`
`
`
`

`
`
`
`
`

`
`
`
`
`
`

`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`ew antiepileptic agents
`
`{Harold Kohn and Judith o. Conley
`
`is
`times as the ‘falling sickness‘.
`_ Epilepsy, known since ancient
`- characterised by convulsive seizures and momentary lapses of awareness
`.. or body function. The generic term cornesfrom the Greekfpiiepsia which
`means ‘to take hold of or seize’. Recent research suggeststhat 2 m people
`in the US and 500000 people in this country suffer with epilepsy. But,
`despite this, there has been little in the way of new drugs over the past
`decade to help epileptics lead a more normal life. This situation is now
`changing. The shortcomings of conventional drug therapy have spurred
`chemists to seek drugs that are safer, more potent and more effective than
`the existing medication. Functionalised amino acids are the latest in a
`series of potent new agents for the treatment of epilepsy.
`
`and phenobarbital ll‘ }—were discovered
`by Locock in 1857 and by Hauptmann in
`1912 respectively, by serendipity.
`The situation changed in ‘[926 with
`the discovery of the convulsive action of
`pentylenetetrazole and then in 1937
`Putman and Merrittdeveloped an eiectro-
`shock model for epilepsy whereby they
`screened around 70 compounds against
`electrically induced convulsions in cats.
`As a result of
`their work the anti-
`convulsant
`activity
`of
`5,5-diphenyI~
`hydantoin (phenytoin, Dilantinl [21 was
`established}? Phenytoin is still the most
`widely used anticonvulsant despite its
`serious side effects. In ‘I948 Goodrnann
`and his coworkers standardised the
`maximal electroshock seizure (MES) test
`and later introduced the subcutaneous
`pentylenetetrazole (Melrazo|l
`lsc Met}
`seizure threshold test.
`In the MES seizure test, animals are
`stimulated by using an alternating
`current applied through corneal elec-
`trodes for a short duration. Drugs with
`markedactivity bythistestarethoughtto
`prevent seizure spread and are likely to
`be effective in grandrnalseizures. The sc
`Met seizure test measures the ability of
`the anticonvulsant drug to protect against
`seizures induced by a subcutaneous
`injection of pentylenetetrazole. The dose
`used is the amount ofconvulsant required
`to cause seizures in 97 per cent of the
`animals
`tested. Drugs with marked
`activitybythistestarethoughttoelevate
`the seizure threshold and are likelyto be
`effective against petrt mar‘ seizures.‘
`These two tests are the most useful
`laboratory testsforscreening large num-
`bers of chemical compounds. In recent
`years, additional models for epileptic
`seizures have been advanced. These
`include inducing seizures by auditory
`stimulation,
`photostimulation,
`hyper-
`thermia, or
`introducing irritant sub-
`
`Epilepsy was recognised as a unique and
`terrible affliction as far back as the
`Babylonian times. Full clinical descrip-
`tions were first given around 4008C in
`the Hippocratic monograph On the sacred
`_ disease and later in the New Testament
`l {Mark 9:37). In the 19th century, major
`} and minor seizures became known as
`3 grand me! and petrr mar‘ respectively.‘
`3 The signs and symptoms depend on the
`1 motor, sensory autonomic and mental
`p functions ofthose regionsinthe brainin
`x which a neuronal discharge arises or to
`fl which it spreads.
`if the discharge is
`it
`violent, prolonged and ubiquitous, the
`maximal seizure of grand ma! develops
`characterised by a sudden fall with a
`tonic spasm {rigidity and stiffening of the
`_ bodylfollowed bycionic spasms [general-
`:
`. isedjerkinglwith the victim's skin some-
`_
`'3 times becoming blue. lf the discharge is
`5 limitedinstrength,varioussortsofrninor
`nu seizures occur. An essential feature of
`M grandrnalisthe abnormal ease by which
`:2; neuronal discharges spread from the
`at origin of excessive discharge to other
`4 areas of the brain. Perir mall is restricted
`
`1?til
`it
`
`I 9
`
`ei_I_ to brief, frequent attacks l5~‘l0Oper clay}
`3%‘. of
`impaired consciousness associated
`5: with staring and eyelid movements, and
`lOCC3SlDI"'|a”Y.
