Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
WO 92/2032~ PCT/US92/0405g
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ENGINEERING THE LOCAL INFLAMM~TORY RESPONSE
AS A MEANS OF CONTROLLED RELEASE DRUG DELIVERY
Field of the Invention
This invention relates generally to drug delivery
systems and particularly to a product, consisting of a
drug and cellular regulator, which, when introduced
subcutaneously into a human or animal, affects the
local tissue response, thereby affecting the release
and absorption rate of the drug into general
circulation.
Backqround of the Invention
There is a need for a reliable, controlled release
drug delivery system in which a drug can-be delivered
to a subject over a prolonged period without repeated
administration. Clinical therapies often require that
a continuous dosage of a drug be administered, or that
multiple drugs be administered in sequence at regular
intervals in continuous dosages over extended periods
of time.
There is a long history of controlled release drug
delivery. Methods include long acting oral dosage
forms, bolus injections, transdermal patches and
sub-cutaneous implants.
Previous efforts to develop implantable drug
delivery systems hav~ used polymeric or nonpolymeric
materials. The polymeric systems consist either of
matrices of non-biodegradable polymers or matrices of
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biodegradable polymers. Such polymer-based systems
are combined with the drug to create either a matrix
erosion system, in which the drug is evenly
distributed in a polymer matrix and is released as the
polymer breaks down in biological fluid after
introduction into the subject, or a matrix diffusion
system in which the drug is released by diffusion
through the polymer matrix, or a matrix
diffusion/erosion system in which the drug is released
by diffusion through the polymer matrix, as well as by
erosion as the surface of the polymer breaks down.
Microspheres in aqueous or oil suspension, have also
been uæed in which the drug is coated with a
bioerodible polymer and injected subcutaneously. The
microspheres erode and release the drug according to
the size and number of microspheres. In addition,
systems utilizing hydrogels and polymeric`reservoirs
have been devised. The nonpolymeric systems include
compressing mixtures of the drug and an excipient intd
a pellet. Such nonpolymeric systems can also be made
of a totally fused pellet or a partially fused
pellet. In a totally fused pellet, a drug and an
excipient are melted and recrystallized to form a
crystalline matrix; in a partially fused pellet, a
mixture of a drug and an excipient having a lower
melting temperature than the drug is heated and cooled
such that only the excipient melts and
recrystallizes. Cholesterol matrix systems have also
been developed.
The systems suffer from various inherent problems
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including: foregoing general permeability to
macromolecules; swelling of macromolecules, resulting
in their being trapped in the erosion or diffusion
systems; highly water soluble macromolecules
exhibiting volatile dissolution kinetics in implants;
proteins aggregating under certain pH conditions,
turning into gel-like subætances and thereby impeding
release; large molecular weight molecules having
problems being taken up by transport cells; surface
erosion resulting in indefinite duration that may
present a prolonged period of sub-effective drug
release, and the requirement of removing the implant
at the end of the effective release period.
Many of these problems have been overcome by
relatively recent nonpolymer implant technology
relating to totally fused and partially fused
implants. See, for example, U.S. Patent~Nos.
4,~48,024 and 4,892,734 issued to Leonard, co-pending
application Serial ~o. 07/565,273, "Multiple Drug
Delivery System", filed August g, 1990 and co-pending
application Serial No. 07/163,328, "Partially Fused
Peptide Pellet", filed March 2, 1988, the entire
disclosures of which are incorporated herein by .
reference.
All of the foregoing approaches, however, suffer
from a failure to recognize and ta~e into account a
critical factor involved in implantable long term
delivery systems, that is, the effect on drug release
of the local tissue response to the implanted
systems. The recognition of this factor, as well as
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an approach to account for and take advantage of it,
forms the basis of the present invention.
SummarY of the Invention
The invention provides a product, including a
biologically active substance, at least one cellular
regulator, and optionally an excipient, and a method
whereby such product is introduced subcutaneously into -~
a human or animal.
The cellular regulator is capable of controlling,
by either stimulating or inhibiting, one or more of
the processes that are associated with the local -
inflammatory response resulting from the subcutaneous
implant, such as production of macrophages,
proliferation of fibrous tissue encapsulating the
implant, infiltration of the fibrous capsule by new
blood vessels and lymphatics, and transport of
lipophilic or hydrophilic molecules into or out of the
encapsulated implant. By specifically regulating
colony stimulation, angiogenesis, and tissue
generation in this way, the cellular regulator aids in
generating a "paraglandular" compartment surrounding
the subcutaneous implant, which is capable of active
and interactive processing, including the release of
the biologically active substance from the
"paraglandular" compartment. This invention thus
exploits the naturally occurring local inflammatory
response by artificially manipulating the presence,
concentration, and order of appearance, of one or more
cellular regulators, so as to affect the kinetics of
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release of the biologically active substance from the
encapsulated implant.
