RADIOACTIVE THERAPEUTIC LIPOSOMES

Description

[0001] The present invention relates to a conjugator system comprising liposornes with ionophores and with chelator located inside of the liposomes, wherein the liposomes are stably labeled with heavy radionuclides emitting α particles. The present invention further relates to a method to prepare the conjugator system, as well as a kit for preparing the conjugator system.

[0002] Biomedical applications of radionuclides in anticancer therapy have so far focused on the use of cationic or anionic species, e.g., [¹³¹I]iodide against thyroid cancer and ⁸⁹Sr for palliation of pain from skeletal cancer metastases, and the use of mostly beta-emitting radionuclides attached to monoclonal antibodies (DeVita et al., 1996).

[0003] The use of targeted radionuclide therapy against cancer rest upon the ability to find ways to attach radionuclides to tumor specific carrier compounds (Gaze, 1996). Today, some of the radionuclides with useful radiation characteristics cannot be used in tumor targeting because of the problem of providing a chemically stable link between the radionuclide and the carrier compound. New carrier systems may, however, broaden both the use of radioisotopes, as well as the arsenal of radionuclides considered useful for therapy (Gaze, 1996).

[0004] Liposomes, with or without receptor affinic groups attached to the surface, have been evaluated for drug delivery, and is currently used clinically for the delivery of chemotherapeutics in some cancer forms. Recently, developments in liposome research have led to new versions with a pharmacokinetics which could make these compounds useful as carriers for radionuclide for internal radiotherapy against cancer (Gabizon, 1995). These recent developments in the formulation and manufacturing of liposomes have resulted in small vesicles of less than 100 nm with prolonged circulation time, as the size of the liposomes can be better confined to small diameters by using extrusion through membranes. Furthermore, the introduction of poly ethylene glycol (PEG) grafted liposomes has reduced the interference from plasma proteins, and thus reduced the recognition and clearance affected by the macrophages of the reticuloendothelial system (Maruyama, et al., 1997). Increased levels of tumor uptake due to sustained blood concentration have thereby been achieved. Even further tumor uptake has been achieved by conjugating molecules with receptor affinity, e.g., monoclonal antibodies or folate, to the surface of the liposomes. In addition, several studies have indicated the advantage of applying PEG as a linker between the lipsome and the targeting ligand, since this also can improve the receptor accessibility (e.g. Maruyama et al, 1997: Gabison et al, 1999: Lee et al, 1994).

[0005] Liposomes have previously been studied as carriers for radioisotopes (Goins et al, 1998; Turner et al, 1988). Pikul, et al (1987) reported a study based on ²¹²Pb-dextran incorporated passively (i.e.. the ²¹²Pb-dextran was added during the generation of the liposome, and a fraction of the ²¹² Pb-dextran was incorporated together with the aqueous phase representing the interior of the liposome). The authors did not suggest that these liposomes were suitable for cancer therapy, but was using it primarily for studying intracellular cell killing in vitro with radioisotope. No data of the fate of ²¹²Bi generated from the ²¹²Pb decay was presented, and the size of the liposomes were in the order of 350-500 nm which is very large compared to the size (approx.100 nm) currently considered optimal for in vivo tumor therapy (Forssen, 1997). Also, the liposomes did not contain PEG in the membrane.

[0006] Ogihar-Umeda et al. (1996) used liposomes as carrier for the gamma emitting radionuclides ⁶⁷Ga, ¹¹¹In and ^99mTc, and suggested the use of radiolabeled liposomes for imaging.

[0007] In a theoretical study, Kostarelos et al. (1999) suggested the use of liposomes labeled with the potentially therapeutically radionucides ¹³¹I, ⁶⁷Cu, ¹⁸⁸Re and ²¹¹At, but chemical procedures for the preparation of the radiolabeled liposomes were not suggested.

[0008] EP386 146 B1 describes a composition and method of use for liposome encapsulated compounds for neutron capture tumor therapy. However, these liposomes were loaded with stabel elements (e.g. boron), that become radioactive only after activation, and the liposomes contain neither ionophores nor chelator.

[0009] Utkhede et al., (1994) describes liposomes loaded with ⁹⁰Y and the chelator DTPA, which is a different chelator compared to the chelators described in the present invention.Furthermore, retention of mother/daughternuclide(s) is not described and in addition, ⁹⁰Y is not a heavy element as the elements described in the present application.

[0010] Achieving sufficiently stable radiolabeling of carriers with heavy alpha-emitting radionuclides usually requires specific chemical procedures tailored to suit the chemistry of each element, and such methods are not known. Procedures used to radiolabel e.g. Ga, In. Tc. Cu or Re cannot be expected to be compatible with heavy radionuclide (atomic weight over 150) cationic alpha emitters like e.g. ^212/213Bi, ²¹²Pb, ^223/224Ra, ^227Th or ²²⁵Ac.

[0011] It is therefore an object of the present invention to provide a radionuclide-liposome conjugator system, with or without receptor affinic groups, that (1) encapsulates chelator and heavy radionuclide(s) that emit alpha particle radiation, (2) can retain daughter nuclide(s) when the mother nuclide(s) is incorporated in the liposome and (3) can be prepared by an active incorporation procedure useful for a panel of radionuclides, as well as use of the system and a kit for preparing the system. These objects have been obtained by the present invention, characterized by the enclosed claims.

[0012] The present invention relates to a conjugator system comprising liposomes with ionophores, i.e., a metal extracting agent for liposomes, and with chelator and heavy radionuclide(s) (atomic weight over 150) located inside the liposome. The liposomes are prepared using active incorporation of the radionuclide, i.e., via ionophores, and prepared according to procedures yielding liposomes of size of typically 100 nm. The resulting product shows good chemical stability over several days, and may also retain daughter nuclide(s) inside the liposome, e.g. from the transformation of ²¹²Pb to ²¹²Bi. The liposomes can be prepared with or without modifying groups like polyalkylene oxides, e.g., PEG, attached to the membrane. Herein we also describe a method to link such radiolabeled liposomes to tumor seeking proteins, such as e.g. folate conjugated monoclonal antibodies.

[0013] The present invention will now be described in more detail, with reference to figures and examples.

Figure 1 Binding of PEGylated liposomes, containing either Fab' or folate-labeled Fab' antibody conjugated to the liposome membrane, to OVCAR 3 cells.

Figure 2 Binding of folated versus non-folated PEG liposomes to OVCAR 3 cells.

[0014] In order to develop radiolabeled liposomes that are suitable for cancer therapy, the present inventors have studied the preparation and use of liposomes loaded with heavy radionuclides (i.e., atomic weight over 150) emitting alpha particles, based on the radionuclides ²¹²Bi, ²¹³Bi, ²²³ Ra, ²²⁴Ra, ²²⁵Ac, ²¹²Pb and ²²⁷Th. Using liposomes (vesicles) with ionophores, radiolabeled liposomes with preferably a chelator (i.e., the liposomes are encapsulating radionuclide and chelator) were prepared by use of active incorporation of the radionuclide, and prepared according to procedures yielding liposomes of a typical size of 100 nm.

[0015] Unilamellar vesicles were prepared by thin lipid film hydration and extrusion (Olson et al. 1979, Mac Donald et al. 1991) in the following manner: DSPC (distearoyl phosphatidyl choline) and cholesterol in a 2:1 molar ratio, typically 10 and 5 µmol, respectively, were dissolved in chloroform in a round bottom flask. The solvent was removed by rotary evaporation using reduced pressure. The dry lipid film was then hydrated in 0.5-1 ml of 150 mM citric acid, 30 mM DOTA (1,4,7,10 tetraazacyclododecane 1,4,7,10 N, N', N'', N '''tetraacetic acid), pH 4. The resulting suspension was subjected to five cycles of freezing and thawing followed by repeated extrusion through polycarbonate filters of 100 nm pore size 5 times and of 50 nm pore size 5 times employing a manual extruding device (Avestin. Ottawa. Canada). The product had a lipid concentration of ~ 30 mM. Prior to radionuclide loading of the liposomes, the external solution was exchanged by elution on a PD-10 column for 250 mM sucrose, 20 mM HEPES (N-2-hydroxyethylpiperazine-N'-2 ethanesulphonic acid), pH 7.4.

[0016] Liposome constituents: a) Internal aqueous medium: pH 1-14, preferably 2-9, more preferably 4-5. Constituents: Water; agents capable of maintaining the desired pH in the internal aqueous medium for the desired time interval. i.e., until ionophore-mediated incorporation of radiometal(s) is initiated. Preferably, the constituents of the internal aqueous medium also leads to a comnplexing function of the radiometal(s). This can be brought to effect by i) e.g. electrostatic donor functions of the agents used for adjustment pH, e.g. the oxygen atom(s) in acetate, citrate and related compounds; ii) in addition, having a complexing agent in the internal aqueous medium, e.g. EDTA, DTPA, DOTA, DOTMP and related compounds.

b) lonophore: e.g. agent capable of transporting, essentially irreversible, a radio metal across the lipid bilayer from the extraliposomal phase to the liposome interior. Examples: Ionophores showed to function in the desired manner: Calcium ionophore A 23187, Dicyclohexyl 18-C6, Bibenzo-18-C6, 2,3,-dimercapto-1-propanol, Pb-ionophore.

c) Constituents of the lipid bilayer: Constituents of the lipid bilayer preferably result in a mixture capable of forming vesicles, and for which the liquid-to-solid transition temperature is above the physiological temperature; e.g., i) phospholipids. Examples: Long-chained, alkyl-phosphatidylcholines e.g. 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC), 1,2-dinlyristoyl-sn-glycero-3-phosphocholine (DMPC), 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC), 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC); ii) sterols or compounds possessing similar properties in that they stiffens (decrease the fluidity of) the lipid bilayer. Examples: Compounds of the sterol class : Cholesterol and cholesterol 3-sulfate, and iii) (sterically) in vivo stabilizer(s) for increasing tumor-cell targeting properties of the construct and increasing the blood residence time, e.g. polyethers, polyethylene glycols. Inclusion of PEG and/or PEG derivatives in liposome formulations will offer advantages in terms of reduced clearance of injected liposomes from the circulatory system by the reticulo-endothelial system. Normally included in the preparation at 3-10 mol % relative to phospholipid. The amount of stabilizer necessary for obtaining the desired stabilizing effect is, however, dependent of the monomer (electrostatic and polar properties) and the number of repeating units i.e.. the chain length. Examples (PEG and/or PEG derivatives): 1,2-dinlyristoyl-sn-glycero-3-phosphoethano lamine-N-[poly(ethylene glycol) 2000] (PEG2000 DJ\1PE), 1,2-dipalmitoyl-sn-glycero-3-phosphoethano lamine-N-[poly(ethylene glycol)2000 ] (PEG2000 DPPE), 1,2-distearoyl-sn-glycero-3-phosphoethano lamine-N-[poly(ethylene glycol)2000] (PEG2000 DSPE).

