U.S. patent application number 10/312895 was filed with the patent office on 2004-02-19 for phospholipid derivatives of valproic acid and mixtures thereof.
Invention is credited to Kozak, Alexander.
Application Number | 20040033987 10/312895 |
Document ID | / |
Family ID | 24460534 |
Filed Date | 2004-02-19 |
United States Patent
Application |
20040033987 |
Kind Code |
A1 |
Kozak, Alexander |
February 19, 2004 |
Phospholipid derivatives of valproic acid and mixtures thereof
Abstract
The present invention relates to compounds, which are
phospholipid derivatives of valproic acid, to compositions
comprising said compounds and their use for treating epilepsy,
migraine, bipolar disorders and pain.
Inventors: |
Kozak, Alexander; (Rehovot,
IL) |
Correspondence
Address: |
DAVIDSON, DAVIDSON & KAPPEL, LLC
485 SEVENTH AVENUE, 14TH FLOOR
NEW YORK
NY
10018
US
|
Family ID: |
24460534 |
Appl. No.: |
10/312895 |
Filed: |
July 11, 2003 |
PCT Filed: |
July 10, 2001 |
PCT NO: |
PCT/IL01/00629 |
Current U.S.
Class: |
514/78 ; 514/114;
514/557 |
Current CPC
Class: |
A61P 25/00 20180101;
C07F 9/10 20130101; A61K 31/352 20130101; A61P 25/08 20180101; A61P
25/06 20180101; A61K 31/19 20130101; A61K 47/544 20170801 |
Class at
Publication: |
514/78 ; 514/557;
514/114 |
International
Class: |
A61K 031/685; A61K
031/66; A61K 031/19 |
Claims
What is claimed is:
1. A pharmaceutical composition comprising a therapeutically
effective amount of valproic acid or pharmaceutically acceptable
derivative thereof covalently bonded to a phospholipid moiety; and
a pharmaceutically acceptable-carrier.
2. The pharmaceutical composition according to claim 1, wherein
said phospholipid moiety is selected from the group consisting of
plasmalogens, phosphatidic acids and phospho-esters derivatives
thereof.
3. The pharmaceutical composition according to claim 1, wherein
said phospholipid moiety is selected from the group consisting of
lysophosphatidyl-ethanolamine, N-mono-(C.sub.1-4)-all,
N,N-di-(C.sub.1-4)-alkyl and quaternary derivatives of the amines
thereof.
4. The pharmaceutical composition according to claim 3, wherein
said quaternary derivative of lysophosphatidyl-ethanolamine is
lysophosphatidylcholine.
5. The pharmaceutical composition according to claim 1, wherein
said valproic acid or pharmaceutically acceptable derivative
thereof covalently bonded to said phospholipid moiety is
1-palmitoyl-2-valproyl-s- n-glycero-3-phosphatidyl-choline.
6. The pharmaceutical composition according to claim 1, wherein
said valproic acid or pharmaceutically acceptable derivative
thereof covalently bonded to said phospholipid moiety is
1-stearoyl-2-valproyl-sn- -glycero-3-phosphatidyl-choline.
7. The pharmaceutical composition according to claim 1 wherein said
valproic acid or pharmaceutically acceptable derivative thereof is
covalently linked to said phospholipid moiety at a position
selected from the group consisting of sn-1, Sn-2, and sn-3.
8. The pharmaceutical composition according to claim 1 wherein said
valproic acid or pharmaceutically acceptable derivative thereof is
covalently linked to said phospholipid moiety at a position
sn-2.
9. The pharmaceutical composition according to claim 8 wherein said
valproic acid or pharmaceutically acceptable derivative thereof is
released by cleavage by phospholipase A.sub.2 at said sn-2
position.
10. The pharmaceutical composition according to claim 1, wherein
said composition is in a form selected from the group consisting of
solutions, suspensions, emulsions, syrups, capsules, tablets and
suppositories.
11. The pharmaceutical composition of claim 1, which is suitable
for oral administration, intravenous administration, or rectal
administration.
12. The pharmaceutical composition of claim 1, further comprising a
second valproic acid or pharmaceutically acceptable derivative
thereof covalently bonded to a different phospholipid moiety,
wherein said valproic acid or pharmaceutically acceptable
derivative thereof covalently bonded to said phospholipid moiety
and said second valproic acid or pharmaceutically acceptable
derivative thereof covalently bonded to said different phospholipid
moiety are in a ratio of from about 1:20 to about 1:2 by
weight.
13. The pharmaceutical composition of claim 1, further comprising a
second valproic acid or said pharmaceutically acceptable derivative
thereof covalently bonded to a different phospholipid moiety;
wherein said valproic acid or pharmaceutically acceptable
derivative thereof covalently bonded to said phospholipid moiety
and said second valproic acid or pharmaceutically acceptable
derivative thereof covalently bonded to said different phospholipid
moiety are in a ratio of from about 1:5 to about 1:7 by weight.
14. The pharmaceutical composition of claim 1, further comprising a
second valproic acid or a pharmaceutically acceptable derivative
thereof covalently bonded to a different phospholipid moiety.
15. The pharmaceutical composition of claim 14, wherein said
valproic acid or pharmaceutically acceptable derivative thereof
covalently bonded to said phospholipid moiety is
1-palmitoyl-2-valproyl-sn-glycero-3-phosphati- dyl-choline.
16. The pharmaceutical composition of claim 14, wherein said second
valproic acid or pharmaceutically acceptable derivative thereof
covalently bonded to said different phospholipid moiety is
1-stearoyl-2-valproyl-sn-glycero-3-phosphatidyl-choline.
17. The pharmaceutical composition of claim 14, wherein the total
amount of said first valproic acid or said pharmaceutically
acceptable derivative thereof covalently bonded to said
phospholipid moiety and said second valproic acid or said
pharmaceutically acceptable derivative thereof covalently bonded to
said different phospholipid moiety is from about 35 mg to about
2500 mg.
