DERIVES D'ACIDE GLYCURONIQUE D'ANTAGONISTES D'OPIOIDES

GLUCURONIC ACID DERIVATIVES OF OPIOID ANTAGONISTS

Abrégé anglais

ABSTRACT
A composition for site-specific delivery of an opioid antagonist
to the intestine of a subject without substantial systemic effects,
comprising nalmefene-3.beta.-D-glucuronide or naltrexone-3.beta.-D-glucuronide in
an amount sufficient to provide opioid antagonism to the intestine of
the subject and a pharmaceutically acceptable carrier for oral admin-
istration, preferably in the form of capsules or tablets.

Revendications

The embodiments of the invention, in which an exclusive property or
privilege is claimed, are defined as follows:
1. A composition for site-specific delivery of an opioid antagonist
to the intestine of a subject without substantial systemic effects,
comprising nalmefene-3.beta.-D-glucuronide or naltrexone-3.beta.-D-glucuronide in
an amount sufficient to provide opioid antagonism to the intestine of
the subject and a pharmaceutically acceptable carrier for oral admin-
istration.
2. Use of an opioid antagonist in the form of a glucuronide deriv-
ative having the formula:
<IMG>
wherein R1 is =0 or =CH2 and R2 is allyl or cyclopropylmethyl, for
providing site-specific opioid antagonism in the intestine of a subject
without substantial systemic effects.
3. The use of claim 2, wherein the glucuronide derivative is
selected from the group consisting of nalmefene-3.beta.-D-glucuronide,
naloxone-3.beta.-D-glucuronide and naltrexone-3.beta.-D-glucuronide.
4. The use of claim 3, wherein the glucuronide derivative is
nalmefene-3.beta.-D-glucuronide.
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5. Use of an opioid antagonist in the form of a glucuronide deriv-
ative, having the formula:
<IMG>
wherein R1 is =0 or =CH2 and R2 is allyl or cyclopropylmethyl, for
treating intestinal dysmotility in a subject suffering from an intes-
tinal dysmotility, without substantial systemic effects, said glucur-
onide derivative being used in an amount sufficient to provide opioid
antagonism in the intestine of the subject, the glucuronide derivative
undergoing cleavage in the intestine of the subject to assume the
aglycone form of the antagonist.
6. The use of claim 5, wherein the glucuronide derivative is
selected from the group consisting of nalmefene-3.beta.-D-glucuronide,
naloxone-3.beta.-D-glucuronide and naltrexone-3.beta.-D-glucuronide.
7. The use of claim 6, wherein the glucuronide derivative is
nalmefene-3.beta.-D-glucuronide.
- 13 -

Description

13~2~
GLUCURONIC ACID DERIVATIVES OF OPIOID ANTAGONISTS
6ACKGROU~ OF THE INVENTION
This invention relates to glucuroni~c acid derivatives of opioid
antagonists, and more particularly to the'therapeutic use of such compounds
in the treatment of localized symptoms with a minimum of systemic ef~ects.
Opioid antagonists are a well-known class of drugs which can be used
to prevent or promptly reverse the effects of morphine-like opioid
agonists. See Goodman and Gilman's The Pharmacological Basis of
.
Therapeutics, Sixth Edition, pp. 521-525. It is known that the opioid
antagonist, naloxone, is converted by the human body to the glucuronide
form, although no use for this form of naloxone has been found before the
present invention. Of particular interest among the known opioid
antagonists is nalmefene, which was first identified and claimed in U.S.
Patent No.-3,814,768 as 6-methylene-6-desoxy-N-cyclopropylmethyl~
hydroxydihydronormorphine.
The constipating effect of opioids is the oldest known effect of these
drugs. Indeed constipation is the most troubling side effect when opioid
drugs are employed to relieve pain. Patients who require opioid analgesics
to relieve pain on a chronic basis e.g. cancer victims, suffer severe
constipation. Such constipation is also common among opioid addicts, and
may even be a problem for those being given opioids on a short term basis,
such as patients undergoing surgery.
Sudden withdrawal of opioid drugs following prolonged exposure
provokes intestinal hypermotility and diarrhea results. This withdrawal
phenomenon of hypermotility and diarrhea is also produced if an opioid
antagonist is given after prolonged opioid administration. Thus the opioid
can cause hypomotility and constipation, and withdrawal can cause the
opposite effect of hypermotility and diarrhea. Hypomotility and
hypermotility are dysmotilities at the extreme ends of the spectrum of
intestinal motility. If an opioid antagonist were administered throughout
the period of opioid exposure, intestinal dysmotility at both ends of the
spectrum could be forestalled.

