TECHNICAL FIELD
[0001] The present invention provides heteroarene-based drug derivatives having a "clickable"
ketone group, as well as conjugates of said drug derivatives with targeting moieties
capable of binding to extracellular antigens and pharmaceutical compositions thereof.
[0002] Abbreviations: ACN, acetonitrile;
AcOH, acetic acid;
Ac2O, acetic anhydride;
CHCl3, chloroform;
CPT, camptothecin;
DBTL, dibutyltin dilaurate;
DCM, dichloromethane;
DMAP, dimethylaminopyridine;
DMF, dimethylformamide;
DMSO, dimethylsulfoxide;
Et2O, diethyl ether;
EtOAc, ethylacetate;
EtOH, ethanol;
FBS, fetal bovine serum;
FR, folate receptor;
Hex, n-hexane;
HBTU, (2-(1H-benzotriazol-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate);
HMPA, hexamethylphosphoramide [?]; HMTA, hexamethylenetetra amine;
HPLC, high pressure liquid chromatography;
LHMDS, lithium hexamethyldisilazide;
MeOH, methanol;
MTX, methotrexate;
PBS, phosphate buffered saline;
PEG, polyethylene glycol;
PTSA, p-toluenesulfonic acid;
RPMI, Roswell Park Memorial Institute;
TBHP, tertbutylhydroperoxide;
TFA, trifluoroacetic acid;
THF, tetrahidrofuran;
TLC, thin layer chromatography;
TMZ, temozolomide;
TsOH, p-toluenesulfonic acid.
BACKGROUND ART
[0003] Bioconjugation is an essential tool in chemical biology for attaining controlled
release of a small molecule with medicinal activity. It is typically implemented through
chemoselective modification of native functional groups present on the target molecule
(Zhou
et al., 2013a). For example, amines can be chemoselectively derivatized through amide linkages,
azides or acetylenes through the "click" reaction (Kolb
et al., 2001) and carbonyl groups through the oxime ligation (Ulrich
et al., 2014). Although many medicinal agents contain traditional "taggable" functional groups,
some compounds present the challenge of not having any apparent chemical handles.
As a further layer of complexity, some molecules require an orthogonal handle for
bioconjugation.
[0004] A general C-H functionalization method for the tagging of heteroarenes, more particularly
heteroarene-based drugs, has been recently been introduced by the group of Baran (Gui
et al., 2014; Zhou
et al., 2013b; Fujiwara
et al., 2012; Bruckl
et al., 2012; Ji
et al., 2011). According to that method, an azide-containing sulfinate reagent, more specifically
sodium (difluoroalkylazido)sulfinate, allows the appendage of azidoalkyl chain onto
a heteroaromatic, and the synthesized azide-linked drug is then attached to a monoclonal
antibody, via a succinimide-containing linker, by reacting with a dibenzoazocan-4-yne
(
referred to in the publication as dibenzylazacyclooctyne)-containing monoclonal antibody in a copper-free azide-alkyne cycloaddition, so as
to obtain a drug-antibody conjugate.
SUMMARY OF INVENTION
[0005] The present invention relates to a new chemical linker strategy for construction
of photo-labile or acid-sensitive conjugates, e.g., folate conjugates, of heteroarene-based
drugs or bioactive reagents including those that
a priori have neither limited or no tagging option, and demonstrates the efficacy and chemical
properties of such conjugates. The main advantage of this methodology is the ability
to introduce a "clickable" ketone group into the heteroarene-based drug molecule while
preserving its biological activity. Upon hydrolysis under slightly acidic conditions,
i.e., physiological conditions, the drug conjugate releases the functionalized drug
in a wide-ranging release rates.
[0006] In one aspect, the present invention provides a compound of the formula I:
I Y-CF
2-(CR
1R
2)
n-X-(CR
1R
2)
m-R
1
wherein
Y is a drug or a bioactive reagent, comprising a heteroaromatic ring and linked via
a carbon atom of said heteroaromatic ring;
X is carbonyl, or cyclic ketal substituted with 1 to 4 groups each independently is
phenyl or naphtyl substituted ortho to the carbon of attachment with -NO2, and optionally further substituted at any position other than ortho to the carbon
of attachment with one or more groups each independently selected from -O-(C1-C8), -(C1-C8)alkyl, -N(R')2, or halogen, wherein R' each independently is -(C1-C8)alkyl or H;
R1 and R2 each independently is H, halogen, -OR3, -CO-R3, -CO-OR3, -OCO-OR3, -OCO-N(R3)2, -CN, -NO2, -SR3, -N(R3)2, -CO-N(R3)2, -(C1-C8)alkyl, -(C2-C8)alkenyl, -(C2-C8)alkynyl, (C3-C10)cycloalkyl, (C6-C14)aryl, or 4-12-membered heterocyclyl;
R3 is H, -(C1-C18)alkyl, -(C2-C18)alkenyl, or -(C2-C18)alkynyl; and
n and m each independently is an integer of 1-8,
or a pharmaceutically acceptable salt thereof.
[0007] In another aspect, the present invention provides a conjugate of the formula II:

wherein
Y is a drug or a bioactive reagent, comprising a heteroaromatic ring and linked via
a carbon atom of said heteroarimatic ring;
R1 and R2 each independently is H, halogen, -OR3, -CO-R3, -CO-OR3, -OCO-OR3, -OCO-N(R3)2, -CN, -NO2, -SR3, -N(R3)2, -CO-N(R3)2, -(C1-C8)alkyl, -(C2-C8)alkenyl, -(C2-C8)alkynyl, (C3-C10)cycloalkyl, (C6-C14)aryl, or 4-12-membered heterocyclyl;
R3 is H, -(C1-C18)alkyl, -(C2-C8)alkenyl, or -(C2-C18)alkynyl;
R4 is absent, or is selected from -NH-(CH2)p-, -NH-CO-(CH2)p-, -NH-CO-NH-(CH2)p-, -NH-CO-O-(CH2)p-, -O-(CH2)p-, -O-CO-(CH2)p-, -O-CO-NH-(CH2)p-, or -O-CO-O-(CH2)p-;
R5 is a polymer-, protein-, peptide-, or carbohydrate moiety;
R6 is H, -(CH2)y-OH, -(CH2)y-SH, -(CH2)y-NH2, -(CH2)y-COOH, -(CH2)y-SO3H, or a divalent radical selected from -(CH2)y-O-, -(CH2)y-S-, -(CH2)y-NH-, -(CH2)y-COO- or -(CH2)y-SO3-;
n and m each independently is an integer of 1-8;
p and y each independently is an integer of 0-8; and
T is absent, or is a targeting moiety capable of binding to an extracellular antigen
and linked via a functional group thereof, provided that when T is absent R6 is not a divalent radical, and when T is a targeting moiety R6 is a divalent radical,
or a pharmaceutically acceptable salt thereof.
[0008] In one particular such aspect, the present invention provides a conjugate of the
formula II wherein R
6 is H, -(CH
2)
y-OH, -(CH
2)
y-SH, -(CH
2)
y-NH
2, -(CH
2)
y-COOH, or-(CH
2)
y-SO
3H, wherein y is an integer of 0-8, and T is absent; and in another particular such
aspect, the present invention provides a conjugate of the formula II wherein R
6 is a divalent radical, and T is a targeting moiety capable of binding to an extracellular
antigen.
[0009] In a further aspect, the present invention provides a pharmaceutical composition
comprising either a compound of the formula I as defined above wherein X is not carbonyl;
or a conjugate of the formula II as defined above, or a pharmaceutically acceptable
salt thereof, herein also referred to as the
active agent, and a pharmaceutically acceptable carrier.
[0010] The active agent as referred to herein can be used for prevention, treatment of management
of various diseases, disorders or indications treatable by administration of the drug
or a bioactive reagent Y composing said compound or conjugate.
[0011] Also disclosed herein is a method for treatment of a cancer in an individual in need
thereof, comprising administering to said individual a therapeutically effective amount
of a conjugate of the formula II as defined above, or a pharmaceutically acceptable
salt thereof, wherein Y is an anticancer drug or an antineoplastic drug, and said
targeting moiety is capable of binding to an extracellular antigen present on the
cells of said cancer.
[0012] In still another aspect, the present invention relates to a conjugate of the formula
II as defined above, or a pharmaceutically acceptable salt thereof, wherein Y is an
anticancer drug or an antineoplastic drug, and said targeting moiety is capable of
binding to an extracellular antigen present on the cells of said cancer, for use in
the treatment of cancer.
BRIEF DESCRIPTION OF DRAWINGS
[0013]
Fig. 1 illustrates schematically the bioconjugation approach disclosed herein, as well as
the bioconjugate hydrolysis releasing the drug-derivative.
Figs. 2A-2C show tumor cell growth inhibition assays of CPT (2A), TMZ (2B), and bosutinib (2C) vs. their ketone analogues.
Fig. 3 shows CPT and CPT-ketone 2a cell viability assay on six different cell lines.
Fig. 4 shows bosutinib and bosutinib-ketone 4a cell viability assay on different cell lines.
Figs. 5A-5B show the release of CPT-ketone 2a with and without irradiation of prodrug 6 (5A); and U-87 human primary glioblastoma cell growth inhibition assay of CPT-ketone 2a, and prodrug 6 before and after irradiation (5B).
Fig. 6 shows the hydrolysis rate of CPT-ketone-semicarbazone-PEG-FA 7 as a function of time after incubation in buffer at pH 4.8, 6.0, 6.5, 7.0, and 7.4,
at 37°C.
Figs. 7A-7B show measurement of binding affinity of folate-conjugate 7 with FR receptors using high expressed-FR KB cells (7A); and cytotoxicity assay for CPT-folic acid conjugate 7 using HiFR KB cells (7B).
DETAILED DESCRIPTION
[0014] According to the C-H functionalization method developed by the group of Baran and
discussed above, an azide-containing sulfinate reagent allows the addition of azidoalkyl
chain onto a heteroarene-based drug, and the azide-linked drug synthesized is then
attached to a monoclonal antibody, via a linker, by reacting with a dibenzoazocan-4-yne-containing
monoclonal antibody in a copper-free azide-alkyne cycloaddition, so as to obtain a
drug-antibody conjugate. Baran does not show the hydrolysis of the drug conjugate
obtained as a function of pH and incubation time; however, it may be postulated that
upon hydrolysis under physiological conditions, either the drug-difluoroalkylene-azide
or the drug-difluoroalkylene-8,9-dihydro-1H-dibenzo[b,f][1,2,3]triazolo[4,5-d]azocine
is released. As currently known, such an azide-linked drug loses most, i.e., up to
99%, of its biological activity compared with the underivatized (native) drug.
[0015] It has now been found, in accordance with the present invention, that heteroarene-based
drugs, i.e., drugs comprising a heteroaromatic ring, which lack an appropriate functional
group for linker chemistry, can be functionalized using an alkylating sulfinate reagent
bearing a protected ketone functional group, recently developed by the present inventors,
more particularly sodium 1,1-difluoro-4-(2-methyl-1,3-dioxolan-2-yl)butane-1-sulfinate
via a one-step synthesis. As surprisingly found, a heteroarene-based drug derivative
prepared using said alkylating sulfinate reagent preserves the biological activity
of the underivatized drug.
[0016] The introduction of a "clickable" ketone group into the heteroarene-based drug molecule
allows for the bioconjugation of the drug molecule via an acid labile hydrazone linkage
or through a photo-labile ketal, for controlled-release applications. When a stable
linkage is required, the oxime ligation could also be used to link between the ketone-tagged
moiety and an amine-oxy derivative. Indeed, as further shown herein, drug derivatives
as described above can be bioconjugated through a linker such as polyethylene glycol
(PEG) or a pseudoPEG, having suitable functional groups, to a targeting moiety capable
of binding to an extracellular antigen, e.g., an antibody, sugar, lectin, hormone,
peptidomimetic, or folic acid as exemplified herein, as schematically illustrated
in
Scheme 1.
