U.S. patent application number 10/117350 was filed with the patent office on 2003-05-01 for pyridomorphinans and use thereof.
Invention is credited to Ananthan, Subramaniam.
Application Number | 20030083499 10/117350 |
Document ID | / |
Family ID | 26845980 |
Filed Date | 2003-05-01 |
United States Patent
Application |
20030083499 |
Kind Code |
A1 |
Ananthan, Subramaniam |
May 1, 2003 |
Pyridomorphinans and use thereof
Abstract
Compounds represented by the formula: 1 wherein each of Y, X and
R individually is H, OH, alkyl, alkoxy, aryl, halo, CF.sub.3 and
NO.sub.2, provided that at least one of Y, X and R is other than H;
and pharmaceutically acceptable salts thereof are provided.
Compounds of the above formula are useful as analgesics for
treating pain, as immunomodulators and for treating drug abuse.
Inventors: |
Ananthan, Subramaniam;
(Birmingham, AL) |
Correspondence
Address: |
CONNOLLY BOVE LODGE & HUTZ LLP
SUITE 800
1990 M STREET NW
WASHINGTON
DC
20036-3425
US
|
Family ID: |
26845980 |
Appl. No.: |
10/117350 |
Filed: |
April 8, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10117350 |
Apr 8, 2002 |
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09637934 |
Aug 14, 2000 |
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6465479 |
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60148580 |
Aug 13, 1999 |
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60210760 |
Jun 12, 2000 |
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Current U.S.
Class: |
546/40 |
Current CPC
Class: |
A61P 37/02 20180101;
A61P 25/04 20180101; A61P 25/36 20180101; A61P 25/30 20180101; C07D
491/20 20130101 |
Class at
Publication: |
546/40 |
International
Class: |
C07D 491/14 |
Goverment Interests
[0001] This invention was made under Grant DA 08883 from the
National Institute on Drug Abuse.
Claims
What is claimed is:
1. A compound represented by the formula: 5wherein each of Y, X and
R individually is selected from the group consisting of hydrogen,
hydroxy, alkyl, alkoxy, aryl, halo, CF.sub.3 and NO.sub.2, provided
that at least one of Y, X and R is other than hydrogen; and
pharmaceutically acceptable salts thereof.
2. The compound of claim 1 wherein X is H, Y is H and R is Cl.
3. The compound of claim 1 wherein X is H, Y is H and R is F.
4. The compound of claim 1 wherein X is H, Y is H and R is Br.
5. The compound of claim 1 wherein X is H, Y is H and R is I.
6. The compound of claim 1 wherein X is H, Y is H and R is
CH.sub.3.
7. The compound of claim 1 wherein X is H, Y is H and R is
OCH.sub.3.
8. The compound of claim 1 wherein X is H. Y is H and R is
CF.sub.3.
9. The compound of claim 1 wherein X is H. Y is H and R is
NO.sub.2.
10. The compound of claim 1 wherein X is H, Y is H and R is OH.
11. The compound of claim 1 wherein X is H, Y is H and R is
phenyl.
12. The compound of claim 1 wherein X is Cl, Y is H and R is H.
13. The compound of claim 1 wherein X is H, Y is Cl and R is H.
14. The compound of claim 1 wherein X is Cl, Y is H and R is
Cl.
15. The compound of claim 1 wherein X is H, Y is Cl and R is
Cl.
16. The compound of claim 1 wherein X is Cl, Y is Cl and R is
Cl.
17. A method for treating a patient suffering from pain which
comprises administering to the patient a pain treating effective
amount of at least one compound according to claim 1.
18. The method of claim 17 wherein the administering is i.p.
administering.
19. A method for treating a patient in need of an immunomodulatory
agent which comprises administering to the patient an
immuno-modulatory effective amount of at least one compound
according to claim 1.
20. The method of claim 19 wherein the administering is i.p.
administering.
21. A method for treating a patient suffering from drug abuse which
comprises administering to the patient an effective amount for
treating drug abuse of at least one compound according to claim
1.
22. The method of claim 21 in which the drug abuse comprises
cocaine or methamphetamine abuse.
23. The method of claim 21 wherein the drug abuse comprises opioid
drug abuse.
24. The method of claim 23 wherein the drug abuse comprises heroin
or morphine drug abuse.
25. The method of claim 21 wherein the administering is i.p.
administering.
Description
TECHNICAL FIELD
[0002] The present invention relates to certain pyridomorphinan
compounds and more particularly to naltrexone-derived
pyridomorphinan compounds. Compounds of the present invention
exhibit high .delta. antagonist potency. Moreover, compounds of the
present invention possess .mu. agonist characteristics. Compounds
of the present invention are especially useful as analgesics for
treating patients suffering from pain. Compounds of the present
invention are also suitable for treating drug abuse including
cocaine, methamphetamine and opioids such as morphine and heroin
abuse. Also, compounds of the present invention can be used as
immunomodulatory agents.
