Stable formulations comprising 225-actinium labeled complexes and methods for preparing the same

Abstract

The present invention provides a pharmaceutical composition comprising a radiolabeled complex comprising a radionuclide and a targeting moiety linked to a chelating moiety, and a stabilizer against radiolytic degradation comprising sodium acetate and ethanol. The pharmaceutical composition of the present invention provides high stability against radiolytic degradation. The present invention also provides a method for preparing such a pharmaceutical composition.

Description

[0001] GRAF VON STOSCH

[0002] PATENTANWALTSGESELLSCHAFT MBH

[0003] Our Ref. Date

[0004] IT02P040W01 April 15, 2025

[0005] Applicant

[0006] ITM Isotope Technologies Munich SE, Garching, Germany

[0007] 5 STABLE FORMULATIONS COMPRISING 225-ACTINIUM LABELED COMPLEXES AND METHODS FOR PREPARING THE SAME

[0008] The present invention relates to the field of radiopharmaceutical formulations, in particular to formulations ensuring the stability of radionuclide complexes and to methods of preparing such formulations.

[0009] Radiopharmaceuticals are drugs, which contain radioactive isotopes (radionuclides). Radiopharmaceuticals can be used to treat various conditions, including cancers, blood

[0010] 15 disorders and hyperthyroidism. In radionuclide therapy of cancer, a molecule labeled with a radionuclide is used to deliver a toxic level of radiation to disease sites. Accordingly, the molecule is used to "target" the disease site, e.g. specific cancer cells. Accordingly, the radionuclide complex combines the specificity of cancer cell targeting with the known antitumor effects of ionizing radiation. Thereby, not only the primary tumor site, but also its metastases can be targeted. The choice of the molecule that carries the radiation to the tumor is usually determined by its selectivity and affinity to the tumor's target structures, such as antigens or receptors. Even if a target structure is not selective for a certain kind of cancer, overexpressed target structures are of interest, because they allow the delivery of the radionuclide complex after its systemic administration in high concentration to those

[0011] 25 (overexpressing) target cells while leaving other cells (with no or minor expression only) essentially unaffected.

[0012] Radionuclides are usually linked to the targeting moiety through a chelating moiety. Thereby, strong complexes with the metal ion of the radionuclide can be formed. The radioactive decay of the radionuclides can cause significant damage to cancer cells by releasing high energy electrons, positrons or alpha particles as well as gamma rays at the target site.

[0013] However, radioactive decay of the radionuclide occurs constantly, including during manufacturing and storage of the radionuclide complex. The high energy emitted in radioactive decay can induce the cleavage of the chemical bonds of the radionuclide complex, thereby leading to partial destruction of the drug due to its radioactivity. The radiolytic degradation of the targeting moiety of the radionuclide complex may result in a reduced specificity of the radionuclide complex, thereby leading to a decrease in its efficacy and / or to an increase in undesired side effects.

[0014] With a half-life of 9.92 days and a decay chain that emits four high energy alpha particles, Actinium-225 (225Ac) is one of the most promising radionuclides for targeted alpha therapy.

[0015] The currently most common radiolabeling strategies of distinct precursor compounds with Ac- 225 described in the literature usually involve using a TRIS buffer (Tris(hydroxymethyl)aminomethane) at pH 9 or an ascorbate buffer at pH 4-6 and heating at 90-95°C for 15 to 45 min. The labeling efficiency is reported to be 90-95% (Hooljman E L, et al. Development of [225Ac]-PSMA-l&T for Targeted Alpha Therapy According to GMP Guidelines for Treatment of mCRPC. Pharmaceutics 2021. 13, 715; Morgenstern A et al. Bismuth-213 and Actinium-225 - Generator Performance and Evolving Therapeutic Applications of Two Generator-Derived Alpha-Emitting Radreisotopes. Current Radiopharmaceuticals, 2012, 5, 221 -227; Pretze M et al. Ac-EAZY! Towards GMP-Compliant Module Syntheses of 225Ar-l.abeled Peptides for Clinical Application. Pharmaceuticals 2021 , 14, 652). Even under optimized conditions, up to 2% uncomplexed Ac-225 remains in the formulation containing the radionuclide complex (Hooljman et al., 2021 , supra}. The indicated amounts of uncomplexed Ac-225 either require further purification of the pharmaceutical product (Hooljman etaL, 2021 , supra; Pretze et al., 2021 ). Another possibility is the addition of weak complexing agents such as DTPA or ETDA to the formulation in order to bind radiotoxic unconjugated Ac-225 and rapidly eliminate it from the organism (Hooljman et al., 2021 , supra; Pretze et al., 2021 ). However, it should be noted that the weak chelators DTPA and EDTA complex Ac-225 only insufficiently strongly and an undesired accumulation of Ac-225 in healthy tissue can only be guaranteed with a low degree of reliability (Deal K. A. et a!., Improved in Vivo Stability of Actinium-ZIS Macrocyclic Complexes. J. Med. Chem. 1999. 42, 2988-2992). Thus, no labeling condition for [225Ac]Ac-labeled substances has been described in the current literature that guarantees a radiochemical yield of > 99 %.

[0016] After radiolabeling the precursor compounds, the stability of radiopharmaceuticals is usually restricted to a few hours or days only. This results in various challenges regarding the manufacture, storage and transport of radiopharmaceuticals. Therefore, for the application of radiopharmaceuticals only a small window is available after manufacturing.

[0017] In order to reduce this problem, usually antioxidants, such as gentisic acid, ethanol, ascorbic acid and methionine, are added to the formulation of the radionuclide complex. However, in particular for peptides labelled with177Lu, such as DOTATOC (edotreotide) and DOTATATE (oxodotreotide), often complex mixtures of antioxidants or specific time points of their addition are required to obtain the desired effect over an acceptable period of time. For example, Maus et al. reports the addition of ascorbic acid after radiolabeling and purification of f177Lu] Lu-DOT AT ATE (Stephan Maus et al. Aspects on radiolabeling of 177Lu-DOTA-TATE: After C18 purification re-addition of ascorbic acid is required to maintain radiochemical purity, International Journal of Diagnostic Imaging, 2014, Vol. 1 , No. 1 ).

[0018] US patent 10,756,278 B2 requires a complex mixture of gentisic acid, ascorbic acid, and EDTA after radiolabeling to obtain the desired stability against radiolysis of 95% at 72 hours after synthesis. De Blois et al. and Breeman et al. even suggest the addition of a mixture of 50 mM ascorbic acid, 10% (v / v) ethanol and 50 mM L-methionine (Erik de Blois et al. Effectiveness of Quenchers to Reduce Radiolysis of111ln- or177Lu-labelled Methionine- Containing Regulatory Peptides. Maintaining Radiochemical Purity as Measured by HPLC. Curr Top Med Chem. 2012;12(23):2677-85; Wouter A. P. Breeman; Practical Aspects of labeling DTPA- and DOTA-Peptides with90Y,111ln,177Lu, and68Ga for Peptide- Receptor Scintigraphy and Peptide- Receptor Radionuclide Therapy in Preclinical and Clinical Applications; The University of New Mexico Health Sciences Center, VOLUME 16, LESSON 5: 1 1 / 16 / 2012). According to these reports, for177Lu-labelled peptides, the stabilizer, or the second or third stabilizing component, respectively, is added only after radiolabeling in acetate or HEPES buffer.

[0019] The strength of radiolysis also depends in particular on the amount of chemical precursor (peptide) used, the radioactivity concentration and the type of antioxidant, as well as their concentrations. In addition to radiolysis stability, particular attention must also be paid to pH in the case of parenterally administered radiopharmaceuticals. The composition of a multicomponent formulation for the stabilization of therapeutic radiopharmaceuticals is a complex matter for this reason. Alpha-emitting emitters are particularly predestined for radiation-induced damage to radiopharmaceuticals. The energy of alpha radiation is about 4- 5 MeV, which is an order of magnitude higher than that of beta radiation. Alpha radiation is therefore not only significantly more energy intensive, but also emits this energy in a much smaller radius from the decay origin due to its high interaction with matter. The only alphaemitting radiopharmaceutical approved to date, [223Ra]RaCb, is chemically inert and - due to its pharmaceutical formulation as a dissolved salt - is not affected by radiolysis.

[0020] In contrast, antibody or peptide conjugates of DOTA, DOTAGA or Macropa with Ac-225, Pb- 212 or other alpha emitters are vulnerable to radiolytic degradation, and the reported shelf life of these drugs is limited to only a few hours (Hooijman et al., Development of [225Ac]Ac- PSMA-I&T for Targeted Alpha Therapy According to GMP Guidelines for Treatment of mCRPC. Pharmaceutics 2021 , 13, 715).

[0021] The low stability results in a short shelf life of Ac-225 radiopharmaceuticals, which is a major obstacle for centralized production. Not least due to inadequate radioanalytics of Ac-225 labeled compounds, but also due to the strong radiolytic properties of alpha emitters, the purity of Ac-225 radiopharmaceuticals is currently reported to be only >90% for many human applications (Pretze et al., Ac-EAZY! Towards GMP-Compliant Module Syntheses of 225Ac- Labeled Peptides for Clinical Application. Pharmaceuticals 2021 , 14, 652). This purity is significantly lower than the current quality of other therapeutic radiopharmaceuticals, such as that of177Lu-DOTATOC,177Lu-DOTATATE (Lutathera), or177Lu-PSMA-617.

