Note: Descriptions are shown in the official language in which they were submitted.
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COMPOSITIONS FOR TREATMENT OF TUMORS BY DIRECT
ADMINISTRATION OF A RADIOISOTOPE
Cross Reference to Related Applications
This application claims priority from US Provisional Patent Applications
60/997,856 and 60/997,873, both filed on October 5, 2007. This application is
related to US Provisional Patent Applications 60/890,831 entitled,
"Directional Bone
Drilling and Methods of Treatment" filed on February 20, 2007 and 60/891,183
entitled, "Directional Bone Drilling and Methods of Treatment" filed on
February 22,
2007.
Field of the Invention
The present invention concerns treatment of undesirable tissue masses,
such as bone cancer or soft tissue tumors, in mammals and humans by direct
administration of a radioisotope formulation directly to the area of the
tissue mass,
i.e., via intratumural, intramedullary or intraosseous injection.
Background of the Invention
The treatment of cancerous tumors or masses of undesirable tissue has been of
concern for many years with various attempts to have effective treatment to
prolong
the quality of life of the mammal or human. Various compositions have been
tried
and the following discussion of bone tumor and soft tissue tumor are discussed
below.
Bone Cancer
According to the American Academy of Orthopaedic Surgeons, "More than
1.2 million new cancer cases are diagnosed each year [in the US], and
approximately
50 percent of these tumors can spread or metastasize to the skeleton."
Metastatic
bone cancer therefore afflicts over 500,000 patients in the US alone. Bone is
the third
most common site of metastatic disease. Cancers most likely to metastasize to
bone
include breast, lung, prostate, thyroid and kidney. In many cases there are
multiple
bone metastatic sites making treatment more difficult. Pain, pathological
fractures
and hypercalcemia are the major source of morbidity associated with bone
metastasis.
Pain is the most common symptom found in 70% of patients.
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Primary bone cancer is much less prevalent (2,370 new cases and 1330 deaths
estimated in the US for 2007) but it is much more aggressive. This type of
cancer is
more likely to occur in young patients. In contrast to people, primary bone
cancer is
more prevalent in dogs than metastatic bone cancer. Large dogs frequently
present
with primary bone cancer. Because of the aggressive nature of the disease,
primary
bone cancer is often treated by amputation of the area affected to prevent the
cancer
from spreading. In addition, chemotherapeutic agents are then used to decrease
the
chance of metastatic disease, especially to the lungs.
The pain associated with bone cancer, especially metastatic bone cancer, is
often treated with narcotics. However, the patients have need for increasing
amounts
of narcotics to control the pain. The side effects of the narcotics result in
a significant
decrease in the patient's quality of life.
Another method for treatment is external beam radiation or more recently
stereotactic radiotherapy of bone metastatic sites. However, current
treatments with
high energy electromagnetic radiation do not exclusively deliver radiation to
the
tumor. This treatment results in the necessity to administer the dose over
about a
week and has the difficultly of giving high doses of radiation to a tumor
without
significant damage to surrounding tissue.
Intraoperative Radiation Therapy (TORT) has permitted localized tumor
destruction, but this is expensive and associated with significant trauma due
to
surgery.
Certain bone seeking radiopharmaceuticals which can be used in the present
invention do not require the use of a chelating agent. For example P-32 can be
used
alone as a bone seeking radiopharmaceutical without a chelant present. Also,
Sr-89 as
the chloride can be used, as indicated in Robinson R G, Spicer J A, Preston D
F, et al.,
"Treatment of Metastatic Bone Pain With Strontium-89," Nucl. Med. Biol. 14:219-
222
(1987).
The ability to target bone tumors has been exploited in the field of
radiopharmaceuticals for many years. Both diagnostic and therapeutic
radiopharmaceuticals capable of targeting bone tumors generally use phosphonic
acid
functionality as the targeting moiety. For example, pyrophosphates have been
used to
deliver Tc-99m, a gamma-emitting diagnostic radioisotope, to bone. This
technology
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was displaced by the bisphosphonates because of their increased stability in
vivo. In
addition, therapeutic radiopharmaceuticals for bone tumors were developed in
the
1980's and 1990's. Of these, a series of chelates based on
aminomethylenephosphonic acids offer another type of functionality useful for
targeting bone tumors. Thus ethylenediaminetetramethylenephosphonic acid
(EDTMP) has been shown to be a very good chelating agent for delivering metals
such as Sm, Gd, Ho, and Y to the bone.
