U.S. patent application number 14/315998 was filed with the patent office on 2014-10-16 for oligomer-corticosteroid conjugates.
The applicant listed for this patent is NAKTAR THERAPEUTICS. Invention is credited to Michael D. Bentley, J. Milton Harris, Jennifer Riggs-Sauthier, Wen Zhang.
Application Number | 20140309398 14/315998 |
Document ID | / |
Family ID | 40227650 |
Filed Date | 2014-10-16 |
United States Patent
Application |
20140309398 |
Kind Code |
A1 |
Zhang; Wen ; et al. |
October 16, 2014 |
OLIGOMER-CORTICOSTEROID CONJUGATES
Abstract
The invention provides corticosteroids that are chemically
modified by covalent attachment of a water-soluble oligomer. A
compound of the invention, when administered by any of a number of
administration routes, exhibits different properties compared to
the properties of the corticosteroid not attached to the
water-soluble oligomer.
Inventors: |
Zhang; Wen; (San Ramon,
CA) ; Riggs-Sauthier; Jennifer; (San Francisco,
CA) ; Harris; J. Milton; (Huntsville, AL) ;
Bentley; Michael D.; (Huntsville, AL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NAKTAR THERAPEUTICS |
San Francisco |
CA |
US |
|
|
Family ID: |
40227650 |
Appl. No.: |
14/315998 |
Filed: |
June 26, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12680877 |
Jun 18, 2010 |
8796248 |
|
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PCT/US08/11523 |
Oct 3, 2008 |
|
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14315998 |
|
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|
60997835 |
Oct 5, 2007 |
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Current U.S.
Class: |
528/228 ;
552/518 |
Current CPC
Class: |
A61P 25/24 20180101;
A61K 47/60 20170801; A61K 31/573 20130101; A61P 25/00 20180101;
A61P 1/08 20180101; A61P 25/08 20180101; A61K 47/59 20170801; A61P
25/22 20180101; C07J 41/0005 20130101 |
Class at
Publication: |
528/228 ;
552/518 |
International
Class: |
A61K 31/573 20060101
A61K031/573; A61K 47/48 20060101 A61K047/48 |
Claims
1. A compound comprising a corticosteroid residue covalently
attached via a releasable linkage to a poly(ethylene oxide),
wherein the corticosteroid residue is a residue dexamethasone and
the poly(ethylene oxide) is branched.
2. The compound of claim 1, wherein the molecular weight of the
poly(ethylene oxide) is below about 1500 Daltons.
3. The compound of claim 1, wherein the molecular weight of the
poly(ethylene oxide) is below about 1300 Daltons.
4. The compound of claim 1, wherein the molecular weight of the
poly(ethylene oxide) is below about 1000 Daltons.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 12/680,877, filed Jun. 18, 2010, which is a 35
U.S.C. .sctn.371 application of International Application No.
PCT/US2008/011523, filed Oct. 3, 2008, designating the United
States, which claims the benefit of priority under 35 U.S.C.
.sctn.119(e) to U.S. Provisional Patent Application Ser. No.
60/997,835, filed Oct., 5 2007, the disclosures of which is are
incorporated herein by reference in their entireties.
FIELD OF THE INVENTION
[0002] This invention comprises (among other things) chemically
modified corticosteroids that possess certain advantages over
corticosteroids lacking the chemical modification. The chemically
modified corticosteroids described herein relate to and/or have
application(s) in (among others) the fields of drug discovery,
pharmacotherapy, physiology, organic chemistry and polymer
chemistry.
BACKGROUND OF THE INVENTION
[0003] Corticosteroids represent a broad class of agents employed
in the treatment of individuals suffering from a variety of
disorders. In the treatment of an individual suffering from
arthritis, for example, administration of a corticosteroid may
reduce inflammation. In addition, individuals suffering autoimmune
disorders often benefit from the administration of a
corticosteroid. Other applications in which corticosteroids have
been used include the treatment of individuals suffering from
allergic reactions, ankylosing spondylitis, asthma, Crohn's disease
dermatological disorders and psoriasis among others. As a class,
corticosteroids represent an important and widely used tool in
pharmacotherapy.
[0004] Although corticosteroids serve an important role in treating
patients, their use is sometimes associated with (among other
things) CNS side effects, such as insomnia, eurphoria, mood
changes, nervousness, personality changes, depression, nausea,
headaches and convulsions.
[0005] As a consequence, pharmacotherapy with corticosteroids would
be improved if these and/or other side effects associated with
their use could be decreased.
[0006] The present invention seeks to address these and other needs
in the art.
SUMMARY OF THE INVENTION
[0007] In one or more embodiments of the invention, a compound is
provided, the compound comprising a corticosteroid residue
covalently attached via a hydrazone linkage to a water-soluble,
non-peptidic oligomer.
[0008] In one or more embodiments of the invention, a compound is
provided, the compound comprising a corticosteroid residue
covalently attached via a hydrazone linkage to a water-soluble,
non-peptidic oligomer, wherein the weight average molecular weight
of the water-soluble, non-peptidic oligomer is less than 400
Daltons.
[0009] In one or more embodiments of the invention, a compound is
provided, the compound comprising a corticosteroid residue
covalently attached (either directly or through one or more atoms)
at a position other than through the 16 or 17 positions to a
water-soluble, non-peptidic oligomer.
[0010] In one or more embodiments of the invention, a compound is
provided, the compound comprising a corticosteroid residue
covalently attached (either directly or through one or atoms) at a
position other than through D-ring atom positions to a
water-soluble, non-peptidic oligomer.
[0011] In one or more embodiments of the invention, a compound is
provided, the compound comprising a corticosteroid residue
covalently attached (either directly or through one or more atoms)
at a position selected from the consisting of A-ring atom
positions, B-ring atom positions, and C-ring atom positions to a
water-soluble, non-peptidic oligomer.
[0012] In one or more embodiments of the invention, a compound is
provided, the compound comprising a corticosteroid residue
covalently attached (either directly or through one or more atoms)
at A-ring atom positions to a water-soluble, non-peptidic
oligomer.
[0013] In one or more embodiments of the invention, a compound is
provided, the compound comprising a corticosteroid residue
covalently attached at the 3 position to a water-soluble,
non-peptidic oligomer.
[0014] Exemplary compounds of the invention include those having
the following structure:
##STR00001##
wherein:
[0015] the dashed line independently represents an optional double
bond;
[0016] R.sup.1 is selected from the group consisting of halo (e.g.,
fluoro, chloro, bromo, iodo) and alkyl;
[0017] either [0018] R.sup.2 is selected from the group consisting
of hydroxy and alkyl and R.sup.3 is selected from the group
consisting of hydroxy, alkyl, --OC(O)-alkyl, and --OC(O)-cyclo, or
[0019] R.sup.2 and R.sup.3 combine to form a moiety selected from
the group consisting of
##STR00002##
[0020] R.sup.4 is selected from the group consisting of --CH.sub.3,
--CH.sub.2--OH, --CH.sub.2-halo, --S--CH.sub.2-halo,
--CH.sub.2--O--C(O)--CH.sub.3,
--CH.sub.2--O--C(O)--CH.sub.2--CH.sub.3, --CH.sub.2--PO.sub.4,
--CH.sub.2--O--C(O)--C(CH.sub.3).sub.3,
--CH.sub.2--O--C(O)--CH.sub.2--CH.sub.2--CH.sub.2--CH.sub.3,
--CH.sub.2--C(O)--O--CH.sub.3,
--CH.sub.2--O--C(O)--CH.sub.2--CH.sub.2--C(O)--OH;
[0021] either [0022] R.sup.5 is --H and R.sup.6 is selected from
the group consisting of --H and hydroxy, or [0023] R.sup.5 and
R.sup.6 combine to form carbonyl;
[0024] R.sup.7 is halo;
[0025] X is a spacer moiety; and
[0026] POLY is a water-soluble, non-peptidic oligomer.
[0027] The "corticosteroid residue" is a compound having a
structure of a corticosteroid that is altered by the presence of
one or more bonds, which bonds serve to attach (either directly or
indirectly) one or more water-soluble, non-peptidic oligomers. In
this regard, any compound having corticosteroid activity can be
used. Exemplary corticosteroids have a structure encompassed by the
structure defined herein as Formula I:
##STR00003##
[0028] wherein:
[0029] the dashed line independently represents an optional double
bond;
[0030] R.sup.1 is selected from the group consisting of halo (e.g.,
fluoro, chloro, bromo, iodo) and alkyl;
[0031] either R.sup.2 is selected from the group consisting of
hydroxy and alkyl and R.sup.3 is selected from the group consisting
of hydroxy, alkyl, --OC(O)-alkyl, and --OC(O)-cyclo, or R.sup.2 and
R.sup.3 combine to form a moiety selected from the group consisting
of
##STR00004##
[0032] R.sup.4 is selected from the group consisting of --CH.sub.3,
--CH.sub.2--OH, --CH.sub.2-halo, --S--CH.sub.2-halo,
--CH.sub.2--O--C(O)--CH.sub.3,
--CH.sub.2--O--C(O)--CH.sub.2--CH.sub.3, --CH.sub.2--PO.sub.4,
--CH.sub.2--O--C(O)--C(CH.sub.3).sub.3,
--CH.sub.2--O--C(O)--CH.sub.2--CH.sub.2--CH.sub.2--CH.sub.3,
--CH.sub.2--C(O)--O--CH.sub.3,
--CH.sub.2--O--C(O)--CH.sub.2--CH.sub.2--C(O)--OH;
[0033] either R.sup.5 is --H and R.sup.6 is selected from the group
consisting of --H and hydroxy, or R.sup.5 and R.sup.6 combine to
form carbonyl; and
[0034] R.sup.7 is halo.
[0035] In one or more embodiments of the invention, a composition
is provided, the composition comprising a compound comprising a
corticosteroid residue covalently attached via a stable or
degradable linkage to a water-soluble and non-peptidic oligomer,
and optionally, a pharmaceutically acceptable excipient.
[0036] In one or more embodiments of the invention, a dosage form
is provided, the dosage form comprising a compound comprising a
corticosteroid residue covalently attached via a stable or
degradable linkage to a water-soluble, non-peptidic oligomer,
wherein the compound is present in a dosage form.
[0037] In one or more embodiments of the invention, a method is
provided, the method comprising covalently attaching a
water-soluble, non-peptidic oligomer to a corticosteroid.
[0038] In one or more embodiments of the invention, a method is
provided, the method comprising administering a compound comprising
a corticosteroid residue covalently attached via a stable or
degradable linkage to a water-soluble, non-peptidic oligomer.
[0039] These and other objects, aspects, embodiments and features
of the invention will become more fully apparent to one of ordinary
skill in the art when read in conjunction with the following
detailed description.
BRIEF DESCRIPTION OF THE DRAWING
[0040] FIG. 1 is a drawing presenting results obtain in connection
with Example 3.