The biologically active substance preferably is a
drug. The cellular regulator preferably is a
cytokine. The optional excipient may be part of any
one of a variety of drug delivery systems, including
polymeric systems, non-polymeric systems,
microspheres, hydrogels, polymeric reservoirs or
cholesterol matrices, which serve as the e~bodiment
for the implant.
Brief Description of the Drawinqs
Fig. 1 is a cross-sectional view of a
"paraglandular" compartment after implanted drug
pellet was removed, as viewed by scanning electron
micros~opy (SEM);
Fig. 2 is a cross-sectional view of the
compartment lumen surrounding an implanted pellet, as
viewed by SEM;
Fig. 3 is a cross-sectional view of the
compartment wall showing blood vessels and relative
tissue densities, as viewed by SEM;
Fig. 4 is a cross-sectional view of ~wo blood
vessels of capillary size in the middle region of the
~apsule wall, as viewed by SEM;
Fig. 5 is another view of the sample depicted in
Fig. 4 with inta t erythrocytes inside blood vessels,
as viewed by SEM;
Fig. 6 is a thin section of a fibroblast with
collagen fibrils of normal periodicity, as viewed by
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transmission electron microscopy (TEM);
Fig. 7 is a thin section of fibrous wall, excised
at 6 months, showing a few lipid-engorged foam cells
among loose collagen fibrils, as viewed by TEM;
Fig. ~ is a thin section of fibrous wall, excised
at 13 months, showing significantly denser populations
of lipid-engorged foam cells and denser collagen
fibrils than are present in Fig. 7 at 6 months, as
viewed by TEM.
Detailed Description of the Invention
This invention pertains to a drug delivery system,
including a drug and a cellular regulator, which, when
introduced subcutaneously into a subject, affects the
local tissue response, and thereby results in
controlled release of the drug. `
When a foreign body is subcutaneouslySintroduced
into a human or animal, a naturally occurring local
inflammatory response occurs. This response is
characterized by the stimulation of macrophages,
proliferation of fibrous tissue encapsulating the
foreign bndy, and infiltration of the fibrous capsule
by new blood vessels and lymphatics. See, e.g., S.M.
Wahl et al., "Role of Growth Factors in Inflammation
and Repair," J. Cell. Biochem., 40:193-199 (19893; A.
Roberts et al., "Transforming growth factor type ~:
Rapid induction of fibrosis and angiogenesis in vivo
and stimulation of collagen formation in vitro," Proc.
Natl. Acad. Sci., U5A, 83:4167-4171 (1986).
The specific regulation of this inflammatory
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response is modulated by naturally occurring, locally
acting, cellular regulators, which affect colony
stimulation, angiogenesis, and tissue generation.
See, e.q., K. Arai et al., "Cytokines: Coordinators of
Immune and Inflammatory Responses," Annu. Rev.
Biochem., 59:783-836 (1990). The composite effect of
such interactions is to generate a ~'paraglandular"
compartment surrounding the foreign body, capable of
active and interactive processïng.
It has been discovered that this paraglandular
compartment is an important factor in determining the
release kinetics of implanted delivery systems. This
invention is designed to exploit the local
inflammatory response by artificially manipulating
both the presence and concentrations of various
cellular regulators to favorably influence the
controlled release of drug from an implanted delivery
system. By modulating the active processing and
equilibration of the various cell and tissue
populations, the invention is designed to affect drug
release and absorption from the foreign body implant.
This invention thus represents a new approach to drug
delivery systems.
The invention involves the implantation of a
biologically active substance which is to be delivered
to a human or an animal in a therapeutically effective
amount, and at least one cellular regulator which is
present in sufficient amount to affect the local
inflammatory response which will result from
implantation.
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A. The BioloqicallY Active Substance
The biologically active substance may be any
substance having biological activity, including
protein, polypeptide, polynucleotide, nucleoprotein,
polysaccharide, glycoprotein, lipoprotein, and
synthetic and biologically engineered analogues o
such molecules.
Preferably, the biologically active substance is a
drug. A drug is a substance used on or administered ~-
to humans or animals as an aid in diagnosis, treatment
or prevention of disease or other abnormal conditions, `:
for relief of pain or suffering, or to control, :~:
affect, maintain or improve a physiological or
pathological condition.
Classes of drugs which are intended to be included
within this invention include anti-AIDS substances,
anti-cancer substances, antibiotics, anti-viral
substances, enzyme inhibitors, neurotoxins, opioids,
hypnotics, tranqùilizers, anti-convulsants, muscle
relaxants and an~i-Parkinson substances, -
anti-spasmodics and muscle contractants,
anti-h~ertensives, analgesics, anti-pyretics and
anti-inflammatory agents, local anesthetics,
prostaglandins, anti-depressants, anti-psychotic
substances, anti-emetics, imaging agents, specific
targeting agents, neurotransmitters and proteins.
Anti-AIDS substances are substances used to treat
or prevent Autoimmune Deficiency Syndrome (AIDS).