[0022] However, in the current literature, no formulation for [225Ac]Ac-labeled compounds has yet been described that ensures stability over at least 72 h with a purity of > 94% and uncomplexed "free"225Ac3+< 1 %.

[0023] US patent application US 2023 / 0144360 A1 describes a liquid radiopharmaceutical composition targeting the somatostatin receptor comprising (a)225Ac-DOTA-TATE or a pharmaceutically acceptable salt thereof, (b) sodium ascorbate at a concentration of 40 mM to 250 mM, (c) diethylentriamin pentaacetate (DTPA), and (d) a saline solution as an aqueous vehicle. According to US 2023 / 0144360 A1 , the radiopharmaceutical composition disclosed therein retains at least 90% of the225Ac content as225Ac-DOTATATE after 120 hours at 20- 25°C.

[0024] In view of the above, it is the object of the present invention to overcome the drawbacks outlined above and to provide a pharmaceutical composition including a radionuclide complex, in particular a225Ac labeled complex, which ensures increased purity and stability of the radionuclide complex over an increased period of time. It is further object of the present invention to provide a rapid and straightforward225Ac radiolabeling method as well as a method for preparing a pharmaceutical composition which provides for a radiolysis-stable formulation containing as few components as possible.

[0025] This object is achieved by means of the subject-matter set out below and in the appended claims.

[0026] Although the present invention is described in detail below, it is to be understood that this invention is not limited to the particular methodologies, protocols and reagents described herein as these may vary. It is also to be understood that the terminology used herein is not intended to limit the scope of the present invention which will be limited only by the appended claims. Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art.

[0027] In the following, the elements of the present invention will be described. These elements are listed with specific embodiments, however, it should be understood that they may be combined in any manner and in any number to create additional embodiments. The variously described examples and preferred embodiments should not be construed to limit the present invention to only the explicitly described embodiments. This description should be understood to support and encompass embodiments which combine the explicitly described embodiments with any number of the disclosed and / or preferred elements. Furthermore, any permutations and combinations of all described elements in this application should be considered disclosed by the description of the present application unless the context indicates otherwise. Throughout this specification and the claims which follow, unless the context requires otherwise, the term "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated member, integer or step but not the exclusion of any other non-stated member, integer or step. The term "consist of" is a particular embodiment of the term "comprise", wherein any other non-stated member, integer or step is excluded. In the context of the present invention, the term "comprise" encompasses the term "consist of". The term "comprising" thus encompasses "including" as well as "consisting" e.g., a composition "comprising" X may consist exclusively of X or may include something additional e.g., X + Y.

[0028] The terms "a" and "an" and "the" and similar reference used in the context of describing the invention (especially in the context of the claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.

[0029] The word "substantially" does not exclude "completely" e.g., a composition which is "substantially free" from Y may be completely free from Y. Where necessary, the word "substantially" may be omitted from the definition of the invention.

[0030] The term "about" in relation to a numerical value x means x ± 20%, preferably x ± 10%, more preferably x ± 5%, even more preferably x ± 2% and still more preferably x ± 1 %.

[0031] Pharmaceutical composition

[0032] In a first aspect the present invention provides a pharmaceutical composition comprising:

[0033] (a) a radiolabeled complex comprising (i) an225Ac (Actinium-225) radionuclide, and (ii) a targeting moiety targeting prostate specific membrane antigen (PSMA) or av03 integrin covalently linked to a chelating moiety; and

[0034] (b) a stabilizer against radiolytic degradation, wherein the stabilizer comprises sodium acetate (NaOAc) and ethanol (EtOH).

[0035] The present inventors have surprisingly found that such a formulation of the radionuclide complex ensures increased radiochemical purity and stability of the radionuclide complex over an increased period of time, in particular at least 72 hours when stored at room temperature (RT). Due to the longer stability of 72 h with consistently high quality, central production with subsequent distribution of the drug to the treatment centers can be ensured.

[0036] Interestingly, the increased stability / shelf life can be achieved with a formulation containing fewer components as compared to prior art formulations for radionuclide complexes. In particular, sodium acetate (NaOAc) used as a stabilizer of the formulation may also serve as buffer for radiolabeling resulting in high radiolabeling yields, such that complicated mixtures can be avoided. Additionally, sodium acetate (NaOAc) used as a stabilizer of the formulation may serve as pH-modulator / buffer (in particular in a pH-range acceptable for parenteral injections, e.g. pH 6 - 8), which further avoids complicated mixtures. In addition, purification of the labeled end product, as well as the addition of weak complexing agents in the formulation, can be omitted.

[0037] Radiolabeled complex

[0038] The radiolabeled complex of the pharmaceutical composition according to the present invention comprises (i) an225Ac (Actinium-225) radionuclide, and (ii) a targeting moiety targeting prostate specific membrane antigen (PSMA) or av03 integrin, wherein the targeting moiety is covalently linked to a chelating moiety.

[0039] In the radiolabeled complex, the radionuclide metal ion225Ac usually forms a non-covalent bond with functional groups of the chelating moiety, e.g. amine or carboxylic acid functional groups. Typically, the chelating moiety has at least two such complexing functional groups to be able to form a chelate complex. As used herein, the term "chelating moiety" (also referred to as "chelator") refers to polydentate (multiple bonded) ligands capable of forming two or more separate coordinate bonds with ^coordinating") a central (metal) ion, in particular the radionuclide metal ion. Specifically, such molecules or molecules sharing one electron pair may also be referred to as "Lewis bases". The central (metal) ion is usually coordinated by two or more electron pairs to the chelating moiety. The terms, "bidentate chelating moiety", "tridentate chelating moiety", and "tetradentate chelating moiety" are known in the art and refer to chelating moieties having two, three, and four electron pairs, respectively, which are readily available for simultaneous donation to a metal ion coordinated by the chelating moiety. Usually, the electron pairs of a chelating moiety forms coordinate bonds with a single central (metal) ion; however, in certain examples, a chelating moiety may form coordinate bonds with more than one metal ion, with a variety of binding modes being possible.

[0040] The terms "coordinating" and "coordination" refer to an interaction in which one multielectron pair donor coordi natively bonds (is "coordinated") to, i.e. shares two or more unshared pairs of electrons with, one central (metal) ion.

[0041] The chelator or chelating moiety is preferably a macrocyclic bifunctional chelator having a metal chelating group at one end and a reactive functional group at the other end, which is capable to bind to other moieties, e.g. peptides. Preferably, the chelating moiety may be selected such that the chelating moiety forms a square bi-pyramidal complex for complexing the radionuclide. In another embodiment, the chelating moiety does not from a planar or a square planar complex.

[0042] The chelating moiety may be selected based on its ability to coordinate the desired central (metal) ion, in particular Actinium-225. Thus, any chelating moiety which is capable of complexing225Ac may suitably be used in the radiolabeled complex according to the present invention.

[0043] Thus, without being limited thereto, the chelating moiety may e.g. be selected from 1 ,4,7,10- tetraazacyclododecane-1 ,4,7,10-tetraacetic acid (DOTA), and derivatives thereof, 2-(4,7,10- tris(carboxymethyl)-1 ,4,7,10-tetraazacyclododecan-1 -yl)-pentanedioic acid (DOTAGA), and derivatives thereof (e.g., DOTAGA-Anhydrid), N,N'-bis[(6-Carboxy-2-pyridil)methyl]-4,13- diaza-18-krone-6 (H2-Macropa), and derivatives thereof (H2-Macropa-NCS, H2-BZ-Macropa, H2-BZ2-Macropa, H2-BZ-Macropa-NSC), Crown and derivatives thereof, and H4py4pa.

[0044] Accordingly, the chelating moiety may be characterized by one of the following Formulae (1 a)-(1 k): H2-BZ-Macropa (1 g) H2-BZ2-Macropa (1 h)

[0045] H4py4pa (1 k)

[0046] Preferably, the chelating moiety is selected from DOT A, DOTAGA, Macropa and Crown, or from a derivative thereof. Particularly preferably, the chelating moiety is DOTA (which may be characterized by Formula (1 a)) or derivatives thereof. DOTA may effectively form complexes with225Ac for both imaging and therapeutic purposes, i.e. as a theragnostic agent.

[0047] The radiolabeled complex comprising (i) the radionuclide225Ac and (ii) the targeting moiety targeting PSMA or avp3, linked to a chelating moiety is preferably formed in a radiolabeling method as described herein below.

