U.S. patent application number 11/742566 was filed with the patent office on 2007-08-30 for compounds and methods for lowering the abuse potential and extending the duration of action of a drug.
This patent application is currently assigned to CONTROLLED CHEMICALS, INC.. Invention is credited to Zhiwei Guo, Jules A. Shafer, Vladislav V. Telyatnikov.
Application Number | 20070203165 11/742566 |
Document ID | / |
Family ID | 33029866 |
Filed Date | 2007-08-30 |
United States Patent
Application |
20070203165 |
Kind Code |
A1 |
Shafer; Jules A. ; et
al. |
August 30, 2007 |
COMPOUNDS AND METHODS FOR LOWERING THE ABUSE POTENTIAL AND
EXTENDING THE DURATION OF ACTION OF A DRUG
Abstract
The abuse potential of a bioavailable drug such as an opiate
analgesic agent is reduced and its duration of action is extended
by converting it to a poorly absorbed ester prodrug or other
prodrug derivative prior to formulation. Unlike many existing
sustained release formulations of active pharmaceutical agents
wherein an active pharmaceutical agent can be released by chewing,
crushing, or otherwise breaking tablets or capsule beads containing
the active pharmaceutical agent, such mechanical processing of
tablets or capsule beads containing a prodrug of this invention
neither releases the active drug nor compromises the controlled
conversion of prodrug to drug. Moreover, tablets and capsule beads
containing prodrugs of this invention or other drugs can be
formulated with a sufficient amount of a thickening agent such as
hydroxypropylmethylcellulose or carboxymethylcellulose to impede
inappropriate intravenous and nasal administration of formulations
that are not indicated for these modes of administration.
Inventors: |
Shafer; Jules A.; (Gwynedd
Valley, PA) ; Telyatnikov; Vladislav V.; (Hatfield,
PA) ; Guo; Zhiwei; (Franklin Park, NJ) |
Correspondence
Address: |
NASTECH PHARMACEUTICAL COMPANY INC
3830 MONTE VILLA PARKWAY
BOTHELL
WA
98021-7266
US
|
Assignee: |
CONTROLLED CHEMICALS, INC.
151 Discovery Drive, Suite 107
Colmar
PA
18915
|
Family ID: |
33029866 |
Appl. No.: |
11/742566 |
Filed: |
April 30, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10800898 |
Mar 15, 2004 |
7230005 |
|
|
11742566 |
Apr 30, 2007 |
|
|
|
60454253 |
Mar 13, 2003 |
|
|
|
Current U.S.
Class: |
514/282 ;
546/44 |
Current CPC
Class: |
A61P 43/00 20180101;
C07D 489/08 20130101; A61K 47/60 20170801; A61P 25/04 20180101;
A61K 47/555 20170801 |
Class at
Publication: |
514/282 ;
546/044 |
International
Class: |
A61K 31/485 20060101
A61K031/485; C07D 489/02 20060101 C07D489/02 |
Claims
1. A prodrug comprising an opiate covalently linked to a
substituent, wherein the prodrug has a lower binding affinity to a
.mu. opoid receptor than a non-linked opiate, and wherein the
opiate is selected from the group consisting of oxymorphone;
morphine; nalbuphine; butorphanol; nalorphine; hydrocodone;
pentazocine; and hydromorphone.
2. The prodrug of claim 1, wherein the substituent is ##STR27##
wherein R.sub.D is the opiate or a pharmaceutically acceptable salt
thereof ##STR28## wherein R.sub.D is the opiate or a
pharmaceutically acceptable salt thereof.
3. The prodrug of claim 1, wherein the substituent is ##STR29##
wherein R.sub.D is the opiate or a pharmaceutically acceptable salt
thereof.
4. The prodrug of claim 1, wherein the substituent is ##STR30##
wherein R.sub.D is the opiate or a pharmaceutically acceptable salt
thereof.
5. The prodrug of claim 1, wherein the substituent is ##STR31##
wherein R.sub.D is the opiate or a pharmaceutically acceptable salt
thereof, wherein R1 is selected from the group consisting of: a.
hydrogen; b. C.sub.1-4 alkyl unsubstituted or substituted with
CH.sub.3 or C.sub.3-7 cycloalkyl, or amino or guanidino or amidino
or carboxy or acetamido or carbamyl or sulfonate, or phosphate or
phosphonate; c. C.sub.1-4 alkoxy; d. methylenedioxy; e. hydroxy; f.
carboxy; g. sulfonate; h. C.sub.3-7 cycloalkyl; i. aryl,
unsubstituted or substituted with guanidino, amidino, carboxy,
acetamido, carbamyl, sulfonate, phosphate, or phosphonate; and j.
benzyl, unsubstituted or substituted with guanidino, amidino,
carboxy, acetamido, carbamyl, sulfonate, phosphate, or
phosphonate.
6. The prodrug of claim 1, wherein the substituent is ##STR32##
wherein R.sub.D is the opiate or a pharmaceutically acceptable salt
thereof.
7. The prodrug of claim 1, wherein the substituent is ##STR33##
wherein R.sub.D is the opiate or a pharmaceutically acceptable salt
thereof.
8. The prodrug of claim 1, wherein the substituent is ##STR34##
wherein R.sub.D is the opiate or a pharmaceutically acceptable salt
thereof.
9. The prodrug of claim 1, wherein the substituent is ##STR35##
wherein R.sub.D is the opiate or a pharmaceutically acceptable salt
thereof.
10. The prodrug of claim 1, wherein the substituent is ##STR36##
wherein R.sub.D is the opiate or a pharmaceutically acceptable salt
thereof, wherein R.sub.1 is selected from the group consisting of:
a. hydrogen; b. C.sub.1-4 alkyl unsubstituted or substituted with
CH.sub.3 or C.sub.3-7 cycloalkyl, or amino or guanidino or amidino
or carboxy or acetamido or carbamyl or sulfonate, or phosphate or
phosphonate; c. C.sub.1-4 alkoxy; d. methylenedioxy; e. hydroxy; f.
carboxy; g. sulfonate; h. C.sub.3-7 cycloalkyl; i. aryl,
unsubstituted or substituted with guanidino, amidino, carboxy,
acetamido, carbamyl, sulfonate, phosphate, or phosphonate; and j.
benzyl, unsubstituted or substituted with guanidino, amidino,
carboxy, acetamido, carbamyl, sulfonate, phosphate, or
phosphonate.
11. The prodrug of claim 1, wherein the substituent is ##STR37##
wherein R.sub.D is the opiate or a pharmaceutically acceptable salt
thereof, wherein R1 is selected from the group consisting of: a.
hydrogen; b. C.sub.1-4 alkyl unsubstituted or substituted with
CH.sub.3 or C.sub.3-7 cycloalkyl, or amino or guanidino or amidino
or carboxy or acetamido or carbamyl or sulfonate, or phosphate or
phosphonate; c. C.sub.1-4 alkoxy; d. methylenedioxy; e. hydroxy; f.
carboxy; g. sulfonate; h. C.sub.3-7 cycloalkyl; i. aryl,
unsubstituted or substituted with guanidino, amidino, carboxy,
acetamido, carbamyl, sulfonate, phosphate, or phosphonate; and j.
benzyl, unsubstituted or substituted with guanidino, amidino,
carboxy, acetamido, carbamyl, sulfonate, phosphate, or
phosphonate.
12. The prodrug of claim 1, wherein the substituent is ##STR38##
wherein R.sub.D is the opiate or a pharmaceutically acceptable salt
thereof.
Description
[0001] This application is a divisional, which claims the benefit
under 35 U.S.C. .sctn. 120 of U.S. patent application Ser. No.
