that ketoconazole
`inhibited the 14a-demethylation
`of 24,25-
`dihydrolanosterol
`and of 32-hydroxy-24,25-dihydrolanostero1
`[i.e. the
`product
`of the hydroxylation
`of the C-32 methyl
`(14a-methyl group) of
`lanosterol]
`but the inhibitory
`effect on the removal of the 32-hydroxy-
`methyl
`group was weaker (45) . This suggests that in the yeast reconsti-
`tuted
`system,
`ketoconazole
`preferentially
`inhibits the hydroxylation
`step
`and not so much the oxidation
`of the C-32 alcohol to a C-32 aldehyde or
`the oxidative
`of the aldehyde as formic acid.
`Trzaskos et
`elimination
`al.
`(46) using hepaticmicrosomes,
`found that both miconazole
`and keto-
`conazole
`promote
`accumulation
`(the major oxysterol
`accumulating
`oxysterol
`
`349
`
`MYLAN PHARMS. INC. EXHIBIT 1118 PAGE 14
`
`

`

`3-HMG·CoA! HMG·CoA·reductase
`
`MEVALONATE
`
`feed-back
`Inhibitor
`
`-----HO
`
`Azores
`
`,C
`
`H3t
`
`HO
`
`HO
`
`Ergosterol
`Cholesterol
`Fig. 2- Inhibition by azole antifungals (Azoles) of ergosterol (yeast and
`fungi) and cholesterol (mammalian cells) synthesis.
`3-HMG-CoA= 3-
`hydroxy-3-methylglutaryl-coenzyme
`A.
`Dashed arrows=multi-enzyme systems.
`
`350
`
`MYLAN PHARMS. INC. EXHIBIT 1118 PAGE 15
`
`

`

`of lanosterol de-
`inhibition
`prior to complete
`was the C-32-aldehyde)
`Fifty % inhibition
`methylation.
`of lanosterol
`14a-demethylation
`was
`achieved at 0.9 and 0.4~
`miconazole
`and ketoconazole,
`respectively.
`These studies
`(46) indicate
`that, miconazole
`and ketoconazole
`at
`concentrations
`higher
`than those needed to inhibit
`lanosterol
`14a-
`demethylase
`in yeast,
`inhibit,
`the lyase activity
`(i.e. the last step in
`the 14-demethylation
`system)
`instead of the hydroxylation
`step in yeast
`(Fig.2).
`This suggests
`that P450s doing the same job in different
`species are not necessarily
`identical.
`However,
`Trzaskos and Henry(47),
`studying the effects
`of the triazole
`derivative,
`flusilazole,
`found that
`the affinity
`of this triazole
`for a partly purified
`P450 from S.
`micro somes is similar to that for a partly purified
`P450 from
`cerevisiae
`rat liver microsomes.
`However,
`when they compared
`the binding of
`flusilazole
`to P450(s)
`in the microsomes,
`the affinity
`for the yeast
`P450(s)
`was almost
`24-times
`higher.
`Studying the effect on the
`lanosterol
`14a-demethylation
`it was found that the hepatic microsomal
`preparation
`was almost
`100 times less sensitive
`than the yeast
`preparation
`(47).
`From these studies, Trzaskos
`and Henry conclude that
`the apparent
`increase
`in susceptibility
`of fungal preparations
`observed
`upon exposure
`to azole antifungals
`is due in part to a protective
`effect
`afforded
`by other susceptible
`P450 isozymes present
`in mammalian
`preparations.
`However,
`Trzaskos
`and Henry
`(47) used S. cerevisiae
`only.
`Although
`the P45014DM
`of both rat liver and S. cerevisiae
`might be quite
`similar
`it can not be excluded
`that P45014DM
`of other yeasts and fungi
`counterpart.
`As shown in the
`differ
`from the hepatic
`or S. cerevisiae
`chapter
`on "Role of cytochrome
`P-450 in the anabolism
`and catabolism
`of
`endobiotics"
`(this book) the P45014DM of S. cerevisiae
`shares with those
`and C. tropicalis
`64.2 and 65.2 identical
`aminoacids,
`of C. albicans
`whereas
`the P45014DM
`of both candidas
`share 83% identical
`amino acids.
`Furthermore,
`ketoconazole
`is a much more potent
`inhibitor
`of ergosterol
`synthesis
`by C. albicans
`than by S. cerevisiae,
`both grown for 24h in a
`casein hydrolysate-yeast
`extract-glucose
`medium
`(27).
`Fifty per cent
`inhibition
`was achieved
`at 2.1 nM and 330 nM, respectively
`(unpublished
`results) .
`STEROID
`SYNTHESIS
`with a broad spectrum
`imidazole
`is an oral antifungal
`Ketoconazole
`daily single dose of ketoconazole
`of antifungal
`activity.
`The effective
`The incidence
`of side effects
`is
`for most fungal
`infections
`is 200 mg.
`low. However,
`in 1981, gynecomastia
`was reported
`in two patients
`during
`treatment
`with 200mg ketoconazole
`daily
`(48) and in a few patients
`receiving
`high multiple
`doses
`(600-1200 mg/day)
`of the antifungal
`(49).
`The observation
`of De Felice et al.(48) triggered
`a multidisciplinary
`study of the endocrinological
`applications
`of ketoconazole
`and was at the
`onset of in-depth
`studies
`on mammalian
`P450 isozymes.
`Indeed, this rare
`side effect
`suggested
`that in such patients
`ketoconazole
`affected the
`estrogen:
`androgen
`ratio
`(49).
`No clear reduction
`in the plasma
`estradiol
`levels at 600 mg ketoconazole
`per day was seen (49).
`Measuring
`the testosterone
`serum levels, a dose related reversible
`decrease
`was
`observed
`(49-56).
`The finding
`of a marked but transient
`decrease
`in plasma testosterone
`levels
`was the start for a series of studies to determine
`the site of
`action
`of ketoconazole
`in the androgen biosynthetic
`pathway.
`Testosterone
`synthesis
`was studied in a rat testicular
`subcellular
`fraction
`(SI0-fraction)
`containing
`the, cytosol and microsomes
`(57-59).
`with pregnenolone
`as substrate,
`a 50% inhibition
`of androgen
`synthesis
`was achieved
`after a 3 h incubation
`period in the presence
`~ketoconazole
`(58). This inhibition
`coincided
`with ,an accumulation
`17a-hydroxy,20-dihydropregnenolone
`(Fig.3).
`Maximum
`accumulation
`was
`
`of 5
`of
`
`351
`
`MYLAN PHARMS. INC. EXHIBIT 1118 PAGE 16
`
`