18. The pharmaceutical composition of claim 14, wherein the total
amount of said first valproic acid or said pharmaceutically
acceptable derivative thereof covalently bonded to said
phospholipid moiety and said second valproic acid or said
pharmaceutically acceptable derivative thereof covalently bonded to
said different phospholipid moiety is from about 70 mg to about 560
mg.
19. The pharmaceutical composition of claim 14, wherein said
combination exhibits greater therapeutic effects, prolonged
therapeutic effects, or greater and prolonged therapeutic effects,
on central nervous system disorders than a composition comprising
only said valproic acid or pharmaceutically acceptable derivative
thereof covalently bonded to a phospholipid moiety, or only said
second valproic acid or pharmaceutically acceptable derivative
thereof covalently bonded to said different phospholipid
moiety.
20. The pharmaceutical composition of claim 14, wherein said
valproic acid or pharmaceutically acceptable derivative thereof
covalently bonded to said phospholipid moiety is
1-palmitoyl-2-valproyl-sn-glycero-3-phosphati- dyl-choline and said
second valproic acid or pharmaceutically acceptable derivative
thereof covalently bonded to said different phospholipid moiety is
1-stearoyl-2-valproyl-sn-glycero-3-phosphatidyl-choline.
21. The pharmaceutical composition of claim 20, wherein
1-palmitoyl-2-valproyl-sn-glycero-3-phosphatidyl-choline and
1-stearoyl-2-valproyl-sn-glycero-3-phosphatidyl-choline are in a
ratio of from about 1:20 to about 1:2 by weight.
22. The pharmaceutical composition of claim 20, wherein
1-palmitoyl-2-valproyl-sn-glycero-3-phosphatidyl-choline and
1-stearoyl-2-valproyl-sn-glycero-3-phosphatidyl-choline are in a
ratio of from about 1:5 to about 1:7 by weight.
23. The pharmaceutical composition of claim 20, which is suitable
for oral administration, intravenous administration, or rectal
administration.
24. A method of reducing side effects of valproic acid or
pharmaceutically acceptable derivative thereof by administering
said valproic acid or pharmaceutically acceptable derivative in the
form of a composition as claimed in claim 1.
25. A method of reducing interactions of valproic acid or
pharmaceutically acceptable derivative thereof with other
therapeutic agents by administering said valproic acid or
pharmaceutically acceptable derivative in the form of a composition
as claimed in claim 1.
26. A method of increasing valproic acid or pharmaceutically
acceptable derivative thereof efficacy by administering said
valproic acid or pharmaceutically acceptable derivative in the form
of a composition as claimed in claim 1.
27. A compound comprising valproic acid or pharmaceutically
acceptable derivative thereof covalently bonded to a phospholipid
moiety.
28. The compound of claim 27 wherein said phophoslipid moiety is
1-stearoyl-sn-glycero-3-phosphorylcholine.
29. The compound of claim 27 wherein said phophoslipid moiety is
1-palmitoyl-sn-glycero-3-phosphorylcholine.
30. A method for the treatment of a central nervous system disorder
in a mammal comprising administering to a mammal in need of
treatment, a pharmaceutical composition comprising a
therapeutically effective amount of valproic acid or
pharmaceutically acceptable derivative thereof covalently bonded to
a phospholipid moiety; a pharmaceutically acceptable carrier; said
composition providing a therapeutic effect after
administration.
31. The method according to claim 30, wherein the central nervous
system disorder is selected from epilepsy, migraine, bipolar
disorders and pain.
32. The method according to claim 30, wherein the central nervous
system disorder is epilepsy.
33. The method according to claim 30, wherein said said
phophoslipid moiety is
1-stearoyl-sn-glycero-3-phosphorylcholine.
34. The method according to claim 30, wherein said said
phophoslipid moiety is 1-palmitoyl-sn-glycero-3-phosphorylcholine.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to compounds, which are
phospholipid derivatives of valproic acid, to compositions
comprising said compounds and their use for treating epilepsy,
migraine, bipolar disorders and pain.
BACKGROUND OF THE INVENTION
[0002] Epilepsy is a neurological disease that is characterized by
paroxysmal transient disturbances of the electrical activity of the
brain. Epileptic seizures may be partial or focal seizures that are
restricted to a particular locus within the brain, or generalized
seizures which can result in abnormal activity throughout the
brain. The disturbances of brain function during an epileptic
attack may be manifested as psychic or sensory incidents such as
amnesia, hallucinations, djvu states etc., as abnormal motor
phenomenon such as spasms or whole body convulsions or as loss of
consciousness. In extreme cases, epilepsy can degenerate into
status epilepticus which may be fatal (DeLorenzo et al.-J. Clin
Neurophysiol. (1995) 12: 316-325).
[0003] Valproic acid (VPA) and its sodium salt (sodium valproate,
NaVPA) are among the most prescribed anti-epileptic drugs. These
drags are also effective in the treatment of bipolar disorders and
in prophylaxis of migraines.
[0004] Although the clinical usefulness of valproic acid is well
established, this compound suffers major drawbacks. Treatment with
VPA is associated with adverse side effects such as
gastro-intestinal irritation, bone marrow suppression (especially
manifested as aplastic anemia and thrombocytopenia), and hepatic
dysfunction. VPA has also been reported to have teratogenic effects
and patients treated with VPA may experience nausea, vomiting,
dizziness, confusion or sedation.
[0005] Another drawback of valproic acid is its short half-life due
to rapid clearance of the drug. As a result plasma levels of VPA
fluctuate during chronic treatment and the drug has to be
administered several times a day even as a sustained release
formulation. In addition, valproic acid, which is a liquid, is less
desirable for use as an oral dosage form. The sodium valproate, on
the other hand, is solid, but being hygroscopic is characterized by
poor stability.
[0006] Efforts have been made in order to overcome the VPA-induced
side effects and the disadvantageous physical and pharmacokinetic
properties of the drug. Most approaches that have been taken
involve modification of the VPA molecule. However, although some of
the modified drugs were devoid of adverse side effects, in many
cases they also lost the therapeutic effect or were much less
potent.