10/800,898, filed Mar. 15, 2004, which claimed the benefit of U.S.
Provisional Application No. 60/454,253 filed Mar. 13, 2003; each of
which is hereby incorporated by reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] The duration of action of orally administered drugs in
tablets or capsules is often extended by utilizing a controlled
release method of delivery wherein an active pharmaceutical agent
is coated and/or encapsulated and/or otherwise entrapped by a
material that delays dissolution of the active agent. This method
of delivery requires a larger amount of active agent than immediate
release formulations to allow for a longer duration of action.
Intentional or unintentional mechanical processing of such
controlled release tablets or capsule beads could compromise the
controlled release action of such formulations, and thereby may
produce, subsequent to administration, toxic levels of active drug.
Thus, for example, controlled release morphine marketed under the
name Avinza.RTM. and controlled release oxycodone marketed under
the name OxyContin.RTM. contain sufficient opioid to produce
powerful euphoria as well as potentially fatal respiratory
depression when controlled release tablets or capsule beads are
chewed, crushed, ground, or otherwise broken so as to compromise
the controlled release action of the formulation as indicated by
the black box warning on the package insert for OxyContin.RTM. and
Avinza.RTM.).
[0003] Because one can easily achieve a powerful morphine-like high
after oral intravenous or nasal administration of crushed tablets
or capsule beads, the abuse potential of these formulations is
great. Consequently, abuse of OxyContin.RTM. has become a serious
problem as evidenced by medical examiner reports that attribute
several hundred deaths per year to abuse of sustained release
oxycodone, and as evidenced by the substantial fraction of new
enrollees in methadone treatment centers who indicate sustained
release oxycodone as their primary drug of abuse.
[0004] Numerous U.S. Publications (e.g. U.S. Pat. Nos. 6,475,494;
6,451,806; 6,375,957; 6,277,384; 6,228,863; 4,785,000; 4,769,372;
4,661,492; 4,457,933; and 3,966,940) describe the addition of an
opioid antagonist such as naloxone or naltrexone to formulations of
opioid agonists for purposes of lowering their abuse potential.
Typically this approach relies on the use of a form and/or amount
of antagonist that is able to neutralize the opioid agonist when
the contents of crushed tablets are administered parenterally, but
not when unbroken tablets are administered orally as medically
indicated. An oral formulation of the opioid pentazocine marketed
under the name TALWIN.RTM.Nx contains naloxone to impede abusive
intravenous administration. Abusive intravenous administration of
TALWIN Nx, however, may cause harmful withdrawal syndromes in
narcotic dependent individuals. Although Talwin Nx has a lower
potential for abusive parenteral administration than previously
marketed oral pentazocine formulations containing no antagonist, it
still is subject to abusive oral administration. U.S. documents
U.S. Pat. No. 5,149,538 and U.S. Pat. No. 5,236,714 discuss the use
of antagonists to impede abuse of opiod formulations that are
medically indicated for transdermal administration. U.S. documents
U.S. Pat. No. 4,457,933 and U.S. Pat. No. 6,475,494 disclose that
the presence of an appropriate amount of an opioid antagonist in an
agonist formulation medically indicated for oral administration may
also reduce abusive oral administration of that formulation. This
reduction has been attributed (U.S. document U.S. Pat. No.
6,475,494) to an aversive effect of the antagonist in physically
dependent individuals. WO 02094254 describes addition of an
appropriate amount of capsaicin to an oral formulation to deter
abusers from crushing prescription pharmaceutical tablets for
abusive snorting, injection or ingestion.
[0005] Other side effects of opioid analgesics include
gastrointestinal dysfunction caused by the opioids binding to the
.mu. receptors present in the gastrointestinal tract. The
side-effects in the stomach include a reduction in the secretion of
hydrochloric acid, decreased gastric motility, thus prolonging
gastric emptying time, which can result in esophageal reflux.
Passage of the gastric contents through the duodenum may be delayed
by as much as 12 hours, and the absorption of orally administered
drugs is retarded. In the small intestines the opioid analgesics
diminish biliary, pancreatic and intestinal secretions and delay
digestion of food in the small intestine. Resting tone is increased
and periodic spasms are observed. The amplitude of the
nonpropulsive type of rhythmic, segmental contractions is enhanced,
but propulsive contractions are markedly decreased. Water is
absorbed more completely because of the delayed passage of bowel
contents, and intestinal secretion is decreased increasing the
viscosity of the bowel contents. Propulsive peristaltic waves in
the colon are diminished or abolished after administration of
opioids, and tone is increased to the point of spasm. The resulting
delay in the passage of bowel contents causes considerable
desiccation of the feces, which, in turn retards their advance
through the colon. The amplitude of the non-propulsive type of
rhythmic contractions of the colon usually is enhanced. The tone of
the anal sphincter is greatly augmented, and reflex relaxation in
response to rectal distension is reduced. These actions, combined
with inattention to the normal sensory stimuli for defecation
reflex due to the central actions of the drug, contribute to
opioid-induced constipation.
[0006] Although addition of opioid antagonists and other aversive
agents to pharmaceutical tablets or capsules may well prevent
abuse, they may also do harm. Thus, there is a need for the
developments of a new class of opioid analgesics that are abuse
resistant and have lower propensity to agonize the .mu. receptors
in the gastrointestinal tract than the opioid analgesics present in
the prior art.
SUMMARY OF THE INVENTION
[0007] The present invention fills this need by providing for a
method for producing non-naturally occurring prodrugs of analgesic
drugs that bind to .mu. opioid receptors that has a low abuse
potential, an extended duration of action and reduced GI
side-effects. Also claimed are prodrugs of analgesic drugs that
have lower binding affinity to .mu. opioid receptors than the
analgesic drug. The method of this invention involves converting,
prior to formulation, a bioavailable analgesic drug that binds to a
.mu. opioid receptor to a prodrug that limits the accessibility of
the drug to its target tissue. Unlike many existing sustained
release tablet and capsule formulations of active pharmaceutical
agents wherein the active pharmaceutical agent can be released by
chewing, crushing, or otherwise breaking tablets or capsule beads
containing the active pharmaceutical agent, such mechanical
processing of tablet or capsule formulations of prodrugs of this
invention neither releases the agent nor compromises the conversion
of inactive prodrug to active drug.
[0008] The prodrug compositions of this invention limit the
bioavailability of the drug, because the prodrug is poorly absorbed
by the blood after administration by the medically indicated route
of administration or in cases wherein the prodrug is absorbed by
the blood or in cases wherein the prodrug is injected directly into
the blood stream the prodrug is more poorly absorbed by or has a
smaller therapeutic effect on the target tissue than the drug.
[0009] This invention includes but is not limited to ester prodrug
compositions of bioavailable opioid analgesic agents wherein an
alkyl or cyclic alkyl, or phenolic or enolic hydroxyl group of the
drug is covalently linked to an acyl group, and wherein the acyl
group is chosen so as to limit the bioavailability of and rate of
conversion of prodrug to drug so as to produce the desired duration
of action of the drug.
[0010] Also included in this invention is a method involving the
use of a thickening agent such as hydroxypropylmethylcellulose or
carboxymethylcellulose to impede intranasal or intravenous
administration of formulations of the prodrugs of this invention or
other formulations of medications that are not medically indicated
for intranasal or intravenous administration.
DETAILED DESCRIPTION OF THE INVENTION
Definitions
[0011] Receptor Binding Affinity is the binding strength that a
molecule has to a receptor. Affinity is measured by the equilibrium
dissociation constant of the drug-receptor complex (denoted
K.sub.d); the fraction of receptors occupied by the drug is
determined by the concentration of drug and K.sub.d. See Goodman
& Gilman's "The Pharmacological Basis of Therapeutics" 10 ed.,
McGraw-Hill, New York, N.Y., 2001, pp. 39-40.