`loss of posture and arm
`fiqiajerks. No specific cause is known forpetft
`lime! and this disorder occurs most
`‘iiicommonly before puberty?
`
`S’aExperimenta| models
`gr.-r=ln the past, drug research was hindered
`5?‘g_by the lack of experimental models for
`Srgepileptic seizures. Not surprisingly, there-
`fore, the early history of treatment is
`mgmaved with failure. In fact some of the
`remedies tried, for example ashes of
`lviifasses‘ hooves,
`storl<‘s dung and the
`7”".-varm blood of a gladiator, probably made
`flygaatients Suffer more. The first anti-
`Hatonvulsant drugs—potassiurn bromide
`-CHEMISTRY IN BRITAIN MARCII 1983
`.n.‘-*-
`
`Development of antiepileptic agents
`With the discovery of new laboratory
`procedures to screen anticonvulsant
`compounds, an intense era of anti-
`epileptic drug development was initiated
`during the 1940s and 19509. Thousands
`of candidate agents were evaluated and
`a cluster of new antiepileptic drugs were
`introduced—-—two hydantoins lmepheny-
`toin {3} and ethotoin {4}}, a barbiturate
`lmetharbital i511, and a deoxybarbiturate
`{primidone {6}} were developed and
`marketed for the treatment of grandma!
`seizures and two oxazolinediones {para-
`rnethadione {7} and trimethadione {8}}
`were introduced for the control of pen"!
`ma! seizures? Similarly, several phenyl-
`succinimides [9] were found to prevent
`pentylenetetrazole-induced seizures and
`control peril ma! seizures.‘
`Progress in antiepilepticdrug research
`slowed down in the early 1950s. By this
`time it was reaiised that most of the
`drugs in use contained a modified ureide
`moietyl101ernbeddedwithintheirchemi-
`cal framework. This structural theme had
`been extensively developed, prompting
`some researchersto suggestthatfurther
`elaboration would probably not lead to an
`improved drug. Moreover, the search for
`new antiepileptic agents had failed to
`produce significant numbers ofnew lead
`compounds possessing novel structures.
`in the late 1960s research in anti-
`convuisant drug developmentwas stimu-
`lated by the creation of the Epilepsy
`Branch and the Epilepsy Advisory Com-
`mittee within the United States National
`
`Institute of Neurological and Communi-
`cative Disorders and Stroke lNINCDSl.
`Programmes were established to collate
`and review the neuroscience literature
`pertinent
`to epilepsy.
`to support con-
`trolled laboratory and clinical trials of
`drugs which needed proof of efficacy for
`marketing approval, and to screen large
`numbers of potentially new antican-
`vulsant
`agents. These programmes
`helped pave the way for the eventual
`introduction of three drugs. containing a
`novel
`structural moiety,
`for
`seizure
`management
`in the US. They were
`carbamazepine (Ill, an iminostiibene;
`clonazepam {I2}, a benzodiazepine; and
`vaiproic acid {I3}, a fatty acid. Both
`valproic acid and carbamazepine were
`already in use in Europe. Another benze-
`231
`
`stances to the experimental anirnalsfi
`
`|PR2014-01126-1019, p. 1
`
`VENNOOT, SANDOZ, SUN
`
`ACTAVIS, AMNEAL,
`AUROBINDO,
`BRECKENRIDGE,
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`

`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`

`
`
`\. Ea'r_ly_fa'Itticon.vulsantdr1.tgs.
`
`:
`
`diazepine. clorazepate dipotassium (14).
`was also approved as an adjunctive drug
`for the treatment of epilepsy.’
`To date the most widely used anti-
`convulsants are phenytoin {Z}. pheno-
`barbital {I}, primidone {6} and carba-
`rnazepinelf 1}. However, they all promote
`adverse side-effects such as drowsiness.
`dizziness, nausea. swelling ol the gums
`and liverdamage. Some search began in
`the late 1970s for new drugs that are
`safer, more potent and more widely
`effective than the existing medications.