DETAILED DESCRIPTION OF THE INVENTION
[0041] As used in this specification, the singular forms "a," "an,"
and "the" include plural referents unless the context clearly
dictates otherwise.
[0042] In describing and claiming the present invention, the
following terminology will be used in accordance with the
definitions described below.
[0043] "Water soluble, non-peptidic oligomer" indicates an oligomer
that is at least 35% (by weight) soluble, preferably greater than
95% (by weight), in water at room temperature. An unfiltered
aqueous preparation of a "water-soluble" oligomer transmits at
least 75%, more preferably at least 95%, of the amount of light
transmitted by the same solution after filtering. On a weight
basis, a "water soluble" oligomer is preferably at least 35% (by
weight) soluble in water, more preferably at least 50% (by weight)
soluble in water, still more preferably at least 85% (by weight)
soluble in water. It is preferred, however, that the water-soluble
oligomer is at least 95% (by weight) soluble in water or completely
soluble in water.
[0044] The terms "monomer," "monomeric subunit" and "monomeric
unit" are used interchangeably herein and refer to one of the basic
structural units of a polymer or oligomer. In the case of a
homo-oligomer, this is defined as a structural repeating unit of
the oligomer. In the case of a co-oligomer, a monomeric unit is
more usefully defined as the residue of a monomer which was
oligomerized to form the oligomer, since the structural repeating
unit may include more than one type of monomeric unit. Preferred
oligomers are homo-oligomers.
[0045] An "oligomer" is a molecule possessing from about 1 to about
30 monomers. Specific oligomers for use in the invention include
those having a variety of geometries such as linear, branched, or
forked, to be described in greater detail below.
[0046] "PEG" or "polyethylene glycol," as used herein, is meant to
encompass any water-soluble poly(ethylene oxide). Unless otherwise
indicated, a "PEG oligomer" or an oligoethylene glycol is one in
which substantially all (preferably all) monomeric subunits are
ethylene oxide subunits, though the oligomer may contain distinct
end capping moieties or functional groups, e.g., for conjugation.
PEG oligomers for use in the present invention may comprise the
following structures: "--(CH.sub.2CH.sub.2O).sub.n-" or
"--(CH.sub.2CH.sub.2O).sub.n-1CH.sub.2CH.sub.2--," depending upon
whether or not the terminal oxygen(s) has been displaced, e.g.,
during a synthetic transformation. As stated above, for the PEG
oligomers, the variable (n) ranges from 1 to 30, and the terminal
groups and architecture of the overall PEG can vary. When PEG
further comprises a functional group, A, for linking to, e.g., a
small molecule drug, the functional group when covalently attached
to a PEG oligomer does not result in formation of (i) an
oxygen-oxygen bond (--O--O--, a peroxide linkage), or (ii) a
nitrogen-oxygen bond (N--O, O--N).
[0047] The terms "end-capped" or "terminally capped" are
interchangeably used herein to refer to a terminal or endpoint of a
polymer having an end-capping moiety. Typically, although not
necessarily, the end-capping moiety comprises a hydroxy or
C.sub.1-20 alkoxy group. Thus, examples of end-capping moieties
include alkoxy (e.g., methoxy, ethoxy and benzyloxy), as well as
aryl, heteroaryl, cyclo, heterocyclo, and the like. In addition,
saturated, unsaturated, substituted and unsubstituted forms of each
of the foregoing are envisioned. Moreover, the end-capping group
can also be a silane. The end-capping group can also advantageously
comprise a detectable label. When the polymer has an end-capping
group comprising a detectable label, the amount or location of the
polymer and/or the moiety (e.g., active agent) of interest to which
the polymer is coupled, can be determined by using a suitable
detector. Such labels include, without limitation, fluorescers,
chemiluminescers, moieties used in enzyme labeling, colorimetric
moieties (e.g., dyes), metal ions, radioactive moieties, and the
like. Suitable detectors include photometers, films, spectrometers,
and the like.
[0048] "Branched", in reference to the geometry or overall
structure of an oligomer, refers to an oligomer having two or more
polymer "arms" extending from a branch point.
[0049] "Forked" in reference to the geometry or overall structure
of an oligomer, refers to an oligomer having two or more functional
groups (through one or more atoms) extending from a branch
point.
[0050] A "branch point" refers to a bifurcation point comprising
one or more atoms at which an oligomer branches or forks from a
linear structure into one or more additional arms.
[0051] The terms "reactive" and "activated" refer to a functional
group that reacts readily or at a practical rate under conventional
conditions of organic synthesis. This is in contrast to those
groups that either do not react or require strong catalysts or
impractical reaction conditions in order to react (i.e., a
"nonreactive" or "inert" group).
[0052] "Not readily reactive," with reference to a functional group
present on a molecule in a reaction mixture, indicates that the
group remains largely intact under conditions that are effective to
produce a desired reaction in the reaction mixture.
[0053] A "protecting group" is a moiety that prevents or blocks
reaction of a particular chemically reactive functional group in a
molecule under certain reaction conditions. The protecting group
may vary depending upon the type of chemically reactive group being
protected as well as the reaction conditions to be employed and the
presence of additional reactive or protecting groups in the
molecule. Functional groups which may be protected include, by way
of example, carboxylic acid groups, amino groups, hydroxyl groups,
thiol groups, carbonyl groups and the like. Representative
protecting groups for carboxylic acids include esters (such as a
p-methoxybenzyl ester), amides and hydrazides; for amino groups,
carbamates (such as tert-butoxycarbonyl) and amides; for hydroxyl
groups, ethers and esters; for thiol groups, thioethers and
thioesters; for carbonyl groups, acetals and ketals; and the like.
Such protecting groups are well-known to those skilled in the art
and are described, for example, in T. W. Greene and G. M. Wuts,
Protecting Groups in Organic Synthesis, Third Edition, Wiley, New
York, 1999, and references cited therein.
[0054] A functional group in "protected form" refers to a
functional group bearing a protecting group. As used herein, the
term "functional group" or any synonym thereof encompasses
protected forms thereof.
[0055] A "physiologically cleavable" or "hydrolyzable" or
"degradable" bond is a relatively labile bond that reacts with
water (i.e., is hydrolyzed) under physiological conditions. The
tendency of a bond to hydrolyze in water may depend not only on the
general type of linkage connecting two central atoms but also on
the substituents attached to these central atoms. Appropriate
hydrolytically unstable or weak linkages include but are not
limited to carboxylate ester, phosphate ester, anhydrides, acetals,
ketals, acyloxyalkyl ether, imines, orthoesters, peptides,
oligonucleotides, thioesters, thiolesters, and carbonates.
[0056] An "enzymatically degradable linkage" means a linkage that
is subject to degradation by one or more enzymes.
[0057] A "stable" linkage or bond refers to a chemical bond that is
substantially stable in water, that is to say, does not undergo
hydrolysis under physiological conditions to any appreciable extent
over an extended period of time. Examples of hydrolytically stable
linkages include but are not limited to the following:
carbon-carbon bonds (e.g., in aliphatic chains), ethers, amides,
urethanes, amines, and the like. Generally, a stable linkage is one
that exhibits a rate of hydrolysis of less than about 1-2% per day
under physiological conditions. Hydrolysis rates of representative
chemical bonds can be found in most standard chemistry
textbooks.
[0058] "Substantially" or "essentially" means nearly totally or
completely, for instance, 95% or greater, more preferably 97% or
greater, still more preferably 98% or greater, even more preferably
99% or greater, yet still more preferably 99.9% or greater, with
99.99% or greater being most preferred of some given quantity.
[0059] "Monodisperse" refers to an oligomer composition wherein
substantially all of the oligomers in the composition have a
well-defined, single (i.e., the same) molecular weight and defined
number of monomers, as determined by chromatography or mass
spectrometry. Monodisperse oligomer compositions are in one sense
pure, that is, substantially having a single and definable number
(as a whole number) of monomers rather than a large distribution. A
monodisperse oligomer composition possesses a MW/Mn value of 1.0005
or less, and more preferably, a MW/Mn value of 1.0000. By
extension, a composition comprised of monodisperse conjugates means
that substantially all oligomers of all conjugates in the
composition have a single and definable number (as a whole number)
of monomers rather than a large distribution and would possess a
MW/Mn value of 1.0005, and more preferably, a MW/Mn value of 1.0000
if the oligomer were not attached to the corticosteroid residue. A
composition comprised of monodisperse conjugates may, however,
include one or more nonconjugate substances such as solvents,
reagents, excipients, and so forth.
[0060] "Bimodal," in reference to an oligomer composition, refers
to an oligomer composition wherein substantially all oligomers in
the composition have one of two definable and different numbers (as
whole numbers) of monomers rather than a large distribution, and
whose distribution of molecular weights, when plotted as a number
fraction versus molecular weight, appears as two separate
identifiable peaks. Preferably, for a bimodal oligomer composition
as described herein, each peak is generally symmetric about its
mean, although the size of the two peaks may differ. Ideally, the
polydispersity index of each peak in the bimodal distribution,
Mw/Mn, is 1.01 or less, more preferably 1.001 or less, and even
more preferably 1.0005 or less, and most preferably a MW/Mn value
of 1.0000. By extension, a composition comprised of bimodal
conjugates means that substantially all oligomers of all conjugates
in the composition have one of two definable and different numbers
(as whole numbers) of monomers rather than a large distribution and
would possess a MW/Mn value of 1.01 or less, more preferably 1.001
or less and even more preferably 1.0005 or less, and most
preferably a MW/Mn value of 1.0000 if the oligomer were not
attached to the corticosteroid residue. A composition comprised of
bimodal conjugates may, however, include one or more nonconjugate
substances such as solvents, reagents, excipients, and so forth
[0061] A "corticosteroid" refers to an organic, inorganic, or
organometallic compound having a molecular weight of less than
about 1000 Daltons and having some degree of corticosteroid
activity. Corticosteroid activity can be measured by art-known
methods. For example, corticosteroid activity can be measured by
testing male Sprague-Dawley rats by injecting a relatively large
amount (e.g., 5-20 mg/kg) of the compound of interest into an
animal. After three days, the thymus glands can be removed and
weighed using the procedure described in Vicent et al. (1997) Mol.
Pharmacol. 52:749-753.
[0062] A "biological membrane" is any membrane made of cells or
tissues that serves as a barrier to at least some foreign entities
or otherwise undesirable materials. As used herein a "biological
membrane" includes those membranes that are associated with
physiological protective barriers including, for example: the
blood-brain barrier (BBB); the blood-cerebrospinal fluid barrier;
the blood-placental barrier; the blood-milk barrier; the
blood-testes barrier; and mucosal barriers including the vaginal
mucosa, urethral mucosa, anal mucosa, buccal mucosa, sublingual
mucosa, and rectal mucosa. Unless the context clearly dictates
otherwise, the term "biological membrane" does not include those
membranes associated with the middle gastro-intestinal tract (e.g.,
stomach and small intestines).