`

`HO
`
`Pregnenolone
`
`o
`
`Progesterone
`
`P45017a
`Hydroxylase
`
`HO
`17a-Hydroxypreg neno lone
`
`o
`17a-Hydroxyprogesterone
`
`0
`HO
`17a-Hyd roxy-20-d Ihydropregn enolone 17a-Hydroxy.20-dl hydroprogesterone
`
`Lyase
`
`P45017a ~
`
`0
`
`P45017a
`
`0
`
`o
`
`OH
`
`Androstenedione
`
`HO
`
`DHEA
`
`HO
`
`Androstenedlol
`Testosterone
`Fig. 3- The synthesis of androgens from pregnenolone and progesterone.
`P45017a= 17a-hydroxylase/17,20-lyase.
`DHEA= dehydroepiandrosterone.
`
`o
`
`an accumulation of pregnenolone
`At concentrations >1~
`reached at 0.5~.
`was observed with a concomitant decrease in 17a-hydroxy,20-dihydropreg-
`nenolone (58). Further studies revealed that ketoconazole inhibited the
`conversion of 17a-hydroxy,20-dihydroprogesterone
`into androstenedione by
`rat testicular microsomes, 50% inhibition was achieved at 0.2 ~
`(57,
`59).
`These studies prove that ketoconazole is an inhibitor of the 17,20-
`lyase.
`
`352
`
`MYLAN PHARMS. INC. EXHIBIT 1118 PAGE 17
`
`

`

`testes from
`decapsulated
`using minced
`et al.(60),
`Studies by Rajfer
`Sprague-Dawley
`rats, indicated
`that the ketoconazole
`induced inhibition
`of androgen
`synthesis
`originated
`from an inhibitory
`effect on the 17,20-
`lyase only (60). Similar
`results were reported by Kan et al.(61). Higashi
`et al. (62) showed that ketoconazole
`inhibited
`the activities
`of steroid
`17a-hydroxylase
`and 17,20-lyase
`in rat and human testis,
`in human testis
`the investigators
`also found inhibition
`of the 16a-hydroxylation
`of
`progesterone.
`In rat testis the 17,20-lyase
`was almost 4-times more
`sensitive
`to ketoconazole
`than the 17a-hydroxylase
`(62).
`This difference
`in sensitivity
`is of interest
`since it has been
`shown that the microsomal
`17-hydroxylase
`and 17,20-lyase
`activities
`result from the