CENTER FOR DRUG EVALUATION AND
`
`RESEARCH
`
`APPLICA TION NUMBER:
`
`NDA 22-253 & 22-254
`
`PHARMACOLOGY REVIEWg S!
`
`

`

`Tertiary Pharmacology Review
`
`By:
`Paul C. Brown, Ph.D., ODE Associate Director for Pharmacology and Toxicology
`0ND 10
`NBA: 22—253, 22—254, We
`M4)
`Submission date: September 28, 2007
`Drug: lacosamide (tablet)
`Sponsor: Schwarz Biosciences
`Indication: treatment of Epilepsy as adjunctive therapy in patients with partial onset
`seizures aged 16 years and older
`
`Reviewing Division: Division of Neurology Products
`
`Introductory Comments: These NDAs have been submitted for the same drug
`substance and essentially same indication. Th6 -- NDAs differ in the formulation of
`
`the drug product. NDA 22-253 is for a tablet, 22-254 is for an injectable formulation .4,
`). Another NDA .—.— was submitted to the Division of
`Anesthesia, Analgesia and Rheumatology Products for the management of neuropathic
`pain associated with diabetic peripheral neuropathy.
`
`The pharm/tox reviewer and supervisor found the nonclinical information submitted for
`lacosamide to be sufficient to support its use for the proposed indication.
`
`Reproductive and developmental toxicity:
`The sponsor has proposed a pregnancy category of C. The reviewer and supervisor agree
`with this category.
`
`The reproductive and developmental studies did not indicate that lacosamide was
`teratogenic but some embryofetal and perinatal mortality and growth deficits were
`observed. In addition, a juvenile animal study in which rats were treated beginning on
`postnatal day seven demonstrated some neurobehavioral changes, brain weight decrease
`and delay in sexual maturation in females. I agree that these studies support a pregnancy
`category of C. I agree with the supervisory memo that additional embryofetal studies are
`not needed at this time.
`
`Neurotoxicity:
`The reviewer recommended that the sponsor should examine the effects of lacosamide on
`brain development during the prenatal and early postnatal periods using more sensitive
`techniques for assessing CNS structure and function than were employed in the standard
`pre— and postnatal development study.
`
`Because of the apparent neurobehavioral effects observed in the juvenile animal study,
`and the potential serious consequences of neurotoxicity in children, I agree that further
`assessment can be requested from the sponsor after approval.
`
`

`

`Conclusions:
`
`I concur With the Division pharm/tox conclusion that the nonclinical data support
`approval of this NDA.
`
`I concur with the recommendation for collecting additional developmental neurotoxicity
`data post approval.
`
`I agree with the labeling changes suggested in the supervisory memo including deletion
`of sectionW
`
`{1(4)
`
`APPEARS THIS WAY
`0N ORIGINAL
`
`

`

`This is a representation of an electronic record that was signed electronically and
`this page is the manifestation of the electronic signature.
`
`Paul Brown
`
`-
`
`7/17/2008 03:17:20 PM
`PHARMACOLOGI ST
`
`

`

`MEMORANDUM
`
`DEPARTMENT OF HEALTH & HUMAN SERVICES
`Public Health Service
`
`Food and Drug Administration
`
`Division of Neurology Products (HFD-120)
`Center for Drug Evaluation and Research
`
`Date:
`
`July 16, 2008
`
`From: Lois M. Freed, Pth.
`Supervisory Pharmacologist
`
`Subject: Lacosamide (SPM927) Tablet (NDA 22-253), Injection (NDA 22-254), ~———
`
`submitted September 28, 2007
`
`31(4)
`
`Schwarz Pharma has submitted - NDAs to the Division of Neurology Products for
`lacosamide (SPM927):
`
`o NDA 22-253: Lacosamide tablet for “treatment of Epilepsy as adjunctive therapy
`in patients with partial onset seizures aged 16 years and older”.
`0 Lacosamide tablet for the “management ofneuropathic pain associated
`with diabetic peripheral neuropathy” is being reviewed by the Division of
`Anesthesia, Analgesia and Rheumatology Products under ND;A
`o NDA 22-254: Lacosamide injection for “treatment of Epilepsy as adjunctive
`therapy in patients with partial onset seizures aged 16 years and older when oral
`administration is temporarily not feasible”.
`M
`
`The nonclinical data in support of these NDAs were submitted under NDA 22—253 and
`were cross-referenced in NDAs 22-254 and
`-—~ Review of the nonclinical data
`
`submitted in support of the oral formulations was shared by DNP and DAARP.
`
`In DNP, J. Edward Fisher, PhD. reviewed the following nonclinical studies:
`0 Pharmacology (i.e., animal efficacy, mechanism of action) relevant to the epilepsy
`indication.
`'
`
`0 Toxicology
`o Sprague-Dawley rat (14-day iv)
`o Beagle dog (14-day iv.)
`0 Reproductive toxicology
`0 Combined oral fertility and developmental toxicity study in Sprague-
`Dawley rat
`
`31(4)
`
`?
`
`

