U.S. patent application number 11/928595 was filed with the patent office on 2008-07-03 for compositions and methods for producing vascular occlusion using a solid-phase platelet binding agent.
This patent application is currently assigned to VIREXX MEDICAL CORP.. Invention is credited to Antoine Noujiam, Roland H. Person, Michael W. Stewart.
Application Number | 20080160063 11/928595 |
Document ID | / |
Family ID | 23237759 |
Filed Date | 2008-07-03 |
United States Patent
Application |
20080160063 |
Kind Code |
A1 |
Stewart; Michael W. ; et
al. |
July 3, 2008 |
Compositions and Methods for Producing Vascular Occlusion Using a
Solid-Phase Platelet Binding Agent
Abstract
The present invention relates generally to methods and
compositions for targeting and delivering solid-phase
platelet-dependent vascular occlusion agents. In particular,
particles or coils or stents coated with platelet binding agents
are directed to target vasculature, such as the vasculature of
solid tumor masses or AV-malformations or aneurysms or endoleaks;
the solid-phase agent then binds and activates platelets, which in
turn bind and activate other platelets. This process results in the
rapid formation of a platelet-mediated thrombus about the
solid-phase agent causing vessel occlusion.
Inventors: |
Stewart; Michael W.; (Spruce
Grove, CA) ; Noujiam; Antoine; (Edmonton, CA)
; Person; Roland H.; (Kelowana, CA) |
Correspondence
Address: |
WILLIAM J BUNDREN;THE LAW OFFICE OF WILLIAM J BUNDREN
734 LaRue Road
Millersville
MD
21108
US
|
Assignee: |
VIREXX MEDICAL CORP.
Edmonton
CA
|
Family ID: |
23237759 |
Appl. No.: |
11/928595 |
Filed: |
October 30, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11205047 |
Aug 17, 2005 |
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11928595 |
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10241717 |
Sep 12, 2002 |
6960352 |
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11205047 |
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60318339 |
Sep 12, 2001 |
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Current U.S.
Class: |
424/423 ;
424/499; 514/13.6; 514/13.7; 514/17.2; 514/776; 514/9.3 |
Current CPC
Class: |
A61K 9/167 20130101;
A61K 31/16 20130101; A61L 2300/252 20130101; A61L 31/16 20130101;
A61K 47/62 20170801; A61K 47/6921 20170801; A61K 38/36 20130101;
A61K 38/37 20130101; A61L 31/047 20130101; A61P 35/00 20180101;
A61K 47/6927 20170801; A61L 2300/418 20130101; A61L 24/108
20130101 |
Class at
Publication: |
424/423 ;
514/776; 424/499; 514/8 |
International
Class: |
A61K 9/00 20060101
A61K009/00; A61K 47/42 20060101 A61K047/42; A61K 38/37 20060101
A61K038/37; A61K 9/14 20060101 A61K009/14 |
Claims
1. A composition for inducing thrombus formation in vivo comprising
a solid-phase agent comprising a platelet-specific component;
wherein upon delivery to target vasculature the platelet-binding
component binds platelets onto the solid-phase agent, induces
platelet activation and allows a thrombus to form.
2. The composition of claim 1 where the solid-phase agent is a
particle.
3. The composition of claim 2 where the particle is a
microsphere.
4. The composition of claim 2 where the particle is
macro-aggregated albumin.
5. The composition of claim 4 where the particles range in size
from about 5 to about 500 microns.
6. The composition of claim 4 where the particles range in size
from about 30 to about 150 microns.
7. The composition of claim 1 where the solid-phase agent is a
coil.
8. The composition of claim 1 where the solid-phase agent is a
stent.
9. The composition of claim 1 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, natural or synthetic.
10. The composition of claim 1 wherein the platelet-specific
component is recombinant VWF.
11. The composition of claim 1 wherein the platelet-specific
component is mammalian VWF.
12. The composition of claim 1 wherein the platelet-specific
component is of human origin.
13. The composition of claim 1 wherein the platelet-specific
component is of porcine origin.
14. The composition of claim 1 wherein the solid-phase agent
contains a targeting moiety.
15. The composition of claim 1 wherein the targeting moiety is
directed to at least one antigen on the target vasculature.
16. The composition of claim 1 wherein the solid-phase agent
further comprises a ligand for binding platelets to the solid phase
agent.
17. The composition of claim 1 wherein the solid-phase agent is
radiolabeled with sodium pertechnetate Tc 99m.
18. A composition for inducing thrombus formation comprising a
solid-phase platelet-binding agent having a first binding component
and a second binding component, said first binding component
comprising a binding region for binding the solid-phase agent to a
ligand/receptor complex but not the ligand or receptor alone; said
second binding component comprising a binding region for
platelets.
19. A composition for inducing thrombus formation comprising a
solid-phase agent having a first binding component and a second
binding component, said first binding component comprising a
binding region for binding the binding component to an epitope on a
pre-determined site; said second binding component comprising a
binding region for platelets.
20. The composition of claim 1 wherein the solid phase agent is 10
microns to 7000 microns.
Description
[0001] This application is a divisional of U.S. application Ser.
No. 11/205,047 filed Aug. 17, 2005 and has been allowed, which is a
continuation of U.S. application Ser. No. 10/241,717 filed Sep. 12,
2002, and is now U.S. Pat. No. 6,960,358, which is a
non-provisional of U.S. Application Ser. No. 60/318,339 filed Sep.
12, 2001. These patent applications are hereby incorporated by
reference.
I. BACKGROUND OF THE INVENTION
[0002] 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 delivering a
solid-phase platelet-binding agent to a target site, causing
platelets to bind and activate thereby forming a localized
thrombus. Occlusion of the vasculature of the target tissue by the
localized thrombus results in deprivation of essential oxygen and
nutrients, in turn leading to tissue regression and ultimately
tissue death.
II. DESCRIPTION OF RELATED ART
[0003] 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. Circulating 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 circulating platelets from
the blood stream, and 5) form an efficient plug, clot, and/or
thrombus stemming the flow of blood from the vessel.
[0004] In response to vascular injury, such as atherosclerotic
plaque rupture in a coronary vessel, circulating platelets are
exposed to a variety of matrix elements that are prothrombotic.
Platelets can strongly adhere to two specific matrix components,
collagen and von Willebrand factor. At low blood flow shear rates,
adhesion to collagen predominates, whereas at higher shear
rates--for example, those that would occur in stenosed vessels--the
initial platelet adhesion is primarily mediated by binding to von
Willebrand factor. Adhesion to either collagen and/or von
Willebrand factor initiates signals leading to platelet activation,
platelet spreading on the matrix, secretion of prothrombotic
substances such as adenosine diphosphate (ADP) and thromboxane
A.sub.2, and upregulation of the adhesive function of GP IIb-IIIa,
which can bind fibrinogen and von Willebrand factor, resulting in
platelet aggregate or thrombus formation.
[0005] In contrast to the coagulation cascade, a process defined in
part by the conversion of fibrinogen to fibrin, platelets coalesce
about 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 von Willebrand Factor
(VWF) in the subendothelium (i.e., immobilized VWF). This
interaction in itself is unique, since normal platelets circulating
in the blood often contact soluble VWF, but 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. Upon activation of
the platelet, an additional receptor, glycoprotein IIb/IIIa
(GPIIb/IIIa), is altered enabling the binding of several plasma
proteins, thereby promoting platelet/platelet binding.
[0006] Hyperactive platelets can induce thrombus formation at
inopportune times resulting in reduced blood supply to various
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.
