Note: Descriptions are shown in the official language in which they were submitted.
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TITLE OF THE INVENTION
iVIETHODS AND COMPOSITIONS FOR TREATING ERECTILE DYSFUNCTION
FIELD OF THE INVENTION
The present invention provides for novel methods for the treatment of
erectile dysfunction comprising a drug combination. More particularly, the
drug
combination of the present invention comprises an agonist of the melanocortin
receptor with a cyclic-GMP-specific phosphodiesterase inhibitor or an alpha-
adrenergic receptor antagonist. The present invention also provides for
pharmaceutical compositions comprising such drug combinations useful in the
methods to treat erectile dysfunction. Moreover; the present invention
provides for a
method of manufacture of a medicament useful in the treatment of erectile
dysfunction.
I~ BACKGROUND OF THE INVENTION
Erectile dysfunction denotes the medical condition of inability to
achieve penile erection sufficient for successful sexual intercourse. The term
"impotence" is oftentimes employed to describe this prevalent condition.
Approximately 140 million men worldwide, and, according to a National
Institutes of
Health study, about 30 million American men suffer from impotency or erectile
dysfunction. It has been estimated that the latter number could rise to 47
million men
by the year 2000. Erectile dysfunction can arise from either organic or
psychogenic
causes, with about 20% of such,cases being purely psychogenic in origin.
Erectile
dysfunction increases from 40% at age 40, to 67% at age 75, with over 75%
occurring
in men over the age of 50. In pite of the frequent occurrence of this
condition; only a
small number of patients have received treatment because existing treatment
alternatives; such as injection therapies, penile prosthesis implantation, and
vacuum
pumps, have been uniformly disagreeable [for a discussion, see "ABC of sexual
health
erectile dysfunction," Brit. Med. J. 318: 387-390(1999)]. Only more recently
have
moreviable treatment modalities become available; in particular orally active
agents,
such as sildenafil citrate, marketed by Pfizer under the brand name of
Viagra~.
Sildenafil is a selective inhibitor of type V phosphodiesterase (PDE-V), a
cyclic-
GMP-specific phosphodiesterase isozyme [see R.B. Moreland et al., "Sildenafil:
A
Novel Inhibitor of Phosphodiesterase Type 5 in Human Corpus Cavernosum Smooth
Muscle Cells," Life Sci., 62: 309-318 (1998)]. Prior to the introduction of
Viagra~
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on the market, less than 10% of patients suffering from erectile dysfupction
received
treatment. Sildenafil is also being evaluated in the clinic for the treatment
of female
sexual dysfunction.
The regulatory approval of Viagra~ for the oral treatment of erectile
dysfunction has invigorated efforts to discover even more effective methods to
treat
erectile dysfunction. Several additional selective PDE-V inhibitors are in
clinical
trials: UK-114542 is a sildenafil backup from Pfizer with supposedly improved
properties. IC-351 (ICOS Corp.).is claimed to have greater selectivity for PDE-
V
over PDE-VI than sildenafil. Other PDE-V inhibitors include M-54033 and M-
54018
from Mochida Pharmaceutical Co. and E-4010 from Eisai Co., Ltd.
Other pharmacological approaches to the treatment of erectile
dysfunction have been described [see, e.g., "Latest Findings on the Diagnosis
and
Treatment of Erectile Dysfunction," Drug News & Perspectives, 9: 572-~7~
(1996);
"Oral Pharmacotherapy in Erectile Dysfunction," Current Opinion in Urology, 7:
349-
353 (1997)J. A product under clinical development by Zonagen is an oral
formulation
of the alpha-adrenoceptor antagonist phentolamine mesylate under the brand
name of
Vasomax~. Vasomax~ is also being evaluated for the treatment of female sexual
dysfunction
Drugs to treat erectile dysfunction act either peripherally or centrally.
They are also classified according to whether they "initiate" a sexual
response or
"facilitate" a sexual response to prior stimulation [for a discussion, see "A
Therapeutic Taxonomy of Treatments for Erectile Dysfunction: An Evolutionary
Imperative," Int. J. Impotence Res:, 9: 115-121 (1997)]. While sildenafil and
phentolamine act peripherally and are considered to be "enhancers" or
"facilitators" of
the sexual response to erotic stimulation, sildenafil appears to be
efficacious in both
mild organic and psychogenic erectile dysfunction. Sildenafil has an onset of
action
of 30-60 minutes after an oral dose with the effect lasting about 4 hours,
whereas
phentolamine requires 5-30 minutes for onset with a duration of 2 hours.
Although
sildenafil is effective in a majority of patients, it takes a relatively long
time for the
compound to show the desired effects. The faster-acting phentolamine appears
to be
less effective and to have a shorter duration of action than sildenafil. Oral
sildenafil is
effective in about 70% of men who take it, whereas an adequate response with
phentolamine is observed in only35-40% of patients. Both compounds require
erotic
stimulation for efficacy: Since sildenafil indirectly increases blood flow in
the
systemic circulation by enhancing the smooth muscle relaxation effects of
nitric
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oxide, it is contraindicated for patients with unstable heart conditions or
cardiovascular disease, in particular patients taking nitrates, such as
nitroglycerin, to
treat angina. Other adverse effects associated with the clinical use of
sildenafil
include headache, flushing, dyspepsia, and "abnormal vision," the latter the
result of
inhibition of the type VI phosphodiesterase isozyme (PDE-VI), a cyclic-GMP-
specific
phosphodiesterase that is concentrated in the retina. "Abnormal vision" is
defined as
a mild and transient "bluish" tinge to vision, but also an increased
sensitivity to light
or blurred vision. Moreover, since some patients have developed a tolerance to
prior
phosphodiesterase inhibitors, sildenafil may prove to have a similar outcome
in some
percentage of patients when used over a long period of time.
Synthetic melanocortin receptor agonists (melanotropic peptides) have
been found to initiate erections in men with psychogenic erectile dysfunction
[See H.
