U.S. patent application number 16/432468 was filed with the patent office on 2019-12-19 for compositions and methods for treating respiratory depression with fenfluramine.
This patent application is currently assigned to ZOGENIX INTERNATIONAL LIMITED. The applicant listed for this patent is ZOGENIX INTERNATIONAL LIMITED. Invention is credited to Carl L. Faingold, Bradley S. Galer, Parthena Martin.
Application Number | 20190380979 16/432468 |
Document ID | / |
Family ID | 67253954 |
Filed Date | 2019-12-19 |
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United States Patent
Application |
20190380979 |
Kind Code |
A1 |
Galer; Bradley S. ; et
al. |
December 19, 2019 |
COMPOSITIONS AND METHODS FOR TREATING RESPIRATORY DEPRESSION WITH
FENFLURAMINE
Abstract
5-HT receptor agonists are useful in the treatment of a variety
of diseases. Provided herein are methods of treating and/or
reducing the occurrence of respiratory depression caused by an
opioid in a human patient or patient population using a 5-HT
receptor agonist, such as, for example, a 5-HT4 agonist (e.g.,
fenfluramine). Methods of stimulating one or more 5-HT.sub.4
receptors in the brain of a patient undergoing treatment with an
opioid, wherein the patient is at risk of respiratory depression,
by administering a 5-HT4 agonist (e.g., fenfluramine) to a subject
in need thereof are provided. Pharmaceutical compositions for use
in practicing the subject methods are also provided.
Inventors: |
Galer; Bradley S.; (West
Chester, PA) ; Faingold; Carl L.; (Emeryville,
CA) ; Martin; Parthena; (Emeryville, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ZOGENIX INTERNATIONAL LIMITED |
Berkshire |
|
GB |
|
|
Assignee: |
ZOGENIX INTERNATIONAL
LIMITED
Berkshire
GB
|
Family ID: |
67253954 |
Appl. No.: |
16/432468 |
Filed: |
June 5, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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62685200 |
Jun 14, 2018 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61K 31/5375 20130101;
A61P 11/16 20180101; A61K 31/137 20130101; A61P 25/08 20180101;
A61K 31/166 20130101; A61K 31/439 20130101 |
International
Class: |
A61K 31/137 20060101
A61K031/137; A61P 25/08 20060101 A61P025/08 |
Claims
1. A method of treating respiratory depression caused by an opioid,
barbiturate or benzodiazepine in a human patient, comprising:
administering to the patient a therapeutically effective dose of a
5-hydroxytryptamine receptor 4 agonist (5-HT.sub.4 agonist); and
allowing the 5-HT.sub.4 agonist to stimulate 5-HT.sub.4 receptors
in the patient, thereby treating respiratory depression caused by
the opioid, barbiturate or benzodiazepine in the patient.
2. (canceled)
3. A method of reducing incidence of respiratory depression caused
by an opioid, barbiturate and/or benzodiazepine in a selected human
patient population, comprising: selecting a population of human
patients being treated with an opioid, barbiturate and/or
benzodiazepine and thereby at risk of respiratory depression;
administering to the selected patient population a therapeutically
effective dose of a 5-HT.sub.4 agonist; and allowing the 5-HT.sub.4
agonist to stimulate 5-HT.sub.4 receptors in the selected patient
population, thereby reducing incidence of respiratory depression
caused by the opioid, barbiturate and/or benzodiazepine in the
patient population.
4. A method of reducing the likelihood of respiratory depression
caused by an opioid, barbiturate and/or benzodiazepine in a human
patient, comprising: selecting a human patient being treated with
an opioid, barbiturate and/or benzodiazepine and thus at risk of
respiratory depression; administering to the patient a
therapeutically effective dose of a 5-HT.sub.4 agonist; and
allowing the 5-HT.sub.4 agonist to stimulate 5-HT.sub.4 receptors
in the patient, thereby reducing the likelihood of respiratory
depression in the patient.
5. The method of any of claim 1 wherein the respiratory depression
is intensified by co-ingestion or co-administration of alcohol or
other CNS depressants.
6. The method of any of claim 1, wherein the 5-HT.sub.4 agonist is
selected from the group consisting of fenfluramine, BIMU-8,
Cisapride, Mosapride, Prucalopride, Renzapride, RS-67506,
Tegaserod, Zacopride, Metoclopramide, and Sulpiride, or a
pharmaceutically acceptable salt thereof.
7. The method of claim 1, wherein the 5-HT.sub.4 agonist is
fenfluramine, or a pharmaceutically acceptable salt thereof; and
wherein fenfluramine is administered in a therapeutically effective
dose as an adjunctive therapeutic agent; and wherein the
therapeutically effective dose of fenfluramine is selected from the
group consisting of 0.2 mg/kg/day to 0.08 mg/kg/day up to a 30 mg
maximum daily dose.
8. The method of claim 7, wherein the therapeutically effective
dose of fenfluramine is administered in an oral liquid dosage
form.
9. The method of claim 1, wherein the opioid is selected from the
group consisting of buprenorphine, codeine, Demerol, Duramorph,
fentanyl (Actiq, Duragesic), heroin, hydrocodone (Zohydro ER),
hydromorphone (Dilaudid, Exalgo), Lorcet, methadone, morphine
(Avinza, Kadian, MSIR, MSContin), Norco, oxycodone (OxyContin,
Roxicodone), oxymorphone (Opana ER), Palladone, Percodan, Percocet,
remifentanil, Roxanol, Sublimaze, sufentanil (R30730, Sufenta),
tapentadol (Nucynta, Palexia, Tapal), Tylox, and Vicodin, or a
pharmaceutically acceptable salt thereof.
10. The method of claim 1, wherein the opioid is fentanyl (Actiq,
Duragesic), remifentanil, or sufentanil (R30730, Sufenta), or a
pharmaceutically acceptable salt thereof.
11. The method of claim 1, wherein the 5-HT.sub.4 agonist has a
characteristic selected from the group consisting of: (a) inactive
at the 5-HT.sub.2B receptor; (b) a neutral agonist of the
5-HT.sub.2B receptor; and (c) an inverse agonist of the 5-HT.sub.2B
receptor 5-HT.sub.2B receptor.
12. The method of claim 1, wherein the patient exhibits a
significantly higher responder rate compared with placebo, the
method further comprising: repeating the administering over a
period of days until the patient exhibits a .gtoreq.40% reduction
from baseline in occurrence of respiratory depression.
13. The method of claim 12, wherein the patient exhibits at least a
.gtoreq.50% reduction in occurrence of respiratory depression.
14. The method of claim 12, wherein the patient exhibits at least a
.gtoreq.75% reduction in occurrence of respiratory depression.
15. The method of claim 12, wherein the patient exhibits at least a
.gtoreq.90% reduction in occurrence of respiratory depression.
16. The method of claim 12, wherein the patient completely free of
an occurrence of respiratory depression.
17. The method of claim 12, wherein the 5-HT.sub.4 agonist is
fenfluramine or a pharmaceutically acceptable salt thereof.
18. A method of increasing the safety of administering
benzodiazepines or barbiturates to a patient suffering from
epilepsy, comprising administering an effective dose of a
5-HT.sub.4 agonist along with the benzodiazepine or barbiturate,
thereby lowering a risk of respiratory depression in the
patient.
19. The method of claim 18 wherein the 5-HT.sub.4 agonist is
administered prior to dosing with a benzodiazepine or
barbiturate.
20. The method of claim 18 wherein the 5-HT.sub.4 agonist is
administered at substantially the same time as dosing with a
benzodiazepine or barbiturate.
21. The method of claim 18 wherein the benzodiazepine or
barbiturate is selected from the group consisting of those drugs
appearing in Table 1.
22. The method of claim 18 wherein the 5-HT.sub.4 agonist is
fenfluramine.
23. A method of lowering a risk of respiratory depression
associated with concomitant use of (i) an opioid and (ii) a
barbiturate and/or benzodiazepine, comprising administering an
effective dose of fenfluramine along with the opioid and the
benzodiazepine and/or barbiturate, thereby lowering the risk of
respiratory depression in the patient.
Description
FIELD
[0001] The present invention relates generally to the therapeutic
treatment of a subject at risk of or undergoing respiratory
distress, such as is induced by opiates, barbiturates, and
benzodiazepines. More specifically, the invention relates to the
use of a 5-HT.sub.4 agonist (e.g., fenfluramine) as a therapeutic
agent, and to methods of its use to treat human patients undergoing
or at risk of respiratory depression.
INTRODUCTION
[0002] Opioids are substances, both natural and synthetic, that
bind to opioid receptors in the brain (including antagonists).
There are several receptor subtypes in this family, of which the
more characterized are the delta, kappa and mu receptors. The delta
and .mu..sub.2 subtypes may modulate .mu.-opioid receptor-mediated
respiratory depression.
[0003] Opiates are alkaloid compounds naturally found in the opium
poppy plant Papaver somniferum. The psychoactive compounds found in
the opium plant include morphine, codeine, and thebaine. There are
also purely synthetic opioids such as, for example, tramadol
(Ultram) and fentanyl (Actiq, Sublimaze) among others which are
opioid-like medications.
[0004] All opioids, like opiates, are considered drugs of high
abuse potential and are listed on various "Substance-Control
Schedules" under the Uniform Controlled Substances Act of the
United States of America. In 2013, between 13 and 20 million people
used opiates recreationally (0.3% to 0.4% of the global population
between the ages of 15 and 65) ("Status and Trend Analysis of
Illicit [sic] Drug Markets." World Drug Report 2015).
[0005] By way of example, thebaine (paramorphine), also known as
codeine methyl enol ether, is an opiate alkaloid. A minor
constituent of opium, thebaine is chemically similar to both
morphine and codeine, but has stimulatory rather than depressant
effects. While thebaine is not used therapeutically, it is the main
alkaloid extracted from Papaver bracteatum (Iranian poppy) and can
be converted industrially into a variety of compounds, including
oxycodone, oxymorphone, nalbuphine, naloxone, naltrexone,
buprenorphine and etorphine. Butorphanol can also be derived from
thebaine.
[0006] Sufentanil (R30730, brand name Sufenta) is a synthetic
opioid analgesic drug approximately 5 to 10 times more potent than
its parent drug, fentanyl, and 500 times as potent as morphine.
[0007] Tapentadol (brand names: Nucynta, Palexia and Tapal) is a
centrally acting opioid analgesic of the benzenoid class with a
dual mode of action as an agonist of the .mu.-opioid receptor and
as a norepinephrine reuptake inhibitor (NRI). Analgesia occurs
within 32 minutes of oral administration, and lasts for 4-6
hours.
[0008] Opioids are widely used analgesics in anesthesiology.
However, opioids also have serious adverse effects, such as
depression of breathing. In fact, many different drugs have been
found to be associated with increased risk of respiratory
depression. Strong opioids (e.g., fentanyl, heroin, or morphine),
some barbiturates, and some benzodiazepines (e.g., short acting
ones and alprazolam) are known for depressing respiration.
Overdosing on these drugs can cause an individual to cease
breathing entirely (go into respiratory arrest) which is rapidly
fatal without treatment.
[0009] Furthermore, concomitant use of benzodiazepines and opioids
may result in profound sedation, respiratory depression, coma, and
death. Thus, physicians are typically instructed not to prescribe
the two together, to reserve concomitant prescribing of these drugs
for use only in patients for whom alternative treatment options are
inadequate and/or to limit dosages and durations to the minimum
required and follow patients for signs and symptoms of respiratory
depression and sedation.
[0010] Although the list below is not comprehensive, it is believed
to include several barbiturates, benzodiazepines, opiates and other
drugs which are widely prescribed and/or used recreationally.
TABLE-US-00001 TABLE 1 Common Drugs (e.g., Barbiturates and
Benzodiazepines, Opiates, etc.) Associated with Risk of Respiratory
Depression Drug class Generic Name Trade Name Barbiturate
amobarbital sodium Amytal Sodium aprobarbital, aprobarbitone
Oramon, Somnifaine, Allonal, Alurate butobarbital, butabarbital,
Butalan, Butisol, Butisol sodium, Buticaps, Sarisol butabarbital
sodium methylophenobarbital, Mebaral, Phemiton, Prominal,
Mephyltaletten mephobarbital, mephobarbitone metharbital, endiemal,
Gemonil metharbitone, methobarbitone methohexital, methohexitone
Brietal, Brevital pentothal Thiopental sodium phenobarbital,
pentobarbital, Luminal, Nembutal, Nembutal sodium, Solfoton
pentobarbitone primidone, Lepsiral, Mysoline, Resimatil, Primaclone
desoxyphenobarbital, desoxyphenobarbitone secobarbital Seconal
thiamylal Surital Benzodiazepine alprazolam Xanax, Xanax XR
carbamazepine Carbatrol, Epitol, Equetro, Tegretol chlordiazepoxide
Librium clobazam Frisium, Onfi clonazepam Klonopin clorazepate
Tranxene diazepam Diastat, Diastat Acudial, Diazepam Intensol,
Valium estazolam Prosom ethyl loflazepate Meilax, Ronlax, Victan
flunitrazepam Rohypnol lorazepam Ativan oxazepam Zaxopam, Serax
temazepam Restoril triazolam Halcion Other tramadol Ultram, Zytram,
Conzip gabapentin Gralise, Horizant, Neurontin, Gabarone pregablin
Lyrica ketamine Ketalar fosphenytoin Cerebyx Phenytoin,
diphenylhydantoin Dilantin, Phenytek, and Epanutin Mephenytoin,
5-Ethyl-3- Mesantoin Methyl-5-Phenylhydantoin, Mefenetoin, Methoin,
Methyl Phenetoin, Phenantoin, Phenetoin Methyl mesuximide,
methsuximide Petinutin ethosuximide Zarontin felbamate Felbatol
eslicarbazepine acetate Aptiom oxcarbazepine Trileptal, Oxtellar
perampanel Fycompa Ezogabine, retigabine Potiga tiagabine Gabitril
topirimate Topamax valproate, valproic acid, 2- Absenor, Convulex,
Depakene, Depakine, Depalept, propylvaleric acid, sodium Deprakine,
Divalproex, Encorate, Epival, Epilim, valproate, valproate Stavzor,
Valcote, Valpakine, Orfiril semisodium vigabatrin Sabril lacosamide
Vimpat zonisamide Zonegran acetaminophen/butalbital Anolor 300,
Bupap, Capacet, Cephadyn, Dolgic LQ, Esgic, Esgic-Plus, Ezol,
Fioricet, Geone, Margesic, Orbivan CF, Phrenilin, Phrenilin Forte,
Zebutal acetaminophen/hydrocodone Vicodin, Norco, Lorcet
[0011] For example, clobazam is in a class of medications called
benzodiazepines. Clobazam (brand names Frisium, Urbanol, Onfi and
Tapclob) has been marketed as an anxiolytic since 1975 and an
anticonvulsant since 1984. Overdose and intoxication with clobazam
can lead to CNS depression, associated with drowsiness, confusion
and lethargy, sometimes progressing to ataxia, respiratory
depression, hypotension and even coma or death. The risk of a fatal
outcome is increased in cases of combined poisoning with other CNS
depressants, including alcohol. (Wildin, et al., (1990).