Two radiopharmaceuticals, both based on radioactive metals, are marketed in
the United States for the treatment of bone metastases. Metastron is an
injectable
solution of strontium-89 (Sr-89) given as the chloride salt. Quadramet is a
phosphonic acid (EDTMP) chelate of samarium-153 (Sm-153). Both of these agents
concentrate in normal bone as well as in the metastatic lesions. This gives a
radiation
dose to the bone marrow resulting in temporary but significant suppression of
the
immune system. For that reason these agents are contraindicated when
chemotherapeutic agents are planned. Thus a patient may suffer from bone pain
while
waiting to receive a chemotherapeutic regimen for the primary cancer.
When these available chelates are injected intravenously, about 50% of the
injected dose concentrates in the bone. The rest is efficiently cleared by the
kidneys
and into the bladder; however, because of this clearance, toxicity to these
organs has
been observed when administering large therapeutic doses of bone seeking
radiopharmaceuticals. The amount of radiometal deposited at the site of a bone
tumor
is significantly higher that in normal bone. Although the chelate
concentration in the
site of a tumor is as much as 20 times that of normal bone, significant
amounts of
radioactivity are taken up by normal bone. The dose from the bone to the bone
marrow can suppress bone marrow. Even though this effect is usually temporary
and
marrow cells recover, the use of these agents are contraindicated when used
with
chemotherapeutic agents that also suppress bone marrow. Therefore therapeutic
bone
agents are typically not used at the same time chemotherapeutic agents are
used. In
addition, only a small fraction of the radiation dose is associated with the
tumor.
Because of the fast kidney clearance and uptake in normal bone, only about
0.1% of
the dose goes to the site of the tumor. Administration of larger doses of bone
agents is
limited by the dose to the bone marrow.
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An example of the bisphosphonate chelant, methylenediphosphonic acid
(MDP), is shown in the structure below.
H
H) / O
/ C \ ~
HO -P P--,
I I OH
O OH
MDP
Two aminomethylenephosphonic acid chelants, ethylenediaminetetra-
methylenephosphonic acid (EDTMP) and 1,4,7,10-tetraazacyclododecane-1,4,7,10-
tetra(methylenephosphonic acid) (DOTMP), are shown in the structures below.
H O P N N PO H
2 3 32
H2O3P PO3H2
EDTMP
H203P---\\ F-~ / P03H2
N N
I:N N
H2O3P~ \_j \-PO3H2
DOTMP
To date even combinations of treatments have not been effective at resolving
bone tumors. Thus it is still common practice to amputate a limb to stop the
spread of
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bone cancers. In the case of metastatic bone cancer, pain palliation and
maintaining
quality of life is often the goal in contrast to resolution of the tumors.
There clearly is
a need for more effective therapy to treat bone cancer.
Brachytherapy
In contrast to external beam radiotherapy, where an external beam of radiation
is directed to the treatment area (such as discussed above for bone tumors),
brachytherapy is a form of radiotherapy where a radioactive source is placed
inside or
next to the area requiring treatment. Brachytherapy is also known as sealed
source
radiotherapy or endocurietherapy and is commonly used to treat localized
prostate
cancer and cancers of the head and neck. Superficial tumors can be treated by
placing
sources close to the skin. Interstitial brachytherapy is where the radioactive
source is
inserted into tissue. Intracavitary brachytherapy involves placing the source
in a pre-
existing body cavity. Intravascular brachytherapy places a catheter with the
source
inside blood vessels.
In most of these cases the radioactive material is encapsulated in a metal
casing. Because of this casing, most of the radioactive sources are
electromagnetic
radiation (X-rays and gamma photons) emitting radionuclides such that the
radiation
can penetrate the outer casing and deliver a radiation dose to surrounding
tissue.
Administration of the radioisotope without this encapsulation may result in
migration
of the radioisotope to other areas of the body creating side effects in the
patient.
Particle emitting radionuclides such as beta ((3) and alpha (a) emitters are
rarely used
in this application because a significant portion of the dose would not
penetrate the
casing within which the isotope is contained. However, in many cases the gamma
photons penetrate beyond the desired treatment area resulting in significant
side
effects. Therefore, a more specific method to deliver radiation is needed.