[0007] Mergen et al (J. Pharm. Pharmacol. (1991), 43: 815-816)
describe conjugates of valproic acid with 1,3-dipalmitoylglycerol,
1,2-dipalmitoylglycerol or 1,3-diaminopalmitoyl-propan-2-ol.
According to the Mergen et al.'s publication, only the latter
compound was found to have antiepileptic activity, while both
conjugates of VPA with the diglycerides were inactive.
[0008] Hadad et al. (Biopharmaceutics & Drug Disposition
(1993), 14: 51-59) investigated the anticonvulsant activity of
1,4-butanediol divalproate, glyceryl trivalproate and valpromide in
comparison to valproic acid. Their study demonstrated that only
1,4-butanediol divalproate, in one of the model systems tested, had
a better protective index value than VPA.
[0009] U.S. Pat. No. 4,654,370 to Marriott and Paris discloses
glycerides esterified with one or two moles of valproic acid. These
compounds have been found to have the same useful therapeutic
effect as valproic acid alone but without causing gastric
irritation.
[0010] U.S. Pat. Nos. 4,988,731 and 5,212,326 both to Meade,
disclose oligomers having 1:1 molar ratio of sodium valproate and
valproic acid which have physiological properties similar to those
of valproic acid or sodium valproate but show superior stability
characteristics.
[0011] U.S. Pat. No. 4,558,070 to Bauer and Shada discloses a
stable complex between valproic acid and potassium, cesium or
rubidium which may be formed by combining four moles of valproic
acid with one mole of the alkali metal ion. The alkali metal salts
of valproic acid were reported to have improved stability.
[0012] Despite continuous efforts in the field, it is still an
unmet need to provide an anti-epileptic medication with improved
pharmacokinetic properties and overall superior therapeutic
index.
SUMMARY OF THE INVENTION
[0013] The present invention provides pharmaceutical compositions
comprising, as an active ingredient, a compound comprising valproic
acid or a pharmaceutically acceptable derivative thereof which is
covalently bonded to a phospholipid moiety. In preferred
embodiments of the invention, the phospholipid moiety is selected
from plasmalogens, phosphatidic acids and phosphoglycerides. More
preferred are compounds, wherein said phospholipid moiety is
lysophosphatidyl-ethanolanine, N-mono-(C.sub.1-4)-alkyl,
N,N-di-(C.sub.1-4)-alkyl and quaternary derivatives of the amines
thereof.
[0014] Most preferred embodiments, in accordance with the
invention, are compositions comprising phospholipid derivatives of
valproic acid (hereinafter referred to as DP-VPA) wherein valproic
acid is covalently linked as an ester at the sn-2 position of a
phospholipid moiety.
[0015] Currently the most preferred DP-VPA compounds are
1-Palmitoyl-2-valproyl-sn-glycero-3-phosphatidylcholine, also
referred to as 1-hexadecanoyl-sn-glycero-3-phosphorylcholine
(hereinafter denoted as C.sub.16-DP-VPA) and
1-Stearoyl-2-valproyl-sn-glycero-3-phosphatidylcholi- ne, also
referred to as 1-octadecanoyl-sn-glycero-3-phosphorylcholine
(hereinafter denoted as C.sub.18-DP-VPA).
[0016] According to preferred embodiments of the present invention,
the pharmaceutical compositions comprise a mixture of DP-VPA
compounds, more preferably a mixture of C.sub.16-DP-VPA and
C.sub.18-DP-VPA (hereinafter denoted as
C.sub.16/C.sub.18-DP-VPA).
[0017] In one preferred embodiment the ratio of C.sub.16-DP-VPA to
C.sub.18-DP-VPA in the C.sub.16/C.sub.18-DP-VPA mixture is from
around 1:20 to around 1:2 by weight. Most preferred are mixtures
wherein the ratio of C.sub.16-DP-VPA to C.sub.18-DP-VPA is from
around 1:5 to around 1:7 w/w (equivalent to 15.+-.5%
C.sub.16-DP-VPA:85.+-.5% C.sub.18-DP-VPA (w/w)).
[0018] The compounds and compositions of the invention are useful
for the treatment of central nervous system disorders including,
but not limited to, epilepsy, migraines, chronic pain and bipolar
disorders.
[0019] Thus, according to yet another embodiment of the present
invention, there is provided a method for the treatment of a
central nervous system disorder in a subject, comprising the step
of administering to a patient in need thereof a therapeutically
effective amount of a compound or a pharmaceutical composition in
accordance with the invention.
[0020] Further objects of the present invention will become
apparent to those skilled in the art upon further review of the
following disclosure, including the detailed descriptions of
specific embodiments of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 depicts a typical HPLC chromatogram of a
C.sub.16/C.sub.18-DP-VPA composition, where the C.sub.16-DP-VPA to
C.sub.18-DP-VPA ratio is 15%:85.degree./, by weight
[0022] FIGS. 2A-B depict plasma concentrations of C.sub.16-DP-VPA
(2A) and C.sub.18-DP-VPA (2B) measured at different time points
following a single oral administration to human subjects of 0.625 g
of C.sub.16/C.sub.18-DP-VPA (C.sub.16/C.sub.18 ratio=13%: 87%
w/w).
DETAILED DESCRIPTION THE INVENTION
[0023] The present invention relates to phospholipid derivatives of
valproic acid, to pharmaceutical compositions comprising these
compounds and mixtures thereof and to their use in the treatment of
neurological disorders.
[0024] DP-VPA molecules are disclosed in U.S. patent application
Ser. No. 08/479,959 and International Patent Publication WO
94/22483, the disclosure of which is herein incorporated by
reference.
[0025] Specifically disclosed in the abovementioned applications is
a molecule, referred to as "TVA 16", which is a 1:1 ester of
valproic acid with 1-hexadecanoyl-sn-glycero-3-phosphorylcholine.
TVA 16 was shown to have significant anticonvulsant activity and to
be more potent than sodium valproate. In the present application,
the 1:1 ester of valproic acid with
1-hexadecanoyl-sn-glycero-3-phosphorylcholine, or in its chemical
name 1-Palmitoyl-2-valproyl-sn-glycero-3-phosphatidylcholine, is
hereinafter referred to as C.sub.16-DP-VPA.