"Respiratory and sedative effects of clobazam and clonazepam in
volunteers." British Journal of Clinical Pharmacology.
29(2):169-77).
[0012] Opioid-induced respiratory depression is dangerous and often
fatal. Furthermore, an optimum treatment for respiratory depression
has yet to be established. Thus, there is a dire, long felt, but
previously unmet need for therapeutic agents effective in treating,
preventing or ameliorating the respiratory depression that occurs
in subjects taking opioids, barbiturates and/or benzodiazepines.
The present disclosure has applicability to treatment, prevention,
or amelioration of respiratory depression often induced by opioids,
barbiturates and/or benzodiazepines, whether administered as
therapeutic agents by doctors or hospitals, or taken illicitly by
drug abusers or addicts.
BRIEF SUMMARY
[0013] Provided in the present disclosure is the surprising
discovery that certain serotonin receptors (also known as
5-hydroxytryptamine (5-HT) receptors) mediate the action of
fenfluramine (FFA) in blocking seizure-induced sudden death in
mice. Specifically, agonists of the 5-HT.sub.4 receptor are useful
in treating, reducing and/or ameliorating the risk or occurrence of
respiratory depression associated with use of one or more opioids,
barbiturates and/or benzodiazepines in a human patient.
[0014] The methods disclosed herein are generally useful for
treating, preventing or ameliorating respiratory depression and/or
seizure-induced respiratory arrest (S-IRA) associated with use of
one or more opioids, barbiturates and/or benzodiazepines.
[0015] In some aspects, provided herein is a method of method of
treating respiratory depression caused by one or more opioids,
barbiturates and/or benzodiazepines in a human patient, comprising
administering to the patient a therapeutically effective dose of a
5-hydroxytryptamine receptor 4 agonist (5-HT.sub.4 agonist), and
allowing the 5-HT.sub.4 agonist to stimulate 5-HT.sub.4 receptors
in the patient, thereby treating respiratory depression caused by
the opioid in the patient.
[0016] In some aspects, provided herein is a method of preventing
respiratory depression and/or seizure-induced respiratory arrest
(S-IRA) in a human patient being treated with an opioid, comprising
administering to the patient a therapeutically effective dose of a
5-HT.sub.4 agonist, and allowing the 5-HT.sub.4 agonist to
stimulate 5-HT.sub.4 receptors in the patient, thereby preventing
respiratory depression and/or S-IRA in the patient being treated
with the opioid.
[0017] In some aspects, provided herein is a method of reducing
incidence of respiratory depression caused by an opioid in a
selected human patient population, comprising selecting a
population of human patients being treated with an opioid and
thereby at risk of respiratory depression, administering to the
selected patient population a therapeutically effective dose of a
5-HT.sub.4 agonist, and allowing the 5-HT.sub.4 agonist to
stimulate 5-HT.sub.4 receptors in the selected patient population,
thereby reducing incidence of respiratory depression caused by the
opioid in the patient population.
[0018] In some aspects, provided herein is a method of reducing
likelihood of respiratory depression caused by an opioid in a human
patient, comprising selecting a human patient being treated with an
opioid and thereby at risk of respiratory depression, administering
to the patient a therapeutically effective dose of a 5-HT.sub.4
agonist, and allowing the 5-HT.sub.4 agonist to stimulate
5-HT.sub.4 receptors in the patient, thereby reducing the
likelihood of respiratory depression caused by an opioid in the
patient in the patient.
[0019] In some aspects, provided herein is a method of stimulating
one or more 5-HT.sub.4 receptors in the brain of a patient
undergoing treatment with an opioid, wherein the patient is at risk
of respiratory depression, comprising administering a
therapeutically effective dose of a 5-HT.sub.4 agonist to the
patient undergoing treatment with an opioid, and allowing the
5-HT.sub.4 agonist to stimulate 5-HT.sub.4 receptors in the brain
of the patient undergoing treatment with an opioid, thereby
reducing the risk of respiratory depression in the patient.
[0020] In some aspects, provided herein is a method of reducing
respiratory depression in a patient treated with an opioid,
comprising administering to the patient a therapeutically effective
dose of a 5-hydroxytryptamine receptor 4 agonist (5-HT.sub.4
agonist), and allowing the 5-HT.sub.4 agonist to stimulate
5-HT.sub.4 receptors in the patient, and thereby reducing
respiratory depression in the patient treated with the opioid.
[0021] In some aspects, provided herein is a method of reducing
opioid-induced respiratory depression in a human patient,
comprising administering to the patient suffering from
opioid-induced respiratory depression a therapeutically effective
dose of a 5-HT.sub.4 agonist, and allowing the 5-HT.sub.4 agonist
to stimulate 5-HT.sub.4 receptors in the patient, thereby
preventing respiratory depression in the patient being treated with
opioids.
[0022] In some aspects, provided herein is a method of increasing
the safety of administering benzodiazepines or barbiturates to a
patient suffering from epilepsy, comprising administering an
effective dose of a 5-HT.sub.4 agonist along with the
benzodiazepine or barbiturate, thereby lowering a risk of
respiratory depression in the patient.
[0023] In some aspects, provided herein is a method of lowering a
risk of respiratory depression associated with concomitant use of
(i) an opioid and (ii) a barbiturate and/or benzodiazepine,
comprising administering an effective dose of a 5-HT.sub.4 agonist
along with the opioid and the benzodiazepine and/or barbiturate,
thereby lowering the risk of respiratory depression in the
patient.
[0024] In some embodiments of the method, the 5-HT.sub.4 agonist is
selected from the group consisting of fenfluramine, BIMU-8,
Cisapride, Mosapride, Prucalopride, Renzapride, RS-67506,
Tegaserod, Zacopride, Metoclopramide, and Sulpiride or a
pharmaceutically acceptable salt thereof.
[0025] In some embodiments of the method, the 5-HT.sub.4 agonist is
fenfluramine, or a pharmaceutically acceptable salt thereof.
[0026] In some embodiments, the fenfluramine is administered as an
adjunctive therapeutic agent.
[0027] In some embodiments, the therapeutically effective dose of
fenfluramine is selected from the group consisting of 0.1 mg/kg/day
to 1.0 mg/kg/day up to a 30 mg maximum daily dose.
[0028] In some embodiments of the method, an effective dose is less
than 10.0 mg/kg/day, or less than 1.0 mg/kg/day, or approximately
0.8 mg/kg/day, or approximately 0.5 mg/kg/day, or approximately 0.2
mg/kg/day, or approximately 0.1 mg/kg/day; or approximately 0.01
mg/kg/day. In some embodiments of the method, the effective dose of
fenfluramine is 0.5 mg/kg/day. In some embodiments of the method,
the effective dose of fenfluramine is between 0.01 mg/kg/day and
0.8 mg/kg/day.
[0029] In some embodiments of the method, the therapeutically
effective dose of fenfluramine is administered in a dosage form
selected from the groups consisting of oral, injectable,
transdermal, inhaled, nasal, rectal, vaginal and parenteral.
[0030] In some embodiments of the method, the therapeutically
effective dose of fenfluramine is administered in an oral liquid
dosage form.
[0031] In some embodiments, the dosage form is an oral composition
in an amount selected from the group consisting of 30 mg/day or
less, 20 mg/day or less, 10 mg/day or less and 5 mg/day or
less.
[0032] In some embodiments of the method, an effective dose of the
5-HT.sub.4 agonist is administered in a pharmaceutically acceptable
carrier.
[0033] In some embodiments of the method, the fenfluramine is
formulated with a pharmaceutically acceptable carrier.
[0034] In some embodiments of the method, the fenfluramine is the
sole (only) pharmaceutically active drug administered to the
patient.
[0035] In some embodiments of the method, the opioid is selected
from the group consisting of buprenorphine, codeine, Demerol,
Duramorph, fentanyl (Actiq, Duragesic), heroin, hydrocodone
(Zohydro ER), hydromorphone (Dilaudid, Exalgo), Lorcet, methadone,
morphine (Avinza, Kadian, MSIR, MSContin), Norco, oxycodone
(OxyContin, Roxicodone), oxymorphone (Opana ER), Palladone,
Percodan, Percocet, remifentanil, Roxanol, Sublimaze, sufentanil
(R30730, Sufenta), tapentadol (Nucynta, Palexia, Tapal), tramadol
(Ultram), Tylox, and Vicodin, or a pharmaceutically acceptable salt
thereof.
[0036] In some embodiments of the method, the opioid is fentanyl
(Actiq, Duragesic), remifentanil, or sufentanil (R30730, Sufenta),
or a pharmaceutically acceptable salt thereof.
[0037] In some embodiments of the method, the 5-HT.sub.4 agonist
further counteracts the intensifying effects of ethanol or other
CNS depressants on respiratory depression that are ingested or
present with the opiate, barbiturate or benzodiazepine that further
potentiate the respiratory depression.
[0038] In some embodiments of the method, the 5-HT.sub.4 agonist is
at least one of:
[0039] (a) inactive at the 5-HT.sub.2B receptor;
[0040] (b) a neutral agonist of the 5-HT.sub.2B receptor; and
[0041] (c) an inverse agonist of the 5-HT.sub.2B receptor
5-HT.sub.2B receptor.
[0042] In some embodiments, the patient exhibits a significantly
higher responder rate compared with placebo.
[0043] In some embodiments, the method further includes repeating
the administering over a period of days until the patient exhibits
a .gtoreq.40% reduction from baseline in occurrence of respiratory
depression.
[0044] In some embodiments, the patient exhibits at least a
.gtoreq.50% reduction in occurrence of respiratory depression.
[0045] In some embodiments, the patient exhibits at least a
.gtoreq.75% reduction in occurrence of respiratory depression.
[0046] In some embodiments, the patient exhibits at least a
.gtoreq.90% reduction in occurrence of respiratory depression.
[0047] In some embodiments, the patient is completely free of an
occurrence of respiratory depression.
[0048] In some embodiments, the patient is alive after two years
after first administration of the 5-HT.sub.4 agonist.
[0049] In some embodiments of the method, the 5-HT.sub.4 agonist is
in a formulation adapted to a dosage forms selected from the group
consisting of an oral dosage form, an intravenous dosage form,
rectal dosage form, subcutaneous dosage form, and a transdermal
dosage form.
[0050] In some embodiments of the method, the oral dosage form is
selected from the group consisting of a liquid, a suspension, a
tablet, a capsule, a lozenge, and a dissolving strip.
[0051] In some embodiments of the method, the 5-HT.sub.4 agonist is
administered prior to dosing with a benzodiazepine or
barbiturate.
[0052] In some embodiments of the method, the 5-HT.sub.4 agonist is
administered at substantially the same time as dosing with a
benzodiazepine or barbiturate.
[0053] In some embodiments of the method, the benzodiazepine or
barbiturate is selected from the group consisting of those drugs
appearing in Table 1.
[0054] In another aspect, the disclosure provides a kit comprising
a therapeutic agent, e.g., a 5-HT.sub.4 agonist, as used in any of
the methods disclosed herein, and instructions for use.
[0055] As shown above and as will be recognized by others skilled
in the art, the therapeutic agents provide the important advantage
that they are more effective and/or exhibit an improved safety
profile as compared to other therapeutic agents and methods
currently known in the art.
[0056] These and other objects, advantages, and features of the
invention will become apparent to those persons skilled in the art
upon reading the details of the therapeutic agents and methods of
using the same as are more fully described below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0057] The invention is best understood from the following detailed
description when read in conjunction with the accompanying
drawings. Included in the drawings are the following figures:
[0058] FIGS. 1A-1D: show the dose- and time-dependent effects of
fenfluramine (FFA) on incidence of tonic seizures and
seizure-induced respiratory arrest (S-IRA) in the DBA/1 mouse
model.
[0059] FIGS. 2A-2B: demonstrate that a 5-HT.sub.2 receptor
antagonist (Ritanserin) reversed the anticonvulsant effect of FFA
on seizures and S-IRA in DBA/1 mice.
[0060] FIGS. 3A-3B: demonstrate that a 5-HT.sub.3 receptor
antagonist (Ondansetron) did not reverse the anticonvulsant effects
of FFA on seizures or S-IRA in DBA/1 mice.
[0061] FIGS. 4A-4B: demonstrate that a 5-HT.sub.4 receptor
antagonist (GR125487) reversed the anticonvulsant and S-IRA
blocking effects of FFA in DBA/1 mice.
[0062] FIGS. 5A-5B: demonstrate that a 5-HT.sub.7 receptor
antagonist (SB269970) reversed the anticonvulsant effects of FFA in
DBA/1 mice.
[0063] FIG. 6: illustrates the mechanism believed to be involved in
the anticonvulsant and S-IRA blocking effects of FFA on various
5-HT receptors in the DBA/1 mouse model.
DETAILED DESCRIPTION
[0064] Before the present compositions and methods are described,
it is to be understood that this invention is not limited to the
particular formulations and methods described, as such can, of
course, vary. It is also to be understood that the terminology used
herein is for the purpose of describing particular embodiments
only, and is not intended to be limiting, since the scope of the
present invention will be limited only by the appended claims.