[0017] Upon hydrolysis under slightly acidic (pH 4.8-6.0) conditions that might mimic endosomal
and liposomal environments, the drug conjugate releases the functionalized drug in
a wide-ranging release rates. The bioconjugation approach disclosed herein, as well
as the bioconjugate hydrolysis releasing the drug-derivative, is schematically illustrated
in
Fig. 1.
[0018] In one aspect, the present invention thus provides a compound, also referred to herein
as "drug derivative", of the formula I:
I Y-CF
2-(CR
1R
2)
n-X-(CR
1R
2)
m-R
1
wherein
Y is a drug or a bioactive reagent, comprising a heteroaromatic ring and linked via
a carbon atom of said heteroaromatic ring;
X is carbonyl, or cyclic ketal substituted with 1 to 4 groups each independently is
phenyl or naphtyl substituted ortho to the carbon of attachment with -NO2, and optionally further substituted at any position other than ortho to the carbon
of attachment with one or more groups each independently selected from -O-(C1-C8), -(C1-C8)alkyl, -N(R')2, or halogen, wherein R' each independently is -(C1-C8)alkyl or H;
R1 and R2 each independently is H, halogen, -OR3, -CO-R3, -CO-OR3, -OCO-OR3, -OCO-N(R3)2, -CN, -NO2, -SR3, -N(R3)2, -CO-N(R3)2, -(C1-C8)alkyl, -(C2-C8)alkenyl, -(C2-C8)alkynyl, (C3-C10)cycloalkyl, (C6-C14)aryl, or 4-12-membered heterocyclyl;
R3 is H, -(C1-C18)alkyl, -(C2-C18)alkenyl, or -(C2-C18)alkynyl; and
n and m each independently is an integer of 1-8,
or a pharmaceutically acceptable salt thereof.
[0019] The term "halogen" as used herein refers to a halogen and includes fluoro, chloro,
bromo, and iodo, and it is preferably fluoro or chloro.
[0020] The term "alkyl" as used herein typically means a linear or branched saturated hydrocarbon
radical having 1-18 carbon atoms and includes, e.g., methyl, ethyl,
n-propyl, isopropyl,
n-butyl, sec-butyl, isobutyl, tert-butyl,
n-pentyl, isoamyl, 2,2-dimethylpropyl,
n-hexyl,
n-heptyl,
n-octyl,
n-nonyl,
n-decyl,
n-undecyl,
n-dodecyl,
n-tridecyl,
n-tetradecyl,
n-pentadecyl,
n-hexadecyl,
n-heptadecyl,
n-octadecyl, and the like. Preferred are (C
1-C
8)alkyl groups, more preferably (C
1-C
4)alkyl groups, most preferably methyl, ethyl or propyl. The terms "alkenyl" and "alkynyl"
typically mean linear and branched hydrocarbon radicals having 2-18 carbon atoms and
1 double or triple bond, respectively, and include ethenyl, propenyl, 3-butenyl, 2-ethenylbutyl,
1- and 2-pentenyl, 1-, 2- and 3-hexenyl, 1-, 2-, 3- and 4-heptenyl, 1-, 2-, 3- and
4-octenyl, 1-, 2-, 3- and 4-nonenyl, 1-, 2-, 3-, 4- and 5-decenyl, and the like, and
propynyl, 2-butynyl, 1- and 2-pentynyl, 1-, 2- and 3-hexynyl, 1-, 2-, 3- and 4-heptynyl,
1-, 2-, 3- and 4-octynyl, 1-, 2-, 3- and 4-nonynyl, 1-, 2-, 3-, 4- and 5-decynyl,
and the like. C
2-C
6 alkenyl and alkynyl radicals are preferred, more preferably C
2-C
4 alkenyl and C
2-C
4 alkynyl. The alkyl, alkenyl and alkynyl defined herein may optionally be substituted
with one or more groups each independently selected from -OR
',-COR
', -COOR
', -OCOOR
', -OCON(R
')
2, -CN, -NO
2, -SR
', -(C
1-C
8)alkyl, -N(R
')
2,-CON(R
')
2, -SO
2R
', -SO
2NHR
', or -S(=O)R
', wherein R
' is H or unsubstituted (C
1-C
8)alkyl.
[0021] The term "alkylene" as used herein means typically means a divalent straight or branched
hydrocarbon radical having 1-8 carbon atoms and includes, e.g., methylene, ethylene,
propylene, butylene, 2-methylpropylene, pentylene, 2-methylbutylene, hexylene, 2-methylpentylene,
3-methylpentylene, 2,3-dimethylbutylene, heptylene, octylene and the like. Preferred
are (C
3-C
8)alkylene, more preferably (C
3-C
6)alkylene.
[0022] The term "cycloalkyl" as used herein means a cyclic or bicyclic hydrocarbyl group
having 3-10 carbon atoms such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl,
cycloheptyl, cyclooctyl, adamantyl, bicyclo[3.2.1]octyl, bicyclo[2.2.1]heptyl, and
the like. Preferred are (C
5-C
10)cycloalkyls, more preferably (C
5-C
7)cycloalkyls. The cycloalkyl defined herein may optionally be substituted with one
or more groups each independently selected from -OR, -COR
', -COOR
', -OCOOR
', -OCON(R
')
2, -CN, -NO
2, -SR
', -(C
1-C
8)alkyl, -N(R
')
2, -CON(R
')
2, -SO
2R
', -SO
2NHR
', or -S(=O)R
', wherein R
' is H or unsubstituted (C
1-C
8)alkyl.
[0023] The term "aryl" denotes an aromatic carbocyclic group having 6-14 carbon atoms consisting
of a single ring or multiple rings either condensed or linked by a covalent bond such
as, but not limited to, phenyl, naphthyl, phenanthryl, and biphenyl. The aryl defined
herein may optionally be substituted with one or more groups each independently selected
from -OR
', -COR
', -COOR
', -OCOOR
', -OCON(R
')
2, -CN, -NO
2, -SR
', -(C
1-C
8)alkyl,-N(R
')
2, -CON(R
')
2, -SO
2R
', -SO
2NHR
', or -S(=O)R
', wherein R is H or unsubstituted (C
1-C
8)alkyl.
[0024] The term "heterocyclic ring" denotes a mono- or poly-cyclic non-aromatic ring of
4-12 atoms containing at least one carbon atom and one to three heteroatoms selected
from sulfur, oxygen or nitrogen, which may be saturated or unsaturated, i.e., containing
at least one unsaturated bond. Preferred are 5- or 6-membered heterocyclic rings.
The term "heterocyclyl" as used herein refers to any univalent radical derived from
a heterocyclic ring as defined herein by removal of hydrogen from any ring atom. Examples
of such radicals include, without limitation, piperidino, 4-morpholinyl, or pyrrolidinyl.
The heterocyclyl defined herein may optionally be substituted, at any position of
the ring, with one or more groups each independently selected from -OR, -COR
', -COOR
', -OCOOR
',-OCON(R
')
2, -CN, -NO
2, -SR
', -(C
1-C
8)alkyl, -N(R
')
2, -CON(R
')
2, -SO
2R
', -SO
2NHR
', or-S(=O)R
', wherein R
' is H or unsubstituted (C
1-C
8)alkyl.
[0025] In certain embodiments, the present invention provides a compound of the formula
I, wherein R
1 and R
2 each independently is H, halogen, -OR
3, -CO-R
3, -CO-OR
3,-OCO-OR
3, -OCO-N(R
3)
2, -CN, -NO
2, -SR
3, -N(R
3)
2, -CO-N(R
3)
2, -(C
1-C
4)alkyl, -(C
2-C
4)alkenyl, -(C
2-C
4)alkynyl, (C
3-C
10)cycloalkyl, (C
6-C
14)aryl, or 4-12-membered heterocyclyl, wherein R
3 is H, -(C
1-C
4)alkyl, -(C
2-C
4)alkenyl, or -(C
2-C
4)alkynyl. Preferred such embodiments are those wherein R
3 is H, methyl, ethyl or propyl, more preferably H.
[0026] In certain embodiments, the present invention provides a compound of the formula
I, wherein n is 3, 4 or 5, preferably 3; or m is 1, 2 or 3, preferably 1.
[0027] In certain embodiments, the present invention provides a compound of the formula
I, wherein R
1 and R
2 each independently is H, halogen, -OR
3, -CO-R
3, -CO-OR
3,-OCO-OR
3, -OCO-N(R
3)
2, -CN, -NO
2, -SR
3, -N(R
3)
2, -CO-N(R
3)
2, -(C
1-C
4)alkyl, -(C
2-C
4)alkenyl, -(C
2-C
4)alkynyl, (C
3-C
10)cycloalkyl, (C
6-C
14)aryl, or 4-12-membered heterocyclyl, wherein R
3 is H, -(C
1-C
4)alkyl, -(C
2-C
4)alkenyl, or -(C
2-C
4)alkynyl, preferably H, methyl, ethyl or propyl; n is 3, 4 or 5, preferably 3; and
m is 1, 2 or 3, preferably 1. Particular such embodiments are those wherein R
1 and R
2 each independently is H, halogen, -OH, -COH, -COOH, -OCOOH, -OCO-NH
2, -CN, -NO
2, -SH, -NH
2, -CO-NH
2, -(C
1-C
4)alkyl, -(C
2-C
4)alkenyl, -(C
2-C
4)alkynyl, (C
3-C
10)cycloalkyl, (C
6-C
14)aryl, or 4-12-membered heterocyclyl; n is 3; and m is 1. In more particular such
embodiments, R
1 and R
2 are H.
[0028] In certain embodiments, the present invention provides a compound of the formula
I, wherein the drug or bioactive reagent Y is selected from anticancer drugs, antineoplastic
drugs, antifungal drugs, antibacterial drugs, antiviral drugs, cardiac drugs, neurological
drugs, psychoactive drugs such as caffeine, drugs of abuse, i.e., drugs taken for
nonmedicinal reasons (usually for mind-altering effects), alkaloids, antibiotics,
bioactive peptides, steroids, steroid hormones, peptide (e.g., polypeptide) hormones,
interferons, interleukins, narcotics, nucleic acids, pesticides, or prostaglandins.
[0029] In particular such embodiments, the drug or bioactive reagent Y is an anticancer
drug such as a chemotherapeutic drug, e.g., camptothecin or a derivative thereof such
as 10-hydroxycamptothecin or any other camptothecin substituted at the 7-, 9- or 10-position
(as described in
Basil and Moro, Expert Opin Ther Pat., 2009, 19(5), 555-574), bosutinib, or methotrexate formerly known as amethopterin; or an antineoplastic
drug such as an alkylating antineoplastic agent, e.g., temozolomide, uramustine or
bendamustine.
[0030] In certain embodiments, the present invention provides a compound of the formula
I as defined in any one of the embodiments above, wherein X is carbonyl, i.e., a compound
of the formula Ia:

[0031] Particular compounds of the formula Ia are those wherein R
1 and R
2 each independently is H, halogen, -OH, -COH, -COOH, -OCOOH, -OCO-NH
2, -CN, -NO
2, -SH, -NH
2, -CO-NH
2, -(C
1-C
4)alkyl, -(C
2-C
4)alkenyl, -(C
2-C
4)alkynyl, (C
3-C
10)cycloalkyl, (C
6-C
14)aryl, or 4-12-membered heterocyclyl, preferably H; n is 3; and m is 1. Specific such
compounds exemplified herein are those wherein R
1 and R
2 are H; n is 3; m is 1; and the drug moiety Y is CPT, TMZ, bosutinib or MTX, herein
identified compounds
2a, 3a, 4a, and
5a, respectively.
[0032] In certain embodiments, the present invention provides a compound of the formula
I as defined in any one of the embodiments above, wherein X is cyclic ketal substituted
as defined above, i.e., a compound of the formula Ib. As shown herein, such compounds
are, in fact, prodrugs for the corresponding compounds wherein X is carbonyl, and
are converted to said corresponding compounds upon exposure to an irradiation, e.g.,
UV irradiation as exemplified herein, or a visible or near infra-red irradiation.