BACKGROUND OF INVENTION
[0003] Opioid receptors belong to the superfamily of G-protein
coupled receptors that mediate the analgesic and other
pharmacological actions of morphine and related opioid drugs. In
the past, it was believed that only a single opioid binding site
existed. The existence of at least three distinct subtypes of
opioid receptors, designated .mu., .delta. and .kappa. receptors,
in the central nervous system and periphery is now well
established. Human .mu., .delta. and .kappa. receptors have been
cloned and have been shown to belong to the G protein-coupled
receptor (GPCR) superfamily.
[0004] The existence of three distinct opioid receptor types, .mu.,
.delta. and .kappa., is confirmed by the recent cloning of these
three opioid receptors from mouse, rat and human cDNAs. All three
of the opioid receptor types are located in human brain or spinal
cord tissues and each has a role in the mediation of pain. Opiates
are used extensively for the treatment of pain and are the most
effective analgesic agents available. Morphine and its analogues
currently prescribed as potent analgesics are .mu. selective
ligands. The general administration of these medications is limited
by side-effects such as respiratory depression, depression of
gastrointestinal motility and development of tolerance and physical
dependence.
[0005] The development of potent and selective antagonist and
agonist ligands for each of these opioid receptor subtypes has been
the goal of medicinal chemists for many years because of their
potential usefulness as pharmacological tools and as therapeutic
agents. Among the .mu., .delta. and .kappa. receptors, the
development of antagonist and agonist ligands acting through the
.delta. receptor has become the focus of research in recent years
due to the therapeutic potential of opioid .delta. ligands. Various
studies suggest that .delta. selective agonists could be
potentially useful as analgesics devoid of side effects such as
respiratory depression and physical dependence side effects.
Selective antagonists of .delta. receptors have been shown to
display immunomodulatory effects as well as modulatory effects on
the actions of drugs of abuse such as cocaine and methamphetamines.
Moreover, recent studies using rodents have demonstrated that
.delta. opioid antagonists are capable of preventing the
development of tolerance and dependence to .mu. agonist such as
morphine without interfering with the .mu. opioid
antinociception.
[0006] It has been found that a number of ligands synthetically
derived from naltrexone display significant selectivity toward the
.delta. receptors. Among these, the indolomorphinan naltrindole is
presently widely used as .delta. selective antagonist ligand, and
other ligands such as its 5'-isothiocyanate derivative, benzofuran
analog, and (E)-7-benzylidenenaltrexone have been useful in the
pharmacological characterization of .delta. opioid receptor
subtypes.
[0007] Continuing efforts exist for developing subtype selective
nonpeptide opioid ligands.
SUMMARY OF INVENTION
[0008] The present invention relates to compounds represented by
the following formula: 2
[0009] wherein each of Y, X and R is individually selected from the
group consisting of hydrogen, hydroxy, alkyl, alkoxy, aryl, halo,
CF.sub.3 and NO.sub.2 provided that at least one of Y, X and R is
other than hydrogen; and pharmaceutically acceptable salts
thereof.
[0010] The present invention also relates to treating a patient
suffering from pain which comprises administering to the patient a
pain treating effective amount of at least one of the above
compounds.
[0011] A further aspect of the present invention relates to
treating a patient in need of an immunomodulatory agent which
comprises administering to the patient an immunomodulatory
effective amount of at least one of the above compounds.
[0012] A still further aspect of the present invention relates to
treating a patient suffering from drug abuse which comprises
administering an effective amount for treating drug abuse of at
least one of the above compounds.
[0013] Still other objects and advantages of the present invention
will become readily apparent by those skilled in the art from the
following detailed description, wherein it is shown and described
preferred embodiments of the invention, simply by way of
illustration of the best mode contemplated of carrying out the
invention. As will be realized the invention is capable of other
and different embodiments, and its several details are capable of
modifications in various obvious respects, without departing from
the invention. Accordingly, the description is to be regarded as
illustrative in nature and not as restrictive.
SUMMARY OF DRAWINGS
[0014] FIG. 1A illustrates antinociceptive dose-response curves for
morphine.
[0015] FIG. 1B illustrates antinociceptive dose-response curves for
compounds of the present invention.
[0016] FIG. 2A illustrates tolerance effects of morphine.
[0017] FIG. 2B illustrates tolerance effects of compounds of the
present invention.