d) Constituents facilitating modification of constucts to possess tumor cell targeting properties: The choice of appropriate activated lipid will be determined by the nature of the hapten, as well as the requirements of the investigation. The efficiency of the reaction will be governed by the leaving group, hydrophilic spacer, material properties of the liposome, and the concentration of reactants. For in vivo investigations, in which the hapten is required to remain associated with the liposome, distinct advantages will be gained by choosing longer acyl chain lipid anchors which exchange more slowly between membranes. Further, the covalent bond between hapten and lipid anchor should be stable to both chemical and enzymatic cleavage. The activated lipids can function to form e.g. amine, amide, thioeter, or disulphide bonds between the lipid and modificator. If sterically stabilizers are included in the preparation, e.g. PEG and/or PEG derivatives, the group functioning for coupling is preferably present on the end of a compound equal or similar to the stabilizer and with an effective chain length equal to or longer of than that of the stabilizer. Examples: Vesicle constituents facilitating modification of constructs to possess tumor cell targeting properties from the PEG and/or PEG derivatives: N-[w-(2-pyridyldithiopropionylamino) poly(ethyleneglycol) 2000] 1,2-distearoyl-sn-glycero-3-phosphoethanolamine (PDP-PEG2000-DSPE), N-{w-[4-(p-maleimidophenyl)butanoyl]amino} poly(ethylene glycol) 2000] 1,2-distearoyl-sn-glycero-3-phosphoethanolamine (MpB- PEG2000- DSPE).

[0017] Separation of liposome associated radionuclide from non-associated radionuclide was achieved by the use of size-exclusion chromatography (Mauk and Gamble 1979. Tilcock et al. 1991). For the separations following liposome loading procedures. PD-10 size exclusion columns were employed. From applied volumes of 1 ml or less on the PD-1 0 columns, the liposomes eluted in the first 4.5 ml. Radionuclides not associated with liposomes eluted in the fraction corresponding to low molecular weight species. PD-10 columns were also used in the study of the stability (with respect to radionuclide retention) of the loaded liposomes in

PBS.

[0018] The separation of liposome associated radionuclides from free radionuclides in the serum was performed by size exclusion chromatography on a Sepharose CL-4B column (Hwang and Mauk, 1977). Thereby solutions containing radioactive liposomes dispersed in a liquid carrier substancially free from unbound radionuclides could be prepared.

[0019] EDTA (ethylene diamine N, N' tetra acetic acid) was added prior to the chromatographic procedures to stabilize the free radionuclide in a state that could easily be separated from the liposome associated fraction.

[0020] The radionuclide loading yield for, and the latency of, the liposome associated radionuclides was established by gamma-spectroscopy for ²²⁸Ac, ²²³Ra, ²¹²Pb, ²¹²Bi, ²⁰⁵Bi and ²⁰⁷Bi, ²²⁸Ac and ^205/207Bi were used as a tracer for the potentially therapeutically useful radionuclides ²²⁵Ac, ²¹²Bi and ²¹³Bi, respectively.

[0021] The present inventors made the significant and unexpected discovery that ²¹²Bi did not translocate significantly after the decay of ²¹²Pb incorporated in this type of liposomes. Current status for the use of ²¹²Pb as a molecularly linked generator for ²¹²Bi, indicates that a significant release (≥ 30%) usually occurs from a chelator (McClure and Feinendegen, 1998; Mirzadeh et al., 1993). However, by trapping of the ²¹²Pb in a high concentration of chelator, such as for example inside of the liposome, release of daughter product could be avoided providing a conjugator system that could be used to trap the daughter nuclide after nuclear transformation. This is the first time a conjugator system for ²¹²Pb that could retain the ²¹²Bi daughter nuclide almost quantitatively is reported. Thus, the present invention relates to liposomes with ionophores that comprises radionuclide and chelator located inside the liposome (conjugator system), and wherein this conjugator system can or cannot retain the daughter nuclide.

[0022] A chelator according to the present invention, can be selected from the group comprising 1,4,7.10 tetraazacyclododecane-1,4,7,10 N, N', N", N"'-tetraacetic acid (DOTA),
1,4,7,10 tetraazacyclotridecane-1,4,7,10 N, N', N", N"'-tetraacetic acid (TRITA), 1,4,7,10 tetraazacyclotetradecane-1,4,7,10 N, N', N", N"'-tetraacetic acid (TETA), 1,4,7,10 tetraazacyclododecane-1,4,7,10 N, N', N", N"'-tetra(methylene) phosphonic acid (DOTMP),
1,4,7,10 tetraazacyclotridecane-1,4,7,10 N, N', N", N'''-tetra(methylene) phosphonic acid,
1,4,7,10 tetraazacyclotetradecane-1,4,7,10 N. N', N", N'''-tetra(methylene) phosphonic acid,
diethylene triamine N. N'. N" pentaacetic acid and isomeric derivatives thereof, cryptate[2,2,2], cryptate[3,2,2], cryptate[2,2,1] and mono and di-benzo derivatives thereof.
bridged calix[4]arenes containing electron rich (donor) groups (hydroxyl, carboxyl, ester, amid, amine),
1.10 diaza-4,7,13,16-tetraoxacyclooctadecane-1,10 N, N' bis-acetic acid, and
1.10 diaza-4,7,13,16-tetraoxacyclooctadecane-1,10 N, N' bis-malonate.

[0023] Another important and surprising discovery was that liposomes according to the present invention could incorporate and retain ²²³Ra efficiently. This is the first time that a conjugator system potentially useful for tumor targeting with radium-223 is described. In addition, we show that also bismuth and actinium can be incorporated and strongly retained in the presently described type of liposomes, indicating that conjugator systems based on ²¹²Bi, ²¹³Bi and ²²⁵Ac also can be prepared.

[0024] The conjugator system according to the present invention can be made with or without modifying surface groups. e.g.. PEG, in the liposome membrane (PEG grafted/PEGylated liposomes). The advantage of applying PEG in the membrane is that it provides some PEG-reactive groups that allows conjugation of proteins such as e.g. antibodies, antibody fragments or constructs or folate, or other receptor affinic (receptor binding) proteins/molecules.

[0025] The present application further relates to a new type of liposomes with receptor binding proteins attached to the liposome membrane. Herein we describe radiolabeled PEG grafted liposomes conjugated to folate labeled antibodies. The use of folate and folate derivatives to target tumors expressing folate binding proteins (FBP), a glycosyl-phosphatidyl-inositol-linked cell membrane protein involved in cellular uptake of oxidized folates via endocytosis, has attracted attention among researchers (Kranz et al., 1996; Reddy et al., 1998; Shinoda et al., 1998: Trippet et al., 1999). As several types of human cancer cells have been shown to overexpress FBP, this receptor may be a possible target for delivery of therapeutic radioisotopes conjugated with folate. Thus, by using antibodies conjugated to folate, a targeted radionuclide therapy against cancer could be obtained. Furthermore, if the folate labeled antibody's antigen combining site is directed against a tumor associated antigen different from FBP, dual binding ability is achieved (i.e.. affinity for both the antibody-antigen and FBP receptor is achieved). To our knowledge, this is the first time conjugation of folate-labeled antibodies is described.

[0026] The folate-labeled antibodies conjugated to the liposomes according to the present invention could further be labeled with a radionuclide or a mixture of different radionuclides in order to increase the radiotherapy.

[0027] The present invention shows that this new combination of folate labeled antibodies conjugated to liposomes can be used to target radionuclide(s) to cells expressing folate receptors. This is especially useful with alpha particle emitters, which are high linear energy transfer (high-LET) radiation emitters that are extremely cytotoxic to mammalian cells (Hall, 1994; Larsen et al., 1998; Ritter et al.. 1977). However, an alpha radiation source can deliver radiation to a particularly small area compared to other types of radiation. Thus, if an alpha radiation source can be directed to a target tissue, tissue exposure to normal tissue can be reduced.

[0028] A conjugator system according to the present invention could also be used to target cells expressing e.g. estrogen receptor or testosterone receptor, by conjugating antibodies to estrogen or testosterone.

[0029] The labeled antibodies used according to the present invention are preferably of IgG or IgM class, and/or fragments and/or constructs (e.g. minibody) thereof. Furthermore, these antibodies and/or fragments and/or constructs could be murine, chimeric or fully humanized, polyclonal or monoclonal.

[0030] The present invention also relates to use of the conjugator system according to the present invention, to prepare a pharmaceutical solution suitable for injection or infusion into mammals, including humans, by intravenous and/or regional, and/or intratumoral route of administration. The pharmaceutical solution can be used in combination with a radioimmunoconjugate or several radioimmunoconjugates, and/or other forms of radiopharmaceutical therapy, chemotherapy, external beam therapy or surgery, to treat malignancies.

[0031] The present invention also relates to manufacture the conjugator system according to the present invention to treat malignancies such as e.g. brain-, lung-, cervix-, ovary- or breast cancer, or leukemia, lymphoma or malignant melanoma.

[0032] The present invention also relates to a kit for the preparation of the conjugator system according to the present invention, comprising a vial containing a liposome solution and a second vial containing radionuclide in a solution, that can be mixed to facilitate radiolabeling. In addition, this could be mixed with a third vial containing a proteins and/or molecules with receptor affinity to obtain a receptor affinic conjugator system.