`

`0 Oral embryo-fetal development study in female New Zealand White rabbit
`0 Oral pre- and post-natal development study in Sprague—Dawley rat
`Juvenile animal
`
`0
`
`0 6-week oral toxicity study in juvenile Sprague—Dawley rat
`0 6-week oral dose-range finding study in juvenile Beagle dog
`0 Genetic toxicology
`,
`o In vitro bacterial reverse mutation (Ames) assay (2 assays)
`o In vitro mammalian cell gene mutation assay
`0 In vivo mammalian cell erythrocyte micronucleus assay
`0 In vivo UDS assay in male Fischer rat (hepatocytes)
`
`Terry Peters, D.V.M, reviewed (included in Dr. Fisher’s review) the following
`nonclinical studies:
`'
`
`9 Carcinogenicity
`o 2-year oral studies in CD-l mouse and Sprague-Dawley rat '
`
`In DAARP, BeLinda Hayes, PhD. reviewed the following nonclinical studies:
`0 Pharmacology (i.e., animal efficacy, mechanism of action) relevant to the
`neuropathic pain indication.
`Safety Pharmacology (CNS, cardiovascular, respiratory)
`0
`0 PK/ADME
`
`0 Toxicology
`0 Mouse (acute p.o., i.v., 13—week p.0.)
`0 Rat (acute p.o., i.v., 13-week p.o., 6—month p.0.)
`0 Dog (12-month p.o.)
`
`Based on their review of these data, Drs Fisher and Hayes have concluded that the
`nonclinical data support approval of lacosamide. However, Dr. Fisher recommends
`additional studies be conducted post-approval to assess the potential developmental
`toxicity of lacosamide. Overall nonclinical findings and the basis for the post-approval
`recommendations will be briefly, discussed.
`
`The following is based on information provided in reviews by Drs. Fisher and Hayes.
`These reviews should be consulted for detailed descriptions and discussion of the
`nonclinical data.
`
`Lacosamide ((R)-2-acetamido—N-benzyl-3-methoxypropionamide), a structural
`0
`analog of D-serine, is a member of a class of fimctionalized amino acids. The sponsor has
`proposed that lacosamide exerts anticonvulsant activity via two distinct mechanisms: (1)
`selective enhancement of “slow inactivation of voltage gated sodium channels without
`affecting fast inactivation” and (2) “modulation of CRMP—2 activity”. CRMP—2
`(collapsing response mediator protein-2) is one of four CRMP genes (CRMP 1-4) that
`have been identified in rat. CRMPs are expressed primarily in the nervous system and are
`thought to have an important role in development of the CNS. Lacosamide binds to
`CRMP-2 with a KB of SuM. Lacosamide demonstrated no appreciable affinity for a
`number of other molecular targets (e.g., receptors, transporters).
`
`