[0026] Another embodiment, disclosed in the present application, is
a 1:1 ester of valproic acid with
1-octadecanoyl-sn-glycero-3-phosphorylcholine- , or in its chemical
name 1-Stearoyl-2-valproyl-sn-glycero-3-phosphatidylc- holine. This
molecule is hereinafter referred to as C.sub.18-DP-VPA.
[0027] The DP-VPA compounds of the invention include conjugates of
valproic acid, or a pharmaceutically acceptable derivative thereof,
with any phospholipid, preferably a phosphoglyceride. Suitable
phospholipids include, but are not limited to, plasmalogens,
phosphatidic acids and phospho-ester derivatives thereof. Preferred
phospholipid moieties, in accordance with he invention, include
lysophosphatidyl-ethanolamine, N-mono-(C.sub.1-4)-alkyl,
N,N-di-(C.sub.14)-alkyl and quaternary derivatives of the amines
thereof. Currently, the most preferred phospholipid in the
compounds of the invention is phosphatidylcholine.
[0028] The choice of the fatty acid residue at position sn-1 of a
glycero-phospholipid moiety is specifically discussed below in
connection with the preferred compounds in accordance with the
invention. However, it should be appreciated that VPA or its
pharmaceutically acceptable derivative may be covalently linked to
the phospholipid moiety at positions sn-1, sn-2 or linked to the
phospholipid head group at position sn-3. Accordingly, it is
possible that VPA or its derivative is released by cleavage by the
respective phospholipases, PLA.sub.1, PLA.sub.2, PLC and PLD as
depicted in the following scheme 1. 1
[0029] X=H or a polar head group.
[0030] In preferred embodiments of the invention, VPA, or its
pharmaceutically acceptable derivative, is joined to the
phospholipid via an ester linkage at position sn-2, thus enabling
release of VPA by phospholipases A.sub.2. In particularly preferred
embodiments, VPA is covalently linked by an ester bond to the sn-2
position of phoshatidylcholine.
[0031] The term "pharmaceutically acceptable derivatives of VPA" as
used in the specification refers to pharmaceutically acceptable
analogs of valproic acid having similar therapeutic activity. This
includes derivatives of VPA with saturated or unsaturated carbon
chains having one or more double and/or triple bonds.
Pharmaceutically acceptable substituent on the carbon atoms of the
molecules are also allowed and may include, for example, halogen
atoms or lower alkyl groups comprising 1-5 carbon atoms. Amides of
VPA and its analogs as mentioned above are also included within the
scope of the invention. Furthermore, for those compounds having a
chiral centre of asymmetry, the compounds of the present invention
include optically active isomers, racemates or preferred mixtures
thereof.
[0032] It should be appreciated that within the scope of the
invention are also pharmaceutically acceptable salts of the DP-VPA
compounds. The term "pharmaceutically acceptable salts" means
non-toxic salts of the compounds of the invention including, but
not limited to, sodium, potassium, calcium, magnesium, ammonium,
alkyl ammonium or amine derived salts.
[0033] Although both C.sub.18-DP-VPA and C.sub.16-DP-VPA are potent
anticonvulsant agents having similar efficacies, it has now been
unexpectedly found that the two compounds differ in their
pharmacokinetic profiles. The C.sub.16-DP-VPA compound, following a
single oral administration, exhibits a significantly prolonged
half-life in plasma in comparison to the half-life of
C.sub.18-DP-VPA. However, the plasma concentrations of
C.sub.18-DP-VPA were found to reach peak levels at a later time
point in comparison to the peak levels of the C.sub.16-DP-VPA
molecule.
[0034] It is now disclosed, for the fist time, that mixtures of
C.sub.16-DP-VPA and C.sub.18-DP-VPA (herein referred to as
C.sub.16/C.sub.18-DP-VPA) offer an advantage by exhibiting higher
neuroprotective values and prolonged therapeutic effect in
comparison to the effect of compositions comprising either
C.sub.16-DP-VPA or C.sub.18-DP-VPA alone.
[0035] Preferred compositions, in accordance with the invention,
are those wherein the C.sub.16-DP-VPA to C.sub.18-DP-VPA ratio in
the C.sub.16/C.sub.18-DP-VPA mixture is from around 1:20 to around
1:2 (by weight). Most preferred are mixtures wherein the ratio of
C.sub.16-DP-VPA to C.sub.18-DP-VPA is around 15.+-.5%: 85+5%
(w/w).
[0036] Without wishing to be limited to a single mechanism or
theory, it is suggested that the length of the alkyl moiety
esterified at position sn-1 of the phospholipid may determine the
lipophilicity of the DP-VPA molecule, and thus also its transport
across cellular membranes.
[0037] Alternatively, again without wishing to be limited to a
single mechanism or theory, the fatty acid residue at position sn-1
may determine the properties of the DP-VPA conjugate as a substrate
for phospholipases, thus affecting the regulated release of
valproic acid, for example, by elevated activity of phospholipase
A.sub.2 (PLA.sub.2) at the diseased site. Phospholipases A.sub.2
are a family of esterases that hydrolyze the sn-2 ester bonds in
phosphoglyceride molecules. It has been shown that in disorders
such as epilepsy, PLA.sub.2 activation coincides with epileptic
seizures (Flynn and Wecker (1987) J. Neurochem. 48: 1178-84; Bazan,
et al. (1986) Adv. Neurol. 44: 879-902).
[0038] Also associated with elevated phospholipase A.sub.2
activity, are bipolar disorders and some types of pain and migraine
that are associated with inflammatory processes (Horrobin and
Bennett (1999) Prostaglandins Leukot Essent Fatty Acids 60:
141-167).
[0039] The compounds according to the invention, being hydrophobic
in nature, may penetrate biological membranes and barriers, thus
facilitating the transport of the drug into cells or organs, for
example, into the brain where their effect is needed.