[0063] A "biological membrane crossing rate," provides a measure of
a compound's ability to cross a biological membrane, such as the
blood-brain barrier ("BBB"). A variety of methods may be used to
assess transport of a molecule across any given biological
membrane. Methods to assess the biological membrane crossing rate
associated with any given biological barrier (e.g., the
blood-cerebrospinal fluid barrier, the blood-placental barrier, the
blood-milk barrier, the intestinal barrier, and so forth), are
known, described herein and/or in the relevant literature, and/or
may be determined by one of ordinary skill in the art.
[0064] A "reduced rate of metabolism" refers to a measurable
reduction in the rate of metabolism of a water-soluble
oligomer-small molecule drug conjugate as compared to the rate of
metabolism of the small molecule drug not attached to the
water-soluble oligomer (i.e., the small molecule drug itself) or a
reference standard material. In the special case of "reduced first
pass rate of metabolism," the same "reduced rate of metabolism" is
required except that the small molecule drug (or reference standard
material) and the corresponding conjugate are administered orally.
Orally administered drugs are absorbed from the gastro-intestinal
tract into the portal circulation and may pass through the liver
prior to reaching the systemic circulation. Because the liver is
the primary site of drug metabolism or biotransformation, a
substantial amount of drug may be metabolized before it reaches the
systemic circulation. The degree of first pass metabolism, and
thus, any reduction thereof, may be measured by a number of
different approaches. For instance, animal blood samples may be
collected at timed intervals and the plasma or serum analyzed by
liquid chromatography/mass spectrometry for metabolite levels.
Other techniques for measuring a "reduced rate of metabolism"
associated with the first pass metabolism and other metabolic
processes are known, described herein and/or in the relevant
literature, and/or can be determined by one of ordinary skill in
the art. Preferably, a conjugate of the invention can provide a
reduced rate of metabolism reduction satisfying at least one of the
following values: at least about 5%; at least about 15%; at least
about 20%; at least about 25%; at least about 30%; at least about
40%; at least about 60%, at least about 70%, at least about 80%,
and at least about 90%.
[0065] "Alkyl" refers to a hydrocarbon chain, ranging from about 1
to 20 atoms in length. Such hydrocarbon chains are preferably but
not necessarily saturated and may be branched or straight chain.
Exemplary alkyl groups include methyl, ethyl, propyl, butyl,
pentyl, 2-methylbutyl, 2-ethylpropyl, 3-methylpentyl, and the like.
As used herein, "alkyl" includes cycloalkyl when three or more
carbon atoms are referenced.
[0066] "Lower alkyl" refers to an alkyl group containing from 1 to
6 carbon atoms, and may be straight chain or branched, as
exemplified by methyl, ethyl, n-butyl, i-butyl, t-butyl.
[0067] "Non-interfering substituents" are those groups that, when
present in a molecule, are non-reactive with other functional
groups contained within the molecule.
[0068] "Alkoxy" refers to an --O--R group, wherein R is alkyl or
substituted alkyl, preferably C.sub.1-C.sub.20 alkyl (e.g.,
methoxy, ethoxy, propyloxy, benzyl, etc.), preferably
C.sub.1-C.sub.7.
[0069] "Electrophile" refers to an ion, atom, or an ionic or
neutral collection of atoms having an electrophilic center, i.e., a
center that is electron seeking, capable of reacting with a
nucleophile.
[0070] "Nucleophile" refers to an ion or atom or an ionic or
neutral collection of atoms having a nucleophilic center, i.e., a
center that is seeking an electrophilic center, and capable of
reacting with an electrophile.
[0071] "Pharmaceutically acceptable excipient" or "pharmaceutically
acceptable carrier" refers to component that may be included in the
compositions of the invention and that causes no significant
adverse toxicological effects to a patient.
[0072] The term "aryl" means an aromatic group having up to 14
carbon atoms. Aryl groups include phenyl, naphthyl, biphenyl,
phenanthrenyl, naphthacenyl, and the like. "Substituted phenyl" and
"substituted aryl" denote a phenyl group and aryl group,
respectively, substituted with one, two, three, four or five (e.g.
1-2, 1-3 or 1-4 substituents) chosen from halo (F, Cl, Br, I),
hydroxy, hydroxy, cyano, nitro, alkyl (e.g., C.sub.1-6 alkyl),
alkoxy (e.g., C.sub.1-6 alkoxy), benzyloxy, carboxy, aryl, and so
forth.
[0073] "Pharmacologically effective amount," "physiologically
effective amount," and "therapeutically effective amount" are used
interchangeably herein to mean the amount of a water-soluble
oligomer-small molecule drug conjugate present in a composition
that is needed to provide a desired level of active agent and/or
conjugate in the bloodstream or in the target tissue. The precise
amount may depend upon numerous factors, e.g., the particular
active agent, the components and physical characteristics of the
composition, intended patient population, patient considerations,
and may readily be determined by one skilled in the art, based upon
the information provided herein and available in the relevant
literature.
[0074] A "difunctional" oligomer is an oligomer having two
functional groups contained therein, typically at its termini. When
the functional groups are the same, the oligomer is said to be
homodifunctional. When the functional groups are different, the
oligomer is said to be heterobifunctional.
[0075] A basic reactant or an acidic reactant described herein
include neutral, charged, and any corresponding salt forms
thereof.
[0076] The term "patient," refers to a living organism suffering
from or prone to a condition that can be prevented or treated by
administration of a conjugate as described herein, and includes
both humans and animals.
[0077] "Optional" or "optionally" means that the subsequently
described circumstance may but need not necessarily occur, so that
the description includes instances where the circumstance occurs
and instances where it does not.
[0078] As indicated above, the present invention is directed to
(among other things) a compound comprising a corticosteroid residue
covalently attached via a stable or degradable linkage to a
water-soluble, non-peptidic oligomer.
[0079] In one or more embodiments of the invention, a compound is
provided, the compound comprising a corticosteroid residue
covalently attached via a stable or degradable linkage to a
water-soluble, non-peptidic oligomer, wherein the corticosteroid
has a structure encompassed by the following formula:
##STR00005##
wherein:
[0080] the dashed line independently represents an optional double
bond;
[0081] R.sup.1 is selected from the group consisting of halo (e.g.,
fluoro, chloro, bromo, iodo) and alkyl;
[0082] either [0083] R.sup.2 is selected from the group consisting
of hydroxy and alkyl and R.sup.3 is selected from the group
consisting of hydroxy, alkyl, --OC(O)-alkyl, and --OC(O)-cyclo, or
[0084] R.sup.2 and R.sup.3 combine to form a moiety selected from
the group consisting of
##STR00006##
[0085] R.sup.4 is selected from the group consisting of --CH.sub.3,
--CH.sub.2--OH, --CH.sub.2-halo, --S--CH.sub.2-halo,
--CH.sub.2--O--C(O)--CH.sub.3,
--CH.sub.2--O--C(O)--CH.sub.2--CH.sub.3, --CH.sub.2--PO.sub.4,
--CH.sub.2--O--C(O)--C(CH.sub.3).sub.3,
--CH.sub.2--O--C(O)--CH.sub.2--CH.sub.2--CH.sub.2--CH.sub.3,
--CH.sub.2--C(O)--O--CH.sub.3,
--CH.sub.2--O--C(O)--CH.sub.2--CH.sub.2--C(O)--OH;
[0086] either [0087] R.sup.5 is --H and R.sup.6 is selected from
the group consisting of --H and hydroxy, or [0088] R.sup.5 and
R.sup.6 combine to form carbonyl; and R.sup.7 is halo.
[0089] Examples of specific corticosteroids include those selected
from the group consisting of desoxycorticosone, hydrocortisone,
cortisone, methylprednisolone, prednisone, prednisolone,
triamcinolone, dexamethasone, betamethasone, beclomethasone,
beclomethasone-17,21-dipropionate, budesonide, flunisolide,
fludrocortisone, mometasone, fluticasone, alclometasone,
clocortolone, flurandrenolide, fluocinonide, hydrocortisone
acetate, fluorometholone, fluocinolone acetonide, diflucortolone
valerate, paramethasone acetate, halcinonide, hydrocortisone
phosphate, clobetasone butyrate, amcinonide, and prednisolone
succinate.
[0090] As used herein, the conventional ring atom numbering system
for identifying positions of atoms and rings within a
corticosteroid will be used, as follows:
##STR00007##
[0091] One of ordinary skill in the art will readily determine the
positions of atoms and rings of the corresponding corticosteroid
residue. When referring to positions of attachment, it will be
understood that when a given moiety is stated to be attached at a
certain numbered position or a position within a ring it can be
either direct (i.e., directly to one of the ring atoms numbered 1
through 17) or indirect (i.e., one or more atoms linking the moiety
to one of the ring atoms numbered one 1 through 17). As used
herein, the first numbered ring atom to which a given moiety is
attached determines that moiety's attachment site. Thus, a
corticosteroid residue attached in accordance with Formula I-C is
only considered attached to an oligomer at the 3-position, and not
(for example) attached to the 2 position by way of the ring atom at
the 3-position.
[0092] Use of discrete oligomers (e.g., from a monodisperse or
bimodal composition of oligomers, in contrast to relatively impure
compositions) to form oligomer-containing compounds can
advantageously alter certain properties associated with the
corresponding small molecule drug. For instance, a compound of the
invention, when administered by any of a number of suitable
administration routes, such as parenteral, oral, transdermal,
buccal, pulmonary, or nasal, exhibits reduced penetration across
the blood-brain barrier. It is preferred that the compounds of the
invention exhibit slowed, minimal or effectively no crossing of the
blood-brain barrier, while still crossing the gastro-intestinal
(GI) walls and into the systemic circulation if oral delivery is
intended. Moreover, the compounds of the invention maintain a
degree of bioactivity as well as bioavailability in comparison to
the bioactivity and bioavailability of the compound free of all
oligomers.
[0093] With respect to the blood-brain barrier ("BBB"), this
barrier restricts the transport of drugs from the blood to the
brain. This barrier consists of a continuous layer of unique
endothelial cells joined by tight junctions. The cerebral
capillaries, which comprise more than 95% of the total surface area
of the BBB, represent the principal route for the entry of most
solutes and drugs into the central nervous system.
[0094] For compounds whose degree of blood-brain barrier crossing
ability is not readily known, such ability can be determined using
a suitable animal model such as an in situ rat brain perfusion
("RBP") model as described herein. Briefly, the RBP technique
involves cannulation of the carotid artery followed by perfusion
with a compound solution under controlled conditions, followed by a
wash out phase to remove compound remaining in the vascular space.