[0007] Other pathological states exist that are caused by platelet
activation as a result of an inappropriate 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. From 1% to 5% of all patients receiving
unfractionated heparin as an anticoagulant to promote blood flow
produce an antibody that binds to heparin in complex with a
platelet granule protein. 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.
[0008] 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 neoplasia or
neoplasms. It has been suggested that thrombosis is the most
frequent complication with patients with overt malignant
disease.
[0009] 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 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.
[0010] 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 per gram of
tumor are not uncommon in human studies. Furthermore, antibodies
that enter the tumor mass do not distribute evenly for several
reasons. Firstly, 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.
Secondly, the distribution of blood vessels in most tumors is
disorganized and heterogeneous. As a result some tumor cells are
separated by large distances from capillaries so that the
extravasating antibody must diffuse over a large volume in order to
reach and bind to remote tumor cells. Thirdly, 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.
[0011] One approach to overcoming the deficiencies of targeting
tumors with antibodies would be to target thrombus-inducing agents
to the vasculature of the tumor rather than to the tumor.
[0012] The present inventors propose that this approach will
provide several advantages over targeting tumor cells directly.
Firstly, the target cells are directly accessible to vascularly
administered therapeutic agents permitting rapid localization of a
high percentage of the injected dose. Secondly, 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.
[0013] The present invention is also directed to compositions and
methods of treating abnormal tissue growth, abnormal bleeding
(during or after surgery, postpartum), ectopic pregnancy, placenta
previa, placenta accreta and uterine fibroids.
[0014] Under certain clinical situations, inhibition of blood flow
to a tissue through occlusion of its associated vasculature is
desirable. Examples include hemorrhagic stroke, existence of
saphenous vein side branches in saphenous bypass graft surgery,
treatment of aortic aneurysm, correction of vascular malformations,
and treatment of solid tumors.
[0015] Vascular occlusion has been performed using a variety of
techniques and materials including embolotherapy. Examples of
embolotherapy include the use of particles composed of a variety of
materials including polyvinyl alcohol (Boschetti, PCT WO0023054),
acrylamide (Boschetti et al, U.S. Pat. No. 5,635,215; Boschetti et
al, U.S. Pat. No. 5,648,100), polymethyl methacrylate (Lemperle,
U.S. Pat. No. 5,344,452), physical plugs composed of collagen
(Conston et al, U.S. Pat. No. 5,456,693) and coils (Mariant, U.S.
Pat. No. 5,639,277). Embolotherapy involves the delivery of these
materials to the target vasculature by means of a catheter. Since
the vasculature in any given area proceeds from larger arteries to
arterioles to metarterioles to capillaries, each with progressively
smaller vessel diameters, the delivered material (embolus)
continues to travel in the flowing blood until it becomes lodged in
the smaller blood vessels thereby impeding the flow of blood to the
dependent tissue.
[0016] The present invention is novel and addresses unmet medical
needs through the use of a solid-phase material, such as
microparticles or coils or stents, coated with porous polylactide,
polyglycolide or polylactide-co-glycolide particles coated with
mammalian collagen. In this way a therapeutic benefit may be
achieved by delivering a solid-phase platelet-binding agent to a
target site and initiating efficient thrombus formation leading to
occlusion of the associated vasculature.
III. SUMMARY OF THE INVENTION
[0017] 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, or
which have arterio-venous malformations, or which are hemorrhaging,
using solid-phase agents that induce thrombus formation via
localized platelet activation. The composition comprises an agent
for capturing platelets on a solid-phase agent such as a coil or a
stent or a particle. In some embodiments of the invention, the
solid-phase agent both captures and activates the platelets. The
method utilizes localizing platelet collection and activating the
platelets on the solid-phase particle to produce subsequent
thrombus formation, thereby limiting the blood supply to the target
area, without inducing a generalized or systemic pro-thrombotic
state.
[0018] Purposeful induction of thrombosis in a patient appears at
first glance to be counter-intuitive, since thrombosis is well
known to contribute significantly to patient morbidity and
mortality. The present invention, solid-phase 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 porous polylactide, polyglycolide or
polylactide-coglycolide particles coated with mammalian collagen or
other locally acting platelet activation agents. The immobilized
collagen, acting as a platelet binding agent, serves to anchor
platelets to the particles through two mechanisms: 1) directly, by
binding to key platelet membrane receptors such as a2.beta.1 and
GPVI; and 2) indirectly, by capturing circulating, autologous, von
Willebrand factor (VWF), which in turns captures and activates
platelets circulating in the blood stream through key platelet
membrane receptors such GPIb and GPIIb/IIIa. 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] Contact of the solid-phase platelet-binding agent with the
blood from a patient (ex vivo) or in the blood stream (in vivo)
induces platelet binding and localized activation leading to
accretion of platelets about the solid-phase agent leading to
thrombosis and cessation of blood flow to the tissue supplied by
the occluded blood vessel(s). Cells, including tumor cells or
hyperplastic tissue, 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 porous
polylactide, polyglycolide or polylactide-co-glycolide particles
coated with mammalian collagen binds to and activates circulating
platelets. Thus, the methods and compositions of the present
invention are an indirect means of treating a pathological
condition, such as cancer, hyperplastic cells, excessive bleeding
or arteriovenous (AV) malformations.
[0020] The present invention improves on existing methods for
treating solid tumors, hyperplastic tissue, excessive bleeding and
AV-malformations and any other disease or condition in which
platelets (resting and/or activated) may play a therapeutic
role.
[0021] In a manner similar to an existing pathological condition
(i.e. Heparin-Induced Thrombocytopenia [HIT]), localized platelet
activation can be enhanced by means of an Fc-mediated process by
including or incorporating a human Fc fragment onto the solid-phase
agent, or by directing select antibodies to the target area.
Platelet activation in HIT syndrome results in localized thrombosis
and cessation of blood flow to the affected area. This leads to
death of the affected tissue.
[0022] The extent or 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.
[0023] Typical vascularized tumors are the solid tumors,
particularly carcinomas, which require a rich vascular blood
supply. Exemplary solid tumors to which the present invention is
directed include, but are not limited to, primary malignant tumors
of the lung, breast, ovary, stomach, pancreas, larynx, esophagus,
testes, liver, parotid, biliary tract, colon, rectum, cervix,
uterus, endometrium, kidney, bladder, prostate, thyroid, head and
neck, melanomas, gliomas, neuroblastomas, neuroendocrine tumors,
and the like. Other conditions to which the present invention is
directed include, but are not limited to, secondary (metastatic)
tumors of the above mentioned tumor types, cancer pain,
AV-malformations, uterine fibroids, pelvic congestion, menorrhagia,
varicoceles, hemoptysis, aneurysms, visceral artery aneurysms,
pseudoaneurysms and endoleaks.
[0024] A preferred method of the invention includes preparing a
coil or stent coated with porous polylactide, polyglycolide or
polylactide-co-glycolide particles coated with mammalian collagen
(PLGA/Collagen) and introducing the PLGA/Collagen-coated agent into
the bloodstream of an animal, such as a human patient, an animal
patient, or a test animal; the PLGA/Collagen is then delivered or
collects at a desired target site. The coils or stents can be
constructed of any suitable material capable of retaining
PLGA/Collagen either within the coil or stent or on the surface of
the coil or stent for an indefinite or varying lengths of time.
[0025] A solution to the problem of the unrestrained growth of
solid tumors is to attack the blood vessels in the tumor. This
approach offers several advantages over methods that directly
target tumor cells. Firstly, the tumor vessels are directly
accessible to vascularly administered therapeutic agents, thus
permitting rapid localization of high percentage of the injected
dose. Secondly, 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, blood vessels are similar in different
tumors, making it feasible to develop a single reagent for treating
numerous types of cancer.