[0018] FIG. 3A illustrates antinociceptive dose-response curves for
morphine.
[0019] FIG. 3B illustrates antinociceptive dose-response curves for
compounds of the present invention.
[0020] FIG. 4 illustrates nociceptive responses for compounds of
the present invention with or without compounds outside the scope
of the present invention.
[0021] FIG. 5 illustrates antinociceptive dose-response curves for
compounds of the present invention in the presence of compounds not
within the scope of the present invention.
[0022] FIG. 6 illustrates opioid withdrawal with compounds of the
present invention compared to compounds not within the scope of the
present invention.
BEST AND VARIOUS MODES FOR CARRYING OUT INVENTION
[0023] The compounds according to the present invention are
represented by the following formula: 3
[0024] wherein each of Y, X and R is individually selected from the
group consisting of hydrogen, hydroxy, alkyl, alkoxy, aryl, halo,
CF.sub.3 and NO.sub.2, provided that at least one of Y, X and R is
other than hydrogen; and pharmaceutically acceptable salts
thereof.
[0025] The alkyl groups typically contain 1 to about 6 carbon
atoms, and more typically 1 to about 3 carbon atoms, and can be
straight, branched-chain or cyclic saturated aliphatic hydrocarbon
groups.
[0026] Examples of suitable alkyl groups include methyl, ethyl and
propyl. Examples of branched alkyl groups include isopropyl and
t-butyl. Examples of suitable cyclic aliphatic groups typically
contain 3-6 carbon atoms and include cyclopentyl and cyclohexyl.
Suitable alkoxy groups contain 1-6 carbon atoms and include
methoxy, ethoxy, propoxy and butoxy. Examples of aryl groups are
phenyl and naphthyl. Examples of halo groups are F, Cl, Br and
I.
[0027] Pharmaceutically acceptable salts of the compounds of the
present invention include those derived from pharmaceutically
acceptable, inorganic and organic acids and bases. Examples of
suitable acids include hydrochloric, hydrobromic, sulfuric, nitric,
perchloric, fumaric, maleic, phosphoric, glycollic, lactic,
salicyclic, succinic, toluene-p-sulfonic, tartaric, acetic, citric,
methanesulfonic, formic, benzoic, malonic, naphthalene-2-sulfonic,
trifluoroacetic and benzenesulfonic acids. Salts derived from
appropriate bases include alkali such as sodium and ammonium.
[0028] Some specific compounds according to the present invention
are represented by the following combinations of R, X and Y
groups:
1 R X Y F H H Br H H I H H CH.sub.3 H H CH.sub.3O H H CF.sub.3 H H
NO.sub.2 H H OH H H C.sub.6H.sub.5 H H H Cl H H H Cl Cl Cl H Cl H
Cl Cl H H Cl Cl Cl
[0029] The preferred compound according to the present invention is
represented by R being Cl, X being H and Y being H and referred to
a
5'-(4-chlorophenyl)-17-(cyclopropylmethyl)-6,7-didehydro-3,14-dihydroxy-4-
,5 .alpha.-epoxypyrido [2', 3':6,7] morphinon (also referred to
herein as compound "6d").
[0030] Compounds of the present invention can be synthesized from
naltrexone by condensation with, for instance, a substituted phenyl
malondialdehyde and ammonium acetate in refluxing acetic acid. By
way of example, a preferred compound of the present invention can
be produced by the following scheme: 4
[0031] The following non-limiting examples are presented to further
illustrate the present invention.
EXAMPLE 1
Preparation of
5'-(4-Chlorophenyl)-17-(Cyclopropylmethyl)-6,7-didehydro-3,-
14-dihydroxy-4,5.alpha.-epoxypyridol[2'3':6,7]morphinan (6d)
[0032] A stirred mixture of naltrexone hydrochloride (4.72 g, 12.5
mmol), 2-(4-chlorophenyl)malondialdehyde (2.5 g, 13.7 mmol), and
ammonium acetate (1.93 g, 25 mmol) in AcOH (75 mL) was heated to
reflux in an oil bath at 130-135.degree. C. under an argon
atmosphere until TLC analysis of the reaction mixture using
EtOAc:cyclohexane:Et.sub.3N (1:1:0.02) as the solvent system
indicated complete disappearance of naltrexone (approximately 20
h). The reaction mixture was cooled to room temperature, and the
solvent was removed under reduced pressure. The residue was treated
with water, and the pH of the mixture was adjusted to 8 with
saturated aqueous NaHCO.sub.3. The solid that separated was
collected by filtration and dried. The crude product was
chromatographed over a column of silica, using CHCl.sub.3-MeOH
(98:2) as the eluent, and then recrystallized from
EtOAc/cyclohexane to give 6d (2.12 g, 35%): mp>175.degree. C.