[0012] .mu. Opioid Receptor is the primary receptor to which the
opioid analgesic drugs bind to produce their analgesic effects. The
opioid analgesic drugs are morphine-related drugs. Examples of
opioid analgesics include morphine, hydromorphone, oxymorphone,
levorphanol, levallorphan codeine, hydrocodone and oxycodone.
Another class of analgesic drugs that bind to the .mu. opioid
receptor is the piperidine and phenylpiperidine class of analgesics
such as meperidine, diphenoxylate, loperamide, fentanyl,
sufentanil, alfentanil, and remifentanil.
[0013] Included in this invention is a method for producing
pharmaceutical agents with both a low abuse potential and an
extended duration of action. The method involves conversion, prior
to formulation, of a bioavailable analgesic drug to a prodrug that
is more poorly absorbed by and/or more poorly activates the target
tissue. This invention includes but is not limited to ester prodrug
compositions of bioavailable opioid analgesic agents wherein an
alkyl or cyclic alkyl or phenolic or enolic hydroxyl group of the
drug is covalently linked to an acyl group that has the following
structure ##STR1## [0014] wherein the values of m and n are
independently selected from the values 0, 1, 2 or 3. [0015] Z and X
are independently selected from ##STR2## [0016] and W is selected
from R.sub.1. ##STR3## [0017] wherein, R.sub.1, R.sub.2, and
R.sub.3 are independently selected from hydrogen. [0018] C.sub.1-4
alkyl unsubstituted or substituted with CH.sub.3 or C.sub.3-7
cycloalkyl, or amino or guanidino or amidino or carboxy or
acetamido or carbamyl or sulfonate, phosphate or phosphonate.
[0019] C.sub.1-4 alkoxy. [0020] methylenedioxy. [0021] hydroxy.
[0022] carboxy. [0023] sulfonate. [0024] C.sub.3-7 cycloalkyl.
[0025] aryl unsubstituted or substituted with guanidino or amidino
or carboxy or acetamido or carbamyl or sulfonate, phosphate or
phosphonate. [0026] benzyl with the benzene ring unsubstituted or
substituted with guanidino or amidino or carboxy or acetamido or
carbamyl or sulfonate, phosphate or phosphonate. [0027] R.sub.1 and
R.sub.2 along with the carbon or carbon atoms to which they are
attached form a C.sub.3-7 cycloalkyl ring ##STR4## [0028] wherein
R.sub.a and R.sub.b are independently selected from hydrogen.
[0029] C.sub.1-4 alkyl unsubstituted or substituted with CH.sub.3
or C.sub.3-7 cycloalkyl. [0030] C.sub.3-7 cycloalkyl. [0031] aryl
unsubstituted or substituted with guanidino or amidino or carboxy
or acetamido or carbamyl or sulfonate, phosphate or phosphonate.
[0032] benzyl with the benzene ring unsubstituted or substituted
with guanidino or amidino or carboxy or acetamido or carbamyl or
sulfonate, phosphate or phosphonate. ##STR5## [0033] wherein
R.sub.e is selected from hydrogen. [0034] C.sub.1-4 alkyl
unsubstituted or substituted with CH.sub.3 or C.sub.3-7 cycloalkyl,
or amino or guanidino or amidino or carboxy or acetamido or
carbamyl or sulfonate, phosphate or phosphonate. [0035] aryl
unsubstituted or substituted with guanidino or amidino or carboxy
or acetamido or carbamyl or sulfonate, phosphate or phosphonate.
[0036] benzyl with the benzene ring unsubstituted or substituted
with guanidino or amidino or carboxy or acetamido or carbamyl or
sulfonate, phosphate or phosphonate. [0037] cellulose or a
cellulose derivative such as methyl cellulose,
hydroxyethylcellulose or hydroxypropylcellulose such that one or
more hydroxyl groups in the cellulose or cellulose derivative forms
an ester or urethane linkage in the prodrug. [0038] poly(ethylene
glycol) or a poly(ethylene glycol) derivative such as poly(ethylene
glycol) methyl ether, poly(ethylene glycol) ethyl ether,
poly(ethylene glycol) carboxymethyl ether, poly(ethylene glycol)
monolaurate such that one or more of the hydroxyl groups of the
poly(ethylene glycol) or the poly(ethylene glycol) derivative form
an ester or urethane linkage in the prodrug. [0039] wherein R.sub.d
is selected from [0040] a polycarboxylic acid such as
carboxymethylcellulose or a derivative thereof, polyacrylic acid or
a derivative thereof, polymethacrylic acid or a derivative thereof
such that one or more of the carboxyl groups of the macromolecule
forms an amide linkage in the prodrug. [0041] poly(ethylene glycol)
bis(carboxymethyl)ether, or poly(ethylene glycol) carboxymethyl,
methyl ether or similar carboxylic acid containing poly(ethylene
glycol) derivative such that one or more carboxyl groups of the
poly(ethylene glycol) derivative forms an amide linkage in the
prodrug. [0042] wherein R.sub.e, R.sub.f and R.sub.g are
independently selected from hydrogen. ##STR6## [0043] wherein the
values of p, and q are independently selected from the values 0, 1,
2, or 3 wherein R.sub.h, R.sub.i, R.sub.k and R.sub.l are
independently selected from hydrogen. [0044] C.sub.1-4 alkyl
unsubstituted or substituted with CH.sub.3 or C.sub.3-7 cycloalkyl,
or amino or guanidino or amidino or carboxy or acetamido or
carbamyl or sulfonate, phosphate or phosphonate. [0045] aryl
unsubstituted or substituted with a guanidino or amidino or carboxy
or acetamido or carbamyl or sulfonate, phosphate or phosphonate.
[0046] benzyl with the benzene ring unsubstituted or substituted
with a guanidino or amidino or carboxy or acetamido or carbamyl or
sulfonate, phosphate or phosphonate R.sub.h and R.sub.l along with
the carbon to which they are attached form a C.sub.3-7 alkyl ring.
[0047] R.sub.k and R.sub.l along with the carbon to which they are
attached form a C.sub.3-7 alkyl ring, [0048] wherein R.sub.j is
selected from [0049] hydrogen. [0050] C.sub.1-4 alkyl unsubstituted
or substituted with CH.sub.3 or C.sub.3-7 cycloalkyl. [0051]
C.sub.3-7 cycloalkyl. [0052] Aryl unsubstituted or substituted with
a carboxyl or guanidino or amidino or carboxy or acetamido or
carbamyl or sulfonate, phosphate or phosphonate. [0053] benzyl with
the benzene ring unsubstituted or substituted with a guanidino or
amidino or carboxy or acetamido or carbamyl or sulfonate, phosphate
or phosphonate. [0054] a polycarboxylic acid such as
carboxymethylcellulose or a derivative thereof, polyacrylic acid or
a derivative thereof, polymethacrylic acid or a derivative thereof
such that one or more carboxyl groups in the macromolecule forms an
amide linkage in the prodrug. [0055] poly(ethylene glycol)
bis(carboxymethyl)ether, or poly(ethylene glycol) carboxymethyl,
methyl ether or similar carboxylic acid containing poly(ethylene
glycol) derivative such that one or more carboxyl groups of the
poly(ethylene glycol) derivative forms an amide linkage in the
prodrug. [0056] Y is independently selected from the following:
##STR7## [0057] wherein the values of u and v are independently
selected from the values 0, 1, 2 or 3, and the value of r is a
value between 10 and 1,000. [0058] wherein R4 is independently
selected from: [0059] Ra. [0060] Rb. ##STR8## [0061] R.sub.d.