[0065] Where a range of values is provided, it is understood that
each intervening value, to the tenth of the unit of the lower limit
unless the context clearly dictates otherwise, between the upper
and lower limits of that range is also specifically disclosed. Each
smaller range between any stated value or intervening value in a
stated range and any other stated or intervening value in that
stated range is encompassed within the invention. The upper and
lower limits of these smaller ranges can independently be included
or excluded in the range, and each range where either, neither or
both limits are included in the smaller ranges is also encompassed
within the invention, subject to any specifically excluded limit in
the stated range. Where the stated range includes one or both of
the limits, ranges excluding either or both of those include limits
are also included in the invention.
[0066] Unless defined otherwise, all technical and scientific terms
used herein have the same meaning as commonly understood by one of
ordinary skill in the art to which this invention belongs. Although
any methods and materials similar or equivalent to those described
herein can be used in the practice or testing of the present
invention, the preferred methods and materials are now described.
All publications mentioned herein are incorporated herein by
reference to disclose and describe the methods and/or materials in
connection with which the publications are cited.
[0067] It must be noted that as used herein and in the appended
claims the singular forms "a," "an," and "the" include plural
referents unless the context clearly dictates otherwise.
[0068] Thus, for example, reference to "a formulation" includes a
plurality of such formulations and reference to "the method"
includes reference to one or more methods and equivalents thereof
known to those skilled in the art, and so forth.
[0069] The publications discussed herein are provided solely for
their disclosure prior to the filing of the present application.
Nothing herein is to be construed as an admission that the present
invention is not entitled to antedate such publication by virtue of
prior invention. Further, the dates of publication provided may be
different from the actual publication dates which may need to be
independently confirmed.
[0070] Fifteen years ago, it was reported that 5-HT.sub.4a
receptors are strongly expressed in respiratory neurons of the
brainstem, and that treatment of rats with the 5-HT.sub.4 receptor
agonist BIMU8 counteracted fentanyl-induced respiratory depression
(Manzke et al., 2003, Science. 301(5630):226-9; incorporated herein
by reference in its entirety).
[0071] Recently, we discovered that fenfluramine (FFA) acts at
specific 5-HT receptors, including the 5-HT.sub.4 receptor, to
block seizure-induced respiratory arrest (S-IRA) in the DBA/1 mouse
model of Sudden Unexpected Death in Epilepsy (SUDEP). Specific
serotonin receptor subtypes were found to mediate this action of
fenfluramine in blocking seizure-induced sudden death and
seizure-induced respiratory arrest (S-IRA).
[0072] The present disclosure is directed to the surprising
discovery that certain serotonin receptors (also known as
5-hydroxytryptamine (5-HT) receptors) mediate the action of
fenfluramine (FFA) in blocking seizure-induced sudden death and
seizure-induced respiratory arrest (S-IRA) in mice. Specifically,
agonists of the 5-HT.sub.4 receptor are useful in treating,
reducing and/or ameliorating the risk or occurrence of respiratory
depression associated with use of one or more opioids, barbiturates
and/or benzodiazepines in a human patient.
[0073] Recently it was discovered that the intractable seizures
characteristic of Dravet syndrome can be significantly reduced in
frequency and/or severity, and in some cases eliminated entirely,
by administering the drug 3-trifluoromethyl-N-ethylamphetamine
(hereinafter "fenfluramine"). See Ceulemans et. al., Successful use
of fenfluramine as an add-on treatment for Dravet Syndrome,
Epilepsia 53(7):1131-1139, 2012. Fenfluramine, is an amphetamine
derivative having the following structure:
##STR00001##
Structure 1
(R,S)--N-ethyl-1-[3-(trifluoromethyl)phenyl]propan-2-amine
[0074] Fenfluramine is a racemic mixture of two enantiomers,
dexfenfluramine and levofenfluramine, and has been reported to
increase the circulating levels of serotonin, a neurotransmitter
that regulates mood, appetite and other functions.
[0075] Serotonin (also known as "5-hydroxytryptamine" or "5-HT") is
a monoaminergic neurotransmitter believed to modulate numerous
sensory, motor and behavioral processes in the mammalian nervous
system. Diverse responses are elicited through the activation of a
large family of receptor subtypes. Of the many subtypes of
serotonin receptors, the 5-HT.sub.1B and 5-HT.sub.2C subtypes are
most strongly implicated in modulating feeding and body weight, and
these receptors are expressed in hypothalamic regions believed to
be involved in food intake regulation. Fenfluramine was known to
have high affinity for and activity at the 5-HT.sub.2A, 5-HT.sub.2B
and 5-HT.sub.2C receptor subtypes (Rothman et al, 2015), and
because 5-HT.sub.2C-agonists trigger appetite suppression,
fenfluramine was used for treating obesity by co-administering it
together with phentermine as part of the popular weight loss drug
combination treatment marketed as Fen-Phen (i.e.,
fenfluramine/phentermine). Fen-Phen was first marketed in the US in
1973 to prevent and treat obesity, but in 1997, Fen-Phen was
withdrawn from the US and global markets, as its use was associated
with the onset of cardiac valvulopathy and pulmonary
hypertension.
[0076] The adverse effects associated with the use of Fen-Phen as
an anorexic agent were believed to be attributable to the
interaction of fenfluramine's primary metabolite norfenfluramine
with the 5-HT.sub.2B receptor, the activation of which was
associated with cardiac valvulopathy. It was for this reason that
Fen-Phen was withdrawn from the market and is no longer indicated
for use in any therapeutic area.
[0077] Despite past cardiovascular safety concerns that arose when
high doses of fenfluramine were used for treatment of adult
obesity, attempts have been made to identify further therapeutic
uses for that product, while weighing the known cardiovascular
risks of fenfluramine against potential therapeutic benefits. The
present disclosure provides a new treatment option for reversing
respiratory depression often induced by opioids, barbiturates
and/or benzodiazepines.
[0078] One use for fenfluramine is the treatment, amelioration
and/or prevention of seizures, such as in epilepsy and epileptic
encephalopathies. Sudden Unexpected Death in Epilepsy (SUDEP) is a
major cause of increased premature mortality that disproportionally
affects young persons with epilepsy. Witnessed SUDEP cases often
observed generalized tonic-clonic seizures (GTC) leading to
respiratory and cardiac failure during post-ictal behavioral
depression (PID). The leading risk factors of SUDEP include male
sex, GTC, young age, and high seizure frequency. Approaches to
reducing SUDEP incidence include improved medication compliance,
nocturnal monitoring, mitigating respiratory compromise and
responsive neurostimulation (Devinsky et al., 2018, Epilepsia
59:555-561; Rugg-Gunn et al., Epilepsia 57 Suppl 1:26-34, 2016).
SUDEP is known to be associated with subtherapeutic levels of
antiepileptic drugs (AEDs) and addition of AEDs can reduce the
incidence of SUDEP in drug resistant epilepsy (George and Davis. J
Forensic Sci. 43:598-603, 1998; Ryvlin et al., 2013, Lancet Neurol.
12:966-77). Therefore, there is a vital need for add-on AEDs with
an indication for SUDEP prophylaxis.
[0079] DBA/1 mice are a widely-used rodent model that recapitulates
many aspects of human SUDEP. DBA/1 mice exhibit increased
susceptibility to seizure and seizure-induced respiratory arrest
and death (S-IRA) in response to electroconvulsive shock,
hyperthermia, convulsant drug and intense acoustic stimulation
(audiogenic seizures, AGSz) (Deckard et al., 1976, Developmental
psychobiology 9:17-24; Faingold, et al., 2011, Epilepsy Behav.
22:186-190; Faingold, et al., 2016, Epilepsy Behav. 64(Pt
A):166-170; Loscher et al., 2017, Epilepsy Behav. 73:214-235;
Maxson S. C., 1980, Epilepsia 21, 637-645). The AGSz in DBA/1 mice
comprise of GTC followed by S-IRA during PID. Serotonin
(5-hydroxytryptamine, 5-HT) is an important neurotransmitter
released during PID that modulates respiration (Murugesan et al.,
Epilepsia 59:e91-e97, 2018; Hilaire et al., 2010, Respir. Physiol.
Neurobiol. 174(1-2):76-88; Zhang et al., Neurobiology of disease
110:47-58).
[0080] Abbreviations used throughout this disclosure include:
[0081] 5-HT 5-hydroxytryptamine
[0082] AGSz Audiogenic seizures
[0083] FFA Fenfluramine, 5-HT release enhancer
[0084] GTC Generalized tonic-clonic seizures
[0085] i.p. intraperitoneal
[0086] N Number of animals
[0087] PID Post-ictal depression
[0088] SUDEP Sudden Unexpected Death in Epilepsy
[0089] S-IRA Seizure-induced respiratory arrest
[0090] SSRI Selective serotonin reuptake inhibitor
[0091] Provided in the present disclosure is the surprising
discovery that certain serotonin receptors (also known as
5-hydroxytryptamine (5-HT) receptors) mediate the action of
fenfluramine (FFA) in blocking seizure-induced sudden death in
mice. Specifically, agonists of the 5-HT.sub.4 receptor are useful
in treating, reducing and/or ameliorating the risk or occurrence of
respiratory depression associated with use of one or more opioids,
barbiturates and/or benzodiazepines in a human patient.
[0092] The methods disclosed herein are generally useful for
treating, preventing or ameliorating respiratory depression and/or
seizure-induced respiratory arrest (S-IRA) associated with use of
one or more opioids, barbiturates and/or benzodiazepines.
[0093] In some aspects, provided herein is a method of method of
treating respiratory depression caused by an opioid in a human
patient, comprising administering to the patient a therapeutically
effective dose of a 5-hydroxytryptamine receptor 4 agonist
(5-HT.sub.4 agonist), and allowing the 5-HT.sub.4 agonist to
stimulate 5-HT.sub.4 receptors in the patient, thereby treating
respiratory depression caused by the opioid in the patient.
[0094] In some aspects, provided herein is a method of preventing
respiratory depression and/or seizure-induced respiratory arrest
(S-IRA) in a human patient being treated with an opioid, comprising
administering to the patient a therapeutically effective dose of a
5-HT.sub.4 agonist, and allowing the 5-HT.sub.4 agonist to
stimulate 5-HT.sub.4 receptors in the patient, thereby preventing
respiratory depression and/or S-IRA in the patient being treated
with the opioid.
[0095] In some aspects, provided herein is a method of reducing
incidence of respiratory depression caused by an opioid in a
selected human patient population, comprising selecting a
population of human patients being treated with an opioid and
thereby at risk of respiratory depression, administering to the
selected patient population a therapeutically effective dose of a
5-HT.sub.4 agonist, and allowing the 5-HT.sub.4 agonist to
stimulate 5-HT.sub.4 receptors in the selected patient population,
thereby reducing incidence of respiratory depression caused by the
opioid in the patient population.
[0096] In some aspects, provided herein is a method of reducing
likelihood of respiratory depression caused by an opioid in a human
patient, comprising selecting a human patient being treated with an
opioid and thereby at risk of respiratory depression, administering
to the patient a therapeutically effective dose of a 5-HT.sub.4
agonist, and allowing the 5-HT.sub.4 agonist to stimulate
5-HT.sub.4 receptors in the patient, thereby reducing the
likelihood of respiratory depression caused by an opioid in the
patient in the patient.
[0097] In some aspects, provided herein is a method of stimulating
one or more 5-HT.sub.4 receptors in the brain of a patient
undergoing treatment with an opioid, wherein the patient is at risk
of respiratory depression, comprising administering a
therapeutically effective dose of a 5-HT.sub.4 agonist to the
patient undergoing treatment with an opioid, and allowing the
5-HT.sub.4 agonist to stimulate 5-HT.sub.4 receptors in the brain
of the patient undergoing treatment with an opioid, thereby
reducing the risk of respiratory depression in the patient.
[0098] In some aspects, provided herein is a method of reducing
respiratory depression in a patient treated with an opioid,
comprising administering to the patient a therapeutically effective
dose of a 5-hydroxytryptamine receptor 4 agonist (5-HT.sub.4
agonist), and allowing the 5-HT.sub.4 agonist to stimulate
5-HT.sub.4 receptors in the patient, and thereby reducing
respiratory depression in the patient treated with the opioid.
[0099] In some aspects, provided herein is a method of reducing
opioid-induced respiratory depression in a human patient,
comprising administering to the patient suffering from
opioid-induced respiratory depression a therapeutically effective
dose of a 5-HT.sub.4 agonist, and allowing the 5-HT.sub.4 agonist
to stimulate 5-HT.sub.4 receptors in the patient, thereby
preventing respiratory depression in the patient being treated with
opioids.
[0100] In some aspects, provided herein is a method of increasing
the safety of administering benzodiazepines or barbiturates to a
patient suffering from epilepsy, comprising administering an
effective dose of a 5-HT.sub.4 agonist along with the
benzodiazepine or barbiturate, thereby lowering a risk of
respiratory depression in the patient.
[0101] In some aspects, provided herein is a method of lowering a
risk of respiratory depression associated with concomitant use of
(i) an opioid and (ii) a barbiturate and/or benzodiazepine,
comprising administering an effective dose of a 5-HT.sub.4 agonist
along with the opioid and the benzodiazepine and/or barbiturate,
thereby lowering the risk of respiratory depression in the
patient.
[0102] In some embodiments of the method, the 5-HT.sub.4 agonist is
selected from the group consisting of fenfluramine, BIMU-8,
Cisapride, Mosapride, Prucalopride, Renzapride, RS-67506,
Tegaserod, Zacopride, Metoclopramide, and Sulpiride or a
pharmaceutically acceptable salt thereof.
[0103] In some embodiments of the method, the 5-HT.sub.4 agonist is
fenfluramine, or a pharmaceutically acceptable salt thereof.
[0104] In some embodiments, the fenfluramine is administered as an
adjunctive therapeutic agent.
[0105] In some embodiments, the therapeutically effective dose of
fenfluramine is selected from the group consisting of 0.2 mg/kg/day
to 0.08 mg/kg/day up to a 30 mg maximum daily dose.
[0106] In some embodiments of the method, an effective dose is less
than 10.0 mg/kg/day, or less than 1.0 mg/kg/day, or approximately
0.8 mg/kg/day, or approximately 0.5 mg/kg/day, or approximately 0.2
mg/kg/day, or approximately 0.1 mg/kg/day; or approximately 0.01
mg/kg/day. In some embodiments of the method, the effective dose of
fenfluramine is 0.5 mg/kg/day. In some embodiments of the method,
the effective dose of fenfluramine is between 0.01 mg/kg/day and
0.8 mg/kg/day.