dec; TLC R.sub.f 0.45 (CHCl.sub.3--MeOH, 97:3); .sup.1H NMR
(CDCl.sub.3) .delta. 0.15-0.19 and 0.56-0.61 (2m, 4H, cyclopropyl
CH.sub.2CH.sub.2), 0.83-0.93 (m, 1H, cyclopropyl CH), 1.81-1.88 (m,
1H, C-15 H), 2.33-2.53 (m, 4H, C-15 H, C-16 H and
NCH.sub.2-cyclopropyl), 2.61-2.84 (m, 4H, C-8 H.sub.2, C-10 H and
C-16 H), 3.17 (app d, 1H, J=18.6 Hz, C-10 H), 3.31 (app d, 1H,
J=6.3 Hz, C-9 H), 4.5-5.5 (broad hump, 2H, C-3 OH and C-14 OH),
5.59 (s, 1H, C-5H), 6.59 and 6.68 (AB-System, 2H, J=8.1 Hz, C-1 H
and C-2 H), 7.38-7.44 (m, 4H, C-2" H, C-3" H, C-5" and C-6"H), 7.48
(d, 1H, J=2.2 Hz, C-4' H) , 8.69 (d, 1H, J-1.9 Hz, C-6' H); MS m/z
487 (MH).sup.+ Anal. (C.sub.29H.sub.27CIN.sub.2O.sub.3), C, H, N,
Cl.
EXAMPLE 2
Opioid Receptor Binding and Bioassays in Smooth Muscle
Preparations
[0033] The binding affinities of compound 6d for the .mu. and
.delta. receptors were determined by inhibition of binding of
[.sup.3H] DAMGO and [.sup.3H] DADLE to rat brain membranes. The
affinity of 6d for the .kappa. receptors was determined by
inhibition of binding of [.sup.3H] U69,593 to guinea pig brain
membranes. The .delta., .mu. and .kappa. opioid receptor binding
affinities along with binding selectivity ratios are given in Table
1. The opioid agonist and antagonist potencies were determined on
the electrically stimulated mouse vas deferens (MVD) and guinea pig
ileum (GPI) smooth muscle preparations. The opioid antagonist and
agonist potencies in the MVD and GPI are listed in Table 2.
2TABLE 1 Opioid Receptor Binding Affinities in Homogenates of Rat
or Guinea Pig Brain Membranes Selectivity K.sub.1 (nM) .+-. SEM
Ratio cmpd .delta..sup.a .mu..sup.b k.sub.1.sup.c .mu./.delta.
k.sub.1/.delta. 6d 2.2 .+-. 0.16 51.0 .+-. 8.0 20.0 .+-. 1.04 23
9.1 naltrexone 39.5 .+-. 3.0 2.5 .+-. 0.21 7.0 .+-. 0.18 0.06 0.18
naltrindole 0.41 .+-. 0.09 99 .+-. 4.6 35.8 .+-. 4.0 241 87
.sup.aDisplacement of [.sup.3H]DADLE (1.3-2.0 nM) in rat brain
membranes using 100 nM DAMGO to block binding to .mu. sites.
.sup.bDisplacement of [.sup.3H]DAMGO (1.4-3.0 nM) in rat brain
membranes. .sup.cDisplacement of [.sup.3H]U69,593 (1.2-2.2 nm) in
guinea pig brain membranes.
[0034]
3TABLE 2 Opioid Antagonist and Agonist Potencies in the MVD and GPI
Preparations antagonist activity agonist activity K.sub.e MVD
IC.sub.50 GPI IC.sub.50 DPDPE (.delta.).sup.a PL-017 (.mu.).sup.b
selectivity (nM) or % (nM) or % compd IC.sub.50 ratio K.sub.e
(nM).sup.c IC.sub.50 ratio K.sub.e (nM).sup.c ratio .mu./.delta.
max resp.sup.d max resp.sup.d 6d 1519 .+-. 797 0.66 .sup.e 21% 163
.+-. 22 nactrindole.sup.f 2000 .+-. 400 0.49 24 .+-. 2 43 88 16% 18
.sup.aDPDPE in the MVD preparation. .sup.bPL-017 in the GPI
preparation. .sup.cK.sub.e (nM) = [antagonist]/(IC.sub.50 ratio -
1), where the IC.sub.50 ratio is the IC.sub.50 of the agonist in
the presence of antagonist divided by the control IC.sub.50 in the
same preparation (n .gtoreq. 3). .sup.dPartial agonist activity is
expressed as the percentage inhibition of contraction at a
concentration of 1 .mu.M. .sup.eThe agonist effects precluded the
determination of antagonist effects. .sup.fData from published
sources.