[0033] In particular such embodiments, X is cyclic ketal substituted with 1 or 2 groups
each independently is phenyl substituted ortho to the carbon of attachment with -NO
2, -CN, or -COO-(C
1-C
4)alkyl, preferably -NO
2, and optionally further substituted at any position other than ortho to the carbon
of attachment with one or more groups each independently selected from -O-(C
1-C
4), preferably -O-(C
1-C
2), more preferably -OCH
3. In more particular such embodiments, X is cyclic ketal substituted with 4,5-dimethoxy,2-nitrophenyl
group, or cyclic ketal substituted with two 4,5-dimethoxy,2-nitrophenyl groups wherein
each one of said groups is linked to a different carbon atom of the ketal.
[0034] Particular such compounds are those wherein X is cyclic ketal substituted with 4,5-dimethoxy,2-nitrophenyl
group; R
1 and R
2 each independently is H, halogen, -OH,-COH, -COOH, -OCOOH, -OCO-NH
2, -CN, -NO
2, -SH, -NH
2, -CO-NH
2, -(C
1-C
4)alkyl,-(C
2-C
4)alkenyl, -(C
2-C
4)alkynyl, (C
3-C
10)cycloalkyl, (C
6-C
14)aryl, or 4-12-membered heterocyclyl, preferably H; n is 3; and m is 1. Specific such
compounds are those wherein R
1 and R
2 are H; n is 3; m is 1; and the drug moiety Y is CPT (herein identified compound 6),
TMZ, bosutinib, or MTX.
[0035] The drug derivatives of the formula I wherein X is carbonyl may be synthesized according
to any technology or procedure known in the art, e.g., via a one-step synthesis using
the alkylating sulfinate reagent sodium 1,1-difluoro-4-(2-methyl-1,3-dioxolan-2-yl)butane-1-sulfinate,
as described in the Examples section hereinafter with respect to, e.g., CPT, TMZ,
bosutinib and MTX. Conversion of these drug derivatives to their corresponding prodrugs,
wherein X is cyclic ketal substituted as defined above, can be carried out, e.g.,
by reacting said drug derivatives with ethylene glycol substituted at one or both
of its carbon atoms with, e.g., 4,5-dimethoxy,2-nitrophenyl group, as described in
the Examples section with respect to such a CPT prodrug herein identified compound
6.
[0036] In another aspect, the present invention provides a conjugate of the formula II:

wherein
Y is a drug or a bioactive reagent, comprising a heteroaromatic ring and linked via
a carbon atom of said heteroarimatic ring;
R1 and R2 each independently is H, halogen, -OR3, -CO-R3, -CO-OR3, -OCO-OR3, -OCO-N(R3)2, -CN, -NO2, -SR3, -N(R3)2, -CO-N(R3)2, -(C1-C8)alkyl, -(C2-C8)alkenyl, -(C2-C8)alkynyl, (C3-C10)cycloalkyl, (C6-C14)aryl, or 4-12-membered heterocyclyl;
R3 is H, -(C1-C18)alkyl, -(C2-C18)alkenyl, or -(C2-C18)alkynyl;
R4 is absent, or is selected from -NH-(CH2)p-, -NH-CO-(CH2)p-, -NH-CO-NH-(CH2)p-, -NH-CO-O-(CH2)p-, -O-(CH2)p-, -O-CO-(CH2)p-, -O-CO-NH-(CH2)p-, or -O-CO-O-(CH2)p-;
R5 is a polymer-, protein-, peptide-, or carbohydrate moiety;
R6 is H, -(CH2)y-OH, -(CH2)y-SH, -(CH2)y-NH2, -(CH2)y-COOH, -(CH2)y-SO3H, or a divalent radical selected from -(CH2)y-O-, -(CH2)y-S-, -(CH2)y-NH-, -(CH2)y-COO- or -(CH2)y-SO3-;
n and m each independently is an integer of 1-8;
p and y each independently is an integer of 0-8; and
T is absent, or is a targeting moiety capable of binding to an extracellular antigen
and linked via a functional group thereof, provided that when T is absent R6 is not a divalent radical, and when T is a targeting moiety R6 is a divalent radical,
or a pharmaceutically acceptable salt thereof.
[0037] In certain embodiments, the present invention provides a conjugate of the formula
II, wherein R
1 and R
2 each independently is H, halogen, -OR
3, -CO-R
3, -CO-OR
3, -OCO-OR
3, -OCO-N(R
3)
2, -CN, -NO
2, -SR
3, -N(R
3)
2, -CO-N(R
3)
2, -(C
1-C
4)alkyl, -(C
2-C
4)alkenyl, -(C
2-C
4)alkynyl, (C
3-C
10)cycloalkyl, (C
6-C
14)aryl, or 4-12-membered heterocyclyl, wherein R
3 is H, -(C
1-C
4)alkyl, -(C
2-C
4)alkenyl, or -(C
2-C
4)alkynyl. Preferred such embodiments are those wherein R
3 is H, methyl, ethyl or propyl, more preferably H.
[0038] In certain embodiments, the present invention provides a conjugate of the formula
II, wherein n is 3, 4 or 5, preferably 3; or m is 1, 2 or 3, preferably 1.
[0039] In certain embodiments, the present invention provides a conjugate of the formula
II, wherein R
4 is -NH-CO-(CH
2)
p- or -NH-CO-NH-(CH
2)
p-, wherein p is an integer of 0-8.
[0040] In certain embodiments, the present invention provides a conjugate of the formula
II, wherein R
5 is a polymer moiety, more specifically a biocompatible and biodegradable water-soluble
polymer moiety. Such a polymer may be selected from a linear or branched PEG or copolymers
thereof; a pseudo PEG interrupted by at least one group, each independently preferably
selected from -NH-CO-, -CO-NH-, or (C
3-C
8)alkylene interrupted by at least two groups each independently selected from -NH-CO-
or -CO-NH-; poly(lactic acid) or copolymers thereof; polyesters selected from polylactide
(PLA), polyglycolide (PGA), polycaprolactone (PCL) or copolymers thereof; or polyamides
based on polymethacrylamide or copolymers thereof.
[0041] The term "pseudo PEG" as used herein refers to a hydrophilic chain having great structural
similarities with the PEG chain, which differs via the presence of one or more, e.g.,
one, two, three, four or more, groups such as ester (-CO-O-, -O-CO-), amide (-CO-NH-,
-NH-CO-), carbamate (-O-CO-NH-, -NH-CO-O-), urea (-NH-CO-NH-), and (C
3-C
8)alkylene interrupted by at least two groups each independently selected from ester,
amide, carbamate and urea, within it. According to the present invention, the "pseudo
PEG" may in fact consist of either a sole PEG chain interrupted as defined above,
or two or more separate PEG chains wherein each couple of those PEG chains are linked
to each other via a group such as those listed above.
[0042] In particular such embodiments, R
5 is a polymer moiety, and said polymer is a linear or branched PEG, or a pseudo PEG
interrupted by at least one group each independently selected from -NH-CO-, -CO-NH-,
or (C
3-C
8)alkylene interrupted by at least two groups each independently selected from -NH-CO-
or -CO-NH-, preferably wherein said PEG or pseudo PEG has a molecular weight of 150-20000
Da (PEG/pseudo PEG
150 to PEG/pseudo PEG
20,000), more preferably 500-2000 Da (PEG/pseudo PEG
500-PEG/pseudo PEG
2000) or 500-1000 Da (PEG/pseudo PEG
500-PEG/pseudo PEG
1000), e.g., a pseudo PEG having the structure (-CH
2-CH
2-O)
3-(CH
2)
3-NH-CO-(CH
2)
2-CO-NH-(CH
2)
3-(O-CH
2-CH
2-)
3 as exemplified herein, i.e., a pseudo PEG consisting of two separate PEG chains linked
via an interrupted (C
8)alkylene chain of the formula -(CH
2)
3-NH-CO-(CH
2)
2-CO-NH-(CH
2)
3-.
[0043] In certain embodiments, the present invention provides a conjugate of the formula
II, wherein R
5 is a protein moiety, and said protein is albumin such as human serum albumin (HSA),
a modified albumin such as a cationized bovine serum albumin (CBSA) or a cationized
human serum albumin (CHSA), or a protein containing globin-like domains having long
half-life in circulation such as hemoglobin A or S.
[0044] In certain embodiments, the present invention provides a conjugate of the formula
II, wherein R
5 is a peptide moiety, e.g., an oligopeptide or polypeptide.
[0045] The term "peptide" as used herein refers to a chain of amino acid monomers (residues)
linked by peptide bonds, i.e., the covalent bond formed when a carboxyl group of one
amino acid reacts with an amino group of another. Such peptides include oligopeptides
and polypeptides, as well as peptides consisting of more than 50 amino acid monomers
that are, in fact, proteins of low or medium molecular weight.
[0046] In certain embodiments, the peptide is a dipeptide, tripeptide or tetrapeptide consisting
of 2, 3 or 4 amino acid residues, respectively, or consists of 5-50, 5-40, 5-30, 5-20,
5-15, or 5-10 amino acid residues and configured as a linear peptide, cyclic peptide,
bicyclic peptide or a combination thereof. In more particular such embodiments, said
peptide is a polypeptide consisting of 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15 amino
acid residues. All such peptides may consist of residues of both natural and non-natural
amino acids.
[0047] The term "amino acid" as used herein refers to an organic compound comprising both
amine and carboxylic acid functional groups, which may be either a natural or non-natural
amino acid. The twenty two natural amino acids are aspartic acid (Asp), tyrosine (Tyr),
leucine (Leu), tryptophan (Trp), arginine (Arg), valine (Val), glutamic acid (Glu),
methionine (Met), phenylalanine (Phe), serine (Ser), alanine (Ala), glutamine (Gln),
glycine (Gly), proline (Pro), threonine (Thr), asparagine (Asn), lysine (Lys), histidine
(His), isoleucine (Ile), cysteine (Cys), selenocysteine (Sec), and pyrrolysine (Pyl).
Non-limiting examples of non-natural amino acids include diaminopropionic acid (Dap),
diaminobutyric acid (Dab), ornithine (Orn), aminoadipic acid, β-alanine, 1-naphthylalanine,
3-(1-naphthyl)alanine, 3-(2-naphthyl)alanine, γ-aminobutiric acid (GABA), 3-(aminomethyl)
benzoic acid,
p-ethynyl-phenylalanine,
p-propargly-oxy-phenylalanine,
m-ethynyl-phenylalanine,
p-bromophenylalanine,
p-iodophenylalanine,
p-azidophenylalanine,
p-acetylphenylalanine, azidonorleucine, 6-ethynyl-tryptophan, 5-ethynyl-tryptophan,
3-(6-chloroindolyl)alanine, 3-(6-bromoindolyl)alanine, 3-(5-bromoindolyl)alanine,
azidohomoalanine,
p-chlorophenylalanine, α-aminocaprylic acid, O-methyl-L-tyrosine, N-acetylgalactosamine-α-threonine,
and N-acetylgalactosamine-α-serine.
[0048] In certain embodiments, the present invention provides a conjugate of the formula
II, wherein R
5 is a carbohydrate moiety.
[0049] The term "carbohydrate" refers to a molecule containing carbon, hydrogen and oxygen
atoms. The carbohydrate can be cyclic or linear, saturated or unsaturated and substituted
or unsubstituted. Preferably, the carbohydrate residue comprises one or more saccharide
residues. The phrase "saccharide residue" as used herein encompasses any residue of
a sugar moiety, including monosaccharides, oligosaccharides and polysaccharides. Alternatively,
the saccharide can be a saccharide derivative such as, but not limited to, glucosides,
ethers, esters, acids and amino saccharides. Monosaccharides consist of a single sugar
molecule which cannot be further decomposed by hydrolysis. Examples of monosaccharides
include, without limitation, pentoses such as, but not limited to, arabinose, xylose
and ribose. Oligosaccharides are chains composed of saccharide units. As commonly
defined in the art and herein, oligosaccarides are composed of up to nine saccharide
units. Examples of oligosaccharides include, without limitation, disaccharides such
as, but not limited to, sucrose, maltose, lactose and cellobiose; trisaccharides such
as, but not limited to, mannotriose, raffinose and melezitose; and tetrasaccharides
such as amylopectin, Syalyl Lewis X (SiaLex) and the like. The term "polysaccharide"
refers to a compound composed of at least 10 saccharide units and up to hundreds and
even thousands of monosaccharide units per molecule, which are held together by glycoside
bonds and range in their molecular weights from around 5,000 and up to millions of
Daltons. Non-limiting examples of common polysaccharides include starch, glycogen,
cellulose, gum arabic, agar and chitin.
