U.S. patent application number 10/101731 was filed with the patent office on 2002-11-14 for compositions and methods for producing vascular occlusion.
Invention is credited to Noujaim, Antoine, Person, Roland Henryk, Stewart, Michael William.
Application Number | 20020168366 10/101731 |
Document ID | / |
Family ID | 22320484 |
Filed Date | 2002-11-14 |
United States Patent
Application |
20020168366 |
Kind Code |
A1 |
Stewart, Michael William ;
et al. |
November 14, 2002 |
Compositions and methods for producing vascular occlusion
Abstract
The present invention relates generally to methods and
compositions for targeting, delivering, and activating
platelet-dependent vascular occlusion agents. In particular,
antibodies carrying platelet binding agents are targeted to
hyperplastic cells or tissues, such as the vasculature of solid
tumor masses; the platelet binding agent then binds and activates
platelets, which in turn bind and activate other platelets. This
process results in the formation of a platelet-mediated
thrombus-causing vessel occlusion.
Inventors: |
Stewart, Michael William;
(St. Albert, CA) ; Person, Roland Henryk;
(Edmonton, CA) ; Noujaim, Antoine; (Edmonton,
CA) |
Correspondence
Address: |
CAHN & SAMUELS LLP
2000 P STREET NW
SUITE 200
WASHINGTON
DC
20036
US
|
Family ID: |
22320484 |
Appl. No.: |
10/101731 |
Filed: |
March 21, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10101731 |
Mar 21, 2002 |
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PCT/IB99/01809 |
Nov 10, 1999 |
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10101731 |
Mar 21, 2002 |
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09438944 |
Nov 12, 1999 |
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60108129 |
Nov 12, 1998 |
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Current U.S.
Class: |
424/146.1 ;
514/13.6; 514/13.8; 514/14.7; 514/14.9; 514/17.2; 514/19.1;
514/19.3; 514/54; 514/56; 514/8.1; 514/9.3 |
Current CPC
Class: |
B82Y 5/00 20130101; C07K
2317/34 20130101; C07K 16/28 20130101; A61K 38/00 20130101; C07K
16/30 20130101; A61P 7/04 20180101; C07K 16/3076 20130101; A61K
2039/505 20130101; A61K 47/6898 20170801; A61K 31/727 20130101;
A61P 35/00 20180101 |
Class at
Publication: |
424/146.1 ;
514/54; 514/56; 514/21 |
International
Class: |
A61K 039/395; A61K
031/727; A61K 031/739; A61K 031/726; A61K 038/36 |
Claims
We claim:
1. A composition for inducing thrombus formation comprising a
binding agent having a first binding component and a second binding
component, said first binding component comprising a binding region
for binding the binding agent to a pre-determined site; said second
binding component comprising a binding region for binding
platelets.
2. The composition of claim 1 wherein the first binding component
is an antigen binding site.
3. The composition of claim 2 wherein the first binding component
is one or more binding agents selected from the group consisting of
an antibody, a monoclonal antibody, a polyclonal antibody, a
humanized monoclonal antibody, a chimeric antibody, a single chain
antibody, a dimeric single chain antibody construct, a multimeric
single chain antibody construct, a peptide, a nucleic acid
sequence, a protein, a ligand, an oligonucleotide, conjugates that
include any one of the above, fragments or parts of any of the
above, and functional equivalents of any of the above.
4. The composition of claim 2 wherein the first binding component
binds to a neo-eptiope.
5. The composition of claim 1 wherein the second binding component
includes at least one of the components selected from the group
consisting of von Willebrand factor, osteopontin, fibrinogen,
fibrin, fibronectin, vitronectin, collagen, thrombospondin,
laminin, heparin, heparan sulfate, chondroitin sulfate,
phospholipase A2, matrix metalloproteinases, thrombin, glass,
sialyl-lewis X, fibulin-1, PECAM, ICAM-1, ICAM-2, p-selectin
ligand, MAC-1, LFA-1, portions of any of the above, and functional
equivalents of any of the above.
6. The composition of claim 1 further comprising a platelet binding
enhancer.
7. The composition of claim 6 wherein the platelet binding enhancer
comprises at least one of ristocetin, platelet microparticles, and
platelet membrane portions.
8. The composition of claim 1 further comprising a thrombus
formation modulator.
9. The composition of claim 8 wherein the thrombus formation
modulator is one or more enhancers selected from the group
consisting of inhibitors of fibrinolysis, inhibitors of
anti-coagulant proteins, and tissue factor pathway inhibitor.
10. The composition of claim 9 wherein the anti-coagulant proteins
include at least one of protein C, protein S, and anti-thrombin
III.
11. The composition of claim 9 wherein the inhibitors of
fibrinolysis include plasminogen activator inhibitors.
12. A method of inducing thrombus in vivo comprising: capturing
platelets at a selected site; inducing activation of the platelets;
and allowing a thrombus to form.
13. The method of claim 12 wherein inducing platelets to collect at
a pre-determined site comprises administering a targeting agent
that specifically binds platelets.
14. The method of claim 13 wherein the targeting agent is one or
more binding agents selected from the group consisting of an
antibody, a monoclonal antibody, a polyclonal antibody, a humanized
monoclonal antibody, a chimeric antibody, a single chain antibody,
a dimeric single chain antibody construct, a multimeric single
chain antibody construct, a peptide, a nucleic acid sequence, a
protein, a ligand, an oligonucleotide, conjugates that include any
one of the above, fragments or parts of any of the above, and
functional equivalents of the above.
15. The method of claim 14 wherein the targeting agent is a
bifunctional binding agent.
16. The method of claim 15 wherein the bifunctional binding agent
comprises a targeting component and a platelet-specific
component.
17. The method of claim 16 wherein the platelet-specific component
comprises at least one of the components selected from the group
consisting of von Willebrand factor, osteopontin, fibrinogen,
fibrin, fibronectin, vitronectin, collagen, thrombospondin,
laminin, heparin, heparan sulfate, chondroitin sulfate,
phospholipase A2, matrix metalloproteinases, thrombin, glass,
sialyl-lewis X, fibulin-1, PECAM, ICAM-1, ICAM-2, p-selectin
ligand, MAC-1, LFA-1, portions of any of the above, and functional
equivalents of any of the above.
18. The method of claim 16 wherein the bifunctional binding agent
comprises a moiety selected from one or more of the following:
biotin mimetics, homophyllic peptides, and human Fc fragments.
19. The method of claim 16 wherein the targeting component binds to
a ligand/receptor complex.
20. The method of claim 19 wherein the ligand/receptor complex is a
growth factor/growth factor receptor.
21. The method of claim 20 wherein the growth factor/growth factor
receptor is VEGF/VEGF receptor or a peptide mimetic of VEGF or
VEGF-like molecule bound to the VEGF receptor.
22. A kit for inducing thrombus formation comprising a binding
agent for targeting a pre-determined site and at least one of the
following: a binding agent for binding platelets; a ligand for
binding the binding agent; a ligand conjugate; an anti-ligand for
binding the ligand or the ligand conjugate; a platelet binding
enhancer; a thrombus formation modulator; a complement cascade
component; a complement cascade component inducer; and a binding
agent for binding platelets that includes an anti-ligand.
23. The kit of claim 22 wherein the binding agent for targeting a
pre-determined site includes a binding component for binding
platelets.
24. The kit of claim 22 wherein the binding agent for targeting a
pre-determined site includes a ligand.
25. A method of treating cancer comprising: capturing platelets at
a selected vascular site near or on a tumor; inducing activation of
the captured platelets and forming a thrombus; and occluding the
vascular site with the thrombus.
26. A method of treating cancer comprising: administering a binding
agent capable of binding platelets binding platelets to the binding
agent to form captured platelets; inducing activation of the
captured platelets and forming a thrombus, whereby formation of the
thrombus provides a therapeutic benefit.
27. A method of treating an undesirable condition comprising:
inducing platelets to collect at a pre-determined site; activating
the platelets, thereby forming a therapeutically beneficial
thrombus.