Wessells et al., "Synthetic Melanotropic Peptide Initiates Erections in Men
With
Psychogenic Erectile Dysfunction: Double-Blind, Placebo Controlled Crossover
1~ Study," J. Urol., 160: 389-393 (1998); Fifteenth American Peptide
Symposium, June
14-19, 1997 (Nashville TN)]. Activation of melanocortin receptors of the brain
appears to cause normal stimulation of sexual arousal. In the above study, the
centrally acting cc-melanocyte-stimulating hormone analog, melanotan-II (MT-
II),
exhibited a 75°Io response rate, similar to results obtained with
apomorphine; when
injected intramuscularly or subcutaneously to males with psychogenic erectile
dysfunction. MT-II is a synthetic cyclic heptapeptide, Ac-Nle-c[Asp-His-DPhe-
Arg-
Trp-Lys]-NH2, which contains the 4-10 melanocortin receptor binding region
common to a-MSH and adrenocorticotropin, but with a lactam bridge. MT-II (also
referred to as PT-14) (Erectide~) is presently in clinical development by
Palatin
Technologies, Inc. and TheraTech, Inc. as a non-penile subcutaneous injection
formulation. An oral transmucosal delivery system for the drug is also being
developed. It is considered to be an "initiator" of the sexual response. The
time to
onset of erection with this drug is relatively short (10-20 minutes) with a
duration of
action approximately 2.5 hours. Adverse reactions observed with MT-II include
nausea, flushing, loss of appetite, stretching, and yawning.
Adverse effects associated with MT-II may be the result of the lack of
selectivity of the compound for a particular melanocortin receptor subtype. To
date,
five melanocortin receptor subtypes have been cloned. Evidence has been
presented
suggesting that the erectogenic properties of melanocortin agonists are
mediated via
binding to the MC-4R subtype. Whereas MC-3R is expressed in the brain, gut;
and
-3-
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placenta, the MC-4R subtype is uniquely expressed in the brain, and
inactivation has
been found to cause obesity.
Because of the unresolved deficiencies of the various pharmacological
agents discussed above, there is a continuing need in the medical arts for
improved
methods and compositions to treat individuals suffering from psychogenic
and/or
organic erectile dysfunction. Such methods should have wider applicability,
enhanced
convenience and ease of compliance, short onset of action, reasonably long
duration
of action, and minimal side effects with few contraindications; as compared to
agents
now available.
It is therefore an object of the present invention to provide methods of
treating erectile dysfunction which comprise the administration to a human
subject in
need thereof a centrally-acting agent that ''initiates" an erectogenic
response in
combination with another centrally-acting agent or a peripherally-acting agent
that
"facilitates" or "enhances" the response to erotic stimulation. The human
subject may
be either male or female.
It is another object of the present invention to provide pharmaceutical
compositions comprising the combination that are useful in the methods of the
present
invention.
It is still a further object of the present invention to provide a method
of manufacture of a medicament useful in the treatment of erectile
dysfunction.
SUMMARY OF THE INVENTION
The present invention provides for methods of treating erectile
dysfunction in a human subject in need of such treatment comprising
administration
of a therapeutically effective amount of an agonist of the melanocortin
receptor in
combination with a therapeutically effective amount of a cyclic-GMP-specific
phosphodiesterase inhibitor or an alpha-adrenergic receptor antagonist.
Further, the
present invention provides for pharmaceutical compositions useful in the
methods of
the present invention, as well as a method of manufacture of a medicament
useful to
treat erectile dysfunction.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is concerned with the combination of an agonist
of the melailocortin receptor with a cyclic-GMP-specific phosphodiesterase
inhibitor
or an alpha-adrenergic receptor antagonist for the treatment of erectile
dysfunction in
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a male or female human subject. This particular combination produces
unexpectedly
superior pharmacokinetic and pharmacodynamic results in the treatment of male
or
female erectile dysfunction. Thus, it is an object of the instant invention to
describe
the combination of the two drugs in the treatment of erectile dysfunction. In
addition;
it is an object of the instant invention to describe preferred embodiments
within each
category of compounds which are used as elements in the instant combination.
It is a
further object of this invention to describe compositions containing each of
the
compounds for use in the treatment of erectile dysfunction. It is a still
further object
of this invention to describe a method of manufacture of a medicament
containing the
present drug combination which is useful for the treatment of erectile
dysfunction
Further objects will become apparent from a reading of the following
description.
The instant combination for the treatment of erectile dysfunction
contains as a first element an agonist of the melanocortin receptor.
Representative
agonists of the melanocortin receptor are disclosed in the following
publications;
which ai-a incorporated by reference herein in their entirety:
( 1) M. E. Hadley et al., "Discovery and Development of Novel Melanogenic
Drugs,"
in Integration of Pharmaceutical Discovery and Development: Case Studies,
edited by
Borchardt et al., Plenum Press, New York, 1998;
(2) R.T. Dorr, et al., "Evaluation of Melanotan-II, A Superpotent Cyclic
Melanotropic
Peptide in a Pilot Phase-I Clinical Study," Life Sci., 58: 1777-1784 (1996);
and
(3) R.A.H. Adan, "Identification of Antagonists for Melanocortin MC3, MC4, and
MC5 Receptors," European J. Pharmacol.; 269: 331-337 (i994).
Compositions and methods for the treatment of psychogenic erectile
dysfunction comprising melanotropic peptides are disclosed in U.S. Patent No.
5;576,290 and CA 2,158,425, which are incorporated by reference herein in
their
entirety.
In the instant combination for the treatment of erectile dysfunction, the
first element of the combination is an agonist of the melanocortin receptor.
In one
embodiment of the combination of the present invention, the agonist of the
melanocortin receptor is melanotan-II (MT-II).
In another embodiment of the combination of the present invention, the
agonist of the melanocortin receptor is selective for the MC-4R subtype.