[0040] It may be envisaged that regulated release of the valproic
acid moiety at the diseased target site may even further improve
the therapeutic index of the drug, as the efficacy the drug is
expected to increase while potential side effects and toxicity are
reduced. Valproic acid may be released by cleavage of the DP-VPA
compound at position sn-2 of the phospholipid by phospholipase
A.sub.2 or any other lipase or esterase. However, it may not be
excluded that the active drug may be different from the original
parent drug molecule, VPA, with a chemical group(s) being removed
from or added to its structure while being released from its
intracellular transporting adjuvant or as a result of physiological
phospholipid metabolism.
[0041] It is important to note that the conjugate of the invention,
namely the valproic acid or its pharmaceutically acceptable
derivative covalently linked to the phospholipid moiety, may be
active per se. Alternatively, the covalent bond of the lipid-drug
conjugate may, under certain circumstances, be cleaved to release
the pharmacologically active drug. In the latter case, the compound
of the invention may be regarded as a prodrug, in the sense that
the therapeutic agent is released from its transporting
adjuvant.
[0042] Irrespective of the exact mechanism of action, it is evident
that the compounds of the invention have an improved therapeutic
profile and are more effective comparing to VPA in at least two
aspects: (i) increased efficacy, and (ii) decreased side
effects.
[0043] The DP-VPA compounds were found to be effective at much
lower equivalent molar doses compared to the doses currently used
for VPA. The reduced therapeutic doses in turn reduce the
toxicological risk, accompanying side effects and also reduce the
risk of undesirable interactions with other drugs. In addition, the
DP-VPA molecules have been found to exhibit significantly improved
pharmacokinetic properties compared to VPA (e.g. substantially
increased half-life in serum and in brain tissue). Thus, the DP-VPA
molecules represent a class of superior anti-epileptic drugs.
[0044] Furthermore, the preferred pharmaceutical compositions in
accordance with the invention, i.e. compositions comprising a
mixture of both C.sub.16-DP-VPA and C.sub.18-DP-VPA, may
conveniently be prepared from natural sources.
[0045] It would be highly advantageous to have DP-VPA molecules
that can be obtained from starting material which can be derived
from natural sources by a relatively simple procedure. Such
starting material, which is readily available, is lyso-lecithin
obtained from egg or soybean lecithins. The soybean, being a
non-animal source, is the preferred starting material in the
preparation of medicaments for human use. In typical hydrogenated
preparations derived from soybean the content of
1-palmitoyl-lysolecithin is around 8-18% and the content of
1-stearoyl-lysolecithin is around 80-90% (by weight).
[0046] Pure C.sub.16-DP-VPA and C.sub.18-DP-VPA molecules may be
chemically synthesized de novo. Alternatively, pure C.sub.16-DP-VPA
and C.sub.18-DP-VPA compounds may be prepared by using staring
materials obtainable from natural sources, i.e
C.sub.16-lyso-lecithin and C.sub.18-lyso-lecithin may be isolated
and purified, for example, from eggs or soybeans, and then acylated
by VPA (semi-natural preparation).
[0047] C.sub.16-DP-VPA and C.sub.18-DP-VPA, in particular when used
as mixtures within a preferred range of ratios in accordance with
the present invention, have been shown, to exhibit significantly
improved therapeutic properties. The advantageous properties were
exemplified by the substantially increased half-life of DP-VPA in
serum and the high efficacy of the drug. The improved residency
time in the serum may facilitate the attainment of steady-state
drug levels with reduced fluctuation around the therapeutic blood
level and reduction in the frequency of drug administration to once
or twice per day.
[0048] The compositions of the invention can be administered
orally, parenterally, (for example by intravenous drip or
intraperitoneal, subcutaneous, or intramuscular injection),
topically, (for example by nasal application or inhalation) or
rectally. Oral administration is a currently more preferred route
of administration.
[0049] Suitable formulations for administration of the compounds of
the invention, whether used separately or as a mixture, include,
but are not limited to, powders, granules, emulsions, suspensions
or solutions in water or non-aqueous media, in the dosage form of
tablets, capsules, syrups or solutions.
[0050] For oral administration, DP-VPA amounts of from about 0.5 to
20 mg/kg body weight per day are useful, preferably 1 to 8 mg/kg
body weight per day. Dosing will be dependent on the severity of
the symptoms and on the responsiveness of the subject to the DP-VPA
drug. A physician or other persons of ordinary skill in the art can
easily determine optimum dosages and dosage form as well as dosage
regimen and means of administration.
[0051] The invention will now be illustrated by the following
non-limiting examples.
EXAMPLES
Example 1
Synthesis of DP-VPA
[0052] The synthesis of DP-VPA is a two-stage process. The first
stage is aimed at obtaining valproic anhydride by heating of
valproic acid in a solution of acetic anhydride under catalysis of
pyridine. In the second stage, DP-VPA is prepared by interaction of
valproic anhydride with lyso-lecithin. This reaction is conducted
in a solution of valproic anhydride by catalysis of
4-dimethylaminopyridine at 90-100.degree. C.
[0053] Extraction and purification of the product obtained are
carried out in four stages. The first stage of purification is
performed by extraction of the un-reacted valproic anhydride,
valproic acid and catalyst (4-aminopyridine) in acetone. The crude
product obtained is precipitated and separated from solution at the
second stage. The solid product obtained is washed from the
remaining compounds at the third stage. Finally, the product is
re-crystallized several times from an acetone/ethanol solution and
the residual solvents are removed under vacuum. Yield of the
product is around 80%. 2
[0054] The 1-Palmitoyl-2-valproyl-sn-glycero-3-phosphatidylcholine
(C.sub.16-DP-VPA) and
1-Stearoyl-2-valproyl-sn-glycero-3-phosphatidylchol- ine
(C.sub.18-DP-VPA) compounds were prepared using, respectively,
lyso-stearic- and lyso-palmitic-phophatidylcholines.
[0055] The lyso-stearic- and lyso-palmitic-phophatidylcholines may
be purified from a natural source (e.g. egg or soybean) by means
and procedures well known in the art (F. Gunstone (1999) Fatty Acid
and Lipid Chemistry, pp. 87-99, Aspen Publishers, Inc.).