[0062] The compounds of the invention may have chiral centers and
may occur as epimeric mixtures, diastereomers, and enantiomers. All
such stereoisomers are included in this invention. When any
variable occurs repeatedly in formula I, the definition of that
variable is independent of its definition at every other occurrence
of that variable. Additionally, combinations of variables and
substituents are permissible only when they produce stable
compounds.
[0063] Some of the abbreviations that may appear in this
application are as follows:
[0064] Designation Definition [0065] Boc tert-butyloxycarbonyl
[0066] tBu tert-butyl [0067] Cbz benzyloxycarbonyl [0068] DCM
dichloromethane [0069] DCC N,N'-dicyclohexylcarbodiimide [0070] DCU
N,N'-dicyclohexylurea [0071] DIEA diisopropylethylamine [0072] DMAP
4-(dimethylamino)pyridine [0073] EtOAc ethyl acetate [0074] Glu
glutamic acid [0075] h hour(s) [0076] HOBt 1-hydroxybenzotriazole
[0077] HPLC high performance liquid chromatography [0078] min
minute(s) [0079] NMR nuclear magnetic resonance [0080] rt room
temperature [0081] TEA triethylamine [0082] TFA trifluoroacetic
acid [0083] THF tetrahydrofuran [0084] TLC thin layer
chromatography
[0085] The acyl portion of the prodrug ester is chosen so as to
endow the prodrug with i) a low bioavailability and ii) a rate of
conversion of prodrug to drug that results in a desired oscillation
in the plasma concentration of drug over the dosing interval.
[0086] To restrict entry of the prodrug into the blood and/or entry
of the prodrug into the central nervous system or otherwise
restrict the bioavailability of the prodrug, one chooses a
macromolecular acyl group (Mr greater than about 1000), and/or a
low molecular weight acyl group (Mr less than about 1000) that
contains one or more groups that bear a charge at pH 7, and/or
groups that contain multiple hydrogen bond donors and acceptors
such as amide groups.
[0087] In cases wherein the prodrug is poorly absorbed into the
blood stream after administration, the rate of conversion of
prodrug to drug substantially controls the duration and intensity
of the effect of the drug. In cases wherein the prodrug is directly
injected into the blood or it is absorbed into the blood, but does
not enter or activate the target tissue, the effect of
administration of the prodrug also will be controlled substantially
by the rate of conversion of prodrug to drug.
[0088] We have discovered how to produce ester prodrugs of alkaloid
opioid analgesics with rates of nonenzymatic hydrolysis at pH 7
compatible with a wide range of dosing frequencies. It is
recognized that for some of the prodrugs included in this
invention, enzymes may contribute to the rate of conversion of
prodrug to drug. The contribution of such enzymatically catalyzed
conversions to the overall rate of conversion of prodrug to drug
may be roughly estimated from in vitro assessment of the conversion
of the drug in presence of digestive enzymes and blood plasma.
Comparative pharmacokinetic studies after administration of drug
and prodrug to a patient should yield an accurate estimate of the
time dependent conversion of prodrug to drug in the patient. When
desirable it should be possible for someone skilled in the art to
adjust the rate of nonenzymatic conversion and enzymatically
catalyzed conversion of prodrug to drug by judicious modification
of the structure of the prodrug. Moreover, someone skilled in the
art should be able to formulate combinations of prodrug derivatives
that release the same drug at differents rates so as to produce a
desired oscillation in plasma drug concentration over the dosing
interval.
[0089] The feasibility of forming enol esters of alkaloid opioids
related to dihydromorphinone has been demonstrated by Nagase et al.
and by Hosztafi et al. These investigators, however, studied
neither the hydrolysis of opioid enol esters nor their suitability
as prodrugs.
[0090] Esters of the phenolic hydroxyl group of various opioid
agonists and antagonists have been studied as prodrugs for
increasing the efficiency of transdermal, sublingual and buccal
delivery and masking the bitter taste opioid agonists and
antagonists (see for example, Hansen et al.; Stinchcomb et al.; and
Hussain et al.).
[0091] For enol esters and phenyl esters wherein the alcohol
portion of the ester is a good leaving group the rate of ester
hydrolysis is increased by increasing the acidity of the carboxyl
group of parent carboxylic acid and/or by utilizing an acyl group
that contains an appropriate neighboring nucleophilic catalyst such
as a carboxylate group that is capable of facilitating hydrolysis
via nucleophilic catalysis as exemplified below. In cases wherein
the intrinsic rate of hydrolysis at pH 7 is more rapid than
desired, steric and charge effects can be employed to reduce the
rate of hydrolysis at pH 7 as exemplified below.
[0092] Listed below by way of example and without limitation are
some oxycodone prodrug compositions included in this invention that
have an acyl group with structure I. ##STR9## ##STR10## ##STR11##
The zwitterionic character and/or molecular weight of these
compounds endow them with a low bioavailability, relative to that
of the drug.
[0093] Enol ester prodrugs 1-7 are carboxylic acid derivatives,
wherein the free carboxylate (at pH 7) group facilitates hydrolysis
of the enol ester and endows the enol ester with a rate of
hydrolysis that changes little in the pH range 6-8. This effect
minimizes intra-individual (over time) or inter-individual
variation in the rate of hydrolysis of compounds 1-7 due to
variation of the pH within the intestinal lumen. It is important to
note that the disposition of the carboxylate group is an important
determinant of the rate of hydrolysis of it effect on ester
hydrolysis (see Table 1). TABLE-US-00001 TABLE I Half-Life for the
Nonenzymatic Hydrolysis of Oxycodone Enol Ester Prodrugs at pH 7.0,
37.degree. C.* ##STR12## R-- Half Life* (h) ##STR13## <0.5
##STR14## 11.4 ##STR15## 3.5 ##STR16## 6.5 ##STR17## 2.4 ##STR18##
173 ##STR19## 66 ##STR20## 6.4 ##STR21## 11.3 ##STR22## 6.9
*Half-life was determined from the first order conversion of
prodrug to oxycodone in buffered solution maintained at 37.degree.
C. The amount of prodrug remaining was determined by HPLC wherein
the ester was quantified from measurements of the area under the
prodrug peak in chromatograms wherein the absorbance of the ester
(typically at 280 nm) was monitored using a diode array detector.
Plots of the logarithm of the fraction of prodrug remaining versus
time were linear as expected for a first order # process.
[0094] It is important to note that the hydrolysis of alkyl esters
with higher pK alcohol leaving groups (such as esters 10-12) is not
facilitated by the presence of a neighboring carboxyl group (See
Table II). We observed, however, that esters of the 14-hydroxyl
group in oxycodone are hydrolyzed rapidly at pH 7. For example we
found that the half-life for the hydrolysis of the 14-acetate ester
of oxycodone is .about.20 min at pH 7, 37.degree. C., whereas the
half-life for hydrolysis of the 6-enolacetate is .about.4 days
under these conditions. The high rate of hydrolysis of the
oxycodone 14-acetate may well reflect intramolecular nucleophilic
attack by the neighboring tertiary amino group in oxycodone to form
an acylammonium ion intermediate that is rapidly hydrolyzed at pH
7. TABLE-US-00002 TABLE II Half-Life for the Nonenzymatic
Hydrolysis of Oxycodone 14-Ester Prodrugs at pH 7.0, 37.degree. C.*
R-- ##STR23## ##STR24## ##STR25## ##STR26## Half life (h) 7.0 2.1
1.9 *Half-Life was determined as described in Table I.