`

`There does not appear to be clinical evidence that enhancement of slow inactivation, as
`opposed to fast inactivation, of voltage gated sodium channels conveys any therapeutic-
`benefit. There also does not appear to be documentation that inhibition ofCRMP-2
`activity has a role in prevention or treatment of epilepsy. A recent publication (Errington
`AC et a]. Male Pharm 73(1):]57—169, 2008) funded, at least in part, and co-authored by
`the sponsor states that""I'he molecular mode of action of LCM is still unknown.”
`
`However, there is concern that inhibition of CRNEP-Z activity may have adverse effects
`on neurobehavioral development (discussed further below).
`
`.
`
`The PK/ADME of lacosamide was assessed in all species used for toxicity testing
`0
`(i.e., CD-l mouse, Sprague-Dawley rat, Beagle dog, and New Z'ealand White rabbit) and
`in human. Parent was the major drug-related circulating compound in all species. The
`main circulating metabolite, SPM 12809 (O-desmethyl; no demonstrated
`'
`pharmacological activity), was also detected in mouse, rat, and dog plasma at levels
`exceeding 'those in human plasma (i.e., SIG-15% of parent compound). Therefore, all
`animal species tested were acceptable models for assessing the potential for lacosamide-
`induced toxicity in humans.
`
`'
`
`In safety pharmacology and general toxicology studies, the primary dose-
`0
`limiting toxicities in all species (except in thejuvenile rat) were CNS-related, and
`included ataxia, decreased spontaneous motor activity, and convulsions. The only other
`notable adverse effect was prolongation of the PR and QRS intervals and AV block
`observed in dog and monkey. (Similar cardiovascular effects have also been reported in
`human.) Lacosamide exhibited no carcinogenic potential in adequately conducted 2-year
`studies in mouse and rat.
`
`To support development and approval of lacosamide injection, the sponsor conducted 2-
`week i.v. toxicity studies in rat and dog. Toxicities were similar to those observed in the.
`oral toxicity studies, i.e., CNS signs were the dose-limiting toxicities. Since, in humans,
`the i.v. formulation is essentially bioequivalent to the oral tablet except that Cmax is
`slightly (:20%) higher at similar doses, these studies were sufficient to bridge to the oral
`database.
`
`No adverse effects were detected in a combined mating/fertility and embryo—
`0
`fetal development study in rat (oral doses up to 200 mg/kg) or in an embryo-fetal
`development study in rabbit (oral doses up to 25 mg/kg) using qd dosing. However, in
`dose-ranging finding studies, increased resorptions and/or decreases in fetal body weight
`were observed at the high doses used in the definitive studies and higher (up to 300 and
`50 mg/kg in rat and rabbit, respectively). As Dr. Fisher notes, it is unclear why these
`adverse effects were not observed in the definitive studies. It is possible that the high
`dose used in each species represents a threshold dose and that the lack of reproducibility
`is simply due to inter—study variability. Dr. Fisher considered the definitive studies
`adequate, as conducted. However, due to the fact that “the maximum plasma drug
`exposures tested were relatively low (or uncertain) compared to those expected
`
`

`

`clinically”, Dr. Fisher recommends that the sponsor be asked to conduct a repeat
`embryofetal study in one species, if higher plasma exposures can be achieved using b.i.d.
`dosing.
`
`In the pre— and post-natal development study in rat, adverse effects (including
`prolonged gestation, increases in stillborn pups and postnatal mortality, and decreases in
`pup body weight) were observed at all oral doses (25-200 mg/kg qd), and prolonged
`gestation occurred at the high dose. There were no statistically significant effects on
`postnatal development; however, Dr. Fisher notes that there was “some suggestion of an
`effect on offspring learning and memory”. Adverse effects on neurobehavioral
`development were also observed in a juvenile rat study, as were decreases in brain weight
`(absolute and relative). As Dr. Fisher also notes, these effects are consistent with
`lacosamide’s proposed inhibition of CRMP-Z, demonstrated in vitro by inhibition of
`. “CRMP-2 mediated effects of neurotrophins. . .on axonal outgrth of primary
`hippocampal cells, at concentrations as low as 1 11M..."
`
`Based on these data, Dr. Fisher has recommended that the sponsor conduct additional
`studies post-approval to further and more carefully assess the potential for lacosamide to
`have adverse effects on brain development. Since pediatric use is not being proposed, the
`most critical periods to assess in rat would be those that correspond to the entire period of
`human fetal development, i.e., organogenesis through the first 7 days postpartum.
`
`I'understand Dr. Fisher’s concern regarding the lack of a substantial margin between
`exposures achieved in rats and those anticipated in humansat the MRHD, and the lack of
`any plasma exposure coverage in the rabbit. I also agree that the dose-limiting clinical
`signs observed in both rat and rabbit are probably related to Cmax, which would suggest
`that higher plasma exposures could be achieved with b.i.d. dosing. However, an increase
`in resorptions was also observed in the rat and rabbit dose-range finding studies at doses
`similar to or 52 fold higher than those tested in the pivotal studies. This would suggest
`that substantially higher doses may not be achievable, particularly since there is no basis
`for assuming that the increases in resorptions are related to Cmax. In addition, since
`clearance appears to be saturated at higher doses (e.g., 200 mg/kg, the high dose in the
`pivotal study) in rat, it is possible that higher systemic exposure resulted from initiation
`of dosing prior to mating (as in the combined mating/fertility and embryo-fetal study)
`than could be achieved if dosing were initiated on GD6-7, as is routine in embryo-fetal
`development studies. For these reasons, it is my opinion that it is unlikely that a better
`evaluation could be achieved in repeat embryo-fetal studies.
`
`I do concur with Dr. Fisher’s recommendation that fiirther assessment of lacosamide’s
`effect on brain development is needed, and that this assessment may be conducted post-
`approval. Such an assessment should certainly involve dosing in rat throughout the
`critical periods that correspond to the entire period of human fetal development with,
`perhaps, direct dosing of the neonate, and, as Dr. Fisher notes, the use of sensitive
`methods for assessing neurobehavioral function and expanded histopathological
`examination of the brain. In addition, twice daily dosing should be considered since it
`more closely mimics the human dosing regimen.
`
`