28. A method of inducing thrombus formation comprising cooling a
platelet suspension to between about 4.degree. C. and about
15.degree. C.; administering the cooled platelet suspension;
capturing the platelets at a pre-determined site; inducing
activation of the platelets; and allowing a thrombus to form.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Not Applicable
FEDERAL SPONSORSHIP
[0002] Not Applicable
BACKGROUND OF THE INVENTION
[0003] 1. Field of the Invention
[0004] The present invention is directed to compositions and
methods for producing a therapeutic benefit by producing vascular
occlusion using platelet activation as the initiating event.
Compositions and methods of the invention involve targeting
platelets to a site, such as a tumor site, using a binding agent,
such as a bi-functional molecule, a portion of which binds to the
site and another portion of which binds or immobilizes a platelet
binding agent, such as circulating von Willebrand Factor (VWF).
[0005] 2. Description of Related Art
[0006] Platelets function in the body to limit blood loss in the
event of vascular damage. Normally, platelets circulate throughout
the body with other cellular components of blood, bathed in a
mixture of various plasma proteins, many of which play key roles in
the clotting process. Upon exposure of vascular sub-endothelium, a
complex series of events occurs to limit the loss of blood from the
damaged vessel. Platelets contacting components of the exposed
sub-endothelium: 1) bind and adhere, 2) spread across the exposed
surface, 3) activate as evidenced by release of granule contents,
4) aggregate and recruit other platelets from the blood stream, and
5) form an efficient plug stemming the flow of blood from the
vessel.
[0007] In contrast to the coagulation cascade, i.e., the sequential
conversion of coagulation protein zymogens into active enzymes and
which ultimately ends in the conversion of fibrinogen to fibrin,
platelets bind specifically to the damaged area and are held
together by bridging molecules that bind to specific receptors on
the platelet surface. The initial bridging between platelets and
the sub-endothelium is dependent on the interaction between the
glycoprotein Ib (GPIb) receptor on the surface of the platelet and
VWF in the subendothelium (i.e., immobilized VWF). This interaction
in itself is unique since normal platelets circulating in the blood
contacting soluble VWF are not activated, nor do they bind to the
soluble VWF. In vitro experimentation has confirmed that
immobilization of the soluble VWF to a surface facilitates binding
and activation of platelets (Stewart et al, British Journal of
Haematology, 97:231-9,1997). Upon activation of the platelet an
additional receptor, glycoprotein IIb/IIIa (GPIIb/IIIa), is altered
and enables the binding of several plasma proteins, thereby
promoting platelet/platelet binding (Savage et al, Journal of
Biological Chemistry, 267:11300-6,1992). In addition to fibrinogen,
soluble VWF binds to the activated GPIIb/IIIa receptor, in turn
becoming immobilized and capable of binding other platelets via
GPIb and GPIIb/IIIa.
[0008] Hyperactive platelets induce thrombus formation at
inopportune times resulting in reduced blood supply to key organs
and tissues. A prime example is thrombus formation induced by blood
flowing through a stenotic (narrowed) vessel supplying the heart.
Reduction of the flow of blood to the heart muscle leads to
infarction and eventually heart attack (cardiac cell death).
Cerebral ischemia (transient ischemic attack, TIA; stroke) occurs
when an embolus or thrombus occludes blood vessels feeding the
brain.
[0009] Other pathological states exist which are caused by platelet
activation due to an antibody-mediated process. Heparin-induced
thrombocytopenia (HIT) is characterized by a dramatic loss in
platelet numbers and thrombus formation at sites of pre-existing
pathology. Patients receiving heparin, as an anticoagulant to
promote blood flow, occasionally (1 to 5% of all patients receiving
un-fractionated heparin) produce an antibody that binds to heparin
in complex with a platelet granule protein (Kelton et al, Blood,
83:3232-9, 1994). The binding of the antibody to the
heparin/protein complex on the surface of the platelet induces
rapid platelet activation and localized thrombus formation. This in
turn leads to infarction of the affected area.
[0010] Thrombosis is a well-described consequence of cancer.
Controversy exists as to whether the presence of a hyper-coagulable
state is predictive of cancer. Many studies have been conducted
demonstrating a prothrombotic tendency with most neoplasias. It has
been suggested that thrombosis is the most frequent complication in
patients with overt malignant disease.
[0011] Concern has arisen regarding the potential risk of enhancing
thromboembolic disease as a result of current therapy regimens
(surgical or chemotherapeutic). In some instances, oral
anticoagulation is initiated to prevent possible thrombotic
complications. A key to the development of successful anti-tumor
agents is the ability to design agents that will selectively kill
tumor cells, while exerting relatively little, if any, untoward
effects against normal tissues. This goal has been elusive to
achieve in that there are few qualitative differences between
neoplastic and normal tissues. Because of this much research over
the years has focused on identifying tumor-specific "marker
antigens" that can serve as immunological targets both for
chemotherapy and diagnosis. Many tumor-specific or
quasi-tumor-specific (tumor-associated) markers have been
identified as tumor cell antigens that can be recognized by
specific antibodies.
[0012] Unfortunately, it is generally the case that tumor specific
antibodies will not in and of themselves exert sufficient
anti-tumor effects to make them useful in cancer therapy. In
contrast with their efficacy in lymphomas, immunotoxins have proven
to be relatively ineffective in the treatment of solid tumors such
as carcinomas. The principal reason for this is that solid tumors
are generally impermeable to antibody-sized molecules: specific
uptake values of less than 0.001% of the injected dose/g of tumor
are not uncommon in human studies. Furthermore, antibodies that
enter the tumor mass do not distribute evenly for several reasons.
First, the dense packing of tumor cells and fibrous tumor stromas
present a formidable physical barrier to macro-molecular transport
and combined with the absence of lymphatic drainage create an
elevated interstitial pressure in the tumor core which reduces
extravasation and fluid convection. Second, the distribution of
blood vessels in most tumors is disorganized and heterogeneous; as
a result, some tumor cells are separated from extravasating
antibody by large diffusion distances. Third, all of the antibody
entering the tumor may become absorbed in perivascular regions by
the first tumor cells encountered, leaving none to reach tumor
cells at more distant sites.
[0013] One approach would be to target cytotoxic agents or
thrombus-inducing agents to the vasculature of the tumor rather
than to the tumor.
[0014] The present inventors propose that this approach offers
several advantages over direct targeting of tumor cells. First, the
target cells are directly accessible to intravenously administered
therapeutic agents permitting rapid localization of a high
percentage of the injected dose. Second, since each capillary
provides oxygen and nutrients for thousands of cells in its
surrounding cord of tumor, even limited damage to the tumor
vasculature could produce an avalanche of tumor cell death.
Finally, the outgrowth of mutant endothelial cells lacking the
target antigen is unlikely because they are normal cells.
SUMMARY OF THE INVENTION
[0015] The present invention relates to therapeutic methods and
compositions for targeting tissues and/or organs, and associated
vasculature, which are hyperplastic or neoplastic in nature, using
agents that induce thrombus formation via localized platelet
activation. The composition uses an agent for capturing platelets
at a pre-determined site and an agent for activating the captured
platelets. In some embodiments of the invention, a single agent
both captures and activates the platelets. The method utilizes
localized platelet collection and activation, which produces
subsequent thrombus formation, thereby limiting the blood supply to
the target area, without inducing a generalized or systemic
pro-thrombotic state.
[0016] The invention also may employ bifunctional agents having a
targeting component capable of binding tumor-associated antigens
and/or antigens expressed on tumor vasculature, and a
platelet-specific recognition component capable of binding and
capturing platelets.
[0017] Purposeful induction of thrombosis in a cancer patient
appears, at first glance, to be counter-intuitive, since inducing
thrombosis in a cancer patient is well known to contribute
significantly to patient morbidity and mortality.
[0018] The present invention, targeted platelet-mediated occlusion,
is based on the site-specific induction of thrombosis, utilizing
the body's natural capacity to produce a thrombus in response to
immobilized von Willebrand factor (VWF) or other locally acting
platelet activation agents. Although VWF circulates in the blood
stream in soluble form, it is not until the molecule is exposed as
part of the subendothelium or binds to exposed collagen from the
subendothelium that it is capable of capturing platelets and
inducing platelet activation.