~3~226S
Attempts have been made to provide opioid antagonists that would
relieve the constipating effect of exogenous opioids without antagonizing
the analgesic effect. This is particularly important for chronic users or
addicts since systemic antagonism can cause severe withdrawal symptoms
mediated by the central nervous system. One class of compounds which has
been investigated for this purpose are the quaternary ammonium derivatives
of known narcotic antagonists (US Patent 4,176,187). The quaternary
antagonists antagonize opioid induced intestinal hypomotility at lower
doses than are required to antagonize opioid induced analgesia. The
selective antagonism, i.e. more effective on intestinal hypomotility than
on central nervous system analgesia, occurs because quaternary compounds
are highly charged. The blood brain barrier impedes passage of highly
charged drugs. Thus, the quaternary ammonium antagonists have more limited
access to the opioid receptors in the central nervous system (CNS) that
mediate analgesia than they do to the opioid receptors in the intestine
that mediate hypomotility.
It is doubtful however that the quaternary ammonium antagonists will
provide a practical solution to the clinical problem of the constipating
effects of opioid analgesics. It has been known since the work of Eddy in
1933 (J. Pharmacol. Exp. Therap., 1967, 157:185-195) that
,''quaternarization" was a means of directing opioids away from the CNS and
toward the intestine. Yet no clinically useful quaternary opioid
antagonist is available to patients. The failure of such a drug to emerge
in therapeutics is likely related to the toxic effects on the autonomic
nervous system that are known to occur with quaternary ammonium drugs.
In addition to relieving the constipating effects of exogenous
opioids, the present invention is also directed to preventing endogenous
opioids from exacerbating intestinal dysmotility of irritable bowel
syndrome. In the last decade it's been discovered that the body produces
its own opioids. The endogenous opioids are called endorphins and
enkephalins. There is an abundance of endogenous opioids and opioid
receptors in the intestinal tract. From the work of Kreek et al. (Lancet
1983 1:262) it appears that such endoyenous opioids contribute to
intestinal dysmotility, Kreek et al. have shown that the opioid antagonist

~ L3~)~2 EiiS
naloxone relieves constipation even though the patients have not been
exposed to an exogenous opioid.
Irritable bowel syndrome is a form of intestinal dysmotility well
known to gastroenterologists. The syndrome is characterized by pain as
well as alternating constipation and dia-rrhea. The endogenous opioids may
exacerbate the syndrome. The hypomotility and constipation phase of the
syndrome could be the result of an excessive endogenous opioid influence,
while the hypermotility and diarrhea could result from an abrupt cessation
of endogenous opioid activity. In irritable bowel syndrome we believe that
there is an exaggerated cyclic effect of the endogenous opioids on the
intestines. During the upphase of the cycle the intestines can be
immobilized and become physically dependent upon the endogenous opioids.
During the down phase of the cycle the intestines can go into withdrawal,
and thus become hypermotile and produce diarrhea. Pain can result from
both constipation and diarrhea.
It appears then that a cycling auto-addiction and withdrawal is an
~important contributor to irritable bowel syndrome. Just as the continued
presence of an opioid antagonist would prevent the addiction or physical
dependence of the intestines to exogenous opioids, an antagonist shauld
similarly prevent the exacerbating influence of cycling endogenous opioids
on the intestine.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an
opioid antagonist which has a local therapeutic effect in the intestinal
tract with a minimum of systemic effects, particularly central nervous
system (CNS) effects.
A further object of this invention is to provide chemical analogs of
known opioid antagonists which have a local intestinal effect with little
or no CNS effects.
A still further object of this invention is to provide a method for
treating intestinal dysmotility by administration of an opioid antagonist
which has a minimum of CNS effects.
In accordance with the above objects of this invention, glucuronic
acid derivatives of opioid antagonists are provided for the treatment of