Examples of such substances include CD4,
3'-azido-3'-deoxythymidine (AZT),
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9-(2-hydroxyethoxymethyl)-guanine acyclovir
(acyclovir), phosphonoformic acid, l-adamantanamine.
peptide T, and 2',3' dideoxycytidine.
Anti-cancer substances are substances used to
treat or prevent cancer. Examples of such substances
include methotrexate, cisplatin, prednisone.
hydroxyprogesterone caproate, medroxyprogesterone
acetate, megestrol acetate, diethylstilbestrol, ~-
ethinyl estradiol, tamoxifen, testosterone propionate,
1uoxymesterone, vinblastine (VLB), vincristine,
vindesine, etoposide, teniposide, dactinomycin
(actinomycin D), daunorubicin (daunomycin;
rubidomycin), doxorubicin, bieomycin, plicamycin
(mithramycin), mitomycin (mitomycin C), -asparaginase,
hydroxyurea, procarbazine (N-methylhydrazine, MIH),
mitotane, aminoglutethimide, mechlorethamine, `
cyclophosphamide, melphalan ( -sarcolysin~, uracil
mustard, chlorambucil, busulfan, carmustine (BCNU),
lomusline (CCNU), semustine (methyl-CCNU),
streptuzocin (steptozotocin), dacarbazine (DTTC:
dimethyltriazenomidazolecarboxamide), methotrexate
(amethopterin), fluorouracil (5-fluorouracil: 5-FU),
cytarabine (cytosine arabinoxide), mercaptopurine
(6-mercaptopurine: 6-MP), thioguanine
(6-thioguanine: TG).
Antibiotics are art recognized and are substances
which inhibit the growth of or kill microorganisms.
Antibiotics can be produced synthetically or by
microorganisms. Examples of antibiotics include
pennicillin, tetracycline, minocycline, doxycycline,
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vanomycin, bacitracin, kanamycin, nQomycin,
erythromicin and cephalosporins. Examples of
cephalosporins include cephalo~hin (keflin, seffin),
cephapirin (cefadyl), cefazolin (ancef, kefzol),
cephalexin (keflex), cephradine (anspor, velosef),
cefadroxil (duricef, ultracef), cefamandole (mandol),
cefoxitin (mefoxin), cefaclor (ceclor), cefuroxime
(zinacef), cefonicid (monocid), ceforanide (pr~cef),
cefotaxime (claforan), moxalactam (moxam), ceftizoxime
(cefizox), ceftriaxone (rocephin), and cefoperazone
(cefobid).
Anti-viral agents are substances capable of
destroying or suppressing the replication of viruses.
Examples of anti-viral agents include
~-methyl-Q-adamantane methylamine (ri mantadine),
l-~-D-ribofuranosyl-1,2,4-triazole-3 carboxamide
(ribavirin), 9-~2-hydroxy-ethoxy]methylguanine
(Acyclovir), adamantanamine, 5-iodo-2'-deoxyuridine
(Idoxuridine) and adenine arabinoside (Vidarabine). ' -
Enzyme inhibitors are substances which in~ibit an
enzymatic reaction. Examples of enzyme inhibitors
include edrophonium chloride,
~-methylphysostigmine,(-~-, neostigmine bromide,
physostigmine sulfate, tacrine HCL (THA),
tacrine,l-hydroxy maleate, iodotubercidin,
p-bromotetramisole,(-)-,
10-(a-diethylaminopropionyl)- phenothiazine
hydrochloride (As-1397), calmidazoli~m chloride,
hemicholinium-3, 3,5-dinitrocatechol (OR-486),
diacylglycerol kinase inhibitor I (R59022),
r. ~
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diacylglycerol kinase inhibitor II (R59949),
3-phenylpropargylamine, N6-monomethyl-L-arginine
acetate, carbidopa, 3-hydroxybenzylhydrazine HCl
(NSD-1015), hydralazine HCl (apresoline), clorgyline
HCl, deprenyl HCl,L~ , deprenyl HCl,D(+)-,
hydroxylamine HCl, iproniazid phosphate,
6-MeO-tetrahydro-9H-pyrido-indole, nialamide,
pargyline HCl, quinacrine HCl, æemicarbazide HCl,
tranylcypromine HCl, ;~
N,N-diethylaminoethyl-2,2-diphenyl~alerate
hydrochloride, 3-isobutyl-1-methylxanthne, papaverine
HCl, indomethacind, 2-cyclooctyl-2-hydroxyethylamine ~'
hydrochloride (CONH),
(+)-2,3-dichloro-a-methylbenzylamine
(DCMB),(LY-78335),
8,9-dichloro-2,3,4,5-tetrahydro-lH-2-
benzazepine hydrochloride, p-aminoglutethimide,(+)-,
p-aminoglutethimide tartrate,R(+)-,
p-aminoglutethimide tartrate,S(-)-, 3-iodo~yrosine,L-,
a-methyltyrosine,L-, ~-methyltyrosine,D ~-, and
allop~rinol.