[0035] The above results show that the chlorophenyl compound 6d
displays relatively potent .delta. antagonist activity with a
K.sub.e of 0.66 nM. Surprisingly, 6d functioned as a full agonist
in the GPI with an IC.sub.50 of 163 nM (0.64.times.morphine). In
the presence of 1 .mu.M CTAP, a .mu. opioid selective antagonist,
the dose-response curve of 6d in the GPI was shifted rightward
5.1-fold. Testing in the presence of nor-BNI, a .kappa. opioid
selective antagonist, shifted the dose-response curve 1.6-fold
rightward. At 1 .mu.M concentration, the nonselective opioid
receptor antagonist naloxone shifted the dose-response curve
5.2-fold to the right. These data show that the agonist activity of
6d in the GPI is mediated through the opioid .mu. receptors.
EXAMPLE 3
Pharmacological Evaluations in Animals
[0036] In the following examples, male ICR mice(20-30 grams) were
used. Solutions of compound 6d and U69,593[(5.alpha., 7 .alpha., 8
.beta.)-(+)-N-methyl-N-(7-(1-pyrrolidinyl)-1-oxaspiro(4,5)dec-8-yl)-benze-
neacetamide] were prepared by initially dissolving compound 6d and
U69,593 in 100 .mu.l of glacial acetic acid and 900 .mu.l of
distilled water. The solution was brought up to approximately pH
5.5 with 1.74 M NaOH and then the final volume adjusted with
distilled water. Vehicle was prepared in a similar fashion without
the drug. Additional compounds used in these studies were dissolved
in distilled water (i.c.v. injections) or physiological saline
(i.p. injections).
[0037] Antinociception was assessed using either the 55.degree. C.
warm-water tail-flick test or the acetic-acid writhing assay. For
the tail-flick test, the latency to the first sign of a rapid
tail-flick was taken as the behavioral endpoint (Jannsen et al.,
The inhibitor effects if fentanyl and other morphine-like
analgesics on the warm water-induced tail-withdrawal reflex in
rats. Arzneimittel-Forschung 13:502-505,1963). Each mouse was first
tested for baseline latency by immersing its tail in the water and
recording the time to response. Mice not responding within 5 sec
were excluded from further testing. Mice were then administered the
test compound and tested for antinociception at 10, 20, 30, 45, 60
and 90 min post-injection. A maximum score was assigned (100%) to
animals not responding within 15 sec to avoid tissue damage.
Antinociception was calculated by the following formula: %
antinociception=100.times.(test latency-control
latency)/(15-control latency). For the acetic acid writhing test,
mice were injected i.p. with 0.9% acetic acid. They were then
placed in a clear Plexiglas observation jar and the number of
abdominal writhes recorded for 15 min (Mogil et al., Heritability
of nociception I: responses of 11 inbred mouse strains on 12
measures of nociception. Pain 80:67-82,1999). Percent
antinociception was calculated using the formula: % MPE (maximum
possible effect)=100-((#writhes individual mouse/mean # writhes
control group).times.100).
[0038] To further determine the in vivo opioid receptor profile of
compound 6d, mice were pretreated with a mu (.beta.-FNA, 19 nmol,
i.c.v., -24 hr), delta (naltrindole, 20 mg/kg, i.p., -20 min) or
kappa (nor-BNI, 1 nmol, i.c.v., -24 hr) selective antagonist.
Control mice received a vehicle injection (5 .mu.l distilled water,
i.c.v., -24 hr). These times and doses have previously been shown
to produce selective blockade of mu, delta and kappa receptors,
respectively (Portoghese et al., Naltrindole, a highly selective
and potent non-peptide delta opioid receptor antagonist. Eur J
Pharmacol 146:185-186,1988; Jiang et al., Naltrindole, a highly
selective and potent non-peptide delta opioid receptor antagonist.
Eur J Pharmacol 146:185-186, 1991; Horan et al., Extremely
long-lasting antagonistic actions of nor-binaltorphimine (nor-BNI)
in the mouse tail-flick test. J Pharmacol Exp Ther 260:1237-1243,
1992). Mice then received an A.sub.90 dose of compound 6d (30 nmol,
i.c.v.) followed 10 min later by an i.p. injection of 0.9% acetic
acid.