IV. DESCRIPTION OF THE DRAWINGS
[0026] Not Applicable
V. DETAILED DESCRIPTION OF THE INVENTION
[0027] The present invention provides compositions and methods for
capturing platelets at a predetermined site, activating the
platelets, and harnessing the natural function of platelets to
achieve a beneficial therapeutic result. In accordance with the
present invention, the platelets may be circulating platelets or
may be platelets obtained from an external source. In accordance
with the present invention, platelets may be targeted to a specific
site, and 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. In some
instances reduction of the blood supply to a target area alleviates
pain.
[0028] The present invention also includes targeting platelets to a
pre-determined tissue capable of being selectively targeted, e.g.,
hyperplastic tissue, using a solid-phase agent capable of binding
and activating the platelets. In these embodiments of the
invention, targeting refers to the solid phase containing a
targeting moiety, e.g., a ligand or the like, that specifically
binds the pre-determined site or tissue. In other embodiments of
the invention, targeting may include delivering a composition of
the present invention at or near a tumor site, e.g., by catheter,
stent, or coil. Activating the platelets at the pre-selected site
causes a therapeutic benefit by reducing the nutrient supply to the
tissue or site.
[0029] The present invention provides compositions and methods for
inducing thrombus formation by capturing platelets on the
solid-phase agent, inducing activation of the platelets, and
allowing a thrombus to form. Thrombus formation in the target
vasculature reduces the blood supply to the downstream tissue. By
capturing platelets on a PLGA/Collagen-containing solid phase
agent, the compositions and methods of the present invention may be
used to treat cancer, hyperplasia, uterine fibroids, pelvic
congestion, menorrhagia, AV-malformations, neuro-embolism,
varicoceles, hemoptysis, visceral artery aneurysms, arterial
aneurysms, endoleaks, and the like. Furthermore, the compositions
and methods of the present invention provide a therapeutic benefit
to the recipient of the composition.
[0030] In a preferred embodiment of the invention, the
PLGA/Collagen is of mammalian origin. In a most preferred
embodiment of the invention, the PLGA/Collagen is of human origin.
In a further most preferred embodiment of the invention, the
PLGA/Collagen is of bovine origin.
[0031] The PLGA/Collagen may be natural, synthetic, recombinant, or
a peptide sequence conforming to a biologically active portion of
PLGA/Collagen. In a further most preferred embodiment of the
invention, the PLGA/Collagen is of recombinant origin.
[0032] The present invention also provides compositions that bind a
platelet-binding agent directly or indirectly through a spacer to
the solid phase, so long as the ability of the platelet-binding
agent to bind platelets is not impaired. Spacer, as used herein,
refers to a group of inert or active molecules that physically
separate the platelet binding agent from the surface of the solid
phase agent. Exemplary spacers are described below. The direct
binding can occur either covalently or non-covalently. Indirect
binding can occur through spacers, including but not limited to
peptide spacer arms, antibody spacers, antibody fragment spacers,
fusion protein spacers or carbohydrate spacers. These spacers
normally act only as bridges between the particle and the
PLGA/Collagen; however, the spacers could also be used to alter the
degree of platelet activation. For example, an Fc component could
be used as a spacer, thereby effecting enhanced platelet activation
on and about the solid-phase agent. Coupling of PLGA/Collagen to
the solid phase agent can occur using methods known to those
skilled in the art. Examples of coupling agents include but are not
limited to glutaraldehyde and carbodiimide.
[0033] In a preferred embodiment of the invention, the positioning
within the vascular system of mammals of compositions without an
active targeting agent would be selected by blood flow directed
positioning following delivery by means of a superselective
microcatheter.
[0034] Compositions according to the present invention may also
include a targeting agent or moiety capable of binding a target
antigen or site on the vascular endothelium or target tissue,
thereby enabling localization of the solid-phase agent to a
selected site. Exemplary targeting agents or moieties are well
known to those skilled in the art, and include, but are not limited
to antibodies, ligands, receptors, hormones, lectins, and
cadherins, or portions or fragments thereof.
[0035] In a preferred embodiment of the invention, the targeting
agent would include an antibody or antibody-like molecule with
biotin, biotin mimetic and/or a peptide component. In a further
preferred embodiment of the invention, the antibody or
antibody-like molecules would be directed toward a growth
factor/receptor complex.
[0036] 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.
[0037] Methods according to the invention may also include
administering a solid-phase agent capable of binding platelets at a
pre-determined site; may also include 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, or by altering the
temperature at the pre-selected site.
[0038] 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; administering one or more complement cascade
components; administering one or more ligands and/or anti-ligands
for binding the solid phase to a pre-determined site, and/or for
binding a platelet binding moiety or component to the solid
phase.
[0039] The present invention also includes a kit which may contain
but is not limited to any or all of the following components
including a solid-phase agent for targeting platelets to an
endothelial membrane component: a binding agent for binding
platelets; a ligand for binding an endothelial membrane component;
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.
[0040] 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.
[0041] In accordance with some embodiments of the invention,
binding agents are used to capture platelets at a predetermined
site.
DEFINITIONS
[0042] As used herein, a solid-phase agent refers to any solid
material suitable for binding, containing, or retaining a
platelet-binding agent. The platelet-binding agent may be attached
to the solid-phase agent such that platelet binding activity is
retained, e.g., at or within a target site. The solid phase agent
may be a coil, stent, or particle, e.g., a bead or the like, all of
which are well known to those skilled in the art.
[0043] As used herein, a particle refers to a discrete portion or
part of a solid-phase material capable of containing or retaining a
platelet-binding agent.
[0044] A preferred method of the invention includes preparing a
particle coated with PLGA/Collagen of recombinant or mammalian
origin and introducing the PLGA/Collagen-coated particle into the
bloodstream of an animal, such as a human patient, an animal
patient, or a test animal.
[0045] As used herein, the term "particle" refers to any
solid-phase material capable of binding platelets, either directly
or indirectly (e.g., through ligands). The particles can be
homogenous or heterogeneous as related to size. Specifically, the
particles can be of spherical (including ovoid) or irregular shape.
The particles can be constructed of any suitable material capable
of retaining collagen either within the particle or on the surface
of the particle for an indefinite or varying lengths of time.
Exemplary materials include polyvinyl alcohol (PVA), polystyrene,
polycarbonate, polylactide, polyglycolide, lactide-glycolide
copolymers, polycaprolactone, lactide-caprolactone copolymers,
polyhydroxybutyrate, polyalkylcyanoacrylates, polyanhydrides,
polyorthoesters, albumin, gelatin, polysaccharides, dextrans,
starches, methyl methacrylate, methacrylic acid, hydroxylalkyl
acrylates, hydroxylalkyl methacrylates, methylene glycol
dimethacrylate, acrylamide, bisacrylamide, cellulose-based
polymers, ethylene glycol polymers and copolymers, oxyethylene and
oxypropylene polymers, polyvinyl acetate, polyvinylpyrrolidone and
polyvinylpyridine, magnetic particles, fluorescent particles,
animal cells, plant cells, macro-aggregated and micro-aggregated
albumin, denatured protein aggregates and liposomes, used singly or
in combination.
[0046] In the present invention the preferred solid phase material
is polylactide, polyglycolide or polylactide-co-glycolide. The
solid phase materials suitable for use in the present invention are
well known to those skilled in the art, and should not be limited
to those exemplary materials recited above.
