The invention pertains to the field of treatment of proliferative diseases and especially the treatment of vascular diseases such as, for example, arteriosclerosis.
It is known that ionizing radiation inhibits the proliferation of cells. A considerable number of neoplastic and non-neoplastic diseases have already been treated in this way (Fletcher, Textbook of Radiotherapy, Philadelphia, Pa.: Lea and Febiger, 1980, Hall, Radiobiology for the Radiologist, Philadelphia, Pa.: Lippincott, 1988).
An attempt has also already been made to treat arteriosclerotic diseases using this process. Arteriosclerosis is an inflammatory, fibroproliferative disease that is responsible for 50% of all deaths in the USA, Europe, and Japan (Ross 1993, Nature 362: 801-809). In its peripheral manifestation, it threatens the upkeep of the extremities; with its coronary manifestation, the risk of fatal myocardial infarction exists; and with supra-aortic infection, there is the threat of stroke.
At this time, arteriosclerosis is treated in various ways. In addition to conservative measures (e.g., lowering the cholesterol level in the blood) and the bypass operation, mechanical dilatation (angioplasty), as well as the intravascular removal of atheromatous tissue (atherectomy) of stenotic segments in peripheral arteries and the coronaries have been established as alternatives in regular clinical practice.
As stated below, the above-mentioned methods are associated with a considerable number of drawbacks, however.
The value of mechanical recanalization processes is greatly diminished by vascular occlusions as a result of vascular tears and dissections, as well as acute thromboses (Sigwart et al. 1987, N. Engl. J. Med. 316: 701-706). Long-term success is jeopardized by the reoccurrence of constrictions (restenosis). The CAVEAT study thus revealed that of 1012 patients, the restenosis rate six months after intervention in coronary atherectomy was 50% and in coronary angioplasty even 57% (Topol et al. 1993, N. Engl. J. Med. 329: 221-227). In addition, abrupt vascular occlusion occurred in this study in 7% of the atherectomy patients and in 3% of the angioplasty patients. Nicolini and Pepine (1992, Endovascular Surgery 72: 919-940) report a restenosis rate of between 35 and 40% and an acute occlusion rate of 4% after angioplastic intervention.
To combat these complications, various techniques have been developed. These include the implantation of metal endoprostheses (stents), (Sigwart et al. 1987, N. Engl. J. Med. 316: 701-706; Strecker et al., 1990, Radiology 175: 97-102). The implantation of stents in large-caliber arteries, e.g., in occlusions in the axis in the pelvis, has already become a treatment modality that is to be applied primarily. The use of stents in femoral arteries has shown disappointing results, however, with a primary openness rate of 49% and a reocclusion frequency of 43% (Sapoval et al., 1992, Radiology 184: 833-839). Similar unsatisfactory results have been achieved with currently available stents in coronary arteries (Kavas et al. 1992, J. Am. Coll. Cardiol. 20: 467-474).
Up until now, no pharmacological or mechanical interventions have been able to prevent restenosis (Muller et al. 1992, J. Am. Coll. Cardiol. 19: 418-432, Popma et al. 1991, Circulation 84: 14226-1436).
The reason for the restenoses frequently occurring after mechanical intervention is assumed to be that interventions induce a proliferation and migration of unstriped muscle cells in the vascular wall. The latter result in a neointimal hyperplasia and the observed restenoses in the treated vessel sections (Cascells 1992, Circulation 86, 723-729, Hanke et al. 1990, Circ. Res. 67, 651-659, Ross 1986, Nature 362, 801-809, Ross 1993, Nature 362, 801-809).
An alternative process for treating arteriosclerotic diseases uses ionizing radiation. The use of ionizing radiation of external origin on restenosis is associated with the drawback, however, that upon administration the radiation dose is not limited just to the desired spot; rather, the surrounding (healthy) tissue is also undesirably exposed to the radiation. Thus, to date, various studies have come up with little to increase the chances of success (Gellmann et al. 1991, Circulation 84 Suppl. II: 46A-59A, Schwartz et al. 1992, J. Am. Coll. Cardiol. 19: 1106-1113).