`As a result, many new chemical classes
`have been identified that possess anti-
`convulsant activity but are less toxic and
`theretore potentially safer than those
`currently in use. Notable examples”
`include
`2,3:4-,5-bis-0-(1-methyi~ethyl-
`ide ne)-,6—o-fructopyranose [15 l, 3-[3-(tri-
`fluoromethy|)phenoxy]-1—azetidinecarbox-
`amide
`{T6}.
`10,11-dihydro~5-rnethyI-
`5H-dibenzo[a,d]cycloheptene-5.1 0-imine
`ll’ 7], N-(2.6-dimethy|phenyll-p—amino-
`benzamide {I8} and more
`recently
`functionalised amino acid derivatives
`{I9}.
`
`Amino acids
`In the past amino acids and their
`derivatives were not considered as
`potential antiepileptic agents. probably
`because these polar compounds do not
`readily
`penetrate
`the
`blood—brain
`barrie r.‘° Despite this, several amino acid
`derivatives have recently been shown to
`be effective in preventing seizure. These
`include derivatives of alicyclic and aro-
`matic amino acids," phosphono deriva-
`tives of aliphatic amino acids,” N-
`ben2oyl-
`and N-phenylacetylglycine
`amides.“ and structural analogues of
`the inhibitory neurotransmitter, y-amino-
`butyric acid (GABA}.“‘ The endogenous
`neuropeptides. Met- and Leu-enkephalin,
`have
`also
`exhibited
`anticonvulsant
`activity in a variety of test animals and
`may play an important
`rate in the
`prevention of a static convulsive state or
`in the maintenance of normal brain
`function.“
`.
`.
`Our investigation of chemotherapeutic
`agents possessing CNS depressant and
`anticonvulsant
`activity suggested a
`common structural motif. Three lunc-
`tionalities were prevalent
`in many of
`these compounds:
`_
`I a vicinal diarnine linkage;
`0 an oxygen atom on the ethene chain
`bridging the two amino groups; and
`0 an aromatic ring one carbon removed
`from an amino residue."
`This empirical blueprint suggested to
`' us that tunctionalised amino acids and
`_ peptides U9} could provide a rich source
`of future arttiepileptic agents and this in
`fact led to our initial-discovery that N-
`acetyl~o.L—alanine-N-benzylamide . {Z0}
`. was an anticonvulsant
`in mice." ._To
`_ elucidate the scope of the anticonvulsant
`_j activity of (20), we did systematic struc—.
`tural variations. initially; at three sites in
`I19): the-ct"-mrhon [Fl1(R3}}.'-the_ amide
`-_ -substituent - {fit}, and the-' N-acyt group '
`_ {W}. in all cases, where appropriate. the
`-. .,°-'-‘-'.3°."’-"'."'3.“*$ .=.Wl‘-‘f9 5Y|‘|_1h35l$9_C_|.' -The; "
`'
`.132 2
`
`initial pharmacologicalstudieswere done
`' on mice through the Epilepsy Branch of
`the NJNCDS and later at the Eli Lilly
`Research Laboratories.
`-
`
`.
`
`aromatic rings. both ot which were one
`carbon removed from an amino residue.“
`We then went on to show that com-
`pounds (20-22) were comparable to
`phenobarbital {1} in the prevention 07
`electroshock-induced seizures in rnit-‘E
`_ and perhaps more sig niiica ntly were less
`toxic after injection and oral adminis-
`tration than phenytoin or phenobarbital.
`Moreover. these compounds displayed
`significantly different activity profiles
`compared to the conventional
`aflll‘
`epileptic agents when tested a93l"'51
`several chemical convulsants. r'e peflill‘
`enetetrazote, bicuculline, picrotoxin, and
`- strychnine, suggesting that these com-
`‘ pounds represented. a new irnputtani
`class of antioonvulsant agents.”
`-The activity at our functionalised amim '
`acid racemates coupled with the legal?"
`aw bi0l°9ica|_.si=ecifi=_:itY .07 mi"?