[0047] Exemplary materials for forming the stent or coil include,
but are not limited to: polyvinyl alcohol (PVA), polystyrene,
polycarbonate, polylactide, polyglycolide, lactide-glycolide
copolymers, polycaprolactone, lactide-caprolactone copolymers,
polyhydroxybutyrate, polyalkylcyanoacrylates, polyanhydrides,
polyorthoesters, polysaccharides, dextrans, starches, methyl
methacrylate, methacrylic acid, hydroxylalkyl acrylates,
hydroxylalkyl methacrylates, methylene glycol dimethacrylate,
acrylamide, bisacrylamide, cellulose-based polymers, ethylene
glycol polymers and copolymers, oxyethylene and oxypropylene
polymers, polyvinyl acetate, polyvinylpyrrolidone and
polyvinylpyridine; magnetic materials, fluorescent materials; gold,
platinum, palladium, rhenium, rhodium, ruthenium, stainless steel,
tungsten, titanium, nickel and alloys thererof; used singly or in
combination.
[0048] The preferred size of the solid phase material depends on
the type of material being used. For example, those skilled in the
art will recognize that if the solid phase is a stent or coil, the
size is preferably of a diameter that fits within a blood vessel,
such as an artery. Typically the diameter will be up to about 15 mm
or greater. If the solid phase is a particle, such as a bead, the
diameter may be up to about 7 mm, preferably from about 1 .mu.m to
about 5 mm, even more preferably from about 20 .mu.m to about 300
.mu.m. The size of solid phase materials suitable for use in the
present invention are well known to those skilled in the art, and
should not be limited to the exemplary sizes recited above.
[0049] As used herein, a binding agent or targeting moiety refers
to one or more solid phase chemical or biological molecules or
structures for binding one substance to another. Specifically the
binding agent, or solid phase agent, binds a ligand, a receptor or
a ligand/receptor complex on a defined population of cells,
typically hyperplastic tissue and/or associated vasculature, or a
cancer cell and/or associated vasculature. 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.
[0050] As used herein, a ligand-binding agent refers to a
complementary set of molecules that demonstrate specific binding
for each other. 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, heterophyllic peptides, "leucine zippers",
zinc finger proteins/ds DNA fragment, enzyme/enzyme inhibitor,
hapten/antibody, ligand/ligand receptor, and growth factor/growth
factor receptor.
[0051] As used herein, a selected site, a pre-determined site,
targeting, and pre-targeting all refer to a site where the
accumulation of platelets about a solid-phase agent 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, the
vasculature of benign tumors, the vasculature of hyperplastic
tissue(s), AV-malformations, vessel aneurysms and endoleaks.
[0052] As used herein, delivery of the solid agent comprising a
platelet-binding agent can occur using a catheter, a microcatheter
or by needle and syringe. Delivery by catheter or microcatheter is
most often achieved by access through the arterial circuit, however
delivery of the solid agent through the venous circuit is also
desirable. As an example, the solid agent in the form of particles,
coils or stents can be delivered by catheter to the target site
using the arterial or venous circuits. Delivery of the solid agent
using the arterial circuit is advantageous since the capillary beds
downstream of the applied agent in the target tissue act as a means
of trapping the agent, thereby preventing the agent from entering
the systemic circulation. The solid agent can also be localized
within the arterial circulation using a targeting agent associated
with the solid agent. Delivery of the solid agent using the venous
system is also desirable. Localized delivery of the solid agent in
the venous system can be accomplished by binding the solid agent to
the target site using a targeting agent associated with the solid
agent. The solid agent can also be delivered to the target site
during a surgical procedure. As an example, the solid agent in the
form of particles can be delivered by syringe and needle to the
target site. As a further example, the solid agent in the form of a
coil or stent can be placed manually at the target site during the
surgical procedure.
[0053] As used herein, thrombus refers to any semi-solid aggregate
of blood cells enmeshed in fibrin and clumps of platelets
originating from platelets actively binding to the solid-phase
agent. 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 are thrombus
forming.
[0054] As used herein, embolus refers to an intravascular mass,
which travels through the bloodstream, and through size constraints
eventually becomes lodged in a blood vessel or capillary, distal
from the site of origin of the intravascular mass. Embolization
does not imply an active process, but instead refers to a passive
process whereby occlusion of blood vessels occurs by intravascular
masses traveling through the blood stream where they become lodged
in small blood vessels and capillaries.
[0055] In contrast, the present invention involves the delivery of
solid-phase material to target vasculature whereupon platelets are
actively recruited to the solid-phase surface through the use of a
platelet-binding agent. In contrast to embolizing materials
described in cited patents, included herein as reference, the
agents of the present invention must be delivered in close
proximity to the target vasculature due to rapid accumulation of
platelets about the solid-phase material.
[0056] The present invention improves upon existing methods of
producing vascular occlusion by securing platelets to the surface
of a solid-phase material through the use of a platelet-binding
agent, thereby increasing the effective size of the solid-phase
material. For example, a particle (e.g. polylactide, polyglycolide
or polylactide-coglycolide) coated with or containing collagen,
which is injected into the blood stream, would rapidly accumulate
platelets on its surface, in effect producing an `onion-effect` of
layered, activated platelets in close proximity to the injection
site. Therefore the present invention enables delivery of a minimum
number of small particles into the bloodstream, whereupon the
particles rapidly grow in size from the accretion of platelets
actively binding to the platelet-binding agent on or within the
particle. Furthermore, the particle-bound platelets would interact
with each other thereby forming aggregates of increasing size
producing a tight matrix and effecting occlusion of the target
vasculature.
[0057] The present invention further improves upon existing methods
of producing vascular occlusion by securing platelets to the
surface of a solid-phase material by means of a platelet-binding
agent. The agent of the invention would therefore have the
following effects in vivo: a) molding to the contours of the blood
vessel or capillary in which it resides, b) producing a solid,
impermeable three-dimensional matrix; this in turn produces a
tight, impermeable seal within the vessel, thereby maximally
inhibiting the delivery of blood to downstream blood vessels and
tissues.
[0058] For example, the introduction of a platelet-binding particle
into the blood stream would proceed through the following sequence
of events: a) a single layer of platelets would form on the surface
of the particle thereby forming (i) a particle of increased
diameter and (ii) a particle coated with activated platelets with
the propensity to bind and activate nearby platelets in suspension,
herein defined as `single-layered surface activated platelets`
particle (S-SAP particle), b) platelets flowing in the blood stream
would interact with platelets bound to the S-SAP particle forming
`onion-like` layers, herein defined as `multi-layered surface
activated platelet particle (M-SAP particle), c) M-SAP would
interact with each other through platelet/platelet interaction
forming larger aggregates, herein defined as the `M-SAP
matrix`.
[0059] As a further example, the introduction of the amorphous
platelet binding particle polylactide, polyglycolide or
polylactide-co-glycolide particles coated with mammalian collagen
into the blood stream would proceed through the following sequence
of events: a) single platelets would bind on and within the matrix
of the particle thereby forming (i) a particle with increased
diameter and rigidity, (ii) a particle coated with and containing
activated platelets with the propensity to bind and activate nearby
platelets in suspension; b) platelets flowing in the blood stream
would interact with the platelets bound to and/or bound within the
particle thereby forming aggregates within and/or on the particle,
c) particles containing and/or having surface bound platelets would
interact with each other to form large particle aggregates.
[0060] 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, starving or reducing the nutrient supply to a
hyperplastic tissue or cancer, repairing AV-malformations, reducing
or preventing blood loss from endoleaks and repairing vessel
aneurysms.