The prostate is a gland in the male reproductive system located just below the
urinary bladder and in front of the rectum. It is about the size of a walnut
and
surrounds the urethra. In 2007 the American Cancer Society estimated 218,890
new
cases and 27,050 deaths due to prostate cancer in the U.S. Treatment options
include
surgery, external radiation therapy, and brachytherapy. In many cases
brachytherapy
is the preferred choice due to less trauma to surrounding tissues. However
since the
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radioisotopes selected for this application are gamma (y) emitters, delivering
an
undesired radiation dose to surrounding tissue remains a problem.
The radioactive sources used for brachytherapy are sealed in "seeds" or wires.
Permanent prostate brachytherapy involves implanting between 60 and 120 rice-
sized
radioactive seeds into the prostate. One type of radioactive seed is based on
1-125
which has a 59.4 day half life and emits multiple X-rays around 30 keV.
Recently a
shorter half life alternative has been proposed with Cs-131 which has a 9.7
day half
life and emits X-rays of about 30 keV. Alternatively, Pd-103 is used which has
a 17
day half life and emits X-rays of about 20 keV. Another option is Ir-192 which
has a
half life of 73.8 days and gamma emissions at 468 keV. Ir-192 can be used to
give
different doses to different parts of the prostate. All these isotopes emit
electromagnetic radiation that penetrates beyond the prostate and into normal
tissue
causing problems such as impotence, urinary problems, and bowel problems.
Although in most cases the seeds stay in place, seed migration does occur in a
portion
of patients. Usually the seeds migrate to the urethra or bladder.
In some cases, brachytherapy is used to destroy cancer cells left over after a
surgical procedure. For example breast cancer patients can be treated with a
technology by the name of MammoSite Radiation Therapy System. This involves a
balloon catheter that is inserted into the area of the breast where a tumor
was
removed. The balloon is expanded and radiation is delivered via a small bead
attached to a wire. Similarly, the space surrounding a resected brain tumor
can be
treated using a balloon catheter inflated with a radioactive solution of 1-
125. This
technology is called G1iaSite Radiation Therapy System (e.g. U.S. Patent
6,315,979).
In these cases the balloon prevents the radioactivity from going systemic.
Again, the
radioisotopes used are those emitting penetrating electromagnetic radiation
such as X-
rays or gamma rays.
Beta emitting radioisotopes are being used in what could be categorized as
brachytherapy. For example, liver cancer has been treated with a form of
brachytherapy. This technology called Selective Internal Radiation Therapy
(SIRT)
delivers radioactive particles to a tumor via the blood supply. The
radioactive
particles are positioned via a catheter in the hepatic artery, the portal
vein, or a branch
of either of these vessels. The catheter is guided to the branch of the blood
vessel that
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feeds the tumor, and then the microspheres are infused. The radioactive
microspheres
become trapped in the capillary beds of the tumor and the surrounding tissues
which
results in a more targeted radiation dose to the tumor. There are currently
two
products that take this approach, both are microspheres labeled with Y-90,
TheraSphere (MDS Nordion, Inc.), and SIR-Spheres (SIRTeX Medical).
TheraSpheres are glass microspheres which have a diameter of 25 10 m so they
are
trapped mainly within tumor terminal arterioles, which are estimated to have a
diameter of 8-10 m. SIR-Spheres are resin-based microspheres that are
approximately 32 pm in diameter. One issue with both of these products is that
a
portion of the radioactive microspheres can migrate to other tissues such as
the lungs
and cause undesired side effects.
Ho-166 bound to chitosan has also been proposed to treat cancer cells. Thus J.
Nucl. Med. 1988 Dec; 39(12):2161-6 describes a method to treat liver cancer by
administering the compound via the hepatic artery. However, "shunting" of
radioactivity to the lung has again been a problem. In addition, it is a
cumbersome
technique to determine the blood supply to the tumor and to deliver the
particles in the
selected blood vessels.
US Patent 5,320,824 describes the use of rare earth isotopes such as Sm-153
and Ho-166 bound to hydroxyapatite for the treatment of rheumatoid arthritis.
In this
process, the most of the radioisotope bound to hydroxyapatite either remains
in the
injected joint or is taken up by the synovial membrane surrounding the joint.
Localization to the target tissue depends on phagocytosis of the
hydroxyapatite
particles into the synovial membrane. One major problem with this approach is
leakage of radioisotope from the synovial cavity to other parts of the body.
As is evident from the discussion above, better technology to ablate
undesirable cells is needed. In the field of brachytherapy, more effective
methods of
delivering radioisotopes to tumors are needed that give a radiation dose
specifically to
the treatment area with little to no dose to non-target tissues.