`p.2
` ' "' _*=='*.|'_=—,_'_~tI.S'1:”I'-"i'.'I1_~t. anrr»_t_I.N.MAP?.¢H 1”” '
`
`.
`
`.
`
`/
`
`
`
`-
`
`Our results for . analogues of (20)
`revealed several significant factors‘
`_
`I The principal biological activity of
`these compounds resided in their ability
`to prevent seizures in the MES test.
`I Stringent steric and electronic requi're— .
`mentsexistedinttslatboththea-carbon
`[Fl’lR3,l] and the amide substituents {R*l _
`for maximal activity.
`-
`. o I-lomologation of the at-carbon by as
`carbon atom to generate a 1.3-diamine
`linkage led to reduced CNS activity.
`- _. I Pronounced activity was observed for
`'
`7 N-acetyl-o,L»alanine-N—m—fiuorobenzyl-_-
`amide 121} and N-acetvt-_o.L-phenyI—- ..
`‘glycine-_N-benzylarnidel22} in addition to _
`_-
`-.
`{go}, of ngotegcmpaund{22} containstwo_ _;.:~
`"
`'
`"
`I"
`'
`"IPR2014-O1126- Exhibit 1019,
`
`
`
`
`
`
`
`
`
`!
`
`"
`
`#
`
`$
`
`!
`
`"
`
`"
`
`
`
`%
`
`$
`
`&
`
`'
`
`(
`
`)
`
`*
`
`)
`
`+
`
`"
`
`!
`
`"
`
`,
`
`
`
`

`
`
`
`
`
`E5-7500 Kan
`590- Rep. e.c?r?'fi2‘?1J
`S
`Telex: 1 772132303
`leading manufactu
`
`
`_
`re
`andan eXpe"e”C9dDarttner
`
`Pharmaceur 3;
`
`SynthesisIntgrmgggtggunds
`CUSiOm S t
`~
`Vn heels and Development
`
`
`
`__'._f_I-u0¢_o_‘
`
`n
`
`"-‘-“"''..’.ef_-'-_“n'a'n'.a'o'-'.’o‘.'..'
`
`Acetylenedicarboxylic acid salts and esters
`
`Adenine-9-L3-D-Arabinofuranoside (Vidarabine)
`
`2-Amino-6-Chloropurine
`
`5-Bromo-2’-deoxyuridine [Broxuridine)
`
`Calcium Folinate (Leucovorin calcium), pure -
`
`Dacarbazine USP 21
`
`'
`
`2-Deoxycytidine
`
`2-Deoxy-d-ribose
`
`2-Deoxyuridine
`
`5-Fluorocyto-sine (Flucytosine) USP 21
`
`5-Fluoro-2’-Deoxyuridine (Floxuridine) USP 21
`
`5-Iodo-2’-Deoxycytidine
`
`5-Iodo-2’-Deoxyuridine (ldoxuridine) USP 21
`
`Methotrexate USP 21
`
`Thioacetic acid -
`
`B-Thymidine
`
`Trmuorothymidine
`
`Protected amino acids.
`
`
`
`
`
`
`
`
`
`!
`
`"
`
`#
`
`$
`
`!
`
`"
`
`"
`
`
`
`%
`
`$
`
`&
`
`'
`
`(
`
`)
`
`*
`
`)
`
`+
`
`"
`
`!
`
`"
`
`,
`
`-
`
`.
`
`/
`
`0
`
`

`
`'-Promisi.I_1g
`'a_n_ti_epileptic'drugcandidate?»-
`‘ .cH,oso',i_1
`
`Acknowledgements‘ We are gratetul to
`the Anticonvulsant Screening Project of
`the National Instiluteof Neurological and
`Communicative Disorders and Stroke
`ININCDS} and the Eli Lilly ‘Research
`Laboratories for kindly performing the
`pharmacological studies. We also thank
`Drs D. Robertson and D. Leander {Lilly}
`and J. Stables and H. Kupferberg
`{NlNCDS) for their comments.
`
`-
`I
`
`Harold Kohn is professor of chemistry in
`the department of chemr'stry. University
`of Houston, Houston. Texas 77004.