(Such analyses can be conducted, for example, by contract research
organizations such as Absorption Systems, Exton, Pa.). In one
example of the RBP model, a cannula is placed in the left carotid
artery and the side branches are tied off. A physiologic buffer
containing the analyte (typically but not necessarily at a 5
micromolar concentration level) is perfused at a flow rate of about
10 mL/minute in a single pass perfusion experiment. After 30
seconds, the perfusion is stopped and the brain vascular contents
are washed out with compound-free buffer for an additional 30
seconds. The brain tissue is then removed and analyzed for compound
concentrations via liquid chromatograph with tandem mass
spectrometry detection (LC/MS/MS). Alternatively, blood-brain
barrier permeability can be estimated based upon a calculation of
the compound's molecular polar surface area ("PSA"), which is
defined as the sum of surface contributions of polar atoms (usually
oxygens, nitrogens and attached hydrogens) in a molecule. The PSA
has been shown to correlate with compound transport properties such
as blood-brain barrier transport. Methods for determining a
compound's PSA can be found, e.g., in, Ertl, P., et al., J. Med.
Chem. 2000, 43, 3714-3717; and Kelder, J., et al., Pharm. Res.
1999, 16, 1514-1519.
[0095] With respect to the blood-brain barrier, the water-soluble,
non-peptidic oligomer-small molecule drug conjugate exhibits a
blood-brain barrier crossing rate that is reduced as compared to
the crossing rate of the small molecule drug not attached to the
water-soluble, non-peptidic oligomer. Exemplary reductions in
blood-brain barrier crossing rates for the compounds described
herein include reductions of: at least about 5%; at least about
10%; at least about 25%; at least about 30%; at least about 40%; at
least about 50%; at least about 60%; at least about 70%; at least
about 80%; or at least about 90%, when compared to the blood-brain
barrier crossing rate of the small molecule drug not attached to
the water-soluble oligomer. A preferred reduction in blood-brain
barrier crossing rate for a conjugate of the invention is at least
about 20%.
[0096] As indicated above, the compounds of the invention include a
corticosteroid residue. Assays for determining whether a given
compound (regardless of whether the compound includes a
water-soluble, non-peptidic oligomer or not) act as a
corticosteroid are described herein.
[0097] In one or more embodiments, the corticosteroid is one of the
following corticosteroids:
##STR00008## ##STR00009## ##STR00010## ##STR00011## ##STR00012##
##STR00013## ##STR00014##
[0098] In some instances, corticosteroids can be obtained from
commercial sources. In addition, corticosteroids can be obtained
through chemical synthesis. Examples of corticosteroids as well as
synthetic approaches for preparing corticosteroids are described in
the literature and in, for example, U.S. Pat. No. 2,403,683
(cortisone and others); U.S. Pat. No. 2,602,769 (hydrocortisone and
others); U.S. Pat. No. 2,897,216 (prednisone and others); U.S. Pat.
No. 2,837,464 (prednisolone and others); U.S. Pat. No. 2,897,218
(methylprednisolone and others); U.S. Pat. Nos. 2,789,118 and
3,031,347 (triamcinolone and others); U.S. Pat. No. 2,990,401
(triamcinolone acetonide and others); U.S. Pat. No. 3,007,923
(dexamethasone and others); U.S. Pat. Nos. 3,053,865 and 3,104,246
(betamethasone and others); U.S. Pat. No. 3,312,590 (beclomethasone
and others); U.S. Pat. No. 3,929,768 (budesonide and others); U.S.
Pat. No. 2,852,511 (fludrocortisone and others); U.S. Pat. No.
4,472,393 (mometasone and others); U.S. Pat. No. 4,335,121
(fluticasone and others); U.S. Pat. Nos. 4,076,708 and 4,124,707
(alclometasone and others); U.S. Pat. No. 3,729,495 (clocortolone
and others); U.S. Pat. No. 3,126,375 (flurandrenolide and others);
U.S. Pat. No. 3,124,571 (fluocinonide and others); U.S. Pat. No.
3,014,938 (fluocinonide acetonide and others); U.S. Pat. No.
2,602,769 (hydrocortisone and others); U.S. Pat. No. 3,038,914
(fluorometholone and others); U.S. Pat. No. 3,426,128
(diflucortolone and others); U.S. Pat. No. 3,892,857 (halcinonide
and others); and U.S. Pat. No. 3,721,687 (clobetasone and others).
In addition, salts and esters of a corticorsteroid can also be used
so long as the oligomer-containing compound retains at least some
degree of corticosteroid activity.
[0099] Each of these (and other) corticosteroids can be covalently
attached (either directly or through one or more atoms) to a
water-soluble and non-peptidic oligomer.
[0100] Exemplary molecular weights of small molecule drugs include
molecular weights of: less than about 950; less than about 900;
less than about 850; less than about 800; less than about 750; less
than about 700; less than about 650; less than about 600; less than
about 550; less than about 500; and less than about 450.
[0101] The small molecule drug used in the invention, if chiral,
may be obtained from a racemic mixture, or an optically active
form, for example, a single optically active enantiomer, or any
combination or ratio of enantiomers (i.e., scalemic mixture). In
addition, the small molecule drug may possess one or more geometric
isomers. With respect to geometric isomers, a composition can
comprise a single geometric isomer or a mixture of two or more
geometric isomers. A small molecule drug for use in the present
invention can be in its customary active form, or may possess some
degree of modification. For example, a small molecule drug may have
a targeting agent, tag, or transporter attached thereto, prior to
or after covalent attachment of an oligomer. Alternatively, the
small molecule drug may possess a lipophilic moiety attached
thereto, such as a phospholipid (e.g.,
distearoylphosphatidylethanolamine or "DSPE,"
dipalmitoylphosphatidylethanolamine or "DPPE," and so forth) or a
small fatty acid. In some instances, however, it is preferred that
the small molecule drug moiety does not include attachment to a
lipophilic moiety.
[0102] The corticosteroid for coupling to a water-soluble,
non-peptidic oligomer possesses a free hydroxyl, carboxyl, thio,
amino group, or the like (i.e., "handle") suitable for covalent
attachment to the oligomer. In addition, the corticosteroid can be
modified by introduction of a reactive group, preferably by
conversion of one of its existing functional groups to a functional
group suitable for formation of a stable covalent linkage between
the oligomer and the drug.
[0103] Accordingly, each oligomer is composed of up to three
different monomer types selected from the group consisting of:
alkylene oxide, such as ethylene oxide or propylene oxide; olefinic
alcohol, such as vinyl alcohol, 1-propenol or 2-propenol; vinyl
pyrrolidone; hydroxyalkyl methacrylamide or hydroxyalkyl
methacrylate, where alkyl is preferably methyl; .alpha.-hydroxy
acid, such as lactic acid or glycolic acid; phosphazene, oxazoline,
amino acids, carbohydrates such as monosaccharides, saccharide or
mannitol; and N-acryloylmorpholine. Preferred monomer types include
alkylene oxide, olefinic alcohol, hydroxyalkyl methacrylamide or
methacrylate, N-acryloylmorpholine, and .alpha.-hydroxy acid.
Preferably, each oligomer is, independently, a co-oligomer of two
monomer types selected from this group, or, more preferably, is a
homo-oligomer of one monomer type selected from this group.
[0104] The two monomer types in a co-oligomer may be of the same
monomer type, for example, two alkylene oxides, such as ethylene
oxide and propylene oxide. Preferably, the oligomer is a
homo-oligomer of ethylene oxide. Usually, although not necessarily,
the terminus (or termini) of the oligomer that is not covalently
attached to a small molecule is capped to render it unreactive.
Alternatively, the terminus may include a reactive group. When the
terminus is a reactive group, the reactive group is either selected
such that it is unreactive under the conditions of formation of the
final oligomer or during covalent attachment of the oligomer to a
small molecule drug, or it is protected as necessary. One common
end-functional group is hydroxyl or --OH, particularly for
oligoethylene oxides.
[0105] The water-soluble, non-peptidic oligomer (e.g., "POLY" in
various structures provided herein) can have any of a number of
different geometries. For example, the water-soluble, non-peptidic
oligomer can be linear, branched, or forked. Most typically, the
water-soluble, non-peptidic oligomer is linear or is branched, for
example, having one branch point. Although much of the discussion
herein is focused upon poly(ethylene oxide) as an illustrative
oligomer, the discussion and structures presented herein can be
readily extended to encompass any of the water-soluble,
non-peptidic oligomers described above.
[0106] The molecular weight of the water-soluble, non-peptidic
oligomer, excluding the linker portion, is generally relatively
low. Exemplary values of the molecular weight of the water-soluble
polymer include: below about 1500; below about 1450; below about
1400; below about 1350; below about 1300; below about 1250; below
about 1200; below about 1150; below about 1100; below about 1050;
below about 1000; below about 950; below about 900; below about
850; below about 800; below about 750; below about 700; below about
650; below about 600; below about 550; below about 500; below about
450; below about 400; below about 350; below about 300; below about
250; below about 200; and below about 100 Daltons.
[0107] Exemplary ranges of molecular weights of the water-soluble,
non-peptidic oligomer (excluding the linker) include: from about
100 to about 1400 Daltons; from about 100 to about 1200 Daltons;
from about 100 to about 800 Daltons; from about 100 to about 500
Daltons; from about 100 to about 400 Daltons; from about 200 to
about 500 Daltons; from about 200 to about 400 Daltons; from about
75 to 1000 Daltons; and from about 75 to about 750 Daltons.
[0108] Preferably, the number of monomers in the water-soluble,
non-peptidic oligomer falls within one or more of the following
ranges: between about 1 and about 30 (inclusive); between about 1
and about 25; between about 1 and about 20; between about 1 and
about 15; between about 1 and about 12; between about 1 and about
10. In certain instances, the number of monomers in series in the
oligomer (and the corresponding conjugate) is one of 1, 2, 3, 4, 5,
6, 7, or 8. In additional embodiments, the oligomer (and the
corresponding conjugate) contains 9, 10, 11, 12, 13, 14, 15, 16,
17, 18, 19, or 20 monomers. In yet further embodiments, the
oligomer (and the corresponding conjugate) possesses 21, 22, 23,
24, 25, 26, 27, 28, 29 or 30 monomers in series. Thus, for example,
when the water-soluble and non-peptidic polymer includes
CH.sub.3--(OCH.sub.2CH.sub.2).sub.n--, "n" is an integer that can
be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18,
19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 or 30, and can fall
within one or more of the following ranges: between about 1 and
about 25; between about 1 and about 20; between about 1 and about
15; between about 1 and about 12; between about 1 and about 10.
[0109] When the water-soluble, non-peptidic oligomer has 1, 2, 3,
4, 5, 6, 7, 8, 9, or 10 monomers, these values correspond to a
methoxy end-capped oligo(ethylene oxide) having a molecular weights
of about 75, 119, 163, 207, 251, 295, 339, 383, 427, and 471
Daltons, respectively. When the oligomer has 11, 12, 13, 14, or 15
monomers, these values correspond to methoxy end-capped
oligo(ethylene oxide) having molecular weights corresponding to
about 515, 559, 603, 647, and 691 Daltons, respectively.