Summary of the Invention
An aim of this invention is to provide a therapy that that can deliver
relatively
large radiation doses from a radioisotope in a minimal volume to the site of
an
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undesired tissue mass, including infections and cancerous tumors in both soft
tissue
and bone, for the purpose of killing said undesirable tissue. A further aim of
this
invention is to minimize the amount of radiation dose to non-target tissues in
order to
minimize side effects.
One aspect of this invention concerns a composition comprising a
therapeutically-effective amount of a radioisotope formulation having a pH
greater
than about 7 together with a pharmaceutically-acceptable liquid carrier, for
the
treatment of an undesirable tissue mass in an animal or human in need of such
treatment, wherein the composition is administered directly to or nearby the
tissue
mass, and the composition is such that less than about 15% of the radioisotope
migrates away from the site of administration within two half lives of
radioactive
decay.
A second aspect of this invention relates a composition for direct
administration of a therapeutically-effective amount of a radioisotope
formulation
wherein the radioisotope is bound to a binder, for the treatment of an
undesirable
tissue mass in an animal or human in need of such treatment, such that greater
than
about 5% of the radioisotope remains at the site of administration within two
half
lives of radioactive decay.
Both of these aspects are accomplished by the direct injection of a very small
volume of a liquid formulation mixture to the desired site. The radioactivity
delivered
to the site remains at the site of administration for a sufficient time to
give a
therapeutic radiation dose to that area. Compared to systemic administration
approaches, the total amount of radioactivity administered is very small and
the
amount of radioisotope that leaches out of the treatment area is minimal, thus
little to
no radiation dose to normal tissues is realized.
Administration of the radioisotope formulation can be via a microsyringe or
another device capable of delivering small volumes of fluid such as a small
pump. In
one embodiment of the invention for treating bone tumors, a miniature drill is
used to
create a hole by which a catheter can be inserted through the hole and a
device capable
of delivering small volumes of fluid is used to deliver the dose. In other
embodiments, a microsyringe can be used for delivery.
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This invention concerns a better therapeutic approach to the treatment of
cancer by the administration of a very small volume of therapeutic
radioisotope
directly to the tissue to be treated. Radioisotopes of this invention include
particle-
emitting isotopes such as alpha (a) emitters or beta (0) emitters that can
deposit
therapeutic amounts of ionizing radiation at the site of the tissue. The
radioisotopes
can be used by themselves or attached to a binder, such as phosphonic acid
chelating
agents (that have affinity for calcific tissue) or other binders such as solid
supports
like hydroxyapatite.
The systemic administration of chelating agents to scavenge radioactivity that
does leach to non-target areas of the body is another aspect of this
invention. The
compositions of this invention allow higher target to non-target ratios using
lower
total amounts of radioisotopes, thus increasing the possibility of delivering
significantly more radioactivity to the site of the target tissue without
dosing normal
tissue.
Detailed Description of the Invention
This invention involves the delivery of a therapeutic amount of a formulated
radioisotope composition directly to an undesired tissue mass, including
infections
(e.g., osteomyelitis) and cancerous tumors, especially inoperable cancerous
tumors, in
both soft tissue and bone. Because these formulations are very small in volume
and
the amount of radioactivity administered is effectively directed to the
desired site, the
administration is not by means that involve other body areas, e.g., no
systemic
administration (such as I.V. administration) is intended. Non-target, normal
tissue is
spared because only a very small amount of radioisotope is administered and
the
majority of the radioisotope mixture is immobilized at the administration
site. Thus
the majority of the radioactive decay of the isotope occurs at the site of
injection with
only small amounts of radioactivity leaching out of the injection site before
a
significant amount of the radioisotope decays. This results in a high
radiation dose to
the target area and extremely small doses to non-target tissues. The
composition can
be used to treat a variety of conditions, particularly cancerous tumors.
Radioisotopes used in this invention are particle emitters (beta ((3) emitters
or
alpha (a) emitters). Preferred radioisotopes are ions of rare earth-type
metals
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including Pm, Sin, Gd, Dy, Ho, Yb, Lu, and Y; especially preferred are Sm, Ho,
Lu,
and Y. Preferred radioactive isotopes include: Sm-153, Ho-166, Y-90, Pm-149,
Gd-
159, Lu-177, Yb-175, Pb-212, Bi-212, Bi-213, and Ac-225. Especially preferred
are
Sm-153, Ho-166, Y-90, Bi-213, Ac-225, and Lu-177. Most preferred are isotopes
with a relatively short half life of less than about 3 days and that emit
energetic beta
particles. Examples include Y-90, Ho-166, and Sm-153. It is understood that
often
the radioisotopes contain non-radioactive carrier isotopes as a mixtures.