Neurotoxins are substances which have a toxic
effect on the ner~ous system, e.g. nerve cells.
~eurotoxins include adrenergic neurotoxins,
cholinergic neurotoxins, dopaminergic neurotoxins, and
other neurotoxins. Examples of adrenergic neurotoxins
include N-(2-chloroethyl)-N-ethyl-~-bromobenzylamine
hydrochloride. Examples of cholinergic neurotoxins
include acetylethylcholine mustard hydrochloride
acetyl AF-64. Examples of dopaminergic neurotoxins
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include 6-hydroxydopamine HBr,
l-methyl-4-(2-methylphenyl)-1,2,3,6-
tetrahydro-pyridine hydrochloride,
l-methyl-4-phenyl-2,3- dihydropyridinium perchlorate,
N-methyl-4-phenyl-1,2,s,6- tetrahydropyridine HCl,
l-methyl-4-phenylpyridinium iodide. Other neurotoxins
include L-B-methyl-a,B-diaminopropionic acid
hydrochloride, (~ methyl-a,~-diaminopropionic
acid hydrochloride, L-~-oxalyl-a,~-diaminopropionic
acid, and quinolinic acid.
Opioids are substances having opiate like effects
that are not derived from QpiUm. Opioids include
opioid agonists and opioid antagonists. Opioid
agonists include codeine sulfate, fentanyl citrate,
hydrocodone bitartrate, loperamide HCl, morphine
sulfate, noscapine, norcodeine, normorphine,
thebaine. Opioid antagonists include
nor-binaltorphimine HCl, buprenorphine, ~-
B-chlornaltrexamine 2HCl, ~-funaltrexamione HCl,
nalbuphine HCl, nalorphine HCl, naloxone HCl,-
naloxonazine, naltrexone HCl, and naltrindole HCl~NTI).
Hypnotics are substances which produce a hypnotic
effect. Hypnotics include pentobarbital sodium,
phenobarbital, secobarbital, thiopental and mixtures,
thereof, heterocyclic hypnotics, dioxopiperidines,
glutarimides, diethyl isovaleramide,
a-bromoisovaleryl urea, urethanes and disulfanes.
Tranquilizers are substances which provide a
tranquilizing effect. Examples of tranquilizers
include chloropromazine, promazine, fluphenzaine, -
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reserpine, deserpidine, and meprobamate.
Anti-convulsants are substances which have an
effect of preventing, reducihg, or eliminating
convulsions. Examples of such agents include
primidone, phenytoin, valproate, Chk and ethosuximide.
Muscle relaxants and anti-Parkinson agents are
ag~nts which relax muscles or reduce or eliminate
symptoms associated with Parkinson`s disease.
Examples of such agents include mephenesin,
methocarbomal, cyclobenzaprine hydrochloride,
trihexylphenidyl hydrochloride, levodopa/carbidopa,
and biperiden.
Anti-spasmodics and muscle contractants are
substances capable of preventing or relieving muscle
spasms or contractions. Examples of such agents
include atropine, scopolamine, oxyphenonium, and
papaverine.
Anti-hypertensives are substances capable of
counteracting high blood pressure. Examples of such
substances include a-methyldapa and the -
pivaloyloxyethyl ester of a-methyldapa.
Analgesics are substances capable of preventing,
reducing, or relieving pain. Examples of analgesics
include morphine sulfate, codeine sulfate, meperidine,
and nalorphine.
Anti-pyretics are substances capable of relieving
or reducing fever and anti-in1ammatory agents are
substances capable of counteracting or suppressing
inflammation. Examples of such agents include aspirin
(salicylic acid), indomethacin, sodium indomethacin
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trihydrate, salicylamide, naproxen, colchicine,
fenoprofen, sulindac, diflunisal, diclofenac,
indoprofen and sodium salicylamide.
Local anes~hetics are substances which have an
anesthetic effec~ in a loralized region. Examples of
such anesthetics include procaine, lidocain,
tetracaine and dibucaine.
Prostaglandins are art recognized and are a class
of naturally occurring chemically related, long-chain
hydroxy fatty acids that have a variety of biological
effects. Examples of such agents include E2 and El.
Anti-depressants are substances capable of
preventing or relieving depression. Examples of
anti-depressants include imipramine, amitriptyline,
nortriptyline, protriptyline, desipramine, amoxapine,
doxepin, maprotiline, tranylcypromine, phenelzine, and
isocarboxazide.
Anti-psychotic substances are substances which
modify psychotic behavior. Examples of such agents
include phenothiazines, butyrophenones and
thioxanthenes.
Anti~emetics are substances which prevent or
alleviate nausea or vomiting. An example of such a
substance includes dramamine.
Imaging agents are agents capable of imaging a
desired site, e.g. tumor, in vivo. Examples of
imaging agents include substances having a label which
is detectable in vivo, e.g. antibodies attached to
fluorescent labels. The term antibody includes whole
an~ibodies or fragments thereof.