[0048] Targeting moiety

[0049] As used herein, the term "targeting moiety" refers to a molecule, which is able to bind (specifically) to a "target", such as a target cell (e.g., a cancer cell). In particular, the "target" may be a molecule located at the cell surface of a target cell (e.g., a cancer cell). Such a surface molecule, to which the targeting moiety binds, may be, for example, a receptor located at the surface of the cell. In particular, the surface molecule is specific for or overexpressed by the target cell (e.g., a cell "marker"). The targeting moiety may bind, for example, to a disease (e.g., cancer) marker (which is expressed / located at the surface of the cell involved in the disease, e.g. a cancer cell). Thereby, the targeting moiety can guide the radionuclide specifically to the cell involved in the disease, e.g. a cancer cell. Accordingly, the targeting moiety is usually selected depending on the disease to be treated or diagnosed. In the context of a disease, e.g. cancer, the cells to be targeted with the radiolabeled complex, e.g. cancer cells, usually express specific molecules (or overexpress specific molecules), which may serve as "target" (surface molecule). The targeting moiety is typically selected such that it binds to said "targets" (surface molecules and, thus, target cells, e.g. cancer cells). The binding of the targeting moiety to the surface molecule may be reversible or irreversible. Preferably, the targeting moiety is selected from peptides, peptidomimetics, antibodies, antibody fragments, and antibody mimetics. In some embodiments, the targeting moiety is a peptide or polypeptide or a modified peptide or polypeptide.

[0050] In the radiolabeled complex of the pharmaceutical composition according to the present invention, the targeting moiety targets PSMA or av03 integrin, and thus is able to bind to PSMA or av03 integrin.

[0051] PSMA-targeting compounds

[0052] In some embodiments, the radiolabeled complex of the pharmaceutical composition according to the present invention comprises a targeting moiety which targets PSMA.

[0053] The human Prostate-specific membrane antigen (PSMA) (also referred to as glutamate carboxypeptidase II (GCPII), folate hydrolase 1, folypoly-gamma-glutamate carboxypeptidase (FGCP), and N-acetylated-alpha-linked acidic dipeptidase I (NAALADase I)) is a type II transmembrane zinc metal lopeptidase. The term "Human Prostate-specific membrane antigen" or "PSMA" as used herein preferably refers to the protein encoded by the human FOLH1 gene. More preferably, the term refers to the protein as characterized under UniProt Acc. No. Q04609 (entry version 186, last modified May 10, 2017), or functional variants, isoforms, fragments or (post-translational ly or otherwise modified) derivatives thereof. The prostate-specific membrane antigen (PSMA) is overexpressed in the majority of prostate cancer cases (Silver, D. A.; Pellicer, I.; Fair, W. R.; Heston, W. D.; Cordon-Cardo, C. Prostatespecific membrane antigen expression in normal and malignant human tissues. CHn Cancer Res 1997, 3, (1 ), 81 -5; Cunha, A. C.; Weigle, B.; Kiessling, A.; Bachmann, M.; Rieber, E. P. Tissue-specificity of prostate specific antigens: comparative analysis of transcript levels in prostate and non-prostatic tissues. Cancer Lett 2006, 236, (2), 229-38). It emerged, therefore, as a promising target for nuclear imaging and radionuclide therapy of metastatic castrationresistant prostate cancer (mCRPC) (Bouchelouche, K.; Choyke, P. L. Prostate-specific membrane antigen positron emission tomography in prostate cancer: a step toward personalized medicine. Curr Opin Oncol 2016, 28, (3), 216-21 ; Haberkorn, U.; Eder, M.; Kopka, K.; Babich, J. W.; Eisenhut, M. New strategies in prostate cancer: prostate-specific membrane antigen (PSMA) ligands for diagnosis and therapy. CHn Cancer Res 2016, 22, (1 ), 9-15; Eiber, M.; Fendler, W. P.; Rowe, S. P.; Calais, J.; Hofman, M. S.; Maurer, T.; Schwarzenboeck, S. M.; Kratowchil, C.; Herrmann, K.; Giesel, F. L. Prostate-specific membrane antigen ligands for imaging and therapy. J Nud Med2(Y\ 7, 58, (Suppl 2), 67S-76S). PSMA is (i) mainly restricted to the prostate (although is also detected in lower amounts in the neovasculature of numerous other solid tumors, including bladder, pancreas, lung, and kidney cancers, but not in normal vasculature), (ii) abundantly expressed as protein at all stages of prostate cancer (in amounts of up to 106PSMA molecules per cancer cell) (iii) presented at the cell surface but not shed into the circulation, and (iv) associated with enzymatic or signaling activity. Moreover, PSMA expression is further up-regulated in poorly differentiated, androgen-insensitive or metastatic cancers and the expression usually correlates with disease progression.

[0054] The unique expression of PSMA makes it an important marker of prostate cancer (and a few other cancers as well). Furthermore, PSMA represents a large extracellular target for imaging agents. PSMA is internalized after ligand binding and, thus, it is not only an excellent target for targeted radionuclide therapy (using particle-emitting radionuclides) but also for other therapeutic strategies including the tumor cell-specific delivery of immunotoxins, retargeting of immune cells, pro-drug activation, PSMA vaccines, and plasmid DNA and adenoviral immunizations. Because of low expression levels in healthy tissue, PSMA has additionally the potential for high-dose therapy, with minimized side effects.

[0055] The PSMA-binding targeting moiety of the radiolabeled complex comprised in the pharmaceutical composition according to the present invention may generally be a binding entity capable of selectively (and optionally irreversibly) binding to (human) Prostate-Specific Membrane Antigen (e.g., as described in Chang Rev Urol. 2004; 6(Suppl 10): S13-S18). The PSMA targeting moiety is preferably chosen by its ability to confer selective affinity towards PSMA. Preferred PSMA binding moieties are described in WO 2013 / 022797 A1 , WO 2015 / 055318 A1 and EP 2862857 A1 , which are incorporated herein by reference in their entirety.

[0056] Accordingly, the PSMA targeting moiety may preferably be characterized by General Formula (2): wherein

[0057] X is selected from O, N, S or P,

[0058] R3, R4and R5are each independently selected from -COH, -CO2H, -SO2H, -SO3H, - SO4H, -PO2H, -PO3H, -PO4H2, -C(O)-(Ci-C10)alkyl, -C(O)-O(Ci-Cw)alkyl, -C(O)-NHR8, or - C(O)-NR8R9,wherein R8and R9are each independently selected from H, bond, (Cl - C10)alkylene, F, Cl, Br, I, C(O), C(S), -C(S)-NH-benzyl-, -C(O)-NH-benzyl, -C(O)-(Ci- C10)alkylene, -(CH2)P-NH, -(CH2)p-(Ci-C10)alkyene, -(CH2)p-NH-C(O)-(CH2)q, -(CHrCH2)t-NH- C(O)-(CH2)P, -(CH2)P-CO-COH, -(CH2)P-CO-CO2H, -(CH2)p-C(O)NH-C[(CH2)q-COH]3, - C[(CH2)P-COH]3, -(CH2)p-C(O)NH-C[(CH2)q-CO2H]3, -C[(CH2)P-CO2H]3or -(CH2)P-(C5- Ci4)heteroaryl, and b, p, q, r, t is each independently an integer selected from 0, 1 , 2, 3, 4, 5, 6, 7, 8, 9, or 10.

[0059] In preferred PSMA targeting moieties, b may be an integer selected from 1 , 2, 3, 4 or 5, R3, R4and R5may each be CO2H, X may be O.

[0060] Examples of small-molecule PSMA targeting agents capable of binding to the extracellular domain of PSMA include, but are not limited to: N-[N-[(S)-1 ,3-dicarboxypropyl]carbamoyl]- S-[1 1 C]methyl-l-cysteine (DCFBC), several urea-based peptidomimetic PSMA-inhibitors as described in Bouchelouche et al. Discov Med. 2010 Jan; 9(44): 55-61 ), including MIP-1095 (Hillier et al. Cancer Res. 2009 Sep 1 ;69(17):6932-40).

[0061] Kelly et al. (Dual-Target Binding Ligands with Modulated Pharmacokinetics for Endoradiotherapy of Prostate Cancer. J Nucl Med. 2017 Sep;58(9):1442-1449. doi: 10.2967 / jnumed.1 16.188722) evaluated agents exhibiting affinity for both PSMA and for human serum albumin (HSA). The ligands developed by Kelly et al. comprise a p- (iodophenyl)butyric acid entity for HSA binding and an urea-based PSMA binding entity. In the compounds developed by Kelly et al., radiotherapeutic iodine (l31l) is covalently attached to the HSA binding moiety, which is in turn directly connected to the PSMA binding entity via a hydrocarbyl chain.

[0062] As mentioned above, the targeting moiety and the chelating moiety usually form together conjugates or molecules (suitable for radiolabeling). Various such conjugates / molecules are known in the art. Preferred conjugates comprising a chelating moiety and a targeting moiety, which is able to bind to PSMA, are disclosed in WO 2018 / 215627 A1 , which is also incorporated herein by reference.