[0050] In certain embodiments, the present invention provides a conjugate of the formula
II, wherein the drug or bioactive reagent Y is selected from anticancer drugs, antineoplastic
drugs, antifungal drugs, antibacterial drugs, antiviral drugs, cardiac drugs, neurological
drugs, psychoactive drugs such as caffeine, drugs of abuse, alkaloids, antibiotics,
bioactive peptides, steroids, steroid hormones, peptide hormones, interferons, interleukins,
narcotics, nucleic acids, pesticides, or prostaglandins.
[0051] In particular such embodiments, the drug or bioactive reagent Y is an anticancer
drug such as a chemotherapeutic drug, e.g., camptothecin or a derivative thereof such
as 10-hydroxycamptothecin or any other camptothecin substituted at the 7-, 9- or 10-position,
bosutinib, or methotrexate; an antineoplastic drug such as an alkylating antineoplastic
agent, e.g., temozolomide, uramustine or bendamustine; or an antimetabolite such as
methotrexate or 5-fluorouracil.
[0052] In certain embodiments, the present invention provides a conjugate of the formula
II, wherein the targeting moiety is a protein, peptide, polypeptide, glycoprotein,
lipoprotein, lipid, phospholipid, oligonucleotide or a mimic thereof, steroid, hormone,
lymphokine, growth factor, albumin, cytokine, enzyme, coenzyme, vitamin, cofactor,
human antigen, hapten, receptor protein, antibody or a fragment thereof, a substance
used or modified such that it functions as a targeting moiety, or a combination thereof.
Preferred such embodiments are those wherein the targeting moiety is a vitamin such
as vitamin B9 (folic acid).
[0053] According to the present invention, the targeting moiety optionally composing the
conjugate of the formula II is capable of binding to an extracellular antigen. Such
an extracellular antigen may be any antigen presented on the membrane of a mammalian
cell, more particularly a human cell. Particular such extracellular antigens are cancer
antigens, i.e., tumor-specific antigens (TSA, which are present only on tumor cells)
or tumor-associated antigens (TAA, which are present on some tumor cells and also
some normal cells) such as, without being limited to, epidermal growth factor receptor
(EGFR; ErbB-1; HER1 in humans), human epidermal growth factor receptor 2 (HER2), or
prostate specific membrane antigen (PSMA).
[0054] In certain embodiments, the present invention provides a conjugate of the formula
II as defined in any one of the embodiments above, wherein R
1 and R
2 each independently is H, halogen, -OR
3, -CO-R
3, -CO-OR
3, -OCO-OR
3, -OCO-N(R
3)
2, -CN, -NO
2, -SR
3,-N(R
3)
2, -CO-N(R
3)
2, -(C
1-C
4)alkyl, -(C
2-C
4)alkenyl, -(C
2-C
4)alkynyl, (C
3-C
10)cycloalkyl, (C
6-C
14)aryl, or 4-12-membered heterocyclyl, wherein R
3 is H, -(C
1-C
4)alkyl, -(C
2-C
4)alkenyl, or -(C
2-C
4)alkynyl, preferably H, methyl, ethyl or propyl; n is 3, 4 or 5, preferably 3; m is
1, 2 or 3, preferably 1; R
4 is -NH-CO-(CH
2)
p or -NH-CO-NH-(CH
2)
p; and R
5 is a PEG moiety or a pseudo PEG interrupted by at least one group each independently
selected from -NH-CO-, -CO-NH-, or (C
3-C
8)alkylene interrupted by at least two groups each independently selected from -NH-CO-
or -CO-NH-, preferably wherein said PEG or pseudo PEG has a molecular weight of 150-20000,
more preferably 500-2000 or 500-1000. Particular such embodiments are those wherein
R
1 and R
2 each independently is H, halogen, -OH, -COH, -COOH, -OCOOH, -OCO-NH
2, -CN, -NO
2, -SH, -NH
2, -CO-NH
2, -(C
1-C
4)alkyl, -(C
2-C
4)alkenyl, -(C
2-C
4)alkynyl, (C
3-C
10)cycloalkyl, (C
6-C
14)aryl, or 4-12-membered heterocyclyl; n is 3; and m is 1. In more particular such
embodiments, R
1 and R
2 are H; and/or R
5 is a PEG moiety or a pseudo PEG moiety having the structure (-CH
2-CH
2-O)
3-(CH
2)
3-NH-CO-(CH
2)
2-CO-NH-(CH
2)
3-(O-CH
2-CH
2-)
3, i.e., a pseudo PEG consisting of two separate PEG chains linked via an interrupted
(C
8)alkylene chain of the formula -(CH
2)
3-NH-CO-(CH
2)
2-CO-NH-(CH
2)
3-.
[0055] In certain particular such embodiments, R
6 is a divalent radical and T is a targeting moiety capable of binding to an extracellular
antigen. More particular such embodiments are those wherein R
6 is (CH
2)
y-NH-, preferably wherein y is 1 or 2; and said targeting moiety is folic acid linked
via a carboxylic group thereof, i.e., through its alpha (α)- or gamma (γ)- carboxyl
group but preferably through its γ-carboxyl group. More specific such embodiments
are those wherein (i) R
4 is -NH-CO-NH-CH
2-; R
5 is a pseudo PEG moiety having the structure (-CH
2-CH
2-O)
3-(CH
2)
3-NH-CO-(CH
2)
2-CO-NH-(CH
2)
3-(O-CH
2-CH
2-)
3; R
6 is -(CH
2)-NH-; and Y is camptothecin or a derivative thereof such as 10-hydroxycamptothecin,
temozolomide, bosutinib, or methotrexate; (ii) R
4 is -NH-CO-CH
2-; R
5 is a pseudo PEG moiety having the structure (-CH
2-CH
2-O)
3-(CH
2)
3-NH-CO-(CH
2)
2-CO-NH-(CH
2)
3-(O-CH
2-CH
2-)
3; R
6 is -(CH
2)-NH-; and Y is camptothecin or a derivative thereof such as 10-hydroxycamptothecin,
temozolomide, bosutinib, or methotrexate; or (iii) R
4 is -NH-CO-; R
5 is a PEG moiety having the structure (-CH
2-CH
2-O)
3-; R
6 is -(CH
2)
2-NH-; and Y is camptothecin or a derivative thereof such as 10-hydroxycamptothecin,
temozolomide, bosutinib, or methotrexate.
[0056] In other particular such embodiments, R
6 is H, -(CH
2)
y-OH, -(CH
2)
y-SH, -(CH
2)
y-NH
2, -(CH
2)
y-COOH or -(CH
2)
y-SO
3H, preferably -(CH
2)
y-SH, -(CH
2)
y-NH
2, -(CH
2)
y-COOH, and T is absent. More particular such embodiments are those wherein y is 1,
2 or 3.
[0057] As shown in the Example section herein, the conjugate of the formula II can be prepared,
e.g., by condensing a drug derivative of the formula I with a targeting moiety linked
to a linker having a terminal semicarbazide (-NH-CO-NH-NH
2) group, under acidic conditions, thus reacting said semicarbazide group with the
ketone group of said drug derivative, and purifying the conjugate obtained, e.g.,
by HPLC. PEG- and pseudo PEG-based linker having a terminal semicarbazide group can
be prepared according to any technology or procedure known in the art, e.g., as described
with respect to the pseudo PEG-based linker exemplified herein, having the structure
(-CH
2-CH
2-O)
3-(CH
2)
3-NH-CO-(CH
2)
2-CO-NH-(CH
2)
3-(O-CH
2-CH
2-)
3. The conjugate obtained by this process can thus be represented as a drug derivative-linker-targeting
moiety triconjugate, wherein said linker is in fact represented by the sequence -R
4-R
5-R
6- in the formula II, wherein R
4 is the -NH-CO-NH-(CH
2)
p- of the semicarbazide group forming an acid labile hydrazone linkage with the drug
derivative of the formula I, and R
6 comprises a functional group through which said linker is linked to the targeting
moiety. As stated above, when a stable linkage between the targeting moiety and the
linker is required, the oxime ligation could also be used to link between the ketone
group of the drug derivative and an amine-oxy derivative.
[0058] In a further aspect, the present invention provides a pharmaceutical composition
comprising a pharmaceutically acceptable carrier and an active agent as referred to
herein, i.e., either a compound of the formula I as defined in any one of the embodiments
above wherein X is not carbonyl, i.e., a prodrug of the formula Ib; or a conjugate
of the formula II as defined in any one of the embodiments above, or a pharmaceutically
acceptable salt thereof.
[0059] The pharmaceutical compositions of the present invention can be provided in a variety
of formulations, e.g., in a pharmaceutically acceptable form and/or in a salt form,
as well as in a variety of dosages.
[0060] In one embodiment, the pharmaceutical composition of the present invention comprises
a non-toxic pharmaceutically acceptable salt of a compound of the formula Ib; or a
conjugate of the general formula II. Suitable pharmaceutically acceptable salts include
acid addition salts such as, without being limited to, the mesylate salt, the maleate
salt, the fumarate salt, the tartrate salt, the hydrochloride salt, the hydrobromide
salt, the esylate salt, the
p-toluenesulfonate salt, the benzenesulfonate salt, the benzoate salt, the acetate
salt, the phosphate salt, the sulfate salt, the citrate salt, the carbonate salt,
and the succinate salt. Additional pharmaceutically acceptable salts include salts
of ammonium (NH
4+) or an organic cation derived from an amine of the formula R
4N
+, wherein each one of the Rs independently is selected from H, C
1-C
22, preferably C
1-C
6 alkyl, such as methyl, ethyl, propyl, isopropyl,
n-butyl, sec-butyl, isobutyl, tert-butyl,
n-pentyl, 2,2-dimethylpropyl,
n-hexyl, and the like, phenyl, or heteroaryl such as pyridyl, imidazolyl, pyrimidinyl,
and the like, or two of the Rs together with the nitrogen atom to which they are attached
form a 3-7 membered ring optionally containing a further heteroatom selected from
N, S and O, such as pyrrolydine, piperidine and morpholine. Furthermore, where the
compounds of the formula Ib or conjugates of the formula II carry an acidic moiety,
suitable pharmaceutically acceptable salts thereof may include metal salts such as
alkali metal salts, e.g., lithium, sodium or potassium salts, and alkaline earth metal
salts, e.g., calcium or magnesium salts.
[0061] Further pharmaceutically acceptable salts include salts of a cationic lipid or a
mixture of cationic lipids. Cationic lipids are often mixed with neutral lipids prior
to use as delivery agents. Neutral lipids include, but are not limited to, lecithins;
phosphatidylethanolamine; diacyl phosphatidylethanolamines such as dioleoyl phosphatidylethanolamine,
dipalmitoyl phosphatidylethanolamine, palmitoyloleoyl phosphatidylethanolamine and
distearoyl phosphatidylethanolamine; phosphatidylcholine; diacyl phosphatidylcholines
such as dioleoyl phosphatidylcholine, dipalmitoyl phosphatidylcholine, palmitoyloleoyl
phosphatidylcholine and distearoyl phosphatidylcholine; phosphatidylglycerol; diacyl
phosphatidylglycerols such as dioleoyl phosphatidylglycerol, dipalmitoyl phosphatidylglycerol
and distearoyl phosphatidylglycerol; phosphatidylserine; diacyl phosphatidylserines
such as dioleoyl- or dipalmitoyl phosphatidylserine; and diphosphatidylglycerols;
fatty acid esters; glycerol esters; sphingolipids; cardiolipin; cerebrosides; ceramides;
and mixtures thereof. Neutral lipids also include cholesterol and other 3β hydroxy-sterols.