Selective
MC-4R agonists have been described, and reference is made to the following
disclosures; which are incorporated by reference herein in their entirety:
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(1) C. Haskell-Luevano, et al., "Discovery of Prototype Peptidomimetic
Aaonists at
the Human Melanocortin Receptors MC1R and iV7C4R;" J.Med. Chem., 40: 2133-
2139 (1997); and
(2) H.B. Schioth; et al., "Discovery of Novel Melanocortin-4 Receptor
Selective MSH
Analogues," Brit. J. Pharmacol., 124: 75-82 (1998).
In the instant combination for the treatment of erectile dysfunction, the
second element of the combination is composed of either a cyclic-GMP-specific
phosphodiesterase inhibitor or an alpha-adrenergic receptor antagonist. In a
further
embodiment of the combination of the present invention, the second element of
the
combination is a cyclic-GMP-specific phosphodiesterase inhibitor selec ive for
the
type V phosphodiesterase isozyme (PDE-V). Representative PDE-V inhibitors are
disclosed in the patent and scientific literature. The Pfizer pyrazolo[4,3-
d]pyrimidin-
7-one PDE-V inhibitors are disclosed in WO 94/28902; WO 96/16644; WO
96/16657; EP 0,702,555; EP 0,463,756; CA 2,163,446; and U.S. Patent No.
5,250,534; all of which are incorporated by reference herein in their
entirety.
Sildenafil is the generic name for 1-[4-ethoxy-(6,7-dihydro-1-methyl-7-oxo-3-
propyl-
1H-pyrazolo[4,3-d]pyrimidin-S-yl)phenylsulfonyl]-4-methyl-piperazine. For a
discussion of its efficacy in the treatment of male erectile dysfunction,
reference is
made to I: Goldstein et al.; N. Enal. J. Med., 338: 1397-1404 (1998) and M.
Boolell et
al.; "Sildenafil: an orally active type 5 cyclic GMP-specific
phosphodiesterase
inhibitor for the treatment of penile erectile dysfunction;" Int. J. Impotence
Res., 8:
47-52 ( 1996).
The ICOS Corp. tetracyclic PDE-V inhibitors are disclosed in WO
95/19978; WO 97/03675; and WO 97/19978; all of which are incorporated by
reference herein in their entirety. IC-351 represents (6R, l2aR)-
2,3,6,7,12,12x-
hexahydro-2-methyl-6-(3,4-methylenedioxyphenyl)-pyrazino[2' ,1' : 6,1
]pyrido[3,4-
b]indole-1,4-dione and is disclosed in WO 97/03675 for the treatment of
impotence.
The Mochida Pharmaceutical Co. pyridocarbazole series of PDE-V
inhibitors, of which M-54018 and M-54033 are members, is disclosed in WO
97/45427, which is incorporated by reference herein in its entirety. Other
structural
classes of PDE-V inhibitors are disclosed in WO 98/16224 (E. Merck GmbH); WO
99/02161 (Forssmann), WO 98/07430 (Eisai), and JP 8225541 (Eisai); all of
which
are incorporated by reference herein in their entirety.
In a class of this embodiment of the present invention, the combination
for the treatment of erectile dysfunction comprises an agonist of the
melanocortin
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receptor and a PDE-V inhibitor selected from the group consisting of
sildenafil citrate,
IC-351, M-54018, and NI-54033. In a subclass of this class of the present
invention,
the aQonist of the melanocortin receptor is MT-IL In another subclass of this
class of
the present invention, the combination of the present invention comprises a
selective
agonist of the melanocortin-4 receptor and a PDE-V inhibitor selected from the
group
consisting of sildenafil citrate, IC-351, M-54018, and M-54033. An especially
preferred combination is a selective agonist of the melanocortin-4 receptor
(MC-4R)
and sildenafil citrate.
In another embodiment of the combination of the present invention, the
second element of the combination is an alpha-adrenergic receptor antagonist.
In a
class of this embodiment of the present invention, the alpha-adrenergic
receptor
antagonist is selective for the alpha-2 receptor subtype. In a subclass. of
this class of
the present invention, the alpha-2 receptor antagonist is yohimbine or
delquamine.
The efficacy of yohimbine in the treatment of psychogenic erectile dysfunction
is
reported in Lancet, pp. 42-43 (1987). Delquamine is an alpha adrenoreceptor
antagonist, with -a greater affinity for the alpha-2 receptor subtype [see A.
Morales et
al., "Oral and topical treatment of erectile dysfunction," Urol. Clin. North
Am., 22:
879-885 (1995)].
In another subclass of this class of the present invention, the alpha-2
receptor antagonist is an arylquinolizine derivative disclosed in U.S. Patent
Nos.
4,824,849 and 4,710,504, both of which are incorporated by reference herein in
their
entirety: In a subclass of this subclass of the present invention, the alpha-2
receptor
antagonist is the benzofuroquinolizine analog, MK-912, disclosed in U.S.
Patent No:
4,824;849. MK-912 represents l',3'-dimethylspiro(1,3,4,5',6,6',7,12b-octahydro-
2H-
benzo[b]-furo[2,3-a]quinolizine)-2,4'-pyrimidin-2'-one and is a potent, orally
active
agent with a pharmacologic profile consistent with alpha-2 antagonism [see
D.J.
Pettibone, et al., "Pharmacological profile of a new potent and specific
alpha2-
adrenoceptor antagonist, L-657,743," Naunyn-Schmiederbera's Arch. Pharmacol.,
336: 169-175 (1987)]. The effect of the drug on penile erections in healthy
male
volunteers was observed by B.J. Gertz et al. and reported in Clin. Pharmacol.
Ther.,
46: 566-575 (1989). An especially preferred combination is a selective agonist
of the
melanocortin-4 receptor (MC-4R) and MK-912.