[0107] In some embodiments of the method, the therapeutically
effective dose of fenfluramine is administered in a dosage form
selected from the groups consisting of oral, injectable,
transdermal, inhaled, nasal, rectal, vaginal and parenteral.
[0108] In some embodiments of the method, the therapeutically
effective dose of fenfluramine is administered in an oral liquid
dosage form.
[0109] In some embodiments, the dosage form is an oral composition
in an amount selected from the group consisting of 30 mg/day or
less, 20 mg/day or less, 10 mg/day or less and 5 mg/day or
less.
[0110] In some embodiments of the method, an effective dose of the
5-HT.sub.4 agonist is administered in a pharmaceutically acceptable
carrier.
[0111] In some embodiments of the method, the fenfluramine is
formulated with a pharmaceutically acceptable carrier.
[0112] In some embodiments of the method, the fenfluramine is the
sole (only) pharmaceutically active drug administered to the
patient.
[0113] In some embodiments of the method, the opioid is selected
from the group consisting of buprenorphine, codeine, Demerol,
Duramorph, fentanyl (Actiq, Duragesic), heroin, hydrocodone
(Zohydro ER), hydromorphone (Dilaudid, Exalgo), Lorcet, methadone,
morphine (Avinza, Kadian, MSIR, MSContin), Norco, oxycodone
(OxyContin, Roxicodone), oxymorphone (Opana ER), Palladone,
Percodan, Percocet, remifentanil, Roxanol, Sublimaze, sufentanil
(R30730, Sufenta), tapentadol (Nucynta, Palexia, Tapal), Tylox, and
Vicodin, or a pharmaceutically acceptable salt thereof.
[0114] In some embodiments of the method, the opioid is fentanyl
(Actiq, Duragesic), remifentanil, or sufentanil (R30730, Sufenta),
or a pharmaceutically acceptable salt thereof.
[0115] In some embodiments, the method further comprises
administering to the patient an effective dose of clobazam or a
pharmaceutically acceptable salt thereof.
[0116] In some embodiments of the method, the 5-HT.sub.4 agonist is
at least one of:
[0117] (a) inactive at the 5-HT.sub.2B receptor;
[0118] (b) a neutral agonist of the 5-HT.sub.2B receptor; and
[0119] (c) an inverse agonist of the 5-HT.sub.2B receptor
5-HT.sub.2B receptor.
[0120] In some embodiments, the patient exhibits a significantly
higher responder rate compared with placebo.
[0121] In some embodiments, the method further includes repeating
the administering over a period of days until the patient exhibits
a .gtoreq.40% reduction from baseline in occurrence of respiratory
depression.
[0122] In some embodiments, the patient exhibits at least a
.gtoreq.50% reduction in occurrence of respiratory depression.
[0123] In some embodiments, the patient exhibits at least a
.gtoreq.75% reduction in occurrence of respiratory depression.
[0124] In some embodiments, the patient exhibits at least a
.gtoreq.90% reduction in occurrence of respiratory depression.
[0125] In some embodiments, the patient is completely free of an
occurrence of respiratory depression.
[0126] In some embodiments, the patient is alive after two years
after first administration of the 5-HT.sub.4 agonist.
[0127] In some embodiments of the method, the 5-HT.sub.4 agonist is
in a formulation adapted to a dosage forms selected from the group
consisting of an oral dosage form, an intravenous dosage form,
rectal dosage form, subcutaneous dosage form, and a transdermal
dosage form.
[0128] In some embodiments of the method, the oral dosage form is
selected from the group consisting of a liquid, a suspension, a
tablet, a capsule, a lozenge, and a dissolving strip.
[0129] In some embodiments of the method, the 5-HT.sub.4 agonist is
administered prior to dosing with a benzodiazepine or
barbiturate.
[0130] In some embodiments of the method, the 5-HT.sub.4 agonist is
administered at substantially the same time as dosing with a
benzodiazepine or barbiturate.
[0131] In some embodiments of the method, the benzodiazepine or
barbiturate is selected from the group consisting of those drugs
appearing in Table 1.
[0132] In another aspect, the disclosure provides a kit comprising
a therapeutic agent, e.g., a 5-HT.sub.4 agonist, as used in any of
the methods disclosed herein, and instructions for use.
[0133] Thus, the disclosure provides methods which employ certain
therapeutic agents useful in treating patients having respiratory
depression and/or seizure-induced respiratory arrest (S-IRA), who
require treatment. The disclosure further provides methods which
employ certain therapeutic agents useful in preventing, treating or
ameliorating symptoms associated with respiratory depression and/or
seizure-induced respiratory arrest (S-IRA) in a human patient being
treated with at least one opioid, barbiturate and/or
benzodiazepine.
[0134] The methods disclosed herein comprise administering a
therapeutically effective amount of one or more therapeutic agents.
A number of therapeutic agents can be employed in the methods of
the present invention. In some embodiments, the therapeutic agent
is a 5-HT.sub.4 receptor agonist. In some embodiments, the
therapeutic agent is active at one or more targets, or two or more
targets, or three or more targets, or four or more targets, or five
or more targets, or more. In some embodiments, the therapeutic
agent activates the 5-HT.sub.4 receptor. In some embodiments, the
therapeutic agent activates the 5-HT.sub.2 receptor. In some
embodiments, the therapeutic agent activates the 5-HT.sub.7
receptor.
[0135] The present disclosure provides a method of preventing,
treating or ameliorating symptoms associated with respiratory
depression and/or seizure-induced respiratory arrest (S-IRA) in a
human patient being treated with at least one opioid, barbiturate
and/or benzodiazepine, wherein the therapeutic agent is a compound
that is active at one or more targets. In some aspects, the
therapeutic agent comprises a compound that activates a 5-HT
receptor protein such as an agonist of the 5-HT.sub.4 receptor.
[0136] The disclosure further provides pharmaceutical compositions
comprising one or more of the therapeutic agents disclosed herein
for use in the methods of the invention. In some embodiments, the
pharmaceutical compositions are formulations adapted to one or more
dosage forms comprising an oral dosage form, an intravenous dosage
form, rectal dosage form, subcutaneous dosage form, and a
transdermal dosage form. In particular embodiments, the oral dosage
forms are selected from the group consisting of a liquid, a
suspension, a tablet, a capsule, a lozenge, and a dissolving strip.
In one embodiment, the transdermal dosage form is a patch.
[0137] The disclosure further provides methods of preventing,
treating or ameliorating one or more symptoms of respiratory
distress, respiratory depression and/or seizure-induced respiratory
arrest (S-IRA) associated with the use of opioids, barbiturates,
and/or benzodiazepines.
[0138] In one embodiment, the method may also involve a patient
being treated for status epilepticus. Status Epilepticus is a
severe and intractable condition categorized as a medical emergency
requiring immediate medical intervention, typically involving
hospitalization. Status Epilepticus can be fatal. It can also be
associated with cerebral hypoxia, possibly leading to damage to
brain tissue.
[0139] In one embodiment, the disclosure provides methods of
preventing, or reducing the incidence (frequency) of respiratory
depression, seizure-induced respiratory arrest (S-IRA) or Sudden
Unexpected Death in Epilepsy (SUDEP) in a population of human
patients also being treated with at least one opioid, barbiturate
and/or benzodiazepine. In some embodiments, the patient is
obese.
[0140] Opioids
[0141] A non-exhaustive list of opioid includes, but is not limited
to, buprenorphine, codeine, Demerol, Duramorph, fentanyl (Actiq,
Duragesic), heroin, hydrocodone (Zohydro ER), hydromorphone
(Dilaudid, Exalgo), methadone, morphine (Avinza, Kadian, MSIR,
MSContin), oxycodone (OxyContin, Roxicodone), oxymorphone (Opana
ER), Palladone, Percodan, Percocet, remifentanil, Roxanol,
Sublimaze, sufentanil (R30730, Sufenta), tapentadol (Nucynta,
Palexia, Tapal), Tylox, and Vicodin, or pharmaceutically acceptable
salts thereof.
[0142] Opioid-containing pharmaceutical compositions used as pain
medications include acetaminophen/hydrocodone (Vicodin, Norco,
Lorcet); these may also cause respiratory depression.
[0143] Another pain medication that is associated with respiratory
distress is gabapentin. Gabapentin (Neurontin) is a medication used
to treat epilepsy (specifically partial seizures), neuropathic
pain, hot flashes, and restless legs syndrome. Gabapentin has been
associated with a rare risk of severe respiratory depression even
without concomitant opioid medicines. Patients with compromised
respiratory function, respiratory or neurological disease, renal
impairment, concomitant use of central nervous system (CNS)
depressants, and elderly people might be at higher risk of
experiencing severe respiratory depression. Dose adjustments might
be necessary in these patients.
[0144] Gabapentin is a gabapentinoid: it has a structure similar to
the inhibitory neurotransmitter .gamma.-aminobutyric acid (GABA);
however, it crosses the blood-brain barrier more easily. It acts by
inhibiting certain calcium channels. Gabapentinoids, also known as
.alpha.2.delta. ligands, are a class of drugs that are derivatives
of the inhibitory neurotransmitter .gamma.-aminobutyric acid (GABA)
(i.e., GABA analogues) which block .alpha.2.delta.
subunit-containing voltage-dependent calcium channels (VDCCs). This
site has been referred to as the gabapentin receptor
(.alpha.2.delta. subunit), as it is the target of the drugs
gabapentin and pregabalin.
[0145] Clinically-used gabapentinoids include gabapentin and
pregabalin as well as a gabapentin prodrug, gabapentin enacarbil.
In addition, phenibut has been found to act as a gabapentinoid in
addition to its action of being a GABA.sub.B receptor agonist.
Another analogue, mirogabalin, is in clinical trials, but has not
yet been approved. Other gabapentinoids which are used in
scientific research but have not been approved for medical use
include atagabalin, 4-methylpregabalin and PD-217,014.
[0146] Barbiturates
[0147] Barbiturates are a class of drugs called central nervous
system (CNS) depressants. When taken as prescribed, barbiturates
help people sleep or with symptoms of anxiety. However, abuse of
these medications can have fatal consequences. Because barbiturates
are highly addictive, they present large risk of abuse and
overdose.
[0148] The action of barbiturates on the CNS, directly affects
nerve endings in the smooth muscles, lowering heart rate,
respiration, and blood pressure. Long term and/or excessive use of
barbiturates may result in respiratory depression. In the brain,
barbiturates interact with neural channels and transmitters,
inhibiting required responses, and quickly, with repeated use,
tolerance occurs requiring more and more of the drug, to achieve
desired results. Because barbiturates cross the `brain-barrier`
easily and readily dissolve into body fat, they will reenter the
blood stream at different rates depending on various factors (such
as body metabolism, other drugs already in system) or type of
barbiturate used. Also, the liver helps metabolize this drug into
soluble components, as it does for alcohol; overuse can cause
hepatitis. These results makes use of this drug extremely
dangerous, as its active levels in a user's body are very difficult
to determine, and overdose is extremely likely, especially when
combined with alcohol, other drugs, or opiates.
[0149] Barbiturates, categorically opposite to amphetamines
(stimulants), act on the CNS (central nervous system) as a
sedative-hypnotic drug, essentially `depressing` its function
within body and brain. Like amphetamines, barbiturates were
synthesized near the turn of the 20th century, the first derivative
being, Barbital, (brand names, Veronal or Medinal), developed by
chemists at Bayer pharmaceuticals, in Germany, in 1903, soon
followed by Phenobarbital, (Luminal), in 1912. Since then, with
over 2500 derivatives (compounds) created, barbiturates are
typically classified according to the `speed of onset,` and
`duration of action,` starting with the `ultra-short acting` group
used in anesthesia, followed by the `short/intermediate acting`
group, used in anesthesia, and to calm and sedate, (now,
benzodiazepines are usually applied), and lastly, the `long-acting`
barbiturates, where Phenobarbital is placed, with a half-life of 92
hours (almost 4 days), sometimes prescribed for convulsions Like
amphetamines, barbiturates, went unchecked for nearly fifty years
being readily prescribed for tension, anxiety, insomnia, and
extreme behavioral reactions. In the 1950's, the medical community
ultimately acknowledged that serious mental and physical health
risks could be associated with this depressant--life-threatening
reactions when combined with other drugs; rapid tolerance and
addiction; potential for lethal overdose.
[0150] Barbiturates are classified in four broad groups:
ultra-short acting, short acting, intermediate acting and long
acting. Ultra-short acting barbiturates are typically used in
anesthesia, injected intravenously, and produce anesthetic results
in one minute or less. Short acting to intermediate acting
barbiturates achieve results in 15 to 40 minutes. Long acting
barbiturates take effect in about an hour, and last about 12
hours.
[0151] Barbiturates--Brand Names: [0152] Allonal (Aprobarbital or
aprobarbitone), sold as Oramon, Somnifaine, and Allonal [0153]
Amytal Sodium (Amobarbital) [0154] Brevital (Methohexital) [0155]
Butabarb [0156] Butalan [0157] Buticaps [0158] Butisol Sodium
(Butobarbital) [0159] Luminal (Phenobarbital) [0160] Mebaral
(Mephobarbital) [0161] Mephyltaletten [0162] Nembutal [0163]
Nembutal Sodium (Phenobarbital) [0164] Oramon (Aprobarbital or
aprobarbitone), [0165] Pentothal (Thiopental sodium) [0166]
Phemiton [0167] Prominal (Methylophenobarbital) [0168] Sarisol
[0169] Seconal (Secobarbital) [0170] Somnifaine (Aprobarbital or
aprobarbitone), [0171] Surital (Thiamylal)
[0172] Generic Names: [0173] Amobarbital sodium [0174] Aprobarbital
[0175] Butabarbital [0176] Mephobarbital (methylophenobarbital)
[0177] Methohexital [0178] Pentobarbital [0179] Phenobarbital
[0180] Primidone (desoxyphenobarbital) [0181] Secobarbital [0182]
Thiopental sodium [0183] Thyamilal
[0184] Ultra Short-Acting: [0185] Brevital (Methohexital) [0186]
Pentothal (Thiopental sodium) [0187] Surital (Thiamylal)
[0188] Short-Acting to Intermediate Acting: [0189] Amytal
(Amobarbital) [0190] Alurate (Aprobarbital) [0191] Butisol
(Butobarbital) [0192] Nembutal (Phenobarbital) [0193] Seconal
(Secobarbital)
[0194] Long-Acting: [0195] Luminal (Phenobarbital) [0196] Mebaral
(Mephobarbital) [0197] Prominal (Methylophenobarbital)
[0198] Combination Barbiturates:
[0199] Combinations of Butalbital (barbiturate) and Acetaminophen
(pain reliever) are available in the following brand names: [0200]
Anolor 300 [0201] Bupap [0202] Capacet [0203] Cephadyn [0204]
Dolgic LQ [0205] Esgic [0206] Esgic-Plus [0207] Ezol [0208]
Fioricet [0209] Geone [0210] Margesic [0211] Orbivan CF [0212]
Phrenilin [0213] Phrenilin Forte [0214] Zebutal
[0215] Ketamine anesthesia following administration of a
barbiturate for preoperative anxiety and sedation has been reported
to produce profound respiratory depression. ("Barbiturates," in The
Pharmacological Basis of Therapeutics. 8th ed. New York, N.Y.