In one aspect of this invention, the radioisotopes are administered in an
aqueous formulation without a chelating agent or other binder after the pH of
the
solution has been raised. A preferred pH of the formulation is wherein the
metallic
radioisotopes are in a hydroxide form which usually results in a suspension.
This pH
varies from metal to metal and is known to one skilled in the art. Preferred
pH
formulations include a pH greater than about 7. More preferred formulations
are a pH
greater than about 8. A pH range from about 8 to about 14 is desirable for
most of
these radioactive metals, and preferred is a range from about 8 to about 11.
The pH is
attained by the addition of a suitable base such as sodium hydroxide. While
not
wishing to be bound by theory, it is believed that the metallic radioisotopes
form
insoluble hydroxides that precipitate and remain in the tissue longer than if
the dose is
administered in neutral or acidic solution (pH less than about 7) or if the
radioisotope
is bound to a soluble binder such as a chelating agent. To facilitate the
precipitation it
is possible to add another non-radioactive metal such as iron that could co-
precipitate
with the radioisotope.
In another aspect of this invention, the radioisotope is bound to a phosphonic
acid chelating agent (that has an affinity for bone) or other binder such as
hydroxyapatite that helps retain it at the injection site. When a binder is
used then
greater than about 75% of the radioisotope remains at the site of
administration within
two half lives of radioactive decay.
The various radioisotopes discussed above are administered as a formulation
in a liquid that is pharmaceutically-acceptable, such as water, saline, or an
oil such as
sesame seed oil, corn oil and others. The formulated liquid may be a
suspension, a
slurry or an emulsion. Optionally other usual ingredients can be present such
as
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excipients, suspension aids, preservatives, base or buffers for pH adjustment,
and
others.
In yet another aspect of this invention, the amount of the radioisotope
administered is very low. Preferred volumes of administered radioisotope are
less
than about 50 microliters per cubic centimeter of tissue (50 gL/cm). More
preferred
are doses of less than 20 microliters per cubic centimeter of tissue (20
gL/cm).
Delivery of the dose can be done using a microsyringe or a pump capable of
accurately delivering microliter volumes (e.g. Valco Instrument Company, Inc.
model
CP-DSM) to provide flow to the proximal end of a catheter which may be placed
within or next to the tissue to be treated. The flow may be either continuous
or may
be pulsed to enhance complete penetration of the tissue mass by the
radioisotope.
In another aspect of this invention a chelating agent is administered
systemically to the patient before and for a time after the administration of
the
radioactive dose. Preferred chelating agents including EDTA and DTPA that
serve to
scavenge systemic radioactivity and remove it from the body via the kidneys
and into
the bladder. These agents are used when desired to ensure more complete
removal of
the administered radioisotope that may have migrated from the injection site.
As
usually only a low amount of such migration occurs, this treatment is
optional.
In one embodiment of the invention, the radioisotope may be delivered to a
bone tumor using a miniature pump. Access to the tumor may be effected by the
use
of a bone biopsy tool or a miniature drill capable of making a curved or
angled hole
through bone and either upstream of the tumor (so to guide the catheter
towards it) or
directly into the bone or tumor in the bone. The insertion of the catheter
using
fluoroscopy, as is known in the art, may help to position the distal end of
the catheter
in close proximity to the tumor. The delivery of the radioisotope upstream of
the
tumor may reduce the risk of spreading cancer cells potentiated by approaching
the
tumor directly or downstream from the blood flow.
The drill used in the present examples is discussed in US Provisional Patent
Applications 60/890,831 entitled, "Directional Bone Drilling and Methods of
Treatment" filed on February 20, 2007 and 60/891,183 entitled, "Directional
Bone
Drilling and Methods of Treatment" filed on February 22, 2007, but this
invention is
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not limited to the use of this drill as any device that can provide a suitable
hole in the
bone, such as a syringe needle or biopsy tool will suffice.
In another aspect of this invention the radioisotopes are combined with a
binder that is a solid support, such as hydroxyapatite. This form of calcium
phosphate
has the ability to bind metal ions such as radioactive rare earth metals. The
hydroxyapatite/metal ion combination can be administered into tissues and a
therapeutically significant amount of the radioisotope remains at the site of
injection.