[0019] Using a bifunctional targeting agent directed toward a
pre-determined site or molecule (e.g. a tumor-specific or
tumor-associated antigen, ligand/receptor complex), VWF is
immobilized at the site, thereby inducing localized platelet
capture and activation leading to thrombosis and cessation of blood
flow to the local area. Cells, including tumor cells, diminish or
die as a result of loss of localized blood flow. This approach
avoids systemic platelet activation and thrombosis; relying on the
fact that immobilized VWF (not soluble VWF) will capture and
activate a circulating platelet. Thus, the methods and compositions
of the present invention are an indirect means of treating a
pathological condition, such as cancer or hyperplastic cells.
[0020] In a manner similar to an existing pathological condition
(i.e. Heparin-Induced Thrombocytopenia, HIT), localized platelet
activation can be enhanced via an Fc-mediated process by
incorporating a human Fc fragment into the bifunctional
anti-tumor-associated or tumor-specific antigen or ligand/receptor
complex targeting agent. Platelet activation in HIT syndrome
results in localized thrombosis and cessation of blood flow to the
affected area. This leads to death of the local tissue.
[0021] The extent and degree of site-specific thrombosis can be
controlled in a variety of ways. Inhibition of platelet activation
through the use of anti-platelet agents (e.g. GPIIb/IIIa
inhibitors, aspirin, dipyridamole, etc.) decreases the propensity
to induce a thrombus, in a defined, titratable manner. Altering
local blood flow, blood pressure and tissue temperature can also
serve as means of controlling local platelet activation to a
stimulus.
[0022] Typical vascularized tumors are the solid tumors,
particularly carcinomas, which require a vascular component for the
provision of oxygen and nutrients. Exemplary solid tumors to which
the present invention is directed, include, but are not limited to,
carcinomas of the lung, breast, ovary, stomach, pancreas, larynx,
esophagus, testes, liver, parotid, biliary tract, colon, rectum,
cervix, uterus, endometrium, kidney, bladder, prostate, thyroid,
squamous cell carcinomas, adenocarcinomas, small cell carcinomas,
melanomas, gliomas, neuroblastomas, and the like.
[0023] A preferred method of the invention includes preparing a
binding agent, such as an antibody or antibody-like molecule, that
recognizes an antigen or other ligand associated with the vascular
endothelial cells of the vascularized tumor mass; linking or
operatively attaching the antibody to the selected agents to form
an antibody-agent conjugate and introducing the antibody-agent
conjugate into the bloodstream of an animal, such as a human
patient or a test animal. As used herein however, the term
"antibody" is intended to refer broadly to any immunologic binding
agent such as IgG, IgM, IgA, IgE, F(ab').sub.2, a univalent
fragment such as Fab', Fab, Dab, as well as engineered antibodies
such as single chain antibodies, covalently-linked single chain
antibodies, recombinant antibodies, humanized antibodies,
bispecific antibodies, and the like.
[0024] As noted above, a solution to the problem of poor
penetration of antibodies into solid tumors is to attack the
endothelial cells (EC) lining the blood vessels in the tumor. This
approach offers several advantages over direct targeting of tumor
cells. First, the target cells are directly accessible to
intravenously administered therapeutic agents permitting rapid
localization of high percentage of the injected dose. Second, since
each capillary provides oxygen and nutrients for thousands of cells
in its surrounding `cord` of tumor even limited damage to the tumor
vasculature could produce extensive tumor cell death. Finally,
endothelial cells are similar in different tumors, making it
feasible to develop a single reagent for treating numerous types of
cancer.
[0025] An example of one such reagent would be that which
recognizes a complex of VEGF and its receptor. Such an agent would
be fashioned to uniquely recognize the combination of VEGF and the
VEGF receptor, having little or no effect on either the ligand
(VEGF) or the receptor.
DESCRIPTION OF THE DRAWINGS
[0026] Not Applicable
DETAILED DESCRIPTION OF THE INVENTION
[0027] The present invention provides compositions and methods for
capturing platelets at a pre-determined site, activating the
platelets, and harnessing the natural function of platelets to
achieve a beneficial therapeutic result. In accordance with the
present invention, platelets may be targeted to a specific site,
then the natural ability of platelets to induce thrombus formation
may be used to interrupt, disrupt, or reduce blood flow at the
site. Reduced blood flow concomitantly reduces nutrient supply to a
disease or condition agent, such as a tumor, so the size of the
disease agent is diminished. It is clear that reducing the size of
a tumor is an obvious therapeutic benefit.
[0028] The present invention also provides compositions and methods
for indirectly treating a disease or condition by disrupting blood
flow to a site or locus of the disease. In this embodiment of the
invention. Blood flow is disrupted by positioning platelets at a
pre-determined site near but not on the site of the disease;
activating the platelets; and allowing the natural function of the
platelets, e.g., thrombus formation, to reduce and/or eliminate the
nutrient supply to the disease site.
[0029] The present invention also includes targeting platelets to a
pre-determined tissue capable of being selectively targeted, e.g.,
hyperplastic tissue, and activating the platelets. Activating the
platelets at the pre-selected site causes a therapeutic benefit by
reducing the nutrient supply to the tissue or site.
[0030] The present invention provides compositions and methods for
inducing thrombus formation by capturing platelets at a selected
site, inducing activation of the platelets, and allowing a thrombus
to form. By capturing platelets on tumor endothelial cells (an
example of a selected site), the compositions and methods of the
present invention may be used to treat cancer. Furthermore, the
compositions and methods of the present invention provide a
therapeutic benefit to the recipient of the composition.
[0031] The present invention also provides compositions and methods
for treating cancer by inducing platelets to collect at a
pre-determined site, and activating the platelets, thereby forming
a therapeutically beneficial thrombus.
[0032] The present invention also provides compositions that
include a binding agent having a first binding component and a
second binding component, said first binding component targeting
the binding agent to the pre-determined site, e.g., comprising a
binding region for binding the binding agent to the pre-determined
site; said second binding component comprising a binding region for
binding platelets. Such compositions include bifunctional binding
agents having an antigenic determinant and a platelet binding
site.
[0033] Compositions according to the present invention may also
include a ligand as a targeting agent, and an anti-ligand for
binding the ligand and binding platelets.
[0034] Compositions according to the invention may also include one
or more of the following: one or more platelet binding modulators
(e.g., inhibitors or enhancers), one or more thrombus formation
controllers or modulators, or one or more complement cascade
components.
[0035] Methods according to the invention may also include one or
more of the following: administering a binding agent capable of
capturing platelets at a pre-determined site; inducing activation
of the captured platelets; administering a bifunctional binding
agent having an antigenic determinant and a platelet binding site;
controlling thrombus generation by altering the temperature of one
or more compositions of the invention; and/or altering the
temperature at the pre-selected site.
[0036] Methods according to the invention may further include one
or more of the following: administering one or more platelet
binding modulators, administering one or more thrombus formation
modulators, or administering one or more complement cascade
components.
[0037] The present invention also includes a kit including a
binding agent for targeting a pre-determined site and at least one
of the following: a binding agent for binding platelets; a ligand
for binding the binding agent; a ligand conjugate; an anti-ligand
for binding the ligand or the ligand conjugate; a platelet binding
modulator (enhancer and/or inhibitor); a thrombus formation
modulator; a complement cascade component; a complement cascade
component inducer; and a binding agent for binding platelets that
includes an anti-ligand. The kit may include a bifunctional binding
agent, and/or a binding agent-ligand conjugate, and/or a
platelet-binding agent--anti-ligand conjugate.
[0038] The compositions and methods of the present invention
include any mechanism of delivering a composition to the
pre-selected site, including but not limited to systemically,
locally, orally, or topically.
[0039] In accordance with some embodiments of the invention,
binding agents are used to capture platelets at a predetermined
site.