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Specific targeting agents include agents capable
of delivering a therapeutic agent to a desired site,
e.g. tumor, and providing a therapeutic effect.
Examples of targeting agents include agents which can
carry toxins or other agents which provide beneficial
effects. The targeting agent can be an antibody
linked to a toxin, e.g. ricin A or an antibody linked
to a drug.
Neurotransmitters are substances which are
released from a neuron on excitation and travel to
either inhibit or excite a target cell. Examples of
neurotransmitters include dopamine, serotonin,
y-aminobutyric acid, norepinephrine, histamine,
acetylcholine, and epinephrine.
The term protein is art-recognized and for
purposes of this invention also encompasses peptides.
The proteins or peptides may be any bioactive protein
or peptide, naturally occurring or synthetic.
Examples of proteins include antibodies, enzymes,
steroids, growth hormone and growth hormone-releasing
hormone, gonadotropin-releasing hormone, and its
agonist and antagonist analogues, somatostatin and its
analogues, gonadotropins such as luteinizing hormone
and follicle-stimulating hormone, peptide-T,
thyrocalcitonin, parathyroid hormone, glucagon,
vasopressin, oxytocin, angiotensin I and II,
bradykinin, kallidin, adrenocorticotropic hormone,
thyroid stimulating hormone, insulin, glucagon and the
numerous analogues and congeners of the foregoing
molecules.
.,
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The examples discussed above may be listed in the
salt or non-salt form but for purposes of this
invention both forms are intended to be encompassed.
Further, if a particular salt-form of a drug is
listed, other art recognized biologically acce~ted
salts can be used in place of the listed salt-~orm. -
Examples of acceptable salts include hydrochloride,
hydrobromide, sulfate, laurelate, palmatate,
phosphate, nitrate, borate, acetate, maleate,
tartratei oleate, salisilate, salts of metals, means
or organic cations, e.g. quarternary ammonium.
This invention is also intended to encompass
derivatives or equivalents of the above discussed
drugs. A derivative is a drug which is structurally
similar to the foregoing list of drugs and is capable
of achieving the same or substantially the same
function or activity. An e~uivalent is àn agent
capable of achieving the same or substantially the
same intended f~nction or activity.
The biologically active subs~ance is present in
sufficient amount to achieve a therapeutic effect for
at least three months of delivery. In certain
preferred embodiments the biologically acti~e
substance is present in sufficient amount to achieve a
therapeutic effect fox at least three mon~hs of
systemic delivery. A therapeutically effective dose
is that amount necessary to prevent, treat, or reduce
the sy~ptoms associated with the particular condition
or disease being treated.
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B. The Cellular Requlator
The cellular regulator is any substance that
affects the local tissue response, including but not
limited to a cytokine or an oncogene product
homologous to a cytokine, or any compound which may
inhibit or otherwise affect such regulators, su~h as a
steroidal or non-steroidal anti-inflammatory. See,
e.q., K. Arai et al., "Cytokines: Coordinators of
Immune and Inflammatory Responses," Annu. Rev.
Biochem., 59:783-836 (1990); F.R. Balkwill and F.
Burke,~"The cytokine network," ImmunoloqY TodaY,
16:29g-304, (September, 1989). Cytokines are involved
in controlling the proliferation and differentation of
mammalian cells and cellular interactions in the
immune and inflammatory responses.
By affecting the local tissue response, it is
meant that the cellular regulator is present in
sufficient amount to accelerate, decelerate, increase,
or decrease the local inflammatory response to the
implant~ Functionally, the cellular regulato~ is
present in sufficient amount to increase or decrease
the release of biologically active substance relative
to an implant with no cellular regulator. This effect
may result for example from the cellular regulator
stimulating or retarding macrophage production,
proliferation of fibrous tissue encapsulating the
implant, infiltration of the fibrous capsule by new
blood vessels and lymphatics, transport of lipophilic
molecules across the encapsulated implant, transport
of hydrophilic molecules across the encapsulated
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implant, or preventing or suppressing chemotaxis.
The cellular regulator is in addition to the
biologically active substance. The cellular regulator
is present in sufficient concentration to affect the
local tissue response, but is not present in :
sufficient concentration to achieve a therapeutic
effect for the particular condition or disease being
treated.
The cellular regulator preferably is an .`.
interleukin, interleukin inhibitor or interleukin
receptor, including interleukin 1 through interleukin :~
10; an interferon, including alpha, beta and g~mma; a
hematopoietic factor, including erythropoietin,
granulocyte colony stimulating factor, macrophage
colony stimulating factor and granulocyte-macrophage
colony stimulating factor; a tumor necrosis factor,
including alpha and beta; a transforming~growth factor
(beta), including beta-l, beta-2, beta-3, inhibin, and
activin; a chemotactic factor, including
neutrophil-activating protein, monocyte
chemoattractant protein, macrophage-inflammatory
protein, SIS (mall inducible secreted), platelet
factor, platelet basic protein, and melanoma growth
stimulating activity; a growth factor, including
epidermal growth factor, transforming growth factor
(alpha), fibroblast growth factor, platelet-derived
growth factor, platelet-derived endothelial cell
growth factor, insulin-like growth factor, nerve
growth factor and bone growth/cartilage-inducing
factor (alpha and beta); a steroidal or non-steroidal
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anti-inflammatory.