In another aspect of the invention, the radioisotopes may have binder
molecules that have affinity for bone such as phosphonic acid chelating
agents.
Preferred chelating agents include those selected from
aminomethylenephosphonic
acids such as ethylenediaminetetramethylenephosphonic acid (EDTMP), diethylene-
triaminepentamethylenephosphonic acid (DTPMP), hydroxyethylethylenediamine-
trimethylenephosphonic acid (HEEDTMP), nitrilotrimethylenephosphonic acid
(NTMP), tris(2-aminoethyl)aminehexamethylenephosphonic acid (TTHMP), 1-
carboxyethylenediaminetetramethylenephosphonic acid (CEDTMP), bis(amino-
ethylpiperazine)tetramethylenephosphonic acid (AEPTMP), ethylenediaminetetra-
acetic acid (EDTA), 1,4,7,1 0-tetraazacyclododecane-N, N',N",N"'-
tetramethylene-
phosphonic acid (DOTMP), hydroxyethyldiphosphonic acid (HEDP), methylene-
diphosphonic acid (MDP), diethylenetriaminepentaacetic acid (DTPA),
hydroxyethyl-
ethylenediaminetriacetic acid (HEDTA), and nitrilotriacetic acid (NTA). More
preferably, the chelating agent is 1,4,7, 1 0-tetraazacyclododecane-N,
N',N",N"'-
tetramethylenephosphonic acid (DOTMP).
In one aspect of this invention, the bone seeking radiopharmaceutical complex
is chosen from the group consisting of Sm-153-EDTMP, Sm-153-DOTMP, Ho-166-
EDTMP, Ho-166-DOTMP, Gd-159-EDTMP, Gd-159-DOTMP, Dy-165-EDTMP,
Dy-165-DOTMP, Lu-177-EDTMP and Lu-177-DOTMP. Most preferred
radiopharmaceutical complexes for use with the present invention include Sm-
153-
DOTMP, Ho-166-DOTMP, Lu-177-DOTMP, and Gd-159-DOTMP. Examples of
these complexes and their preparation are described in U.S. Patents 4,976,950,
4,882,142, 5,059,412, 5,066,478, 5,064,633, 4,897,254, 4,898,724 and
5,300,279,
which are incorporated herein by reference.
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This invention will be further clarified by a consideration of the following
examples, which are intended to be purely exemplary of the present invention.
The
following numbered examples illustrate this invention; and the lettered
examples are
illustrating comparative examples.
Examples
General Information
All percentages are weight/weight (w/w) unless stated otherwise.
MURR is University of Missouri Research Reactor (Columbia, MO) that has a
service to provide radioisotopes.
It is understood that often the radioisotopes contain non-radioactive carrier
isotopes as a mixtures.
Example 1: High pH Lu-177 mixture
A high pH Lu-177 solution was prepared by adding of 2.0 gL of 50% w/w
NaOH to 10 L of a Lu- 177 solution (obtained from MURR, 1.09 Ci/mL in 0.05 M
HCI) followed by the addition of 8.0 L of water. The mixture was allowed to
stand
for 30 minutes prior to injection. The pH of the mixture was greater than
about 10.
Example A: Low pH Lu-177 solution (comparative)
A solution of Lu-177 in 0.05 M HCl was obtained from MURR containing
about 1.09 Ci/mL. The injectate was prepared by mixing equal volumes of the Lu-
177
solution and 0.05 M HCI. The pH was less than about 2.
Example 2: In vivo Xenograft Test - High pH Lu-177
An athymic mouse bearing an HT-29 xenograft was anesthetized and 2-3 L
of the mixture of Example 1 was diluted with about 20 L of water and
administered
directly into the tumor. Multiple injections were made at several. different
sites
around the periphery of the tumor as well as directly into the tumor mass. The
amount
of injected activity was determined to be 0.924 mCi Lu- 177. Gamma camera
images
13 days post-treatment showed the majority of the activity remaining at the
injection
site. Less than 1 pCi of the Lu-177 was found in the urine or feces on any of
the 13
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days post-injection. The size of the tumor was measured and compared to a
similar
mouse injected with saline as a control. The tumor in the saline control mouse
increased in size while the tumor in the mouse of this Example 2 decreased in
size.