[0095] Included in this invention is a method to impede intravenous
and nasal administration of hydrolytically treated prodrug tablets
or capsule beads by formulating the prodrugs with an appropriate
amount of a thickening agent such as hydroxypropylmethylcellulose
or carboxymethylcellulose. Hydrolytic treatment of such ester
prodrug formulations to release the drug produces a high viscosity
glue-like material that would be difficult to administer nasally.
Moreover, this material requires dilution to more than 10 mL to
easily pass through a hypodermic needle suitable for intravenous
administration. Also included in this invention is a method to add
a sufficient amount of a thickening agent such as
hydroxypropylmethylcellulose or carboxymethylcellulose to impede
intravenous and nasal administration of drug and prodrug
formulations that are not indicated for these routes of
administration. Dissolution for intravenous administration of a
drug or prodrug in a formulation containing the thickening agent
produces a highly viscous glue-like material that requires dilution
to more than 10 mL to easily pass through a hypodermic needle
suitable for intravenous administration. The thickening agent also
reduces absorption of drug or prodrug from nasally administered
powdered tablets or capsule beads. This reduction may reflect an
osmotic effect of the thickening agent.
[0096] Ester prodrugs of the invention can be prepared according to
the general procedures outlined below:
General Procedure for the Preparation of Enol Ester Prodrugs
[0097] The free base form of an aldehyde or ketone containing drug
at 0.0.025-0.5 mol/L is dissolved or suspended in an aprotic polar
solvent such as anhydrous THF or DCM under argon and cooled in a
acetone/dry-ice bath. A 1.05 molar excess over drug of potassium
tBu-OH is added, and the reaction mixture stirred for 40 min. A
1.0-1.2 molar excess over drug of the nitrophenyl ester of the
carboxylic acid to be esterified by the enol group of the drug is
added via syringe as a 0.025-2.0 M. solution in THF or DCM. After
1-2 h, or when the reaction is complete as judged by formation of
the enol ester and liberation of nitrophenol, the reaction is
neutralized by the addition of TFA. If the reaction solidifies at
-78.degree. C., it is allowed to warm to rt before addition of the
TFA. In cases involving the formation of hemi-esters of certain
symmetrical dicarboxylic acids, one can use the cyclic dicarboxylic
acid anhydride in place of a nitrophenyl ester.
[0098] The following carbodiimide mediated coupling reactions can
also be used to prepare enol ester prodrugs. The free base form of
an aldehyde or ketone containing drug at a concentration of
0.025-1.0 M in an aprotic polar solvent such as anhydrous
acetonitrile, THF, or DCM is treated with a 3-6-fold molar excess
of a tertiary amine strong base such as TEA or DIEA for 20-30 min
at rt to promote enolate formation. DMAP, DCC, and carboxylic acid
are then added so that the molar ratio DMAP: carboxylic is in the
range of 0.5-1.0, the molar ratio DCC:carboxylic acid is in the
range 0.5-1.5, and the molar ratio of carboxylic acid:drug is in
the range 2-6.
[0099] In cases wherein a low yield is obtained using this
procedure, addition, prior to addition of carboxylic acid, of HOBt
(in a molar amount approximately equivalent to the carboxylic acid)
may increase the yield. Groups in the prodrug that might interfere
with ester formation can be blocked with groups (such as Boc, tBu,
and Cbz) that may be removed after ester formation without
significant decomposition of the ester.
General Procedure for the Preparation of Alcohol Ester and Phenyl
Ester Prodrugs
[0100] The above procedure for preparation of enol esters wherein
the addition of strong base (to promote enolization) is eliminated
may also be used to prepare alcohol and phenyl ester prodrugs.
Additionally, alcohol ester prodrug may be prepared by condensing
cyclic carboxylic acid anhydrides with drugs containing an alkyl or
cycloalkyl hydroxyl group in pyridine as described in Example 2. It
is important to note that i) dicarboxylic acids (such as maleic
acid, phthalic acid and succinic acid) that facilely form cyclic
anhydrides form unstable phenyl and enol esters; ii) esters of the
14-hydroxyl group of drugs in the 14-hydroxymorphinan family that
contain a tertiary 17-amino group are unstable unless hydroxide ion
catalyzed ester hydrolysis is electrostatically or sterically
impeded; iii) enol ester formation can be eliminated by forming
acid labile ketal and acetal derivatives of drugs that contain
these groups. One skilled in the art can exploit these findings
together with differential chromatographic properties to convert a
drug containing more than one hydroxyl group to a desired mono
ester prodrug.
EXAMPLES
Example 1
Preparation of pentanedioic acid
mono-(3-methoxy-14-hydroxy-6,7-didehydro-4,5.alpha.-epoxy-17-methylmorphi-
nan-6-yl)ester (1-4, also designated compound 2)
Step A: Preparation of Oxycodone Free Base (1-1)
[0101] Oxycodone (Ig) was dissolved in water (5 mL) and mixed with
30 mL of a saturated sodium bicarbonate solution to produce the
free base. The resulting suspension was extracted with three 70 mL
portions of EtOAc. The combined EtOAc extract was washed with 30 mL
of saturated sodium bicarbonate, 30 mL of brine and dried over
magnesium sulfate. EtOAc was removed under reduced pressure from
the resulting solution to yield 785 mg of oxycodone free base.
Step B: Preparation of Pentanedioic Acid Mono-Tert-Butyl Ester
(1-2)
[0102] Potassium tert-butoxide (2.7 g, 24 mmol) was dissolved in 17
mL of anhydrous THF at rt. After 5 min glutaric anhydride (2.4 g,
21 mmol) was added and the resulting suspension stirred for 2 h at
rt. The reaction mixture was then quenched with 20 mL of 1 M
KHSO.sub.4, extracted with 50 mL of EtOAc, adjusted to pH 2-3 with
1 M KHSO.sub.4 and extracted twice with 50 mL EtOAc. The combined
extracts were dried over anhydrous magnesium sulfate, filtered and
concentrated to give a yellow oil which was purified by silica gel
flash chromatography (eluent: EtOAc:Hexanes-1:1) to give 1.65 g
(35% yield) pure (TLC) 1-2.
Step C: Preparation of pentanedioic acid tert-butyl ester
3-methoxy-14-hydroxy-6,7-didehydro-4,5.alpha.-epoxy-17-methylmorphinan-6--
yl ester (1-3)
[0103] A suspension of oxycodone free base (100 mg, 0.317 mmol) in
1.5 mL of anhydrous acetonitrile was stirred for 20 min with DIEA
(0.2 mL 1.15 mmol). DMAP (63 mg, 0.516 mmol) and DCC (112 mg, 0.545
mmol) were then added to the stirred suspension. After 5 min 1-2
(150 mg, 0.8 mmol) was added, the mixture stirred for 16 h at rt,
and the resulting orange suspension concentrated to an oil under
reduced pressure. The concentrated mixture was stirred with 6 mL of
acetone for 10 min, and the precipitated DCU removed by filtration.
The filtrate was concentrated to give a brown oil. HPLC analysis of
the oil indicated that the primary reaction product was 1-3. The
concentrated oil was subjected to reverse phase C-18 silica gel
chromatography using a gradient of 25-40% acetonitrile in 0.07%
aqueous TFA as eluent. Evaporation of the eluent from the fraction
containing 1-3 gave 82 mg (53% yield) of a colorless oil which was
greater than >99% pure 1-3 (HPLC).