Reagents and equipment

[0033] Gamma-spectroscopy was performed using a germanium detector (Canberra, Meriden, CT, USA) coupled to a multichannel analyzer (EG&G ORTEC. Oak Ridge, TN, USA). A Beckmann LS 6500 (Beckmann, Fullerton, CA. USA) was used for liquid scintillation counting. DSPC and cholesterol purchased from Northern Lipids (Vancouver. Canada). Sephadex G-25 PD-10 columns (Amersham Pharmacia Biotech AB, Uppsala, Sweden) was used for the purification of radiolabeled liposomes. The macrocyclic chelator DOTA was used as intra-liposomal chelator and was purchased from Macrocyclics (Richardson, TX. USA). Ultrex grade HNO₃ (J.T. Baker, Phillipsburg. NJ, USA) and 6M HCl (Fisher Scientific. Pittsburgh. PA. USA) and bis(2-ethyl hexyl) phosphoric acid (HDEHP) from Fluka (via Sigma-Aldrich AS, Norway) was used in the study.

[0034] All buffers used for the ionophore mediated cation loading of liposomes were adjusted to the desired pH using arginine (free base). All water used was obtained from a Milli-Q water purification system (Millipore, Bedford, MA. USA).

[0035] Ion exchange resins were supplied by Bio-Rad (Hercules, CA, USA).

[0036] The resins was preconditioned by washing with water, then 6 M HCl followed by acetone and finally with water. The resins were stored in water prior to column packing.

[0037] The DMSO used was stored with 4 Å sieves.

[0038] The ²³²Th(NO₃)₄ used in this work had been stored for more than 20 y. The sample was provided by Nuclear Chemistry Group, Department of Chemistry University of Oslo, Oslo, Norway.

[0039] ³H-folic acid was purchased from Amersham Pharmacia Biotech (Buckinghamshire, UK).

[0040] All other chemicals were purchased from Sigma-Aldrich, Norway.

[0041] Table 1 shows some physical properties of radionuclides used in experiments with liposomes.

Table 1

Nuclide	t1/2	gamma-ray(s)	% probability*
228Ac	6.13h	911.2 (26.6)	26.6
223Ra	11.43d	269.4 (13.7) 271.2 (0.108) (219Rn)2	13.7 10.8
212Pb	10.6h	238.6 (43.6)	43.6
208Tl	3.05m	583.1 (32.5)	35.2
207Bi	31.55y	569.7 (97.7)	97.7
205Bi	15.31d	703.4 (31.1)	31.1

*Only the most abundant gamma-ray is listed for each radionuclide. Data from Nuclear Data Sheets, Academic Press INC.

Best mode

[0042] Liposomes prepared according to the described procedures were loaded with radium-223 or lead-212. Thereafter, antibodies were reacted with liposomes to achieve antibody molecules on the surface of the liposomes. Lipsome size of about 100 µm will be appropriate for systemic delivery, but typical sizes of 200-1000 µm can be used when intracavitary delivery, e.g., for the treatment of intracranial brain tumor, or for the treatment of intraperitoneal ovarian cancer, is to be achieved. (The larger liposome size could slow down clearance rate from the cavity where the preparation is injected, thereby maintaining a high concentration in the tumor region.)

EXAMPLES

Example 1. Loading of ²¹²Pb/²¹²Bi in liposomes

[0043] Methods: ²¹²Pb/²¹²Bi was produced via emanation of ²²⁰Rn from a ²²⁸Th source as described by Hassfjell and Hoff (1994). No carrier added ²¹²Pb/²¹²Bi was leached from the collection vessel using 0.1 M HNO₃, and the solution applied to a 2x20 mm column of AG 50W-X4 cation exchange resin. ²¹²Pb/²¹²Bi was then eluted in 2 M HCl and the solution evaporated to dryness. The ²¹²Pb/²¹²Bi was then dissolved in 200 µl 10 mM acetate solution, pH 5. ²¹²Pb was quantified by measurement of its 238.6 keV gamma-ray (Table 1). ²¹²Bi was quantified by measuring the 583.1 keV gamma-ray of its daughter ²⁰⁸Tl at radioactive equilibrium.

[0044] Results: Less than 0.2% of the added activity was found to be associated with the liposomes for incubation times up to 3 days.

[0045] Liposomes corresponding to a lipid concentration of 30-60 mM was vigorously mixed with a film of the ionophore A23187 (10-13 nM). Approximately 1 MBq of ²¹²Pb/²¹²Bi was then added and the mixture was incubated at 75 °C for 30 min, followed by elution on a PD-10 column. The fraction containing more than 95% of the loaded vesicles was then eluted on a second PD-10 column. The latency of the liposome associated ²¹²Pb/²¹²Bi was investigated by incubating the vesicles at 37 °C in human serum or PBS. The activity distribution was followed over a 24 h period.

Results: Loading efficacy of ²¹²Pb: 34.8 % (n=3).

[0046] Retention was measured by gamma spectroscopy, and more than 99% of the ²¹²Pb was associated with the liposomes for incubation times up to 24h.

Example 2: Retention of ²¹²Bi formed from the decay of liposome-associated ²¹²Pb

[0047] Methods: Liposomes were loaded with ²¹²Pb as described above. The liposome associated radioactivity was isolated by eluting the reaction mixture with 10 mM EDTA in PBS on a PD-10 column pre-equilibrated with 10 mM EDTA in PBS.

[0048] After 3 hours, in order to ensure that transient equilibrium between ²¹²Pb and ²¹²Bi was established, aliquots of the solution were applied to PD-10 columns pre-equilibrated with 10mM EDTA in PBS for separation of free radionuclides from liposome-associated radionuclides. The activity distribution was followed over a 24 h period.

[0049] A separate aliquot of the labeled liposomes that did not undergo the separation procedure (of identical geometry to that obtained from chromatographical procedures) was measured for use as a standard. This was performed to establish the activity ratio of ²¹²Bi/²¹²Pb at radioactive equilibrium.

[0050] Results: By comparing the ratio of ²¹²Bi/²¹²Pb obtained for the chromatographically separated liposomes with that of the equilibrium mixture, it was estimated that more than 95% of the ²¹²Bi was shown to be retained in the liposomes after the decay of liposome associated ²¹²Pb.

[0051] Additionally, measurements of the ²¹²Bi activity in the two chromatographically obtained fractions were compared. More than 99% of the total ²¹²Bi activity eluted in the fractions corresponding to the liposomes.

Example 3: Investigating possible Pb and Bi reloading in liposomes

[0052] Methods: Liposomes corresponding to 30-60 mM lipid, entrapping 150 mM citric acid. 30 mM DOTA. and using an external solution containing 10 mM EDTA in PBS were added to a film of the ionophore A23187 (20-26 nmol on the inside surface of a glass vial). ²¹²Pb and ²¹²Bi in PBS was then added followed by incubation at 37 °C. Aliquots of the solution were eluted through PD-10 columns and the chromatographically obtained fractions corresponding to the liposome-eluate was assayed by the intrinsic Ge-detector.

Results: No detectable loading (< 1%) of ²¹²Pb and ²¹²Bi was observed over a 24 h time period.

Example 4: Loading of ²²³Ra in liposomes

[0053] ²²³Ra was produced from a generator based on ²²⁷Ac as described (Larsen and Henriksen, 1999). Briefly, ²²⁷Ac and its daughter nuclide ²²⁷Th are retained in a column of an extraction chromatographic resin facilitating elution of ²²³Ra using a mineral acid. For incorporating radium into liposomes, the eluted solution from the generator was evaporated to dryness and ²²³Ra was then dissolved in 5 mM citrate, pH 7.4.

[0054] Liposomes corresponding to a lipid concentration of 30-60 mM was vigorously mixed with a film of the ionophore A23187 (10-13 nmol on the inner surface of a glass vial). Thereafter, approximately 50 kBq of ²²³Ra was added and the mixture incubated at 75 °C for 20 min. The reaction mixture was then added to 100 µl of 10 mM EDTA, and eluted on a PD-10 column for isolating the radioactivity associated with the lipid vesicles.

[0055] The retention of the liposome associated ²²³Ra was investigated by incubating the vesicles at 37 °C in human serum (Sigma) or 5 mM EDTA in human serum at a liposome concentration of 0.3mg total lipid/ml serum. The results are exhibited in the Table 2. and demonstrate that ²²³Ra is very stably retained in the liposomes.

Table 2

Incubation time (days)	% of total 223Ra in liposome fraction
1	94.6 ± 1
3	94 ± 2.5
4	94.7 ± 0,5
Mean s.d. , n=4

Example 5. Determining if reloading would contribute in the ²²³Ra retention experiment.

[0056] Methods: Liposomes corresponding to 30-60 mM of lipid, formed by hydration of lipid films with 150 mM citric acid, 30 mM DOTA. external solution PBS or serum were added to a film of the ionophore A23187 (10-13 nmol distributed on the inside surface of a glass vial). ²²³Ra in 5 mM citrate pH 7.4 was then added followed by incubation at 37 °C. Aliquots of the solution were applied to PD-10 columns and the chromatographically obtained fraction corresponding to the liposomes was assayed by the intrinsic Ge-detector.

Example 6: Loading of ²⁰⁷Bi in liposomes

[0057] Methods: ^203-207Bi was produced by (p. xn) reactions on natural lead targets and purified by using a lead selective extraction chromatographic resin (Henriksen and Hoff, 1998).

[0058] An isotopic Bi-mixture consisting mainly of ²⁰⁵Bi and ²⁰⁷Bi, hereafter denoted as ²⁰⁷Bi, was used in this study. 50 µl of a solution of ²⁰⁷Bi in 10^-4 M HCl was added to the liposomes, corresponding to 30-60 mM of lipid, which in advance had been mixed with a film of the ionophore A23187 (10-13 nmol on the inner surface of a glas vial) and incubated for 30 min at 75 °C. The reaction mixture was then added 100 µl of 10 mM EDTA, and eluted on a PD-10 column to isolate the radioactivity associated with the lipid vesicles.

[0059] Results: 32% of the total ²⁰⁷Bi was found to be associated with the liposomes.