[0110] When the water-soluble, non-peptidic oligomer is attached to
the corticosteroid (in contrast to the step-wise addition of one or
more monomers to effectively "grow" the oligomer onto the
corticosteroid), it is preferred that the composition containing an
activated form of the water-soluble, non-peptidic oligomer be
monodisperse. In those instances, however, where a bimodal
composition is employed, the composition will possess a bimodal
distribution centering around any two of the above numbers of
monomers. For instance, a bimodal oligomer may have any one of the
following exemplary combinations of monomer subunits: 1-2, 1-3,
1-4, 1-5, 1-6, 1-7, 1-8, 1-9, 1-10, and so forth; 2-3, 2-4, 2-5,
2-6, 2-7, 2-8, 2-9, 2-10, and so forth; 3-4, 3-5, 3-6, 3-7, 3-8,
3-9, 3-10, and so forth; 4-5, 4-6, 4-7, 4-8, 4-9, 4-10, and so
forth; 5-6, 5-7, 5-8, 5-9, 5-10, and so forth; 6-7, 6-8, 6-9, 6-10,
and so forth; 7-8, 7-9, 7-10, and so forth; and 8-9, 8-10, and so
forth.
[0111] In some instances, the composition containing an activated
form of the water-soluble, non-peptidic oligomer will be trimodal
or even tetramodal, possessing a range of monomers units as
previously described. Oligomer compositions possessing a
well-defined mixture of oligomers (i.e., being bimodal, trimodal,
tetramodal, and so forth) can be prepared by mixing purified
monodisperse oligomers to obtain a desired profile of oligomers (a
mixture of two oligomers differing only in the number of monomers
is bimodal; a mixture of three oligomers differing only in the
number of monomers is trimodal; a mixture of four oligomers
differing only in the number of monomers is tetramodal), or
alternatively, can be obtained from column chromatography of a
polydisperse oligomer by recovering the "center cut", to obtain a
mixture of oligomers in a desired and defined molecular weight
range.
[0112] It is preferred that the water-soluble, non-peptidic
oligomer is obtained from a composition that is preferably
unimolecular or monodisperse. That is, the oligomers in the
composition possess the same discrete molecular weight value rather
than a distribution of molecular weights. Some monodisperse
oligomers can be purchased from commercial sources such as those
available from Sigma-Aldrich, or alternatively, can be prepared
directly from commercially available starting materials such as
Sigma-Aldrich. Water-soluble, non-peptidic oligomers can be
prepared as described in Chen Y., Baker, G. L., J. Org. Chem.,
6870-6873 (1999), WO 02/098949, and U.S. Patent Application
Publication 2005/0136031.
[0113] When present, the spacer moiety (through which the
water-soluble, non-peptidic polymer is attached to the
corticosteroid) may be a single bond, a single atom, such as an
oxygen atom or a sulfur atom, two atoms, or a number of atoms. A
spacer moiety is typically but is not necessarily linear in nature.
The spacer moiety, "X," is hydrolytically stable, and is preferably
also enzymatically stable. Preferably, the spacer moiety "X" is one
having a chain length of less than about 12 atoms, and preferably
less than about 10 atoms, and even more preferably less than about
8 atoms and even more preferably less than about 5 atoms, whereby
length is meant the number of atoms in a single chain, not counting
substituents. For instance, a urea linkage such as this,
R.sub.oligomer--NH--(C.dbd.O)--NH--R.sub.drug, is considered to
have a chain length of 3 atoms (--NH--C(O)--NH--). In selected
embodiments, the linkage does not comprise further spacer
groups.
[0114] In some instances, the spacer moiety "X" comprises an ether,
amide, urethane, amine, thioether, urea, or a carbon-carbon bond.
Functional groups such as those discussed below, and illustrated in
the examples, are typically used for forming the linkages. The
spacer moiety may less preferably also comprise (or be adjacent to
or flanked by) other atoms, as described further below.
[0115] More specifically, in selected embodiments, a spacer moiety
of the invention, X, may be any of the following: "--" (i.e., a
covalent bond, that may be stable or degradable, between the
corticosteroid residue and the water-soluble, non-peptidic
oligomer), --O--, --NH--, --S--, --C(O)--, C(O)--NH, NH--C(O)--NH,
O--C(O)--NH, --OC(O)--NH--N.dbd., .dbd.N--NH--C(O)O--,
--C(O)--NH--N.dbd., .dbd.N--NH--C(O)--, --C(S)--, --CH.sub.2--,
--CH.sub.2--CH.sub.2--, --CH.sub.2--CH.sub.2--CH.sub.2--,
--CH.sub.2--CH.sub.2--CH.sub.2--CH.sub.2--, --O--CH.sub.2--,
--CH.sub.2--O--, --O--CH.sub.2--CH.sub.2--,
--CH.sub.2--O--CH.sub.2--, --CH.sub.2--CH.sub.2--O--,
--O--CH.sub.2--CH.sub.2--CH.sub.2--,
--CH.sub.2--O--CH.sub.2--CH.sub.2--,
--CH.sub.2--CH.sub.2--O--CH.sub.2--,
--CH.sub.2--CH.sub.2--CH.sub.2--O--,
--O--CH.sub.2--CH.sub.2--CH.sub.2--CH.sub.2--,
--CH.sub.2--O--CH.sub.2--CH.sub.2--CH.sub.2--,
--CH.sub.2--CH.sub.2--O--CH.sub.2--CH.sub.2--,
--CH.sub.2--CH.sub.2--CH.sub.2--O--CH.sub.2--,
--CH.sub.2--CH.sub.2--CH.sub.2--CH.sub.2--O--,
--C(O)--NH--CH.sub.2--, --C(O)--NH--CH.sub.2--CH.sub.2--,
--CH.sub.2--C(O)--NH--CH.sub.2--, --CH.sub.2--CH.sub.2--C(O)--NH--,
--C(O)--NH--CH.sub.2--CH.sub.2--CH.sub.2--,
--CH.sub.2--C(O)--NH--CH.sub.2--CH.sub.2--,
--CH.sub.2--CH.sub.2--C(O)--NH--CH.sub.2--,
--CH.sub.2--CH.sub.2--CH.sub.2--C(O)--NH--,
--C(O)--NH--CH.sub.2--CH.sub.2--CH.sub.2--CH.sub.2--,
--CH.sub.2--C(O)--NH--CH.sub.2--CH.sub.2--CH.sub.2--,
--CH.sub.2--CH.sub.2--C(O)--NH--CH.sub.2--CH.sub.2--,
--CH.sub.2--CH.sub.2--CH.sub.2--C(O)--NH--CH.sub.2--,
--CH.sub.2--CH.sub.2--CH.sub.2--C(O)--NH--CH.sub.2--CH.sub.2--,
--CH.sub.2--CH.sub.2--CH.sub.2--CH.sub.2--C(O)--NH--,
--NH--C(O)--CH.sub.2--, --CH.sub.2--NH--C(O)--CH.sub.2--,
--CH.sub.2--CH.sub.2--NH--C(O)--CH.sub.2--,
--NH--C(O)--CH.sub.2--CH.sub.2--,
--CH.sub.2--NH--C(O)--CH.sub.2--CH.sub.2,
--CH.sub.2--CH.sub.2--NH--C(O)--CH.sub.2--CH.sub.2,
--C(O)--NH--CH.sub.2--, --C(O)--NH--CH.sub.2--CH.sub.2--,
--O--C(O)--NH--CH.sub.2--, --O--C(O)--NH--CH.sub.2--CH.sub.2--,
--NH--CH.sub.2--, --NH--CH.sub.2--CH.sub.2--,
--CH.sub.2--NH--CH.sub.2--, --CH.sub.2--CH.sub.2--NH--CH.sub.2--,
--C(O)--CH.sub.2--, --C(O)--CH.sub.2--CH.sub.2--,
--CH.sub.2--C(O)--CH.sub.2--,
--CH.sub.2--CH.sub.2--C(O)--CH.sub.2--,
--CH.sub.2--CH.sub.2--C(O)--CH.sub.2--CH.sub.2--,
--CH.sub.2--CH.sub.2--C(O)--,
--CH.sub.2--CH.sub.2--CH.sub.2--C(O)--NH--CH.sub.2--CH.sub.2--NH--,
--CH.sub.2--CH.sub.2--CH.sub.2--C(O)--NH--CH.sub.2--CH.sub.2--NH--C(O)--,
--CH.sub.2--CH.sub.2--CH.sub.2--C(O)--NH--CH.sub.2--CH.sub.2--NH--C(O)--C-
H.sub.2--, bivalent cycloalkyl group, --N(R.sup.6)--, R.sup.6 is H
or an organic radical selected from the group consisting of alkyl,
substituted alkyl, alkenyl, substituted alkenyl, alkynyl,
substituted alkynyl, aryl and substituted aryl.
[0116] For purposes of the present invention, however, a group of
atoms is not considered a linkage when it is immediately adjacent
to an oligomer segment, and the group of atoms is the same as a
monomer of the oligomer such that the group would represent a mere
extension of the oligomer chain.
[0117] The linkage "X" between the water-soluble, non-peptidic
oligomer and the small molecule is typically formed by reaction of
a functional group on a terminus of the oligomer (or nascent
oligomer when it is desired to "grow" the oligomer onto the
corticosteroid) with a corresponding functional group within the
corticosteroid. Illustrative reactions are described briefly below.
For example, an amino group on an oligomer may be reacted with a
carboxylic acid or an activated carboxylic acid derivative on the
small molecule, or vice versa, to produce an amide linkage.
Alternatively, reaction of an amine on an oligomer with an
activated carbonate (e.g. succinimidyl or benzotriazyl carbonate)
on the drug, or vice versa, forms a carbamate linkage. Reaction of
an amine on an oligomer with an isocyanate (R--N.dbd.C.dbd.O) on a
drug, or vice versa, forms a urea linkage
(R--NH--(C.dbd.O)--NH--R'). Further, reaction of an alcohol
(alkoxide) group on an oligomer with an alkyl halide, or halide
group within a drug, or vice versa, forms an ether linkage. In yet
another coupling approach, a small molecule having an aldehyde
function is coupled to an oligomer amino group by reductive
amination, resulting in formation of a secondary amine linkage
between the oligomer and the small molecule.
[0118] A particularly preferred water-soluble, non-peptidic
oligomer is an oligomer bearing an aldehyde functional group. In
this regard, the oligomer will have the following structure:
CH.sub.3O--(CH.sub.2--CH.sub.2--O).sub.n--(CH.sub.2).sub.p--C(O)H,
wherein (n) is one of 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10 and (p) is
one of 1, 2, 3, 4, 5, 6 and 7. Preferred (n) values include 3, 5
and 7 and preferred (p) values 2, 3 and 4.