Pergamon Press, 1990, p. 1320, Gilman, A. G., T. W. Rall, A. S.
Nies and P. Taylor (eds.)).
[0216] Barbiturates and benzodiazepines can be used to treat
seizures and/or status epilepticus. Phenobarbital and other
barbiturates enhance inhibitory neurotransmission by binding to a
specific barbiturate site on the GABAA receptor. Intravenous
phenobarbital is used in the treatment of refractory status
epilepticus. Dosing can range from 10 to 20 mg/kg. The use of such
high doses of phenobarbital can cause respiratory depression and
depression of central cardiovascular function, which can contribute
to a "shock-like" condition requiring medical support. One
advantages of phenobarbital is a relatively rapid infusion time and
efficacy. The main drawbacks of phenobarbital are sedation,
respiratory depression, and hypotension.
[0217] Benzodiazepines
[0218] Benzodiazepines are man-made medications that cause mild to
severe depression of the nerves within the brain (central nervous
system) and sedation (drowsiness), and have largely replaced
barbiturates for treatment of anxiety, nervousness, muscle spasms,
seizures, sleeplessness, alcohol withdrawal, status epilepticus,
premenstrual syndrome, and panic and sleep disorders.
Benzodiazepines are also used as sedatives during surgery.
[0219] Seizures, anxiety, and other diseases that require
benzodiazepine treatment may be caused by excessive activity of
nerves in the brain. These drugs may work by enhancing the effects
of gamma-aminobutyric acid (GABA) in the brain. Gamma-aminobutyric
acid is a neurotransmitter, a chemical that nerves in the brain use
to send messages to one another. Gamma-aminobutyric acid reduces
the activity of nerves in the brain and increasing the effect of
GABA with a benzodiazepine, reduces brain activity. One serious
side effect of benzodiazepines is respiratory depression.
[0220] Acute toxicity and/or overdose of carbamazepine can effect
respiration, causing irregular breathing and/or respiratory
depression. A few cases of neonatal seizures and/or respiratory
depression associated with maternal Tegretol and other concomitant
anticonvulsant drug use have been observed. A few cases of neonatal
vomiting, diarrhea, and/or decreased feeding have also been
reported in association with maternal Tegretol use. These symptoms
may represent a neonatal withdrawal syndrome.
[0221] Similarly, diazepam or barbiturates may aggravate
respiratory depression (especially in children), hypotension, and
coma. However, barbiturates should not be used if drugs that
inhibit monoamine oxidase have also been taken by the patient
either in overdosage or in recent therapy (within 1 week).
[0222] Examples of oral benzodiazepines are: [0223] alprazolam
(Xanax, Xanax XR) [0224] clobazam (Onfi) [0225] clonazepam
(Klonopin) [0226] clorazepate (Tranxene) [0227] chlordiazepoxide
(Librium) [0228] diazepam (Valium, Diastat, Acudial, Diazepam
Intensol) [0229] estazolam (Prosom is a discontinued brand in the
US) [0230] lorazepam (Ativan) [0231] oxazepam (Zaxopam, Serax is a
discontinued brand in the US) [0232] temazepam (Restoril) [0233]
triazolam (Halcion)
[0234] Formulations of benzodiazepines
[0235] All oral benzodiazepines are available in tablet forms.
[0236] Alprazolam and clorazepate are available as extended-release
tablets. [0237] Alprazolam, clobazam, diazepam, and lorazepam are
available in oral liquid form. [0238] Alprazolam and clonazepam are
available in orally dissolving tablets. [0239] Chlordiazepoxide,
oxazepam, and temazepam are available in capsule form. [0240]
Diazepam also is available as a rectal gel (Diastat). [0241] Some
benzodiazepines are available for injection.
[0242] Epilepsy is associated with a two to three-fold increase in
premature mortality compared to the general population. A major
cause for this premature mortality increase is Sudden Unexpected
Death in Epilepsy (SUDEP), which occurs under benign circumstances
associated with terminal seizures but excludes injury, drowning,
trauma, toxicological effect, or status epilepticus-related deaths.
Most of the witnessed clinical cases of SUDEP reported generalized
seizures leading to respiratory and cardiac failure. The lifetime
risk of SUDEP among epileptics is estimated to be up to 8%, and
young persons with epilepsy are at a 24 or 28-fold higher risk of
sudden unexpected death than the general population. SUDEP ranks
second only to stroke among neurologic diseases, in terms of
potential years of life lost. The major pathophysiological
mechanisms that have been implicated in SUDEP include respiratory
failure, cardiac arrhythmia and cerebral shutdown. Because no
effective treatments are currently available, there is a pressing
need to find drugs that could prevent SUDEP. One measure of
severity of seizures is to count the frequency and/or duration.
[0243] Although estimates vary, some studies suggest that each year
there are about 1.16 cases of SUDEP for every 1,000 people with
epilepsy. Most, but not all, cases of SUDEP occur during or
immediately after a seizure, and although the exact cause is not
known, but the following is a list of factors that may play a
role:
[0244] Breathing. A seizure may cause a person to have pauses in
breathing due to apnea, or to airway obstruction. If these pauses
last too long, they can reduce the oxygen in the blood to a
life-threatening level. Heart rhythm. A seizure may cause a
dangerous heart rhythm or even heart failure. Other causes and
mixed causes. SUDEP may result from more than one cause or a
combination involving both breathing difficulty and abnormal heart
rhythm.
[0245] Three drugs that are especially effective for partial onset
seizures are vigabatrin, a selective and irreversible
GABA-transaminase inhibitor that greatly increases whole-brain
levels of GABA; tiagabine, a potent inhibitor of GABA uptake into
neurons and glial cells; and topiramate, which is believed to
produce its antiepileptic effect through several mechanisms,
including modification of Na.sup.+-dependent and/or
Ca.sup.2+-dependent action potentials, enhancement of GABA-mediated
Cl.sup.- fluxes into neurons, and inhibition of kainate-mediated
conductance at glutamate receptors of the AMPA/kainate type.
(Angehagen, et al., 2003, Neurochemical Research,
28(2):333-340).
[0246] Tiagabine (trade name Gabitril) is an anticonvulsant
medication used in the treatment of epilepsy. The drug is also used
off-label in the treatment of anxiety disorders and panic disorder.
Tiagabine overdose can produce neurological symptoms such as
lethargy, single or multiple seizures, status epilepticus, coma,
confusion, agitation, tremors, dizziness, dystonias/abnormal
posturing, and hallucinations, as well as respiratory depression,
tachycardia, hypertension, and hypotension. Overdose may be fatal
especially if the victim presents with severe respiratory
depression and/or unresponsiveness.
[0247] The DBA/1 mouse model of SUDEP exhibits a chronic,
abnormally high degree of susceptibility to fatal seizures
(seizure-induced death) induced by electroconvulsive shock,
hyperthermia, convulsant drug, and acoustic stimulation. High
intensity acoustic stimuli induce audiogenic seizures (AGSz), which
consist of tonic-clonic seizures followed by seizure-induced
respiratory arrest (S-IRA) that leads to death in the immediate
post-ictal period. Timely mechanical support of respiration can
consistently reverse S-IRA in this SUDEP model. (Faingold C L,
Randall M, Tupal S. 2010. DBA/1 mice exhibit chronic susceptibility
to audiogenic seizures followed by sudden death associated with
respiratory arrest. Epilepsy Behav. 17:436-40).
[0248] Studies have elucidated deficits in serotonin production and
receptor expression in DBA/1 mice. Many, but not all drugs that
enhance serotonergic neurotransmission, including selective
serotonin reuptake inhibitors (SSRIs), such as fluoxetine,
fluvoxamine and sertraline, or inhibit serotonin-norepinephrine
reuptake, such as venlafaxine and atomoxetine, have been reported
to prevent seizure-induced respiratory failure and death in DBA
mice in a dose-dependent manner. In contrast, serotonin antagonists
enhance the susceptibility of DBA mice to S-IRA. These findings and
additional studies on other SUDEP models have led to a serotonergic
hypothesis of SUDEP.
[0249] The serotonin hypothesis of SUDEP is based on findings that
treatments which modify serotonergic function significantly alter
susceptibility to seizure-induced sudden death in several epilepsy
models, including DBA/1 mice. Serotonergic abnormalities have also
recently been observed in human SUDEP.
[0250] As disclosed in US Patent Application publication
2018/0092864 (U.S. Ser. No. 15/717,159), the contents of which are
incorporated herein by reference in their entirety, methods are
provided for determining the binding characteristics, activity
(e.g., agonist or antagonist) selectivity, specificity and
pharmaceutical effects of fenfluramine and fenfluramine analogs at
various receptors, including (5-HT) receptor sub-types, (e.g.,
5-HT.sub.1A, 5-HT.sub.1D, 5-HT.sub.1E, 5-HT.sub.2A, 5-HT.sub.2C,
5-HT.sub.4, 5-HT.sub.5A and 5-HT.sub.7) as well as other receptors,
such as, for example, an adrenergic receptor (e.g., the beta-1 or
beta-2 adrenergic receptors), a muscarinic acetylcholine receptor
protein (e.g., the M1, M2, M3, M4 or M5 muscarinic acetylcholine
receptor), a chaperone protein (e.g., the Sigma 1 or Sigma-2
receptors), or a voltage-gated sodium channel subunit protein or a
subunit thereof (e.g., the Nav 1.1, Nav 1.2, Nav 1.3, Nav 1.4, Nav
1.5, Nav 1.6, or Nav 1.7) and/or a neurotransmitter transport
protein (e.g., a serotonin transporter (SET), a dopamine
transporter (DAT), and a norepinephrine transporter (NET)). Testing
in animal models led to the unexpected discovery that certain of
those candidates surprisingly reduced epileptiform activity in in
vivo animal models.
[0251] Recently, the contributions of several serotonin receptor
subtype(s) in mediating the action of fenfluramine in blocking
seizure-induced sudden death were evaluated in the DBA/1 mouse
model of SUDEP. In these studies, fenfluramine, known to enhance
the release of serotonin (5-hydroxytryptamine, 5-HT) in the brain,
was discovered to be effective in blocking audiogenic seizures
(AGSz) and seizure-induced respiratory arrest (S-IRA) in DBA/1
mice.
[0252] The present disclosure is directed to the surprising
discovery that certain serotonin receptors (also known as
5-hydroxytryptamine (5-HT) receptors) mediate the action of
fenfluramine (FFA) in blocking seizure-induced sudden death and
seizure-induced respiratory arrest (S-IRA) in mice. Specifically,
the present disclosure is directed to the surprising discovery that
fenfluramine is useful in treating, reducing and/or ameliorating
the risk or occurrence of respiratory depression and/or
seizure-induced respiratory arrest (S-IRA) associated with use of
one or more opioids, barbiturates and/or benzodiazepines in a human
patient.
[0253] Without being bound by theory, fenfluramine (FFA) enhances
serotonergic neurotransmission by augmenting carrier-mediated
synaptic release of serotonin (5-HT) in the brain due to disruption
of its vesicular storage and inhibiting its reuptake. Its active
metabolite, norfenfluramine (N-FFA), contributes to prolonging this
effect. Recent clinical studies found treatment with FFA to be
effective as an add-on (adjunctive) agent to improve seizure
control in patients with the intractable seizures characteristic of
Dravet syndrome, which is difficult to treat and has a tragically
high risk of SUDEP. Seizure activity was significantly reduced in
frequency and/or severity, and in some cases eliminated entirely,
by administering the drug fenfluramine.
[0254] The present disclosure is the first study to investigate the
efficacy of FFA on respiratory depression due to opioids,
barbiturates and/or benzodiazepines in a mammalian mouse model.
Thus, the present disclosure is directed to elucidating the effects
of FFA on respiratory depression. The effect of FFA on
seizure-induced respiratory arrest (S-IRA) in DBA/1 mice was
investigated.
[0255] As described herein, several 5-HT receptor-specific
antagonists were used to investigate fenfluramine's effects, to
determine whether the 5-HT antagonists could reverse the
anticonvulsant activity (and/or S-IRA blocking, or any other
effect) mediated by fenfluramine, thereby allowing identification
of a subset of 5-HT receptors to which fenfluramine binds and acts
as an agonist.
[0256] For these experiments, after subjecting DBA/1 mice to the
established priming procedure to assure consistent susceptibility
to S-IRA following AGSz, the mice were used to assess the effects
of fenfluramine on various 5-HT receptor subtypes. Seizures were
induced using an electrical bell, and resuscitation was
accomplished using a rodent respirator (Faingold et al., 2010). At
least 24 hours after priming, the mice received FFA (15 mg/kg,
i.p.) and were tested for AGSz and S-IRA susceptibility 16 hours
later. Thirty minutes prior to AGSz induction, a selective 5-HT
receptor antagonist or vehicle was administered to evaluate if a
specific receptor contributes to the ability of FFA to block S-IRA.
Seizure behaviors were recorded on videotape, quantified, and
compared statistically with vehicle-treated negative and
FFA-treated positive controls (Chi-Square Test; significance set at
p<0.05).