Example 7. Loading of ²²⁸Ac in liposomes

[0060] Methods: ²²⁸Ac was isolated from a ²³²Th(NO₃)₄ preparation by a combination of solvent extraction and ion exchange. ²³²Th(NO₃)₄ (4H₂O originally) was dissolved in 20 ml 0.1 M HNO₃ and added to a 500 ml separation funnel and contacted with 5x100 ml of a 2 M solution of HDEHP in heptane. The aqueous phase was then washed three times with heptane and thereafter applied to a 3x40 mm column of AG50W-X12 cation exchange resin for isolation of ²²⁸Ac as described (Cabell, 1959). From the column, ²¹²Pb, ²¹²Bi, ²²⁴Ra and ²²⁸Ra was eluted in 3 M HNO₃ and the solution was left for >20 h. The solution was then evaporated to dryness followed by leaching the radionuclides from the vessel with 1 ml 1 M HNO₃. This solution was applied to a 3x40 mm column of AG50W-X12. Again. ²¹²Pb, ²¹²Bi, ²²⁴Ra and ²²⁸Ra was eluted in 3 M HNO₃. ²²⁸Ac was eluted in 6 M HNO₃ and the eluate evaporated to dryness. ²²⁸Ac was then leached form the vessel using 200 µl 5 mM HNO₃. Approximately 6 kBq of ²²⁸Ac was added to the liposomes containing the ionophore A23187 as described above, and incubated for 60 min at 75 °C. The reaction mixture was then added to 100 µl of 10 mM EDTA. and eluted on a PD-10 column to isolate the radioactivity associated with the lipid vesicles. Fractions corresponding to more than 95% of the loaded vesicles were pooled and then eluted on a second PD-10 column. The liposomal retention of ²²⁸Ac was investigated by incubating the radiolabeled vesicles at 37 °C in human serum or PBS. The activity distribution was followed over a 24 h period.

[0061] Results: In the loading experiment 90-95% of the added ²²⁸Ac (corrected for decay during labeling and purification) was associated with the liposomes after the loading procedure. In the retention experiment more than 98% of the ²²⁸Ac was found to be associated with the liposomes for incubation times up to 24 h.

Example 8: Loading of ⁹⁰Y

[0062] Methods: ⁹⁰Y was used as a tracer in this example to study the behavior of radiolabeled liposomes. ⁹⁰Y and ⁹⁰Sr was measured by liquid scintillation counting in this study.

[0063] ⁹⁰Y was isolated from ⁹⁰Sr by means of a strontium selective extraction chromatographic resin as described by Dietz and Horwitz (1992). Here, ⁹⁰Sr (Amersham, Buckinghamshire, England) in 0.1 M HNO₃ was evaporated to dryness and residue added 3 M HNO₃. The solution was loaded onto a 3x20 mm column of Sr-resin (EiChroM. Darien. IL, USA) and the column washed with 5 ml 3 M HNO₃.

[0064] This procedure selectively elutes ⁹⁰Y while Sr is sufficiently retained on the column to lower the ⁹⁰Sr content of a ⁹⁰Sr/⁹⁰Y mixture by a factor of approximately 10³ (Dietz and Horwitz, 1992). After this, ⁹⁰Sr was stripped from the column using 0.05 M HNO₃ and this solution was left for one week in order to allow ⁹⁰Y to grow in. Then, the solution was evaporated to dryness and the residue added 3 M HNO₃ before separating the radionuclides on a second column of Sr-Resin. The eluate containing ⁹⁰Y was evaporated to dryness and the radionuclide leached form the vessel using 200 µl 5 mM HNO₃. This solution was added to liposomes containing the ionophore A23187 (as described previously) and incubated for 60 min at 75 °C. The reaction mixture was then added 50 µl 10 mM EDTA, and eluted on a PD-10 column for isolating the radioactivity associated with the lipid vesicles. The fraction corresponding to more than 95% of the vesicles was then eluted on a second PD-10 column. The liposome retention of the liposome associated ⁹⁰Y was investigated by incubating the vesicles at 37 °C in human serum or PBS. The activity distribution was followed over a 4 day-period.

[0065] Results: More than 95 % of the added ⁹⁰Y was associated with the liposomes after 1 hour of loading and purification on gel exclusion column.

[0066] In the study of the liposomal retention the following results were obtained: after 5h and 1 day more than 99% was liposome associated. After 4 days the liposome associated fraction was determined to be 98 ±1 %.

[0067] As shown in these experiments liposomes can be radiolabeled with alpha-particle and/or beta-particle emitting radionuclides and retain these nuclides well at physiological temperature.

Example 9: Preparation of Yttrium-90/Radium-223 PEGylated liposome-folate-Fab'

[0068] F(ab')₂ RØ myeloma (Subclass IgG₁) 14mg/ml in PBS was used for this experiment (Michalsen. Norwegian Institute of Public Health. Oslo, Norway).

Conjugation of folic acid to antibodies

[0069] Folic acid ●2H₂O was firstly dissolved in dimethyl sulfoxide (Fluka, H₂O content less than 0.05%). The solution was then cannulated onto activated 4 Å sieves (Fluka) and stored under an argon atmosphere in the dark for 6-10 hours. Tritium labeled folate (³H-folate) was added as an aqueous solution of the potassium salt of ³H-folate (1% with respect to citric acid). The specific activity of the ³H-folate used for conjugation to protein was 7-7.5 GBq/mol.

[0070] The ³H-folate was activated for coupling to F(ab')₂ myeloma antibody by adding 10 mol equivalents of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide to the folate solution and incubating for 30 min at ambient temperature. Thereafter, a 30-40-fold molar excess of the activated folate was added to protein, 14 mg/ml in PBS, and allowed to react for 30-60 min. The reaction was quenched by adding 0.2 ml of 0.3 M glycine in PBS/borate, pH 8.5. The folate F(ab')₂ conjugate (folate-F(ab')₂) was separated from unreacted material using a PD-10 column preequillibrated in PBS. In order to form folate-Fab', folate-F(ab')₂ was incubated in 1 mM Dithiotreitol (DTT) at ambient temperature for 2 h followed by elution on a NAP-5 size exclusion column. The fraction containing folate-Fab' was deoxygenated by bubbling Argon through the solution where after the solution was immediately mixed with the liposome solution.

[0071] The extent of folic acid conjugation was determined by the ³H-content of the purified protein as measured by liquid scintillation counting (Beckmann LS6500) combined with spectrophotometrical readings at 280nm.

[0072] For quantification of the liposome bound fraction of folate-Fab'. a trace amount of iodinated F(ab')₂ was added prior to the reaction with DTT (the protein was iodinated via IodoGen according to standard procedures).

Conjugation of labeled antibodies to liposomes

[0073] DSPE-PEG2000-MPB (Northern Lipids. VA. Canada), sodium salt was included at 5 mol % of total phospolipid. Liposomes were otherwise constituted and were also prepared for the ionophore mediated cation loading step in an identical manner to that described for the non-PEGylated liposomes.

[0074] After allowing the reaction mixture after the loading step to reach room temperature the liposome suspension was deoxygenated prior to adding folate-Fab' to obtain a protein concentration of 0.3-0.5 mg/ml. Lipid concentration was 1-3 mM as determined by the Bartlett phosphorous assay (Bartlett, 1958). The folate-Fab' and liposomes were allowed to react for 2 h at ambient temperature. The reaction mixture was then applied using a PD-10 column equilibrated in PBS. folate-Fab' conjugated PEG-liposomes were stored at 4 °C for 12-15 h prior to use in the folate-receptor binding assays .

[0075] Liposome-bound radioactivity was measured by a NaI well type detector correcting for the spillover in the respective channels from the doubly labeled samples. Samples of single nuclide and a mixtures of the nuclides were used as reference.

[0076] From the radioactivity measurements, the protein concentration was converted to the number of Fab' per liposome assuming a liposome size of 100 nm and 8●10⁴ phospholipids/vesicles (Kirpotin et al. 1997) and a molecular weight of the Fab' Myeloma antibody equal to 52 000.

[0077] The cell bound radioactivity was measured by the NaI-detector (3 higher concentrations for Y-90) and liquid scintillation counting after adding Insta-Gel plus (Packard) (Table 3).

Table 3. Binding of 90Y-liposomes conjugated with antibodies with or without folate, to OVCAR cells.
Added liposome/cell	% cell bound folat-negative liposomes	% cell bound folat-positive liposomes
1●105	<0,5	10 ± 3
1●104	1 ± 0.5	9 ± 3
1●103	4 ± 2	11 ± 2
1●102	5 ± 1	16 ± 2
10	8 ± 3	46 ± 8

Detection of ³H-folate on liposomes

[0078] PEG liposomes (2.5 mM lipid conc.) in 20 mM HEPES/300 mM sucrose was reacted with ³H-folate conjugated Fab' (0.5mg/ml in PBS. folate/Fab ratio of 2 ± 0.2). After 2 h at room temperature, the folate-Fab' coupled liposomes were isolated by elution on a column of Sepharose CL-4B. The amount of ³H-folate-Fab' on the liposomes was quantified by liquid scintillation counting of the chromatographically obtained fractions, and the folate-Fab'/liposome ratio was determined to be approximately 110 .

Abbreviations:

[0079] 

DSPC :

distearoyl phosphatidyl choline

DOTA :

1,4.7.10 tetraazacyclododecane 1.4,7,10 N, N', N'', N''' tetraacetic acid

DSPE-PEG2000-MPB:

N-(4-(p-Maleimidophenyl)butyryl)-1,2-distearoyl-sn-glycero-3-phosphoethanolamine (Northern Lipids. VA, Canada).

HEPES :

N-2-hydroxyethylpiperazine-N'-2 ethanesulphonic acid

PBS

: phosphate buffered saline

EDTA :

ethylene diamine N. N' tetra acetic acid

HDEHP:

bis(2-ethyl hexyl) phosphoric acid

PEG

: poly etylene glycol

DTT :

dithiotreitol

References:

[0080] 

Bartlett GR. Phosphorus assay in column Chromatography. J. Biol. Chem. 234 (3), 466-468 (1958).

Cabell MJ. The purification, determination and neutron capture cross section of actinium-227. Can. J. Chem. 37, 1094-1101, (1959).

DeVita Jr VT, Hellman S. Rosenberg SA. Cancer. Principles & practice of oncology. 5th edition Lippincot-Raven, Philadelphia. New York, USA (1997).