Step D: Preparation of pentanedioic acid
mono-(3-methoxy-14-hydroxy-6,7-didehydro-4,5.alpha.-epoxy-17-methylmorphi-
nan-6-yl) ester (1-4)
[0104] 1-3 was treated with 0.5 mL of TFA and after 15 min at rt,
the TFA was removed under reduced pressure to yield>98% pure 1-4
as indicated by HPLC and the .sup.1H and .sup.13C NMR spectra. (As
expected for enol ester 1-4, the .sup.1H NMR spectrum of the
product exhibited a resonance for a vinylic proton at C.sub.7 at
5.53 ppm and the .sup.13C NMR spectrum of the product exhibited no
resonance for a ketonic carbonyl carbon atom in the region of 207
ppm.)
Example 2
Preparation of phthalic acid
mono-(3-methoxy-4,5.alpha.-epoxy-17-methylmorphinan-6-one-14-yl)
ester (2-1, also designated compound 10)
[0105] A solution comprised of oxycodone free base, 1-1, (63 mg,
0.2 mmol), phthalic anhydride (1.185 g, 8.0 mmol) and DMAP (24 mg,
0.2 mmol) in 10 mL of pyridine was stirred in an oil bath at
50-55.degree. C. for 24 h and concentrated under reduced pressure.
The residue was subjected to silica gel flash chromatography with a
5%-20% methanol in dichloromethane gradient. The fraction
containing 2-1 was collected and concentrated under reduced
pressure. HPLC indicated that the fraction was 60% pure. The
concentrated fraction was subjected to another silica gel flash
chromatography using a gradient of 0-20% methanol in
dichloromethane as eluent to yield a fraction containing 32 mg (35%
yield) of 96% pure (HPLC) 2-1, which was further purified by HPLC.
The 1H and .sup.13C NMR spectra verified the structure of 2-1 as a
hydrogen phthalate ester of the 14-hydroxyl group of oxycodone.
(The absence of a 1H resonance in the region of 5.5-6 ppm for a C7
vinylic proton, and the presence of a 13C resonance at 207.5 ppm
for the C6 carbonyl group excluded the presence of an enol ester
linkage in 2-1.)
Example 3
Preparation of 2-(benzyloxycarbonylamino)-pentanedioic acid
1-(3-methoxy-14-hydroxy-6,7-didehydro-4,5.alpha.-epoxy-17-methylmorphinan-
-6-yl) ester (3-2, also designated compound 1)
Step A: Preparation of 2-(benzyloxycarbonylamino)-pentanedioic acid
5-tert-butyl ester
1-(3-methoxy-14-hydroxy-6,7-didehydro-4,5.alpha.-epoxy-17-methylmorphinan-
-6-yl) ester (3-1)
[0106] A solution comprised of oxycodone free base, 1-1, (517 mg,
1.64 mmol), DIEA (1.5 mL, 8.6 mmol) in 9 mL of anhydrous
acetonitrile was stirred at rt for 20 min and mixed with a solution
containing DMAP (400 mg, 3.3 mmol), DCC (1.01 g, 4.1 mmol), and
HOBt (440 mg, 3.3 mmol) in 6 mL of anhydrous acetonitrile.
Cbz-L-Glu(OtBu)-OH (1.1 g, 3.3 mmol) was then added to the combined
solutions. The mixture was stirred for 45 h at rt, precipitated DCU
removed by filtration, and the solution concentrated under reduced
pressure to give a dark-brown oil. HPLC analysis indicated that 39%
of the oxycodone had been converted to 3-1. The brown oil
containing crude 3-1 was dissolved in 20 mL of acetone, cooled in
an ice bath for 2 h, and filtered to remove precipitated DCU. The
filtrate was concentrated to dryness, and subjected to flash
chromatography using a gradient of 0-10% methanol in DCM. The
fractions containing 3-1 were combined and concentrated to dryness.
The residue was treated with 20 mL acetone and filtered to remove
precipitated DCU. The filtrate was concentrated to dryness under
reduced pressure to yield partially purified 3-1.
Step B: Preparation of 2-(benzyloxycarbonylamino)-pentanedioic acid
1-(3-methoxy-14-hydroxy-6,7-didehydro-4,5.alpha.-epoxy-17-methylmorphinan-
-6-yl) ester (3-2)
[0107] The partially purified 3-1 from Step B was treated with 4 mL
TFA in 2 mL DCM at rt for 10 min, dried immediately, and twice
taken up in 10 mL acetonitrile and evaporated to dryness. The
resulting residue was subjected to C-18 silica gel chromatography
using a 20-40% gradient of acetonitrile in 0.07% aqueous TFA as
eluent. Fractions containing pure 3-1 were combined to yield 105 mg
(11% yield) of >99% pure (HPLC) 3-2.
Example 4
Preparation of Fumaric Acid
mono-(3-methoxy-14-hydroxy-6,7-didehydro-4,5.alpha.-epoxy-17-methylmorphi-
nan-6-yl) ester (4-3)
Step A: Preparation of Fumaric Acid Ethyl Ester tert-butyl ester
(4-1)
[0108] To a solution of fumaric acid mono-ethyl ester (721 mg, 5
mmol) and tert-butanol (0.938 mL, 10 mmol) in 10 mL of DCM was
added DMAP (122 mg, 1 mmol) followed by DCC (2.06 g, 10 mmol). The
resulting mixture was stirred at rt for 16 h, taken to dryness
under reduced pressure, stirred overnight with 50 mL acetone and
filtered to remove DCU. The resulting filtrate was concentrated
under reduced pressure, and the residue taken up in EtOAc. The
EtOAc was washed twice with 30 mL 0.1 M KHSO.sub.4, and once with
30 mL saturated NaHCO.sub.3 and once with 30 mL of brine. The
resulting EtOAc solution was treated with charcoal and dried over
magnesium sulfate, concentrated under reduced pressure, and
subjected to silica gel flash chromatography using a gradient of
0-15% EtOAc in hexanes as eluent to give essentially pure (one peak
on HPLC) 4-1 (350 mg, 35% yield).
Step B: Preparation of Fumaric Acid mono-tert-butyl ester (4-2)
[0109] 4-1 (340 mg, 1.7 mmol) was stirred for 1 h at rt with a
solution comprised of 4 mL THF, and 4 mL of a solution containing 1
M NaOH and 1 M LiCl. The resulting mixture was acidified to pH 3-4
with 1 M KHSO.sub.4 and extracted twice with 30 mL of EtOAc. The
extract was washed with 30 mL of brine, dried over magnesium
sulfate, and concentrated under reduced pressure. The resulting
material was subjected to silica gel flash chromatography using a
gradient of 5-10% methanol in DCM to yield 240 mg (82% yield) of
4-2.
Step C: Preparation of fumaric acid
mono-(3-methoxy-14-hydroxy-6,7-didehydro-4,5.alpha.-epoxy-17-methylmorphi-
nan-6-yl) ester (4-3)
[0110] Oxycodone free base, 1-1, (13 mg, 0.04 mmol) in 0.5 mL
acetonitrile was stirred with TEA (0.034 mL 0.24 mmol) for 30 min
at rt. DMAP (15 mg, 0.12 mmol) and DCC (25 mg, 0.12 mmol) were then
added to the solution followed by a solution comprised of 4-2 (41
mg, 0.24 mmol) in 1 mL of acetonitrile. The resulting mixture was
stirred for 16 h and concentrated under reduced pressure. The
resulting residue was stirred with 4 mL of acetone for 30 min, the
precipitated DCU removed by filtration, and the acetone removed
under reduced pressure. The residue was treated with 0.8 mL of TFA
(5 min at rt) to remove the tert-butyl group. The TFA was then
removed under reduced pressure and the resulting residue purified
by HPLC on a C-18 column eluted with 20% acetonitrile in 0.07%
aqueous TFA to yield fraction containing essentially pure 4-3.