[0039] To determine antagonist actions, mice were pretreated with
vehicle or various doses of compound 6d (i.p., -20 min) followed by
injection of i.c.v. A.sub.90 doses of selective mu [D-Ala.sup.2,
NMPhe.sup.4, Gly-ol]enkephalin (DAMGO, 0.1 nmol), delta-1
cyclic[D-Pen.sup.2, D-Pen.sup.5]-enkephalin where Pen is
penicillamine (DPDPE, 30 nmol), delta-2 ([D-Ala.sup.2,
Glu.sup.4]deltorphin (20 nmol), or kappa (U69,593, 60 nmol)
agonists at 0 min. Antinociception was assessed 10 min after
agonist injection, which corresponded to the time of agonist peak
effect (Horan et al., 1992).
[0040] To test for acute physical dependence on morphine, an acute
assay in mice was used (Bisky et al., Effects of neutral and
negative antagonists and protein kinase inhibitors on acute
morphine dependence and antinociceptive tolerance in mice. J
Pharmacol Exp Ther 277: 484-490,1996; Yano et al., Inhibition by
naloxone of tolerance and dependence in mice treated acutely and
chronically with morphine. Res Commun Chem Pathol Pharmacol
16:721-734,1977). Mice were pretreated with morphine (100 mg/kg
s.c.) followed four hours later by an injection of the opioid
antagonist naloxone (10 mg/kg, i.p.), Compopund 6d (10 mg/kg i.p.)
or a combination of both. Mice were immediately placed in a clear
Plexiglas cylinder and observed for 15 minutes. The number of
vertical jumps was recorded during this time.
[0041] Compound 6d was evaluated for antinocieceptive activity in
mice. In the 55.degree. C. tail-flick test (high-intensity
stimulus) compound 6d, administered by intracerebroventricular
(icv) injections, was a partial agonist with an A.sub.50 value
greater than 100 nmol (FIG. 1b). In the acetic acid writhing assay,
6d displayed full agonist activity with a calculated A.sub.50 value
of 7.5 nmol. Morphine, a prototypic p agonist, produced a full
agonist effect following icv injection in both the 55.degree. C.
tail-flick and acetic acid writhing assays (FIG. 1a). The
calculated A.sub.50 values for morphine were 2.94 nmol in the
tail-flick and 0.004 nmol in the acetic acid writhing assays. Using
a standard tolerance regimen, repeated icv injections of an
A.sup.90 dose of morphine (.times.2 daily for 3 days) produced a
significant rightward shift in the antinociceptive dose-response
curve (12.5-fold), indicating the development of tolerance (FIG.
2a). Repeated icv injections of an A.sub.90 dose of 6d on the other
hand did not produce a significant rightward shift (<1.5-fold)
in the antinociceptive dose-response curve (FIG. 2b). This
indicates that compound 6d may produce limited or no
antinociceptive tolerance. The lack of development of tolerance to
the antinociceptive effects of 6d may be related to the mixed .mu.
agonist/.delta. antagonist profile of this compound. The calculated
A.sub.50 values and 95% confidence intervals for each compound and
route of administration are summarized in Table 3 below.
4TABLE 3 Summary of Antinociceptive activity of morphine and
Compound 6d in control mice and mice injected repeatedly (.times.2
daily, 3 days) with A.sub.90 doses of morphine or Compound 6d.
Repeated Drug and Control Injections A.sub.50 Tolerance Route
A.sub.50 (95% C.I.) (95% C.I.) Shift Morphine 0.004 nmol 0.05 nmol
12.5 i.c.v. (0.003-0.006 nmol).sup..dagger. (0.03-0.08
nmol).sup..dagger. 6d 7.5 nmol 10.9 nmol 1.45 i.c.v. (5.3-10.5
nmol).sup..dagger. (7.2-16.5 nmol).sup..dagger. Morphine i.p. 2.2
mg/kg 4.78 mg/kg 2.17 (1.8-2.7 mg/kg) (3.7-6.2 mg/kg) 6d i.p. 4.6
mg/kg 3.85 mg/kg 0.84 (2.5-8.6 mg/kg) (0.9-16.0 mg/kg)
[0042] The calculated A.sub.50 values for morphine in the tail
flick assay by i.c.v. and i.p. routes (and 95% confidence
intervals) were 1.7 nmol (0.8-3.7 nmol) and 8.0 mg/kg (6.3-10.0
mg/kg), respectively. In contrast, Compound 6d produced only
partial agonist effects following i.c.v. administration (40.3% MPE
@ 100 nmol) and had no measurable antinociceptive effect following
i.p. administration at doses up to 60 mg/kg in the tail flick
assay. In the acetic acid writhing test, both compounds produced
full agonist effects following i.c.v. or i.p. administration.