These results are shown in the Table 1 below:
Table 1
Tumor size in cubic millimeters for treated and control mice
Days Post 1 2 3 6 7 8 9 10 11 12 13
Treatment
Mouse of 405 447 816 282 721 282 237 211 144 181 154
Example
2
Control
Mouse 527 1362 1332 1499 2673 2847 3621 3589 3357 3748 4573
Example B: In vivo Xenograft Test - Low pH Lu-177 (comparative)
An athymic mouse bearing an HT-29 (human colorectal carcinoma) xenograft
was anesthetized and 2-3 pL of the solution of Example A was administered
directly
into the tumor. The amount of injected activity was determined using a dose
calibrator to be 1.08 mCi of Lu- 177.
The fate of the Lu- 177 in the mouse body was determined using a gamma
camera. In addition, a dose calibrator was used to measure the amount of
radioactivity
collected in the urine as a function of time. After 1 day, 50 ICi of Lu-177
was found
in the collected urine and feces. In addition, significant migration of
radioisotope
from the tumor area was observed. Over time, the mouse showed signs of
increasing
morbidity. The mouse was euthanized due to morbidity after a 20% loss in body
weight 9 days post-injection.
Example 3: In vivo Prostate Test
A volume of about 6-8 pL of the solution of Example 1 was administered to
the left lobe of the prostate of a normal Sprague Dawley rat while the rat was
under
anesthesia. The rat received a Lu-177 dose of 0.924 mCi.
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The rat was monitored daily for Lu-177 in urine and feces. Only minimally
measurable Lu-177 (-1.0 .tCi) was found on any individual day. Gamma images
showed the Lu- 177 remaining at the injection site throughout the 7 day study
with
very little systemic radioactivity. The rat was euthanized seven days post-
treatment,
organs and tissues were excised and the presence of Lu-177 in each was
determined.
Less than 10% of the dose was found outside the prostate after 7 days.
Examination
of the prostate revealed the injected lobe of the prostate to be atrophied
compared to
the opposite lobe of the prostate.
Example 4: Lu-177 Injectate preparation
Lu-177 was received from MURR in 0.1 M HCl at 0.71 mCi/ L upon arrival.
Activity was measured using a CapintecTM CRC-15 dose calibrator. To 3.0 gL of
this
solution was added 3.0 gL of 1.0 N NaOH (Fisher). Water was added to give a
final
volume of 10.0 L.
Example 5: Lung Test - Lu- 177 Injection into a male Sprague Dawley Rat
A 364 g male Sprague Dawley rat, under anesthesia, was injected with 3-5 L
(-1.0 mCi) of the preparation in Example 4 directly into the lung using an
insulin
syringe. The dose was deposited in the left lobe of the lung via needle
insertion
through the skin.
Images of the rat using a gamma camera were taken at 30 minutes post
injection, 18 hours, 2, 5, 7 and 9 days post injection. Feces and urine
excretions were
collected daily and analyzed for the presence of radioactivity. At 9 days the
rat was
euthanized and organs/tissues obtained for gamma counting.
All gamma images showed one a single spot at the site of injection with no
detectable activity in any other part of the body.
Gamma counting of low activity tissues was accomplished using a WizardTM
1480 gamma counter (Packard); highest activity samples, which were the urine
and
lung, were evaluated on a CapintecTM CRC-15 dose calibrator.
Evaluation of the data indicate 76.2% of the injected Lu-177 remained in the
lung at 9 days post injection. About 15% was excreted in the feces/urine. The
rat
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skeleton (Bone) had 3.6%, and liver about 0.4%. Less than 1 % of the injected
radioactivity was found in any other organ or tissue.
Example 6: Ho-166 Administered to Bone as the Hydroxide
Holmium-166 (Ho-166) was obtained from MURR. The solution was 52.4
mCi in 350 L for a specific activity of 0.15 mCi/IL in 0.1 M HCI. The Ho-166
solution (10 L) was placed in a vial and 5 L of 0.1 M NaOH was added. The pH
was measured with pH paper showing a pH of about 10.
A miniature drill was used to create a hole in the femur of an anesthetized
Sprague Dawley rat. A miniature pump was used to deliver 3 L of this high pH
Ho-
166 solution into the hole created by the drill.
Two hours after the injection of the dose the rat was sacrificed and
dissected.
Tissues/organs excised and counted included bone (opposite femur), liver,
kidneys,
spleen, muscle, blood, heart, lung, pancreas as well as the injected femur.
Counting
was done by the use of a Nal gamma detector to determine the presence of
radioactivity.