`Judith D. Conley is a researcher in the
`same department.
`
`
`
`
`._.——.—£‘:.—"T—u.-v-'.2;‘....-.—lC
`
`' i
`
`i
`
`'
`
`"i
`
`1 tr‘?! -
`
`acidlalntie lileptiedrugn
`
`1
`
`"
`
`
`
`
`
`1
`
`'
`
`5
`
`_
`
`tiocrl'tj'1a.-
`_ rrtnectsvs'irioexota'drugis'tlie
`-_£Ioseneededtoobseneto:ricmanife=rt:rrt'ionsi1't5u '-
`percent of the animals sr.-reertedvs the dose '
`equlrodtooroter:t50peroentotdreanirnaistested' .-
`
`.
`
`
`References
`1. B. J. Wilder. and J. Bruni, Seizure
`disorders.‘ a pharmacologicalapproach to
`treatment. NowYork: Haven. 1981.
`2. A. Spinks and W. S. Waring. Prog. Med.
`Chem., 1963. 3, 261.
`3. D. M. Woodbury, J. K. Penry and C. E.
`Pippenger, Anti}:-pHep1r'c drugs. 2nd Erin.
`New York: Raven, 1982.
`4. W.
`(J. Foye. Principles of medI'ci'nal
`chemistry. Philadelphia: Lea and Febiger.
`1981.
`5. D. P. Purpura er al. Experirnentalmodels
`of epr'i'epsy—-a 'manual for the laboratory
`worker. New York: Raven, 1972.
`G. Chen and R, Portman, J. Pharmacol.
`Exp. Ther., 1951, 103. 54.
`Ft. J. Porter et all Cleveland C!r'n. 0..
`1 984, 51 , 293.
`Ft. Dagani, Chem. Eng. News. 1986. 54.
`23.
`£lI.2l;.9C|ark eral, J Med Chernt. 1985, 23.
`10. P. S. Callery at at‘. J. Neurochem.. 1932.
`38,1063. -
`based substrates prompted us to examine
`11. A. M. Crider et aL J. Pharm. Scr'..1934-
`73, 1612; A. J. Belt: and A. A. Larson.
`whether the observed activity resided in
`Eur. J. Pharmacai, 1935. 114, 181. U.
`a single enantiomer. Surprisingly. pre-
`Ere: or an‘, Eur. J. Pharmacol'., 1985, 1 10.
`31 .
`vious pharmacological differentiation of
`12. M. J. Croucher. J. E. Collins and B. S.
`enantiomeric antiepileptic agents had
`Meldrum. Science, 1 982. 21 6, 899; LA.
`proved to be largely unsuccessful. Most
`Cates et at J. Pharm. Sci, 1984, 73.
`currently used drugs are not chiral, eg
`1550.
`Conclusions
`phenytoin {2}, valproic acid {13} and
`13. T. Takahashi erai. Swr'sspatent393355.
`phenobarbital {I l. But in those instances
`October 30, 1965; D. E. Thorrte, Us
`The pharmacological profiles exhibited
`paterrt3657341', April 13, 1972.
`‘_
`by functionalised oi.-amino acid deriva-
`where a single chiral centre exists,
`14. P. Krogsgaard-Larsen. J. Scheel-Kruger
`tives estahlishes that this class of com-
`. anticonvulsant
`activity
`is
`typically
`and H. Kofod, GABA-neurorransmmers.
`observed for both stereoisorners. with
`pounds is worthy of further detailed
`pharmacochemical.
`biochemical.
`and
`one of the two enantiorners exhibiting
`inspection. The specific activities of
`pharmacological aspects. New York:
`Academic, 1979; S. J. Enna. Biachent
`these compounds in the MES, sc Met.
`only marginally enhanced activity. For
`Pharmacol,
`1981." 30, 907;
`J.
`P-
`example. Nirvanol
`(23) displays the
`- and toxicity tests can be independently
`Chambon er at Arzneim. -Forsi:h., 1984.
`largest pharmacological differentiation
`modulated by altering the substitution
`34.1017.