[0043] Repeated administration by i.p. route of approximate
A.sub.90 doses of morphine (6 mg/kg, i.p., .times.2 daily for 3
days) shifted the morphine dose-response curve approximately
2.2-fold (FIG. 3a, Table 3). In contrast, repeated injections by
i.p. route of A.sub.90 doses of Compound 6d (30 mg/kg, i.p.,
.times.2 daily for 3 days) did not significantly shift the Compound
6d dose-response curve (FIG. 3b, Table 3).
[0044] To determine the opioid receptor(s) through which Compound
6d produces its antinociceptive actions, mice were pretreated with
vehicle or a selective mu, delta or kappa antagonist. Mice were
then injected with an A.sub.90 i.c.v. dose of Compound 6d and
antinociception was assessed in the acetic acid writhing assay. An
ANOVA of the data depicted in FIG. 4 yielded an F(4,65)=11.2,
p<0.001. Post-hoc analysis using a Scheff test indicated that
the 30 nmol dose of Compound 6d significantly decreased the number
of writhes (p<0.001). This effect was blocked by pre-treatment
with .beta.-FNA (p<0.002) but not by naltrindole (p>0.99) or
nor-BNI (p>0.13). There was also no difference between the
vehicle control and nor-BNI group (p>0.23).
[0045] The antagonist actions of Compound 6d were assessed by
pre-treating mice i.p. with doses of Compound 6d. Mice were then
injected with A.sub.90 doses of selective mu, delta or kappa
agonists and antinociception was assessed in the 55.degree. C.
tail-flick test. The antagonist dose-response curves are depicted
in FIG. 5 with the corresponding ID.sub.50 values and 95%
confidence limits displayed in Table 4 below. Compound 6d potently
antagonized the actions of the delta-2 selective agonist
[D-Ala.sup.2, Glu.sup.4]deltorphin. The compound was much less
potent at antagonizing the actions of the delta-1 agonist DPDPE or
the mu agonist DAMGO. In addition, doses of up to 60 mg/kg of
Compound 6d did not affect the antinociception actions of the kappa
agonist U69,593.
5TABLE 4 Summary of i.p. Compound 6d ID.sub.50 values against the
antinociceptive actions of A.sub.90 doses of selective opioid
agonists Compound 6d ID.sub.50 95% Confidence Limits Agonist
(mg/kg) (mg/kg) [D-Ala.sup.2, Glu.sup.4]deltorphin 3.4 2.0-5.8
DPDPE 15.3 8.9-26.4 DAMGO 28.9 20.1-41.5 U69,593 >60 N.D.
[0046] The ability of Compound 6d to elicit a withdrawal syndrome
in morphine (100 mg/kg, i.p., -4 hr) pretreated mice and to
attenuate a naloxone precipitated withdrawal (FIG. 6) was
determnined. An ANOVA yielded an F(2,56)=11.9, p<0.0001.
Post-hoc analysis (Scheff test) indicated that an i.p. injection of
Compound 6d (10 mg/kg) precipitated significantly less vertical
jumps than naloxone injection (10 mg/kg, i.p.) (p<0.001).
Coadministration of Compound 6d and naloxone also produced
significantly less jumps than naloxone alone (p<0.05).
[0047] The above tests demonstrate that compound 6d possesses high
binding potency at the .delta. receptor, high .delta. antagonist
potency in bioassays in the MVD, and moderate .mu. agonist potency
in the GPI. In the antinociceptive studies, 6d displayed partial
agonist activity in the tail-flick assay and a full agonist
activity in the acetic acid writhing assay. This compound,
possessing mixed .mu. agonist/.delta. antagonist properties, did
not induce tolerance to its antinociceptive effects and did not
display any overt signs of toxicity in mice in the dose ranges
tested.
[0048] Moreover, Compound 6d attenuated opioud withdrawal in mice
made acutely dependent on morphine.
[0049] The pharmaceutically acceptable effective dosage of the
active compound of the present invention to be administered is
dependent on the species of the warm-blooded animal (mammal), the
body weight, age and individual condition, and on the form of
administration.
[0050] The pharmaceutical composition may be oral, parenteral,
suppository or other form which delivers the compounds used in the
present invention into the bloodstream of a mammal to be treated.
The preferred method of administration is by i.p. (intraperitoneal)
administration since the most effective results were achieved by
this route.
[0051] The compounds of the present invention can be administered
by any conventional means available for use in conjunction with
pharmaceuticals, either as individual therapeutic agents or in a
combination of therapeutic agents. They can be administered alone,
but generally administered with a pharmaceutical carrier selected
on the basis of the chosen route of administration and standard
pharmaceutical practice.