The invention embodies a system in which one or
more than one cellular regulators are introduced.
Various combinations of cellular regulators, as well
as various times of introduction of different celll~lar
regulators, can be devised to either stimulate or
inhibit various aspects of the local inflammatory
response, so as to finely tune the rate of release of
the biologically active substance and maximize the
therapeutic efficacy of the particular biologically
active substance involved in the patient's treatment.
C. DeliverY Method
The invention embodies delivering the biologically
active substance and the cellular regulator into the
subject by injection or implantation. If the
injection method is to be used, a phased effect on the
local inflammatory response can be achieved by varying
the timing and order of the injections. If the
implantation method is to be used, the biologically
active subs~ance and the cellular regulator may be
prssent in the same physical unit or in separate
physical units. More than one cellular regulator may
also be used, either in the same physical unit or in `
separate physical units. Varying the timing and order
of implantations of the physical units can be used to
achieve a phased effect on the local inflammatory
response. In addition, the biologically active
substance and cellular regulator may be introduced
alone or in combination with an excipient. ~:
;,
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The excipient may be part of a polymeric system
consisting of matrices of biodegradable or
non-biodeqradable polymers; a nonpolymeric system
consisting of compressed mixtures, totally fused
pellets or parti~lly fused pellets; microspheres;
hydrogels; polymeric reservoirs; or cholesterol
matrices. ~-
A polymeric system consists of matrices of
polymers combined with a biologically active `~
substance. Such systems include (i~ matrix erosion
systems, in which the biologically active substance is
evenly dist~ibuted in a polymer matrix and is released
as the polymer breaks down in biological fluid after
introduction into the subject, (ii) matrix diffusion
systems in which the biologically active substance is
released by diffusion through the polymer matrix, and `~
(iii) matrix diffusion/erosion systems in which the
biologically active substance is released by diffusion
through the polymer matrix, as well as by erosion as
the surface of the polymer breaks down. Biodegradable
polymers that have been used in such systems include
hydroxycarboxylic acids, especially lactic acid and
glycolic acid. Cholesterol and ethylene vinyl acetate
copolymers have also been used. See, for example,
U.S. Patent No. 4,591,496 issued to Cohen et al.,
which describes a polymeric system consisting of
mixing a drug and a polymer, e.g. ethylene-vinyl
acetate copolymer powders, below the glass transition
temperature of the polymer, and compressing the
mixture at a temperature above the transition point.
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Nonpolymeric systems can be fabricated by
compressing mixtures of the bi~logically active
substance and a nonactive biocompatible binder into a
pellet. The rate of release and the uniformity of
release depend both on the relative amounts of the
drug and binder and on the homogeneity of the mixture
prior to compression. Nonpolymeric systems also
include totally fused pellets in which the
biologically active substance is melted together wi~h
a nonpolymeric carrier and then recrystallized by
cooling, to form the fused pellet. See, for example,
U.S. Patent Nos. 4,748,024 and 4,892,734, issued to
Leonard. In addition, a partially fused pellet can be
fabricated by mixing a biologically active substance
and a nonpolymeric carrier having a lower melting `~
temperature than the biologically active substance,
and heating and then cooling the mixture, such that
only the carrier melts and recrystallizes, capturing
the unmelted drug. Such totally and partially fused
pellets are characterized by nondiffusional, -
erosion-based, drug release. See, for example,
co-pending applications Serial No. 07/565,273,
"Multiple Drug Delivery System," filed Augus~ 9, 1990
and Serial No. 07/163,328, "Partially Fused Peptide
Pellet," filed March 2, 1988.
Microspheres are systems in aqueous or oil
suspensions, in which the drug is coated with a
bioerodible polymer and injected subcutaneously. The
`microspheres erode and release the drug according to
the size and number of microspheres.
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A hydrogel is designed to release a biologically
active substance contained therein, when the
composition is placed in an aqueous environment. See,
for example, U.S. Patent No. 4,526,938 issued to
Churchill et al., which describes a composition
comprising a polypeptide and a copolymer, in which the
hydrophobic component is biodegradable and the
hydrophilic component may or may not be biodegradable,
and in which the composition is capable of absorbing
water to form a hydrogel when placed in water or an
aqueous physiological type environment, from which the
polypeptide is then released over an extended period
of time.