`

`Reeommendations
`It is my opinion that the nonclinical data support approval ofNDAs 22-253, 22-254:=N;=
`‘V": with a post marketing commitment to conduct an additional assessment of
`lacosamide’s effect on brain development (as discussed above).
`
`“k“
`
`Labeling recommendations are as follows:
`
`// / =
`// /
`
`

`

`'_ 3- Page(s) Withheld
`
`Trade Secret / Confidential (b4)
`
`_
`
`Draft Labeling (b4) .
`
`Draft Labeling (b5)
`
`Deliberative Process (b5)
`
`

`

`ATTACHMENT 1
`
`Plasma exposures (Cmax, AUC) achieved at the high doses (except'as noted) used in the
`pivotal toxicology studies are provided in the following table (in M-F; data in [brackets]
`are from dose-range finding, not definitive, studies):
`.
`
`-
`
`; *hr/mL
`_lmL
`(mg/kg)
`TIME
`“-——
`6-month -E-
`
`
`
`_
`
`fetal
`
`-
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`" m”
`
`
`v
`
`" ‘5“
`
`
`S-D rat
`
`juvenile
`
`-D rat ‘ n-m
`“——_
`““__
`
`'
`
`juvenile d-ranging
`
`CD-l mouse -—_“_
`
`(i.v.)
`0-24 hr, '0-00', 0-4 hr, 0-8 hr, data estimated from AUC(0-12hr) 33 data; i.v. data estimated based on
`15-min infusion, with Cmax being =20% higher and AUC similar to the same dose of the oral tablet.
`
`(I.o'
`
`APPEARS THlS WAY
`0N ORIGINAL
`
`

`

`This'Is a representation of an electronic record that was signed electronically and
`this pageis the manifestatIonofthe electronic signature.
`'
`'
`
`
`
`
`/S/
`
`Lois Freed
`7/16/2008 11:00:50 AM
`PHARMACOLOGIST
`
`

`

`
`
`DEPARTMENT OF HEALTH AND HUMAN SERVICES
`PUBLIC HEALTH SERVICE
`’
`FOOD AND DRUG ADMINISTRATION
`CENTER FOR DRUG EVALUATION AND RESEARCH
`
`PHARMACOLOGY/TOXICOLOGY REVIEW AND EVALUATION
`
`NDA NUMBER:
`
`SERIAL NUMBER:
`
`DATE RECEIVED BY CENTER:
`
`22—253, 22-254 '
`
` :
`
`MAI
`
`I
`
`000
`
`9/28/07
`
`PRODUCT:
`INTENDED CLINICAL POPULATION:
`
`Lacosamide (SPM927) Tablet, Injection, "TT’T—
`epilepsy
`
`M4)
`
`SPONSOR:
`
`Schwarz Biosciences
`
`_
`
`REVIEW DIVISION:
`PHARM/TOX REVIEWER:
`
`PHARM/TOX SUPERVISOR:
`
`DIVISION DIRECTOR:
`PROJECT MANAGER:
`
`Division of Neurology Products (HFD-120)
`Ed Fisher
`
`Lois Freed
`
`Russell Katz
`Jackie Ware
`
`

`

`TABLE OF CONTENTS
`
`I.
`
`INTRODUCTION AND DRUG HISTORY ................................................................................................ 3
`
`ll. PHARMACOLOGY .................................................................................................................................. 4
`A. Brief summary .................................................................................................................... 4
`B. Mechanism of action ....................................................' ...................................................... 4
`C. Animal models .................................................................................................. 6
`
`D. Safety pharmacology ........................................................................................................... 7
`
`III. PHARMACOKINETICS/TOXICOKINETICS ........................................................................... 12
`
`A. Brief summary ................................................................................................ 12
`B. Plasma drug levels ............................................................ ............................... 12
`
`IV. TOXICOLOGY .................................................................................................. '............... 14
`
`A. Repeat-dose oral toxicity ................................................................................... 14
`B. Repeat-dose iv toxicity ...................................................................................... 14
`C. Genetic toxicity ................................................................................................ 18
`D. Carcinogenicity ................................................................................................ 27
`E. Reproductive and developmental toxicology ..............‘............................................ 35
`
`V. SUMMARY AND EVALUATION ........................................................................................................... 64
`
`VI. RECOMMENDATIONS ........................................................................................................................ 74
`
`APPEARS THIS WAY
`ON ORIGINAL
`
`