[0061] As used herein, "administering" refers to any action that
results in delivering a composition containing a solid-phase agent
to 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, the
vasculature of tumor or hyperplastic tissue may be exposed. In
accordance with an embodiment of the invention, the exposed cells
or vasculature may be exposed directly to a composition of the
present invention, e.g., by washing or irrigating the surgical
site, vasculature, and/or the cells.
[0062] The solid-phase platelet-binding agent can be localized to a
specific target site using a binding or targeting agent. Exemplary
binding or targeting agents include, but are not limited to:
monoclonal antibodies; polyclonal antibodies; chimeric monoclonal
antibodies; humanized antibodies; genetically engineered
antibodies; fragments of antibodies, selected from the group
consisting of F(ab)2, F(ab')2, Fab, F(ab'), Dab, Fv, sFv, scFv, Fc,
and minimal recognition unit; single chains representing the
reactive portion of monoclonal antibodies (SC-Mab); 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 (paired with its
complementary anti-ligand); 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.
[0063] Monoclonal antibodies useful in the practice of the present
invention include whole antibodies 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. See, generally, Kohler and
Milstein, Nature, 256:495-97, 1975; Eur. J. Immunol., 6:511-19,
1976. The preferred binding and/or targeting agent capable of
localizing the solid-phase agent to a target site is an antibody or
antibody-like molecule, preferably a monoclonal antibody. A more
preferred binding agent is an antibody that binds a ligand/receptor
complex on hyperplastic tissue or cells (e.g., tumor) or the
vasculature associated with hyperplastic tissue or cells. The most
preferred binding agent is an antibody or antibody-like molecule
that binds a growth factor/growth factor receptor complex either on
or in the vicinity of the tumor mass such as the tumor vasculature.
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 due to ligand/receptor (i.e., 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 growth factor/growth factor receptor complex would not
affect the function of either the growth factor or the growth
factor receptor.
[0064] 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.
[0065] 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, such minimal polypeptides exhibiting the
binding affinity of the targeting moiety.
[0066] 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 antibodies recognizing a ligand/receptor
complex.
[0067] 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 components of 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.
[0068] It may be desirable to prepare and employ an antibody or
other binding agent or moiety having a relatively high degree of
selectivity for tumor vasculature, together with little or no
reactivity with the cell surface of normal endothelial cells as
assessed by immunostaining of tissue sections. It may also be
desirable to prepare and employ an antibody or other binding agent
or moiety capable of binding an epitope common to all
vasculature.
[0069] Any composition that includes a solid-phase platelet-binding
agent with or without a targeting agent according to the invention
may be used to initiate an in vivo therapeutic benefit, thrombus
formation, and/or cell killing or regression. 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 and buffers. 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, non-pyrogenic and free
of undesirable particulate matter. The compositions may be
sterilized by conventional sterilization techniques.
[0070] In a preferred embodiment of the invention, a suitable
composition includes a binding or targeting agent that binds to
ligand/receptor complex. Exemplary antigens useful as targets in
accordance with the present invention include, but are not limited
to, antigens associated with cancer, including, lung, colon,
rectum, breast, ovary, prostate gland, head, neck, bone, immune
system, blood, or any other anatomical location. Exemplary antigens
and/or pre-determined sites include but are not limited to
VEGF/VEGF receptor complex, FGF/FGF receptor complex, or
TGF.beta/TGF.beta receptor complex, p-selectin, sialyl-lewis X,
endothelin, endothelin receptor, endothelin/endothelin receptor
complex, alpha-fetoprotein, platelet-endothelial cell adhesion
molecule (PECAM), CD31, CD34, CD36, glycoprotein Ib (GPIb),
endoglin, thrombomodulin, endothelial leukocyte adhesion molecule
(ELAM), intercellular adhesion molecule 1 (ICAM-1), MHC-I, and
MHC-II. The subject may be a human or animal subject.
[0071] As noted above, a composition or method of the present
invention includes a platelet binding agent or component. In the
present invention the preferred platelet binding agent is
collagen.
[0072] 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 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.
[0073] 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), proteinase-activated receptor (also
known as protease activated receptor, PAR) agonists, 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, von Willebrand factor (VWF), matrix
metalloproteinases (MMPs), heparin, heparan sulfate, chondroitin
sulfate, ionophores, complement cascade components (e.g., C5b-9)
platelet microparticles, platelet membrane fractions.
[0074] 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.
[0075] Exemplary platelet-mediated occlusion retarders include but
are not limited to aspirin, ibuprofen, acetaminophen, ketoprofen,
ticlopidine, clopidogrel, indomethacin, dipyridamole, omega-3 fatty
acids, prostacyclin, nitric oxide, inducers of nitric oxide,
inducers of nitric oxide synthase, matrix metalloproteinase
inhibitors (MMPIs, TIMPS), anti-GPIIb/IIIa agents,
anti-.quadrature.v.quadrature.3 agents,
anti-.quadrature.2.quadrature.1 agents, anti-CD36 agents, anti-GPVI
agents, aurintricarboxylic acid, thrombin receptor antagonists,
thromboxane receptor antagonists, streptokinase, urokinase, tissue
plasminogen activator (tPA).
[0076] In addition, it is known that platelets that 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., in 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 PGLA/Collagen. 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.
[0077] 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.
[0078] In accordance with the invention, two, 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.
[0079] In accordance with a method of the invention, the binding
agent must be capable of binding a ligand/receptor complex, 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, intra-arterial, subcutaneous,
intraperitoneal, intrathecal, intravesical, intradermal,
intramuscular, or intralymphatic route. The composition may be in
solid, 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 or serum may
be removed from the patient; optionally, it may be desirable to
purify the antigen in the patient's blood; the blood or serum may
then be mixed with a composition that includes a binding agent or
the solid-phase agent according to the invention; and the treated
blood or serum 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.
[0080] Administration may be once, more than once, or 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 solid-phase 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).
[0081] A solid-phase 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,
embolizing agents such as Gelfoam or polyvinyl alcohol (PVA)
particles or the like.
[0082] As is well known in the art, a disadvantage associated with
administering treatment agents or treatment 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
treatment 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 a toxic threshold.
[0083] In accordance with a preferred embodiment of the invention,
therefore, un-activated platelets accumulate or are induced to
accumulate at a pre-determined site through binding to the
solid-phase agent, and then the properly localized platelets are
selectively activated.
[0084] In accordance with a preferred embodiment of the invention,
activated platelets accumulate or are induced to accumulate at a
predetermined site through binding to the solid-phase agent or
through platelets bound to the solid-phase agent.
[0085] The effectiveness of the present invention may be monitored
by conventional assays that determine thrombus formation,
morphometric studies of thrombus formation, tumor necrosis, tumor
size, tumor morphology, and/or thrombus formation that results in
tumor necrosis, blood flow studies (e.g., angiography, Doppler
ultrasound, radiography, CT scan, MRI), or reduction in pain
symptoms. One skilled in the art will recognize that other tests
may be performed to assess or monitor therapeutic benefit.
[0086] 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).
[0087] Exemplary pro-thrombotic or pro-coagulant conditions that
may warrant the using of controllers, retarders, or agents that
diminish a method or composition of the invention include, but are
not limited to, 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 include a risk of hemorrhage 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. 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.
[0088] As an example of the foregoing, it will be recognized by
those skilled in the art that upon initiation of the vascular
occlusion process, reversal or dampening of the associated
prothrombotic condition may be necessary. 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,
ibuprofen, acetaminophen, ketoprofen, ticlopidine, clopidogrel,
indomethacin, omega-3 fatty acids, prostacyclin, nitric oxide,
inducers of nitric oxide, inducers of nitric oxide synthase, matrix
metalloproteinase inhibitors (MMPIs, TIMPs), anti-GPIb 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).