Dietz ML and Horwitz EP. Improved chemistry for the production of Y-90 for medical applications. Appl. Radiat. Isot. 43, 1093-1101 (1992).

Forssen EA. The design and development of DaunoXome® for solid tumor targeting in vivo. Adv. Drug Delivery Rev. 24. 133-150 (1997).

Gabizon R, Horowitz AT, Goren D, Tzemach D, Mandelbaum-Shavit F, Quasen MM, and Zalipsky S. Targeting Folate receptor with folate linked to extremities of poly(ethylene glycol)-grafted liposomes: In vitro studies. Bioconjugate Chem. 10, 289-298 (1999).

Gabison A. Liposome circulation time and tumor targeting: Implication for cancer chemotherapy. Adv. Drug Delivery Rev. 16, 285-294 (1995).

Gaze MN. The current status of targeted radiotherapy in clinical practice. Phys. Med. Bol. 41, 1895-1903 (1996).

Goins B. Phillips WT. and Klipper R. Repeat injection studies of technetium-99m labeled PEG-liposomes in the same animal. J. Liposome Res. 8(2), 265-281 (1998).

Hall E. Radiobiology for the radiologist. Fourth Edn. JB Lippincott Company, Philadelphia, USA (1994).

Hassfjell SP and Hoff P. A generator for production of Pb-212 and Bi-212.

Appl. Radiat. Isot. 45. 1021-1025 (1994).

Henriksen G and Hoff P. Isolation of cyclotron produced Bi-205, Bi-206 and Pb-203 using a lead-selective extraction chromatographic resin. Appl. Radiat. Isot. 49, 357-359 (1998).

Hwang KJ and Mauk MR. Fate of lipid vesicles in vivo: A gamma-ray perturbed angular correlation study. Proc. Nati. Acad. Sci. USA. 74, 4991-4995 (1977).

Kirpotin D, Park JW. Hong K. Zalipsky S. Wen-Lu L, Carter P, Benz CC and Papahadjopoulos D. Sterically stabilised Anti-HER2 Immunoliposomes: Design and targeting to human breast cancer cells in Vitro. Biochemistry. 36, 66-75, (1997).

Kostarelos K. Emfietzoglou D and Stamatelou M. Liposome-mediated delivery of radionuclides to tumor models for cancer radiotherapy: A quantitative analysis. J. Liposome Res. 9 (3), 407-424 (1999).

Kranz. DM. Roy, EJ and Patrick. TA. Conjugates of folate anti-effector cell antibodies. United States Patent number: 5 547 668 (20. Aug. 1996).

Larsen RH, Akabani G, Welsh P and Zalutsky MR. The cytotoxicity and microdosimetry of astatine-211-labeled chimeric monoclonal antibodies in human glioma and melanoma cells in vitro. Radiat. Res. 149, 155-162 (1998).

Larsen RH. Henriksen G. Norwegian Patent application No P990001 (1999).

Lee RJ and Low PS. Delivery of liposomes into cultured KB cells via folate receptor-mediated endocytosis. J. Biol. Chem. 269, 3198-3204 (1994).

MacDonald RC. MacDonald RI, Menco BPhM., Takeshita K, Subbarao NK and Hu Lan-rong. Small-volume extrusion apparatus for preparation of large, unilamellar vesicles. Bioch. Biophys. Acta 1061, 297-303 (1991).

Maruyama K, Takizawa T, Takahashi N, Tagawa T, Nagaike K and Iwatsuru M. Targeting efficiency of PEG-immunoliposorne-conjugated antibodies at PEG terminals. Adv. Drug Delivery Rev. 24. 235-242 (1997).

Mauk MR and Gamble RC. Preparation of lipid vesicles containing high level of entrapped radioactive cations. Anal. Biochem. 94, 302-307 (1979).

McClure JJ and Feinendegen, LE. Alpha-emitters for medical therapy: Second Biannual Workshop, Toronto, Canada, June 4-5, (1998). Report from Department of Energy. Germantown, MD, USA

Mirzadeh S, Kumar K, Ganzow. OA. The chemical fate of 212Bi-DOTA formed by b-decay of 212Pb(DOTA)2-. Radiochimica Acta, 60, 1-10 (1993).

Ogihara-Umeda I, Sasaki T. Kojima S. Nishigori H. Optimal radiolabeled liposomes for tumor imaging. J. Nucl. Med. 37 (2), 326-332 (1996).

Olson F, Hunt CA, Szoka F, Vail WJ and Papahadjopoulos D. Preparation of liposomes of defined size distribution by extrusion through polycarbonate membranes. Bioch. Biophys. Acta 557, 9-23 (1979).

Pikul II SS, Parks NJ. Schneider PD. In vitro killing of melanoma by liposome delivered intracellular irradiation. Arch. Surg. 122, 1417-1420 (1987).

Reddy. JA and Low. PS. Folate-mediated targeting of therapeutic and imaging agents to cancers. Critical Reviews in Therapeutic Drug Carrier Systems 15 (6): 587-627 (1998).

Ritter MA, Cleaver JE. and Tobias CA. High-LET radiations induce a large proportion of non-rejoining DNA-breaks. Nature 266, 653-655 (1977).

Shinoda, T, Takagi, A, Maeda, A. Kagatani, S, Konno, Y and Hashida, M. In vivo fate of folate-BSA in non-tumour- and tumour-bearing mice. J Pharm Sci 87 (12): 1521-1526, 1998.

Tilcock CP. Ahkong QF and Parr M. An improved method for the preparation of liposomal gadolinium-DTPA- Ionophore-Mediated active entrapment of gadolinium. Invest. Radiol. 26. 242-247 (1991).

Trippett, TM and Bertino, JR. Therapeutic strategies targeting proteins that regulate folate and reduced folate transport. J Chemotherapy 11: 3-10 (1999).

Turner AF, Presant CA, Proffitt RT, Wiliams LE, Winsor DW and Werner JL. In-111-labeled liposomes: Dosimetry and tumor depiction. Radiology 166 (3), 761-765 (1988).

Utkhede D, Yeh V, Szucs M and Tilcock C. Uptake of Yttrium-90 into lipid vesicles. Jour. Lip. Res. 4(2), 1049-1061 (1994).

Claims

1. Conjugator system, characterized in that it comprises liposomes with ionophores and with chelator located inside of the liposomes, the liposomes further encapsulates heavy radionuclide(s) emitting α particles or ²¹²Pb as a generator for the α-emitter ²¹²Bi, wherein the heavy radionuclides has an atomic weight of greater than 150.

2. Conjugator system according to claim 1, characterised in that the concentration of chelator inside the liposomes is suitable.to retain daughter nuclides.

3. Conjugator system according to any of the claims 1 to 2, characterised in that a chelator is selected from the group comprising 1,4,7,10 tetraazacyclododecane-1,4,7,10 N,N',N",N"'-tetraacetic acid (DOTA),
1,4,7,10 tetraazacyclotridecane-1,4,7,10 N,N',N",N'''-tetraacetic acid (TRITA)
1,4,7,10 tetraazacyclotetradecane-1,4,7,10 N,N',N",N"'-tetraacetic acid (TETA),
1,4,7,10 tetraazacyclododecane-1,4,7,10 N,N',N",N"'-tetra (methylene) phosphonic acid (DOTMP),
1,4,7,10 tetraazacyclotridecane-1,4,7,10 N,N',N",N"'-tetra(methylene) phosphonic acid,
1,4,7,10 tetraazacyclotetradecane-1,4,7,10 N,N',N",N"'-tetra(methylene) phosphonic acid, diethylene triamine N,N',N" pentaacetic acid and isomeric derivatives thereof , cryptate[2,2,2], cryptate[3,2,2], cryptate[2.2,1] and mono and di-benzo derivatives thereof, bridged calix[4]arenes containing electron rich (donor) groups (hydroxyl, carboxyl, ester, amid, amine),
1,10 diaza-4,7,13,16-tetraoxacyclooctadecane 1,10 N,N' bis-acetic acid, and
1,10 diaza-4,7,13,16-tetraoxacyclooctadecane 1,10 N,N' bis-malonate.

4. Conjugator system according to any of the claims 1 to 3, characterised in that the liposomes contain activated groups in the membrane allowing conjugation of proteins or other receptor affinic molecules to these activated groups.

5. Conjugator system according to claim 4, wherein said activated groups are poly ethylene glycol.

6. Conjugator system according to any of the claims 1 to 5, characterised in that the liposomes are conjugated to receptor binding proteins.

7. Conjugator system as claimed in claim 6 wherein said receptor binding proteins are monoclonal or polyclonal antibodies, or antibody fragments or constructs, or folate.

8. Conjugator system according to claim 6, characterised in that the liposomes are conjugated with antibodies of IgM or IgG class, or fragments or constructs from these classes of antibodies.

9. Conjugator system according to claim 6, characterised in that the liposomes are conjugated with antibodies of IgM or IgG class, or fragments or constructs from these classes of antibodies, wherein the antibodies, fragments or constructs are labelled with folate and a radionuclide or a mixture of different radionuclides.

10. Conjugator system according to any of the claims 1 to 9, characterized in that the antibodies or antibody fragments or constructs conjugated to the liposomes are murine, chimeric or human, monoclonal or polyclonal.

11. Conjugator system according to claim 10, characterised in that the antibodies or antibody fragments or constructs are labelled with folate, wherein the antigen binding site is directed towards folate binding protein (FBP).

12. Conjugator system according to claim 10, characterised in that the antibodies or antibody fragments or constructs are labelled with folate, wherein the antigen binding site is directed towards an antigen different, from FBP.

13. Conjugator system according to any of the claims 1 to 12, characterised in that the radionuclide is a heavy alpha emitter and/or ²¹²Pb as a generator for the α-emitter ²¹²Bi, selected from ²¹¹At, ²¹²Bi, ²¹³Bi, ²¹²Pb ²²⁵Ac, ²²³Ra, ²²⁴Ra and ²²⁷Th.

14. Conjugator system according to any of the claims 1 to 13, characterised in that the daughter nuclide and the mother nuclide are ²¹²Bi and ²¹²Pb, respectively.