[0257] Specifically, the antagonists tested were: the 5-HT.sub.1A
antagonist WAY100635 (0.1-15 mg/kg); the 5-HT.sub.2 antagonist
Ritanserin (10-20 mg/kg); the 5-HT.sub.3 antagonist Ondansetron
(1-3 mg/kg); the 5-HT.sub.4 antagonist GR125487 (20-60 mg/kg); the
5-HT.sub.5A antagonist SB669551 (10-20 mg/kg); and the 5-HT.sub.7
antagonist SB269970 (30-40 mg/kg). Studies investigating the effect
of 5-HT.sub.6 and 5-HT.sub.1a/1b antagonists are also underway.
[0258] Notably, a reversal of the FFA-induced reduction in the
incidence (frequency) of S-IRA was observed following treatment
with the 5-HT.sub.4 antagonist (GR125487, 30 mg/kg). This dose was
effective in inducing a significant (p<0.05) blockade of this of
the FFA-induced reduction in S-IRA. While the antagonists of
5-HT.sub.2, 5-HT.sub.4 and 5-HT.sub.7 receptors were found to
reverse the anticonvulsant effect of FFA against the severity of
AGSz in the mice, but not FFA's S-IRA blocking effect, 5-HT.sub.1a
and 5-HT.sub.3 receptor antagonists were not effective at any dose
tested.
[0259] Specifically, a significant (p<0.05) partial reversal of
the FFA-induced S-IRA blockade was observed following 30-minutes
treatment with the 5-HT.sub.4 antagonist (GR125487, 30 mg/kg).
Thus, GR125487 was effective in inducing a significant blockade of
fenfluramine's inhibition of S-IRA. Interestingly, antagonists of
5-HT.sub.2, 5-HT.sub.4 and 5-HT.sub.7 receptors were found to
reverse the anticonvulsant effect of FFA against the severity of
AGSz but not its S-IRA blocking effect.
[0260] The antagonists of 5-HT.sub.2 (20 mg/kg Ritanserin),
5-HT.sub.4 (30 and 60 mg/kg GR125487) and 5-HT.sub.7 (30 mg/kg and
40 mg/kg SB269970) receptors were able to reverse FFA's
anticonvulsant effect against the severity of AGSz. The 5-HT.sub.5
a antagonist SB669551 blocked FFA's anticonvulsant effect at 20
mg/kg. In contrast, 5-HT.sub.1A (WAY100635 at 0.1-15 mg/kg) and
5-HT.sub.3 (Ondansetron at 1-3 mg/kg) receptor antagonists were not
effective at any dose tested.
[0261] These findings suggest that the anticonvulsant effect of FFA
against S-IRA induced by AGSz in DBA/1 mice is mediated, relatively
selectively, as a result of activation of 5-HT.sub.4 receptors. It
may be relevant that the expression levels of 5-HT.sub.4 receptors
in the DBA/1 mouse brain is not significantly different from that
in normal mice (Faingold et al., 2011). The results were surprising
in light of previous studies on the receptors that mediate the
ability of a selective serotonin re-uptake inhibitor to reduce
seizure severity and block S-IRA can be reversed only by a
selective 5-HT.sub.3 antagonist (Faingold et al., 2016). Thus,
agonists which activate specific 5-HT receptors (e.g., 5-HT.sub.4
receptor agonists) are of interest for future studies in animal
models of SUDEP and as a potential preventative treatment for human
SUDEP.
[0262] Generally, antagonists of the 5-HR.sub.1A, 5-HT.sub.3, and
receptors did not reverse fenfluramine's effect, suggesting that
fenfluramine's effect on S-IRA and/or AGSz is not mediated by an
interaction with these receptors. In contrast, the 5-HT.sub.2,
5-HT.sub.5A, 5-HT.sub.7 antagonists (Ritanserin at 20 mg/kg;
SB669551 at 20 mg/kg; and SB269970 at 30 mg/kg and 40 mg/kg) were
found to block FFA's anticonvulsant effect, suggesting that
fenfluramine's anticonvulsant effect may be mediated by its
interaction of these receptors.
[0263] Notably, because the compound GR125487 was found to
partially reverse fenfluramine's anticonvulsant effects and S-IRA
blocking effects, it was concluded that fenfluramine was found to
act specifically as an agonist at the 5-HT.sub.4 receptor.
[0264] Thus, the anticonvulsant effect of FFA against S-IRA induced
by AGSz in DBA/1 mice is mediated, at least in part, by activation
of 5-HT.sub.4 receptors. The expression level of 5-HT.sub.4
receptors in the DBA/1 mouse brain is not significantly different
from that in normal mice (Faingold et al., 2011). These results
were surprising in light of previous studies on the receptors that
mediate the ability of a selective serotonin re-uptake inhibitor to
reduce seizure severity and block S-IRA can be reversed only by a
selective 5-HT.sub.3 antagonist (Faingold et al., 2016).
[0265] Agonists which activate specific 5-HT receptors are of
interest for future studies in animal models of SUDEP and as a
potential preventative treatment for human SUDEP.
[0266] Known 5-HT receptors include: 5-HT.sub.1, 5-HT.sub.1A,
5-HT.sub.1B, 5-HT.sub.1C, 5-HT.sub.1D, 5-HT.sub.1E, 5-HT.sub.1F,
5-HT.sub.2, 5-HT.sub.2A, 5-HT.sub.2B, 5-HT.sub.2C, 5-HT.sub.3,
5-HT.sub.4, 5-HT.sub.5, 5-HT.sub.5A, 5-HT.sub.5B 5-HT.sub.6, and
5-HT.sub.7 amongst others. In some embodiments of the present
disclosure, the 5-HT receptor is 5-HT.sub.4. In some embodiments of
the present disclosure, the 5-HT receptor agonist is a 5-HT.sub.4
receptor agonist. In some embodiments of the present disclosure,
the 5-HT.sub.4 receptor agonist is fenfluramine. In certain
embodiments of this disclosure, the patient has been diagnosed with
epilepsy. In certain embodiments of this disclosure, the patient
has respiratory depression due to the use of an opioid, barbiturate
and/or benzodiazepine.
[0267] FFA has a specific effect at a particular 5-HT receptor
subtype, and 5-HT receptor-specific antagonists could reverse the
anticonvulsant effects and S-IRA blocking effects of FFA.
Fenfluramine (FFA), was found to enhance the release of serotonin
(5-hydroxytryptamine, 5-HT) in the brain, was found to be effective
in blocking audiogenic seizures (AGSz) and seizure-induced
respiratory arrest in these DBA/1 mice.
[0268] In some embodiments of this disclosure, the 5-HT receptor is
5-HT.sub.4. As disclosed herein, fenfluramine was found to act as
an anticonvulsant at 5-HT.sub.4 receptors to prevent
seizure-induced respiratory arrest (S-IRA) and seizure-induced
Sudden Unexpected Death in Epilepsy (SUDEP) in the DBA/1 mouse
model. Furthermore, the present study identifies fenfluramine as a
5-HT.sub.4 receptor agonist able to reverse respiratory depression
in a subject using one or more opioids, barbiturates, and/or
benzodiazepines.
[0269] Fluoxetine, a 5-HT re-uptake inhibitor (SSRI), can prevent
S-IRA in DBA/1 mice by acting via 5-HT.sub.3 receptors (Faingold,
et al., 2011, Epilepsy Behav. 22:186-190; Faingold, et al., 2016,
Epilepsy Behav. 64(Pt A):166-170). Fenfluramine (FFA), which
enhances 5-HT release in the brain, is an effective add-on in
Dravet syndrome patients (Ceulemans, et al., 2016, Epilepsia
57:e129-34; Schoonjans, et al., 2017, Eur J Neurol. 24(2):309-314)
and is able to block AGSz and S-IRA in DBA/1 mice. The 5-HT.sub.1_7
receptors, known to be expressed in brainstem cardio-respiratory
networks, are implicated in modulating respiration (Hilaire et al.,
2010, Respir. Physiol. Neurobiol. 174(1-2):76-88). Therefore, in
order determine the mechanism of action of FFA, the role of the
5-HT receptors in mediating anticonvulsant and S-IRA prophylaxis
effect of FFA in DBA/1 mice was investigated.
Specific Aspects of the Invention
[0270] Provided are therapeutic agents that are useful in
preventing, treating, or ameliorating symptoms associated with a
disease or disorder in a patient diagnosed with the disease or
disorder, including but not limited to patients diagnosed with
respiratory depression or seizure-induced respiratory arrest
(S-IRA) which can lead to Sudden Unexpected Death in Epilepsy
(SUDEP), and pharmaceutical compositions and formulations
comprising those agents that are useful in practicing the methods
of the invention.
Therapeutic Agents
[0271] The inventors have made the surprising discovery that
certain therapeutic agents (e.g. fenfluramine (FFA)) are useful in
treating diseases or disorders, including but not limited to
respiratory depression or seizure-induced respiratory arrest
(S-IRA). Thus, in accordance with one aspect of the present
disclosure, provided herein are therapeutic agents useful in
treating patients diagnosed with a disease or disorder and/or in
preventing or ameliorating symptoms of those diseases or disorders
exhibited by the patient.
[0272] Dosage/Frequency of Administration: Dosage forms can be
formulated for once a day administration, or for multiple daily
administrations (e.g. 2, 3 or 4 times a day administration).
Alternatively, for convenience, dosage forms can be formulated for
less frequent administration (e.g., monthly, bi-weekly, weekly,
every fourth day, every third day, or every second day), and
formulations which facilitate extended release are known in the
art.
[0273] As used herein, the phrase "semi-chronic administration"
refers to administration of a therapeutic agent, such as
fenfluramine or a 5-HT.sub.4 receptor agonist, for a period of
several days, a week, several weeks, a month, several months, a
year, or several years.
Binding of Single or Multiple Targets
[0274] In some embodiments, the therapeutic agents provided by the
disclosure can bind one or more targets, for example, two or more
targets, three or more targets, four or more targets, five or more
targets, or more.
Receptor Protein Targets
[0275] In some embodiments, the therapeutic agent binds a
5-HT.sub.4 receptor.
[0276] In some embodiments, the therapeutic agent binds to the
sigma-1 receptor and one or more 5-HT receptors, for example, the
5-HT.sub.1A receptor, the 5-HT.sub.1D receptor, the 5-HT.sub.1E
receptor, the 5-HT.sub.2A receptor, the 5-HT.sub.2C receptor, the
5-HT.sub.4 receptor, the 5-HT.sub.5A receptor, and/or the
5-HT.sub.7 receptor. In some embodiments, the therapeutic agent
binds to the sigma-1 receptor and the 5-HT.sub.4 receptor.
Functional Activity
[0277] In accordance with the present disclosure, the terms
"active" or "activity" are used herein to mean having an effect on
cell, nuclear, or tissue function, and is intended to encompass
agonist activity, inverse agonist activity, antagonist activity,
synergy, allosteric agonism, allosteric modulation, including
positive, negative and neutral allosteric modulation,
ago-allosteric modulation, including positive, negative, and
neutral ago-allosteric modulation, and ligand trapping.
Receptor Activity
[0278] In some embodiments, the therapeutic agent is active at one
or more 5-HT receptor proteins selected from the group consisting
of the 5-HT.sub.1A receptor, the 5-HT.sub.1D receptor, the
5-HT.sub.1E receptor, the 5-HT.sub.2A receptor, the 5-HT.sub.2C
receptor, the 5-HT.sub.4 receptor, the 5-HT.sub.5A receptor, and/or
the 5-HT.sub.7 receptor. In some embodiments, the therapeutic agent
activates the 5-HT.sub.4 receptor.
Therapeutic Agents Active at Multiple Targets
[0279] The disclosure further provides therapeutic agents that are
active one or more targets, for example, two or more targets, three
or more targets, four or more targets, five or more targets, or
more.
[0280] For example, in one embodiment, the disclosure provides
therapeutic agents that are active at two or more 5-HT receptors.
In this regard, the present disclosure is directed to the
surprising discovery that fenfluramine acts on the 5-HT.sub.4
receptors and is useful in preventing, treating or ameliorating
symptoms such as seizure-induced respiratory arrest (S-IRA) leading
to Sudden Unexpected Death in Epilepsy (SUDEP) in patients having a
seizure disease or disorder, epilepsy and/or epileptic
encephalopathy.
Therapeutic Agents which are Inactive at the 5-HT.sub.2B
Receptor
[0281] In preferred embodiments, the therapeutic agents disclosed
herein are not active at the 5-HT.sub.2B receptor to an extent
sufficient to cause adverse effects such as valvulopathy, pulmonary
hypertension or other adverse effects. In alternate exemplary
embodiments, the agents do not bind the 5-HT.sub.2B receptor, or
are 5-HT.sub.2B antagonists (i.e., agents that block the activity
of agonists), or are 5-HT.sub.2B inverse antagonists (i.e., agents
that decrease basal activity of the receptor), or are neutral
agonists (i.e., compounds that block binding of agonists) of the
5-HT.sub.2B receptor.
Diseases and Disorders
[0282] The therapeutic agents provided by the disclosure are useful
in treating a number of diseases and disorders, and/or in reducing
or ameliorating their symptoms. For example, the therapeutic agents
disclosed herein are useful for treating respiratory depression or
seizure-induced respiratory arrest (S-IRA), and in preventing,
reducing or ameliorating their symptoms in patients diagnosed with
those conditions.
Methods of Use
[0283] The above-described therapeutic agents can be employed in a
variety of methods. As summarized above, aspects of the method
include administering a therapeutically effective amount of a
therapeutic agent as described herein to treat a patient in need of
treatment, for example, to a patient diagnosed with a disease or
condition of interest, or to prevent, reduce or ameliorate symptoms
of a disease or disorder in patients diagnosed with that disease or
disorder. Examples include seizures, particularly status
epilepticus, seizure-induced respiratory arrest (S-IRA), and Sudden
Unexpected Death in Epilepsy (SUDEP). By "therapeutically effective
amount" is meant the concentration of a compound that is sufficient
to elicit the desired biological effect (e.g., treatment or
prevention of epilepsy and associated symptoms and co-morbidities,
including but not limited to seizure-induced sudden respiratory
arrest (S-IRA). Diseases and conditions of interest include, but
are not limited to, respiratory depression or seizure-induced
respiratory arrest (S-IRA). Also of interest is the prevention or
amelioration of symptoms and co-morbidities associated with those
diseases
[0284] In some embodiments, the subject method will be protective
of symptoms, including but not limited to respiratory depression,
S-IRA, SUDEP, and co-morbid conditions.