[0089] 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,
platelet substitutes and whole blood.
[0090] 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), PAR agonists,
cathepsin G, elastase, arachidonate, thromboxane A2 (TxA2)
mimetics, TxA2, phospholipase A2 (PLA2), activators of protein
kinase C (PKC), adenosine diphosphate (ADP), collagen, von
Willebrand factor (VWF), matrix metalloproteinases (MMPs), heparin,
heparan sulfate, chondroitin sulfate, ionophores, platelet
microparticles, platelet membrane fractions.
[0091] Once introduced into the bloodstream of an animal bearing a
tumor, hyperplastic tissue, AV-malformation, aneurysm or endoleak,
the solid-phase agent will localize in the target vasculature; bind
or immobilize platelets, whereby immobilization activates the
platelets; and the activated platelets in turn bind and activate
other platelets until an occlusion is formed. Platelet activation
and binding facilitates leukocyte binding to the activated
platelets further enhancing occlusion of the target
vasculature.
EXAMPLES
Example 1
[0092] 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 four or more 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-week 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.
[0093] From the resultant collection of hybridomas, one will 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. 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, for example, 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 test for the absence of reactivity
against non-activated or "normal" endothelium or other normal
tissue or cell types. 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
[0094] 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. Female BALB/c
mice are immunized with HPLC-purified recombinant VEGF and VEGF
receptor (soluble VEGF/FLT-1 receptor or VEGF/KDR receptor, as
examples) in complex in the presence of an adjuvant such as Quil A.
After the appropriate antibody titre is reached (usually following
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
[0095] A variety of endothelial cell markers are known that can be
employed as existing or 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 likely be preferred.
Monoclonal antibodies or specific peptides recognizing the above
endothelial cell antigens can be bound to the solid-phase agent,
such as particles coated with VWF, and delivered to target
vasculature by means of a catheter or similar delivery device. The
particles are thereby bound to the endothelial cells in the target
vasculature leading to platelet binding and platelet activation on
the particle, which in turn leads to platelet aggregation about the
particle and eventually thrombus formation. The formed thrombus
occludes the targeted vasculature thereby preventing delivery of
oxygen and nutrients to the down-stream tissue.
Example 4
[0096] Targeting platelets to a specific site may take the form of
platelets binding directly to the solid-phase agent through
interaction VWF immobilized on the solid-phase agent. For example,
recombinant and/or human and/or porcine VWF immobilized on a
particle of an approximate diameter of 1 .mu.m to 5 mm can be
delivered to a target site by various means, such as by catheter.
Platelet binding can take place after delivery of the VWF-particle
to the target vasculature whereby platelets flowing in the blood
stream contact the particles, bind to the particles, spread across
the particles, activate, bind other platelets and eventually form a
thrombus that occludes the blood vessel. Platelet binding to the
VWF-particle can also be initiated ex vivo, whereby the platelets
contact the particles in a vessel outside the body, and are
subsequently delivered to the target site by means of a catheter or
similar agent delivery device. Particle size is selected such that
upon initiation of platelet reactivity with the particles (i.e.,
platelet binding to the particles) progression of the particle
beyond the capillary bed cannot occur due to size limitations or
because of the particle-associated platelets and/or bound
coagulation proteins interacting with the vessel wall receptors.
VWF particle sizes, therefore, could range from about 1 .mu.m to
about 5 mm in diameter. Most preferably the particles will range
between 5 .mu.m and 2 mm in diameter. An even more preferable
diameter of the particle would be between 20 .mu.m and 300
.mu.m.
Example 5
Particles
[0097] Particles of various compositions can be used as solid-phase
agents for the purpose of the present invention. The following
particles have been tested for their ability to bind agents that
bind platelets. Polystyrene microspheres were purchased from
Polysciences Inc., (Warrington, Pa.) and coated with human von
Willebrand factor through a passive adhesion process (incubation in
0.2M carbonate buffer, pH 9.0-9.6) or through a covalent linkage to
derivatized beads using carbodiimide or glutaraldehyde. Several
types of beads were tested including plain polystyrene microspheres
(cat. # 07310, 17134, 17135, 07312, 07313, 07314), polybead amino
microspheres (cat. # 19118), polybead carboxylate microspheres
(cat. # 17141), fluoresbrite microspheres (cat. # 17155, 17156),
polystyrene dyed microspheres (cat. # 15715, 15714, 15716), and
paramagnetic particles (cat. # 19829). All beads bound von
Willebrand factor, and upon subsequent testing bound platelets.
Binding of platelets to the beads was confirmed by aggregometry and
phase contrast microscopy.
[0098] Other particles tested included polyvinyl alcohol (PVA)
particles (Cook, Bloomington, Ind.) and macro-aggregated albumin
(MM) particles (Edmonton Radiopharmaceutical Centre, Edmonton,
Alberta, Canada). In separate experiments, von Willebrand factor
was bound passively (carbonate buffer, as above) and covalently
(glutaraldehyde linkage, as above) to the particles. Binding of
platelets to the particles was then confirmed using aggregometry,
phase contrast microscopy and fluorescence microscopy (anti-CD61
antibody labeled with FITC).
Example 6
Comparison of Mammalian VWFs
[0099] Porcine VWF, bovine VWF, and human VWF were immobilized on
polystyrene particles using two approaches. The first approach
(direct binding) employed passive adsorption of the material to the
solid-phase particle in the presence of 0.2M carbonate (pH 9.35).
The second approach (indirect binding) consisted of the isolation
of VWF from porcine, bovine, and human plasmas, respectively, using
an anti-VWF antibody that had been immobilized on the surface of
the solid-phase particle. In the latter approach, the antibody
(rabbit source) used was purchased from Dako (Mississauga, Ontario;
cat #A0082), and as per information provided by the manufacturer,
was confirmed to bind human, bovine and porcine von Willebrand
factor. The antibody was fixed to polystyrene beads (4.5 .mu.m in
diameter) by passive adsorption in carbonate buffer (0.2M, pH 9.35)
and incubated with the respective source plasmas for 60 minutes at
room temperature. The beads were washed free of unbound protein and
used to challenge whole blood and platelet rich plasma from humans
and pigs. In a like manner, human, porcine and bovine VWFs were
individually bound directly to the beads (i.e. without a linking
antibody) by passive adsorption as outlined above, and used to
challenge human and porcine platelets (whole blood and platelet
rich plasma [PRP]). In some experiments, porcine and human PRP were
mixed together and challenged with the various agents (see
below).
TABLE-US-00001 Immobilized VWF Ab Whole 50:50 PRP Direct Capture
Source VWF Blood PRP (human:porcine) -- Human Human ++++ Human ++++
+++++ Porcine + Porcine + -- Human Human ++++ Human ++++ +++++
Porcine + Porcine + -- Porcine Human +++++ Human +++++ +++++
Porcine +++ Porcine +++ -- Porcine Human +++++ Human +++++ +++++
Porcine +++ Porcine +++ -- Bovine Human + Human + + Porcine +
Porcine + Bovine Human + Human + + Porcine + Porcine + + weak
platelet reaction, ++ moderately weak platelet reaction, +++
moderate platelet reaction, ++++ strong platelet reaction, +++++
very strong platelet reaction
Example 7
White Cell Interaction
[0100] Particles bound with porcine or human VWF characteristically
bound human or porcine platelets, depending on the source blood. In
addition, white cells including monocytes, granulocytes and
lymphocytes were observed to interact with the platelets bound to
the particles (confirmed by differential staining and microscopic
examination).