The instant combination of an agonist of the melanocortin receptor and
a cyclic-GMP-specific phosphodiesterase inhibitor or an alpha-adrenergic
receptor
antagonist is useful in the therapeutic treatment of erectile dysfunction:
Although the
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methods and compositions comprising drug combinations of the present invention
are
envisaged primarily for the treatment of male erectile dysfunction, they may
also be
useful for the treatment of female sexual dysfunction, including orgasmic
dysfunction
related to clitoral disturbances.
j The combination of an agonist of the melanocortin receptor and a
cyclic-GMP-specific phosphodiesterase inhibitor or an alpha-adrenergic
receptor
antagonist provides an unexpectedly superior effect in the treatment of
erectile
dysfunction. The combination provides for effective treatment of either
psychogenic
or organic erectile dysfunction in a greater percentage of the affected
population than
either element of the combination separately. The combination provides for a
shorter
onset of action and longer duration of action than either element of the
combination
separately. The combination also has fewer side effects and contraindications
than
either member of the combination separately
For use in medicine, the salts of the compounds of this invention refer
to non-toxic "pharmaceutically acceptable salts." Other salts may, however, be
useful
in the preparation of the compounds according to the invention or of their
pharmaceutically acceptable salts. Salts encompassed within the term
"pharmaceutically acceptable salts" refer to non-toxic salts of the compounds
of this
invention which are generally prepared by reacting the free base with a
suitable
organic or inorganic acid. Representative salts include the following:
Acetate, Benzenesulfonate, Benzoate, Bicarbonate, Bisulfate,
Bitartrate, Borate, Bromide, Camsylate, Carbonate, Chloride, Clavulanate,
Citrate,
Dihydrochloride, Edetate, Edisylate, Estolate, Esylate, Fumarate, Gluceptate,
Gluconate, Glutamate, Glycollylarsanilate, Hexylresorcinate, Hydrabamine;
Hydrobromide, Hydrochloride, Hydroxynaphthoate, Iodide, Isothionate, Lactate,
Lactobionate, Laurate, Malate, Maleate, Mandelate, Mesylate, Methylbromide,
Methylnitrate, Methylsulfate, Mucate, Napsylate, Nitrate; N-methylglucamine
ammonium salt, Oleate, Oxalate, Pamoate (Embonate), Palmitate, Pantothenate;
Phosphate/diphosphate, Polygalacturonate, Salicylate, Stearate, Sulfate,
Subacetate,
Succinate, Tannate, Tartrate, Teoclate, Tosylate, Triethiodide and Valerate.
Furthermore, where the compounds of the invention carry an acidic moiety;
suitable
pharmaceutically acceptable salts thereof may include alkali metal salts,
e.g., sodium
or potassium salts; alkaline earth metal salts, e.g., calcium or magnesium
salts; and
salts formed with suitable organic ligands, e.g., quaternary ammonium salts.
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The compounds of the present invention may have chiral centers and
occur as racemates, racemic mixtures and as individual diastereomers, or
enantiomers
with all isomeric forms being included in the present invention: Therefore,
where a
compound is chiral, the separate enantiomers, substantially free of the other,
are
included within the scope of the invention; further included are all mixtures
of the two
enantiomers. Also included within the scope of the invention are polymorphs
and
hydrates of the compounds of the instant invention.
The present invention includes within its scope prodrugs of the
compounds of this invention. Tn general, such prodrugs will be functional
derivatives
of the compounds of this invention which are readily convertible in vivo into
the
required compound. Thus, in the methods of treatment of the present invention,
the
term "administering" shall encompass the treatment of erectile dysfunction
with the
compound specifically disclosed as an element of the combination or with a
compound which may not be specifically disclosed, but which converts to the
specified compound in vivo after administration to the patient. Conventional
procedures for the selection and preparation of suitable prodrug derivatives
are
described, for example, in "Design of Prodrugs," ed. H. Bundgaard; Elsevier;
1985.
Metabolites of these compounds include active species produced upon
introduction of
compounds of this invention into the biological milieu.
The term "therapeutically effective amount" shall mean that amount of
a drug or pharmaceutical agent that will elicit the biological or medical
response of a
tissue; system, animal or human that is being sought by a researcher or
clinician.
As used herein, the term "composition" is intended to encompass a
product comprising the specified ingredients in the specified amounts, as well
as any
product which results, directly or indirectly, from combination of the
specified
ingredients in the specified amounts.
In the combination of the present invention, the agonist of the
melanocortin receptor may be administered separately or in conjunction with
the
cyclic-GMP-specific phosphodiesterase inhibitor or the alpha-adrenergic
receptor
antagonist. In addition, the administration of one element of the combination
of the
present invention may be prior to, concurrent to, or subsequent to the
administration
of the other element of the combination.
The elements of the combination of the present invention may be
administered by oral, parenteral (e.g., intramuscular, intraperitoneal;
intravenous or
subcutaneous injection, or implant), buccal, nasal, vaginal; rectal,
sublingual, or
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topical (e.g., ocular eyedrop) routes of administration and may be formulated,
alone or
together, in suitable dosage unit formulations containing conventional non-
toxic
pharmaceutically acceptable carriers, adjuvants and vehicles appropriate for
each
route of administration.
The pharmaceutical compositions for the administration of the
compounds of this invention may conveniently be presented in dosage unit form
and
may be prepared by any of the methods well known in the art of pharmacy. All
methods include the step of bringing the active ingredient into association
with the
carrier which constitutes one or more accessory ingredients. In general, the
pharmaceutical compositions are prepared by uniformly and intimately bringing
the
active ingredient into association with a liquid carrier or a finely divided
solid carrier
or both, and then. if necessary, shaping the product into the desired
formulation. In
the pharmaceutical composition the active object compound is included in the
combination in an amount sufficient to produce the desired pharmacologic
effect upon
the process or condition of erectile dysfunction.:
The pharmaceutical compositions containing the active ingredient
suitable for oral administration may be in the form of discrete units such as
hard or
soft capsules, tablets, troches or lozenges, each containing a predetermined
amount of
the active ingredient; in the form of a dispersible powder or granules; in the
form of a
solution or a suspension in an aqueous liquid or non-aqueous liquid; in the
form of
syrups or elixirs; or in the form of an oil-in-water emulsion or a water-in-
oil emulsion.