Genetic Testing
[0285] In some cases, it can be desirable to test the patients for
a genetic mutation prior to administration of some of the
therapeutic agents provided by the disclosure, especially in cases
where use of specific agent is contraindicated either because the
agent is ineffective or because it would have undesired or serious
side effects. Thus, it is in some cases desirable to test patients
prior to treatment. For example, a subject/patient can be tested
for the presence of opioids, barbiturates, and/or benzodiazepines,
and/or for respiratory depression or seizure-induced respiratory
arrest (S-IRA) associated with the use of these drugs.
[0286] Other genetic tests can be carried out, and can be required
as a condition of treatment.
Dosing
[0287] The different therapeutic agents disclosed herein can be
dosed to patients in different amounts depending on different
patient age, size, sex, condition as well as the use of different
therapeutic agents.
[0288] For example, the dosing can be a daily dosing based on
weight. However, for convenience the dosing amounts can be preset.
In general, the smallest dose which is effective should be used for
the particular patient. The patient can be dosed on a daily basis
using a single dosage unit which single dosage unit can be
comprised of the therapeutic agent in an amount appropriate for the
particular agent. The dosage unit can be selected based on the
delivery route, e.g. the dosage unit can be specific for oral
delivery, transdermal delivery, rectal delivery, vaginal delivery,
buccal delivery, intranasal and/or inhaled delivery, pulmonary
delivery or delivery by injection.
Formulation
[0289] The dose of therapeutic agent administered in the methods of
the present invention can be formulated in any pharmaceutically
acceptable dosage form including, but not limited to oral dosage
forms such as tablets including orally disintegrating tablets,
capsules, lozenges, oral solutions or syrups, oral emulsions, oral
gels, oral films, buccal liquids, powder e.g. for suspension, and
the like; injectable dosage forms; transdermal dosage forms such as
transdermal patches, ointments, creams; inhaled dosage forms;
and/or nasally, rectally, vaginally administered dosage forms. Such
dosage forms can be formulated for once a day administration, or
for multiple daily administrations (e.g. 2, 3 or 4 times a day
administration).
[0290] Particular formulations of the invention are in a liquid
form. The liquid can be a solution or suspension and can be an oral
solution or syrup which is included in a bottle with a pipette
which is graduated in terms of milligram amounts which will be
obtained in a given volume of solution. The liquid solution makes
it possible to adjust the solution for small children which can be
administered in increments appropriate to the particular
therapeutic agent.
[0291] Administration of the subject compounds can be systemic or
local. In certain embodiments, administration to a mammal will
result in systemic release of a subject compound (for example, into
the bloodstream). Methods of administration can include enteral
routes, such as oral, buccal, sublingual, and rectal; topical
administration, such as transdermal and intradermal; and parenteral
administration. Suitable parenteral routes include injection via a
hypodermic needle or catheter, for example, intravenous,
intramuscular, subcutaneous, intradermal, intraperitoneal,
intraarterial, intraventricular, intrathecal, and intracameral
injection and non-injection routes, such as intravaginal rectal, or
nasal administration. In certain embodiments, the subject compounds
and compositions are administered orally. In certain embodiments,
it can be desirable to administer a compound locally to the area in
need of treatment. In some embodiments, the method of
administration of the subject compound is parenteral
administration. This can be achieved, for example, by local
infusion during surgery, topical application, e.g., in conjunction
with a wound dressing after surgery, by injection, by means of a
catheter, by means of a suppository, or by means of an implant,
said implant being of a porous, non-porous, or gelatinous material,
including membranes, such as sialastic membranes,
[0292] Combination therapy includes administration of a single
pharmaceutical dosage formulation which contains the subject
compound and one or more additional agents; as well as
administration of the subject compound and one or more additional
agent(s) in its own separate pharmaceutical dosage formulation. For
example, a subject 5-HT.sub.4 receptor agonist (e.g., fenfluramine)
and an additional agent-for treating respiratory depression can be
administered to the patient together in a single dosage composition
such as a combined formulation, or each agent can be administered
in a separate dosage formulation. Where separate dosage
formulations are used, the subject compound and one or more
additional agents can be administered concurrently, or at
separately staggered times, e.g., sequentially.
[0293] In some embodiments, the subject method is an in vitro
method that includes contacting a sample with a subject compound.
The protocols that can be employed in these methods are numerous,
and include but are not limited to, serotonin release assays from
neuronal cells, cell-free assays, binding assays (e.g., 5-HT.sub.4
receptor binding assays); cellular assays in which a cellular
phenotype is measured, e.g., gene expression assays; and assays
that involve a particular animal model for a condition of interest
(e.g., respiratory depression or seizure-induced respiratory arrest
(S-IRA)) or symptoms or comorbidities associated with such
conditions.
Pharmaceutical Preparations
[0294] Also provided are pharmaceutical preparations.
Pharmaceutical preparations are compositions that include a
compound (either alone or in the presence of one or more additional
active agents) present in a pharmaceutically acceptable vehicle.
The term "pharmaceutically acceptable" means approved by a
regulatory agency of the Federal or a state government or listed in
the U.S. Pharmacopeia or other generally recognized pharmacopeia
for use in mammals, such as humans. The term "vehicle" refers to a
diluent, adjuvant, excipient, or carrier with which a compound of
the invention is formulated for administration to a mammal.
[0295] The choice of excipient will be determined in part by the
particular compound, as well as by the particular method used to
administer the composition. Accordingly, there is a wide variety of
suitable formulations of the pharmaceutical composition of the
present invention.
[0296] The dosage form of a therapeutic agent employed in the
methods of the present invention can be prepared by combining the
therapeutic agent with one or more pharmaceutically acceptable
diluents, carriers, adjuvants, and the like in a manner known to
those skilled in the art of pharmaceutical formulation.
[0297] By way of illustration, the therapeutic agent can be admixed
with conventional pharmaceutically acceptable carriers and
excipients (i.e., vehicles) and used in the form of aqueous
solutions, tablets, capsules, elixirs, suspensions, syrups, wafers,
and the like. Such pharmaceutical compositions contain, in certain
embodiments, from about 0.1% to about 90% by weight of the active
compound, and more generally from about 1% to about 30% by weight
of the active compound. The pharmaceutical compositions can contain
common carriers and excipients, such as solubilizers, isotonic
agents, suspending agents, emulsifying agents, stabilizers,
preservatives, colorants, diluents, buffering agents, surfactants,
moistening agents, flavoring agents and disintegrators, and
including, but not limited to, corn starch, gelatin, lactose,
dextrose, sucrose, microcrystalline cellulose, kaolin, mannitol,
dicalcium phosphate, sodium chloride, alginic acid, vegetable or
other similar oils, synthetic aliphatic acid glycerides, esters of
higher aliphatic acids or propylene glycol, corn starch, potato
starch, acacia, tragacanth, gelatin, glycerin, sorbitol, ethanol,
polyethylene glycol, colloidal silicon dioxide, croscarmellose
sodium, talc, magnesium stearate and stearic acid. Disintegrators
commonly used in the formulations of this invention include
croscarmellose, microcrystalline cellulose, corn starch, sodium
starch glycolate and alginic acid. The compounds can be formulated
into preparations for injection by dissolving, suspending or
emulsifying them in an aqueous or nonaqueous solvent, such as
vegetable or other similar oils, synthetic aliphatic acid
glycerides, esters of higher aliphatic acids or propylene glycol;
and if desired, with conventional additives such as solubilizers,
isotonic agents, suspending agents, emulsifying agents, stabilizers
and preservatives.
[0298] In some embodiments, formulations suitable for oral
administration can include (a) liquid solutions, such as an
effective amount of the compound dissolved in diluents, such as
water, or saline; (b) capsules, sachets or tablets, each containing
a predetermined amount of the active ingredient, as solids or
granules; (c) suspensions in an appropriate liquid; and (d)
suitable emulsions. Tablet forms can include one or more of
lactose, mannitol, corn starch, potato starch, microcrystalline
cellulose, acacia, gelatin, colloidal silicon dioxide,
croscarmellose sodium, talc, magnesium stearate, stearic acid, and
other excipients, colorants, diluents, buffering agents, moistening
agents, preservatives, flavoring agents, and pharmacologically
compatible excipients. Lozenge forms can include the active
ingredient in a flavor, usually sucrose and acacia or tragacanth,
as well as pastilles including the active ingredient in an inert
base, such as gelatin and glycerin, or sucrose and acacia,
emulsions, gels, and the like containing, in addition to the active
ingredient, such excipients as are described herein.
[0299] In some cases, the compound is formulated for oral
administration. In some cases, for an oral pharmaceutical
formulation, suitable excipients include pharmaceutical grades of
carriers such as mannitol, lactose, glucose, sucrose, starch,
cellulose, gelatin, magnesium stearate, sodium saccharine, and/or
magnesium carbonate. For use in oral liquid formulations, the
composition can be prepared as a solution, suspension, emulsion, or
syrup, being supplied either in solid or liquid form suitable for
hydration in an aqueous carrier, such as, for example, aqueous
saline, aqueous dextrose, glycerol, or ethanol, preferably water or
normal saline. If desired, the composition can also contain minor
amounts of non-toxic auxiliary substances such as wetting agents,
emulsifying agents, or buffers.
[0300] Particular formulations of the invention are in a liquid
form. The liquid can be a solution or suspension and can be an oral
solution or syrup which is included in a bottle with a pipette
which is graduated in terms of milligram amounts which will be
obtained in a given volume of solution. The liquid solution makes
it possible to adjust the solution for small children which can be
administered anywhere from 0.5 mL to 15 mL and any amount between
in half milligram increments and thus administered in 0.5, 1.0,
1.5, 2.0 mL, etc.
[0301] A liquid composition will generally consist of a suspension
or solution of the compound or pharmaceutically acceptable salt in
a suitable liquid carrier(s), for example, ethanol, glycerine,
sorbitol, non-aqueous solvent such as polyethylene glycol, oils or
water, with a suspending agent, preservative, surfactant, wetting
agent, flavoring or coloring agent. Alternatively, a liquid
formulation can be prepared from a powder for reconstitution.
EXAMPLES
[0302] The following examples are put forth so as to provide those
of ordinary skill in the art with a complete disclosure and
description of how to make and use the present invention, and are
not intended to limit the scope of what the inventors regard as
their invention nor are they intended to represent that the
experiments below are all or the only experiments performed.
Efforts have been made to ensure accuracy with respect to numbers
used (e.g. amounts, temperature, etc.) but some experimental errors
and deviations should be accounted for. Unless indicated otherwise,
parts are parts by weight, molecular weight is weight average
molecular weight, temperature is in degrees Centigrade, and
pressure is at or near atmospheric.
[0303] Several selective serotonin (5-HT) reuptake inhibitors were
found to prevent seizure-induced respiratory arrest (S-IRA) in DBA
mice. However, not all drugs that enhance the activation of 5-HT
receptors effectively block S-IRA in DBA mice. Therefore,
fenfluramine (FFA) was investigated to determine whether its
augmentation of 5-HT release altered susceptibility to audiogenic
seizures and S-IRA in DBA/1 mice.
Example 1
Effects of Fenfluramine on Animal Model of SUDEP
Materials and Methods
Animals
[0304] These studies involved age matched (<80 days) male DBA/1
mice obtained from ENVIGO. Because there were no significant sex
differences in the AGSz incidence (frequency), severity and S-IRA
susceptibility in DBA/1 mice, males were used in this study. The
mice were primed as described in previous studies (Faingold et al.,
(2010). Epilepsy Behav. 17:436-40; Faingold, et al. (2011) Brain
Res. 1418:104-10; Faingold, et al., (2011) Epilepsy Behav.
22:186-90). Briefly, the mice were maintained on an ad libitum diet
under a 12 h light-dark cycle in a temperature and
humidity-controlled laboratory animal medicine facility. Starting
at postnatal day 23-25, the mice were primed and tested for
consistent susceptibility to AGSz and S-IRA by presenting an
intense acoustic stimulus, as described previously. The mice
exhibiting consistent susceptibility to S-IRA on three consecutive
tests were included in the following studies.
Seizure Induction and Resuscitation
[0305] AGSz were induced by presenting to each DBA/1 mouse (N=287)
an intense (110 dB SPL; re: 0.0002 dynes/cm.sup.2) broad-band
acoustic stimulus from an electrical bell (Heath Zenith Model
#172C-A) installed inside a plastic cylinder (43 cm diameter).
using an electrical bell, and resuscitation was accomplished using
a rodent respirator (Faingold et al., (2010) DBA/1 mice exhibit
chronic susceptibility to audiogenic seizures followed by sudden
death associated with respiratory arrest. Epilepsy Behav.
17:436-40).
[0306] The stimulus was presented until the mouse exhibited tonic
seizures or for a maximum duration of 60 s. The typical seizure
semiology in the DBA/1 mice begins with a wild running phase,
followed by clonic-tonic seizures and then tonic hind-limb
extension that immediately leads to S-IRA during post-ictal
behavioral depression (PID). The onset of S-IRA was visually
determined by the occurrence of respiratory failure following loss
of the righting reflex, relaxation of the pinnae, and then a
generalized loss of muscle tone. These behaviors are reliable
indicators of imminent sudden death in DBA mice. Resuscitation was
initiated within 10 s after pinna relaxation and the generalized
loss of muscle tone, which was effective in reversing S-IRA and
reviving >90% of the mice. The mice were placed in a supine
position, and a polyethylene tube (4.4 mm external diameter)
connected to the outflow of a rodent respirator (Harvard Apparatus
680), pumping one cc of room air at 200 strokes/min, was the placed
over the nostrils, which produced observable displacement of the
chest. Respiratory support was provided until spontaneous breathing
rhythm returned, which required .about.19 sec. The mice were
monitored until they regained the righting reflex and then returned
to their home cage. Video recordings of seizure behaviors and
recovery were made for off-line evaluation and analysis, including
the duration of PID, as indicated by time from muscle tone loss to
return of the righting reflex.