The amount of activity found in the site of injection was 92 % of the injected
dose. Less than 2% of the dose was found in the liver or in the rest of the
bone. Total
skeletal dose was determined by multiplying the % dose in the opposite femur
by 25.
No urine activity was evident.
Example C (comparative): Ho-166 Administered to Bone as the Chloride
Ho-166 in O.1M HCl was obtained from MURR. The pH was measured with
pH paper showing a pH of about 1. The miniature drill described above in
Example 6
was used to create a hole in the femur of an anesthetized Sprague Dawley rat.
The
miniature pump described above was used to deliver 3 pL of Ho-166 solution
into the
hole created by the drill. Two hours after the injection of the dose the rat
was
sacrificed and dissected. The amount of activity found in the site of
injection was 5 %
of the injected dose. However 52% of the dose was found in the liver and 23%
of the
dose was found in the rest of the bone. Total skeletal dose was determined by
multiplying the % dose in the opposite femur by 25. The high amount of the
dose
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found in non-target areas shows that this form of Ho-166 is not an effective
way to
dose patients.
Example 7: Ho-166 Administered to Bone with Hydroxyapatite
Hydroxyapatite (6 mg) was placed in a vial and 600 L of water was added.
The mixture was shaken to form a slurry and 15 pL of the slurry were taken and
placed in a separate tube. To this was added 3 gL of Ho-166 in 0.1M HCI. The
miniature drill described in Example 6 was used to create a hole in the femur
of an
anesthetized Sprague Dawley rat. The miniature pump described in Example 6 was
used to deliver 3 pL of Ho- 166 labeled hydroxyapatite solution into the hole
created
by the drill. Three hours after the injection of the dose the rat was
sacrificed and
dissected. The amount of radioactivity found in or directly around the site of
injection
was 94% of the injected dose. Less than 1% of the dose was found in the liver
or in
the rest of the bone. Total skeletal dose was determined by multiplying the %
dose in
the opposite femur by 25.
Example 8: Sm-153-DOTMP
Sm-153 in 0.1 M HCI was obtained from MURR. The complex formed
between Sm-153 and DOTMP was prepared by combining 5 pL of Sm-153 with 5.6
L of a solution containing 13 mg/mL of DOTMP (previously adjusted to pH 7-8)
and
4 L of water. An additional 5 pL of DOTMP solution was added to obtain high
complex yields. The amount of Sin found as a complex was 99% by ion exchange
chromatography. DOTMP was prepared and purified by known synthetic techniques.
The chelant was greater than 99% pure.
The miniature drill described in Example 6 was used to create a hole in the
femur of an anesthetized Sprague Dawley rat. The miniature pump described in
Example 6 was used to deliver 2 pL of Sm-153-DOTMP solution into the hole
created
by the drill. Two hours after the injection of the dose the rat was sacrificed
and
dissected. The amount of activity found in the site of injection was 9 % of
the
injected dose. None of the radioactivity was found in the liver and about 20%
was
found in the rest of the bone. Total skeletal dose was determined by
multiplying the
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% dose in the opposite femur by 25. An average of 65% of the injected dose was
found in the urine.
Summary
The examples above are illustrative of the present invention. When
compositions of radioisotope solutions at high pH are administered in small
volume,
the vast majority of the isotope remains at the site of administration, even
13 days post
injection (e.g. Example 2), compared with a similar administration of
radioisotopes at
low pH where a significant portion of the radioactivity migrates away from the
site of
administration (e.g. Example B). When direct injections of isotopes are made
directly
into the bone, a significantly higher percentage of radioactivity can be
delivered to
bone compared to I.V. administration of a bone-seeking radiopharmaceutical
where
only about 0.1 % of the radioactivity is taken up by a bone tumor. This allows
a much
lower total amount of radioactivity injected to deliver a much greater
radiation dose to
the target tissue.
The use of the compositions of this invention show in some cases, greater than
90% of the radioactivity at the desired site with little to no activity in non-
target
organs or tissues. As stated above, in addition to practically eliminating the
dose to
non-target tissues and organs, much less radioisotope is needed. Finally,
since more
activity can be delivered to the tumor, resolution of the tumor is possible.
In
comparing the tumor growth rate in Example 2 to that of Example B, a
therapeutic
effect was clearly demonstrated.
Although the invention and processes have been described with reference to
these embodiments, those of ordinary skill in the art may, upon reading this
application, appreciate changes and modifications which may be made which do
not
depart from the scope and spirit of this invention as described above or
claimed
hereafter.
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