[0101] Platelet activation at the target site induces 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) inhibit angiogenesis. Post activation
platelet release of chemoattractants such as RANTES enhance the
effects of leukocytes (e.g., eosinophils, monocytes) on target
tissue. Post activation expression by the platelets of granular
constituents such as CD62 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 induces tissue factor
expression by monocytes leading to a local hyper-coagulable
state.
Example 8
[0102] The solid-phase agent can also take the form of a coil or a
stent. VWF of recombinant or mammalian origin can be bound to these
solid phase agents and delivered to the target vasculature by
various means including surgery and/or by catheter. The target
site, such as an aneurysm, can be reached through the blood stream
using specific catheters and associated guide wires. A guide wire
is introduced into the vascular system through an entry site such
as the femoral artery and gently pushed through the major blood
vessels to the target site. The catheter is introduced over the
guide wire to the target site, whereupon the guide wire is removed.
The solid-phase platelet-binding coil is then pushed through the
lumen of the catheter to the aneurysm where it is deployed. VWF
bound to the coil specifically binds platelets flowing in the
bloodstream. The platelets activate and accumulate about the coil
rapidly, thereby forming a localized stationary thrombus, in turn
reducing the risk of aneurismal rupture.
Example 9
Acute Effects of Particle-immobilized VWF in a Porcine Model
[0103] The study was designed to evaluate the effectiveness of
particles coated with human VWF in inducing thrombus formation in
the vasculature of the pig kidney. In this procedure, the renal
artery was catheterized using a 20-22 gauge angiocatheter. The
renal vessels were exposed by surgery and a Doppler flow probe
attached to the renal vessels to monitor blood flowing into and out
of the target organ. No noticeable difference was seen between flow
readings taken from the renal artery and vein; therefore, all
readings were further taken from the renal vein to be indicative of
blood flow through the target kidney. Human VWF was covalently
bound to human MAA by overnight incubation with glutaraldehyde.
Previous titration studies varying the amount of VWF bound to MAA
on a per weight protein basis had established that ratios of 1:5
through 1:80 (MAA:VWF) provided sufficient immobilized VWF to
induce platelet binding and activation. On this basis, a ratio of
1:20 (MAA:VWF) was chosen for in vivo studies. Particle analysis by
phase contrast microscopy demonstrated that the particle size in
the final preparation ranged from 30 .mu.m through to 250 .mu.m (as
estimated by light microscopy using a
micrometer/hemacytometer).
[0104] Injection of MAA/VWF (500 .mu.l or 1 ml) followed by human
PRP (500 .mu.l containing approximately 200--400.times.10.sup.6
platelets) into the renal artery of the pig caused a dramatic
decrease in blood flow. Human platelets were injected after the
test agent to approximate conditions within a human as closely as
possible. In addition, binding of porcine platelets to human VWF
was noted to be very weak (see Example 6, above). Within 10 minutes
of injection of the test agent, the blood flow had dropped to less
than half of baseline levels. Within 15 minutes of injection of the
test agent, the blood flow had dropped to less than 20% of the
baseline values. Blood flow to the organ did not increase during
the 90-minute monitoring period.
[0105] Conversely, control agent (MM alone; identical protein
concentration) injected into the renal artery of the contra lateral
kidney showed a transient decrease in blood flow. The blood flow
decreased by 50% initially, but rapidly returned to near baseline
levels, i.e., >80% of original blood flow within 15 minutes and
>90% of original blood flow within 30 minutes.
[0106] Histological examination of the target vasculature revealed
a large thrombus in the immediate branches of the renal artery in
the test organ with minor thrombosis of the renal vasculature in
the control kidney. No thrombi were noted in the liver, lungs,
spleen, brain, heart and eyes of the control or test animals.
Example 10
Chronic Effects of Particle-Immobilized VWF in a Porcine Model
[0107] In a manner similar to the procedure outlined in Example 9,
the renal arteries of two test and two control pigs were
catheterized using 20-22 gauge angiocatheters. A Doppler flow probe
was placed surgically on the renal vein of each animal and the lead
wires exposed on the outer skin of the animal after closing the
initial incision. After establishing a baseline for blood flowing
through the affected kidney, 1 ml of MAA:VWF particles (11 mg total
protein) followed by 1 mL human platelet rich plasma (approximately
460.times.10.sup.6 platelets (platelet count
458.times.10.sup.9/liter) were injected into the renal arteries of
the test animals, and an identical amount of MAA was injected into
the control animals. The animals were transferred to metabolic
crates and monitored at varying time intervals over a 7-day period.
The following table presents blood flow results from these
studies.
TABLE-US-00002 PORCINE DOPPLER BLOOD FLOW (milliliters per minute)
Day Test 1 Control 1 Test 2 Control 2 0 28 70 35 35 1 17 15 11 103
2 32 24 15 71 3 3 109 16 85 4 3 101 17 78 5 3 140 3 65 6 1 140 0 55
7 3 148 2 30
The major organs and tissues of the control and test animals were
examined histologically for evidence of thrombosis and other
treatment-associated damage. No thrombosis was observed except in
the renal vasculature of the target kidney.
Example 11
MAA/VWF Labeling with Sodium Pertechnetate Tc 99m
[0108] MAA/VWF particles were prepared by conjugating human VWF
(source Alphanate, Alpha Therapeutics Corp.) to MAA particles (11
mg protein; source MAA for injection, Edmonton Radiopharmaceutical
Centre) using glutaraldehyde (0.0625% v/v, final). The protein
ratios ranged from 40:1 to 20:1 (MAA:VWF). The functionality of the
particles was checked by challenging citrated platelet rich plasma
and citrated whole blood from a healthy non-medicated (greater than
2 weeks) volunteer with the MAA/VWF particles with stirring at 500
rpm for 10 minutes (10 .mu.l particles+100 .mu.l platelet source).
Observation of the reaction by phase contrast microscopy confirmed
the ability of the particles to bind and activate platelets,
forming large masses of platelets and MAA/VWF particles.
[0109] The MAA/VWF particles were then labeled with sodium
pertechnetate Tc 99 m using activities ranging from 88 MBq to 300
MBq. Equal volumes of the particles in saline and sodium
pertechnetate Tc 99m were incubated at room temperature for 10
minutes. Labeling efficiency was determined using thin layer
chromatography and found to be in excess of 95%.
[0110] The Tc 99m labeled MAA/VWF particles were then tested to
evaluate the effect of the labeling on the functionality of the
particles. Phase contrast microscopy confirmed that the Tc 99m
labeled MAA/VWF particles were capable of binding and activating
platelets. There was no apparent reduction in the functional
activity of the labeled particles.
Example 12
Fluoroscopy Studies of MAA/VWF Thrombosis of Porcine Renal
Vasculature
[0111] MAA/VWF was delivered to porcine renal vasculature using a
femoral artery approach. A 5-Fr sheath catheter was inserted into
the femoral artery of 18 to 20 kg piglets after general anesthesia
(halothane) and guided by fluoroscopy to the left renal artery. The
catheter was positioned such that upon delivery of contrast dye,
only the lower pole of the kidney's vasculature was visualized. At
time zero 1 ml of MAA/VWF particles (size range 30-250 micron) were
delivered slowly (over 10 seconds) to the renal vasculature. Ten
(10) seconds later 1 ml human PRP (420.times.10.sup.9 per liter)
was delivered and the catheter flushed with 1 ml saline. The
catheter was kept in place and after a twenty (20) minute waiting
period contrast agent was again delivered to the target
vasculature. The contrast agent was observed to pool at the end of
the catheter then move rapidly into the vasculature of the upper
pole of the kidney. The vasculature of the lower pole of the kidney
slowly accumulated contrast agent that did not dissipate (greater
than 20 minutes), while the upper pole vasculature rapidly lost the
contrast agent (less than 5 seconds). With the animal under
anesthetic and the catheter still in place, the affected kidney was
surgically exposed, the renal vasculature clamped just proximal to
the catheter and the affected kidney removed. The renal artery was
opened through a longitudinal incision and dissected toward the
kidney. A large thrombus was noted distal to the tip of the
catheter extending deep within the vasculature of the lower pole of
the kidney. No clotting was noted in the vasculature of the upper
pole of the kidney. In addition, the lower pole of the affected
kidney was noticeably blanched indicating a lack of blood flow,
while the upper pole of the kidney exhibited normal red
coloration.