[0062] Examples of cationic lipid compounds include, without being limited to, Lipofectin®
(Life Technologies, Burlington, Ontario) (1:1 (
w/
w) formulation of the cationic lipid N-[1-(2,3-dioleyloxy)propyl]-N,N,N-trimethylammonium
chloride and dioleoylphosphatidyl-ethanolamine); Lipofectamine™ (Life Technologies,
Burlington, Ontario) (3:1 (
w/
w) formulation of polycationic lipid 2,3-dioleyloxy-N-[2(spermine-carboxamido)ethyl]-N,N-dimethyl-1-propanamin-iumtrifluoroacetate
and dioleoylphosphatidyl-ethanolamine), Lipofectamine Plus (Life Technologies, Burlington,
Ontario) (Lipofectamine and Plus reagent), Lipofectamine 2000 (Life Technologies,
Burlington, Ontario) (Cationic lipid), Effectene (Qiagen, Mississauga, Ontario) (Non
liposomal lipid formulation), Metafectene (Biontex, Munich, Germany) (Polycationic
lipid), Eu-fectins (Promega Biosciences, San Luis Obispo, Calif.) (ethanolic cationic
lipids numbers 1 through 12: C
52H
106N
6O
4·4CF
3CO
2H, C
88H
178N
8O
4S
2·4CF
3CO
2H, C
40H
84NO
3P·CF
3CO
2H, C
50H
103N
7O
3·4CF
3CO
2H, C
55H
116N
8O
2·6CF
3CO
2H, C
49H
102N
6O
3·4CF
3CO
2H, C
44H
89N
5O
3·2CF
3CO
2H, C
100H
206N
12O
4S
2·8CF
3CO
2H, C
162H
330N
22O
9·13CF
3CO
2H, C
43H
88N
4O
2·2CF
3CO
2H, C
43H
88N
4O
3·2CF
3CO
2H, C
41H
78NO
8P); Cytofectene (Bio-Rad, Hercules, Calif.) (mixture of a cationic lipid and a neutral
lipid), GenePORTER® (Gene Therapy Systems, San Diego, Calif.) (formulation of a neutral
lipid (Dope) and a cationic lipid) and FuGENE 6 (Roche Molecular Biochemicals, Indianapolis,
Ind.) (Multi-component lipid based non-liposomal reagent).
[0063] The pharmaceutically acceptable salts of the present invention may be formed by conventional
means, e.g., by reacting a free base form of the active agent with one or more equivalents
of the appropriate acid in a solvent or medium in which the salt is insoluble, or
in a solvent such as water which is removed
in vacuo or by freeze drying, or by exchanging the anion/cation of an existing salt for another
anion/cation on a suitable ion exchange resin.
[0064] The pharmaceutical compositions provided by the present invention may be prepared
by conventional techniques, e.g., as described in
Remington: The Science and Practice of Pharmacy, 19th Ed., 1995. The compositions can be prepared, e.g., by uniformly and intimately bringing the
active agent into association with a liquid carrier, a finely divided solid carrier,
or both, and then, if necessary, shaping the product into the desired formulation.
The compositions may be in liquid, solid or semisolid form and may further include
pharmaceutically acceptable fillers, carriers, diluents or adjuvants, and other inert
ingredients and excipients. In one embodiment, the pharmaceutical composition of the
present invention is formulated as nanoparticles.
[0065] The compositions can be formulated for any suitable route of administration, but
they are preferably formulated for parenteral, e.g., intravenous, intraarterial, intramuscular,
intraperitoneal, intrathecal, intrapleural, intratracheal, subcutaneous, or topical
administration, as well as for inhalation. The dosage will depend on the state of
the patient, i.e., individual treated, and will be determined as deemed appropriate
by the practitioner.
[0066] The pharmaceutical composition of the invention may be in the form of a sterile injectable
aqueous or oleagenous suspension, which may be formulated according to the known art
using suitable dispersing, wetting or suspending agents. The sterile injectable preparation
may also be a sterile injectable solution or suspension in a non-toxic parenterally
acceptable diluent or solvent. Acceptable vehicles and solvents that may be employed
include, without limiting, water, Ringer's solution, PEG, 2-hydroxypropyl-β-cyclodextrin
(HPCD), Tween-80, and isotonic sodium chloride solution.
[0067] Pharmaceutical compositions according to the present invention, when formulated for
inhalation, may be administered utilizing any suitable device known in the art, such
as metered dose inhalers, liquid nebulizers, dry powder inhalers, sprayers, thermal
vaporizers, electrohydrodynamic aerosolizers, and the like.
[0068] Pharmaceutical compositions according to the present invention, when formulated for
administration route other than parenteral administration, may be in a form suitable
for oral use, e.g., as tablets, troches, lozenges, aqueous, or oily suspensions, dispersible
powders or granules, emulsions, hard or soft capsules, or syrups or elixirs.
[0069] Pharmaceutical compositions intended for oral administration may be formulated so
as to inhibit the release of the active agent in the stomach, i.e., delay the release
of the active agent until at least a portion of the dosage form has traversed the
stomach, in order to avoid the acidity of the gastric contents from hydrolyzing the
active agent. Particular such compositions are those wherein the active agent is coated
by a pH-dependent enteric-coating polymer. Examples of pH-dependent enteric-coating
polymer include, without being limited to, Eudragit® S (poly(methacrylicacid, methylmethacrylate),
1:2), Eudragit® L 55 (poly (methacrylicacid, ethylacrylate), 1:1), Kollicoat® (poly(methacrylicacid,
ethylacrylate), 1:1), hydroxypropyl methylcellulose phthalate (HPMCP), alginates,
carboxymethylcellulose, and combinations thereof. The pH-dependent enteric-coating
polymer may be present in the composition in an amount from about 10% to about 95%
by weight of the entire composition.
[0070] Pharmaceutical compositions intended for oral administration may be prepared according
to any method known to the art for the manufacture of pharmaceutical compositions
and may further comprise one or more agents selected from sweetening agents, flavoring
agents, coloring agents and preserving agents in order to provide pharmaceutically
elegant and palatable preparations. Tablets contain the active ingredient in admixture
with non-toxic pharmaceutically acceptable excipients, which are suitable for the
manufacture of tablets. These excipients may be, e.g., inert diluents such as calcium
carbonate, sodium carbonate, lactose, calcium phosphate, or sodium phosphate; granulating
and disintegrating agents, e.g., corn starch or alginic acid; binding agents, e.g.,
starch, gelatin or acacia; and lubricating agents, e.g., magnesium stearate, stearic
acid, or talc. The tablets may be either uncoated or coated utilizing 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
using the techniques described in the
US Patent Nos. 4,256,108,
4,166,452 and
4,265,874 to form osmotic therapeutic tablets for control release. The pharmaceutical composition
of the invention may also be in the form of oil-in-water emulsion.
[0071] The pharmaceutical compositions of the invention may be formulated for controlled
release, i.e., extended- or sustained-release, of the active agent. Such compositions
may be formulated as controlled-release matrix, e.g., as controlled-release matrix
tablets in which the release of a soluble active agent is controlled by having the
active diffuse through a gel formed after the swelling of a hydrophilic polymer brought
into contact with dissolving liquid (
in vitro) or gastro-intestinal fluid (
in vivo). Many polymers have been described as capable of forming such gel, e.g., derivatives
of cellulose, in particular the cellulose ethers such as hydroxypropyl cellulose,
hydroxymethyl cellulose, methylcellulose or methyl hydroxypropyl cellulose, and among
the different commercial grades of these ethers are those showing fairly high viscosity.
In other configurations, the compositions comprise the active agent formulated for
controlled release in microencapsulated dosage form, in which small droplets of the
active agent are surrounded by a coating or a membrane to form particles in the range
of a few micrometers to a few millimeters.
[0072] Another contemplated formulation is depot systems, based on biodegradable polymers,
wherein as the polymer degrades, the active ingredient is slowly released. The most
common class of biodegradable polymers is the hydrolytically labile polyesters prepared
from lactic acid, glycolic acid, or combinations of these two molecules. Polymers
prepared from these individual monomers include poly (D,L-lactide) (PLA), poly (glycolide)
(PGA), and the copolymer poly (D,L-lactide-co-glycolide) (PLG).
[0073] The active agent as referred to herein, as well as the pharmaceutical composition
thereof, can be used for prevention, treatment of management of various diseases,
disorders or indications treatable by administration of the drug or a bioactive reagent
Y composing said active agent.
[0074] Further disclosed herein is a method for treatment of a cancer in an individual in
need thereof, comprising administering to said individual a therapeutically effective
amount of a conjugate of the formula II as defined in any one of the embodiments above,
or a pharmaceutically acceptable salt thereof, wherein Y is an anticancer drug, e.g.,
a chemotherapeutic drug such as camptothecin or a derivative thereof, bosutinib or
methotrexate, or an antineoplastic drug, e.g., an alkylating antineoplastic agent
such as temozolomide, uramustine or bendamustine; and said targeting moiety is capable
of binding to an extracellular antigen present on the cells of said cancer. In a disclosure,
the cancer treated by this method is characterized by folate receptor overexpressing
cells, and said targeting moiety is folic acid linked via a carboxylic group thereof,
preferably through its gamma-carboxyl group. In another disclosure, said cancer is
carcinoma.
[0075] In still another aspect, the present invention relates to a conjugate of the formula
II as defined in any one of the embodiments above, or a pharmaceutically acceptable
salt thereof, wherein Y is an anticancer drug or an antineoplastic drug, and said
targeting moiety is capable of binding to an extracellular antigen present on the
cells of said cancer, for use in the treatment of a cancer. In a particular embodiment,
the conjugate is used in the treatment of a cancer characterized by folate receptor
overexpressing cells, e.g., a carcinoma, wherein said targeting moiety is folic acid
linked via a carboxylic group thereof, preferably through its gamma-carboxyl group.
[0076] The invention will now be illustrated by the following non-limiting Examples.
EXAMPLES
Synthesis schemes and experimental procedures
Materials and Methods
[0077] All reactions requiring anhydrous conditions were performed under argon atmosphere.
All reactions were carried out at room temperature unless stated otherwise. Chemicals
and solvents were either standard analytical grade (A.R. grade) or purified by standard
techniques. TLC: silica gel plates Merck 60 F
254, compounds were visualized by irradiation with UV light. Flash chromatography: silica
gel Merck 60 (particle size 0.040-0.063 mm), eluent given in parentheses. HPLC: C18
5µ, 250×4.6mm, eluent given in parentheses. Preparative HPLC: C18 5µ, 250×21mm, eluent
given in parentheses.
1H-NMR and
13C-NMR spectra were measured using Bruker Avance operated at 400MHz as mentioned. All
general reagents, including salts and solvents, were purchased from Sigma-Aldrich.
Absorption and fluorescence spectra were recorded on Spectramax-M2 fluorescent spectrometer
using quartz cuvettes or quartz 96-wells plate reader.
Compound 1c
[0078] Mercaptopyridine was reacted with bromodifluoromethyl diethylphosphonate under basic
conditions. The non-isolated thio-pyridine product was oxidized using sodium periodate
to afford the sulfonyl-pyridine derivative
1a.
[0079] Pentaiodoacetal
1b was prepared first by replacement reaction of 5-chloro-2-pentanone with sodium iodide
in acetone. The carbonyl group of 5-iodo-2-pentanone was protected with ethylene glycol
catalyzed by PTSA.
[0080] As depicted in
Scheme 2, to a flask equipped with a magnetic stirrer, HMPA (4 mL) was added under N
2 atmosphere to a solution of 2-(difluoromethylsulfonyl)-pyridine (1.5 g, 7.8 mmol,
1.0 equiv.) in THF (50 mL). The reaction mixture was cooled to -98°C (CH
3OH/liquid nitrogen bath), then 2-methyl-2-(3-iodo)-propyl-1,3-dioxolane (3.15 mL,
0.0194, 2.5 equiv.) was added. A THF solution of LHMDS (2.72 mL, 3.5 equiv.) was added
dropwise over 35 minute. After 30 minutes, the reaction mixture was quenched with
saturated aqueous NH
4Cl solution (2 mL) at -98°C. The cold bath was removed and distilled water (1 mL)
was added. The mixture was extracted with EtOAc. The combined organic solution was
treated with saturated aqueous NaCl to remove HMPA and dried over Na
2SO
4. The solvent was removed under reduced pressure to obtain a crude product which was
purified by flash column chromatography (EtOAc/Hex) to give a pure product
1c (1.67 g, 67% yield) as a light yellow viscous oil.