`

`I.
`
`INTRODUCTION AND DRUG HISTORY
`
`NDA number: 22-253 (oral tablet), 22—254 (injection)
`
`b(4)
`
`Date of submission: 9/28/07
`
`Sponsor:
`
`Schwarz Biosciences
`
`Drug:
`
`Trade name:
`
`Generic name:
`
`lacosamide
`
`Code names: ADD 234037; harkoseride; SPM 927
`
`Chemical name: (R)—2-acetamido-N-benzyI-3-methoxypropionamide
`
`CAS registry number:
`
`175481-36-4
`
`Molecular formula: C13H18N203
`
`Molecular weight: 2503
`
`Structure:
`
`:r
`
`0
`
`if)
`
`/‘
`
`Q
`0345
`
`Relevant lND: 57,939
`
`Drug class: sodium channel modulator
`
`Indication: epilepsy
`
`Route of administration: oral (tablets -———
`
`,injection
`
`Previous reviews: Original IND review dated 3/22/99
`CAC-EC reviews dated 7/13/00, 3/1/01, and 6/5/02
`CAC-EC minutes dated 8/8/00, 4/24/01, and 7/9/02
`
`Tables and figures are taken directly from the sponsor's submission unless noted otherwise.
`
`

`

`ll.
`
`A.
`
`PHARMACOLOGY
`
`BRIEF SUMMARY
`
`Lacosamide (LCM) is a member of a series of functionalized amino acids that were specifically
`synthesized as anticonvulsant drug candidates. In standard in vitro radioligand binding assays,
`LCM showed no significant affinity for any of the typical binding sites,
`including a variety of
`neurotransmitter, neuropeptide, and growth factor receptors,
`ion channels,
`transporters, and
`intracellular signaling enzymes. However, weak displacement of binding (25% at 10 uM) was
`observed for
`the sodium channel site 2. Electrophysiological studies indicated that LCM
`selectively enhances the slow inactivation of sodium channels without affecting fast inactivation.
`This was shown to be in contrast to other sodium channel modulators such as lamotrigine,
`phenytoin, and carbamazepine which enhance fast inactivation. No significant modulation of
`voltage-gated potassium (KCNQZ/S) or calcium channels (L-, N-, P- and T—type) was detected.
`
`In studies using proteomic affinity-labeling techniques, collapsin-response mediator protein 2
`(CRMP-Z; also called DRP-2, dihydropyrimidinase-related protein) was subsequently identified as
`a potential binding target of LCM.
`In radioligand binding experiments using a cloned human
`analogue'of CRMP-2 expressed in Xenopus oocytes, LCM exhibited a binding affinity of 5 pM.
`
`Due its structural relationship to the endogenous amino acid D—serine, which acts as an NMDA
`receptor antagonist, LCM was assessed for binding at glutamate receptors.
`In an initial
`experiment, 50% displacement of a glycine site antagonist was observed with an ICSO of 5.2
`pmol/L. However,
`in a follow—up study using more specific ligands, LCM (10 pmol/L) did not
`produce significant (>50%) displacement of specific binding at AMPA, kainate, NMDA (agonist,
`glycine and phencyclidine binding sites) or glycine receptors isolated from rat brain. But in a
`functional experiment using recombinant NMDA receptor subtypes, LCM inhibited NMDA— and
`glycine-induced currents at NR1/ZB receptors, albeit with an ICSO of 1.89 mmol/L.
`
`LCM showed anticonvulsant activity in various rodent seizure models, ie, maximal electroshock
`seizures (MES), 6 Hz seizures, hippocampal kindling, audiogenic seizures (AG8), and self
`sustaining status epilepticus (SSSE). Lacosamide was inactive against clonic convulsions
`induced by so pentylenetetrazol (PTZ), bicuculline, and picrotoxin, but it did inhibit NMDA-induced
`convulsions in mice. Although inactive against sc PTZ—induced threshold clonic convulsions, LCM
`elevated the seizure threshold somewhat in the iv PTZ test at the MES EDSO. The O—desmethyl
`metabolite, SPM 12809, and the S-entantiomer of LCM, SPM 6953, were inactive in the MES test
`at relevant doses.
`
`In vitro investigations of the cardiovascular effects of LCM showed that LCM reduced the action
`potential duration in cardiac tissue and inhibited sodium current in isolated cells. Effects on
`sodium current were dependent on membrane potential, with higher
`inhibition at more
`depolarized potentials.
`In vivo studies showed that LCM decreased cardiac conduction.
`In
`anesthetized instrumented dogs, LCM induced hypotensive effects characterized mainly by
`reduced contractility, as indicated by decreases in systolic left ventricular pressure and left
`ventricular pressure over
`time (dP/dt) and reduced cardiac output. These effects were
`accompanied by increases in PR interval and QRS complex duration and by AV block. Similar
`EEG effects were seen in monkeys, ie, QRS prolongation and AV and ventricular block.
`
`B.
`
`MECHANISM OF ACTION
`
`LCM (10—100 pM) showed no significant affinity (>50°/o inhibition) for any of the typical receptors,
`channels, or enzymes screened, but did bind weakly (25—50% inhibition) to the sodium channel at
`the batrachotoxin site 2. LCM did not modulate the uptake of NE, DA, or 5HT into synaptosomes,
`and did not bind to GABA transporters or influence the activity of GABA transaminases. The
`
`