[0040] Definitions:
[0041] As used herein, a binding agent or targeting moiety refers
to any chemical or biological molecule for binding one substance to
another. Typically the binding agent binds a defined population of
cells, typically hyperplastic tissue, or a cancer cell. A
molecule's function as a binding agent should not be limited by the
structural mechanism of attachment. For example, a binding agent
may bind a receptor, an antigenic determinant or epitope, an
enzymatic substrate, or other biological structure linking the
binding agent to a target cell or cell population. The binding
agent may be a conjugate, and includes but is not limited to
immunological conjugates, chemical conjugates (covalent or
non-covalent), fusion proteins, and the like.
[0042] As used herein, a ligand-binding agent refers to a
complementary set of molecules that demonstrate specific binding
for each other. Preferably, a ligand binding agent is a targeting
and a platelet binding agent. A ligand/anti-ligand pair generally
binds with relatively high affinity, and for this reason, may be
highly desirable for use with the present invention. A very well
known ligand/anti-ligand pair is biotin and avidin. As used herein,
avidin refers to avidin, streptavidin, neutravidin, derivatives and
analogs thereof, and functional equivalents thereof. Avidin may
bind biotin in a multivalent or univalent manner. Other exemplary
ligand/anti-ligand pairs include, but are not limited to,
homophyllic peptides, "leucine zippers", zinc finger proteins/ds
DNA fragment, enzyme/inhibitor, hapten/antibody, ligand/receptor,
growth factor/growth factor receptor.
[0043] As used herein, a selected site, a pre-determined sited,
targeting, and pre-targeting all refer to the location where the
accumulation of platelets will provide a therapeutically beneficial
result. Typically this involves target site localization of a
targeting moiety. Such sites include but are not limited to the
vasculature of solid tumors, tumor associated antigens, tumor
specific antigens, hyperplastic tissues, and/or the extracellular
matrix or subendothelium that is adjacent to or comprises any of
these tissues or cells. The binding agent may be directed against
any antigen of clinical significance, but preferably is directed
against a tumor-specific or tumor-associated antigen.
[0044] As used herein, thrombus refers to any semi-solid aggregate
of blood cells enmeshed in fibrin and clumps of platelets. In
accordance with the invention, a thrombus is formed as a direct
result of activated platelet accumulation at the pre-determined
site. Thrombosis refers to the formation of a thrombus, typically
within a blood vessel. Thrombogenic refers to substances that tend
to cause thrombosis, or thrombus-forming.
[0045] As used herein, therapeutically beneficial, providing a
therapeutic benefit or the like refers to a desirable change in the
physiology of the recipient animal. In a preferred embodiment of
the invention, the change is detectable. In accordance with the
invention, any biological mechanism that involves activated
platelets or platelet modulation may be used or harnessed to
achieve a beneficial therapeutic result. Exemplary therapeutic
benefits produced in accordance with the present invention include
but are not limited to forming a thrombus, forming a
platelet-mediated occlusion, eliminating a hyperplastic tissue or
cells, eliminating a tumor and/or tumor cells, diminishing the size
of a hyperplastic tissue, diminishing the size of a tumor, causing
the hyperplastic tissue or tumor to become susceptible to
additional therapies such as chemotherapy and/or radiation therapy
or the like, and starving or reducing the nutrient supply to a
hyperplastic tissue or cancer.
[0046] As used herein, "administering" refers to any action that
results in exposing or contacting a composition containing a
binding agent with a pre-determined cell, cells, or tissue,
typically mammalian. Administering may be conducted in vivo, in
vitro, or ex vivo. For example, a composition may be administered
by injection or through an endoscope or catheter. Administering
also includes the direct application to cells of a composition
according to the present invention. For example, during the course
of surgery, tumor or hyperplastic cells may be exposed. In
accordance with an embodiment of the invention, these exposed cells
(or tumors) may be exposed directly to a composition of the present
invention, e.g., by washing or irrigating the surgical site, and/or
the cells.
[0047] As used herein, VEGF refers to all members of the Vascular
Endothelial Growth Factor family. As used herein, VEGF receptor
refers to all members of the Vascular Endothelial Growth Factor
Receptor family, including but not limited to FLT1/VEGFR,
FLK1/KDR/VEGFR2, and FLT4/VEGFR3. As used herein "causing a tissue
or tumor to become susceptible to additional therapies" refers to
inducing a condition of low nutrient and/or oxygen supply to the
tissue or tumor, through the method of the present invention
including, but not limited to, forming a thrombus in the tumor
vasculature and/or causing a reduced blood supply to the tumor.
[0048] As noted above, the invention employs a binding agent. In
accordance with the present invention, the binding agent may
function as a targeting agent, a platelet-binding agent, a
platelet-activating agent, and/or as a portion of a conjugate for
targeting, platelet binding, or platelet activation. In a preferred
embodiment of the invention, the binding agent is bifunctional,
preferably functioning as a targeting agent and as a
platelet-binding agent.
[0049] The preferred binding and/or targeting agent is an antibody
or antibody-like molecule, preferably a monoclonal antibody. A
preferred binding agent is an antibody that binds hyperplastic
tissue or cells, including but not limited to a tumor, a tumor
associated antigen (TAA), or a tumor specific antigen (TSA). In a
preferred embodiment of the invention, the binding agent (i.e.,
antibody or antibody-like molecules) would bind to the VEGF/VEGF
receptor complex. In a further preferred embodiment of the
invention, the antibody or antibody-like molecule binding would
recognize a neo-epitope (cryptic or previously unavailable epitope)
formed by the interaction of a ligand and its receptor (e.g.,
growth factor/growth factor receptor interaction). In a further
preferred embodiment of the invention, the binding of the antibody
or antibody-like molecules to the ligand/receptor complex (e.g.,
growth factor/growth factor receptor complex) would not affect the
function of either the ligand (e.g., growth factor) or the receptor
(e.g., growth factor receptor).
[0050] Exemplary binding agents include, but are not limited to:
monoclonal antibodies; polyclonal antibodies; native or naked
antibodies; chimeric monoclonal antibodies; humanized antibodies;
genetically engineered monoclonal antibodies; fragments of
antibodies, selected from the group consisting of F(ab).sub.2,
F(ab').sub.2, Fab, F(ab'), Dab, Fv, sFv, Fc, and minimal
recognition unit; single chains representing the reactive portion
of monoclonal antibodies ("SC-Mab"); modified antibodies, e.g.
activated or chemically-activated antibodies; tumor-binding
peptides; a protein, including receptor proteins; peptide;
polypeptide; glycoprotein; lipoprotein, or the like, e.g., growth
factors; lymphokines and cytokines; enzymes, immune modulators;
hormones, for example, somatostatin; a ligand (with its
complementary anti-ligand pair); oligonucleotides; any of the above
joined to a molecule that mediates an effector function; and mimics
or fragments of any of the above. Analogs of the above-listed
targeting moieties that retain the capacity to bind to a defined
target cell population may also be used within the claimed
invention. In addition synthetic targeting moieties may be
designed.
[0051] Exemplary binding agents are those that bind to at least one
epitope on an antigen or the like disclosed in Nustad, et al, Tumor
Biology, 17:196-219 (1996) and Nap, et al, Tumor Biology,
17:325-331 (1996); Tumor Biology, 19:390-420 (1998); and Tumor
Biology, 19:21-29 (1998).
[0052] Monoclonal antibodies useful in the practice of the present
invention include whole antibody and fragments thereof. Such
monoclonal antibodies and fragments are producible in accordance
with conventional techniques, such as hybridoma synthesis,
recombinant DNA techniques and protein synthesis. Useful monoclonal
antibodies and fragments may be derived from any species (including
humans) or may be formed as chimeric proteins, which employ
sequences from more than one species. These include but are not
limited to the hybridoma technique originally described by Kohler
and Milstein [Nature, 256:495-497 (1975)]; the human B-cell
hybridoma technique [Kozbor, et al., Immunology Today, 4:72
(1983)]; and the EBV transformation technique [Cole, et al.,
Monoclonal Antibodies and Cancer Therapy, Alan R. Liss, Inc., pp.
77-96 (1985)].