[0056] Alternatively these starting materials may be obtained by
chemical synthesis procedures as known in the art.
Example 2
Synthesis of C.sub.16/C.sub.18-DP-VPA
[0057] Mixtures of C.sub.16/C.sub.18-DP-VPA were prepared by the
same procedure as described in Example 1 for the preparation of
DP-VPA. The difference was that in the case of the mixture
compositions the interaction of valproic anhydride was with
lyso-lecithin, which was obtained from soybean and saturated by
hydrogenation (S VPC-3 from Lipoid GmbH, Ludwigshafen,
Germany).
Example 3
Analysis of DP-VPA compounds
[0058] C.sub.16/C.sub.18-DP-VPA mixtures synthesized as described
above in Example 2 were subjected to analytical assays for
characterization and proof of structure. Analytical results of a
product containing
1-Palmitoyl-2-valproyl-sn-glycero-3-phosphatidylcholine
(C.sub.16-DP-VPA) and
1-Stearoyl-2-valproyl-sn-glycero-3-phosphatidylcholine
(C.sub.18-DP-VPA), at a ratio of 13%:87% (by weight) are given
below.
[0059] Mass Spectroscopy
[0060] The mass of the protonated DP-VPA molecules as determined by
ESI (+) is 622.4 to 622.8 for C.sub.16-DP-VPA, and 650.4 to 650.8
for C.sub.18-DP-VPA. This agrees well with the calculated molecular
weight values.
[0061] Elementary Analysis
[0062] Calculated for M.H.sub.2O: C60.93%, H 10.25%, N 2.11%, P
4.66% (M is corrected for the content of
1-palmitoyl-2-valproyl-sn-glycero-3 phosphatidylcholine).
[0063] The average values found were C 60.72%, H 10.58/o, N 2.09/o,
P 4.560/. These values agree well with the calculated values.
[0064] Thin Layer Chromatograph (TLC) Analysis
[0065] A TLC is performed on silica gel 60 F.sub.254 on aluminium
sheet with a chloroform:methanol:water (65:35:5, v/v) fluent. The
spray reagent for detection is a mixture of 4-methoxybenzaldehyde
(5 ml), sulphuric acid 95-98% (5 ml), ethanol (100 ml) and glacial
acetic acid (1 ml). The sheet is sprayed with this reagent and then
heated with hot air at 120-150.degree. C.
[0066] The TLC analysis results show that there is one spot at an
R.sub.f of 0.58 to 0.60.
[0067] Analytical NMR Data
[0068] The typical NMR data given below are for proton, carbon-13
and phosphorus-31. .sup.1H NMR(CDCl.sub.3), .delta. (ppm):
0.84-0.90 (m, 9H), 1.24-1.27 (broad s)+1.31-1.41 (m) (both 34H),
1.50-1.59 (m, 4H), 2.21-2.28 (t, 2H), 2.29-2.37 (m, 1H), 3.35 (s,
9H), 3.77-3.78 (broad s, 2H), 3.88-3.96 (m,2H), 4.06-4.14 (m, 1H),
4.30 (broad s, 2H), 4.40-4.46 (d, 1H), 5.18 (m, 1H).
[0069] .sup.13C NMR(CDCl.sub.3), .delta. (ppm): 8.62 (CH.sub.3),
22.65 (CH.sub.3), 62.99 [(CH.sub.3).sub.3N], 29.17, 30.93, 33.15,
39.92, 43.07, 53.86, 67.97, 71.89, 74.99, 78.91 (CH.sub.2 and CH),
182.21 (CO), 184.43 (CO).
[0070] .sup.31P NMR(CDCl.sub.3), .delta. (ppm): -0.29 (respectively
to H.sub.3PO.sub.4 in D.sub.2O).
[0071] HPLC Analysis
[0072] DP-VPA is analysed by HPLC using the following
conditions:
1 Instrument: Liquid chromatograph equipped with integrating device
Column: Zorbax Eclipse XDB C18, 5.mu., 4.6 .times. 250 mm Mobile
phase: Methanol - Acetonitrile - Water (85:15:5 v/v) Flow rate: 1.0
mL/min Detection: UV @ 220 nm Injection volume: 20 .mu.L
[0073] Typical retention times are given in the following
table:
2 Typical Retention time, Name of the compound min
1-Palmitoyl-lysolecithine (potential impurity) 6
1-Stearoyl-lysolecithine (potential impurity) 8 1-Palmitoyl-DP-VPA
12 1-Stearoyl-DP-VPA 18
[0074] A typical HPLC chromatogram of
C.sub.16-DP-VPA/C.sub.18-DP-VPA mixture at a ratio of 15%:85% (by
weight) which was analysed as described above is depicted in FIG.
1.
Example 4
Toxicology and Safety Studies in Humans
[0075] A Phase I safety and tolerability clinical trial has been
carried out using C.sub.16/C.sub.18-DP-VPA mixture
(C.sub.16-DP-VPA/C.sub.18-DP-V- PA at a ratio of 15%:85% w/w) in
solution of 5% Poloxamer F-127+0.5% Tween-80 and the oral route of
administration.
[0076] The design of this study was double blind, placebo
randomized. It was divided into a single administration part and a
part in which there was repeated daily administration for 7
consecutive days. In each part the doses were increased at
intervals of 7 days if the previous dose was well tolerated.
[0077] Five doses ranging form 0.3125 g to 5 g of DP-VPA were
administered as single doses in the first part of the study and 3
doses (0.3125 g, 0.625 g and 1.25 g) were administered as repeated
doses in the second part of the study. Fifty six subjects in total
were enrolled in this study: 29 in the first part and 27 in, the
second part.
[0078] In the first part, nausea and vomiting were the most
commonly reported adverse effects, the incidence of which was
highest in the highest dose group (DP-VPA 5 g) with 3 of the 6
subjects reporting it. Two of the 6 subjects in the second highest
dose group (DP-VPA 2.5 g) reported nausea and vomiting. Headache,
diarrhoea, abdominal pain and dizziness were also reported but in
the investigator's opinion they were probably not study drug
related.