A polymeric reservoir is a tubular device
possessing interconnected porous walls. The
interconnected porous reservoir walls provide a
continuous path for the migrating biologically active
substance which then diffuses from the reservoir at a
rate governed by the tortuosity of ~he diffusion
path. See, for example, U.S. Patent ~o. 4,702,917
issued to Schindler, in which the polymeric reservoir
is fabricated from a polylactone, including
polycaprolactone or its copolymers, or
pol~valerolactone and its copolymers, containing an
additive, such as a polyether which is selectively
removed by treatment with an appropriate solvent to
form the interconnected pores therein.
A cholesterol matrix delivery system comprises a
cholesterol matrix permeable to passage by diffusion
of the biologically active agent contained therein.
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See, for example, U.S. Patent No. 4,452,775 issued to
Kent, in which the matrix consists of cholesterol
powder and cholesterol prills optionally in
combination with a binding agent and a lubricating
agent, and in which the biologically active substance
is dispersed throughout the matrix.
The entire disclosures of U.S. Patent Nos.
4,452,775, 4,702,917, 4,526,938, 4,591,496 are
expressly incorporated herein by reference.
The presence of a cellular regulator, as described
in this invention, is designed to overcome the various
drawbacks that each of these previously described
systems exhibit on their own. The stimulation or
inhibition of the local inflammatory response upon
introduction of a cellular regulator into these `
systems will result in an enhanced "paraglandular"
compartment and a means for controlled rèlease of the
drug.
The cellular regulator may be present as a core
within a pellet, or the cellular regulator may be
coated onto the surface of a pellet so as to have an
initial stimulatory effect on ~he local inflammatory
response, or the cellular regulator may be impregnated
throughout a pellet to provide a continuous effect on
the local inflammatory response, or the cellular
regulator may be layered in a pellet to provide a
time-variant effect on the local inflammatory
response.
While the inventor does not wish to be bound by
any theory of the invention, it is believed that
W092/20325 PCT/US92/~059
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chemotaxis of foam cells (engorged lipophages) from
the foreign implant, through the fibrous tissue, and
toward the vasculature and Iymphatics, occurs. Since
the implant appears to remain coated with macrophages
throughout, it is further hypothesized that a dynamic
equilibrium or flux rate of new macrophages and
migrating lipophages exists and is regulated.
Analysis of the local tissue response to a
bioerodible s~bcutaneous drug implant has been carried
out using scanning electron microscopy (SEM) and
transmission electron microscopy (TEM~. These studies
support the conclusion that an integral microanatomy
devoted to the active processing of a drug implant
exists. In these studies, norethindrone (NET)
pellets, ANNUELLE'~ (Endocon, Inc. Walpole, MA),
composed of NET and cholesterol (85:15% respectively),
were implanted into human volunteers and subsequently
removed at various time points between 3 and 10.5
months post-implantation.
Figure 1 is an SEM of a cross-sectional view of a
"paraglandular" compartment 10, excised after 7 months
of implantation of a drug pellet in a subject, with
the implanted drug pellet removed. The wall 12, lumen
14, and bed 16 of the compartment 10 are apparent.
Capillary openings 18 are present at the bed 16.
Connective tissue 20 is loose at the periphery of the
compartment 10, and much denser towards the bed 16.
Figure 2 is an SEM of a cross-sectional view of the
compartment lumen 14, excised after 7 months,
surrounding an implanted drug pellet 22. Figure 3 is
W092/20325 PCT/US92/W059
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an SEM of the compartment wall 12, excised after 13.5
months, showing blood vessels 24 and relative
connective tissue densities. Looser connective tissue
20 is present at the outer compartment wall 12.
Figure 4 is an SEM of two blood vessels 24 of
capillary size, excised after 13 months, in the middle
region of the capsule wall 12. Connective tissue 20
surrounds the blood vessels 24. Figure 5 is an SEM of
another view of the sample depicted in Fig. 4, showing
intact erythrocytes 26 inside blood vessels 24.
Connective tissue 20 surrounds the blood vessels 24.
Figure 6 is a T~M of a thin section of a fibroblast -
28, excised after 3 months, with collagen fibrils 30
of normal periodicity in the fibrous portion of the
compartment. Figure 7 is a TEM of a thin section of
fibrous wall 32, excised after 6 months, showing a few `
lipid engorged foam cells 34, i.e., lipid-laden
macrophages, among loose collagen fibrils 30. Figure
8 is a T~M of a thin section of fibrous wall 32,
excised after 13 months, showing significantl~ denser
populations of lipid engorged foam cells 34 and denser
collagen fibrils 30 than are present in ~ig. 7 after 6
months of drug pellet implantation. A comparison of
Figures 7 and 8 supports the theory that the
concentration of foam cells increases with time
post-implantation of the drug pellet. The above
pictures are consistent with the foam cells either
entering the blood and lymphatic vessels, or extruding
the lipid at the vessel surface.
' '
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Mass spectrometric data supports the theory that
the foam cells absor~ the NET as it is released from
the pellet surface. In the same studies in which the
micrographs were taken, NET levels in the capsule
tissue at 3 to 10.5 months post-implantation, were,
respectively, 0.05~ and 8.4%. Such an increas~-
correlates qualitatively with the increase in foam
cell population in the capsule wall for the same
period.