~3~2~;~
intestinal dysn;otility with a minimum of systemic effects. Nalmefene
glucuronide has been found particularly useful for achieving the objects of
this invention.
DETAILED DESCRIPTION
Th,is invention uses the ~-D-glucuronic acid derivatives of opioid
antagonists for colon specific drug delivery. These compounds are given by
the following general formula:
COH
~ ~0~
O~i o
~--R2
Rl
Wherein R1 is either =O or =CH2, and R2 iS allyl or cyclopropylmethyl.
Three compounds ofi particular interest are nalmefene -3~ -D-glucuronide (~1
is =CH2 and R2 iS cyclopropylmethyl), naloxone -3S -D-glucuronide (R1 is =O
and R2 iS allyl) and naltrexone -3B -D-glucuronide (Rl is =O and R2 iS
cyclopropylmethyl).
In accordance with the present invention, it has been found that these
glucuronide compounds have little or no opioid antagonistic effect unless
they are enzymatically cleaved to yield the free antagonist. For example:
Nalmefene-3B -D-glucuronide + ~-glucuronidase
Nalmefene + glucuronic acid
~ -glucuronidase is a naturally occuring enzyme which is present in the
bacterial flora of the lower intestinal tract, particularly in the colon.
Therefore the compounds of this invention provide a means of specific
delivery of an opioid antagnoist to the lower intestinal tract. Opioid
antagonist activity in the body outside the intestine is avoided because
glucuronic acid derivatives are poorly absorbed and rapidly eliminated in
the urine. Further, the glucuronides do not encounter ~-glucuronidase
outside the intestine.

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~ fter liberation of the aglycone antagonist in the lower intestinal
tract, small amounts o~ this aglycone antagonist could be absorbed into the
portal circulation. However as the aglycone antagonist passes into the
portal blood and through the liver it will be reconverted to its
~-D-glucuronide conjugate by hepatic gtucaronyl transferase. Therefore no
significant amount of active antagonist will reach the systemic
circulation.
An analysis of the blood and urine of rats treated with nalmefene
~orally showed that the concentration of nalmefene glucuronide is about 100
fold higher than is the concentration of free nalmefene. Thus nalmefene is
almost totally biotransformed as a result of "first-pass" metabolism when
administered orally. Such a high degree of biotransformation is common for
this type of drug. However it was discovered that the relative
concentrations of free nalmefene and nalmefene glucuronide in the feces of
these animals were in marked contrast to the blood and urine. Whereas the
ratio of nalmefene to nalmefene glucuronide in the blood and urine was
about 1:100, in the feces the ratio was about 3:1. This suggests that some
of the nalmefene glucuronide formed from nalmefene as a result of
"first-pass" metabolism in the liver, was excreted via the bile into the
intestine and subsequently hydrolysed by intestinal micro flora to yield
free nalmefene.
This observation led to developing opioid antagonist drugs with
activity confined to the intestine. This intestinal specificity would
provide for the following three therapeutic applications:
1) Preventing the unwanted constipation (side effect) caused by opioid
analgesic drugs without interfering with the wanted analgesic effect.
2) Treating idiopathic constipation.
3) Treating irritable bowel syndrome.
SY~THESIS
The compounds according to the present invention can be prepared by
the reaction of opioid antagonists salts (for exanlple lithium salts) with
the appropriate bromosugar followed by alkaline hydrolysis of the
protecting groups. These cornpounds can also be obtained by the Koenigs-

2~i5
Knorr reaction (R.L. Whistler ancl M.L. Wolfrom, "Methods in CarbohydrateChemistry"; R.B. Conrow and S. Bernstein, J. Org. Chem. 1971, (36), 863
and literature cited therein) Followed by alkaline hydrolysis.
Further features and advantages o-F the invention will become more
readily apparent from the following non-limiting examples and the en-
closed drawings, in which:
Fig. 1 is a graph depicting the change in tail skin temperature
in degrees Celsius as a function of time in minutes for various doses of
nalmefene hydrochloride; and
Fig. 2 is a graph depicting the change in tail skin temperature
in degrees Celsius as a function of time in minutes for various doses of
synthetic nalmefene-3-glucuronide.
Examples l and 2 are synthesis of precursor materials and are
described in Bollenback, et al., J. Am. Chem. Soc. 1955, (77), 3310.
Example 1.
40 9 of D-glucurono-6,3-lactone was added to a solution of 0.11 9 of
sodium hydroxide in 300 ml of methanol. The mixture was stirred at room
temperature for 1 hour and the methanol was then removed under vacuum.
The residue was dissolved in 100 ml oF pyridine and 150 ml of acetic
anhydride was added at O C. After 18 hours a-t O C the precipitate was
filtered and recrystallized from ethanol. 38 9 of methyl tetra-O-
acetyl-3-D-glucopyranuronate was obtained, with M.P. 176.5-178 C;[~]2D2=
+ 7.668 (c 1, CHC13).
Example 2.
5 9 of methyl tetra-O-acetyl-~-D-glucopyranuronate was dissolved in 20
ml of 30 %hydrobromic acid in acetic acid and the reaction mixture was
kept overnight at O C. The solvent was then removed under vacuum and
the residue was dissolved in 25 ml of chloroform. This solution was
extracted with cold aqueous sodium bicarbonate and water, dried over
sodium sulfate and the solvent was removed under vacuum. The residual