These drawbacks, which occur when external radiation sources are used, can be overcome if gamma radiation is directly used with restenosis via, e.g., a catheter in the vascular area. With this form of administration with iridium-192, a high radiation dose of 20 Gy is applied to the restenosis foci. Some works report on the almost complete prevention of restenosis after this intervention (Wiedermann et al. 1994, Am. J. Physiol. 267: H125-H132, Böttcher et al. 1994, Int. J. Radiation Oncology Biol. Phys. 29: 183-186, Wiedermann et al. 1994 , J. Am. Coll. Cardiol. 23: 1491-1498, Liermann et al. 1994, Cardiovasc. Intervent. Radiol. 17: 12-16). A drawback to this method is, however, that the radiation dose of 20 Gy that is applied in this case is very high. Since the lesions are dispersed irregularly on the vascular wall, uniform administration of a defined dose is not possible using this technique. Moreover, treatment of large-caliber vessels is not possible since, because of the dose reduction from the iridium source, the dose that can be administered is not adequate.
Another possible way of inhibiting restenosis is the implantation of P-32-doped stents (Fischell et al. Stents III, Entwicklung, Indikationen und Zukunft, Konstanz [Development, Indications, and the Future: Constancy]: Kollath and Liermann, 1995). In this work, an activity of 0.2 kBq P-32 per centimeter of stent length was enough (corresponding to a radiation dose of 0.25 Gy) to achieve maximum inhibition of unstriped vascular muscle cells in vitro. It was thus possible to show that not only γ-emitters but also β-emitters prevent the proliferation of unstriped muscle cells. An advantage of this Method is that the radiation dose administered is considerably lower than in all previously mentioned interventions. At this low dose, the endothelial cells that line the vascular bed are not damaged (Fischell et al. Stents III, Entwicklung, Indikationen und Zukunft, Konstanz: Kollath and Liermann, 1995). This form of intervention can be used only once, however, namely when the stent is positioned. In addition, it is limited only to those interventions in which stents are used. The restenoses that occur in the far more common types of interventions, such as atherectomies and angioplasties, cannot be treated with this method. Because of the small range of action of the β-radiation, it is not possible to administer a uniform dose of energy to the entire lesion.
In addition to radiation therapy, a number of other therapeutic strategies are used for inhibiting neointimal hyperplasias (restenoses). The latter comprise standard medicines for suppression of restenoses such as antithrombotic agents, platelet aggregation inhibitors, calcium antagonists, anti-inflammatory and antiproliferative substances, but also gene-therapy approaches. In this case, the inhibition of growth stimulators, e.g., by antisense oligonucleotides or the enhancement of inhibiting factors by expression-vector-plasmids and the virus-mediated gene integration, is possible. Also, Aptamer oligonucleotides can be used for inhibiting a wide variety of receptor-mediated processes, which play a decisive role in restenosis.
With great energy and care, substances have been studied over the years that were administered under strictly controlled conditions as a long-term treatment since the desired purpose was theoretically to reduce the restenosis rate (Herrmann et al., 1993, Drugs 46: 18-52).
More than 50 controlled studies with different substance groups were performed, without yielding definite proof that the substances examined could seriously reduce the restenosis rate.
This also applies for topical administration, in which the substances are brought via a special balloon catheter to the site of action that is desired in each case. It has been shown, however, that the previously used substances are washed too quickly from the vascular wall to be able to be therapeutically effective. Moreover, additional vascular wall alterations, which even act to promote restenosis, are induced by these pressure-mediated liquid injections.
The object of this invention was therefore to develop a process for the treatment of proliferative diseases that overcomes the drawbacks of previously known treatment processes.
This object is achieved by this invention.
A process for therapeutic treatment of proliferative diseases was developed that is characterized in that first an administration catheter is placed at the site of the lesion, a radioactive substance is topically administered via the catheter, then the catheter is removed, and the radioactive substance remains at the site of the lesion.
Since radioactive substances are transported via an administration catheter right to the wall of a blood vessel and remain there, the concentration of the radionuclide lasts long enough to inhibit the proliferation of the cells and thus a restenosis.