[0063] Preferred examples of conjugates comprising a targeting moiety and a chelating moiety include PSMA-617 developed by Benesova et al 0NM 2015, 56: 914-920 and EP 2862 857 A1 ) according to Formula (3) below, PSMA-I&T (Weineisen M et al., J Nucl Med. 2015; 56:1169-1 176) according to Formula (4) below; Ibu-PSMA according to Formula (5) below; Ibu-DAB-PSMA according to Formula (6) below, Ibu-N-PSMA according to Formula (7) below; and Ibu-Da-PSMA according to Formula (8) below: Ibu-DAB-PSMA: Ibu-Da-PSMA:

[0064] Accordingly, the radiolabeled complex (comprising the radionuclide, and the targeting moiety linked to the chelating moiety) of the pharmaceutical composition according to the present invention may be obtained from a compound represented by above formulae (3) to (8), and is preferably selected from225Ac-lbu-DAB-PSMA,22SAc-PSMA-617, and225Ac-PSMA-l&T, in particular225Ac-lbu-DAB-PSMA, more specifically (5)-lbu-DAB-PSMA. All of them contain a DOTA chelator and may also e.g. be designated as225Ac-DOTA-lbu-DAB-PSMA,225Ac- DOTA-PSMA-617, and225Ac-DOTA-PSMA-l&T, respectively.

[0065] The concentration of the radiolabeled complex (comprising the radionuclide, and the targeting moiety linked to the chelating moiety) in the pharmaceutical composition, preferably225Ac- Ibu-DAB-PSMA,225Ac-PSMA-617, and225Ac-PSMA-l&T, is preferably in a range from 10 to 150 nmol / mL, preferably 10 to 130 nmol / mL. The concentration of the precursor (the targeting moiety linked to the chelating moiety) in the pharmaceutical composition is preferably in the range from 20 to 200 pg / mL, in particular 30 to 160 pg / mL.

[0066] Further, in the pharmaceutical composition, the225Ac radionuclide is preferably present at a concentration providing volumetric radioactivity of 0.2 to 4 MBq / mL or 0.4 to 4.0 MBq / mL, preferably 1.0 to 4.0 MBq / mL. In another embodiment, the225Ac radionuclide is preferably present at a concentration providing volumetric radioactivity of 0.2 to 2 MBq / mL, more preferably 0.2 to 1 .0 MBq / mL, and most preferably 0.3 to 0.8 MBq / mL.

[0067] Integrin-targeting compounds

[0068] In some embodiments, the radiolabeled complex of the pharmaceutical composition according to the present invention comprises a targeting moiety which targets an integrin, in particular an aV / ?3 integrin.

[0069] Integrins are heterodimeric glycoproteins consisting of an a- and P-subunit. There are 24 different combinations of the eight p-units and the eighteen a-units known. The integrins mediate cell-cell and cell-matrix interactions and transduce signals across the plasma membrane via insight-out and outside-in signaling. Some of the integrins play an important role during migration of endothelial as well as tumor cells during tumor-induced angiogenesis and tumor metastasis. Angiogenesis, the formation of new blood vessels out of the preexisting vasculature, is a critical step in the development and dissemination of various human tumors. A variety of therapeutic strategies in oncology are focused on the inhibition of tumor-induced angiogenesis. Concerning the integrins, significant attention has been paid to the role of integrin aV / ?3 and aV / ?5, as they are prominent on proliferating vascular endothelial cells. Thus, one of the most prominent target structures used for the development of radiopharmaceuticals for imaging angiogenesis is the integrin aV / ?3.

[0070] Tumor-induced angiogenesis can be blocked in vivo by antagonizing the avp3 integrin with small peptides containing the Arg-Gly-Asp (RGD) amino acid sequence. This tripeptidic sequence, naturally present in extracellular matrix proteins, is the primary binding site of the avP3 integrin. Because of selective expression of avp3 integrin in tumors, radiolabeled RGD peptides are attractive candidates for avp3 integrin targeting in tumors. Over the last decade, many radiolabeled linear and cyclic RGD peptides have been evaluated as radiotracers for imaging tumors by SPECT or PET, as well as therapeutic agents.

[0071] To allow radiolabeling with225Ac, a chelating moiety conjugated to the peptide is preferably used. As a chelating moiety, any suitable chelating moiety, e.g. as specified above, can be used, wherein DOTA, DOTAGA, and Macropa are preferred. A preferred example of a conjugate comprising the RGD peptide as the targeting moiety and DOTA as the chelating moiety is DOTA-RGD according to formula (9):

[0072] DOTA-RGD:

[0073] In a preferred embodiment, the radiolabeled complex comprised in the pharmaceutical composition according to the present invention comprises (i) the radionuclide (Ac-225) and (ii) DOTA-RGD. Thus, in a preferred embodiment, the radiolabeled complex (comprising the radionuclide, the targeting moiety and the chelating moiety) is225Ac-DOTA-RGD.

[0074] The concentration of the aV / ?3 targeting moiety linked to the chelating agent in the pharmaceutical composition is preferably in a range from 10 to 150 nmol / mL, preferably 10 to 130 nmol / mL.

[0075] Further, in the pharmaceutical composition, the225Ac radionuclide is preferably present at a concentration providing volumetric radioactivity of 0.2 to 4 MBq / mL or 0.4 to 4.0 MBq / mL, preferably 1.0 to 4.0 MBq / mL, or, preferably 0.2 to 2 MBq / mL, more preferably 0.2 to 1 .0 MBq / mL, and more preferably 0.3 to 0.8 MBq / mL and most preferably 0.35 to 0.45 MBq / mL. Stabilizer

[0076] In order to provide stability against radiolytic degradation, the pharmaceutical composition comprises a stabilizer. As used herein, the term "stabilizer" (against radiolytic degradation) refers to an agent which protects organic molecules against radiolytic degradation. In particular, the stabilizer may be able to scavenge radicals, which may be generated, for example, when the radionuclide emits a gamma ray and the gamma ray cleaves a bond between the atoms of organic molecules, thereby forming radicals. Therefore, the stabilizer can avoid or reduce that radicals undergo other chemical reactions, which might lead to undesired, potentially ineffective or even toxic molecules.

[0077] The stabilizer comprised in the pharmaceutical composition according to the present invention comprises sodium acetate (NaOAc) and ethanol. As shown in the appended examples, such a formulation not only decreases the complexity of the composition (and its preparation), but surprisingly a high stability of the radiolabeled complex can be obtained.

[0078] Preferably, the concentration of sodium acetate in the pharmaceutical composition according to the present invention is in the range from 7 to 100 mg / mL or 9 mg / mL to 100 mg / mL, in particular in the range of 7 or 9 mg / mL to 15 or 20 mg / mL, e.g. 7 mg / mL to 15 mg / mL, more preferably in the range of 7 or 9 to 12mg / mL, e.g. 7 mg / mL to 12 mg / mL. Examplary ranges are 20 mg / mL to 90 mg / mL, 30 mg / mL to 80 mg / mL, 40 mg / mL to 70 mg / mL, or 50 mg / mL to 60 mg / mL. Preferably, the pharmaceutical composition according to the present invention contains 9.8 mg / mL to 98.4 mg / mL sodium acetate, which corresponds to 2.7 mg / MBq to 6.6 mg / MBq.

[0079] As shown in the Examples below, a formulation comprising sodium acetate in a concentration as defined above, exhibits high purity and long-term stability of the radiolabeled complex.

[0080] Moreover, the stabilizer of the pharmaceutical composition according to the present invention also comprises ethanol. In a preferred embodiment, the concentration of ethanol in the pharmaceutical composition according to the present invention is in a range from 1 to 30 % (vol / vol), more preferably 2 to 20% (vol / vol), more preferably 2 to 7 vol.%, even more preferably 3 to 5 vol.%., most preferably 3.5 to 4.5 vol.%.. As shown in the Examples below, a formulation comprising ethanol in a concentration as defined above, as well as sodium acetate in a concentration as defined above, ensures high purity and long stability of the radiolabeled complex.

[0081] In some embodiments, other stabilizers may be present in addition to sodium acetate (NaOAc) and ethanol. Examples of such further stabilizers include ascorbic acid and / or a salt thereof, e.g. sodium ascorbate, gentisic acid, methionine, histidine, melatonine, and Se-methionine.

[0082] In a preferred embodiment, the pharmaceutical composition comprises, in addition to sodium acetate (NaOAc) and ethanol, ascorbic acid and / or a salt thereof.

[0083] Various salts of ascorbic acid are known in the art and readily available. In general, the term "salt" refers to an ionic assembly of cations and anions, which is composed of related numbers of cations and anions, so that the product (the salt) is electrically neutral (without net charge). In salts of ascorbic acid, the salts are typically formed with the ascorbate anion. Preferred salts of ascorbic acid include the alkali salts of ascorbic acid. The term "alkali salt" refers to salts that produce hydroxide ions when dissolved in water. Non-limiting examples of preferred salts of ascorbic acid include sodium, potassium, calcium, magnesium and lithium salts of ascorbic acid; such as sodium ascorbate, sodium ascorbyl phosphate, potassium ascorbate, calcium ascorbate, magnesium ascorbate, magnesium ascorbyl phosphate and lithium ascorbate. Most preferably, the salt of ascorbic acid is a sodium salt of ascorbic acid, in particular sodium ascorbate.