Example 5
Preparation of poly(ethylene glycol), Mr 2,000, methyl ether,
carbonylimidodiacetic acid
mono-(3-methoxy-14-hydroxy-6,7-didehydro-4,5.alpha.-epoxy-17-methylmorphi-
nan-6-yl) ester (5-4, also designated compound 5)
Step A: Poly(ethylene glycol), Mr 2,000, methyl ether, nitrophenyl
carbonate (5-1)
[0111] 10 g (5 mmol) of poly(ethylene glycol), Mr 2,000, methyl
ether was boiled with 200 mL of toluene and 100 mL of solvent
distilled off to remove water. The solution was cooled to rt, 10 mL
(61 mmol) of DIEA and 10 g (50 mmol) of nitrophenyl chloroformate
added, and the mixture stirred overnight at 55.degree. C. The
reaction mixture was then concentrated under reduced pressure. The
residue was taken up in DCM, and purified by precipitation from DCM
with ethyl ether to yield 10 g of 5-1 (92%).
Step B: Preparation of poly(ethylene glycol), Mr 2,000, methyl
ether, carbonylimidodiacetic acid (5-2)
[0112] 5-1 was added to a stirred mixture of 0.666 g (5 mmol)
iminodiacetic acid, 1.9 mL (11.5 mmol) DIEA, and 20 mL of DCM.
After 12 h, reverse phase HPLC of an acidified aliquot of the
reaction mixture indicated essentially complete release of
p-nitrophenol and consumption of 5-1. The reaction mixture was
filtered, and the filtrate concentrated under reduced pressure.
Ethyl ether (200 mL) was added to the concentrate to precipitate
the product. 1 N HCl (50 mL) was added to dissolve the solid. After
extraction the aqueous phase with DCM, the DCM was concentrated
under reduced pressure. Addition of ethyl ether to the DCM
concentrate yielded 5-2 (0.446 g, 45%).
Step C: Preparation of poly(ethylene glycol), Mr 2,000, methyl
ether, carbonyliminodiacetic anhydride (5-3)
[0113] DCC (28 mg, 0.25 mmol) was added to 5-2 (430 mg, 0.2 mmol)
in 3 mL DCM. After stirring the solution for 4 h, the DCU was
removed by filtration to yield a DCM solution of 5-3 which was used
in Step D without further purification.
Step D: Preparation of poly(ethylene glycol), Mr 2,000, methyl
ether, carbonyliminodiacetic acid
mono-(3-methoxy-14-hydroxy-6,7-didehydro-4,5.alpha.-epoxy-17-methylmorphi-
nan-6-yl) ester (5-4)
[0114] K-OtBu (28 mg, 0.25 mmol) was added to a stirred suspension
of 1-1 (65 mg, 0.21 mmol) in 2 mL DCM under argon at -78.degree. C.
in an acetone/dry ice bath. After 40 min, the DCM solution of 5-3
from Step C (which was at rt) was added via syringe to the stirred
solution of 1-1 under argon in the acetone/dry ice bath. After one
hour the reaction mixture was brought to rt and neutralized with
TFA. The resulting DCM solution was washed with 0.1% aqueous TFA
and concentrated under reduced pressure. Purified product, 5-4, was
obtained by precipitation of the DCM concentrate with ethyl
ether.
Example 6
Preparation of poly(ethylene glycol), Mr 2,000, methyl ether,
N-carbonylglutamic acid
1-(3-methoxy-14-hydroxy-6,7-didehydro-4,5.alpha.-epoxy-17-methylmorphinan-
-6-yl) ester (6-4, also designated compound 4)
Step A: Preparation of poly(ethylene glycol), Mr 2000, methyl
ether, N-carbonylglutamic acid 5-tert-butyl ester (6-1)
[0115] 5-1 (1 g, 0.46 mmol) was added to a stirred suspension of
1.02 g (5 mmol) 2-aminopentanedioic acid 5-tert-butyl ester in 7.5
mL of 0.333 M NaOH at rt. The solution turned yellow concomitant
with dissolution of 5-1. After 45 min, reverse phase HPLC indicated
essentially complete consumption of 5-1 and liberation
ofp-nitrophenol. The reaction mixture was acidified to pH 1 with 1
N HCl, and extracted with DCM. The DCM was washed with 0.1 N HCl
and concentrated under reduced pressure. Addition of ethyl ether to
the DCM concentrate resulted in precipitation of 450 mg (0.202
mmol, 44%) of the desired product (6-1).
Step B: Preparation of poly(ethylene glycol), Mr 2,000, methyl
ether, N-carbonylglutamic acid 5-tert-butyl ester, 1-p-nitrophenyl
ester (6-2)
[0116] 6-1 (0.45 g, 0.20 mmol) and p-nitrophenol (36 mg, 0.26 mmol)
were dissolved in 1 mL of DCM. The solution was cooled in an ice
water bath; after which time DCC (53 mg. 0.26 mmol) was added.
After 10 minutes of stirring in the ice water bath, the solution
was removed from the ice water bath and stirred overnight at rt.
The resulting reaction mixture was filtered to remove DCU. The DCU
precipitate was washed with 5 mL of DCM, and the DCM solutions were
combined and concentrated under reduced pressure. The product (6-2)
was purified from the DCM concentrate by precipitation with ethyl
ether to yield 168 mg (36%) of 6-2.
Step C: Preparation of poly(ethylene glycol), Mr 2,000, methyl
ether, N-carbonylglutamic acid 5-tert-butyl ester,
1-(3-methoxy-14-hydroxy-6,7-didehydro-4,5.alpha.-epoxy-17-methylmorphinan-
-6-yl) ester (6-3)
[0117] K-OtBu (10 mg, 0.0.086 mmol) was added to a stirred
suspension of 1-1 (23 mg, 0.073 mmol) in 1 mL DCM under argon at
-78.degree. C. in an acetone/dry ice bath. After 40 min, 168 mg
(0.071 mmol) of 6-2 in 1 mL DCM (which was at rt) was added via
syringe to the stirred solution of 1-1 under argon in the
acetone/dry ice bath. After one hour, the reaction mixture was
neutralized with TFA. The resulting DCM solution was washed with
0.1% aqueous TFA and concentrated under reduced pressure. The
product, 6-3, was purified by precipitation of DCM concentrates of
5-4 with ethyl ether.
Step D: Preparation of poly(ethylene glycol), Mr 2,000, methyl
ether, N-carbonylglutamic acid
1-(3-methoxy-14-hydroxy-6,7-didehydro-4,5.alpha.-epoxy-17-methylmorphinan-
-6-yl) ester (6-4)
[0118] 5-4 was dissolved in neat TFA at rt, after 15 min the TFA
was removed under reduced pressure to yield 6-4, which was purified
by dissolution in DCM and precipitation with ethyl ether.
Example 7
Preparation of poly(ethylene glycol), Mr 2,000, methyl ether,
N-carbonylglycine
1-(3-methoxy-14-hydroxy-6,7-didehydro-4,5.alpha.-epoxy-17-methylmorphinan-
-6-yl) ester (7-3)
Step A: Preparation of poly(ethylene glycol), Mr 2,000, methyl
ether, N-carbonylglycine (7-1)
[0119] 5-1 (1 g, 0.46 mmol) was added to a solution of glycine
(0.375 g, 5 mmol) in 5 mL of 0.5 N NaOH. The solution turned yellow
concomitant with dissolution of 1. After 45 min reverse phase HPLC
of an acidified aliquot of the reaction mixture indicated
essentially complete consumption of 5-1 and release of
p-nitrophenol. The reaction mixture was acidified to pH 1 with 1 N
HCl and extracted three times with 5 mL DCM. The combined DCM
extract was washed with water and concentrated under reduced
pressure. Addition of ethyl ether resulted in precipitation of 436
mg (0.207 mmol, 45%) of 7-1.