Compositions intended for oral use may be prepared according to any method
known
to the art for the manufacture of pharmaceutical compositions and such
compositions
may contain one or more agents selected from the group consisting of
sweetening
agents, flavoring agents, coloring agents and preserving agents in order to
provide a
pharmaceutically elegant and palatable preparation.
Solid dosage forms for oral administration include capsules, tablets,
pills, powders and granules. In such solid dosage forms, the active compounds
are
admixed with at least one inert pharmaceutically acceptable carrier such as
sucrose,
lactose, or starch. Such dosage forms can also comprise, as is normal
practice,
additional substances other than inert diluents, e.g., lubricating agents such
as
magnesium stearate. In the case of capsules, tablets and pills, the dosage
forms may
also comprise buffering agents.
Tablets containing the active ingredient in admixture with non-toxic
pharmaceutically acceptable excipients may also be manufactured by known
methods.
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The excipients used may be for example, (1) inert diluents such as calcium
carbonate.
lactose, calcium phosphate or sodium phosphate; (2) granulating and
disintegrating
agents, such as corn starch or alginic acid; (3) binding agents such as
starch, Gelatin or
acacia; and {4) lubricating agents such as magnesium stearate, stearic acid or
talc.
The tablets may be uncoated or they may be coated by known techniques to delay
disintegration and absorption in the gastrointestinal tract and thereby
provide a
sustained action over a longer period. For example, a time delay material such
as
glyceryl monostearate or glyceryl distearate may be employed: They may also be
coated by the techniques described in the U.S. Pat. Nos. 4,256,108; 4,160,452;
and
4,265,874 to form osmotic therapeutic tablets for controlled release.
In some cases, formulations for oral use may be in the form of hard
gelatin capsules wherein the active ingredient is mixed with an inert solid
diluent, for
example calcium carbonate, calcium phosphate or kaolin. They may also be in
the
form of soft gelatin capsules wherein the active ingredient is mixed with
water or an
oil medium, for example peanut oil, liquid paraffin, or olive oil:
Liquid dosage forms for oral administration include pharmaceutically
acceptable emulsions, solutions, suspensions, syrups, and elixirs containing
inert
diluents commonly used in the art, such as water. Besides such inert diluents,
compositions can also include adjuvants, such as wetting agents; emulsifying
and
suspending agents, and sweetening, flavoring, and perfuming agents.
Aqueous suspensions normally contain the active materials in
admixture with excipients suitable for the manufacture of aqueous suspensions.
Such
excipients may be
1) suspending agents such as sodium carboxymethyl-cellulose;
methylcellulose, hydroxypropylmethyl-cellulose; sodium
alginate, polyvinyl-pyrrolidone, gum tragacanth and hum
acacia;
(2) dispersing or wetting agents which maybe
(a) a naturally-occurnng phosphatide such as lecithin;
(b) a condensation product of an alkylene oxide with a fatty
acid, for example, polyoxyethylene stearate,
(c) a condensation product of ethylene oxide with a long
chain aliphatic alcohol, for example,
heptadecaethyleneoxycetanol,
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(d) a condensation product of ethylene oxide with a partial
ester derived from a fatty acid and a hexitol such as
polyoxyethylene sorbitol monooleate, or
(e) a condensation product of ethylene oxide with a partial
ester derived from a fatty acid and a hexitol anhydride,
for example polyoxyethylene sorbitan monooleate.
The aqueous suspensions may also contain one or more preservatives,
for example, ethyl or n-propyl p-hydroxybenzoate; one or more coloring agents;
one
or more flavoring agents; and one or more sweetening agents, such as sucrose
or
saccharin.
Oily suspensions may be formulated by suspending the active
ingredient in a vegetable oil, for example arachis oil, olive oil; sesame oil
or coconut
oil, or in a mineral oil such as liquid paraffin. The oily suspensions may
contain a
thickening agent, for example beeswax, hard paraffin or cetyl alcohol.
Sweetening
agents and flavoring agents may be added to provide a palatable oral
preparation.
These compositions may be prepared by the addition of an antioxidant such as.
ascorbic acid.
Dispersible powders and granules are suitable for the preparation of an
aqueous suspension. They provide the active ingredient in admixture with a
dispersing or wetting agent, a suspending agent and one or more preservatives.
Suitable dispersing or wetting agents and suspending agents are exemplified by
those
already mentioned above. Additional excipients; for example; those sweetening,
flavoring and coloring agents described above may also be present.
The pharmaceutical compositions of the invention may also be in the
form of oil-in-water emulsions. The oily phase may be a vegetable oil such as
olive
oil or arachis oils, or a mineral oil such as liquid paraffin or a mixture
thereof.
Suitable emulsifying agents may be (1) naturally-occurnng gums such as gum
acacia
and gum tragacanth, (2) naturally-occurring phosphatides such as soybean and
lecithin, (3) esters or partial esters derived from fatty acids and hexitol
anhydrides; for
example, sorbitan monooleate, (4) condensation products of said partial esters
with
ethylene oxide, for example polyoxyethylene sorbitan monooleate. The emulsions
may also contain sweetening and flavoring agents.
Syrups and elixirs may be formulated with sweetening agents, for
example, glycerol, propylene glycol, sorbitol or sucrose. Such formulations
may also
contain a demulcent, a preservative and flavoring and coloring agents.