[0112] In a separate experiment following the above outlined
procedure the catheter was directed to the vasculature of the lower
pole of the target kidney and used to deliver 1 ml of MAA/VWF
particles followed by 1 ml of human PRP. After 20 minutes blood
flow to the lower pole of the kidney was notably impeded as
determined by fluoroscopy. As before, the contrast dye moved
rapidly into the upper pole vasculature after pooling at the tip of
the catheter. The catheter was then repositioned and MAA/VFW
followed by human PRP was delivered to the upper pole vasculature.
After a 20 minute waiting period contrast dye was again injected.
Fluoroscopy revealed that blood flow to the upper pole vasculature
was blocked. The contrast dye did not enter the lower pole
vasculature. The target kidney with associated renal vessels was
then removed surgically prior to sacrificing the animal. Immediate
dissection of the kidney revealed extensive thrombosis of the blood
vessels in both the upper and lower poles of the kidney.
Example 13
Preparation of Collagen-Coated Particles
[0113] Various sources of collagen were bound to different particle
types by passive adsorption, or chemical conjugation.
[0114] Collagen derived from calf-skin and bovine tendon (Sigma; St
Louis, Mo.), was bound to 4.5 .mu.m diameter polystyrene particles
(Polybead; Polysciences Corp.; Warrington, Pa.) through passive
adsorption by overnight incubation in the presence of mild acid.
The particles were washed free of unbound collagen by
centrifugation (3 cycles; saline, 0.15 M) and left suspended in
saline. The particles were stored at 4.degree. C. until needed.
[0115] Collagen purchased from Bard Inc. as Avitene flour (Bard;
Murray Hill, N.J.) was solubilized in mild acid and covalently
bound to 100 .mu.m diameter polylactic acid (PLA) particles (G.
Kisker, Germany) using EDC (Sigma) as a linking agent (3 hrs,
22.degree. C.). Acid-solubilized Avitene was covalently bound to
100-135 .mu.m diameter polylactide-co-glycolide (PLGA) particles
(PolyMicrospheres; Indianapolis, Ind.), or 240 .mu.m PLGA particles
using glutaraldehyde (Fisher Scientific Inc., Edmonton, Canada) as
a linking agent. Conjugations were accomplished by overnight
incubation using glutaraldehyde. The particles were washed free of
unbound collagen, blocked with 1% (w/v) bovine serum albumin (BSA)
and left suspended in PBS. The particles were stored at 4.degree.
C. until needed.
Example 14
Detection of Collagen Bound to Particles
[0116] Collagen bound to the various particle types was detected
using a collagen-specific monoclonal antibody. Particles were
incubated with saturating concentrations of anti-collagen IgG
(Sigma) for 1 hour at 22.degree. C. After washing away unbound
antibody, the particles were incubated with saturating amounts of
goat anti-mouse IgG-FITC for 1 hour at 22.degree. C. (Sigma). After
washing away unbound antibody, the particles were observed by
fluorescence microscopy. Bovine serum albumin (BSA) coated
particles served as negative control.
Example 15
Collagen-Coated Particle Mediated Platelet Activation
[0117] Collagen coated particles (acid-soluble, fibrillar, Avitene)
were mixed with citrated whole blood from healthy non-medicated
donors to determine the effect of the particles on platelet
activation. Agitation of the reaction mixture was accomplished by
mixing on a rotary shaker in microwells. Particle-dependent
platelet activation was assessed by phase contrast microscopy and
by a platelet counting technique. Mixing collagen-coated particles
with whole blood induced platelet activation and binding to the
particles. In contrast to the addition of acid soluble collagen
(i.e. not particle bound), which caused extensive platelet
aggregation observed as platelet clumps in the reaction mixture,
the collagen-particle-activated platelets remained localized to the
particle surface facilitating particle bound platelet aggregation.
Platelet counts post-mixing were significantly less than the
starting platelet counts as determined by automated cell counting
(Coulter Ac.T; Coulter, Fullerton, Calif.).
Example 16
Inhibition Studies
[0118] Citrated whole blood from healthy, unmedicated donors was
incubated with saturating concentrations of anti-GPIb antibody,
clone AK2 (Biodesign International; Saco, Me.). The whole blood was
then challenged with decreasing numbers of collagen-coated
polystyrene microspheres. BSA microspheres were used as negative
control. The results of the experiments are shown in the table
below.
TABLE-US-00003 Percent Platelets Remaining Percent Platelets
Remaining After Reaction After Reaction (100% test agent) (1:1
dilution of test agent) Agent Donor 1 Donor 2 Donor 3 Donor 1 Donor
2 Donor 3 Collagen Coated 0.93 1.1 2.39 4.97 6.29 93.99 Polystyrene
Microspheres Collagen Coated 1.31 5.92 34.2 23.2 75.89 100.18
Polystyrene Microspheres + Anti GP1b Change in 1.4-fold 5.4-fold
14.3-fold 4.7-fold 12.1-fold 1.1-fold Platelet decrease decrease
decrease decrease decrease decrease Reactivity
[0119] Anti-GPIb antibody significantly reduced platelet reactivity
with the collagen-coated microspheres indicating that the platelets
were activated by an immobilized VWF-dependent mechanism. This
result is not surprising since collagen exposed as part of the
subendothelium is known to bind circulating VWF, which in turn
serves to capture platelets flowing past the area of vascular
damage.
[0120] In a separate series of experiments, PLGA coated collagen
microspheres were used to challenge, whole blood that had been
incubated with saturating concentrations of anti-GPIb, collagen
particles that had been incubated with anti-collagen antibodies.
The results of the experiments are shown in the table below.
TABLE-US-00004 Percent Platelets Remaining Test Agent After
Reaction Collagen Coated PLGA particles 9.7 Collagen Coated PLGA
particles + 90.2 anti collagen antibody Whole Blood + anti GPIb
antibody 54.6
[0121] Both the anti-GPIb and the anti-collagen antibodies reduced
platelet reactivity with the PLGA/collagen microspheres. The
results demonstrate that platelets are activated in the presence of
PLGA/collagen microspheres through two mechanisms, a VWF-dependent
and a VWF-independent mechanism. Since collagen is required to
capture VWF from the whole blood, treating the collagen-coated
microspheres with anti-collagen antibody inhibited VWF binding to
the collagen. In addition, collagen-dependent platelet activation
through other receptor pathways was essentially eliminated. In
contrast, inhibiting VWF/platelet interaction by blocking GPIb, had
no effect on the collagen-dependent platelet interaction. The
results demonstrate that both pathways contribute to PLGA/collagen
microsphere-dependent platelet activation. The results also support
the use of inhibitors to modulate platelet activation induced by
solid-phase platelet binding agents in an in vivo setting.
[0122] 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.
* * * * *