[0053] Exemplary proteins useful in the practice of this invention
include but are not limited to proteins corresponding to known cell
surface receptors (including low density lipoproteins, transferrin
and insulin), fibrinolytic enzymes, anti-HER2, platelet binding
proteins such as annexins, and biological response modifiers
(including interleukin, interferon, erythropoietin and
colony-stimulating factor). Oligonucleotides, e.g., anti-sense
oligonucleotides that are complementary to portions of target cell
nucleic acids (DNA or RNA), are also useful as targeting moieties
in the practice of the present invention. Oligonucleotides binding
to cell surfaces are also useful.
[0054] Any growth factor may be used for such a targeting purpose
so long as it binds to a tumor or tumor-associated endothelial
cell. Suitable growth factors for targeting include but are not
limited to VEGF/VPF (vascular endothelial growth factor/vascular
permeability factor), FGF (which, as used herein refers to the
fibroblast growth factor family of proteins), TGFb (transforming
growth factor b), EGF and pleitotropin. Preferably the growth
factor receptor to which the targeting factor binds should be
present at a higher concentration on the surface of
tumor-associated endothelial cells than on non-tumor associated
endothelial cells. Most preferably, the growth factor receptor to
which the targeting growth factor binds should further be present
at a higher concentration on the surface of tumor-associated
endothelial cell than on any non-tumor-associated cell type.
[0055] Functional equivalents of the aforementioned molecules are
also useful as targeting moieties of the present invention. One
targeting moiety functional equivalent is a "mimetic" compound, an
organic chemical construct designed to mimic the proper
configuration and/or orientation for targeting moiety-target cell
binding. Another targeting moiety functional equivalent is a short
polypeptide designated as a "minimal" polypeptide, constructed
using computer-assisted molecular modeling and mutants having
altered binding affinity, which minimal polypeptides exhibit the
binding affinity of the targeting moiety.
[0056] The Fv fragments of immunoglobulins have many significant
advantages over whole immunoglobulins for the purpose of targeted
tumor therapy, including better lesion penetration on solid tumor
tissue and more rapid blood clearance, as well as potentially lower
Fc-mediated immunogenicity. An exemplary single-chain Fv (scFv)
binding agent may be engineered from the genes isolated from the
variable regions of a tumor antibody. For example, a scFv binding
agent may comprise a genetically engineered recombinant fusion
protein that comprises a heavy chain (Vh) and a light chain (V1)
variable domain connected by an artificial linker and an effector
domain.
[0057] An embodiment of the invention involves a targeting agent
having a binding affinity for a marker found, expressed, accessible
to binding, or otherwise localized on the cell surfaces of
tumor-associated vascular endothelial cells as compared to normal
non-tumor-associated vasculature. Further, certain markers for
which a targeting agent has a binding affinity may be associated
with the tumor-associated vasculature rather than on the
tumor-associated endothelial cells, themselves. For example, such
markers may be located on basement membranes or tumor-associated
connective tissue.
[0058] In preferred embodiments of the invention, it will be
desirable to prepare and employ an antibody having a relatively
high degree of tumor vasculature selectivity, which might be
expressed as having little or no reactivity with the cell surface
of normal endothelial cells as assessed by immunostaining of tissue
sections. Bi-specific antibodies useful in the practice of this
aspect of the invention, therefore, will have a dual specificity
recognizing a selected tumor cell surface antigen on the one hand,
and on the other hand, recognizing a selected platelet specific
agent.
[0059] Any composition that includes a binding and/or targeting
agent according to the invention may be used to initiate in vivo
therapeutic benefit, thrombus formation, and/or cell killing or
diminution. The composition may include one or more adjuvants, one
or more carriers, one or more excipients, one or more stabilizers,
one or more permeating agents (e.g., agents that modulated movement
across a cell membrane), one or more imaging reagents, one or more
effectors; and/or physiologically acceptable saline. Generally,
adjuvants are substances mixed with an immunogen in order to elicit
a more marked immune response. The composition may also include
pharmaceutically acceptable carriers. Pharmaceutically acceptable
carriers include but are not limited to saline, sterile water,
phosphate buffered saline, and the like. Other buffering agents,
dispersing agents, and inert non-toxic substances suitable for
delivery to a patient may be included in the compositions of the
present invention. The compositions may be solutions suitable for
administration, and are typically sterile and free of undesirable
particulate matter. The compositions may be sterilized by
conventional sterilization techniques.
[0060] In a preferred embodiment of the invention, a suitable
composition includes a binding agent that binds to an antigen.
Typically, the tumor antigen recognized by the bi-specific
antibodies employed in the practice of the present invention will
be one that is located on the cell surfaces of the tumor being
targeted. A large number of solid tumor-associated antigens have
now been described in the scientific literature and the preparation
and use of antibodies that bind these antigens are well within the
skill of the art; of course, the tumor antigen that is ultimately
selected will depend on the particular tumor to be targeted.
[0061] Exemplary antigens useful as targets in accordance with the
present invention include, but are not limited to antigens
associated with cancer including but is not limited to lung, colon,
rectum, breast, ovary, prostate gland, head, neck, bone, immune
system, or any other anatomical location. Exemplary antigens and/or
pre-determined sites include but are not limited to GM2, Tn, sTn,
Thompson-Friedenreich antigen, Glogo H, Le(y), MUC1, MUC2, MUC3,
MUC4, MUC5AC, MUC5B, MUC7, DEA, hCGbeta, HER2/neu, HER2, PSA, PSMA,
KSA, CA 72-4, CA 19-9, CA 15-3, CA 125, TAG-72. The subject may be
a human or animal subject. Other illustrative tumors and tumor
markers are listed in U.S. Pat. Nos. 5,075,218 and 5,776,427.
[0062] As noted above, a composition or method of the present
invention includes a platelet specific agent or component.
Exemplary platelet specific agents or components include but are
not limited to von Willebrand factor (VWF), osteopontin,
fibrinogen, fibrin, fibronectin, vitronectin, collagen,
thrombospondin, laminin, heparin, heparan sulfate, chondroitin
sulfate, phospholipase A2, matrix metalloproteinases (MMPs),
thrombin, glass, sialyl-lewis X, fibulin-1, platelet-endothelial
cell adhesion molecule (PECAM), intercellular adhesion molecule 1
(ICAM-1), ICAM-2, MAC-1, LFA-1, PSGL-1, either singly or in
combination.
[0063] As noted above, a composition or method of the present
invention may include a platelet-mediated occlusion enhancer. The
platelet-mediated occlusion enhancer may be a moiety that forms a
portion of a bifunctional molecule as noted above, may be an
ingredient in a composition according to the invention, and/or may
be administered separately from a composition according to the
invention. Those skilled in the art will recognize that it may be
desirable to include or use a platelet-mediated occlusion enhancer
when the individual receiving the therapy is in a state of
compromised haemostasis. Under such conditions, the individual
receiving the therapy has a propensity to bleed due to a
pathological process that may have been acquired or is congenital
in nature. Since the utility of the present invention is reliant
upon the formation of a thrombus in the tissue or tumor vasculature
after targeting platelets to the area, use of methods that augment
platelet activation and/or the coagulation process could compensate
for the individuals hemorrhagic tendencies. Examples of such
conditions include, but are not limited to, haemophilia, von
Willebrand's disease, coagulation factor deficiencies, Glanzmann's
thrombasthenia, and Bernard Soulier Syndrome.
[0064] Exemplary platelet-mediated occlusion enhancers include but
are not limited to ristocetin, thrombin, heparin-induced
thrombocytopenia (HIT) antibodies or portions thereof,
antiphospholipid antibodies (APA) or portions thereof, whole
antibody molecules via an Fc-mediated mechanism, anti-LIBS
antibodies, anti-CD9 antibodies, epinephrine, thrombin receptor
activating peptide (TRAP), cathepsin G, elastase, arachidonate,
platelet activating factor (PAF), thromboxane A2 (TxA2), TxA2
mimetics, phospholipase A2 (PLA2), activators of protein kinase C
(PKC), adenosine diphosphate (ADP), inducers of cyclo-oxygenase 1
(COX-1), inducers of cyclo-oxygenase 2 (COX-2), collagen, VWF,
matrix metalloproteinases (MMPs), heparin, heparan sulfate,
chondroitin sulfate, ionophores, complement cascade components
(e.g., C5b-9) platelet microparticles, platelet membrane
fractions.