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The pharmaceutical compositions may be in the form of a sterile
injectable aqueous or oleagenous suspension or solution. The suspension may be
formulated according to known methods using those suitable dispersing or
wetting
agents and suspending agents which have been mentioned above. The sterile
injectable preparation may also be a sterile injectable solution or suspension
in a non-
toxic parenterally-acceptable diluent or solvent, for example as a solution in
1,3-
butane- diol. Among the acceptable vehicles and solvents that may be employed
are
water, Ringer's solution and isotonic sodium chloride solution. In addition,
sterile,
fixed oils are conventionally employed as a solvent or suspending medium. For
this
purpose any bland fixed oil may be employed including synthetic mono- or
diglycerides. In addition, fatty acids such as oleic acid find use in the
preparation of
injectables.
Preparations according to this invention for parenteral administration
include sterile aqueous or non-aqueous solutions, suspension, or emulsions.
Examples of non-aqueous solvents or vehicles are propylene glycol,
polyethylene
glycol, vegetable oils, such as olive oil and corn oil, Gelatin, and
injectable organic
esters such as ethyl oleate. Such dosage forms may also contain adjuvants such
as
preserving, wetting, emulsifying, and dispersing agents. They maybe sterilized
by,
for example, filtration through a bacteria-retaining filter, by incorporating
sterilizing
agents into the compositions, by irradiating the compositions, or by heatinj
the
compositions. They can also be manufactured in the form of sterile solid
compositions which can be dissolved in sterile water, or some other sterile
injectable
medium immediately before use. The combination of this invention may also be
administered in the form of suppositories for rectal administration. This
composition
can be prepared by mixing the drug with a suitable non-irritating excipient
which is
solid at ordinary temperatures but liquid at the rectal temperature and will
therefore
melt in the rectum to release the drug. Such materials are cocoa butter and
polyethylene glycols. Compositions for buccal, nasal or sublingual
administration are
also prepared with standard excipients well known in the art.
For topical administration the combination of this invention may be
formulated in liquid or semi-liquid preparations such as liniments, lotions,
applications; oil-in-water or water-in-oil emulsions such as creams;
ointments, jellies
or pastes, including tooth-pastes; or solutions or suspensions such as drops,
and the
like.
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WO 00/53148 PCT/US00/05711
The dosage of the active ingredients in the compositions of this
invention may be varied. However, it is necessary that the amount of the
active
ingredient be such that a suitable dosage form is obtained. The selected
dosage
depends upon the desired therapeutic effect, on the route of administration
and on the
duration of the treatment. Dosage ranges in the combination for the
melanocortin
receptor agonist and cyclic-GMP-specific phosphodiesterase inhibitor or alpha-
adrenergic receptor antagonist are approximately one tenth to one times the
clinically
effective ranges required to induce the desired erectogenic effect,
respectively when
the compounds are used singly. Generally, dosage levels of the, melanocortin
receptor
agonist of between about 0.001 mg per kg of body weight per day (mg/kg/day) to
about 100 mg/kg/day, preferably 0.01 to 10 mg/kg/day, and most preferably 0.1
to 5.0
mg/kg/day. For oral administration, the compositions are preferably provided
in the
form of tablets containing 0.01; 0.05, 0.1, 0.~, 1.0, 2.5, 5.0, 10.0,
15.0,25.0; 50.0,
100, 250 and 500 milligrams of each of the active ingredients for the
symptomatic
adjustment of the dosage to the patient to be treated. A medicament typically
contains
from about 0.01 mg to about 500 mg of each of the active ingredients,
preferably,
from about 1 mg to about 100 mg of each of the active ingredients.
Intravenously, the
most preferred doses will range from about 0.1 to about 10 mg/kJminute during
a
constant rate infusion. Advantageously, compounds of the present invention may
be
administered in a single daily dose, or the total daily dosage may be
administered in
divided doses of two, three or four times daily. Dosage levels of the cyclic-
GMP-
specific phosphodiesterase inhibitor or alpha-adrenergic receptor antagonist
of
between about 0.001 to 50 mg/kg of body weight daily, preferably about 0.005
to
about 25 mg/kg per day, and more preferably about 0.01 to about 10 mb/kg per
day
are administered to a patient to obtain effective treatment of erectile
dysfunction.
An especially preferred combination is that wherein the agonist of the
melanocortin receptor is selective for the MC-4R subtype, the cyclic-GMP-
specific
phosphodiesterase inhibitor is the PDE-V inhibitor sildenafil citrate or IC-
351, and the
alpha-adrenergic receptor antagonist is the alpha-2 antagonist MK-912. In this
especially preferred combination, dosage levels of each component are as noted
above; however, it is even more preferred that the agonist of the MC-4R
subtype be
administered at a dosage rate of about 0.01 to about 10 mg/kg/day, especially
about
0.05 to about 5.0 mg/kg/day, and more particularly about 0.1 to about 5
mg/kglday,
and that the PDE-V inhibitor, sildenafil citrate or IC-351, or the alpha-2
antagonist
MK-912 be administered at a dosage level of about 0.001 to about 20 mg/kg/day,
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WO 00/53148 PCT/US00/05711
especially about 0.005 to about 10 mg/kJday, and more particularly about 0.01
to
about 5 mJkg/day.
More particularly illustrating the invention is a pharmaceutical
composition comprising any of the compounds described above and a
pharmaceutically acceptable carrier. Another example of the invention is a
pharmaceutical composition made by combining any of the compounds described
above and a pharmaceutically acceptable Garner. Another illustration of the
invention
is a process for making a pharmaceutical composition comprising combining any
of
the compounds descr7bed above and a pharmaceutically acceptable Garner.
The dosage regimen utilizing the compounds of the present invention
is selected in accordance with a variety of factors including type, species,
age, weight;
sex and medical condition of the patient; the severity of the condition to be
treated;
the route of administration; the renal and hepatic function of the patient;
and the
particular compound or salt thereof employed. An ordinarily skilled physician,
veterinarian or clinician can readily determine and prescribe the effective
amount of
the drug required to prevent, counter or arrest the progress of the condition:
The test procedures used to measure the efficacy of he combination of
the present invention to treat erectile dysfunction are described below in the
following
examples. These examples are not intended to be limitations on the scope of
the
instant invention in any way, and they should not be so construed.