Behavioral Testing
[0307] The experiments herein disclosed examined the dose-response
relationship of FFA (10-40 mg/kg, i.p.) on AGSz-induced behaviors
in DBA/1 mice compared to vehicle (saline) treated control mice
using different seizure-testing protocols. This initial protocol
involved induction of AGSz at 30 min, 12 h and 24 h after drug
administration, and subsequently at 24 h intervals until
susceptibility to S-IRA returned. These studies were aimed at
determining whether FFA can reduce the incidence (frequency) and
severity of AGSz and susceptibility to S-IRA. Based on these
results, the 5-20 mg/kg dose range was selected to determine the
time-course of FFA's effect in another group of DBA/1 mice by a
second seizure testing protocol using 8 h intervals during the
first 24 h to evaluate the time course of effect in greater detail,
and subsequently at 24 h periods. To determine the effect of FFA on
the severity of AGSz in DBA/1 mice, the ordinal scoring system of
De Sarro and coworkers was used: no seizure=0; wild running=1;
clonic seizure=2; tonic seizure=3; death/S-IRA=4. The median
effective dose (ED.sub.50) for FFA for blocking AGSz at 30 min
following the i.p. injection in DBA/1 mice was calculated using a
second order polynomial equation (y=65.113x.sup.2-2.0715x-63.578)
that gave the best fit (R.sup.2=0.9989).
Drugs
[0308] Fenfluramine (FFA), kindly provided by Zogenix
International, was dissolved in sterile saline vehicle prepared in
the laboratory using Sodium Chloride tablets (Catalog number:
07982-100TAB-F) obtained from Sigma-Aldrich (St. Louis, Mo.,
U.S.A.).
Statistical Analysis
[0309] The videos of seizure behaviors were analyzed visually, and
the incidence (frequency) of AGSz, seizure severity, and incidence
(frequency) of S-IRA following drug treatment were compared
statistically to vehicle controls using the Chi-square,
Mann-Whitney U or paired samples t-test with SPSS software. The
ED.sub.50 was calculated using SigmaPlot 13 and Microsoft.RTM.
Excel. The experimental protocols used in these studies were
approved by the Laboratory Animal Care and Use Committee of
Southern Illinois University School of Medicine, which are in
accordance with National Institutes of Health guidelines for the
care and use of laboratory animals. Measures to minimize animal
usage as well as pain and discomfort were included in these
procedures.
[0310] DBA/1 male mice (25-26 days) were subjected to AGSz priming
involving 3-4 daily seizures by presenting 122 dB SPL (re: 0.0002
dyne/cm.sup.2) broadband acoustic stimulus for <1 min.
[0311] Mice that showed S-IRA were resuscitated by placing the
inhalation tube of a rodent respirator (200 strokes/min) over the
nose.
[0312] At least 24 h after the final priming seizure the consistent
S-IRA susceptible mice were given intraperitoneal (i.p.) injection
of FFA or vehicle (saline).
[0313] The experimental paradigms used to determine the 5-HT
receptors that mediate the protective effect of FFA involved:
[0314] Determination of dose and time at which FFA-treated mice
showed the lowest incidence of S-IRA following tonic seizures: Mice
were tested at 8 h intervals after receiving FFA (5-20 mg/kg, i.p.)
for 24 h (to determine the selective S-IRA blocking effect). The
mice that didn't show a return of S-IRA susceptibility were tested
again at 24 h intervals.
[0315] Determination of 5-HT receptors that mediate S-IRA
prophylaxis and anticonvulsant effect of FFA: Selective 5-HT
receptor antagonist were administered (i.p.) 30 min prior to
seizure testing.
[0316] Behaviors were recorded on videotape and quantified, and
changes were analyzed offline using SPSS and Excel software.
[0317] The incidence of S-IRA and tonic seizures were analyzed
Chi-square test with a significance level set at p<0.05.
Dose- and Time-Dependent Effects of FFA on Audiogenic Seizures
(AGSz) and S-IRA in DBA/1 Mice.
[0318] FFA significantly reduced the incidence of tonic seizures,
the AGSz phenotype known to lead to S-IRA, in DBA/1 mice. 10-20
mg/kg of FFA had a blocking effect on S-IRA (FIGS. 1A-1D). The
incidence of S-IRA following AGSz in DBA/1 mice was significantly
reduced and was long-lasting. Although the tonic AGSz and S-IRA
susceptibility returned by approximately 48 h in the mice that
received 20 mg/kg FFA, many of these mice continued to show a
reduced susceptibility to these seizure behaviors for several days.
In contrast, the mice that received 10 mg/kg of FFA showed a
shorter-duration of the reduction of S-IRA and tonic seizure at 12
h.
[0319] FFA prevented S-IRA in DBA/1 mice. The mice that received
10-20 mg/kg of FFA showed a significant reduction in the incidence
of S-IRA starting at 8 h (FIG. 1A). Starting at 8 h following 10,
15 and 20 mg/kg FFA, a significant reduction in the incidence of
S-IRA occurred when compared to saline treated controls. The
incidence of S-IRA in the mice that received 5 mg/kg FFA was not
affected. A return of S-IRA susceptibility among the FFA treated
DBA/1 mice occurred at 48 h. [*p<0.05; **p<0.01; #p<0.001
indicate statistically different from controls, respectively, as
determined by Chi-square test].
[0320] FIG. 1B shows selective S-IRA blocking effect of FFA. A
significant reduction in the incidence of S-IRA was seen at the 8 h
time point in 100% of the mice following 10-20 mg/kg FFA, and
continued to exhibit tonic seizures displayed a significant
[#p<0.001, Chi-square test] incidence of selective blockade of
S-IRA (FIG. 1B). A return of susceptibility to S-IRA in these
FFA-treated mice was seen by 48 h.
[0321] FIGS. 1C-1D show reduction in the incidence of S-IRA and a
significant increase in percent selective S-IRA blockade upon
treatment with 15 mg/kg FFA (n=73), as compared to saline-treated
counterparts (n=38).
[0322] To identify a subset of 5-HT receptors to which fenfluramine
specifically binds and acts as an agonist, several 5-HT
receptor-specific antagonists were evaluated for their ability to
reversing fenfluramine's effect on seizure and S-IRA incidence in
DBA/1 mice. Antagonists of 5-HT.sub.1a, 5-HT.sub.2, 5-HT.sub.3,
5-HT.sub.4, 5-HT.sub.5a and 5-HT.sub.7 receptors were tested and
the results are detailed below. Studies investigating the effect of
5-HT.sub.6 and 5-HT.sub.1a/1b antagonists are underway.
[0323] For these experiments, DBA/1 mice were used (after
subjecting to the established priming procedure to assure
consistent susceptibility to S-IRA following AGSz) to assess the
effects of fenfluramine on various 5-HT receptors. Seizures were
induced using an electrical bell, and resuscitation was
accomplished using a rodent respirator (Faingold et al., 2010). At
least 24 hours after priming, the mice received FFA (10 or 20
mg/kg, i.p.) and were tested for AGSz and S-IRA susceptibility 16
hours later. Thirty minutes prior to AGSz induction, a selective
5-HT receptor antagonist or vehicle was administered to evaluate if
a specific receptor contributes to the ability of FFA to block
S-IRA. Seizure behaviors were recorded on videotape, quantified,
and compared statistically with vehicle-treated negative and
FFA-treated positive controls (Chi-Square Test; significance set at
p<0.05).
Antagonists
[0324] Specifically, the antagonists tested were: the 5-HT.sub.2
antagonist Ritanserin (10-20 mg/kg); the 5-HT.sub.3 antagonist
Ondansetron (2-3 mg/kg); the 5-HT.sub.4 antagonist GR125487 (20-30
mg/kg); and the 5-HT.sub.7 antagonist SB269970 (30-40 mg/kg).
[0325] Results:
[0326] Notably, a partial reversal of the FFA-induced S-IRA
blockade was observed following treatment with the 5-HT.sub.4
antagonist (GR125487, 30 mg/kg). Thus, GR125487 was effective in
inducing a significant blockade of fenfluramine's inhibition of
S-IRA (See FIGS. 4A and 4B). The antagonists of 5-HT.sub.2 (10-20
mg/kg Ritanserin), 5-HT.sub.4 (20 and 30 mg/kg GR125487) and
5-HT.sub.7 (30 mg/kg and 40 mg/kg SB269970) receptors were able to
reverse FFA's anticonvulsant effect against the severity of AGSz.
Interestingly, antagonists of 5-HT.sub.2 and 5-HT.sub.7 receptors
were found to reverse only the anticonvulsant effect of FFA against
the severity of AGSz but not its S-IRA blocking effect, suggesting
that fenfluramine's anticonvulsant effect may be mediated by its
interaction of these receptors. (See FIGS. 2A-2B, and 5A-5B). In
contrast, the 5-HT.sub.3 (Ondansetron at 2-3 mg/kg) receptor
antagonist was not effective at any dose tested. Because the
compound GR125487 was found to partially reverse fenfluramine's
anticonvulsant effects and S-IRA blocking effects, it was concluded
that fenfluramine was found to act specifically as an agonist at
the 5-HT.sub.4 receptor.
[0327] Thus, the effect of FFA against S-IRA in DBA/1 mice is
mediated, at least in part, by activation of 5-HT.sub.4 receptors.
The expression level of 5-HT.sub.4 receptors in the DBA/1 mouse
brain is not significantly different from that in normal mice
(Faingold et al., 2011). These results were surprising in light of
previous studies on the receptors that mediate the ability of a
selective serotonin re-uptake inhibitor to reduce seizure severity
and block S-IRA can be reversed only by a selective 5-HT.sub.3
antagonist (Faingold et al., 2016).
Discussion
[0328] A model illustrating the presently disclosed discoveries is
shown in FIG. 6.
[0329] The present study found that FFA administration
significantly reduced seizure severity or blocked AGSz
susceptibility in DBA/1 mice in a dose- and time-dependent manner.
FFA was also found to significantly reduce the incidence of S-IRA,
and a selective block of S-IRA without affecting any seizure
behavior was also observed. These findings suggest that FFA has the
therapeutic potential for improving seizure control and preventing
S-IRA and SUDEP.
[0330] A significant reversal (p<0.05) of the FFA-mediated
reduction in S-IRA incidence was induced by the 5-HT.sub.4 receptor
antagonist (GR125487).
[0331] The effect of FFA to reduce seizure severity (incidence of
tonic seizures) was reversed by the 5-HT.sub.2 receptor antagonist
(ritanserin), 5-HT.sub.4 receptor antagonist and 5-HT.sub.7
receptor antagonist (SB269970).
[0332] 5-HT.sub.3 receptors, which are implicated in mediating
protective effect of fluoxetine in DBA/1 mice, are not involved in
mediating the effect of FFA.
[0333] These findings implicate 5-HT.sub.4 receptors in a crucial
role of mediating the S-IRA prophylactic effect of FFA, while the
5-HT.sub.2 and 5HT.sub.7 receptors also play a role in modulating
the action of FFA in reducing AGSz susceptibility in these
mice.
[0334] In conclusion, we show for first time that 5-HT.sub.4
receptors mediate the seizure-induced sudden death prevention
effect of FFA in DBA/1 mice.
[0335] Studies involving intracerebrovascular injection of
5-HT.sub.4 and other 5-HT receptor antagonist along with the i.p.
injection of FFA are needed to confirm its mechanism of action.
[0336] The present study identifies the 5-HT.sub.4 receptor agonist
fenfluramine is useful in mitigating opioid-, barbiturate- and/or
benzodiazepine-induced respiratory depression.
[0337] Future studies will investigate the protective effect of FFA
against opiate-induced respiratory depression, and also the
potential prophylactic role of 5-HT.sub.4 receptor agonists against
S-IRA in DBA/1 mice.
Example 3
Further Studies of FFA's Anticonvulsant and S-IRA Blocking
Effects
[0338] First, because the 5-HT.sub.4 receptor antagonist (GR125487)
was able to significantly reverse the anticonvulsant and S-IRA
blocking effects of FFA in the DBA/1 mouse model, further studies
will be conducted to investigate the anticonvulsant and S-IRA
blocking potential of additional 5-HT.sub.4 receptor agonists. For
example, 10-30 mg/kg BIMU8, alone and in combination with FFA, will
be assessed for its effects on AGSz and S-IRA (Manzke et al., 2003;
Hasebe et al., 2015).
[0339] Additionally, the effect of 5-HT.sub.4 receptor agonists
(e.g., fenfluramine) on reducing ameliorating and/or eliminating
seizures, and/or S-IRA and/or SUDEP in a clinical study in humans
has been assessed.
[0340] Additionally, intracerebrovasular microinjection of GR125487
(10, 20 and 40 nmol) will be performed to further investigate the
effects of fenfluramine or other 5-HT.sub.4 receptor agonists on
FFA-like targets in the brain (See De Deurwaerdere et al., 2002;
Consolo et al., 1994).
[0341] Furthermore, because the 5-HT.sub.4 receptor antagonist
significantly reduced the anticonvulsant and S-IRA suppressant
effects of FFA, the role of Sigma 1 receptors in mediating the
effect will be investigated. The efficacy of a Sigma 1 receptor
antagonist, NE-100, as compared to Sigma 2 antagonist (YUN252), in
reversing the effect of FFA on AGSz and the incidence of S-IRA in
DBA/1 mice will be studied.
[0342] Finally, if Sigma receptor antagonists are able to affect
the action of FFA in DBA/1 mice, a follow-up study for the effect
of Sigma 1 or 2 agonists and positive allosteric modulator, E1R
(10-75 mg/kg), on AGSz and S-IRA in DBA/1 mice will be conducted to
further validate this mechanism.
[0343] The preceding merely illustrates the principles of the
invention. It will be appreciated that those skilled in the art
will be able to devise various arrangements which, although not
explicitly described or shown herein, embody the principles of the
invention and are included within its spirit and scope.
Furthermore, all examples and conditional language recited herein
are principally intended to aid the reader in understanding the
principles of the invention and the concepts contributed by the
inventors to furthering the art, and are to be construed as being
without limitation to such specifically recited examples and
conditions. Moreover, all statements herein reciting principles,
aspects, and embodiments of the invention as well as specific
examples thereof, are intended to encompass both structural and
functional equivalents thereof. Additionally, it is intended that
such equivalents include both currently known equivalents and
equivalents developed in the future, i.e., any elements developed
that perform the same function, regardless of structure. The scope
of the present invention, therefore, is not intended to be limited
to the exemplary embodiments shown and described herein. Rather,
the scope and spirit of present invention is embodied by the
appended claims.
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