[0084] It is preferred that the concentration of the salt of ascorbic acid, in particular sodium ascorbate, if present in the pharmaceutical composition, is in the range from 1 mg to 100 mg / mL, preferably in the range from 10 mg / mL to 90 mg / mL, more preferably in the range from 10 mg / mL to 80 mg / mL, still more preferably in the range from 10 mg / mL to 70 mg / mL, still more preferably in the range from 10 mg / mL to 60 mg / mL, particular preferably in the range from 10 mg / mL to 50 mg / mL, most preferably in the range from 10 mg / mL to 40 mg / mL. In a preferred embodiment, the concentration of the salt of ascorbic acid, in particular sodium ascorbate, in the pharmaceutical composition is below 40 mg / mL, i.e. in a range from 0, 1 , 2, 3, 4, 5, 6, 7, 8, 9, or 10 mg / mL to 40 mg / mL. If the pharmaceutical composition comprises a salt of ascorbic acid, its concentration may be selected from 15 mg / mL to 50 mg / mL or 20 mg / mL to 50 mg / mL. In another embodiment, if the pharmaceutical composition comprises a salt of ascorbic acid, its concentration may be selected from 20 mg / mL to 40 mg / mL or, preferably, 30 mg / mL to 40 mg / mL. The salt of ascorbic acid is preferably sodium ascorbate.

[0085] In another embodiment, the pharmaceutical composition comprises ascorbic acid and / or the salt of ascorbic acid at a concentration of at least 10 mg / mL or, preferably, at least 15 mg / mL or more preferably at least 20 and even more preferably at least 30 mg / mL. The upper limit may be selected from the group consisting of 40 mg / mL or 50 mg / mL, such that the concentration range e.g. is from 15 mg / mL to 50 mg / mL or, in particular from 20 mg / mL to 40 mg / mL or from 30 mg / mL to 40 mg / mL.

[0086] As shown in the Examples below, a formulation comprising sodium ascorbate in a concentration as defined above ensures high purity and long stability of the radiolabeled complex.

[0087] Thus, the pharmaceutical composition of the present invention comprises as stabilizers sodium acetate (NaOAc) and ethanol, and optionally comprises sodium ascorbate, preferably in the concentrations defined above. More preferably, sodium acetate (NaOAc), ethanol, and, optionally, sodium ascorbate are the only stabilizers present in the pharmaceutical composition. In other words, the stabilizer comprised in the pharmaceutical composition preferably consists of sodium acetate (NaOAc), ethanol, and, optionally, sodium ascorbate, preferably in the concentrations as defined above.

[0088] In another preferred embodiment, the pharmaceutical composition does not comprise any of the following: gentisic acid or a salt thereof, methionine, histidine, melatonine, and Se- methionine. In another embodiment, the pharmaceutical composition does not comprise ascorbic acid or a salt of ascorbic acid. Furthermore, the pharmaceutical composition may not comprise any of gentisic acid or a salt thereof, ascorbic acid or a salt thereof, methionine, histidine, melatonine, and Se-methionine. In another embodiment, the pharmaceutical composition may comprise as stabilizer sodium acetate (NaOAc) and ethanol only. In a preferred embodiment, the pharmaceutical composition comprises 9.0 mg / mL to 100 mg / mL NaOAc, 2 to 20 vol.% Ethanol and 0 to 40 mg / mL Na-Ascorbate.

[0089] In another preferred embodiment, the pharmaceutical composition comprises 7 mg / mL to 15 mg / mL NaOAc, 2 to 7 vol.%, more preferably 3 vol.% to 5 vol.% ethanol and 30 mg / mL to 50 mg / mL of a salt of ascorbic acid, in particular Na-Ascorbate. Thereby, the pharmaceutical composition may comprise 7 mg / mL to 12 mg / mL NaOAc, 3 vol.% to 5 vol.% ethanol and 30 mg / mL to 40 mg / mL of a salt of ascorbic acid, in particular Na-Ascorbate. Alternatively, the pharmaceutical composition may comprise 7 mg / mL to 15 mg / mL NaOAc, 3 to 5 vol.% Ethanol, and 20 mg / mL to 40 mg / mL Na-Ascorbate. As shown in the appended Examples, pharmaceutical composition comprising the stabilizer(s) in amounts defined above, exhibit radiochemical purity of > 94% over at least 72 hours.

[0090] In a preferred embodiment, the pharmaceutical composition comprises (i) 7 mg / mL to 12 mg / mL NaOAc, 3 to 5 vol.% Ethanol, and 30 mg / mL to 40 mg / mL Na-Ascorbate, (ii) the composition further does not comprise a sequestering agent, and further (iii) the composition does not comprise any of the following: gentisic acid or a salt thereof, methionine, histidine, melatonine, and Se-methionine.

[0091] The pharmaceutical composition according to the present invention is preferably an aqueous solution, in particular a radiopharmaceutical aqueous solution. As used herein, an "aqueous solution" is usually a solution of one or more solute(s) in water.

[0092] In some embodiments, the pharmaceutical composition may comprise a further buffer, e.g. a citrate buffer or a phosphate buffer. However, it is preferred that the pharmaceutical composition does not contain any buffer in addition to sodium acetate and, optionally, sodium ascorbate, which are present as stabilizer(s) and also provide buffering functionality.

[0093] In some embodiments, the pharmaceutical composition may comprise a sequestering agent, such as diethylenetriaminepentaacetic acid (DTPA) or a salt thereof. As used herein, the term "sequestering agent" refers to an agent suitable to complex the radionuclide metal ions, such as DTPA. However, the present inventors have found that addition of a sequestering agent is not required. Thus, it is preferred that the pharmaceutical composition does not comprise a sequestering agent, such as DTPA. DTPA is known to induce side effects, such as nausea, vomiting, diarrhea, chills, fever, itching, muscle cramps, headache, light-headedness and chest pain. Therefore, it is preferred, that the pharmaceutical composition does not comprise DTPA.

[0094] Thus, in a preferred embodiment, the excipients of the pharmaceutical composition consist essentially of sodium acetate, ethanol, optionally sodium ascorbate, and water.

[0095] In a particular embodiment, the pharmaceutical composition may consist (essentially) of

[0096] (a) a radiolabeled complex comprising225Ac-PSMA-617;

[0097] (b) a stabilizer comprising 9 to 100 mg / mL sodium acetate, 1 .0 to 30 % (vol / vol) ethanol, 0 to 40 mg / mL sodium ascorbate; and

[0098] (c) water.

[0099] In another particular embodiment, the pharmaceutical composition may consist (essentially) of

[0100] (a) a radiolabeled complex comprising225Ac-PSMA-l&T;

[0101] (b) a stabilizer comprising 9 to 100 mg / mL sodium acetate, 1 .0 to 30 % (vol / vol) ethanol, 0 to 40 mg / mL sodium ascorbate; and

[0102] (c) water.

[0103] In a further particular embodiment, the pharmaceutical composition may consist (essentially) of

[0104] (a) a radiolabeled complex comprising225Ac-lbu-DAB-PSMA;

[0105] (b) a stabilizer comprising 9 to 100 mg / mL sodium acetate, 1 .0 to 30 % (vol / vol) ethanol, 0 to 40 mg / mL sodium ascorbate; and

[0106] (c) water.

[0107] In a still further embodiment, the pharmaceutical composition may consist (essentially) of

[0108] (a) a radiolabeled complex comprising225Ac-DOTA-RGD;

[0109] (b) a stabilizer comprising 9 to 100 mg / mL sodium acetate, 1 .0 to 30 % (vol / vol) ethanol, 0 to 40 mg / mL sodium ascorbate; and

[0110] (c) water. In another particular embodiment, the pharmaceutical composition may consist (essentially) of

[0111] (a) a radiolabeled complex comprising225Ac-PSMA-617;

[0112] (b) a stabilizer comprising 7 to 12 mg / mL sodium acetate, 1 .0 to 7 % (vol / vol) ethanol, 0 to 50 mg / mL sodium ascorbate; and

[0113] (c) water.

[0114] In another particular embodiment, the pharmaceutical composition may consist (essentially) of

[0115] (a) a radiolabeled complex comprising225Ac-PSMA-l&T;

[0116] (b) a stabilizer comprising 7 to 12 mg / mL sodium acetate, 1.0 to 7 % (vol / vol) ethanol, 30 to 40 mg / mL sodium ascorbate; and

[0117] (c) water.

[0118] In a further particular embodiment, the pharmaceutical composition may consist (essentially) of

[0119] (a) a radiolabeled complex comprising225Ac-lbu-DAB-PSMA;

[0120] (b) a stabilizer comprising 7 to 12 mg / mL sodium acetate, 3 to 5 % (vol / vol) ethanol, 30 to 40 mg / mL sodium ascorbate; and

[0121] (c) water.

[0122] In a still further embodiment, the pharmaceutical composition may consist (essentially) of

[0123] (a) a radiolabeled complex comprising225Ac-DOTA-RGD;

[0124] (b) a stabilizer comprising 9 to 10 mg / mL sodium acetate, 3.5 to 4.5 % (vol / vol) ethanol, 35 to 40 mg / mL sodium ascorbate; and

[0125] (c) water.