`

`major desmethyl metabolite (SPM 12809) also showed no significant binding to the receptors
`tested.
`'
`
`In early mechanistic studies, sustained repetitive firing (SRF) of current clamped rat cortical
`neurons evoked by applying current pulses (750 ms, every 12—14 s) was weakly (78 vs 96% in
`control) but significantly reduced in frequency by LCM (100 uM) without apparent changes in
`individual spike properties. This effect was different from that produced by the known sodium
`channel-blocker phenytoin (100 uM), which produced a large (28 vs 96%) attenuation of spiking
`during the evoked period of SRF and progressively reduced the amplitude and eventually
`terminated the AP, but the results suggested that LCM could be acting in part via inhibition of
`voltage gated sodium channels (VGSCs). When SRF duration was prolonged (10 s) LCM
`produced significant (EC50: 48 uM) inhibition, but not within the first second of the burst (ECSO:
`_ 640 uM).
`
`In a study conducted in patch-clamped mouse neuroblastoma cells, which was designed to
`recruit only fast inactivation (without significant development of slowly inactivated conformations)
`of the VGSC, significant hyperpolarizing shifts in the fast
`inactivation voltage curves were
`produced by the classical anticonvulsants LTG, CBZ, and DPH (all 100 uM).
`in contrast, LCM
`(100 pM) did not produce a hyperpolarizing shift in the V50 for inactivation of sodium currents in
`these cells,
`ie, the voltage for half maximal
`inactivation after equilibration with LCM was not
`significantly different from V50 in control solutions. However, LCM (100 uM) did produce a
`hyperpolarizing shift
`in the voltage dependence of slow sodium channel
`inactivation and
`promoted channel entry into the slow inactivated state, but did not alter the rate of recovery. The
`effect of the other drugs on slow inactivation was not
`tested.
`(Table "3.1; adapted from
`Beyreuther et al, CNS Drug Reviews, 13:21—42,2007).
`
`Table "3.1. Effect of anticonvulsants on the voltage dependence of Na+ channel inactivation
`
`
`
`
`
`
`
`
`Lamotrigine CarbamazepineControl Lacosamide Phenytoin
`Fast inactivation
`-66 '
`-65
`-72*
`-80*
`-77*
`V50 [mV]
`n.t.
`n.t.
`n.t.
`-58*
`-43
`Slow inactivation
`V50 [mV]
`n.t., not tested. V50, half maximal reduction of channel availability.
`All drugs were applied at a concentration of 100 pM. Steady—state fast inactivation was tested with conditioning prepulses
`of 500 msec between -120 and -20 mV. For steady—state slow inactivation conditioning, prepulse duration was 5 sec,
`followed by a 1-sec hyperpolarizing pulse to -100 mV prior to test pulse to —10mV. *P < 0.05 vs control.
`
`indicated a selective effect of LCM on slow inactivation,
`that
`In another experiment
`neuroblastoma cells were maintained at a holding potential of —60 mV and depolarized by a 10 ms
`test pulse to 0 mV at 0.5 Hz. The protocol was then repeated in each cell with a 500 ms
`hyperpolarizing pulse to -100 mV applied prior to the depolarizing test pulse in order to remove
`fast inactivation. In all cells tested all four of the anticonvulsants (LCM, LTG, CMZ, DPH; all 100
`(AM) produced a reduction in Na+ current when the holding potential was -60 mV. For LTG, CBZ,
`and DPH application of the hyperpolarizing prepulse to -100 mV markedly reduced the blocking
`action on the channel. In contrast, the inhibition produced by LCM was not significantly altered by
`the hyperpolarizing prepulse. (Table llB.2; adapted from Beyreuther et al, CNS Drug Reviews,
`13121-422007).
`_
`‘
`
`