EXAMPLE 1
Bindin~Assay.
The membrane binding assay is used to identify competitive inhibitors
of 1?5I-cc-NDP-MSH binding to cloned human melanocortin receptors expressed in
L- or CHO- cells.
Cell lines expressing melanocortin receptors are grown in T-180 flasks
containing selective medium of the composiiton: 1 L Dulbecco's modified Eagles
Medium (DMEM) with 4.5 g L-glucose, 25 mM Hepes, without sodium pyruvate,
(GibcoBRl); 100 ml 10% heat-inactivated fetal bovine serum (Sigma); 10 ml
10,000
unit/ml penicillin & 10,000 p,g/ml streptomycin (GibcoBRl); 10 m1200 mM L-
glutamine (GibcoBRl); 1 mg/ml Geneticin (G418) (GibcoBRl). The cells are grown
at 37°C with C02 and humidity control until the desired cell density
and cell number
are obtained.
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The medium is poured off and 10 mls/monolayer of enzyme-free
dissociation media (Specialty Media Inc.) is added. The cells are incubated at
37°C
for 10 minutes or until cells slouch off when flask is banged against hand.
The cells are harvested into 200 ml centrifuge tubes and spun: at 1000
rpm, 4°C; for 10 min: The supernatant is discarded and the cells are
resuspended in-~
mls/monolayer membrane preparation buffer having the composition: 10 mM Tris
pH
7.2-7.4; 4 Etg/ml Leupeptin (Sigma); 10 l.tM Phosphoramidon (Boehringer
Mannheim); 40 ~g/ml Bacitracin (Sigma); 5 ~.j/ml Aprotinin (Sigma); 10 mM
Pefabloc (Boehrin~er Mannheim). The cells are homogenized with motor-driven
dounce (Talbot' setting 40), using l0 strokes and the homogenate centrifuged
at 6,000
mpm, 4°C, for 15 minutes.
The pellets are resuspended in 0.2 mls/monolayer membrane prep
buffer and aliquots are placed in tubes (500-1000 ~I/tube) and quick frozen in
liquid
nitrogen and then stored at -80°C.
Test compounds or unlabelled NDP-a-MSH is added to 100 ~L of
membrane binding buffer to a final concentration of 1 ~M. The membrane binding
buffer has the composition: Sfl mM Tris pH 7.2; 2 mM CaCl2; 1 mM MgCl25 mM
KC1; 0:2% BSA; 4 yg/ml Leupeptin (SIGMA); 10 ~M Phosphoramidon (Boehringer
Mannheim); 40 ~,g/ml Bacitracin (SIGMA); 5 ~.g/ml Aprotinin (SIGMA); and 10
mM Pefabloc (Boehringer Mannheim). One hundred p,1 of membrane binding buffer
containing 10-40 ~g membrane protein is added, followed by 100 p;M 125I-NDP-a-
MSH to final concentration of 100 pM. The resulting mixture is vortexed
briefly and
incubated for 90-120 min at room temperature while shaking:
The mixture is filtered with a Packard Microplate 196 filter apparatus
using Packard Unifilter 96-well GF/C filter with 0.1 % polyethyleneimine
(Sigma).
The filter is washed (5 times with a total of 10 ml per well) with room
temperature of
filter wash having the composition: SOmM Tris-HCI pH 7.2 and 20 mM NaCI. The
filter is dried, and the bottom sealed and 50 ~1 of Packard Microseint-20 is
added to
each well. The top is sealed and the radioactivity quantitated in a Packard
Topcount
Microplate Scintillation counter.
EXAMPLE 2
Functional assay.
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WO 00/53148 PCT/US00/05711
Functional cell based assays are developed to discriminate
melanocortin agonists and antagonists.
Cells (for example, CHO- or L-cells or other eukaryotic cells)
expressing a human melanocortin receptor[see e:g. Yang-YK; Ollmann-MM; Wilson-
BD; Dickinson-C; Yamada-T; Barsh-GS; Gantz-I; Mol. Endocrinol., 11: 274-80
(1997)] are dissociated from tissue culture flasks by rinsing with Ca and Mj
free
phosphate buffered saline ( 14190-136, Life Technologies, Gaithersburg, MD)
and
detached following 5 minutes incubation at 37°C with enzyme free
dissociation buffer
(S-014-B, Specialty Media, Lavellette, NJ). Cells are collected by
centrifugation and
resuspended in Earle's Balanced Salt Solution (14015-069, Life Technologies,
Gaithersburg, MD) with additions of 10 mM HEPES pH 7.5; 5 mM MgCl2, 1 mM'
glutamine and 1 mg/ml bovine serum albumin: Cells are counted and diluted to 1
to 5
x 106/m1. The phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine is added
to
cells to 0.6 mM.
Test compounds are diluted in dimethylsulfoxide (DMSO) (10-5 to 10-
10 M) and 0.1 volume of compound solution is added to 0.9 volumes of cell
suspension; the final DMSO concentration is 1%. After room temperature
incubation
for 45 min., cells are lysed by incubation at 100°C for 5 min. to
release accumulated
cAMP.
cAMP is measured in an aliquot of the cell lysate with the Amersham
(Arlington Heights, IL) cAMP detection assay (RPA556). The amount of cAMP
production which results from an unknown compound is compared to that amount
of
CAMP produced in response to alpha-MSH which is defined as a 100% agonist. The
EC50 is defined as the compound concentration which results in half maximal
stimulation; when compared to its own maximal level of stimulation.