Step B: Preparation of poly(ethylene glycol), Mr 2,000, methyl
ether, N-carbonylglycine 1-p-nitrophenyl ester (7-2)
[0120] 7-1 (436 mg, 0.21 mmol) andp-nitrophenol (37 mg 0.27 mmol)
were dissolved in 1 mL of DCM. The solution was cooled in an ice
water bath and DCC (55 mg, 0.27 mmol) was added. After 10 minutes
of stirring in the ice water bath, the solution was stirred
overnight at rt. The solution was filtered to remove the DCU and
the DCU precipitate washed with 5 mL of DCM. The DCM solutions
combined, concentrated under reduced pressure and the product
precipitated with ethyl ether to yield 130 mg (28%) of 7-2.
Step C: Preparation of poly(ethylene glycol), Mr 2,000, methyl
ether, N-carbonylglycine
1-(3-methoxy-14-hydroxy-6,7-didehydro-4,5.alpha.-epoxy-17-methylmorphinan-
-6-yl) ester (7-3)
[0121] K-OtBu (28 mg, 0.25 mmol) was added to a stirred suspension
of 1-1 (65 mg, 0.21 mmol) in 2 mL DCM under argon at -78.degree. C.
in an acetone dry ice bath. After 40 min, 130 mg 7-2 in 0.5 mL DCM
(which was at rt) was added via syringe to the stirred solution of
1-1 under argon in the acetone/dry ice bath. After one hour, the
reaction mixture was neutralized with TFA. The resulting DCM
solution was washed with 0.1% aqueous TFA and concentrated under
reduced pressure. The product, 7-3, was purified by precipitation
of DCM concentrates of 7-3 with ethyl ether.
Example 8
Preparation of poly(ethylene glycol), Mr 2,000, methyl ether,
carboxy((3-methoxy-14-hydroxy-6,7-didehydro-4,5.alpha.-epoxy-17-methylmor-
phinan-6-yl) ester) methyl ether (8-3, also designated compound
8)
Step A: Preparation of poly(ethylene glycol), Mr 2,000, methyl
ether, carboxymethyl ether (8-1)
[0122] 50 g of poly(ethylene glycol), Mr 2,000, methyl ether (25
mmol) in 750 mL of toluene was boiled and 200 mL solvent distilled
off to remove water. The solution was cooled to rt and 4.5 g of
KOtBu in 50 mL of t-butanol was added. The resulting mixture was
stirred for 1 h at rt and 16 mL of ethyl bromoacetate added. The
resulting solution was heated to reflux for 0.75 h, stirred at rt
for 18 h, stirred with Celite and filtered. The reaction solvent
was removed under reduced pressure, the residue taken up in 200 mL
DCM and precipitated with 3.3 L of ethyl ether to yield 40 g of the
ethyl ester derivative of 8-1. This material was stirred with 400
mL of 1 N sodium hydroxide for 4 h at rt, cooled in an ice water
bath, acidified to pH 1 with 2 N HCl, and extracted twice with 200
mL of DCM. The DCM extract was concentrated under reduced pressure
to approximately 50 mL, and added to 400 mL of ethyl ether. The
resulting precipate was washed with ethyl ether and dried under
reduced pressure to yield 37 g (72%) of 8-1.
Step B: Preparation of poly(ethylene glycol), Mr 2,000, methyl
ether, carboxy (p-nitophenyl ester) methyl ether (8-2)
[0123] p-Nitrophenol (0.42 g, 3 mmol) was dissolved in a solution
of 8-1 (5 g, 2.5 mmol) in 20 mL of DCM, and cooled in an ice bath.
DCC (0.62 g, 3) was then added with stirring. After 10 min the
solution was removed from the ice water bath and stirred overnight
at room temperature. The reaction mixture was filtered to remove
DCU and the filtrate added to 400 mL of ethyl ether. The resulting
precipate was collected, washed with ethyl ether and dried under
reduced pressure to yield 3.4 g (.about.62%) of 8-1.
Step C: Preparation of poly(ethylene glycol), Mr 2,000, methyl
ether, carboxy
((3-methoxy-14-hydroxy-6,7-didehydro-4,5.alpha.-epoxy-17-methylmo-
rphinan-6-yl) ester) methyl ether 8-3
[0124] K-OtBu (59 mg, 0.52 mmol) was added to a stirred suspension
of 1-1 (141 mg, 0.45 mmol) in 6 mL DCM under argon at -78.degree.
C. in an acetone/dry ice bath. After 40 min, 1 g (0.5 mmol) of 8-1
in 5 mL DCM (which was at rt) was added via syringe to the stirred
solution of 1-1 under argon in the acetone/dry ice bath. The dry
ice bath was removed and the stirred reaction mixture was allowed
to come to rt over a period of 1 h. The reaction mixture was then
neutralized with neat TFA, washed with 0.1% aqueous TFA, and
concentrated under reduced pressure. The product, 8-3, was purified
by precipitation of DCM concentrates of 8-3 with ethyl ether.
Example 9
Binding Affinity of Prodrug of an Analgesic Drug v. the Analgesic
Drug
Receptor Interactions
[0125] Interactions of a prodrug of oxycodone with the .mu., opioid
receptors were assessed wherein receptor affinity was determined
from inhibition of radio labeled ligand binding to membranes from
C6 rat glioma cells expressing recombinant .mu. (rat) opioid
receptor. Opioid-agonist activity was evaluated from the ability of
the test article to stimulate [.sup.35S]-GTP's binding. The data in
the Table reveal that compound 1, a prodrug of oxycodone, has a
substantially lower affinity for the .mu. receptor than does
oxycodone. It is important to note that the affinity of compound 1
for the .mu. receptor may well be lower than that indicated by the
measured K.sub.i, since partial conversion of prodrug to oxycodone
during the assay may have occurred.
Interactions of Compound 1 and Oxycodone with Opioid Receptors
[0126] TABLE-US-00003 Affinity Agonist Activity Receptor Opioid
K.sub.i (.mu.M) EC.sub.50 (.mu.M) .mu. Compound 1 1.21 .+-. 0.18
3.38 .+-. 0.29 .mu. Oxycodone 0.21 .+-. 0.01 0.85 .+-. 0.15
[0127] Conclusions: This shows that the prodrug of oxycodone,
compound 1 has a lower binding affinity for the .mu. opioid
receptor than the analgesic drug oxycodone.
Example 10
Effect of Pancreatic Enzymes and Pepsin on the Rate of Conversion
of Prodrug to Drug
[0128] The half-lives for hydrolysis of prodrug to drug listed in
the following table indicate that pancreatic enzymes do not
markedly effect the liberation of oxycodone from compounds 4 and 5,
whereas the release of oxycodone from compound 8 is markedly
enhanced by pancreatic enzymes.
Effect of Pancreatin (0.5 mg/mL at 37.degree. C., pH 7.4) and
Pepsin (2 mg/mL at 37.degree. C., pH 2) on the Half-Life for
Release of Oxycodone from Prodrugs 4,5 and 8
[0129] TABLE-US-00004 Half-Life for Hydrolysis (h) Compound no
pancreatin plus pancreatin plus pepsin 4 5.5 4.8 105 5 11 8 103 8
6.9 1
[0130] Conclusions: These data indicate that it is possible to
identify prodrugs which either resist or are susceptible to the
action of pancreatic enzymes. By using one or two or more prodrugs
with different half-lives in the digestive tract, it should be
possible for one skilled in the art to obtain a desired oscillation
in oxycodone concentration in the blood over the dosing
interval.
* * * * *