The above data suggests that the local
inflammatory response plays an essential role in the
active processing of drug delivery systems. This
invention utilizes the theory that the implant, in
înducing a local inflammatory response, results in the
recruitment of macrophages and the concomitant release
of various cytokines. The implant becomes coated with
macrophages, and absorption of the drug from the
implant becomes, inter alia, a function of foam cell
transport to the local vasculature and lymphatics.
Some of the cytokines stimulate fibroblast production
and the establishment of angiogenesis for the
capsule. The resultant serum concentrations of
released drug are a function of this active processing -
of the drug implant. Thus, by regulating the rate and
extent of this active processing, by manipulating the
various elements that contribute to this processing,
one can regulate the rate and extent of drug release
from the implant.
One preferred embodiment would be the use of a
jacketed implant which is the subject of the
W092/2032S PCT/US92/~059
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co-pending application Serial No. 07/565,273,
"Multiple Drug Delivery System" (the disclosure of `
which is incorporated herein by reference). In this
embodiment, an angiogenesis factor would be combined
in matrix with a bio-erodible polymer, such as poly-dl
lactide or glycolide, as a sheath around a core drug
implant. The sheath would be formed so as to
gradually erode, releasing the angiogenesis factor,
and thus preparing the tissue environment for delivery ~
of the core drug. `
Example 1
One important compound of recombinant origin is
growth hormone of either human or bovine species
(hGH:bGH)
It is desirable to provide sustained release of a
few hundred micrograms of GH per day in vivo. Such
sustained release has not been achieved, because the
protein is not well absorbed and is rapidly degraded
in the subcutaneous environment by proteases ~r tumor
necrosis factor (TNF), both directly or indirectly, as
a result of macrophage stimula~ion in situ. Due to
this effect, much more compound than is clinically
required (one or more milligramsJday) is currently
attempted for reléase from compressed implants for
less than 30 days.
While the macrophage is directly or indirectly the
source of the hostile factors mentioned above, it is
also directly or indirectly the source of the growth
factors which are associated with sufficient
W092/20325 PCT/US92/04~59
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neovascular development (angiogenesis) necessary to
optimize the absorption of the active protein.
It would, therefore, be desirable to suppress the
macrophage function while supplying sufficient growth
factor necessary for angiogenesis by releasing GH into
the subcutaneous environment. Because GH is
~onlipophilic, it suffers additional difficulties
relati~e to absorption in the lipid environment~
Utilizing the methods of partial melting
elaborated in a co-pending application, matrices of
protein and lipophilic compounds such as steroids can
be acheived by seiecting combinations of excipients
and active ingredients that allow the melting and
recrystallization of the excipient only. This does
not preclude the material which undergoes a phase
change from also being an active ingredient.
A method of obtaining the desired results
described above is as follows:
1. 30 milligrams of bGH is intimately mixed
together with 0.3 milligrams of corticosterone or
similar crystalline, steroidal anti-inflammatory
compo~nd. This mixture is then packed into an
enclosed form and heated to the melting point of
the corticoid (145 degrees C.) and allowed to
cool. The resulting aggregate is then ground into
fine grains of approximately 100 microns @.
2. The granular powder of number one is
introduced into an intimate mixture of S
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milligrams of cholesterol palmitate and 0.7
milligrams of epidermal growth factor,
transforming growth factor beta or more specific
angiogenic cytokine.
3. The resulting mixture is packed into a Teflon
tube and partially fused into a rod-shaped implant
according to the methods described in U.S. Patent
Application Ser. No. 07/163,328 (filed March 2,
1988 and entitled "Partially Fused Peptide
Pellet," the disclosure of which is incorporated
herein by reference), by heating to the melting
point of the cholesterol palmitate (79 degrees
C.), which is below the melting points of all
other components of the mixture.
4. The rod is allowed to cool and rècrystallize
at room temperature.
5. The resulting pellet is implanted into the
subcut~neous tissue of a cow by means of a Harman
Injector; U.S. Patent No. 4,820,267.
The corticoid is soluble within the cholesterol
palmitate matrix and thus diffuses from the rod
carrying the GH with the result of both suppressing
the local inflammatory response (thus macrophage) and
providing a lipid buffer for the protein. As the
corticoid leaches from the rod, surface erosion of the
cholesterol palmitate will release angiogenic
W092~2032~ PCT/US92/04059
2i~3~4~ - 30 -
factor -- representing about 8% of the
non-GH/corticoid component of~the matrix, thus
stimulating neovascularization at the local implant
site.
Those skilled in the art will recognize or will be
able to ascertain with no more than routine
experimentation numerous equivalents to the specific
products and processes described herein. Such
equivalents are considered to be within the scope of
the invention and are intended to be covered by the
following claims in which I claim: `