1H NMR (400 MHz, CDCl
3): δ 8.90-8.84 (m, 1H), 8.17 (dd, J = 7.9, 0.7 Hz, 1H), 8.04 (td, J = 7.8, 1.6 Hz,
1H), 7.67 (ddd, J = 7.7, 4.7, 1.0 Hz, 1H), 4.01-3.85 (m, 2H), 2.58-2.31 (m, 2H), 1.81-1.71
(m, 4H), 1.32 (s, 3H).
13C NMR (101 MHz, CDCl
3) δ 152.65, 151.45, 139.21, 129.55, 128.55, 125.70 (t), 109.80, 65.10, 38.58, 30.78(t),
24.25, 16.07. MS (ESI+) m/z: 322.
Ketal sulfinate 1
[0081] As depicted in
Scheme 2, sodium ethanethiol (1.2 g, 14.3 mmol, 3 equiv) was dissolved in THF (60 mL) at 0°C
under argon atmosphere and stirred at 0°C for 5 minutes. THF (30 mL) solution of
1c (1.5 g, 4.7 mmol, 1.0 equiv.) was added. The flask was sealed with a cap and further
wrapped with parafilm. The mixture was stirred at 0°C for 2 h, then at room temperature
for 10 h. The solvent was removed under vacuum, and the residue was purified by column
chromatography (MeOH/DCM) to give ketal sulfinate
1 (4.1 g, 93% yield).
1H NMR (400 MHz, DMSO-d
6): δ 3.88-3.79 (m, 2H), 1.90-1.70 (m, 2H), 1.63-1.54 (m, 2H), 1.46 (m, 2H), 1.22 (s,
3H).
13C NMR (400 MHz, CDCl
3) δ 134.04, 131.23, 128.42, 112.76, 67.55, 41.75, 30.20, 29.99, 29.78, 26.03, 18.63.
MS (ESI-) m/z: 243.
CPT-ketone (compound 2a)
[0082] To a solution of CPT (
2, 150 mg, 0.43 mmol, 1.0 equiv.), ketal sulfinate
1 (343 mg, 1.29 mmol, 3.0 equiv.) and ZnCl
2 (123 mg, 0.64 mmol, 1.5 equiv.) in DCM (2.5 mL) and H
2O (1 mL) was added PTSA (54 mg, 0.43 mmol, 1.0 equiv.). The reaction mixture was cooled
in ice bath and TBHP (70% solution in water, 0.214 mL, 5.0 equiv.) was added dropwise
with vigorous stirring. The stirring was continued at this temperature for 5 minutes.
The reaction was warmed to room temperature and monitored by TLC until completion.
After 24 h, a second addition of ZnCl
2 (123 mg, 0.64 mmol, 1.5 equiv.), ketal kulfinate
1 (343 mg, 1.29 mmole, 3.0 equiv.) and TBHP (0.214 mL 5.0 equiv.) was performed to
drive the reaction further. Upon consumption of the starting material, the reaction
was partitioned between DCM and saturated aqueous NaHCO
3 (2.0 mL). The organic layer was separated, and the aqueous layer was extracted with
DCM (3×2.0 mL). The combined organic solution was dried over Na
2SO
4, concentrated in vacuum and purified by column chromatography to give product
2a (140 mg, 75% yield).
1H NMR (400 MHz, CDCl
3): δ 8.27 (dd, J = 16.1, 8.5 Hz, 2H), 7.87 (t, J = 7.6 Hz, 1H), 7.79-7.65 (m, 2H),
5.46 (d, J = 3.1 Hz, 2H), 2.56 (td, J = 7.1, 3.6 Hz, 2H), 2.51-2.38 (m, 2H), 2.13
(s,3H), 1.99-1.78 (m, 4H), 1.07 (t, J = 7.4 Hz, 3H). MS (TOF-ESI): m/z 483.3 [M+ H]
+, 481.4 [M-H]
-.
13C NMR (101 MHz, CDCl
3) δ 208.01, 174.62, 158.13, 153.28, 150.80, 150.66, 146.25, 137.89, 131.68, 131.31,
129.62, 126.67, 125.41, 124.60, 119.87, 98.75, 73.45, 67.10, 52.04, 42.86, 38.69,
32.34, 30.70, 30.42, 16.91, 8.54. MS (ESI+) m/z: 483, 405 [M+Na].
10-hydroxy CPT-ketone
[0083] Using the synthetic procedure described above for CPT-ketone, an analogue of 10-hydroxy
CPT-ketone, a compound having a similarity to the SN-38 anti-cancer drug, can be prepared.
TMZ-ketone (compound 3a)
[0084] To a solution of TMZ (
3, 25 mg, 0.13 mmol, 1.0 equiv.), ketal sulfinate
1 (120 mg, 0.45 mmol, 3.5 equiv.) and ZnCl
2 (31 mg, 0.22 mmol, 1.75 equiv.) in DMSO (1 mL) was added TFA (0.02 mL, 0.19 mmol,
1.5 equiv.). The reaction mixture was cooled in ice bath and TBHP (70% solution in
water, 0.071 mL, 5.5 equiv.) was added dropwise with vigorous stirring. The stirring
was continued at this temperature for 5 minutes. The reaction was warmed to 50°C and
monitored by HPLC. The reaction stopped after 1h and purified by preperative HPLC
to give product
3a (7 mg, 28% yield).
1H NMR (400 MHz, CDCl
3) δ 7.45 (s, 1H), 7.26 (s, 1H), 6.28 (s, 1H), 4.07 (s, 3H), 2.68-2.52 (m, 4H), 2.16
(s, 3H), 1.98-1.84 (m, 2H). MS (ESI+) m/z: 329, 351 [M+Na].
Bosutinib-ketone (compound 4a)
[0085] To a solution of bosutinib (
4, 20 mg, 0.04 mmol, 1.0 equiv.), Ketal Sulfinate
1 (30 mg, 0.11 mmol, 3 equiv.) and ZnCl
2 (11 mg, 0.05 mmol, 1.5 equiv.) in DMSO:H
2O (0.2:0.2 mL) was added TFA (12 µL, 0.15 mmol, 4 equiv.). The reaction mixture was
cooled in ice bath and TBHP (70% solution in water, 0.019 mL, 5 equiv.) was added
dropwise with vigorous stirring. The stirring was continued at this temperature for
5 minutes. The reaction was warmed to 50°C and monitored by HPLC. After 24 h, a second
addition of ZnCl
2 (11 mg, 0.056 mmol, 1.5 equiv.), ketal sulfinate
1 (30 mg, 0.11 mmole, 3.0 equiv.) and TBHP (0.019 mL 5.0 equiv.) was performed to drive
the reaction further. The reaction stopped after 24 h and purified by preparative
HPLC to give product
4a (17 mg, 73% yield).
1H NMR (400 MHz, DMSO) δ 8.16 (d, J = 7.9 Hz, 1H), 7.70 (d, J = 8.8 Hz, 2H), 6.71 (d,
J = 8.9 Hz, 2H), 5.01 (s, 1H), 4.32 (s, 1H), 3.19 (s, 2H), 2.37-2.28 (m, 3H), 2.12-1.99
(m, 4H), 1.89 (s, 1H), 1.73-1.66 (m, 1H).
13C NMR (101 MHz, CDCl
3) δ 208.68, 154.42, 153.30, 152.64, 150.51, 150.40, 145.39, 137.50, 130.74, 121.38,
118.84, 117.81, 117.62, 115.00, 114.79, 110.21, 106.11, 102.10, 91.39, 66.17, 56.66,
55.91, 54.76, 50.78, 50.09, 49.88, 49.67, 49.45, 49.24, 48.99, 43.22, 42.82, 34.87,
29.95, 24.18, 16.42. MS (ESI+) m/z: 665, 687 [M+Na].
MTX-ketone (compound 5a)
[0086] To a solution of MTX (
5, 30 mg, 0.06 mmol, 1.0 equiv.), ketal sulfinate
1 (105 mg, 0.42 mmol, 6 equiv.) and ZnCl
2 (38 mg, 0.19 mmol, 3 equiv.) in DMSO (1 mL) was added PTSA (27 mg, 0.19 mmol, 3 equiv.).
The reaction mixture was cooled in ice bath and TBHP (70% solution in water, 0.066
mL, 10 equiv.) was added dropwise with vigorous stirring. The stirring was continued
at this temperature for 5 minutes. The reaction was warmed to 50°C and monitored by
HPLC. The reaction stopped after 24 h and purified by preparative HPLC to give product
5a (13 mg, 35% yield).
1H NMR (400 MHz, DMSO) δ 8.16 (d, J = 7.9 Hz, 1H), 7.70 (d, J = 8.8 Hz, 2H), 6.71 (d,
J = 8.9 Hz, 2H), 5.01 (s, 1H), 4.32 (s, 1H), 3.19 (s, 2H), 2.37-2.28 (m, 3H), 2.12-1.99
(m, 4H), 1.89 (s, 1H), 1.73-1.66 (m, 1H).
13C NMR (101 MHz, DMSO) δ 209.11, 174.97, 163.12, 152.59, 132.87, 132.71, 130.69, 129.99,
129.32, 128.06, 123.00, 122.09, 117.32, 112.18, 54.22, 52.89, 42.85, 31.58, 31.20,
30.94, 27.14, 17.36, 16.90. MS (ESI+) m/z: 589.
Compound 9
[0087] As depicted in
Scheme 3, a solution of benzylchloroformate (1.3 mL, 9 mmol) in DCM (20 mL) was added over
1.5 h to a solution of compound
8 (2 gr, 9 mmol) and triethyl amine (3.8 ml, 27 mmol) in DCM (40 mL) cooled at 0°C.
The solution was stirred for 2 h at 0°C, then warmed to room temperature. After completion
the crude was concentrated by evaporation and the product was purified by column chromatography
(Hex:EtOAc) to give product
9 (1.3 gr, 40% yield).
1H NMR (400 MHz, CDCl
3) δ 7.21-7.11 (m, 5H), 4.89 (s, 2H), 3.46-3.31 (m, 12H), 3.07 (dd, J = 12.6, 6.3 Hz,
2H), 2.94 (t, J = 6.5 Hz, 2H), 1.84-1.76 (m, 1H), 1.64-1.56 (m, 1H).
13C NMR (101 MHz, CDCl
3) δ 157.58, 137.35, 129.06, 128.58, 128.47, 70.78, 70.54, 70.40, 69.63, 66.97, 50.32,
39.36, 39.16, 30.06, 27.39. MS (ESI+) m/z: 255.
Compound 10
[0088] As depicted in
Scheme 3, compound
9 (100 mg, 0.28 mmol), DMAP (70 mg, 0.6 mmol) and succinic anhydride (28 mg, 0.28 mmol)
were dissolved into 4 mL of DCM. The solution was stirred for 2 h. After completion,
the mixture was extracted with 1 M HCl, the organic layer dried over Na
2SO
4, and concentrated to give product
10 (96 mg, 75% yield).
1H NMR (400 MHz, CDCl
3) δ 7.28-7.13 (m, 1H), 6.98 (s, 1H), 5.79 (s, 1H), 4.92 (s, 1H), 3.52-3.27 (m, 3H),
3.17-3.08 (m, 1H), 2.52-2.41 (m, 1H), 2.38-2.30 (m, 1H), 1.60 (dt, J = 12.6, 6.2 Hz,
1H).
13C NMR (101 MHz, CDCl
3) δ 175.87, 173.23, 157.42, 137.41, 129.09, 128.61, 128.38, 70.97, 70.63, 70.56, 70.03,
69.92, 67.01, 39.54, 38.29, 31.35, 30.39, 30.05, 29.44. MS (ESI-) m/z: 425. MS (ESI+)
m/z: 247.