[0052] The dosage administered will, of course, vary depending upon
known factors, such as the pharmacodynamic characteristics of the
particular agent and its mode and route of administration; the age,
health and weight of the recipient; the nature and extent of the
symptoms, the kind of concurrent treatment; the frequency of
treatment; and the effect desired. A daily dosage of active
ingredient can be expected to be about 0.001 to 1000 milligram (mg)
per kilogram (kg) of body weight, with the preferred dose being 0.1
to about 30 mg/kg.
[0053] Dosage forms (compositions suitable for administration)
typically contain from about 1 mg to about 100 mg of active
ingredient per unit. In these pharmaceutical compositions, the
active ingredient will ordinarily be present in an amount of about
0.5-95% by weight based on the total weight of the composition.
[0054] The active ingredient can be administered orally in solid
dosage forms, such as capsules, tablets, and powders, or in liquid
dosage forms, such as elixirs, syrups, and suspensions. It can also
be administered parenterally, in sterile liquid dosage forms. The
active ingredient can also be administered intranasally (nose
drops) or by inhalation. Other dosage forms are potentially
possible such as administration transdermally, via a patch
mechanism or ointment.
[0055] Gelatin capsules contain the active ingredient and powdered
carriers, such as lactose, starch, cellulose derivatives, magnesium
stearate, stearic acid, and the like. Similar diluents can be used
to make compressed tablets. Both tablets and capsules can be
manufactured as sustained release products to provide for
continuous release of medication over a period of hours. Compressed
tablets can be sugar-coated or film-coated to mask any unpleasant
taste and protect the tablet from the atmosphere, or enteric coated
for selective disintegration in the gastrointestinal tract.
[0056] Liquid dosage forms for oral administration can contain
coloring and flavoring to increase patient acceptance.
[0057] In general, water, a suitable oil, saline, aqueous dextrose
(glucose), and related sugar solutions and glycols such as
propylene glycol or polyethylene glycols are suitable carriers for
parenteral solutions. Solutions for parenteral administration
preferably contain a water-soluble salt of the active ingredient,
suitable stabilizing agents, and, if necessary, buffer substances.
Antioxidizing agents such as sodium bisulfite, sodium sulfite, or
ascorbic acid, either alone or combined, are suitable stabilizing
agents. Also used are citric acid and its salts and sodium EDTA. In
addition, parenteral solutions can contain preservatives, such as
benzalkonium chloride, methyl- or propylparaben, and
chlorobutanol.
[0058] Suitable pharmaceutical carriers are described in
Remington's Pharmaceutical Sciences, Mack Publishing Company, a
standard reference text in this field.
[0059] Useful pharmaceutical dosage forms for administration of the
compounds according to the present invention can be illustrated as
follows:
Capsules
[0060] A large number of unit capsules are prepared by filling
standard two-piece hard gelatin capsules each with 100 mg of
powdered active ingredient, 150 mg of lactose, 50 mg of cellulose,
and 6 mg of magnesium stearate.
Soft Gelatin Capsules
[0061] A mixture of active ingredient in a digestible oil such as
soybean oil, cottonseed oil, or olive oil is prepared and injected
by means of a positive displacement pump into gelatin to form soft
gelatin capsules containing 100 mg of the active ingredient. The
capsules are washed and dried.
Tablets
[0062] A large number of tablets are prepared by conventional
procedures so that the dosage unit was 100 mg of active ingredient,
0.2 mg of colloidal silicon dioxide, 5 mg of magnesium stearate,
275 mg of microcrystalline cellulose, 11 mg of starch, and 98.8 mg
of lactose. Appropriate coatings may be applied to increase
palatability or delay absorption.
[0063] Various modifications of the invention in addition to those
shown and described herein will be apparent to those skilled in the
art from the foregoing description. Such modifications are also
intended to fall within the scope of the appended claims.
[0064] The foregoing disclosure includes all the information deemed
essential to enable those skilled in the art to practice the
claimed invention. Because the cited applications may provide
further useful information, these cited materials are hereby
incorporated by reference in their entirety.
[0065] The foregoing description of the invention illustrates and
describes the present invention. Additionally, the disclosure shows
and describes only the preferred embodiments of the invention but,
as mentioned above, it is to be understood that the invention is
capable of use in various other combinations, modifications, and
environments and is capable of changes or modifications within the
scope of the inventive concept as expressed herein, commensurate
with the above teachings and/or the skill or knowledge of the
relevant art. The embodiments described hereinabove are further
intended to explain best modes known of practicing the invention
and to enable others skilled in the art to utilize the invention in
such, or other, embodiments and with the various modifications
required by the particular applications or uses of the invention.
Accordingly, the description is not intended to limit the invention
to the form disclosed herein. Also, it is intended that the
appended claims be construed to include alternative
embodiments.
* * * * *