[0079] With regard to the laboratory results, vital signs and ECG
parameters, no trends were seen and all results remained within
acceptable parameters for all subjects.
[0080] In the second part fewer adverse effects occurred and only 3
(burning stomach and abdominal pain) were considered to be probably
related to the drug as they occurred soon after administration.
There were no incidences of nausea and the 1 episode of vomiting
occurred more than 24 h after administration and was not related to
the study drug.
[0081] From the point of view of the vital signs, ECGs, laboratory
tests, urinalysis and physical examinations the tolerability was
very good.
[0082] Conclusions: In both the single and repeated administration
parts of this study the clinical and biological tolerability was
found to be very good at DP-VPA doses of up to 2.5 g. It can be
concluded that the DP-VPA's toxicological profile is significantly
improved compared to that for the parent drug VPA.
Example 5
Pharmacokinetics Studies in Humans
[0083] In order to assess the pharmacokinetic properties of the
C.sub.16-DP-VPA and C.sub.18-DP-VPA compounds, the plasma levels of
these compounds were monitored in human subjects.
[0084] Healthy male volunteers, 18-40 year old, (7 individuals for
each dose tested) received, by a single oral administration, 0.3125
g, 0.625 g or 1.25 g of C.sub.16/C.sub.18-DP-VPA mixture at a ratio
of C.sub.16/C.sub.18=13%: 87% (w/w). Blood samples, 10 ml each,
were drawn from each individual at the time points after the
administration of the drug, as indicated. The samples were
centrifuged at 4.degree. C. at 1100 g for 10 minutes immediately
after collection. Plasma levels of C.sub.16-DP-VPA and
C.sub.18-DP-VPA were determined using a LC-MS/MS technique. The
plasma concentration profiles of C.sub.16-DP-VPA and
C.sub.18-DP-VPA as monitored for 24 hours following a single oral
administration 0.625 g of C.sub.16/C.sub.18-DP-VPA are shown,
respectively, in FIGS. 2A and 2B.
[0085] As can be seen from the results of the human study, the
C.sub.16-DP-VPA and C.sub.18-DP-VPA compounds have different
kinetic profiles. While the peak concentration of C.sub.16-DP-VPA
in the plasma was reached at 6 hours after the administering of the
drug, the peak of C.sub.18-DP-VPA was reached two hours later, at 8
hours post administration
[0086] The terminal plasma half-life (t.sub.1/2) for the
C.sub.16-DP-VPA and C.sub.18-DP-VPA compounds was calculated form
their plasma concentration-tie profiles. It was found that the
calculated t.sub.1/2 values for the two compounds were
significantly different; t.sub.1/2 for C.sub.16-DP-VPA was
14.0.+-.0.6 hours compared to 8.3.+-.1.3 hours for
C.sub.18-DP-VPA.
[0087] The t.sub.1/2 measured for the global DP-VPA was 10.6.+-.1.2
hours, a value that combines the pharmacokinetic profiles of both
the C.sub.16-DP-VPA and C.sub.18-DP-VPA compounds.
[0088] Plasma concentration (.mu.g/ml) of C.sub.16-DP-VPA and of
C.sub.18-DP-VPA measured in samples collected at various time
points following a single oral administration of 0.625 g
C.sub.16/C.sub.18-DP-VP- A are summarized in Table 1.
3TABLE 1 C.sub.16-DP-VPA and of C.sub.18-DP-VPA concentrations in
humans plasma following a single oral administration of
C.sub.16/C.sub.18-DP-VPA. Time C.sub.16-DP-VPA C.sub.18-DP-VPA
Ratio (hours) (.mu.g/ml) (.mu.g/ml) C.sub.18/C.sub.16 1 0.013 .+-.
0.034 0.000 .+-. 0.000 3 0.167 .+-. 0.094 0.058 .+-. 0.043 0.35 6
0.397 .+-. 0.172 0.818 .+-. 0.292 2.1 8 0.385 .+-. 0.140 1.175 .+-.
0.137 3.1 10 0.368 .+-. 0.182 0.949 .+-. 0.254 2.6 12 0.318 .+-.
0.150 0.698 .+-. 0.163 2.2
[0089] As can be seen from the results in Table 1, the observed
ratios of C.sub.18-DP-VPA/C.sub.16-DP-VPA were different from the
expected ratio of 6.7 (C.sub.18-DP-VPA: C.sub.16-DP-VPA ratio 87%:
13% (by weight)).
[0090] Surprisingly, the presentation of the C.sub.16-DP-VPA
compound in the plasma was found to be higher tan its proportion in
the administered mixture. This phenomenon was more pronounced at
the shorter time points, i.e. less than 6 hours following the
administration of C.sub.16/C.sub.18-DP-VPA.
[0091] The highest ratio of C.sub.18/C.sub.16, i.e. 3.1 (which is
still below the expected ratio of 6.7) was reached at 8 hours
following the administration of C.sub.16/C.sub.18-DP-VPA. At this
point the levels of C.sub.18-DP-VPA reach their peak concentration
in the plasma.
[0092] These observations indicate that the C.sub.16-DP-VPA and
C.sub.18-DP-VPA compounds demonstrate different pharmacokinetic
profiles.
Example 6
Anti-Convulsive Effect of C.sub.16DP-VPA; C.sub.18-DP-VPA and
C16/C.sub.18-DP-VPA Mixtures (Efficacy Study)
[0093] The anti-epileptic efficacies of C.sub.16-DP-VPA,
C.sub.18-DP-VPA and mixtures comprising both C.sub.16-DP-VPA and
C.sub.18-DP-VPA were evaluated in mice. The protective effect of
the compounds was compared at different time points following
chemical seizure induction by pentylenetetrazol (PTZ).