Compound 11
[0089] As depicted in
Scheme 4, in one flask, triphosgene (288 mg, 0.5 mmol, 1.2 equiv.) was dissolved in toluene
(16 mL). In a separate flask, tert-butyl (2-(2-(2-aminoethoxy)ethoxy)ethyl)carbamate
(200 mg, 0.4 mmol, 1 equiv.) was dissolved in toluene (12 mL) and the resulted solution
was added dropwise within 10 minutes to the mixture in the first flask at reflux.
The reaction mixture was kept at reflux for 30 minutes. The toluene was removed under
reduced pressure to obtain the corresponding crude isocyanate intermediate product
which was dissolved in a solution of toluene (10 mL), DBTL (3 drops) and tert-butyl
carbazate (104 mL, 0.4 mmol, 1 equiv.), then the mixture was heated to reflux for
30 minutes and monitored by TLC (Hex:EtOAc). The toluene was removed under vacuum
and the crude product was purified by column chromatography (Hex:EtOAc) to give product
11 (200 mg, 50% yield).
1H NMR (400 MHz, CDCl
3) δ 8.10-7.19 (m, 5H), 7.12 (s, 1H), 6.59 (s, 1H), 6.19 (s, 1H), 5.54 (s, 1H), 5.07
(s, 2H), 3.79-3.42 (m, 12H), 3.42-3.16 (m, 4H), 1.85-1.64 (m, 4H), 1.44 (s, 9H).
13C NMR (101 MHz, CDCl
3) δ 159.76, 157.36, 156.79, 137.50, 129.17, 128.83, 128.70, 81.97, 71.32, 71.11, 70.88,
70.73, 70.63, 70.06, 67.16, 39.74, 39.49, 30.11, 29.65, 28.95.
Compound 12
[0090] As depicted in
Scheme 4, a mixture of compound
11 (100 mg, 0.19 mmol), 5% Pd/C (cat.), and methanol was stirred under a balloon of
hydrogen at ambient pressure at room temperature overnight. The reaction mixture was
then filtered through a short plug of Celite and the filtrate was concentrated in
vacuo to give product
12 (68 mg, 93 % yield).
1H NMR (400 MHz, CDCl
3) δ 3.53 (m, 14H), 3.22 (m, 2H), 3.04 (m, 1H), 1.92 (s, 2H), 1.61 (m, , 4H), 1.36
(s, 9H).
13C NMR (101 MHz, CDCl
3) δ 160.20, 157.36, 81.66, 71.03, 70.55, 70.20, 70.01, 42.11, 41.72, 39.83, 38.46,
30.09, 28.96, 27.92. MS (ESI+) m/z: 379, 401 [M+Na].
Compound 13
[0091] As depicted in
Scheme 4, compound
12 (50 mg, 0.13 mmol), DMAP (33 mg, 0.26 mmol) and succinic anhydride (14 mg, 0.13 mmol)
were dissolved into 3 mL of DCM. The solution was stirred for 2 h. After completion,
the mixture was extracted with 1 M HCl, the organic layer dried over Na
2SO
4, and concentrated to give product
13 (46 mg, 70% yield).
1H NMR (400 MHz, CDCl
3) δ 3.55-3.37 (m, 12H), 3.15 (m, 2H), 2.63-2.41 (m, 4H), 2.32 (m, 2H), 1.72-1.61 (m,
4H), 1.33 (s, 9H).
13C NMR (101 MHz, CDCl
3) δ 177.12, 173.48, 160.94, 156.80, 82.01, 72.20, 71.09, 70.87, 70.04, 40.53, 37.40,
32.12, 31.20, 30.41, 30.08, 29.97, 29.12, 29.03. MS (ESI+) m/z: 451.
Compound 14
[0092] As depicted in
Scheme 5, DMAP (68 mg, 0.55 mmol, 3 equiv.) and compound
10 (70 mg, 0.18 mmol, 1 equiv.) were dissolved in DCM (2 mL). HBTU (210 mg, 0.55 mmol,
3 equiv.) was added and the reaction mixture was stirred in room temperature for 10
minutes, then compound
13 (84 mg, 0.19 mmol, 1 equiv.) was added, and the reaction was monitored by TLC (Hex:EtOAc).
After completion the product was purified by coloumn chromatography (Hex:EtOAc), to
give product
14 (97 mg, 82% yield).
Compound 15
[0093] As depicted in
Scheme 5, a mixture of compound
14 (97 mg, 0.0.151 mmol), 5% Pd/C (cat.), and methanol was stirred under a balloon of
hydrogen at ambient pressure at room temperature overnight. The reaction mixture was
then filtered through a short plug of Celite and the filtrate was concentrated in
vacuo and directly reacted.
[0094] DMAP (25 mg, 0.21 mmol, 8 equiv.) and folic acid (50 mg, 0.105 mmol, 4 equiv.) were
dissolved in DMSO (4 mL). HBTU (20 mg, 0.052 mmol, 2 equiv.) was added and the reaction
mixture was stirred in room temperature for 10 minutes, then compound
14a (13 mg, 0.026 mmol, 1 equiv.) was added, the reaction progress was monitored by HPLC
(ACN/H
2O). After completion the product was purified by preparative HPLC (ACN/H
2O) to give product
15 (24 mg, 60% yield).
1H NMR (400 MHz, DMSO) δ 8.68 (s, 1H), 7.64 (d, J = 6.5 Hz, 2H), 6.63 (d, J = 8.7 Hz,
2H), 4.52 (s, 2H), 4.26 (d, J = 9.6 Hz, 1H), 3.61 - 3.17 (m, 22H), 3.06 (dd, J = 22.9,
6.1 Hz, 10H), 2.26-1.98 (m, 8H), 1.58 (dd, J = 16.1, 9.8 Hz, 8H), 1.37 (s, 9H).
13C NMR (101 MHz, DMSO) δ 175.06, 175.06, 172.42, 172.42, 167.42, 159.59, 154.11, 154.11,
151.82, 149.35, 149.35, 130.17, 130.17, 129.16, 129.16, 112.40, 112.40, 80.11, 70.92,
70.92, 70.70, 70.70, 69.45, 69.22, 69.22, 53.39, 46.98, 38.03, 37.78, 36.95, 36.95,
33.18, 32.49, 32.02, 32.02, 31.16, 30.85, 30.53, 30.53, 29.25, 29.25, 27.70. MS (ESI+)
m/z: 1223, 1245 [M+Na].
Compound 7
[0095] As depicted in
Scheme 6, compound
15 was dissolved in a mixture of 2 ml DCM and 2 ml TFA, and stirred for 1h. After completion
the product was concentrated in vacuum and directly reacted in the next step.
[0096] CPT-ketone
2a (20 mg, 0.0414 mmol, 1 equiv.) was dissolved in methanol (5 mL). TFA (5 drops) and
compound
15a (82 mg, 0.083 mmol, 2 equiv.) were added and the mixture was stirred for 2 hour at
40°C. The reaction progress was monitored by HPLC (ACN/H
2O). After completion, the crude was purified by preparative HPLC (ACN/H
2O) to give
7 (40 mg, 75% yield).
1H NMR (400 MHz, DMSO) δ 8.90 (s, 1H), 8.61 (d, J = 2.2 Hz, 1H), 8.22-8.26 (m, 3H),
8.01-7.61 (m, 8H), 7.10-6.85 (m, 2H), 6.59 (m, 3H), 5.53-5.15 (m, 3H), 4.87 (s, 1H),
4.46 (d, J = 4.4 Hz, 2H), 4.31 (m, 1H), 3.50 (m, 22H), 3.16-2.93 (m, 10H), 2.51 (m,
2H), 1.57 (m, 8H), 0.88 (t, J = 7.1 Hz, 2H).
13C NMR (101 MHz, DMSO) δ 173.69, 172.41, 157.77, 157.41, 153.76, 151.83, 151.19, 149.99,
149.71, 145.85, 142.15, 132.77, 131.59, 131.05, 130.23, 129.92, 129.72, 129.15, 128.86,
127.60, 125.91, 124.40, 122.96, 120.26, 113.55, 112.42, 97.90, 73.57, 70.90, 70.68,
69.70, 69.21, 66.43, 51.44, 47.09, 38.33, 37.82, 36.93, 35.67, 33.34, 32.04, 31.43,
31.19, 30.51, 25.20, 19.49, 16.82, 9.97, 8.95. MS (ESI+) m/z: 1689, 1711 [M+Na].
Compound 7b
[0097] As depicted in
Scheme 7, compound
13 was dissolved in a mixture of 2 ml DCM and 2ml TFA, and mixed for 1h. After completion
the product
13a was concentrated in vacuum and directly reacted in the next step.
[0098] CPT-ketone
2a (10 mg, 0.02 mmol, 1 equiv.) was dissolved in methanol (5 mL). TFA (5 drops) and
compound
13a (21 mg, 0.06 mmol, 3 equiv.) were added and the mixture was stirred for 2 hour at
40°C. The reaction progress was monitored by HPLC (ACN/H
2O). After completion, the crude was purified by preparative HPLC (ACN/H
2O) to give product
7b (8 mg, 50 % yield).
1H NMR (400 MHz, DMSO) δ 8.89 (s, 1H), 8.24 (dd, J = 18.5, 8.4 Hz, 2H), 7.95-7.87 (m,
1H), 7.78-7.67 (m, 2H), 6.54 (t, J = 5.8 Hz, 1H), 5.27 (d, J = 12.4 Hz, 2H), 3.72-3.35
(m, 16H), 3.12 (d, J = 6.3 Hz, 2H), 2.57 (s, 4H), 2.23 (t, J = 7.3 Hz, 2H), 2.10 (m,
1H), 2.02 (m, 1H), 1.89-1.53 (m, 10H), 0.85 (t, J = 7.0 Hz, 3H).
13C NMR (101 MHz, DMSO) δ 178.93, 174.79, 171.67, 162.02, 157.40, 154.92, 150.04, 149.70,
141.95, 136.93, 131.46, 129.50, 128.52, 125.86, 124.15, 102.24, 100.54, 95.33, 84.25,
81.26, 70.90, 70.72, 69.70, 69.34, 59.27, 56.59, 52.43, 38.36, 37.81, 36.94, 36.74,
32.65, 31.19, 30.68, 30.28, 29.98, 29.16, 28.54, 19.52, 16.76, 10.26, 9.60. MS (ESI+)
m/z: 943.
Compound 6
[0099] As depicted in
Scheme 8, compound
16 (20 mg, 0.082 mole, 2 eq.) and CPT-ketone
2a (10 mg, 0.041 mole, 1 eq.) were dissolved in toluene and catalytic amount of PTSA
was added. The reaction was heated to 110°C and stirred for 5 h. The reaction progress
was monitored by HPLC (ACN/H
2O). After completion, the crude was purified by preparative HPLC (ACN/H
2O) to give product
6 (15 mg, 75 % yield).
[0100] 1H NMR (400 MHz, CDCl
3) δ 8.40-8.14 (m, 2H), 7.85 (d, J = 1.4 Hz, 1H), 7.69 (m, 3H), 7.38-7.29 (m, 1H),
5.73 (m, 1H), 5.58-5.20 (m, 3H), 5.03-4.87 (m, 1H), 4.71-4.53 (m, 1H), 3.95 (m, 6H),
2.61-2.45 (m, 2H), 2.31-2.15 (m, 2H), 1.96-1.78 (m, 2H), 1.71-1.57 (m, 2H), 1.41 (s,
3H), 1.10-1.01 (t, 3H).
13C NMR (101 MHz, CDCl
3) δ 174.60, 158.12, 154.56, 153.33, 150.68, 148.71, 146.22, 139.89, 132.92, 131.76,
131.32, 130.76, 130.47, 129.61, 125.46, 124.71, 119.92, 114.80, 111.75, 111.22, 110.29,
108.94, 108.75, 98.84, 75.92, 74.66, 73.45, 71.98, 71.06, 67.08, 65.11, 57.15, 57.02,
52.05, 42.86, 39.37, 38.41, 36.66, 35.59, 34.56, 32.65, 32.33, 32.16, 31.36, 30.90,
30.42, 30.25, 30.06, 29.96, 27.94, 26.24, 25.13, 23.66, 23.42, 19.85, 17.47, 14.86,
8.54, 1.75.