)226~
syrup was crystallised from ethanol and 4.5 9 of methyl(tri-o-acetyl-a-
D-glucopyranosyl bromide~-uronate was obtained with M.P. 105-7 C, [a]D5=
-~ 196.2 (c 1, CHC13).
Example 3.
To a solution of 2.555 g of nalmefene free base and 0.269 g of lithium
hydroxide monohydrate in 11 ml of methanol was added 2.15 g of methyl
(tri-o-acetyl-a-D-glucopyranosyl bromide)-uronate. After 30 min at room
temperature a solution of 0.430 g of lithium hydroxide in 11 ml of water
`~ '
. ~

13~2~6S
was added. After another 30 min the reaction was brought ~o pH 8 with
acetic acid and the unreacted nalmefene was filtered off. The filtrate was
evaporated and the residual syrup was chromatographed on a silica gel
column with chloroform: methanol = 3:2 as elutant. It was then further
purified on an H+fcrm ion-exchange resi~n~~ith ammonium hydroxide solution
as elutant and 0.78 9 of nalmefene-36-D-glucuronide was obtained.
Elemental analysis C H N
_
Calculated for C27H33N09-2H20 58.79 6.76 2.54
Found 58.76 6.78 2.53
Example 4.
A solution of 0.397 9 of methyl(tri-0-acetyl ~-D-glucopyranosyl
bromide)-uronate in 10 ml of toluene was added dropwise over a period of 1
hour to a mixture of 0.17 g of nalmefene free base and 0.172 9 of cadmium
carbonate in 10 ml of toluene. During the addition, 10 ml of toluene was
also removed from the reaction mixture by distillation. Distillation of
toluene was continued for another 0.5 hour during which time an equal
volume of toluene was added dropwise to the reaction mixture. The
inorganic salts were then removed by filtration and the filtrate was
evaporated. The residue was chromatographed on a silica gel column with
chloroform : methanol = 9:1 as elutant. This gave 0.240 9 of methyl
(nalmefene-tri-0-acetyl~-D-glucopyranosid)-uronate.
Example 5.
To the solution of 0.830 9 of nalmefene free base and 0.087 9 of lithium
hydroxide monhydrate in 4 ml of methanol was added 0.7 g of
methyl(tri-0-acetyl-~-D-glucopyranosyl bromide)-uronate. After 30 min at
room temperature the reaction mixture was brought to pH 8 with acetic acid
and the unreacted nalmefene was filtered off. The filtrate was evaporated
and the residual syrup was chromatographed on a silica gel column with
chloroform : methanol = 9:1 as elutant. 0.`81 9 of methyl(nalmefene-tri-
0-acetyl-~-D-glucopyranosid)-uronate was obtained.
,r.~
~,~

~3~)2~
Example 6.
To a solution of 0.81 9 of methyl(nalmefene-tri-0-acetyl-
~-D-glucopyranosid) uronate in 3.6 ml of methanol was added a solution of
0.12 9 of lithium hydroxide in 3.6 ml of water. After 30 min at room
temperature the reaction mixture was bro-ught to pH 8 with acetic acid and
the solvents were removed under vacuum. The residual syrup was purified as
in example 3 and 0.41 g of nalmefene-3~-D-glucuronide was obtained. This
was identical to the product in example 3.
Example 7.
To a solution of 3.7 9 of naloxone free base and 0.4 9 of lithium hydroxide
in 16 ml of water was added 3.26 9 of methyl(tri-0-acetyl-
3-D-glucopyranosyl bromide)-uronate. After 30 min at room temperature a
solution of 0.65 9 of lithium hydroxide in 16 ml of water was added. After
another 30 min the reaction was brought to pH 8 with acetic acid and the
unreacted naloxone was filtered off. The filtrate was evaporated and the
residual syrup was crystallized from 95k ethanol and 2.27 9 of naloxone-33
-D-glucuronide was obtained.
Elemental analysis C H N
CalCUlated for C25H29NOl02H2o 55.65 6.16 2.6
Found 55.27 5.86 2.54
TEST RESULTS
To determine whether nalmefene glucuronide would alleviate
morphine-induced hypomotility, the charcoal meal assay method of IJitkin et
al. ~J. Pharmacol. Ext. ~herep., 133: 400, 1961) was done on 56 mice. The
results of the assay are given in Table 1 below. These results show that
nalmefene- ~-D-glucuronide was as effective as nalmefene in alleviating the
depressant effects of morphine on intestinal transit.
~'
... . .