`_
`15. F. C. Tortella and A. Cowan. Life Sci-
`in activity in animal studies for its two
`pattern at the at-carbon atom, the N—acyI,
`1982.31,2225.
`'
`' enantiomers. The {R}-stereoisomer is 3.8
`and the N-amido moieties. The pharma-
`- 16. Other models have been proposed. F0‘
`times more potent than the {S}-isomer
`cological evaluation of the individual
`a comprehensive discussion as ml‘
`enantiomersof[20}andl22lshowedthat
`_ against seizures induced by electroshock‘
`as
`review, see: A. Carnerman and
`in mice.” In other cases, enantiomeric
`N. Cartterrnan in Antfepfleptfc drt-lg‘-3’
`the anticortvulsant
`activity observed
`_ mechanism of action; G. H. Glaser Bf 3’
`discrimination is considerably less.”
`resided primarily in the o-stereoisomers
`(eds). p223. New York: Haven. 19393
`However. in our most potent amino
`and represents the greatest pharma-
`M. G. Wong. J- A- Define and P. 4-
`_ acid derivatives. I20} and B2}. we found
`'
`.
`cological stereochemical differentiation -.
`Andrews. J. Med. Chem., 1 986, 29. 562-
`' 17. S. Cortes er al, J. Med. Chem, 1985. 23-
`reported to date among antiepileptic
`_ that the o-stereoisomers were over to
`601.
`times more effective in the MES test than
`agents possessing a single chiral centre.
`-- 18. .J. D-Conle-{and H. Kohrt, J. Med. Chem-
`the corresponding L—enantiorners when
`These observations may provide the first '
`1987, 30. 537.
`-
`injected in mice. Differentiation between -
`important step for the identification oi a -
`19. E. A. Andrews and L C. Marluflnesthe-'v"
`iolaml. 1982, 57. 314.‘
`'___the two stereoisomers of (20) was "
`- potential receptor site for this series of
`20. D. T. Witiak e!‘ at J. Med. Chem. 1975.
`": further magnified {1 3.1 times} when the
`amino- acid anticonvulsants.
`lnvesti'- '
`.-
`_ 19. .1419; L Turski, s. s. Meldrum and
`drugs were given oraliy. All compounds
`_
`' gations currently in progress are aimed.
`J. F. Collins, Brain Res". 1985. 335. 1523
`1 "tested were less toxic after oral adrninis- '
`. P. V. Taberner and F. Roberts. Eur. J.
`at elucidating the generality-o_f these ;_ __
`
`Pharmatcofi, 1978. 52. 231.‘ O. Goldbefil
`-
`- observations as well as determir_:in'g the ‘
`-' andv. l. Teichberg.J. Med. Chem..1_985.
`mode at action of these new medicinal
`-'
`._ 23,1957.
`'
`--
`-
`—
`'-agents} including the origin of the
`. 2.1. J. D. Conley and H. l(ohn, un'publisl’I°5
`. results: H. Kuhn. .1. o. Conley and J. D.
`observed higlt-ertatttiospecificity in this :_-
`
`SySteI'l1_
`.
`..
`l.aamler.Br_a:'rr Res. submitted.
`;
`__
`. "
`'. IPR2014-01126- Exhibit 1019, p. 4
`c;ii'm_i.«.-i_iin«'ti~i entrain riuiisii
`
`E-99°!‘-19‘
`
`.
`
`,
`
`..
`'
`
`-
`__
`
`-
`
`.
`
`/
`
`#
`
`"- 5°
`
`'
`
`'
`
`'
`
`
`
`
`
`
`
`
`
`!
`
`"
`
`#
`
`$
`
`!
`
`"
`
`"
`
`
`
`%
`
`$
`
`&
`
`'
`
`(
`
`)
`
`*
`
`)
`
`+
`
`"
`
`!
`
`"
`
`.
`
`
`
`tration than after intraperitoneal injec-
`tion. Significantly, the low toxicity of the
`D-isomers as well as the racemates
`contributed to their
`large protective
`indices* {Pl}, which approached that of
`phenytoinfi‘