15. Method to prepare a radiolabeled conjugator system, characterised in that liposomes with ionophores and chelator of a suitable concentration are stably radiolabeled with heavy α- particle emitters, by mixing a solution containing radionuclide or a mixture of radionuclides which emits α-particle radiation or ²¹²Pb as a generator for the α-emitter ²¹²Bi, wherein the heavy α- particle emitters have atomic weight greater than 150 with a solution containing liposomes and incubate at elevated temperature compared to physiological temperature to obtain transport of the radionuclide(s) into the liposomes.

16. Method according to claim 15, characterised in that the chelator is selected from the group comprising 1,4,7,10 tetraazacyclododecane-1,4,7,10 N,N',N",N"'-tetraacetic acid (DOTA),
1,4,7,10 tetraazacyclotridecane-1,4,7,10 N,N',N",N"'-tetraacetic acid (TRITA),
1,4,7,10 tetraazacyclotetradecane-1,4,7,10 N,N',N",N"'-tetraacetic acid (TETA),
1,4,7,10 tetraazacyclododecane-1,4,7,10 N,N',N",N"'-tetra(methylene) phosphonic acid (DOTMP),
1,4,7,10 tetraazacyclotridecane-1,4,7,10 N,N',N",N"'-tetra(methylene) phosphonic acid,
1,4,7,10 tetraazacyclotetradecane-1,4,7,10 N,N',N",N"'-tetra(methylene) phosphonic acid,
diethylene triamine N,N',N" pentaacetic acid and isomeric derivatives thereof, cryptate[2,2,2], cryptate[3,2,2], cryptate[2,2,1] and mono and di-benzo derivatives thereof, bridged calix[4]arenes containing electron rich (donor) groups (hydroxyl, carboxyl, ester, amid, amine),
1,10 diaza-4,7,13,16-tetraoxacyclooctadecane-1,10 N,N' bis-acetic acid, and
1,10 diaza-4,7,13,16-tetraoxacyclooctadecane-1,10 N,N' bis-malonate.

17. Method according to any of the claims 15 to 16, characterised in that the liposomes contain activated groups in the membrane allowing conjugation of proteins or other receptor affinic molecules.

18. Method according to claim 17, characterised in that the activated groups are poly ethylene glycol.

19. Method according to any of the claims 15 to 18, characterised in that the liposomes are conjugated to receptor binding proteins.

20. Method as claimed in claim 19 wherein said receptor binding proteins are monoclonal or polyclonal antibodies or antibody fragments or constructs or folate.

21. Method according to claim 19, characterized in that the liposomes are conjugated with antibodies of IgM or IgG class, or fragments or constructs from these classes of antibodies

22. Method according to claim 19, characterised in that the liposomes are conjugated with antibodies of IgM or IgG class, or fragments or constructs from these classes of antibodies, wherein the antibodies are labelled with folate and a radionuclide or a mixture of different radionuclides, using standard procedures for folate and radionuclide labelling of the antibody.

23. Method according to any of the claims 15 to 22, characterised in that an antibody or antibody fragments or constructs conjugated to the liposomes are murine, chimeric or human, monoclonal or polyclonal.

24. Method according to claim 23, characterised in that the antibody or antibody fragments or constructs are labelled with folate, wherein the antigen binding site is directed towards FBP.

25. Method according to claim 23, characterised in that the antibodies or antibody fragments or constructs are labelled with folate, wherein the antigen binding site is directed towards an antigen different from FBP.

26. Method according to any of the claims 15 to 25, characterised in that the radionuclide is a heavy alpha emitter or ²¹²Pb as a generator for the α-emitter ²¹²Bi, selected from ²¹¹At, ²¹²Bi, ²¹³Bi, ²¹²Pb ²²⁵Ac, ²²³Ra, ²²⁴Ra and ²²⁷Th.

27. Method according to any of the claims 15 to 26, characterised in that the daughter nuclide and the mother nuclide are ²¹²Bi and ²¹²Pb, respectively.

28. Process for the manufacture of the conjugator system according to any of the claims 1 to 14, suitable for injection or infusion into mammals, including humans.

29. Process according to claim 28, to prepare a pharmaceutical solution suitable for injection or infusion into mammals, including humans, by intravenous, and/or regional, and/or intratumoral route of administration.

30. Use of the conjugator system according to any of the claims 1-to 14 to prepare a pharmaceutical solution suitable for injection or infusion into mammals including humans in combination with a radioimmunoconjugate or several radioimmunoconjugates and/or other forms of radiopharmaceutical therapy, chemotherapy external beam therapy or surgery to treat malignancies.

31. Use of a conjugator system as claimed in any one of claims 1 to 14 for the manufacture of a medicament for injection into human subjects for the purpose of delivering potentially therapeutic radiation to malignant cells expressing receptors selected from folate binding protein, oestrogen receptor and testosterone receptor.

32. The use as claimed in claim 31 wherein said malignant cells are derived from malignant tissue selected from brain cancer, lung cancer, cervical cancer, ovarian cancer, breast cancer, leukaemia, lymphoma and malignant melanoma.

33. Kit for the preparation of the conjugator system according to any of the claims 1 to 14, characterised in comprising a vial containing a liposome solution and a vial containing radionuclide in a solution that can be mixed to facilitate radiolabeling.

34. Kit for the preparation of the conjugator system according to any of the claims 1 to 14, characterised in comprising a vial containing a liposome solution and a second vial containing radionuclide in a solution and a third vial containing a molecule with receptor affinity, that can be mixed to facilitate radiolabeling and labelling with a receptor affinic molecule.

Ansprüche

1. Konjugatorsystem, dadurch gekennzeichnet, dass es Liposomen mit lonophoren und mit im Inneren der Liposomen angeordnetem Chelator umfasst und die Liposomen außerdem (ein) α-Teilchen emittierende(s) schwere(s) Radionuklid(e) oder ²¹²Pb als Generator des α-Emittors ²¹²Bi umschließen, wobei das (die) schwere(n) Radionuklid(e) ein Atomgewicht von mehr als 150 aufweist (aufweisen).

2. Konjugatorsystem nach Anspruch 1, dadurch gekennzeichnet, dass die Konzentration des Chelators im Inneren der Liposomen geeignet ist, Tochtemuklide zu binden.

3. Konjugatorsystem nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass ein Chelator ausgewählt ist unter 1,4,7,10-Tetraazacyclododecan-1,4,7,10-N,N',N",N'''-tetraessigsäure (DOTA),
1,4,7,10-Tetraazacyclotridecan-1,4,7,10-N,N',N",N'''-tetraessigsäure (TRITA), 1,4,7,10-Tetraazacyclotetradecan-1,4,7,10-N,N',N",N'''-tetraessigsäure (TETA),
1,4,7,10-Tetraazacyclododecan-1,4,7,10-N,N',N",N'''-tetra(methylen)-phosphonsäure (DOTMP)
1,4,7,10-Tetraazacyclotridecan-1,4,7,10-N,N',N",N'''-tetra(methylen)-phosphonsäure,
1,4,7,10-Tetraazacyclotetradecan-1,4,7,10-N,N',N",N'''-tetra(methylen)-phosphonsäure, Diethylentriamin-N,N',N"-pentaessigsäure und isomere Derivative davon, Kryptat[2.2,2], Kryptat[3,2,2], Kryptat[2,2,1] und Mono- und Dibenzoderivate davon, verbrückte Calix[4]arene mit elektronenreichen (Donor-) Gruppen (Hydroxyl, Carboxyl, Ester, Amid, Amin), 1,10-Diaza-4,7,13,16-tetraoxacyclooctadecan-1,10-N,N' bis-essigsäure und
1,10-Diaza-4,7,13,16-tetraoxacyclooctadecan-1,10-N,N'-bis-malonat.

4. Konjugatorsystem nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, dass die Liposomen aktivierte Gruppen in der Membran enthalten, die eine Konjugation von Proteinen oder anderen rezeptoraffinen Molekülen an diese aktivierten Gruppen gestatten.

5. Konjugatorsystem nach Anspruch 4, wobei es sich bei den aktivierten Gruppen um Polyethylenglykol handelt.

6. Konjugatorsystem nach einem der Ansprüche 1 bis 5, dadurch gekennzeichnet, dass die Liposomen an Rezeptorbindungsproteine konjugiert sind.

7. Konjugatorsystem nach Anspruch 6, wobei die Rezeptorbindungsproteine monoklonale oder polyklonale Antikörper oder Antikörperfragmente oder -konstrukte oder Folat sind.

8. Konjungatorsystem nach Anspruch 6, dadurch gekennzeichnet, dass die Liposomen mit Antikörpern der Klasse IgM oder IgG oder Fragmenten oder Konstrukten dieser Antikörperklassen konjugiert sind.

9. Konjugatorsystem nach Anspruch 6, dadurch gekennzeichnet, dass die Liposomen mit Antikörpern der Klasse IgM oder IgG oder Fragmenten oder Konstrukten dieser Antikörperklassen konjugiert sind, wobei die Antikörper, Fragmente oder Konstrukte mit Folat und einem Radionuklid oder einem Gemisch verschiedener Radionuklide markiert sind.

10. Konjugatorsystem nach einem der Ansprüche 1 bis 9, dadurch gekennzeichnet, dass die an die Liposomen konjugierten Antikörper oder Antikörperfragmente oder -konstrukte von der Maus stammend, chimärer Natur oder vom Menschen stammend, monoklonal oder polyklonal sind.

11. Konjugatorsystem nach Anspruch 10, dadurch gekennzeichnet, dass die Antikörper oder Antikörperfragmente oder -konstrukte mit Folat markiert sind, wobei die Antigenbindungsstelle gegen Folatbindungsprotein (FBP) gerichtet ist.

12. Konjugatorsystem nach Anspruch 10, dadurch gekennzeichnet, dass die Antikörper oder Antikörperfragmente oder -konstrukte mit Folat markiert sind, wobei die Antigenbindungsstelle gegen ein von FBP verschiedenes Antigen gerichtet ist.