[0065] As noted above, a composition or method of the present
invention may include a platelet-mediated occlusion retarder or the
like. The platelet-mediated occlusion retarder may be a moiety that
forms a portion of a bi-functional molecule as noted above, may be
an ingredient in a composition according to the invention, and/or
may be administered separately from a composition according to the
invention. Those skilled iin the art will recognize that it may be
desirable to include or use a platelet-mediated occlusion retarder
when the individual receiving therapy based on the method of the
present invention has an underlying propensity to thrombose (i.e.
form clots too rapidly and/or in inappropriate locations in the
body). Although the method of the present invention is directed to
the formation of a thrombus in the tumor vasculature, individuals
with a propensity to thrombose may form thrombi in inappropriate
locations during the course of the therapy described by the present
invention. Use of agents to reduce the rapidity and/or extent of
thrombosis could be used to minimize the risk of forming thrombi in
inappropriate locations in the body. Examples of conditions whereby
the individual receiving therapy encompassed by the present
invention may require the use of occlusion retarders are, but are
not limited to, coronary artery disease, acute myocardial
infarction, transient ischemic attack, stroke, high blood pressure,
ATIII deficiency, Protein C deficiency, Protein S deficiency,
heparin-induced thrombocytopenia, deep vein thrombosis, peripheral
vascular disease and/or Factor V Leiden deficiency.
[0066] Exemplary platelet-mediated occlusion retarders include but
are not limited to aspirin, aspirin-like compounds, nonsteroidal
anti-inflammatory drugs (NSAIDS), nitric oxide releasing NSAIDS
(NO-NSAIDS), ibuprofen, acetaminophen, ketoprofen, ticlopidine,
clopidogrel, indomethacin, dipyridamole, omega-3 fatty acids,
prostacyclin, nitric oxide, inducers of nitric oxide, inducers of
nitric oxide synthase, proanthocyanidins, matrix metalloproteinase
inhibitors (MMPIs, TlIMPs), anti-GPIIb/IIIa agents,
anti-.alpha.v.beta.3 agents, anti-.alpha.2.beta.1 agents, anti-CD36
agents, aurintricarboxylic acid, thrombin receptor antagonists,
thromboxane receptor antagonists, streptokinase, urokinase, tissue
plasminogen activator (tPA).
[0067] In addition, it is known that platelets which have been
cooled below their membrane phase transition temperature (i.e.,
<15 degrees C.) become irreversibly activated. Although the
platelets function normally if transfused into a patient, the
platelets are rapidly cleared from the body (i.e., approximately 24
hours, in contrast to normal circulating platelet life span of 7 to
10 days). Although these platelets are cleared rapidly, they bind
with high avidity to immobilized VWF. Therefore, transfusion of
cooled platelets provides an additional means to enhance thrombus
formation at the target site. Therefore, one embodiment of the
invention includes controlling platelet-mediated occlusion by
administering platelets cooled as noted above.
[0068] As noted above, the targeting moiety may be, or may be bound
to, one member of a binding pair. Methods according to the
invention may require a time period sufficient for accumulation of
the targeting moiety at the site of localization, for optimal
target to non-target accumulation, for accumulation and binding of
the second member of the binding pair, and/or for clearance of
unbound substances.
[0069] In accordance with the invention, three or more step
targeting or localization steps may be used. Many of these
protocols are well known in the art (see, for example, U.S. Pat.
No. 5,578,287 using a biotin/avidin protocol). Exemplary multiple
step protocols include, but are not limited to, administering a
binding agent-ligand, administering an anti-ligand to clear unbound
binding agent and to localize bound binding agent-ligand, and
administering an active agent-ligand. As used herein, active agent
refers to any therapeutic agent that is active or becomes active
and leads to a therapeutic benefit.
[0070] In accordance with a method of the invention, the binding
agent must be capable of binding a pre-determined binding site or
receptor, and may be administered to the patient by any
immunologically suitable route. For example, the binding agent may
be introduced into the patient by an intravenous, subcutaneous,
intraperitoneal, intrathecal, intravesical, intradermal,
intramuscular, or intralymphatic route. The composition may be in
solution, tablet, aerosol, or multi-phase formulation forms.
Liposomes, long-circulating liposomes, immunoliposomes,
biodegradable microspheres, micelles, or the like may also be used
as a carrier, vehicle, or delivery system. Further more, using ex
vivo procedures well known in the art, blood, plasma, serum, or
cell components from the patient may be removed from the patient;
optionally, it may be desirable to purify the antigen in the
patient's blood; the blood, plasma, serum or cellular component may
then be mixed with a composition that includes a binding agent
according to the invention; and the treated blood, plasma, serum or
cellular component is returned to the patient. The clinician may
compare the responses associated with these different routes in
determining the most effective route of administration. The
invention should not be limited to any particular method of
introducing the binding agent into the patient.
[0071] Administration may be once, more than once, and over a
prolonged period. As the compositions of this invention may be used
for patients in a serious disease state, i.e., life-threatening or
potentially life-threatening, excesses of the binding agent may be
administered if desirable. Actual methods and protocols for
administering pharmaceutical compositions, including dilution
techniques for injections of the present compositions, are well
known or will be apparent to one skilled in the art. Some of these
methods and protocols are described in Remington's Pharmaceutical
Science, Mack Publishing Co. (1982).
[0072] A binding agent may be administered in combination with
other binding agents, or may be administered in combination with
other treatment protocols or agents, e.g., chemotherapeutic
agents.
[0073] As is well known in the art, a disadvantage associated with
administering binding agents or binding agent conjugates in vivo
includes non-target or undesirable target binding. It is therefore
a desirable attribute of any administered composition to minimize
non-target binding, to minimize non-target exposure to the binding
agent or active agent, and/or to maximize clearance of non-bound
binding agent, ligand, or active agent. Moreover, optimizing these
attributes typically permits administering a higher dose of active
agent, a therapeutic agent, or an element of the process that
activates a previously un-activated agent. Those skilled in the art
are well versed in selecting the optimal parameters for
administering the highest possible dose while remaining safely
below the toxicity threshold.
[0074] In accordance with a preferred embodiment of the invention,
therefore, un-activated platelets accumulate or are induced to
accumulate at a pre-determined site, then the properly localized
platelets are selectively activated.
[0075] The effectiveness of the present invention may be monitored
by conventional assays that determine thrombus formation,
morphametric studies of thrombus formation, tumor necrosis, tumor
size, tumor morphology, and/or thrombus formation that results in
tumor necrosis. One skilled in the art will recognize that other
tests may be performed to assess or monitor therapeutic
benefit.
[0076] Since some binding agents such as proteins are by themselves
poor immunogens, their immunogenicity may be augmented by
administration in immunological adjuvants and antigen delivery
systems. The immunogenicity of a specific composition may also be
increased or optimized by choice of delivery route. For example,
the immunogenicity of compositions produced in accordance with the
present invention that include a monoclonal antibody may be
increased by choosing a mode of delivery that increases the direct
contact between the binding agent and the antigen. The referred
route is intravenous. Those skilled in the art are conversant with
the various choices available, and why one route might be chosen
over another route for a particular binding agent.
[0077] One skilled in the art will also recognize that liposomes,
nanospheres, micelles, or microspheres may be used to administer a
composition, and that such administration may result in a
therapeutically desirable benefit.
[0078] It will be recognized by those skilled in the art that for
certain congenital and pathological conditions, some of which are
listed below, it is desirable to modify a composition or method of
the present invention to compensate for a predisposition of the
patient to bleed excessively or to thrombose. Under these
circumstances, use of modifying agents, which either enhance or
dampen a method or composition of the invention, can be employed.
The use of these modifying agents is predicted to minimize bleeding
or clotting episodes. Moreover, the use of modifying agents enables
controlled administration of a composition according to the
invention under normal circumstances (i.e., normal hemostasis).