[0126] In the pharmaceutical composition, the radionuclide, in particular225Ac, may be present at a concentration providing volumetric radioactivity of 0.4 to 4.0 MBq / mL or 0.2 to 2 MBq / mL, preferably of 1 .0 to 4.0 MBq / mL or 0.2 to 1 MBq / mL, more preferably 0.3 to 0.8 MBq / mL, most preferably 0.35 to 0.45 MBq / mL.

[0127] In some embodiments, the pharmaceutical composition is substantially free of precursors of the radiolabeled complex, e.g. of precursors of225Ac-PSMA-617,225Ac-PSMA-l&T,225Ac-lbu- DAB-PSMA and225Ac-DOTA-RGD, respectively. In some embodiments, the amount of precursors of the radiolabeled complex, in particular precursors of225Ac-PSMA-617,225Ac- PSMA-I&T,225Ac-lbu-DAB-PSMA and22SAc-DOTA-RGD, respectively in the pharmaceutical composition is no more than 5%, preferably no more than 2%, more preferably no more than 1 %, even more preferably no more than 0.5% of the amount of radiolabeled complex, e.g.225Ac-PSMA-617,225Ac-PSMA-l&T,225Ac-lbu-DAB-PSMA and225Ac-DOTA-RGD, respectively, in the final pharmaceutical composition (to be injected / infused). Even more preferably, the pharmaceutical composition is essentially free of precursors of the radiolabeled complex, e.g. of precursors of225Ac-PSMA-617,225Ac-PSMA-I&T,225Ac-lbu-DAB-PSMA and225Ac-DOTA-RGD, respectively. In a particularly preferred embodiment, the pharmaceutical composition is essentially free of a precursor of225Ac-lbu-DAB-PSMA.

[0128] As shown in the appended examples, the pharmaceutical composition according to the present invention can provide a shelf life of at least 24 h, in particular when stored at room temperature (RT) (e.g., 23°C / 70% RH (relative humidity)). In some embodiments, the shelf life of the pharmaceutical composition is at least 24 h, preferably at least 48 h, more preferably at least 72 h and even more preferably at least 96 h, in particular when stored at RT.

[0129] Moreover, the appended Examples show that the use of the specific stabilizer(s) as described herein provides at least 94% radiochemical purity of the225Ac labeled compounds for at least 72 hours, in particular when stored at RT. For example, for various formulations according to the present invention as described herein225Ac-labeled compounds having at least 95% radiochemical purity and <1 .0% uncomplexed "free"225Ac3+was found after 72 hours. More preferably, the radiochemical purity of the pharmaceutical composition can be maintained at > 95%, more preferably at > 96%, even more preferably at > 97%, still more preferably at > 99% for at least 72 h, and uncomplexed "free"225Ac3+can be maintained at < 1 .4%, preferably at < 1.0%, more preferably at < 0.5%, still more preferably at < 0.25%, in particular when stored at RT. To this end, radiochemical purity may be determined by radio TLC or HPLC as known in the art and described in the Examples.

[0130] The formulation ensures radiolysis-stable radioactivity concentrations of 0.2 to 4 MBq / mL, 0.4-4.0 MBq / mL, 0.2 to 2 MBq / mL, 0.2 to 1 MBq / mL or 0.3 to 0.8 MBq / mL or, most preferably, most preferably 0.35 to 0.45 MBq / mL, thereby guaranteeing radiolysis-stable volumes of 1 -20 mL.

[0131] In a preferred embodiment, the pharmaceutical composition comprises (i) 7 mg / mL to 12 mg / mL NaOAc, 3 to 5 vol.% Ethanol, and 30 mg / mL to 40 mg / mL Na-Ascorbate, (ii) the composition further does not comprise a sequestering agent, (iii) the composition further does not comprise any of the following: gentisic acid or a salt thereof, methionine, histidine, melatonine, and Se-methionine, and (iv) the225Ac radionuclide is present in the composition at a concentration providing volumetric radioactivity of 0.3 to 0.8 MBq / mL, preferably 0.35 to 0.45 MBq / mL.

[0132] In a further preferred embodiment, the pharmaceutical composition comprises (i) 7 mg / mL to 12 mg / mL NaOAc, 3 to 5 vol.% Ethanol, and 30 mg / mL to 40 mg / mL Na-Ascorbate, (ii) the composition further does not comprise a sequestering agent, (iii) the composition further does not comprise any of the following gentisic acid or a salt thereof, methionine, histidine, melatonine, and Se-methionine, (iv) the225Ac radionuclide is present in the composition at a concentration providing volumetric radioactivity of 0.3 to 0.8 MBq / mL, preferably 0.35 to 0.45 MBq / mL, and (v) the radiolabeled complex comprises or consists of the225Ac (Actinium- 225) radionuclide and Ibu-DAB-PSMA, more preferably (5)-lbu-DAB-PSMA.

[0133] The pharmaceutical composition may be for intravenous (iv) use / application / administration. The pharmaceutical composition is typically stable, concentrated, and ready-to-use.

[0134] The pharmaceutical composition according to the present invention may be provided as single-dose product, e.g. in a vial containing a single dose of the radiolabeled complex. To this end, the vial may contain about 1 to 25 ml of the pharmaceutical composition, preferably 1 to 20 ml of the pharmaceutical composition, more preferably 1 to 15 ml of the pharmaceutical composition, and even more preferably 1 ml to 10 ml of the pharmaceutical composition. A single dose may allow delivery of 0.5 to 40 MBq± 10% of radioactivity at injection time, preferably of 1 to 20 MBq ± 10% of radioactivity at injection time, more preferably of about 1 to 20 MBq ± 10% of radioactivity at injection time, such as e.g. of 7.5 MBq ± 10% of radioactivity at injection time. Preferably, each of the stabilizers sodium acetate and ethanol present in the (final) pharmaceutical composition is / are already present during complex formation (radiolabeling).

[0135] As used herein, the expression "present during complex formation" is intended to refer to such agents / compounds, which are present in the reaction mixture (also referred to as "radiolabeling composition") for the complex formation (radiolabeling). To obtain the radiolabeling reaction mixture (radiolabeling composition), the radionuclide solution is added to the solution containing the chelating moiety linked to the targeting moiety (or vice versa). Accordingly, any agent / compound present during complex formation (radiolabeling), such as a stabilizer, may be contained in either the radionuclide solution, in the solution containing the chelating moiety linked to the targeting moiety, or in a separate solution to be added. After obtaining the radiolabeling composition, elevated temperatures, such as 80 to 90°C, may be applied to the radiolabeling composition (including the agents / compounds comprised therein) for a defined time window, such as 5 to 25 minutes, to facilitate the complex formation (radiolabeling).

[0136] As described above, it is preferred that each of the stabilizers sodium acetate and ethanol present in the (final) pharmaceutical composition is / are already present during complex formation (radiolabeling). However, the concentrations and / or weight ratios of the stabilizer(s) in the radiolabeling composition (reaction mix) during complex formation (radiolabeling) may be distinct from the concentrations and / or weight ratios of the stabilizer(s) in the (final) pharmaceutical composition. For example, one or more of the stabilizers present during complex formation (radiolabeling) may be additionally added after the complex formation (radiolabeling).

[0137] As used herein, the expression "after the complex formation (radiolabeling)" refers to the time when the complex forming (radiolabeling) reaction is completed. For example, when elevated temperatures were applied for radiolabeling, "after the complex formation (radiolabeling)" may refer to a time when the radiolabeling composition (radiolabeling reaction mixture) is no longer exposed to an elevated temperature (for example, when ambient temperature is reached again, e.g. by cooling down the radiolabeling composition). In particular, "after the complex formation (radiolabeling)" may refer to the formulation of the (final) pharmaceutical composition, e.g. by dilution of the radiolabeling mix with water. Accordingly, it is preferred that sodium acetate and ethanol are present during complex formation (radiolabeling). It is also preferred that sodium acetate and ethanol are added after complex formation (radiolabeling). More preferably, sodium acetate and ethanol are present during complex formation (radiolabeling), and sodium acetate and ethanol are added after complex formation (radiolabeling). In a further preferred embodiment, sodium ascorbate is not present during complex formation (radiolabeling). In a further preferred embodiment, sodium ascorbate is added after complex formation

[0138] Thereby, it is preferred that sodium acetate is present during complex formation (i.e., in the radiolabeling composition) at a concentration of 9 mg / mL to 100 mg / mL, preferably 10 mg / mL to 100 mg / mL, e.g. 20 mg / mL to 90 mg / mL, 30 mg / mL to 80 mg / mL, 40 mg / mL to 70 mg / mL, 50 mg / mL to 60 mg / mL.

[0139] It is also preferred that ethanol is present during complex formation (i.e., in the radiolabeling composition) at a concentration of 1 to 30 % (vol / vol), preferably 2 to 20% (vol / vol), more preferably 5 to 10% (vol / vol).