`

`Table "3.2. Inhibition of Na+ current with and without removal of fast inactivation
`
`
`
`
`
`
`
`
`Lamotrigine CarbamazepineLacosamide Phenytoin
`% Inhibition of Na+ current
`32
`50
`71
`48
`with fast inactivation
`1*
`6*
`12*
`29
`% Inhibition of Na+ current
`after removal of fast inactivation—.—______—_—_
`Availability of Na+ channels was determined in neuroblastoma cells by a 10-msec test pulse to 0 mV from a holding
`potential of -60 mV. Fast inactivation was removed by a hyperpolarizing pulse to -100 mV (500 msec) prior to the 10-
`msec test pulse. Concentration of drug was 100 pM for all compounds. *P < 0.05 versus % inhibition with fast inactivation.
`
`In affinity-labeling studies, LCM was modified chemicaily in order to allow covalent crosslinking to
`potential targets. A set of four LCM-related affinity reagents applied to rat brain fractions led to
`enrichment of an overlapping set of proteins, including a dihydropyrimidinase-related protein and
`some additional proteins related to the vesicle release machinery. Although the results suggested
`that dihydropyrimidinase-related protein may be a target of LCM,
`they were considered
`inconclusive, since this type of chemical crosslinking experiment is susceptible to nonspecific side
`reactions.
`
`Based on the results of this study, a follow-up study was performed in which the human analogue
`of DRP-2 (CRMP-Z) was cloned, expressed in Xenopus oocytes, and the binding of radiolabeled
`SPM 927 was examined. The results indicated a membrane—associated binding site in oocytes
`transfected with DRP—2; competitive and specific binding could be observed with a KD value of
`about 5 uM.
`It was pointed out, however, that the expression of DRP—Z couId not be monitored
`directly in this system due to the lack of a functional assay. In cultured rat hippocampal neurons,
`NT3 and BDNF-stimulated axon growth was inhibited by 1, 10, 100 and ZOOpM LCM. The
`positive reference compound wortmannin had a similar inhibitory effect on both neurotrophin-
`induced effects. These results were thought to provide evidence that LCM may exert some of its
`pharmacological action via inhibition of CRMP—Z.
`
`When LCM (10uM) was evaluated for displacement of various radioligands from glutamate
`subtype and glycine binding sites (glutamate, AMPA; glutamate, kainate; glutamate, NMDA,
`agonist; glutamate, NMDA, glycine; glutamate, NMDA, phencyclidine; glutamate, non— selective;
`and glycine, strychnine-sensitive), no significant responses (250% stimulation or inhibition) were
`seen.
`In a functional experiment using recombinant NR1/2A and NR1/ZB NMDA receptor
`subtypes expressed in Xenopus oocytes, LCM inhibited NMDA— and glycine-induced currents at
`NR1/ZB but not at NR1/2A receptors with an I050 of 1.89 mmol/L. Binding was observed to be
`independent of glycine concentration, indicating noncompetitive antagonism.
`
`C.
`
`ANIMAL MODELS OF EPILEPSY
`
`In initial screening, LCM blocked sound-induced seizures in mice with an ED50 of 0.63 mg/kg, ip
`and protected mice (ED50 = 4.5 mg/kg,
`ip) and rats (ED50 = 3.9 mg/kg, po) against maximal
`electroshock (MES)—induced tonic-extension seizures,
`indicating that LCM is effective in
`preventing seizure spread (Table IlC.1; from Stohr et al, Epilepsy Res 74:147-54,2007). LCM
`showed efficacy in the 6-Hz psychomotor seizure test, which is considered a model for treatment-
`resistant seizures, with an ED50 of 9.99 mg/kg ip.
`In this model, LCM exhibited additive to
`synergistic’effects with a variety of AEDs (pronounced synergism observed with Ievetiracetam
`and CBZ). LCM did not block GTCSs induced by the GABAA-receptor antagonist bicuculline or
`the chloride channel blocker picrotoxin. LCM was also ineffective against clonic Seizures induced
`by so bolus injection of pentylenetetrazole (PTZ) in rats and mice. However, LCM significantly
`increased the threshold for minimal seizures induced by timed iv infusion of PTZ in mice. In the
`rat hippocampal kindling model, which is thought to predict activity against complex partial
`
`