[0094] The pentylenetetrazol (PTZ) induced seizure model in mice is
an established animal model system for epilepsy. Subcutaneous
injection of PTZ into control animals results in the following
sequence of events: myoclonic jerks within 1-2 mins, followed by
clonic and clonic-tonic seizures each lasting approximately 5-10
secs with the severity of seizures increasing with time for up to
30 mins. 80% of the first seizures are-observed within 5 mins, and
100% within 20 mins. The second seizures usually follow within 6-10
mins and subsequent seizures (if any) every 6 mins.
[0095] CD-1 mice (25-30 g) were pre-treated by subcutaneous (s.c.)
injection of either C.sub.16-DP-VPA or C.sub.18-DP-VPA or a mixture
thereof. The amounts used were equivalent to 40 mg/kg VPA. After
different times as indicated, 1, 2 or 4 hours, a convulsive dose of
pentylenetetrazol (85-100 mg/kg) was subcutaneously injected into
the mice. The animals were monitored for one hour following the PTZ
administration for the occurrence of episodes of clonic spasms
persisting for at least 5 sec. The protection effect was calculated
as the number of animals that did not experience a second seizure
divided by the total number of animals tested.
[0096] In Tables 2 A-D are shown the results of PTZ-induced
seizures test as described above, wherein the tested compositions
were as follows:
[0097] Table A--C.sub.16-DP-VPA 100%
[0098] Table B--C.sub.16-DP-VPA/C.sub.18-DP-VPA ratio 50/50 (by
weight)
[0099] Table C--C.sub.16-DP-VPA/C.sub.18-DP-VPA ratio 10/90 (by
weight)
[0100] Table D--C.sub.18-DP-VPA 100%
[0101] n=the number of animals experiencing a seizure;
[0102] N=the total number of animals in the assay.
4TABLES 2 A-D PTZ-induced seizures test in mice Time (h) Second
seizure (n//N) % Protection A) C.sub.16-DP-VPA-100% 1 4/8 50 2 6/8
25 4 5/8 38 B) C.sub.16-DP-VPA/C.sub.18-DP-VPA:50/50 1 6/7 14 2 6/7
14 4 5/8 38 C) C.sub.16-DP-VPA/C.sub.18-DP-VPA:10/90 1 5/7 29 2 6/7
14 4 2/8 75 D) C.sub.18-DP-VPA-100% 1 5/6 17 2 6/7 14 4 1/7 86
[0103] As can be seen in Table 2, the C.sub.18-DP-VPA compound is
more effective in prevention of second seizures, showing 86%
protection compared to a maximum of 50% protection obtained by 100%
C.sub.16-DP-VPA.
[0104] The C.sub.16-DP-VPA/C.sub.18-DP-VPA mixtures demonstrated
intermediate behaviour, with the effect of the
C.sub.16-DP-VPA/C.sub.18-D- P-VPA at a ratio of 10/90 (Table C)
being closer to that obtained with the pure C.sub.18-DP-VPA
compound. However, protection was more apparent at 1 hour with the
10/90 mixture than with 100% C.sub.18-DP-VPA.
[0105] It is also important to note the different kinetics of the
protective effects by the two DP-VPA compounds. The peak activity
of C.sub.18-DP-VPA was obtained 4 hours after the administration of
PTZ, while the pure C.sub.16-DP-VPA reached its maximal therapeutic
effect already within 1 hour.
[0106] Conclusion: although C.sub.16-DP-VPA and C.sub.18-DP-VPA
have similar potency as anti-convulsant (i.e. similar ED.sub.50
values), their therapeutic profiles are different. The
C.sub.16-DP-VPA compound is more effective in preventing seizures
in the first hour after induction of seizures by subcutaneous
administration of PTZ. The C.sub.18-DP-VPA compound, on the other
hand, shows maximal anti-convulsant activity at the later times,
i.e. at four hours after the injection of PTZ (see Table A in
comparison to Table D).
[0107] It is important to note that the tested
C.sub.16-DP-VPA/C.sub.18-DP- -VPA mixtures, in particular the
C.sub.16/C.sub.18 mixture at a ratio of 10:90, behave in a similar
way to the 100% C.sub.18-DP-VPA compound, namely demonstrating high
maximal seizure protection, but over a more prolonged time.
Example 7
Suitable Formulations for Administration of DP-VPA
[0108] The DP-VPA compounds and compositions of the present
invention can be administered to a subject in a number of ways,
which are well known in the art. For example, administration may be
done orally, parenterally, (for example by intravenous drip or
intraperitoneal, subcutaneous, or intramuscular injection),
topically, (for example by nasal application or inhalation) or
rectally.
[0109] Formulations for topical administration may include, but are
not limited to drops, liquids, sprays, powders, suppositories,
creams, gels and ointments. Conventional pharmaceutical carriers,
aqueous, powder or oily bases, thickeners and the like may be
necessary or desirable.
[0110] Formulations for parenteral administration may include, but
are not limited to, sterile aqueous solutions which may also
contain buffers, diluents and other suitable additives.
[0111] Compositions for oral administration may be formulated as
powders or granules, suspensions or solutions in water or
non-aqueous media, in the dosage form of tablets, capsules, syrups
or solutions. The formulation may be designed so to enable modified
controlled release of the active agent. The capsules and tablets
may be coated so to afford site-specific delivery to different
parts of the gastrointestinal tract Thickeners, diluents,
flavorings, dispersing aids, emulsifiers or binders may be
desirable.
[0112] Suitable pharmaceutical excipients that may be included in
the formulations include, but are not limited to, phospholipids,
triglycerides, propylene glycols, polyethylene glycols, poloxamers,
surfactant and co-surfactants.
[0113] Dosing is dependent on the severity of the symptoms and on
the responsiveness of the subject to the DP-VPA drug. Persons of
ordinary skill in the art can easily determine optimum dosages and
dosage form as well as dosage regimen and means of
administration.
[0114] While the present invention has been particularly described,
persons skilled in the art will appreciate that many variations and
modifications can be made. Therefore, the invention is not to be
construed as restricted to the particularly described embodiments,
rather the scope, spirit and concept of the invention will be more
readily understood by reference to the claims which follow.
* * * * *