[0140] Medical treatment and uses

[0141] In a further aspect, the present invention also provides the use of the pharmaceutical composition as described above in medicine. For example, the pharmaceutical composition as described above may be preferably used in the treatment or in the (in vitro) diagnosis of cancer (e.g., by using an isolated sample, for example a blood sample or tumor tissue). Accordingly, the present invention also provides a method for treating cancer or initiating, enhancing or prolonging an anti-tumor-response in a subject in need thereof comprising administering to the subject the pharmaceutical composition as described above.

[0142] It is understood that for medical purposes, the pharmaceutical composition usually comprises an effective amount of the radiolabeled complex. As used herein, an "effective amount" means an amount of the agent(s) that is sufficient to allow for diagnosis and / or significantly induce a positive modification of the disease to be treated. At the same time, however, an "effective amount" may be small enough to avoid serious side-effects, that is to say to permit a sensible relationship between advantage and risk. An "effective amount" may vary depending on the particular condition to be diagnosed or treated and also with the age and physical condition of the patient to be treated, the severity of the condition, the duration of the treatment, the nature of the accompanying therapy, of the particular pharmaceutically acceptable excipient or carrier used, and similar factors. Accordingly, an "effective amount" may be readily determined in a specific situation by the physician. In general, effective doses may be determined by routine experiments, e.g. by using animal models. Such models include, without implying any limitation, rabbit, sheep, mouse, rat, dog and non-human primate models. Therapeutic efficacy and toxicity of radiolabeled complexes can be determined by standard pharmaceutical procedures in cell cultures or experimental animals, e.g., for determining the LD50 (the dose lethal to 50% of the population) and the ED50 (the dose therapeutically effective in 50% of the population). The dose ratio between toxic and therapeutic effects is the therapeutic index and can be expressed as the ratio LD50 / ED50. The data obtained from the cell culture assays and animal studies can be used in determining a dose range for use in humans. The dose of said conjugates lies preferably within a range of circulating concentrations that include the ED50 with little or no toxicity.

[0143] As used herein, the term "diagnosis" or "diagnosing" refers to act of identifying a disease from its signs and symptoms and / or as in the present case the analysis of biological markers (such as proteins) indicative of the disease.

[0144] As used herein, the term "treatment" or "treating" of a disease includes preventing or protecting against the disease (that is, causing the clinical symptoms not to develop); inhibiting the disease (i.e., arresting or suppressing the development of clinical symptoms; and / or relieving the disease (i.e., causing the regression of clinical symptoms). As will be appreciated, it is not always possible to distinguish between "preventing" and "suppressing" a disease or disorder since the ultimate inductive event or events may be unknown or latent. Accordingly, the term "prophylaxis" will be understood to constitute a type of "treatment" that encompasses both "preventing" and "suppressing." The term "treatment" thus includes "prophylaxis". Accordingly, the term "treatment" includes prophylactic treatment (before onset of the disease) as well as therapeutic treatment (after onset of the disease).

[0145] The pharmaceutical compositions as described herein are typically administered parenterally. Administration may preferably be accomplished systemically, for instance by intravenous (i.v.), subcutaneous, intramuscular or intradermal injection. Alternatively, administration may be accomplished locally, for instance by intra-tumoral injection. The pharmaceutical compositions as described above may be administered to a subject in need thereof several times a day, daily, every other day, weekly, or monthly.

[0146] Pharmaceutical compositions of the invention comprising radiolabeled complexes with a targeting moiety binding to PSMA, may be used in the treatment or diagnosis of any cancer expressing PSMA. In particular, the presence of PSMA-expressing cells or tissues may be indicative of a prostate tumor (cell), a metastasized prostate tumor (cell), a renal tumor (cell), a pancreatic tumor (cell), a bladder tumor (cell), and combinations thereof. Accordingly, the cancer is preferably prostate cancer, pancreatic cancer, renal cancer or bladder cancer.

[0147] Pharmaceutical compositions of the invention comprising radiolabeled complexes with a targeting moiety binding to aV / ?3, may be used in the treatment or diagnosis of tumor-induced angiogenesis, as described above.

[0148] The pharmaceutical composition as described above may be used for both imaging and therapeutic purposes, i.e. as a "theragnostic" agent. As used herein, the term "theragnostic" includes "therapeutic-only", "diagnostic-only" and "therapeutic and diagnostic" applications. Accordingly, in a further aspect, the present invention also provides an (in vitro) method of detecting the presence of cancerous cells and / or tissues comprising (a) contacting said cancerous cells and / or tissues with the pharmaceutical composition of the invention and (b) applying detection means, optionally radiographic imaging, to detect said cells and / or tissues.

[0149] In the in vivo and in vitro uses and methods of the present invention, radiographic imaging may be accomplished using any means and methods known in the art. Preferably, radiographic imaging may involve positron emission tomography (PET) or single-photon emission computed tomography (SPECT). The targeted cells or tissues detected by radiographic imaging of the inventive conjugate may preferably comprise (optionally cancerous) prostate cells or tissues, (optionally cancerous) spleen cells or tissues, or (optionally cancerous) kidney cells or tissues. Method for preparing the pharmaceutical composition

[0150] The present invention also provides a method for preparing a pharmaceutical composition according to the present invention.

[0151] A method for preparing a pharmaceutical composition according to the present invention comprises

[0152] (i) formation of the radiolabeled complex; and

[0153] (ii) formulation of the pharmaceutical composition.

[0154] Formation of the radiolabeled complex (step (i)) is achieved by radiolabeling a targeting moiety covalently linked to a chelating moiety with 225-Actinium in a labeling buffer.

[0155] Thus, in a further aspect the present invention provides a method for radiolabeling a targeting moiety covalently linked to a chelating moiety with 225-Actinium comprising the steps of

[0156] (a) combining a225Ac radionuclide, a radiolabeling precursor comprising a targeting moiety covalently linked to a chelating moiety, and a labeling buffer comprising sodium acetate and ethanol; and

[0157] (b) heating the mixture for a predetermined period of time to obtain a225Ac-labeled complex comprising the225Ac radionuclide and the targeting moiety covalently linked to the chelating moiety.

[0158] As described above, formulation of the pharmaceutical composition (step (ii)) is accomplished by adding a formulation buffer to the radiolabeled complex to obtain the final pharmaceutical composition. The final pharmaceutical composition is preferably a pharmaceutical composition according to the present invention.

[0159] Thus, in a further aspect, the present invention provides a method for preparing a pharmaceutical composition comprising the following steps: (a1) formation of a radiolabeled complex (radiolabeling) by heating a radiolabeling solution comprising (i) a225Ac (Actinium-225) radionuclide, (ii) a radiolabeling precursor comprising a targeting moiety covalently linked to a chelating moiety, and (iii) a radiolabeling buffer comprising sodium acetate (NaOAc) and ethanol for a defined period of time; and (b') formulating the pharmaceutical composition by adding a formulation buffer comprising water, in particular water for injection, sodium acetate and ethanol, and optionally comprising a salt of ascorbic acid, in particular Na-ascorbate;

[0160] (c1) optionally sterile filtrating the obtained solution of the225Ac-labeled complex.

[0161] It is understood that the above detailed description applies accordingly to the method for radiolabeling a targeting moiety covalently linked to a chelating moiety with 225-Actinium, and for the method for preparing the pharmaceutical composition according to the present invention, respectively. For example, detailed embodiments described above for the radiolabeled complex of the pharmaceutical composition apply accordingly to the method for radiolabeling a targeting moiety covalently linked to a chelating moiety with 225-Actinium, and for the method for preparing the pharmaceutical composition according to the present invention, respectively.

[0162] Accordingly, step (i), i.e. the formation of the radiolabeled complex, is preferably performed in a radiolabeling composition comprising (or consisting essentially of) the radionuclide and the targeting moiety linked to the chelating moiety as described above; and a radiolabeling buffer comprising sodium acetate and ethanol.

[0163] In the radiolabeling composition obtained in step (a) and / or (a'), respectively, sodium acetate is preferably present at a concentration of 9 mg / mL to 100 mg / mL, more preferably 20 mg / mL to 90 mg / mL, 30 mg / mL to 80 mg / mL, even more preferably 40 mg / mL to 70 mg / mL, still more preferably 50 mg / mL to 60 mg / mL. Preferably, the radiolabeling composition contains 9.8 mg / mL to 98.4 mg / mL sodium acetate, which corresponds to 2.7 mg / MBq to 6.6 mg / MBq.

[0164] Further, in the radiolabeling composition obtained in step (a) and / or (a'), respectively, ethanol is present at a concentration of 1 to 30 % (vol / vol), preferably 2 to 20% (vol / vol), more preferably 3 to 15% (vol / vol), still more preferably 5 to 10% (vol / vol).

[0165] In step (a) and / or (a'), respectively, (radiolabeling step), a radiolabeling reaction mixture (radiolabeling composition) is obtained by combining a radionuclide solution (comprising e.g. [225Ac]AcCl3 in HCI), a solution containing the chelating moiety linked to the targeting moiety (=radiolabeling precursor), and a radiolabeling buffer comprising sodium acetate and ethanol as stabilizers. Preferably, in the radiolabeling process (step (a) and / or step (b) of the radiolabeling method, and step (a') of the method for preparing a pharmaceutical composition, respectively), the formation of a radiolabeled complex (radiolabeling) is performed in an aqueous solution.