[0119] The terminus of the water-soluble, non-peptidic oligomer not
bearing a functional group is capped to render it unreactive. When
the oligomer includes a further functional group at a terminus
other than that intended for formation of a conjugate, that group
is either selected such that it is unreactive under the conditions
of formation of the linkage "X," or it is protected during the
formation of the linkage "X."
[0120] As stated above, the water-soluble, non-peptidic oligomer
includes at least one functional group prior to conjugation. The
functional group typically comprises an electrophilic or
nucleophilic group for covalent attachment to a small molecule,
depending upon the reactive group contained within or introduced
into the small molecule. Examples of nucleophilic groups that may
be present in either the oligomer or the small molecule include
hydroxyl, amine, hydrazine (--NHNH.sub.2), hydrazide
(--C(O)NHNH.sub.2), and thiol. Preferred nucleophiles include
amine, hydrazine, hydrazide, and thiol, particularly amine. Most
small molecule drugs for covalent attachment to an oligomer will
possess a free hydroxyl, amino, thio, aldehyde, ketone, or carboxyl
group.
[0121] Examples of electrophilic functional groups that may be
present in either the oligomer or the small molecule include
carboxylic acid, carboxylic ester, particularly imide esters,
orthoester, carbonate, isocyanate, isothiocyanate, aldehyde,
ketone, thione, alkenyl, acrylate, methacrylate, acrylamide,
sulfone, maleimide, disulfide, iodo, epoxy, sulfonate,
thiosulfonate, silane, alkoxysilane, and halosilane. More specific
examples of these groups include succinimidyl ester or carbonate,
imidazoyl ester or carbonate, benzotriazole ester or carbonate,
vinyl sulfone, chloroethylsulfone, vinylpyridine, pyridyl
disulfide, iodoacetamide, glyoxal, dione, mesylate, tosylate, and
tresylate (2,2,2-trifluoroethanesulfonate).
[0122] Also included are sulfur analogs of several of these groups,
such as thione, thione hydrate, thioketal, is 2-thiazolidine
thione, etc., as well as hydrates or protected derivatives of any
of the above moieties (e.g. aldehyde hydrate, hemiacetal, acetal,
ketone hydrate, hemiketal, ketal, thioketal, thioacetal).
[0123] An "activated derivative" of a carboxylic acid refers to a
carboxylic acid derivative that reacts readily with nucleophiles,
generally much more readily than the underivatized carboxylic acid.
Activated carboxylic acids include, for example, acid halides (such
as acid chlorides), anhydrides, carbonates, and esters. Such esters
include imide esters, of the general form --(CO)O--N[(CO)--].sub.2;
for example, N-hydroxysuccinimidyl (NHS) esters or
N-hydroxyphthalimidyl esters. Also preferred are imidazolyl esters
and benzotriazole esters. Particularly preferred are activated
propionic acid or butanoic acid esters, as described in co-owned
U.S. Pat. No. 5,672,662. These include groups of the form
--(CH.sub.2).sub.2-3C(.dbd.O)O-Q, where Q is preferably selected
from N-succinimide, N-sulfosuccinimide, N-phthalimide,
N-glutarimide, N-tetrahydrophthalimide,
N-norbornene-2,3-dicarboximide, benzotriazole, 7-azabenzotriazole,
and imidazole.
[0124] Other preferred electrophilic groups include succinimidyl
carbonate, maleimide, benzotriazole carbonate, glycidyl ether,
imidazoyl carbonate, p-nitrophenyl carbonate, acrylate, tresylate,
aldehyde, and orthopyridyl disulfide.
[0125] These electrophilic groups are subject to reaction with
nucleophiles, e.g., hydroxy, thio, or amino groups, to produce
various bond types. Preferred for the present invention are
reactions which favor formation of a hydrolytically stable linkage.
For example, carboxylic acids and activated derivatives thereof,
which include orthoesters, succinimidyl esters, imidazolyl esters,
and benzotriazole esters, react with the above types of
nucleophiles to form esters, thioesters, and amides, respectively,
of which amides are the most hydrolytically stable. Carbonates,
including succinimidyl, imidazolyl, and benzotriazole carbonates,
react with amino groups to form carbamates. Isocyanates
(R--N.dbd.C.dbd.O) react with hydroxyl or amino groups to form,
respectively, carbamate (RNH--C(O)--OR') or urea (RNH--C(O)--NHR')
linkages. Aldehydes, ketones, glyoxals, diones and their hydrates
or alcohol adducts (i.e., aldehyde hydrate, hemiacetal, acetal,
ketone hydrate, hemiketal, and ketal) are preferably reacted with
amines, followed by reduction of the resulting imine, if desired,
to provide an amine linkage (reductive amination).
[0126] Several of the electrophilic functional groups include
electrophilic double bonds to which nucleophilic groups, such as
thiols, can be added, to form, for example, thioether bonds. These
groups include maleimides, vinyl sulfones, vinyl pyridine,
acrylates, methacrylates, and acrylamides. Other groups comprise
leaving groups that can be displaced by a nucleophile; these
include chloroethyl sulfone, pyridyl disulfides (which include a
cleavable S--S bond), iodoacetamide, mesylate, tosylate,
thiosulfonate, and tresylate. Epoxides react by ring opening by a
nucleophile, to form, for example, an ether or amine bond.
Reactions involving complementary reactive groups such as those
noted above on the oligomer and the small molecule are utilized to
prepare the conjugates of the invention.
[0127] In some instances the corticosteroid may not have a
functional group suited for conjugation. In this instance, it is
possible to modify (or "functionalize") the "original"
corticosteroid so that it does have a functional group suited for
conjugation. For example, if the corticosteroid has an amide group,
but an amine group is desired, it is possible to modify the amide
group to an amine group by way of a Hofmann rearrangement, Curtius
rearrangement (once the amide is converted to an azide) or Lossen
rearrangement (once amide is concerted to hydroxamide followed by
treatment with tolyene-2-sulfonyl chloride/base).
[0128] It is possible to prepare a conjugate of small molecule
corticosteroid bearing a carboxyl group wherein the carboxyl
group-bearing small molecule corticosteroid is coupled to an
amino-terminated oligomeric ethylene glycol, to provide a conjugate
having an amide group covalently linking the small molecule
corticosteroid to the oligomer. This can be performed, for example,
by combining the carboxyl group-bearing small molecule
corticosteroid with the amino-terminated oligomeric ethylene glycol
in the presence of a coupling reagent, (such as
dicyclohexylcarbodiimide or "DCC") in an anhydrous organic
solvent.
[0129] Further, it is possible to prepare a conjugate of a small
molecule corticosteroid bearing a hydroxyl group wherein the
hydroxyl group-bearing small molecule corticosteroid is coupled to
an oligomeric ethylene glycol halide to result in an ether (--O--)
linked small molecule conjugate. This can be performed, for
example, by using sodium hydride to deprotonate the hydroxyl group
followed by reaction with a halide-terminated oligomeric ethylene
glycol.
[0130] In another example, it is possible to prepare a conjugate of
a small molecule corticosteroid bearing a ketone group by first
reducing the ketone group to form the corresponding hydroxyl group.
Thereafter, the small molecule corticosteroid now bearing a
hydroxyl group can be coupled as described herein.
[0131] In still another example, it is possible to prepare a
conjugate of a small molecule corticosteroid bearing a carbonyl
group by using hydrazono-de-oxo-substitution. In one approach, a
carbonyl group-bearing small molecule corticosteroid (such as a
ketone group-bearing corticosteroid) and a hydrazine-bearing
oligomer are dissolved in a suitable buffer and allowed to react,
thereby forming a hydrazone-containing linkage between the
corticosteroid residue and the oligomer.
[0132] In still another instance, it is possible to prepare a
conjugate of a small molecule corticosteroid bearing an amine
group. In one approach, the amine group-bearing small molecule
corticosteroid and an aldehyde-bearing oligomer are dissolved in a
suitable buffer after which a suitable reducing agent (e.g.,
NaCNBH.sub.3) is added. Following reduction, the result is an amine
linkage formed between the amine group of the amine
group-containing small molecule corticosteroid and the carbonyl
carbon of the aldehyde-bearing oligomer.
[0133] In another approach for preparing a conjugate of a small
molecule corticosteroid bearing an amine group, a carboxylic
acid-bearing oligomer and the amine group-bearing small molecule
corticosteroid are combined, typically in the presence of a
coupling reagent (e.g., DCC). The result is an amide linkage formed
between the amine group of the amine group-containing small
molecule corticosteroid and the carbonyl of the carboxylic
acid-bearing oligomer.
[0134] An exemplary conjugate of the invention is provided below
having the following structure:
##STR00015##
wherein:
[0135] the dashed line represents an optional double bond;
[0136] R.sup.1 is selected from the group consisting of halo and
alkyl;
[0137] either [0138] R.sup.2 is selected from the group consisting
of hydroxy and alkyl and R.sup.3 is selected from the group
consisting of hydroxy, alkyl, --OC(O)-alkyl, and --OC(O)-cyclo, or
[0139] R.sup.2 and R.sup.3 combine to form a moiety selected from
the group consisting of
##STR00016##
[0140] R.sup.4 is selected from the group consisting of --CH.sub.3,
--CH.sub.2--OH, --CH.sub.2-halo, --S--CH.sub.2-halo,
--CH.sub.2--O--C(O)--CH.sub.3,
--CH.sub.2--O--C(O)--CH.sub.2--CH.sub.3, --CH.sub.2--PO.sub.4,
--CH.sub.2--O--C(O)--C(CH.sub.3).sub.3,
--CH.sub.2--O--C(O)--CH.sub.2--CH.sub.2--CH.sub.2--CH.sub.3,
--CH.sub.2--C(O)--O--CH.sub.3,
--CH.sub.2--O--C(O)--CH.sub.2--CH.sub.2--C(O)--OH;
[0141] either [0142] R.sup.3 is --H and R.sup.6 is selected from
the group consisting of --H and hydroxy, or [0143] R.sup.5 and
R.sup.6 combine to form carbonyl; R.sup.7 is halo;
[0144] X is a spacer moiety; and
[0145] POLY is a water-soluble, non-peptidic oligomer.
[0146] First, an oligomer obtained from a monodisperse or bimodal
water soluble oligomer is conjugated to the small molecule drug.
Preferably, the drug is orally bioavailable, and on its own,
exhibits a non-negligible blood-brain barrier crossing rate. Next,
the ability of the conjugate to cross the blood-brain barrier is
determined using an appropriate model and compared to that of the
unmodified parent drug. If the results are favorable, that is to
say, if, for example, the rate of crossing is significantly
reduced, then the bioactivity of conjugate is further evaluated.
Preferably, the compounds according to the invention maintain a
significant degree of bioactivity relative to the parent drug,
i.e., greater than about 30% of the bioactivity of the parent drug,
or even more preferably, greater than about 50% of the bioactivity
of the parent drug.