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TABLE 1
Summary of the Results of the Charcoal Meal Assaya
~Gastrointestial Motility) in Mice Given Nalmefene HCl
and Nalmefene- ~-D-Glucuronide
Percent Meal
Group Treat_entb ~~raveled + S.E.M. (N) - ~ of Mice
1 Saline ~ Saline 68 + 2 (N=14)
2 Saline + Morphine 28 + 2 (N=8)C
3 Morphine + Saline 31 + 3 (N=8)C'9
4 Saline + Nalmefene Glucuronide 66 + 3 (N=8)d
Morphine + Nalmefene Glucuronide 58 T 12 (N=5)d'e'h'
6 Saline + Nalmefene HCl 63 ~ 2 (N=8)C
7 Morphine + Nalmefene HCl 66 + 14 (N=5) ' '
aWitkin et al., JPET 133: 400, 1961.
bThe first vehicle or drug listed under ~reatment was given 30 minutes
before the second vehicle or drug listed. The results were determined 30
~nin later. All treatments are p.o. and given in a volume of 0.3 ml.
Doses were 10 mg/kg for morphine, 15 mg/kg or 2.9 x 10 6 M/kg for
nalmefene glucuronide and 2.9 x lo 6 M/kg for nalmefene HCl.
CSignificantly different (p~0.05) from Saline + Saline-controls.
dNo significant difference compared with Saline + Saline group.
eSignificantly different (p <0.05) from Morphine + Saline group.
fNo significant difference compared with Saline + Nalmefene group.
9No significant difference compared with Saline + Morphine group.
hNo significant difference compared with Saline ~ Nalmefene Glucuronide.
iNo significant difference compared with Morphine + Nalmefene group.
Group 1 shows that the percentage of the intestinal tract traveled by
the charcoal meal when no drug is given (just vehicle control) is 69 + 2~,'.
,Morphine (groups 2 and 3) reduced the percentage of the intestine traveled
by more than half.
In the absence of morphine neither nalmefene (group 6) nor nalmefene
glucuronide (group 4) had any significant effect. However both nalmefene
(group 7) and nalmefene glucuronide (group 5) protected the intestine
against the depressant effect of morphine. In these latter two groups the
percentage of intestine traveled was not significantly less than in the
group (group 1) where no morphine was present.
Having found that nalmefene-3 ~-D-glucuronide was as effective as
nalmefene in preventing morphine-induced intestinal hypomotility,
experiments were done to determine whether nalmefene-glucuronide lacked
opioid antagonist effect in the central nervous system.
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~30Z26~
The Rapid ~uantitative In Vivo Assay for Narcotic Antagonist of
Katovich et al. (Substance and Alcohol Actions/Misuse, vol 5 87095~ 1984)
was used. This assay is based on the extreme sensitivity of
opioid-dependant animals to narcotic antagonists. Injection of these
animals with a narcotic antagonist produces severe central nervous system
withdrawal signs. One of these signs is an abrupt rise in the skin
temperature of the tail.
Figure 1 shows the marked rise in skin tail temperature in response to
nalmefene in doses as low as 10 ~g/kg. Yet, as Figure 2 shows, an
injection of 1000 ~g/kg of nalmefene glucuronide had no effect.
Additional studies in rats using 14C labelled nalmefene glucuronide
demonstrated that nalmefene glucuronide is not absorbed to any measurable
extent following oral administration of doses as high as 40 mg/kg. No
radioactivity could be detected in plasma 2 hours after dosing while about
85% of the dose was present in the small intestine still as nalmefene
glucuronide. Howevér the 2-3,~ of the dose which had reached the cecum by
-
this time was almost exclusively free nalmefene. Therefore the glucuronide
of an opioid antagonist provides a means of preventing narcotic-induced
intestinal hypomotility without interfering with central nervous system
effects of narcotics, such as analgesia.
The glucuronide derivatives should be administered orally, preferably
in the form of capsules or tablets. Known coating and tabletting agents
can be used. As examples, known enteric coatings like polyacrylates and
cellulose acetate phthalates may be used as coatings for the active
ingredient. The amount of glucuronide derivative administered at one time
is from about 0.1 to 50 mg, preferably 0~5 ~ 20 mg.
The terms and expressions which have been employed are used as terms
of description and not of limitation, and there is no intention in the use
of such terms and expressions of excluding any equivalents of the features
shown and described or portions thereof, but it is recognized that various
modifications are possible within the scope of the invention claimed.