Buffer Preparation Protocols:
[0101] Preparation of acetate buffers. The buffer solutions were prepared by addition of acetic acid solution (pH 4, 284.4
mL; pH 4.8, 87.2 mL; pH 5, 73.4 mL; pH 6 52.4 mL) and sodium hydroxide solution (1M,
50 mL) in 500 mL volumetric flask. The mixture was diluted with distilled water to
a final volume of 500 mL.
[0102] Preparation of PBS buffers. 1M NaH
2PO
4 solution was prepared by dissolving 13.8 g of NaH
2PO
4•H
2O in distilled H
2O to make a final volume of 100 mL. 1M Na
2HPO
4 solution was prepared by dissolving 14.2 g of Na
2HPO
4 in distilled H
2O to make a final volume of 100 mL. 1M NaH
2PO
4 (pH 7.0, 42.3 mL; pH 7.4, 22.6 mL) and 1M Na
2HPO
4 (pH 7.0, 57.7 mL; pH 7.4 mL) were mixed and diluted to 1L with H
2O.
[0103] Hydrolysis of compound 7 in buffer: pH 4.8, pH 6.0, pH 6.5, pH 7.0 and pH 7.4. A stock solution of
7 (10 mM) was prepared by dissolving 17.95 mg of the compound in 1 mL DMSO. A sample
of 25 µL from the stock solution was added to 75 µL DMSO, and the resulting solution
was added slowly while stirring to 840 µL of the appropriate buffer (pH 4.8, 6.0,
6.5, 7.0, or 7.4). Samples were taken at different times and analyzed by HPLC. The
hydrolysis percentage of the carrier was calculated based on the HPLC integration
ratio of the starting material and the corresponding hydrolytic products.
[3H]-Folic acid competition assay
[0104] KB HiFR cells (nasopharyngeal epidermal carcinoma cells overexpressing the folate
receptor) were growth in folate depleted RPMI + 10% FBS for 15 days in order to overexpress
the folate receptor. KB cells were growth in regular RPMI + 10% FBS. KB or KB HiFR
cells were seeded in 24 wells/plate, 1×10
6 cells/well in 500 µL of folate depleted RPMI without FBS. The cells were treated
as follow: 3 wells: 10 µL/wel of RMPI without FBS; 3 wells: 10 µL/well of cold folic
acid (100 µM, final concentration in each well 2 µM); 3 wells: 10 µL/well of compound
7 ([FA]=100 µM, final concentration in each well 2 µM); 3 wells: 10 µL /well of compound
7b ([FA]=100 µM, final concentration in each well 2 µM); 3 wells: 10 µL /well of CPT
([FA]=100 µM, final concentration in each well 2 µM). The cells were incubated for
3 hours at 37°C, 5% CO
2. After 3 h of incubation 10 µL of [
3H]-FA (5 µCi/mL, 10 µM, final concentration in each well 0.2 µM) were added to each
well. After 3 h of incubation the medium was collected (100 mL were kept and added
to 3 mL of scintillation fluid for counting, as reference), the cells harvested with
trypsin, added to the medium and the suspension was centrifuged. The supernatant was
discarded and the pellet washed 3 times with 3 mL of cold PBS. After the last wash,
each sample was treated overnight with 500 µL of 0.5N NaOH, followed by neutralization
with 0.5N HCl. After 30 minutes, 600 µL of the suspension was added to 3 mL of scintillation
fluid and the amount of radioactivity was determined by liquid scintillation counting.
Proliferation assay
[0105] KB HiFR were seeded in 96 well/plates, 2×10
3 cell/100 µL in folate depleted RPMI + 10% FBS. After 24 h incubation at 37°C, 5%
CO
2, 100 µL of serial dilutions (200-0.00002 µM CPT equivalent concentrations) of CPT
and CPT-derivatives were added to the wells (final concentration 100-0.00001 µM).
In the short exposure (pulse and chase) experiment the treatments were removed after
10 min incubation at 37°C, 5% CO
2, the cells were washed once with PBS and incubated with fresh folate depleted RPMI
+ 10% FBS for 72h. In the long exposure experiment, the cells were incubated for 72
h with the treatment. After 72 h incubation, 30 µL of mg/mL solution of MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium
bromide) in PBS were added to each well, and incubated for 5h. After incubation the
medium was removed and the cells lysed in 200 µL DMSO and kept under gentle stirring
protected from light for 20 min. Absorbance was measured at 560 nm and survival plotted
as percentage of untreated control.
Example 1.
[0106] Sodium difluoroalkyl ketal sulfinate
1 is a ketone-protected reagent, capable of reacting with a heteroarene C-H bond under
oxidative acidic conditions to produce the corresponding ketone derivative
I (Scheme 1). Deprotection of the ketal should occur
in situ under the hydrolytic acidic conditions of the reaction to afford the ketone functional
group. The heteroarene-ketone analogue can be readily masked through an acid-labile
hydrazone linkage (Patil
et al., 2012; Yang
et al., 2007)
(III) or a photo-labile ketal protecting group (Gravel
et al., 1983)
(II).
[0107] The synthesis of ketal sulfinate
1 was achieved in an analogous manner to that recently described for other sulfinate
salts
(Scheme 2). Thus, alkylation of ketal
1b by pyridine derivative
1a generated sulphone
1c. The latter was reacted with sodium mercaptoethanol to afford sulfinate salt
1. This synthesis could be easily performed on multi-gram scale to produce sulfinate
1 with good yields. Heteroarene difluoroalkylation by sulfinate salt
1 to produce the corresponding ketone derivative was initially established on caffeine
as a test substrate. Caffeine successfully reacted with sulfinate
1 through direct functionalization of its C-H bond to afford ketone derivative
Id in 87% yield.
[0108] Next, we sought to evaluate the functionalization-capability of sulfinate salt
1 on CPT
(2), TMZ
(3), bosutinib
(4) and MTX
(5), all heteroarene known antineoplastic drugs. CPT is a topoisomerase inhibitor with
limited options for bioconjugation through its tertiary hydroxyl group. TMZ is a cytotoxic
alkylating agent, which is considered as an untaggable compound due to the absence
of suitable functional group. Likewise, bosutinib, an approved tyrosine kinase inhibitor
based drug, has no functional group available for conjugation. MTX, an antifolate-based
chemotherapeutic drug, is another heteroarene with limited bioconjugation options
(Table 1). The four heteroarene drugs were successfully functionalized by sulfinate salt
1 to afford the corresponding ketone analogues in moderate to good yields. For CPT,
bosutinib and MTX, sulfinate salt
1 was able to selectively functionalize the heteroarenes at the most electron-deficient
C-H bond.
[0109] In order to find out whether the new derivatives retain their potency, the cytotoxicity
of the CPT-, TMZ- and bosutinib-ketone analogues was evaluated in comparison to that
of the parent drugs.
Fig. 2 shows representative cell-growth inhibition plots for each drug and its ketone analogue,
wherein the applied cell lines and the calculated IC
50s are presented in
Table 2.
Table 2. IC
50s values calculated from cell-growth inhibition assays for CPT, TMZ and bosutinib,
and their ketone analogues
| Drugs |
IC50 |
Cell line |
| CPT |
7 nm |
U-87 |
| CPT-ketone |
10 nm |
U-87 |
| TMZ |
36 µm |
U-251 |
| TMZ-ketone |
35 µm |
U-251 |
| Bosutinib |
17 µm |
SF-295 |
| Bosutinib-ketone |
17 µm |
SF-295 |
[0110] Remarkably, for three of the four drugs, tumor cell-growth inhibition assays showed
almost identical cytotoxicity (IC
50 values) for the ketone-derivatives and their native drugs. Functionalization of CPT,
TMZ and bosutinib using sulfinate salt
1, resulted in ketone analogues that retained their cytotoxic activity. However, the
ketone analogue of MTX completely lost its cytotoxicity. The assays were repeated
with several tumorous cell-lines and the obtained results were similar
(Figs. 3-4). These results indicate that it is possible for certain biologically relevant heteroarenes
to maintain their original activity, after C-H functionalization by sulfinate salt
1, at an appropriate position.
Example 2.
[0111] To determine the usefulness of the drug analogues produced harboring a ketone for
controlled release and bioconjugation, CPT-ketone
2a was selected for further evaluation. As presented in
Scheme 1, a ketone functional group can be masked either through an acid-labile hydrazone linkage
or with a photo-labile ketal protecting group. CPT-ketone
2a was masked with a photo-labile protecting group (Gravel
et al., 1983; Klan
et al., 2013) to produce ketal derivative
6 (Fig. 5). This derivative can be considered as prodrug form of CPT-ketone
2a. Irradiation of prodrug
6 with UV light over 2 hours under physiological conditions resulted in release of
CPT-ketone
2a (Fig. 5A). No release was observed without irradiation. The cytotoxicity of prodrug
6 was then evaluated in a standard cell-growth inhibition assay before and after irradiation
with UV light
(Fig. 5B). As expected, derivative
6 before irradiation exhibited typical prodrug behavior, with an IC
50 value of 350nM. Prodrug
6 after irradiation has showed significantly higher cytotoxicity with an IC
50 value of 10nM, similarly to that obtained for CPT-ketone
2a (IC
50=5nM). These results demonstrate how the newly installed ketone of the heteroarene
analogues can be used to obtain prodrugs with a photo-labile controlled-release pathway.
In this example, the prodrug was activated with UV light; however, there are analogues
protecting groups that can be removed through a visible or near infrared light (Lu
et al., 2003). To our knowledge, this is the first demonstration of a prodrug photo-activation,
which is based on unmasking of a ketone group (Klan
et al., 2013).
[0112] Next, we sought to evaluate the acid-labile hydrazone linkage, for controlled-release
and bioconjugation between CPT-ketone
2a and a targeting vehicle. Hydrolysis via an acid-labile linkage is a useful controlled-release
mechanism for cell-penetrating vehicles such as folic acid (FA) (Zhao
et al., 2008) conjugate
(Scheme 9). Thus, CPT-ketone
2a was reacted with a semicarbazide derivative of folic acid
(7a), via a semicarbazone linkage, to generate CPT-folic acid conjugate
7 with an acid-labile controlled-release mechanism (see Synthesis schemes and experimental
procedures). A PEG linker derivative was used as a spacer to connect between the folic
acid and CPT-ketone
2a.
Example 3.
[0113] To validate the release of CPT-ketone
2a from the folate conjugate
7, we monitored the hydrolysis of the semicarbazone linkage under various pHs (physiological
conditions - pH, 7.4; early endosome stage - pH, 6.5 and 6.0; and late endosome stages
- pH, 4.8). The kinetic plots of CPT-ketone
2a release are presented in
Fig. 6. The semicarbazone-base conjugate exhibited excellent selective hydrolysis under acidic
conditions. Fast release kinetics of CPT-ketone
2a was observed under acidic pHs, while no release at all was observed over 24 hr. at
physiological pH. Importantly, at relatively mild acid conditions (early-stage endosome
pH, 6.5), release of CPT-ketone
2a (about 50%) still effectively took place (Yang
et al., 2007).
[0114] The binding affinity of folate-conjugate
7 with FR receptors was evaluated with highly expressed-FR KB cells (HiFR-KB). CPT-PEG
derivative
7b, which lacks the folic acid was used as a control
(Fig. 7A). The obtained measurements showed 82% binding of conjugate
7 to FR receptors in comparison to that of free folic acid. Cytotoxicity evaluation
of CPT-folic acid conjugate
7 on HiFR KB cells results with relatively similar IC
50 values for CPT-ketone
2a and its folic acid conjugate
7 (Fig. 7B). CPT-PEG derivative
7b showed IC
50 value of 15-fold higher in comparison to that of conjugate
7. These results support the cell-penetrating ability of the folic acid-CPT conjugate
and
in vitro CPT-ketone controlled-release through the acid-labile semicarbazone linkage.
APPENDIX
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