The process according to the invention has some important advantages over known treatment processes. In comparison to a considerable number of studied compounds from a wide variety of classes, the topical administration of certain substances and with certain catheters results in a surprisingly high radioactive dose at the desired, pathologically altered spot. This procedure results in a highly effective radiation dose with a low systemic load. The radioactive substances have a long dwell time at the administration site, which results in a highly effective dose on the spot. They are dispersed in particular and uniformly in the pathological regions. The unbonded radioactive substances are quickly eliminated.
Since certain radioactive substances, which are described in more detail below, pass into the wall of the arteriosclerotically altered vessels, not only the cells of the intima that face the lumen, but also those of the media and adventitia are kept from proliferating. The portion of the administered dose that passes through the cell membrane results in a high radiation dose, which is effective close to the cell core.
Owing to the sensitivity of proliferating cells to ionizing radiation, the process according to the invention is suitable not only for treatment of arteriosclerotic diseases, but also for the treatment of other proliferative diseases, such as, e.g., tumor diseases.
Suitable radioactive substances are those that have sufficiently high lipophilia to remain adhered to the plaque. For example, radiolabeled metal complexes are suitable, such as, e.g., metal complexes of bis-amine-oxime derivatives of general formula I
in which n=0-3, and radicals R1 to R8 are the same or different and in each case stand for a hydrogen atom and/or for an unbranched, branched, cyclic or polycyclic C1-C100 alkyl, C1-C100 alkenyl, C1-C100 alkinyl, C1-C100 aryl, C1-C100 alkylaryl and/or C1-C100 arylalkyl radical, which optionally is substituted with fluorine, chlorine, bromine and/or iodine atoms, and/or hydroxy, oxo, carboxy, aminocarbonyl, alkoxycarbonyl, amino, aldehyde or alkoxy groups with up to 30 carbon atoms and/or optionally is interrupted and/or substituted by one or more heteroatoms from the series N, P, As, O, S, Se, and whereby radicals R2 and R3, R4 and R5 as well as R6 and R7 together optionally can stand for an oxygen atom. These compounds, together with a radionuclide, form a metal complex, which is then used for topical administration in the treatment of proliferative diseases.
Also suitable are the metal complexes of the N2
derivatives of general formulas II and III
whereby R9 to R32 are the same or different and in each case stand for a hydrogen atom or for an unbranched, branched, cyclic or polycyclic C1-C100 alkyl, C1-C100 alkenyl, C1-C100 alkinyl, C1-C100 aryl, C1-C100 alkylaryl and/or C1-C100 arylalkyl radical, which is optionally substituted with fluorine, chlorine, bromine, and/or iodine atoms and/or hydroxy, oxo, carboxy, aminocarbonyl, alkoxycarbonyl, amino, aldehyde, or alkoxy groups with up to 30 carbon atoms, and/or optionally is interrupted and/or substituted by one or more heteroatoms from the series N, P, As, O, S, Se, and whereby radicals R11 and R12, R13 and R14, R15 and R16, as well as R17 and R18 together optionally can stand for an oxygen atom, and n, m and p, independently of one another, mean 1 or 2.
Other suitable compounds, which are suitable for topical treatment after complexing with suitable radioisotopes, are tetrofosmin, sestamibi and furifosmin derivatives. 99mTc-tetrofosmin can be obtained under the trade name Myoview™ from the Amersham Company; 99m Tc-sestamibi is marketed under the trade name Cardiolite® by the DuPont Company; and 99mTc-furifosmin can be purchased under the trade name TechneScan Q-12 from the Mallinckrodt Medical Company.
Together with a radionuclide, all these compounds form a metal complex that can then be used for topical administration in the treatment of proliferative diseases.
To form a metal complex, radionuclides can be introduced that are alpha-, beta- and/or gamma-radiators, positron-radiators, Auger electron-radiators, and fluorescence radiators, whereby β- as well as combined β/γ-radiators are preferred for therapeutic purposes.