[0079] Exemplary conditions that may warrant using controllers,
retarders, or agents that diminish a method or composition of the
invention include but are not limited to pro-thrombotic or
pro-coagulant conditions, such as Factor V.sup.Leiden deficiency,
antiphospholipid syndrome (APS), Protein C and/or Protein S and/or
Antithrombin III deficiency, deep vein thrombosis (DVT), pseudo-von
Willebrands disease, Type IIb von Willebrands disease, peripheral
vascular disease (PVD), and high blood pressure, among others.
Exemplary conditions that may warrant using enhancers or agents
that augment a method or composition of the invention include but
are not limited to any condition that includes a risk of
hemorrhage, including but not limited to coagulation factor
deficiencies, hemophilia, thrombocytopenia, and anticoagulation
therapy, among others. Also, controlling thrombus generation
includes at least one of altering the temperature at the
pre-determined site, altering the rate of blood flow at the
pre-determined site, and altering the blood pressure at the
pre-determined site.
[0080] For example, upon initiation of the vascular occlusion
process, reversal or dampening of the associated prothrombotic
condition may be necessary, as will be recognized by those skilled
in the art. In such cases, administration of agents that reduce
platelet reactivity will, in turn, reduce response to the vascular
occlusion initiators. Such agents are readily known by those
skilled in the art and include, but are not limited to: aspirin or
aspirin-like compounds, NSAIDS, NO-NSAIDS, ibuprofen,
acetaminophen, ketoprofen, ticlopidine, clopidogrel, indomethacin,
omega-3 fatty acids, prostacyclin, nitric oxide, inducers of nitric
oxide, inducers of nitric oxide synthase, proanthocyanidins, matrix
metalloproteinase inhibitors (MMPIs, TIMPs), anti-GPlb agents,
anti-GPIIb/IIIa agents, anti-.alpha.v.beta.3 agents,
anti-.alpha.2.beta.1 agents, anti-CD36 agents, aurintricarboxylic
acid, thrombin receptor antagonists, thromboxane receptor
antagonists, streptokinase, urokinase, tissue plasminogen activator
(tPA).
[0081] An exemplary process in which it may be desirable to enhance
or augment platelet occlusion process includes thrombocytopenic
(low platelet count) patients. These individuals would benefit from
concomitant or pre-administration (transfusion) of platelet
products to provide an adequate resource of platelets to accomplish
platelet occlusion. It will be recognized by those skilled in the
art that all transfusable products mimicking or approximating
normal platelet function can be used under such circumstances. Such
agents include but are not limited to: random donor platelets,
apheresis platelets, autologous platelets, washed platelets,
platelet membrane fractions, cooled platelets, frozen platelets,
particles containing or expressing platelet membrane components and
whole blood.
[0082] As a further example, specific platelet-function enhancing
agents can be employed to boost or enhance initial platelet
reactivity once targeted to the site of therapy. Agents known to
those skilled in the art have been demonstrated to enhance existing
platelet reactivity and/or lower the threshold limiting sufficient
platelet reactivity to facilitate irreversible platelet adhesion
and/or platelet degranulation and/or platelet/platelet binding
and/or platelet accretion about an existing thrombus. These agents
include but are not limited to: ristocetin, thrombin,
heparin-induced thrombocytopenia (HIT) antibodies or portions
thereof, antiphospholipid antibodies (APA) or portions thereof,
whole antibody molecules via an Fc-mediated mechanism,
anti-ligand-induced binding site (anti-LIBS) antibodies or portions
thereof, anti-CD9 antibodies or portions thereof, epinephrine,
thrombin receptor activating peptide (TRAP), cathepsin G, elastase,
arachidonate, thromboxane A2 (TxA2) mimetics, TxA2, phospholipase
A2 (PLA2), activators of protein kinase C (PKC), adenosine
diphosphate (ADP), collagen, VWF, matrix metalloproteinases (MMPs),
heparin, heparan sulfate, chondroitin sulfate, ionophores, platelet
microparticles, platelet membrane fractions.
[0083] An exemplary method of targeting or pre-targeting a
composition according to the invention includes accumulating the
targeting agent at the target site, then administering a rapidly
clearing composition comprising a complementary agent that is
capable of binding the previously localized binding agent. Some of
these techniques are disclosed in U.S. Pat. No. 4,863,713.
[0084] Once introduced into the bloodstream of an animal bearing a
tumor, such a bispecific construct will bind to tumor cells within
the tumor; bind or immobilize a platelet specific component,
whereby immobilization activates the platelet specific component;
the activated platelet specific component then binds and activates
platelets; and the activated platelets in turn bind and activate
other platelets until an occlusion is formed.
EXAMPLES
Example 1
[0085] The technique of preparing monoclonal antibodies against
antigenic cell surface markers is quite straightforward and may be
readily carried out using techniques well known to those of skill
in the art as exemplified by the technique of Kohler and Milstein
(1975). Generally speaking, the preparation of monoclonal
antibodies using stimulated endothelial cells involves the
following procedures. Cells or cell lines derived from human tumors
are grown in tissue culture for >4 days. The tissue culture
supernatant ("tumor-conditioned medium") is removed from the tumor
cell cultures and added to cultures of human umbilical vein
endothelial cells (HUVEC) at a final concentration of 50% (v/v).
After 2 days culture the HUVEC are harvested non-enzymatically and
1-2.times.10.sup.6 cells injected intraperitoneally into mice. This
process is repeated three times at two-weekly intervals, the final
immunization being by the intravenous route. Three days later the
spleen cells are harvested and fused with SP2/0 myeloma cells by
standard protocols (Kohler and Milstein, 1975): Hybridomas
producing antibodies with the appropriate reactivity are cloned by
limiting dilution.
[0086] From the resultant collection of hybridomas, one will then
select one or more hybridomas that produce an antibody that
recognizes the activated vascular endothelium to a greater extent
than it recognizes non-activated vascular endothelium of course,
the ultimate goal is the identification of antibodies having
virtually no binding affinity for normal endothelium. Suitable
antibody-producing hybridomas are identified by screening using
e.g., an ELISA, RIA, IRMA, IEF, or similar immunoassay against one
or more types of tumor-activated endothelial cells. Once candidates
have been identified, one will desire to test for the absence of
reactivity for non-activated or "normal" endothelium or other
normal tissue or cell type. In this manner, hybridomas producing
antibodies having an undesirably high level of normal
cross-reactivity for the particular application envisioned may be
excluded.
Example 2
[0087] The technique of preparing single chain antibodies that
specifically recognize a ligand/receptor complex, specifically a
growth factor/growth factor receptor complex is employed, whereby
the resulting antibody molecules recognize the growth factor/growth
factor receptor complex, but do not bind to either the growth
factor or growth factor receptor alone. These antibodies can be
formed through the immunization of mice with a complex of purified
ligand and receptor, such as VEGF and VEGF receptor, and the
resulting V genes used to construct an antibody library in
filamentous phage. The phage display of antibody fragments allows
the production of recombinant antibody molecules against activated
endothelial cell antigens, specifically a ligand/receptor complex.
The phage system mimics the vertebrate immune system.
[0088] Female Balb/C mice are immunized with HPLC-purified
recombinant VEGF and VEGF receptor (e.g. soluble FLT) in complex,
in the presence of an adjuvant such as Quil A. After the
appropriate antibody titre is reached (approximately the fourth
boost), the mice are sacrificed and the spleens isolated. Messenger
RNA (mRNA) is isolated from the spleen and transcribed to cDNA. The
V genes of the cDNA are amplified and assembled as "single chain
Fv" (scFv). After digestion with the appropriate restriction
enzymes, the scFv are ligated into phagemid vectors. Competent E.
coli cells are then transformed with these phagemid libraries, and
after infection with helper phage (e.g. M13K07, Pharmacia), phage
particles displaying the scFv are prepared. Selected clones are
screened for expression of soluble scFv binding to the
ligand/receptor complex, but do not bind to either the ligand alone
or the receptor alone. This screening is accomplished using
standard ELISA techniques, with the ligand/receptor complex, ligand
and receptor used as solid-phase antigens, respectively.