[0147] The above steps are repeated one or more times using
oligomers of the same monomer type but having a different number of
subunits and the results compared.
[0148] For each conjugate whose ability to cross the blood-brain
barrier is reduced in comparison to the non-conjugated small
molecule drug, its oral bioavailability is then assessed. Based
upon these results, that is to say, based upon the comparison of
conjugates of oligomers of varying size to a given small molecule
at a given position or location within the small molecule, it is
possible to determine the size of the oligomer most effective in
providing a conjugate having an optimal balance between reduction
in biological membrane crossing, oral bioavailability, and
bioactivity. The small size of the oligomers makes such screenings
feasible and allows one to effectively tailor the properties of the
resulting conjugate. By making small, incremental changes in
oligomer size and utilizing an experimental design approach, one
can effectively identify a conjugate having a favorable balance of
reduction in biological membrane crossing rate, bioactivity, and
oral bioavailability. In some instances, attachment of an oligomer
as described herein is effective to actually increase oral
bioavailability of the drug.
[0149] For example, one of ordinary skill in the art, using routine
experimentation, can determine a best suited molecular size and
linkage for improving oral bioavailability by first preparing a
series of oligomers with different weights and functional groups
and then obtaining the necessary clearance profiles by
administering the conjugates to a patient and taking periodic blood
and/or urine sampling. Once a series of clearance profiles have
been obtained for each tested conjugate, a suitable conjugate can
be identified.
[0150] Animal models (rodents and dogs) can also be used to study
oral drug transport. In addition, non-in vivo methods include
rodent everted gut excised tissue and Caco-2 cell monolayer
tissue-culture models. These models are useful in predicting oral
drug bioavailability.
[0151] To determine whether the corticosteroid or the conjugate of
a corticosteroid and a water-soluble non-peptidic polymer has
activity as a corticosteroid, it is possible to test such a
compound. Such methods are known to those of ordinary skill in the
art and described herein.
[0152] The present invention also includes pharmaceutical
preparations comprising a conjugate as provided herein in
combination with a pharmaceutical excipient. Generally, the
conjugate itself will be in a solid form (e.g., a precipitate),
which can be combined with a suitable pharmaceutical excipient that
can be in either solid or liquid form.
[0153] Exemplary excipients include, without limitation, those
selected from the group consisting of carbohydrates, inorganic
salts, antimicrobial agents, antioxidants, surfactants, buffers,
acids, bases, and combinations thereof.
[0154] A carbohydrate such as a sugar, a derivatized sugar such as
an alditol, aldonic acid, an esterified sugar, and/or a sugar
polymer may be present as an excipient. Specific carbohydrate
excipients include, for example: monosaccharides, such as fructose,
maltose, galactose, glucose, D-mannose, sorbose, and the like;
disaccharides, such as lactose, sucrose, trehalose, cellobiose, and
the like; polysaccharides, such as raffinose, melezitose,
maltodextrins, dextrans, starches, and the like; and alditols, such
as mannitol, xylitol, maltitol, lactitol, xylitol, sorbitol
(glucitol), pyranosyl sorbitol, myoinositol, and the like.
[0155] The excipient can also include an inorganic salt or buffer
such as citric acid, sodium chloride, potassium chloride, sodium
sulfate, potassium nitrate, sodium phosphate monobasic, sodium
phosphate dibasic, and combinations thereof.
[0156] The preparation may also include an antimicrobial agent for
preventing or deterring microbial growth. Nonlimiting examples of
antimicrobial agents suitable for the present invention include
benzalkonium chloride, benzethonium chloride, benzyl alcohol,
cetylpyridinium chloride, chlorobutanol, phenol, phenylethyl
alcohol, phenylmercuric nitrate, thimersol, and combinations
thereof.
[0157] An antioxidant can be present in the preparation as well.
Antioxidants are used to prevent oxidation, thereby preventing the
deterioration of the conjugate or other components of the
preparation. Suitable antioxidants for use in the present invention
include, for example, ascorbyl palmitate, butylated hydroxyanisole,
butylated hydroxytoluene, hypophosphorous acid, monothioglycerol,
propyl gallate, sodium bisulfite, sodium formaldehyde sulfoxylate,
sodium metabisulfite, and combinations thereof.
[0158] A surfactant may be present as an excipient. Exemplary
surfactants include: polysorbates, such as "Tween 20" and "Tween
80," and pluronics such as F68 and F88 (both of which are available
from BASF, Mount Olive, N.J.); sorbitan esters; lipids, such as
phospholipids such as lecithin and other phosphatidylcholines,
phosphatidylethanolamines (although preferably not in liposomal
form), fatty acids and fatty esters; steroids, such as cholesterol;
and chelating agents, such as EDTA, zinc and other such suitable
cations.
[0159] Pharmaceutically acceptable acids or bases may be present as
an excipient in the preparation. Nonlimiting examples of acids that
can be used include those acids selected from the group consisting
of hydrochloric acid, acetic acid, phosphoric acid, citric acid,
malic acid, lactic acid, formic acid, trichloroacetic acid, nitric
acid, perchloric acid, phosphoric acid, sulfuric acid, fumaric
acid, and combinations thereof. Examples of suitable bases include,
without limitation, bases selected from the group consisting of
sodium hydroxide, sodium acetate, ammonium hydroxide, potassium
hydroxide, ammonium acetate, potassium acetate, sodium phosphate,
potassium phosphate, sodium citrate, sodium formate, sodium
sulfate, potassium sulfate, potassium fumerate, and combinations
thereof.
[0160] The amount of the conjugate in the composition will vary
depending on a number of factors, but will optimally be a
therapeutically effective dose when the composition is stored in a
unit dose container. A therapeutically effective dose can be
determined experimentally by repeated administration of increasing
amounts of the conjugate in order to determine which amount
produces a clinically desired endpoint.
[0161] The amount of any individual excipient in the composition
will vary depending on the activity of the excipient and particular
needs of the composition. Typically, the optimal amount of any
individual excipient is determined through routine experimentation,
i.e., by preparing compositions containing varying amounts of the
excipient (ranging from low to high), examining the stability and
other parameters, and then determining the range at which optimal
performance is attained with no significant adverse effects.
[0162] Generally, however, excipients will be present in the
composition in an amount of about 1% to about 99% by weight,
preferably from about 5%-98% by weight, more preferably from about
15-95% by weight of the excipient, with concentrations less than
30% by weight most preferred.
[0163] These foregoing pharmaceutical excipients along with other
excipients and general teachings regarding pharmaceutical
compositions are described in "Remington: The Science &
Practice of Pharmacy", 19.sup.th ed., Williams & Williams,
(1995), the "Physician's Desk Reference", 52.sup.thi ed., Medical
Economics, Montvale, N.J. (1998), and Kibbe, A. H., Handbook of
Pharmaceutical Excipients, 3.sup.rd Edition, American
Pharmaceutical Association, Washington, D.C., 2000.
[0164] The pharmaceutical compositions can take any number of forms
and the invention is not limited in this regard. Exemplary
preparations are most preferably in a form suitable for oral
administration such as a tablet, caplet, capsule, gel cap, troche,
dispersion, suspension, solution, elixir, syrup, lozenge,
transdermal patch, spray, suppository, and powder.
[0165] Oral dosage forms are preferred for those conjugates that
are orally active, and include tablets, caplets, capsules, gel
caps, suspensions, solutions, elixirs, and syrups, and can also
comprise a plurality of granules, beads, powders or pellets that
are optionally encapsulated. Such dosage forms are prepared using
conventional methods known to those in the field of pharmaceutical
formulation and described in the pertinent texts.
[0166] Tablets and caplets, for example, can be manufactured using
standard tablet processing procedures and equipment. Direct
compression and granulation techniques are preferred when preparing
tablets or caplets containing the conjugates described herein. In
addition to the conjugate, the tablets and caplets will generally
contain inactive, pharmaceutically acceptable carrier materials
such as binders, lubricants, disintegrants, fillers, stabilizers,
surfactants, coloring agents, flow agents, and the like. Binders
are used to impart cohesive qualities to a tablet, and thus ensure
that the tablet remains intact. Suitable binder materials include,
but are not limited to, starch (including corn starch and
pregelatinized starch), gelatin, sugars (including sucrose,
glucose, dextrose and lactose), polyethylene glycol, waxes, and
natural and synthetic gums, e.g., acacia sodium alginate,
polyvinylpyrrolidone, cellulosic polymers (including hydroxypropyl
cellulose, hydroxypropyl methylcellulose, methyl cellulose,
microcrystalline cellulose, ethyl cellulose, hydroxyethyl
cellulose, and the like), and Veegum. Lubricants are used to
facilitate tablet manufacture, promoting powder flow and preventing
particle capping (i.e., particle breakage) when pressure is
relieved. Useful lubricants are magnesium stearate, calcium
stearate, and stearic acid. Disintegrants are used to facilitate
disintegration of the tablet, and are generally starches, clays,
celluloses, algins, gums, or crosslinked polymers. Fillers include,
for example, materials such as silicon dioxide, titanium dioxide,
alumina, talc, kaolin, powdered cellulose, and microcrystalline
cellulose, as well as soluble materials such as mannitol, urea,
sucrose, lactose, dextrose, sodium chloride, and sorbitol.
Stabilizers, as well known in the art, are used to inhibit or
retard drug decomposition reactions that include, by way of
example, oxidative reactions.
[0167] Capsules are also preferred oral dosage forms, in which case
the conjugate-containing composition can be encapsulated in the
form of a liquid or gel (e.g., in the case of a gel cap) or solid
(including particulates such as granules, beads, powders or
pellets). Suitable capsules include hard and soft capsules, and are
generally made of gelatin, starch, or a cellulosic material.
Two-piece hard gelatin capsules are preferably sealed, such as with
gelatin bands or the like.
[0168] Included are parenteral formulations in the substantially
dry form (typically as a lyophilizate or precipitate, which can be
in the form of a powder or cake), as well as formulations prepared
for injection, which are typically liquid and requires the step of
reconstituting the dry form of parenteral formulation. Examples of
suitable diluents for reconstituting solid compositions prior to
injection include bacteriostatic water for injection, dextrose 5%
in water, phosphate-buffered saline, Ringer's solution, saline,
sterile water, deionized water, and combinations thereof.
[0169] In some cases, compositions intended for parenteral
administration can take the form of nonaqueous solutions,
suspensions, or emulsions, each typically being sterile. Examples
of nonaqueous 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.
[0170] The parenteral formulations described herein can also
contain adjuvants such as preserving, wetting, emulsifying, and
dispersing agents. The formulations are rendered sterile by
incorporation of a sterilizing agent, filtration through a
bacteria-retaining filter, irradiation, or heat.