Corresponding radionuclides are known to one skilled in the art. By way of example, the radionuclides of the elements of atomic numbers 27, 29-32, 37-39, 42-51, 62, 64, 70, 75, 77, 82, or 83 can be mentioned.
Preferred are the nuclides 99mTc, 186Re, 188Re, 67Cu, 90Y and 107Ag; especially preferred are nuclides 186Re, 188Re and 67Cu.
The production of bis-amine-oxime derivatives is described in U.S. Pat. Nos. 5,506,345 and 5,387,692; the production of N2S2 derivatives is described in U.S. Pat. No. 5,279,811.
The production of tetrofosmin derivatives is described in European Patent Application EP 303 374; the production of furifosmin derivatives is described in U.S. Pat. No. 5,112,595. Sestamibi derivatives and their production are described in International Patent Application WO 89/02433.
Other suitable metal complexes have ligands that are derived from ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), or a macrocyclic compound, such as, e.g., tetraazacyclododecane. The production of these compounds is known to one skilled in the art and is, moreover, described in detail in the examples below.
Other suitable ligands are, e.g., porphyrin derivatives, as they are described in, e.g., DE 42 32 925 A1 and DE 43 05 523 A1. Metal complexes that are suitable for the process according to the invention can also be produced with radionuclides from these ligands.
Also suitable are radioactive thallium compounds of isotopes 201Tl, 207Tl, 209Tl, and 210Tl; especially suitable is 201TlCl.
Radiolabeled colloidal solutions are also extremely well suited for the treatment of proliferative diseases and especially for topical administration.
Suitable colloidal solutions are the tin colloids that are described in the examples; especially suitable are the tin colloids that can be produced with the aid of a kit from the Amersham Company (“Amerscan Zinnkolloid (99mTc)—Markierungskit für die Leberszintigraphie [Amerscan Tin Colloid (99mTc)—Labeling Kit for Liver Scintigraphy]).” Other suitable colloids are, e.g., radioactive gold sol (198Au colloid) and radiolabeled sulfur colloids as well as other physiologically compatible, radioactive colloidal solutions.
Suitable radionuclides for radioactive labeling of colloidal solutions are known to one skilled in the art. By way of example, the radionuclides of elements Ag, As, At, Au, Ba, Bi, Br, C, Co, Cr, Cu, F, Fe, Ga, Gd, Hg, Ho, I, In, Ir, Lu, Mn, N, O, P, Pb, Pd, Pm, Re, Rh, Ru, Sb, Sc, Se, Sm, Sn, Tb, Tc, or Y can be mentioned.
Preferred are the nuclides 99mTc, 186Re, 188Re, 67Cu, 90Y, 153Sm, 160Tb, 162Tb, 198Au, and 107Ag.
The production of the colloidal solutions is generally done with a redox reaction or the alteration of pH in an aqueous or alcoholic solution in the presence of a radioactive salt. The colloid can be formed in the presence of a stabilizer or subsequently mixed with a surfactant or another stabilizing amphiphilic substance. Other production methods for suitable colloidal solutions are electrochemical methods, such as are described by, e.g., M. T. Reetz et al. in Angew. Chem. [Applied Chemistry] 1995, Vol. 107, p. 2461 ff. The production of the tin colloids is described in the examples below, as well as in the instructions of the labeling kit of the Amersham Company. The production of a gold colloid for diagnostic purposes is described in Patent DE 24 20 531 C3.
The size of the particles formed is in the range between 5 and 1000 nm, and in the case of the tin colloid it is between 300 and 600 nm.
As catheters that are suitable for topical administration of the substances according to the invention, the catheters that are sketched in FIG. 3 can be used. Especially suitable are multichamber balloon catheters (such as, e.g., Dispatch™, SciMed) and microperforated balloon catheters.
In the examples below, the process in the animal experiment is described. In addition, the production of some compounds that are suitable for use in this treatment process is described. In Examples 1 to 5, the process is implemented with 99m
Tc-labeled HMPAO, whereby the ligand HMPAO has the following structure:
(see also Radiopharmaceuticals, Chemistry and Pharmacology, edited by Adrian D. Nunn, 1992, page 53).