Antagonist assay: Antagonist activity is defined as the ability of a
compound to block cAMP production in response to alpha-MSH. Solution of test
compounds and suspension of receptor containing cells are prepared and mixed
as
described above; the mixture is incubated for 15 min.; and an ECSp dose
(approximately 10 nM alpha-MSH) is added to the cells. The assay is terminated
at
45 min. and cAMP quantitated as above. Percent inhibition is determined by
comparing the amount of cAMP produced in the presence to that produced in the
absence of test compound.
EXAMPLE 3
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Rat Ex Copula Assay.
Sexually mature male Caesarian Derived Sprague Dawley (CD) rats
(over 60 days old) are used with the suspensory ligament surgically removed to
prevent retraction of the penis back into the penile sheath during the ex
copula
evaluations. Animals receive food and water arl lib and are kept on a normal
light/dark cycle. Studies are conducted during the light cycle.
a) Conditioning to Supine Restraint for Ex Copula Reflex Tests.
I0 This conditioning takes ~ 4 days. Day 1, the animals are placed in a
darkened
restrainer and left for 15 - 30 minutes. Day 2, the animals are restrained in
a supine
position in the restrainer for 15 - 30 minutes. Day 3; the animals are
restrained in the
supine position with the penile sheath retracted for 15 - 30 minutes. Day 4,
the
animals are restrained in the supine position with the penile sheath retracted
until
penile responses are observed. Some animals require additional days of
conditioning
before they are completely acclimated to the procedures; non-responders are
removed
from further evaluation. After any handling or evaluation, animals are given a
treat to
ensure positive reinforcement.
b) Ex Copula Reflex Tests. Rats are gently restrained in a supine
position with their anterior torso placed inside a cylinder of adequate size
to allow for
normal head and paw grooming. For a 400-500 gram rat, the diameter of the
cylinder
is approximately 8 cm. The lower torso and hind limbs are restrained with a
non-
adhesive material (vetrap). An additional piece of vetrap with a hole in it,
through
which the glans penis will be passed, is fastened over the animal to maintain
the
preputial sheath in a retracted position. Penile responses will be observed,
typically
termed ex copula genital reflex tests. Typically, a series of penile erections
will occur
spontaneously within a few minutes after sheath retraction. The types of
normal
reflexogenic erectile responses include elongation, engorgement, cup and flip.
An
elongation is classified as an extension of the penile body. Engorgement is a
dilation
of the glans penis. A cup is defined as an intense erection where the distal
margin of
the plans penis momentarily flares open to form a cup. A flip is a
dorsiflexion of the
penile body.
Baseline and or vehicle evaluations are conducted to determine how
and if an animal will respond. Some animals have a long duration until the
first
response while others are non-responders altogether. During this baseline
evaluation
CA 02362918 2001-08-29
WO 00/53148 PCT/US00/05711
latency to first response, number and type of responses are recorded. :The
testing time
frame is 1~ minutes after the first response.
After a minimum of 1 day between evaluations, these same animals are
administered the test compound or combination at 20 mg/kg and evaluated for
penile
reflexes. All evaluations are videotaped and scored later. Data are collected
and
analyzed using paired 2 tailed t-tests to compare baseline and/or vehicle
evaluations to
druj- or combination- treated evaluations for individual animals. Groups of a
minimum of 4 animals are utilized to reduce variability:
Positive reference controls are included in each study to assure the
validity of the study. Animals can be dosed by a number of routes of
administration
depending on the nature of the study to be performed: The routes of
administration
include intravenous (IV), intraperitoneal (IP), subcutaneous (SC) and
intracerebral
ventricular (ICV).
1 ~ EXAMPLE 4
Models of Female Sexual Dysfunction
Rodent assays relevant to female sexual receptivity include the
behavioral model of lordosis and direct observations of copulatory activity.
There is
also a urethrogenital reflex model in anesthetized spinally tranSected rats
for
measuring orgasm in both male and female rats. These and other established
animal
models of female sexual dysfunction are described in McKenna KE et al, A Model
For The Study Of Sexual Function In Anesthetized Male And Female Rats, Am. J.
Physiol. (Regulatory Integrative Comp. Physiol 30): 81276-81285, 1991; McKenna
KE et al, Modulation By Peripheral Serotonin Of The Threshold For Sexual
Reflexes
In Female Rats, Pharm. Bioch. Behav., 40:151-156, 1991; and Takahashi LK et
al,
Dual Estradiol Action In The Diencephalon And The Regulation Of Sociosexual
Behavior In Female Golden Hamsters Brain Res., 359:194-207, 1985:
EXAMPLE S
As a specific embodiment of an oral composition of a combination of
the present invention, S mg of a melanocortin agonist and 10 mg of a type V
phosphodiesterase (PDE-V) inhibitor are formulated with sufficient finely
divided
lactose to provide a total amount of 580 to 590 mg to fill a size O hard
gelatin
capsule.
CA 02362918 2001-08-29
WO 00/53148 PCT/US00/05711
EXAMPLE 6
As another specific embodiment of an oral composition of a
combination of the present invention, 2.5 mg of a melanocortin agonist and 5
mg of
an alpha-2 receptor antagonist are formulated with sufficient finely divided
lactose to
provide a total amount of 580 to 590 mg to fill a size O hard gelatin capsule.
While the invention has been described and illustrated with reference
to certain particular embodiments thereof, those skilled in the art will
appreciate that
various changes, modifications and substitutions can be made therein without
departing from the spirit and scope of the invention. For example, effective
dosajes
other than the particular dosages as set forth herein above may be applicable
as a
consequence of variations in the responsiveness of the patient being treated
for
erectile dysfunction. Likewise, the specific pharmacological responses
observed may
vary according to and depending upon the particular active compound or
combination
selected or whether there are present pharmaceutical carriers, as well as the
type of
formulation and mode of administration employed, and such expected variations
or
differences in the results are contemplated in accordance with the objects and
practices of the present invention. It is intended, therefore, that the
invention be
defined by the scope of the claims which follow and that such claims be
interpreted as
broadly as is reasonable.
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