`

`seizures, the ED50 of LCM for reduction of the seizure score from 5 to s3 in fully kindled rats was
`13.5 mg/kg. LCM (210 mg/kg ip) also significantly inhibited kindling development in this model.
`LCM was also active in a model of status epilepticus, blocking limbic seizures induced by self
`sustaining status
`epilepticus
`(SSSE)
`in
`rats. LCM also increased survival
`and was
`neuroprotective in this model.
`
`Table llC.1
`
`Tablet
`
`
`- Summary of anti-convuisant profileof tacosamide in initiai screening and differentiation tests in rnice and rats
`
`Species and-route
`- oftacosamide
`Mimi‘s.
`'
`
`,
`
`-
`
`‘
`
`“festa
`,
`MES
`. FringsAGS
`61-12
`scP’iZ
`
`/‘
`
`Time of .
`test in)”
`0,57
`0.5
`0.5'
`‘ 0.25
`
`,
`V
`
`'
`
`ED50 (mgikg)
`
`.
`
`1
`
`.
`
`"
`5
`
`4.46
`0.63
`9.99
`>25
`
`”ms“ (mg/kg)
`4
`—
`——
`e
`—
`
`_
`
`.
`
`.'
`
`'
`
`'
`
`95% Cl (mg/kg)
`
`.
`
`3.72—5.46
`6.37—0.99
`. 27.73—12.78
`
`Protective index
`(Tnsotmwib
`6.0
`43.0
`2.?
`n.a.
`
`2550-28310
`9.1mm '
`2.58—6.20
`— -
`—
`
`’
`
`n.a.
`n.a.
`—
`n.a..
`>128
`
`—
`
`'
`
`,
`
`.-
`
`.
`._
`[$213,133.
`_Rats,p.o.
`
`.
`
`>50
`1'
`sc BIC
`>30
`1
`so PIC 3
`—
`0.25
`Rotorod " .5
`.
`13.5
`r015}
`Kindling
`.'
`3.9oi,‘
`, No.5»
`MES '
`I
`>250
`/
`' 0,5,
`scmv :.
`- ‘-
`0.25724
`Minimalmotbr
`’
`impairment ‘ “ " '
`a At{easteight animais were used per treatment grbup in each test
`5 Plcatcuiated with T050 obtained in CF§1 mice and £950 in Frings mice.
`
`,
`
`'
`
`~
`
`/
`
`‘
`
`j
`. f
`‘
`
`.
`.1}
`
`‘ c" f
`—,
`. 26.8
`T —
`1
`.—
`i —
`>500
`'
`
`.
`
`.
`
`.
`
`D.
`
`SAFETY PHARMACOLOGY
`
`ln Purkinje fibers isolated from male Beagle dog hearts, LCM (1.5, 5, 15, 50, 150 pmollL) induced
`concentration-dependent decreases (SS) in action potential duration at 50%, 70% and 90% of
`repolarization (APD50, APD70, APD90, respectively), both at normal (1 Hz) and low (0.2 Hz)
`stimulation frequencies (Table IID.1). At the high concentration, decreases in APD50, APD70 and
`APD90 ranged from 30 to 47% at normal frequencies and from 32 to 54% at low stimulation
`frequencies,
`respectively. This shortening in action potential duration was associated with
`reductions in the maximal rate of depolarization (Vmax). At 150 umol/L, Vmax was reduced by
`32% and 36% at 1 Hz and 0 2 Hz, respectively.
`
`Table IID.1
`
`Effect of lacosamide on cardiac action potential in isolated Purkinje fibers
`Change in % versus pretreatment values
`
`Stimulation frequency 1 Hz
`L1cnsamide
`
`(011:9anation {plant/L}
`
`

`

`Stimulation frequency 0.2 Hz
`
`
`
`
`
`= p s 0.0 , ** = p s 0.01 compared to the vehicle group
`
`In human embryonic kidney cells (HEK293) stably expressing the cardiac SCN5A Na+ channel (=
`hHNa), LCM (10, 100, 200, 500, 1000 uM) produced a concentration-dependent inhibition of
`sodium currents (IC50 of 293 um