Example 3
[0089] A variety of endothelial cell markers are known that can be
employed as inducible targets for the practice of this aspect of
the invention including VEGF/VPF (vascular endothelial growth
factor/vascular permeability factor), endothelial-leukocyte
adhesion molecule (ELAM-1; Bevilacqua et al., 1987); vascular cell
adhesion molecule-1 (VCAM-1; Dustin et al; 1986) intercellular
adhesion molecule-1 (ICAM-1; Osborn et al., 1989); the agent
leukocyte adhesion molecule-1 (LAM-1 agent) or even a major
histocompatibility complex (MHC) Class II antigen, such as HLA-DR,
HLA-DP, or HLA-DQ (Collins et al., 1984). Of these, the targeting
of the VEGF/VEGF receptor complex will be preferred.
Example 4
[0090] Targeting platelets to a specific site can take the form of
establishing a linkage between the bifunctional binding agent and
the target site, followed by platelet binding: or can take the form
of establishing a linkage between the bi-functional binding agent
and the platelet, followed by binding of the platelet to the target
site. The latter example requires pretreatment of the platelets (in
vivo, in vitro; autologous donor) with the bifunctional agent. An
exemplary bi-functional agent would impart minimal immunogenicity
to the treated platelets and would bind specifically with high
avidity to the tumor site, tumor vasculature, hyperplastic
tissue(s) or organ(s). Platelets pre-treated with the bi-functional
agent could take the form of random donor or apheresis platelets
suitable for transfusion. Platelets, which have been cooled before
or after treatment with the bifunctional agent, would provide a
means of enhancing the targeted vaso-occlusive effects.
Example 5
[0091] Platelet activation at the target site will induce secondary
effects that may enhance diminution or killing of the target
tissue. Release of agents by the activated platelets such as
platelet factor 4 (PF4) will inhibit angiogenesis. Platelet release
of chemoattractants such as Regulated on Activation Normal T-cell
Expressed and Secreted (RANTES), post activation, will enhance the
effects of leukocytes (e.g., eosinophils, monocytes) on target
tissue. Expression of granular constituents such as CD62 by the
platelets, post activation, will induce binding of monocytes and
polymorphonuclear leukocytes (PMNs) resulting in tissue factor
expression (monocyte; procoagulant) and cellular activation and
attack (PMNs). In addition, release of CD40 ligand (CD40L) by
activated platelets at the target site will induce tissue factor
expression by monocytes leading to a local hyper-coagulable
state.
Example 6
Identification of Candidate Monoclonal Antibodies
[0092] Prostate cancer tumor cell line LnCAP (Clone FGC, ATCC #
CRL-1740) was grown in modified RPMI 1640 medium according to the
product information sheet provided by the American Type Culture
Collection (ATCC). Six different hybridomas producing antibodies
specific for MUC1 were tested for binding reactivity to LnCAP cells
and MCF-7 cells (human breast carcinoma) by flow cytometry. The
following table describes the binding epitope specificity of these
hybridomas and the reactivity of the hybridomas with
MUC1-expressing MCF-7 human breast carcinoma cells.
1 Binding to MCF-7 Cells MUC1 Binding Flow Cytometry (% Hybridoma
Epitope positive) Control -- 2% TH1 GVTSAPDTRPAP 72% TH2 PDTRP 69%
TH3 TSAPDTR 12% TH4 APDTR 17% TH5 TSAPDTR 11% TH6 SAPDTRPA 60%
TH1-TH6 Cocktail -- 55%
[0093] A similar study was carried out using prostate cancer LnCAP
cells as the target. Also included in this study was antibody 7E11
(ATCC # HB 10494) recognizing prostate specific membrane antigen
(PSMA) and EMT6/Ed (murine mastocytoma) cells as target. The
following table presents data from these flow cytometry
experiments.
2 Antibody LnCAP EMT6/Ed Control 8% 8% 7E11 58% 4% TH1-TH6 Cocktail
55% 9%
[0094] Based on these results, the TH6 hybridoma (anti-MUC1) and
the 7E11 hybridoma (anti-PSMA) were chosen for further study.
Example 7
Biotinylation of Targeting Antibodies
[0095] Protein A Sepharose-purified TH6 and 7E11 monoclonal
antibodies were biotinylated according to the manufacturer's
(Sigma, St. Louis, Mo.) directions. In addition, humanized (i.e.,
human Fc bound to mouse monoclonal F(ab')2) antibodies (TH6, 7E11)
were also biotinylated. In a similar manner, purified human von
Willebrand factor was also biotinylated. Testing confirmed both
significant levels of biotinylation of the antibodies and no
reduction in antibody binding to LnCAP cells. Similarly,
biotinylated VWF was shown to retain both the capacity to initiate
platelet adhesion and promote platelet/platelet binding, post
biotinylation. VWF (.+-.biotinylation) was immobilized on
polystyrene beads as described by Stewart et al (Br J Haematol,
97:321-329, 1997). The VWF-coated beads were then used as a
solid-phase agonist to induce platelet adhesion and subsequent
platelet dense granule ATP release. ATP release was quantified
using a luciferin/luciferase assay (Stewart et al, 1997).
Comparison of VWF beads with biotinylated-VWF beads indicated the
two agents to be equivocal relative to platelet activation
(0.41.+-.0.05, 0.39.+-.0.05 arbitrary luminescence units;
respectively).
Example 8
Targeting Platelets to Cancer Cells
[0096] LnCAP cells were challenged with biotinylated antibodies, or
non-biotinylated antibodies (TH6 or 7E11); washed to remove unbound
antibody; challenged with avidin or neutravidin, or not; washed to
remove unbound avidin or neutravidin; challenged with biotinylated
human VWF; then incubated with human citrated whole blood or
platelet rich plasma under agitation. Platelet reactivity with the
LnCAP cells was then assessed by video microscopy, phase contrast
microscopy and fluorescence microscopy. The following table
presents the results of these experiments.
3 Human Platelets Binding Test Conditions to LnCAP Cells Control-No
agents added to LnCAPs - TH6.biotin/No Avidin/VWF.biotin -
TH6.biotin/Avidin/VWF.biotin + + Humanized TH6.biotin/No
Avidin/VWF.biotin -/+ Humanized TH6.biotin/Avidin/VWF.biotin + + +
+ 7E11.biotin/No Avidin/VWF.biotin - 7E11.biotin/Avidin/VWF.biotin
+ + + Humanized 7E11.biotin/No Avidin/VWF.biotin -/+ Humanized
7E11.biotin/Avidin/VWF.biotin + + + +
[0097] Targeting of the LnCAP cells with either biotinylated TH6 or
7E11 led to localization of platelets, in either platelet rich
plasma or whole blood, to the cancer cells, via interaction with
cancer cell-immobilized VWF. The interaction of platelets with
cancer cells was dramatically enhanced by constructing a
humanized/biotinylated targeting antibody. Engagement of the
platelet Fc receptor by the humanized portion of the targeting
antibody (i.e., the human Fc component) caused massive platelet
aggregation about the cancer cells and subsequent membrane blebbing
and/or loss of cell membranes in the form of vesicles.
[0098] Although the present invention has been described in terms
of particular preferred embodiments, it is not limited to those
embodiments. Alternative embodiments, examples, and modifications,
which would still be encompassed by the invention, may be made by
those skilled in the art, particularly in light of the foregoing
teachings.
Sequence CWU 1
1
6 1 12 PRT human MUC-1 1 Gly Val Thr Ser Ala Pro Asp Thr Arg Pro
Ala Pro 1 5 10 2 5 PRT human MUC-1 2 Pro Asp Thr Arg Pro 1 5 3 7
PRT human MUC-1 3 Thr Ser Ala Pro Asp Thr Arg 1 5 4 5 PRT human
MUC-1 4 Ala Pro Asp Thr Arg 1 5 5 7 PRT human MUC-1 5 Thr Ser Ala
Pro Asp Thr Arg 1 5 6 8 PRT human MUC-1 6 Ser Ala Pro Asp Thr Arg
Pro Ala 1 5
* * * * *