13. Konjugatorsystem nach einem der Ansprüche 1 bis 12, dadurch gekennzeichnet, dass es sich bei dem Radionuklid um einen schweren alpha-Emitter und/oder ²¹²Pb als Generator des α-Emitters ²¹²Si handelt, ausgewählt unter ²¹¹At, ²¹²Bi, ²¹³Bi, ²¹²Pb, ²²⁵Ac, ²²³Ra, ²²⁴Ra und ²²⁷Th.

14. Konjugatorsystem nach einem der Ansprüche 1 bis 13, dadurch gekennzeichnet, dass das Tochtemuklid und das Muttemuklid ²¹²Bi beziehungsweise ²¹²Pb sind.

15. Verfahren zur Herstellung eines radiomarkierten Konjugatorsystems, dadurch gekennzeichnet, dass man Liposomen mit lonophoren und einem Chelator geeigneter Konzentration stabil mit schweren α-Teilchen-Emittern radiomarkiert, indem man eine Lösung, die ein α-Teilchenstrahlung emittierendes Radionuklid oder ein Gemisch von Radionukliden oder ²¹²Pb als Generator des α-Emitters ²¹²Bi enthält, wobei die schweren α-Teilchen-Emitter ein Atomgewicht von mehr als 150 aufweisen, mit einer Liposomen enthaltenden Lösung mischt und bei gegenüber physiologischer Temperatur erhöhter Temperatur inkubiert, wobei man eine Wanderung des (der) Radionuklids (der Radionuklide) in die Liposomen erhält.

16. Verfahren nach Anspruch 15, dadurch gekennzeichnet, dass der Chelator ausgewählt ist unter 1,4,7,10-Tetraazacyclododecan-1,4,7,10-N,N',N",N'''-tetraessigsäure (DOTA), 1,4,7,10-Tetraazacyclotridecan-1,4,7,10-N,N',N",N'''-tetraessigsäure (TRITA), 1,4,7,10-Tetraazacyclotetradecan-1,4,7,10-N,N',N",N'''-tetraessigsäure (TETA),
1,4,7,10-Tetraazacyclododecan-1,4,7,10-N,N',N",N'''-tetra(methylen)-phosphonsäure (DOTMP)
1,4,7,10-Tetraazacyclotridecan-1,4,7,10-N,N',N",N'''-tetra(methylen)-phosphonsäure,
1,4,7,10-Tetraazacyclotetradecan-1,4,7,10-N,N',N",N'''-tetra(methylen)-phosphonsäure, Diethylentriamin-N,N',N"-pentaessigsäure und isomere Derivative davon, Kryptat[2,2,2], Kryptat[3,2,2], Kryptat[2,2,1] und Mono- und Dibenzoderivate davon, verbrückte Calix[4]arene mit elektronenreichen (Donor-) Gruppen (Hydroxyl, Carboxyl, Ester, Amid, Amin), 1,10-Diaza-4,7,13,16-tetraoxacyclooctadecan-1,10-N,N' bis-essigsäure und
1,10-Diaza-4,7,13,16-tetraoxacyclooctadecan-1,10-N,N'-bis-malonat.

17. Verfahren nach Anspruch 15 oder 16, dadurch gekennzeichnet, dass die Liposomen aktivierte Gruppen in der Membran enthalten, die eine Konjugation von Proteinen oder anderen rezeptoraffinen Molekülen gestatten.

18. Verfahren nach Anspruch 17, dadurch gekennzeichnet, dass es sich bei den aktivierten Gruppen um Polyethylenglykol handelt.

19. Verfahren nach einem der Ansprüche 15 bis 18, dadurch gekennzeichnet, dass die Liposomen an Rezeptorbindungsproteine konjugiert sind.

20. Verfahren nach Anspruch 19, wobei die Rezeptorbindungsproteine monoklonale oder polyklonale Antikörper oder Antikörperfragmente oder -konstrukte oder Folat sind.

21. Verfahren nach Anspruch 19, dadurch gekennzeichnet, dass die Liposomen mit Antikörpern der Klasse IgM oder IgG oder Fragmenten oder Konstrukten dieser Antikörperklassen konjugiert sind.

22. Verfahren nach Anspruch 19, dadurch gekennzeichnet, dass die Liposomen mit Antikörpern der Klasse IgM oder IgG oder Fragmenten oder Konstrukten dieser Antikörperklassen konjugiert sind, wobei die Antikörper mit Folat und einem Radionuklid oder einem Gemisch verschiedener Radionuklide mittels Standardverfahren zur Folat- und Radionuklidmarkierung des Antikörpers markiert sind.

23. Verfahren nach einem der Ansprüche 15 bis 22, dadurch gekennzeichnet, dass die an die Liposomen konjugierten Antikörper oder Antikörperfragmente oder -konstrukte von der Maus stammend, chimärer Natur oder vom Menschen stammend, monoklonal oder polyklonal sind,

24. Verfahren nach Anspruch 23, dadurch gekennzeichnet, dass die Antikörper oder Antikörperfragmente oder -konstrukte mit Folat markiert sind, wobei die Antigenbindungsstelle gegen FBP gerichtet ist.

25. Verfahren nach Anspruch 23, dadurch gekennzeichnet, dass die Antikörper oder Antikörperfragmente oder -konstrukte mit Folat markiert sind, wobei die Antigenbindungsstelle gegen ein von FBP verschiedenes Antigen gerichtet ist.

26. Verfahren nach einem der Ansprüche 15 bis 25, dadurch gekennzeichnet, dass es sich bei dem Radionuklid um einen schweren alpha-Emitter und/oder ²¹²Pb als Generator des α-Emitters ²¹²Bi handelt, ausgewählt unter ²¹¹At, ²¹²Bi, ²¹³Bi, ²¹²Pb, ²²⁵Ac, ²²³Ra, ²²⁴Ra und ²²⁷Th.

27. Verfahren nach einem der Ansprüche 15 bis 26, dadurch gekennzeichnet, dass das Tochternuklid und das Mutternuklid ²¹²Bi beziehungsweise ²¹²Pb sind.

28. Verfahren zur Herstellung des Konjugatorsystems nach einem der Ansprüche 1 bis 14, geeignet zur Injektion oder Infusion in Säuger, einschließlich des Menschen.

29. Verfahren nach Anspruch 28, zur Herstellung einer pharmazeutischen Lösung, die zur Injektion oder Infusion in Säuger, einschließlich des Menschens, durch intravenöse und/oder regionale und/oder intratumorale Verabreichungsweise geeignet ist.

30. Verwendung des Konjugatorsystems nach einem der Ansprüche 1 bis 14 zur Herstellung einer pharmazeutischen Lösung, die zur Injektion oder Infusion in Säuger, einschließlich des Menschen geeignet ist, in Kombination mit einem Radioimmunkonjugat oder verschiedenen Radioimmunkonjugaten und/oder anderen Formen der radiopharmazeutischen Therapie, Chemotherapie, äußerlichen Strahlungsbehandlung oder Chirurgie zur Behandlung bösartiger Tumoren,

31. Verwendung eines Konjugatorsystems nach einem der Ansprüche 1 bis 14 zur Herstellung eines Arzneimittels zur Injektion in menschliche Patienten zu dem Zweck, potentiell therapeutische Strahlung an entartete Zellen abzugeben, die unter Folatbindungsprotein, Östrogenrezeptor und Testosteronrezeptor ausgewählte Rezeptoren exprimieren.

32. Verwendung nach Anspruch 31, wobei die entarteten Zellen abgeleitet sind von bösartigem Gewebe, das unter Gehimkrebs, Lungenkrebs, Gebärmutterhalskrebs, Eierstockkrebs, Brustkrebs, Leukämie, Lymphomen und bösartigen Melanomen ausgewählt ist.

33. Kit zur Herstellung des Konjugatorsystems nach einem der Ansprüche 1 bis 14, dadurch gekennzeichnet, dass es ein Behältnis mit einer Liposomenlösung und ein Behältnis mit einem Radionuklid in einer Lösung, die zur erleichterten Radiomarkierung vermischt werden kann, umfasst.

34. Kit zur Herstellung des Konjugatorsystems nach einem der Ansprüche 1 bis 14, dadurch gekennzeichnet, dass es ein Behältnis mit einer Liposomenlösung und ein zweites Behältnis mit einem Radionuklid in einer Lösung und ein drittes Behältnis mit einem Molekül mit Rezeptoraffinität enthält, die zur erleichterten Radiomarkierung und Markierung mit einem rezeptoraffinen Molekül vermischt werden können.

Revendications

1. Système de conjugaison, caractérisé en ce qu'il comprend des liposomes avec des ionophores et un chélateur situés à l'intérieur des liposomes, les liposomes encapsulent en outre un ou des radionucléides lourds émettant des particules α ou ²¹²Pb en tant générateur pour l'émetteur α²¹²Bi, dans lequel le ou les radionucléides lourds ont un poids atomique supérieur à 150.

2. Système de conjugaison selon la revendication 1. caractérisé en ce que la concentration de chélateur dans les liposomes est appropriée pour conserver des nucléides filles.

3. Système de conjugaison selon l'une quelconque des revendications 1 à 2, caractérisé en ce qu'un chélateur est choisi parmi le groupe comprenant l'acide 1,4,7,10 tétraazacyclododécane-1,4,7,10 N,N',N",N'''-tétraacétique (DOTA),
l'acide 1.4.7.10 tétraazacyclotridécane-1,4,7,10 N,N',N",N'''-tétraacétique (TRITA)
l'acide 1,4,7,10 tétraazacyclotétradécane-1,4,7,10 N,N',N",N'''-tétraacétique (TETA),
l'acide 1,4,7,10 tétraazacyclododécane-1,4,7,10 N,N',N",N'''-tétra(méthylène)phosphonique (DOTMP),
l'acide 1,4,7,10 tétraazacyclotridécane-1,4,7,10 N,N',N",N'''-tétra(méthylène)phosphonique,
l'acide 1,4,7,10 tétraazacyclotétradécane-1,4,7,10 N,N'.N",N"'-tétra(méthylène)phosphonique, l'acide diéthylène triamine N,N',N" pentaacétique et des dérivés isomères de celui-ci, le cryptate [2,2,2], le cryptate [3,2,2], le cryptate [2-2,1] et des dérivés mono et di-benzo de ceux-ci, des calix[4]arènes pontées contenant des groupes (donneurs) riches en électron (hydroxyle, carboxyle, ester, amide, amine),
l'acide 1,10 diaza-4,7,13,16-tétraoxacyclooctadécane 1,10,N,N' bis-acétique, et
le 1,10 diaza-4,7,13,16-tétraoxacyclooctadécane 1,10,N,N' bis-malonate.