[0171] The conjugate can also be administered through the skin
using conventional transdermal patch or other transdermal delivery
system, wherein the conjugate is contained within a laminated
structure that serves as a drug delivery device to be affixed to
the skin. In such a structure, the conjugate is contained in a
layer, or "reservoir," underlying an upper backing layer. The
laminated structure can contain a single reservoir, or it can
contain multiple reservoirs.
[0172] The conjugate can also be formulated into a suppository for
rectal administration. With respect to suppositories, the conjugate
is mixed with a suppository base material which is (e.g., an
excipient that remains solid at room temperature but softens, melts
or dissolves at body temperature) such as coca butter (theobroma
oil), polyethylene glycols, glycerinated gelatin, fatty acids, and
combinations thereof. Suppositories can be prepared by, for
example, performing the following steps (not necessarily in the
order presented): melting the suppository base material to form a
melt; incorporating the conjugate (either before or after melting
of the suppository base material); pouring the melt into a mold;
cooling the melt (e.g., placing the melt-containing mold in a room
temperature environment) to thereby form suppositories; and
removing the suppositories from the mold.
[0173] The invention also provides a method for administering a
conjugate as provided herein to a patient suffering from a
condition that is responsive to treatment with the conjugate. The
method comprises administering, generally orally, a therapeutically
effective amount of the conjugate (preferably provided as part of a
pharmaceutical preparation). Other modes of administration are also
contemplated, such as pulmonary, nasal, buccal, rectal, sublingual,
transdermal, and parenteral. As used herein, the term "parenteral"
includes subcutaneous, intravenous, intra-arterial,
intraperitoneal, intracardiac, intrathecal, and intramuscular
injection, as well as infusion injections.
[0174] In instances where parenteral administration is utilized, it
may be necessary to employ somewhat bigger oligomers than those
described previously, with molecular weights ranging from about 500
to 30K Daltons (e.g., having molecular weights of about 500, 1000,
2000, 2500, 3000, 5000, 7500, 10000, 15000, 20000, 25000, 30000 or
even more).
[0175] The method of administering may be used to treat any
condition that can be remedied or prevented by administration of
the particular conjugate. Those of ordinary skill in the art
appreciate which conditions a specific conjugate can effectively
treat. The actual dose to be administered will vary depend upon the
age, weight, and general condition of the subject as well as the
severity of the condition being treated, the judgment of the health
care professional, and conjugate being administered.
Therapeutically effective amounts are known to those skilled in the
art and/or are described in the pertinent reference texts and
literature. Generally, a therapeutically effective amount will
range from about 0.001 mg to 1000 mg, preferably in doses from 0.01
mg/day to 750 mg/day, and more preferably in doses from 0.10 mg/day
to 500 mg/day.
[0176] The unit dosage of any given conjugate (again, preferably
provided as part of a pharmaceutical preparation) can be
administered in a variety of dosing schedules depending on the
judgment of the clinician, needs of the patient, and so forth. The
specific dosing schedule will be known by those of ordinary skill
in the art or can be determined experimentally using routine
methods. Exemplary dosing schedules include, without limitation,
administration five times a day, four times a day, three times a
day, twice daily, once daily, three times weekly, twice weekly,
once weekly, twice monthly, once monthly, and any combination
thereof. Once the clinical endpoint has been achieved, dosing of
the composition is halted.
[0177] One advantage of administering the conjugates of the present
invention is that a reduction in first pass metabolism may be
achieved relative to the parent drug. Such a result is advantageous
for many orally administered drugs that are substantially
metabolized by passage through the gut. In this way, clearance of
the conjugate can be modulated by selecting the oligomer molecular
size, linkage, and position of covalent attachment providing the
desired clearance properties. One of ordinary skill in the art can
determine the ideal molecular size of the oligomer based upon the
teachings herein. Preferred reductions in first pass metabolism for
a conjugate as compared to the corresponding nonconjugated small
drug molecule include: at least about 10%, at least about 20%, at
least about 30; at least about 40; at least about 50%; at least
about 60%, at least about 70%, at least about 80% and at least
about 90%.
[0178] Thus, the invention provides a method for reducing the
metabolism of an active agent. The method comprises the steps of:
providing monodisperse or bimodal conjugates, each conjugate
comprised of a moiety derived from a small molecule drug covalently
attached by a stable linkage to a water-soluble oligomer, wherein
said conjugate exhibits a reduced rate of metabolism as compared to
the rate of metabolism of the small molecule drug not attached to
the water-soluble oligomer; and administering the conjugate to a
patient. Typically, administration is carried out via one type of
administration selected from the group consisting of oral
administration, transdermal administration, buccal administration,
transmucosal administration, vaginal administration, rectal
administration, parenteral administration, and pulmonary
administration.
[0179] Although useful in reducing many types of metabolism
(including both Phase I and Phase II metabolism) can be reduced,
the conjugates are particularly useful when the small molecule drug
is metabolized by a hepatic enzyme (e.g., one or more of the
cytochrome P450 isoforms) and/or by one or more intestinal
enzymes.
[0180] All articles, books, patents, patent publications and other
publications referenced herein are incorporated by reference in
their entireties.
EXPERIMENTAL
[0181] It is to be understood that while the invention has been
described in conjunction with certain preferred and specific
embodiments, the foregoing description as well as the examples that
follow are intended to illustrate and not limit the scope of the
invention. Other aspects, advantages and modifications within the
scope of the invention will be apparent to those skilled in the art
to which the invention pertains.
[0182] All chemical reagents referred to in the appended examples
are commercially available unless otherwise indicated. The
preparation of PEG-mers is described in, for example, U.S. Patent
Application Publication No. 2005/0136031.
[0183] All .sup.1H NMR (nuclear magnetic resonance) data was
generated by an NMR spectrometer manufactured by Bruker. A list of
certain compounds as well as the source of the compounds is
provided below.
Example 1
Preparation of Hydrazine-Bearing Oligomers
[0184] Hydrazine-bearing oligomers (a type of oligomeric reagent)
were prepared following the schematic provided below.
##STR00017##
[0185] CH.sub.3--(OCH.sub.2CH.sub.2).sub.n--OH (1.0 mmol) and DMAP
(1.5 mmol) were dissolved in 20 ml DCM to form a solution. To the
solution, 4-nitrophenyl chloformate (1.0 mmol) was added. The
reaction mixture was stirred overnight at room temperature. t-Butyl
carbazate (2.0 mmol) was added into the mixture which was then
stirred for additional 24 hours at room temperature. DCM (150 ml)
was added into the mixture and the DCM phase was washed with water
(150 ml.times.2) and then dried. The crude product was deprotected
by DCM/TFA (2:1). The solvent and TFA were removed, and the residue
was dissolved in 200 ml DCM, which was washed with 5%
Na.sub.2CO.sub.3 and water. After removing solvent and drying, the
product (a hydrazine-bearing oligomer reagent) was obtained as an
oil, which could be used in a coupling reaction.
[0186] Using this approach, hydrazine-bearing oligomeric reagents
wherein n is 3, 7 and 8 were made.
Example 2
Coupling Reaction
[0187] Using hydrazine-bearing oligomers prepared in accordance
with Example 1, conjugates were prepared following the schematic
below.
##STR00018##
[0188] The corticosteroid, cortisone, (1.0 mmol) and a
hydrazine-bearing oligomer prepared in accordance with Example 1,
(1.5 mmol) were dissolved in 10 ml CH.sub.3OH to form a solution.
To the solution, 5 drops of acetic acid were added. The reaction
mixture was stirred overnight at room temperature. DCM (150 ml) was
added into the mixture. The DCM phase was washed with 1%
Na.sub.2CO.sub.3 and then with water (150 ml.times.2). After dried
and removing the solvent, the crude product was purified by silicon
gel column (DCM:MeOH, 20:1). The products were obtained as solid or
sticky oil (yield: .about.70-90%, purity: 92-99%).
[0189] To conjugate dexamethasone, the same process is generally
followed except that dexamethasone is used in place of cortisone
and the reaction is run at reflux in methanol for three days.
[0190] Using this approach, hydrazine-bearing oligomeric reagents
wherein n was 3 was made for hydrocortisone
("mPEG.sub.3-Hydrocortisone") and dexamethasone
("mPEG.sub.3-Dexamethasone"), wherein n was 7 was made for
hydrocortisone ("mPEG.sub.7-Hydrocortisone"), cortisone
("mPEG.sub.7-Cortisone") and dexamethasone
("mPEG.sub.7-Dexamethasone"), and wherein n was 8 was made for
hydrocortisone ("mPEG.sub.8-Hydrocortisone"), cortisone
("mPEG.sub.8-Cortisone") and dexamethasone
("mPEG.sub.8-Dexamethasone").
Example 3
Hydrolysis Testing
[0191] mPEG.sub.7-Cortisone prepared in accordance with Example 2
(n in the oligomer equal to seven) were tested for hydrolysis at pH
5.5 and 7.4. The drug was stable and the conjugate was able to
release cortisone clearly at pH 5.5. The cortisone release from the
compound at pH 7.4 is much slower than that at pH 5.5. However,
many decomposed impurities from cortisone were observed with
extended time at pH 7.4. Hydrocortisone is much more stable than
cortisone in PBS buffer at pH 7.4.
[0192] A graph of the results is provided in FIG. 1.
Example 4
Glucocorticoid Binding Assay
[0193] The assay was used to determine whether the tested compounds
bound to the glucocorticoid binding site and is based on procedures
set forth in the literature. See, for example, Da Han et al. (1994)
Neurochem. Int. 24:339-348. Briefly, using competitive binding of
with the radioligand "[6,7-.sup.3H]triamcinolone acetonide" (30-50
Cl/mmol), reactions were carried out in 50 mM KH.sub.2PO.sub.4 (pH
7.4) containing 10 mM sodium molybdate and 10 mM
.alpha.-monothioglycerol at 0.degree. C. for 16 hours. The
glucocorticoid receptors were obtained from rat brains. The
reactions were terminated by rapid vacuum filtration onto glass
fiber filters. Radioactively trapped onto the filters is determined
and compared to control values. The IC.sub.50 value, or the half
maximal inhibitory concentration, represents the concentration of a
test compound that is required for 50% displacement of the
radioligand from the receptor. A higher IC.sub.50 value reflects a
weaker binding affinity. The IC.sub.50 values for several compounds
prepared in accordance with Example 3 as well as some oligomer-free
corticosteroids are presented in Table 1.
TABLE-US-00001 TABLE 1 IC.sub.50 Values for Tested Compounds Drug
IC.sub.50 (M) Triamcinolone Acetonide 1.21 .times. 10.sup.-9
Cortisone 3.89 .times. 10.sup.-6 mPEG.sub.7-Cortisone 3.44 .times.
10.sup.-6 Hydrocortisone 3.62 .times. 10.sup.-8
mPEG.sub.7-Hydrocortisone 3.93 .times. 10.sup.-9 Dexamethasone 1.50
.times. 10.sup.-9 mPEG.sub.7-Dexamethasone 7.93 .times.
10.sup.-7
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