4. Système de conjugaison selon l'une quelconque des revendications 1 à 3, caractérisé en ce que les liposomes contiennent des groupes activés dans la membrane permettant la conjugaison des protéines ou d'autres molécules ayant une affinité pour des récepteurs à ces groupes actifs.

5. Système de conjugaison selon la revendication 4, dans lequel lesdits groupes activés sont du polyéthylèneglycol.

6. Système de conjugaison selon l'une quelconque des revendications 1 à 5, caractérisé en ce que les liposomes sont conjugués à des protéines se liant à des récepteurs.

7. Système de conjugaison selon la revendication 6 dans lequel lesdites protéines se liant à des récepteurs sont des anticorps monoclonaux ou polyclonaux, ou des fragments ou des hybrides d'anticorps, ou de l'acide folique.

8. Système de conjugaison selon la revendication 6, caractérisé en ce que les liposomes sont conjugués à des anticorps de classe IgM ou IgG. ou des fragments ou des hybrides de ces classes d'anticorps.

9. Système de conjugaison selon la revendication 6, caractérisé en ce que les liposomes sont conjugués à des anticorps de classe IgM ou IgG. ou des fragments ou des hybrides de ces classes d'anticorps, dans lequel les anticorps, fragments ou hybrides sont marqués avec l'acide folique et un radionucléide ou un mélange de différents radionucléides.

10. Système de conjugaison selon l'une quelconque des revendications 1 à 9, caractérisé en ce que les anticorps ou les fragments ou hybrides d'anticorps conjugués aux liposomes sont murins, chimères ou humains, monoclonaux ou polyclonaux.

11. Système de conjugaison selon la revendication 10, caractérisé en ce que les anticorps ou fragments ou hybrides d'anticorps sont marqués avec de l'acide folique, dans lequel le site anticorps est dirigé vers la protéine de liaison de l'acide folique (FBP).

12. Système de conjugaison selon la revendication 10, caractérisé en ce que les anticorps ou fragments ou hybrides d'anticorps sont marqués avec de l'acide folique, dans lequel le site anticorps est dirigé vers un antigène différent de FBP.

13. Système de conjugaison selon l'une quelconque des revendications 1 à 12, caractérisé en ce que le radionucléide est un émetteur alpha lourd et/ou ²¹²Pb en tant générateur pour l'émetteur α²¹²Bi, choisi parmi ²¹¹At, ²¹²Bi, ²¹³Bi, ²¹²Pb ²²⁵Ac, ²²³Ra, ²²⁴Ra et ²²⁷Th.

14. Système de conjugaison selon l'une quelconque des revendications 1 à 13, caractérisé en ce que le nucléide fille et le nucléide mère sont ²¹²Bi et ²¹²Pb, respectivement.

15. Procédé pour préparer un système de conjugaison radiomarqué, caractérisé en ce que les liposomes avec des ionophores et un chélateur d'une concentration appropriée sont radiomarqués de manière stable avec des émetteurs de particule α lourds, en mélangeant une solution contenant un radionucléide ou un mélange de radionucléide qui émet un rayonnement de particules α ou ²¹²Pb en tant que générateur pour l'émetteur α²¹²Bi, dans laquelle les émetteurs de particule a lourds ont un poids atomique supérieur à 150, avec une solution contenant des liposomes et incubent à une température élevée en comparaison à une température physiologique pour obtenir un transport du ou des radionucléides dans les liposomes.

16. Procédé selon la revendication 15, caractérisé en ce que le chélateur est choisi parmi le groupe comprenant l'acide 1.4.7.1.0 tétraazacyclododécane-1,4,7,10 N,N',N',N'''-tétraacétique (DOTA),
l'acide 1,4,7,10 tétraazacyclotridécane-1,4,7,10 N,N',N",N'''-tétraacétique (TRITA)
l'acide 1,4,7,10 tétraazacyclotétradécane-1,4,7,10 N.N'.N",N"'-tétraacétique (TETA),
l'acide 1,4,7,10 tétraazacyclododécane-1,4,7,10 N,N',N",N'''-tétra(méthylène)phosphonique (DOTMP),
l'acide 1,4,7,10 tétraazacyclotridécane-1,4,7,10 N,N',N",N'''-tétra(méthylène)phosphonique,
l'acide 1,4,7,10 tétraazacyclotétradécane-1,4,7,10 N,N',N",N'''-tétra(méthylène)phosphonique,
l'acide diéthylène triamine N,N',N" pentaacétique et des dérivés isomères de celui-ci, le cryptate [2,2,2], le cryptate [3,2,2], le cryptate [2-2,1] et des dérivés mono et di-benzo de ceux-ci, des calix[4]arènes pontées contenant des groupes (donneurs) riches en électron (hydroxyle, carboxyle, ester, amide, amine),
l'acide 1,10 diaza-4,7,13,16-tétraoxacyclooctadécane 1,10,N,N' bis-acétique, et
le 1,10 diaza-4,7,13,16-tétraoxacyclooctadécane 1,10,N,N' bis-malonate.

17. Procédé selon l'une quelconque des revendications 15 à 16, caractérisé en ce que les liposomes contiennent des groupes activés dans la membrane permettant la conjugaison des protéines ou d'autres molécules ayant une affinité pour des récepteurs.

18. Procédé selon la revendication 17, caractérisé en ce que les groupes activés sont du polyéthylèneglycol.

19. Procédé selon l'une quelconque des revendications 15 à 18, caractérisé en ce que les liposomes sont conjugués à des protéines se liant à des récepteurs.

20. Procédé selon la revendication 19 dans lequel lesdites protéines se liant à des récepteurs ont des anticorps monoclonaux ou polyclonaux, ou des fragments ou des hybrides d'anticorps, ou de l'acide folique.

21. Procédé selon la revendication 19, caractérisé en ce que les liposomes sont conjugués à des anticorps de classe IgM ou IgG, ou des fragments ou des hybrides de ces classes d'anticorps.

22. Procédé selon la revendication 19, caractérisé en ce que les liposomes sont conjugués avec des anticorps de classe IgM ou IgG, ou des fragments ou hybrides de ces classes d'anticorps, dans lequel les anticorps, sont marqués avec l'acide folique et un radionucléide ou un mélange de différents radionucléides, en utilisant des modes opératoires standard pour le marquage par acide folique et radionucléide de l'anticorps.

23. Procédé selon l'une quelconque des revendications 15 à 22. caractérisé en ce qu'un anticorps ou des fragments ou hybrides d'anticorps conjugués aux liposomes sont murins, chimères ou humains, monoclonaux ou polyclonaux.

24. Procédé selon la revendication 23, caractérisé en ce que l'anticorps ou les fragments ou hybrides d'anticorps sont marqués avec l'acide folique, dans lequel le site de liaison de l'antigène est dirigé vers (FBP).

25. Procédé selon la revendication 23, caractérisé en ce que les anticorps ou fragments ou hybrides d'anticorps sont marqués avec l'acide folique, dans lequel le site anticorps est dirigé vers un antigène différent de FBP.

26. Procédé selon l'une quelconque des revendications 15 à 25, caractérisé en ce que le radionucléide est un émetteur alpha lourd ou ²¹²Pb en tant générateur pour l'émetteur α²¹²Bi, choisi parmi ²¹¹At, ²¹²Bi, ²¹³Bi, ²¹²Pb ²²⁵Ac, ²²³Ra, ²²⁴Ra et ²²⁷Th.

27. Procédé selon l'une quelconque des revendications 15 à 26, caractérisé en ce que le nucléide fille et le nucléide mère sont ²¹²Bi et ²¹²Pb, respectivement.

28. Procédé pour la fabrication du système de conjugaison selon l'une quelconque des revendications 1 à 14, approprié pour l'injection ou la perfusion à des mammifères, y compris des humains.

29. Procédé selon la revendication 28, pour préparer une solution pharmaceutique appropriée pour l'injection ou la perfusion à des mammifères, y compris des humains, par voie intraveineuse et/ou régionale, et/ou intratumorale d'administration.

30. Utilisation du système de conjugaison selon l'une quelconque des revendications 1 à 14 pour préparer une solution pharmaceutique appropriée pour une injection ou un perfusion à des mammifères y compris des humains en combinaison avec un radioimmunoconjugué ou plusieurs radioimmunoconjugués et/ou d'autres formes de thérapie radiopharmaceutique, chimiothérapie, radiothérapie externe ou chirurgie pour traiter des affections malignes.

31. Utilisation d'un système de conjugaison selon l'une quelconque des revendications 1 à 14 pour la fabrication d'un médicament pour l'injection à des sujets humains à des fins de délivrance d'un rayonnement potentiellement thérapeutique à des cellules malignes exprimant des récepteurs choisis parmi la protéine de liaison de l'acide folique, un récepteur de l'oestrogène et un récepteur de la testostérone.

32. Utilisation selon la revendication 31 dans laquelle lesdites cellules malignes sont dérivées de tissu malin choisi parmi le cancer du cerveau, le cancer du poumon, le cancer cervical, le cancer des ovaires, le cancer du sein, une leucémie, un lymphome et un mélanome malin.

33. Kit pour la préparation du système de conjugaison selon l'une quelconque des revendications 1 à 14, caractérisé en ce qu'il comprend un flacon contenant une solution de liposomes et un flacon contenant un radionucléide dans une solution qui peuvent être mélangés pour faciliter le radiomarquage.

34. Kit pour la préparation du système de conjugaison selon l'une quelconque des revendications 1 à 14, caractérisé en ce qu'il comprend un flacon contenant une solution de liposomes et un second flacon contenant un radionucléide dans une solution et un troisième flacon contenant une molécule avec une affinité pour un récepteur, qui peuvent être mélangés pour faciliter le radiomarquage et le marquage avec une molécule ayant une affinité pour un récepteur.

Drawing