[0166] Preferably, the radiolabeling composition in step (a) and / or (a'), respectively, has a pH of about 4.0 to 5.5, more preferably about 4.5 to 5.0. The buffer is useful to maintain such an advantageous pH range. Preferably, the radiolabeling buffer has a pH of about 6.0 to 9.0, preferably of about 7 to 8, more preferably of about 7.0. The use of a radiolabeling buffer in step (a) and / or (a'), respectively, has the advantage that the pH can be maintained even for different amounts of Ac (225Ac) chloride solution used for radiolabeling, as required, while the pH is maintained.

[0167] Preferably, sodium acetate and ethanol are the only stabilizers present during the radiolabeling steps (a / b) and (a'), respectively. In particular, it is preferred that the radiolabeling composition does not comprise a salt of ascorbic acid, in particular Na-ascorbate and / or does not comprise any other stabilizer, such as gentisic acid. Thus, in a preferred embodiment, the radiolabeling buffer comprises sodium acetate and ethanol, and preferably does not comprise any other stabilizer such as a salt of ascorbic acid, in particular Na-ascorbate, or gentisic acid. More preferably, the labeling buffer consists essentially of sodium acetate, ethanol and water.

[0168] The precursor compound (the targeting moiety linked to the chelating moiety) used in the radiolabeling step, in particular in step (a) and / or (a'), respectively, to form the radiolabeled complex, may be as described above (with respect to the pharmaceutical composition).

[0169] Accordingly, the precursor compound (the targeting moiety linked to the chelating moiety) used in the radiolabeling step, in particular in step (a) and / or (a'), respectively, to form the radiolabeled complex, may comprise a targeting moiety which is able to bind to PSMA or avp3 integrin, as described above.

[0170] Moreover, the precursor compound (the targeting moiety linked to the chelating moiety) used in the radiolabeling step, in particular in step (a) and / or (a'), respectively, of the inventive method for radiolabeling a targeting moiety covalently linked to a chelating moiety with 225- Actinium, and method for preparing a pharmaceutical composition, respectively, to form the radiolabeled complex, may comprise a targeting moiety which is able to bind to the somatostatin receptor.

[0171] The somatostatin receptor in numerous tumors, in particular neuroendocrine tumors, such as e.g. gastroenteropancreatic neuroendocrine tumor, carcinoid tumor, pheochromocytoma, paraganglioma, medullary thyroid cancer, pulmonary neuroendocrine tumor, thymic neuroendocrine tumor, a carcinoid tumor or a pancreatic neuroendocrine tumor, pituitary adenoma, adrenal gland tumors, Merkel cell carcinoma, breast cancer, Non-Hodgkin lymphoma, Hodgkin lymphoma, Head & Neck tumor, urothelial carcinoma (bladder), Renal Cell Carcinoma, Hepatocellular Carcinoma, GIST, neuroblastoma, bile duct tumor, cervix tumor, Ewing sarcoma, osteosarcoma, small cell lung cancer (SCLC), prostate cancer, melanoma, meningioma, glioma, medulloblastoma, hemangioblastoma, supratentorial primitive, neuroectodermal tumor, and esthesioneuroblastoma, functional carcinoid tumor, insulinoma, gastrinoma, vasoactive intestinal peptide (VIP) oma, glucagonoma, serotoninoma, histaminoma, ACTHoma, pheocromocytoma, and somatostatinoma.

[0172] Conjugates comprising a chelating moiety and a targeting moiety, which is able to bind to a somatostatin receptor, may e.g. be selected from DOTA-OC ((DOTA^D-Phe^octreotride), DOTATOC ([DOTA^D-Phe^TyPjoctreotride; INN: edotreotide), DOTANOC ([DOTA°,D- Phe^i-NaPjoctreotride), DOTATATE ([DOTA^D-Phe^TyPjoctreotate; INN: oxodotreotide), DOTALAN ([DOTA°,D-P-NaP]octreotride), DOTAVAP ([DOTA^D-Phe^TyPjvapreotide), satoreotide trizoxetan and satoreotide tetraxetan and DOTA-JR11 (DOTA-(Cpa-c(D-Cys- Aph(Hor)-d-Aph(Cbm)-Lys-Thr-Cys)D-Tyr-NH2).

[0173] Thus, the molecule comprising a chelating moiety and a targeting moiety used in the radiolabeling method of the present invention may be selected from e.g. DOTATOC (which may be represented by Formula 10), DOTA-JR1 1 (which may be represented by Formula 11 ), and DOTATATE (which may be represented by Formula 12) to provide a225Ac labeled radiopharmaceutical which effectively targets the somatostatin receptor. DOTATOC:

[0174] DOTA-JR11:

[0175] (ID DOTATATE:

[0176] Moreover, the targeting moiety linked to the chelating moiety of the precursor compound used in the radiolabeling step, in particular in step (a) and / or (a'), respectively, of the inventive method for radiolabeling a targeting moiety covalently linked to a chelating moiety with 225- Actinium, and method for preparing a pharmaceutical composition, respectively, may be directed to a number of further receptors which are known to be expressed on distinct tumor cells.

[0177] In one embodiment, the targeting moiety may be a folic acid conjugate binding the folate receptor, which is overexpressed e.g. in ovarian cancer.

[0178] In another embodiment, the targeting moiety linked to the chelating moiety of the precursor compound used in the radiolabeling step, in particular in step (a) and / or (a'), respectively, may target the CCK2-receptor (cholecystokinin) which is overexpressed in several types of human cancer, as medullar thyroid carcinomas, small cell lung cancers and stromal ovarian carcinomas. A variety of peptide ligands for targeting the CCK2 -receptor, all of which have the C-terminal CCK receptor-binding tetrapeptide sequence Trp-Met-Asp-Phe-NH2in common, has been synthesized and characterized. Examples for CCK receptor ligands are gastrin analogs, such as Sargastrin (Gln-Gly-Pro-Trp-Leu-Glu-Glu-Glu-Glu-Glu-Ala-Tyr-Gly- Trp-Nle-Asp-Phe-NH2), Minigastrin 0 (MG-0) D-Glu-(Glu)5-Ala-Tyr-Gly-Trp-Met-Asp-Phe- NH2), Minigastrin 1 1 (MG-11 ) (D-Glu-Ala-Tyr-Gly-Trp-Met-Asp-Phe-NH2), cyclo-Minigastrin 1 (cyclo-MG1 ) (cyclo[y-D-Glu-Ala-Tyr-D-Lys]-Trp-Met-Asp-Phe-NH2), cyclo-Minigastrin 2 (cyclo-MG2) (cyclo[y-D-Glu-Ala-Tyr-D-Lys]-Trp-Nle-Asp-Phe-NH2, Demogastrin 1 (D-GIU- (Glu)5-Ala-Tyr-Gly-Trp-Met-Asp-Phe-NH2), Demogastrin 2 (D-Glu-(Glu)5-Ala-Tyr-Gly-Trp- Met-Asp-Phe-NH2, H2-Met (His-His-Glu-Ala-Tyr-Gly-Trp-Met-Asp-Phe-NH2), H2-Nle (His- His-Glu-Ala-Tyr-Gly-Trp-Nle-Asp-Phe-NH2), H6-Met (His)6-Glu-Ala-Tyr-Gly-Trp-Met-Asp- Phe-NH2); and CCK8 analogs, such as CCK8 (D-Asp-Tyr-Met-Gly-Trp-Met-Asp-Phe-NH2), CCK8(Nle) (D-Asp-Tyr-Nle-Gly-Trp-Nle-Asp-Phe-NH2), sCCK8 (D-Asp-Tyr(OSO3H)-Met-Gly- Trp-Met-Asp-Phe-NH2), sCCK8[Phe2( / >CH2SO3H), Nle3,6] (D-Asp-Phe(p-CH2SO3H)-Nle-Gly- Trp-Nle-Asp-Phe-NH2), sCCK8[Phe2( / >CH2SO3H), HPG3 6] (D-Asp-Phe(p-CH2SO3H)-HPG- Gly-Trp-HPG-Asp-Phe-NH2).

[0179] The CCK receptor targeting peptides may be radiolabeled with225Ac using an appropriate chelating moiety as specified above, wherein DOTA, DOTAGA, and DOTAM may be preferred.

[0180] In another embodiment, the targeting moiety linked to the chelating moiety of the precursor compound used in the radiolabeling step, in particular in step (a) and / or (a'), respectively, may target the neurotensin receptor. Neurotensin receptor 1 (NTR1 ) is overexpressed in ductal pancreatic adenocarcinoma, which is one of the deadliest cancers. Therefore, radiopharmaceuticals may target the Neurotensin receptor 1 , in particular using radiolabeled NTR1 antagonists for cancer diagnosis or therapy. NTR1 antagonists, such as SR142948A and SR48692, may be linked to an appropriate chelating moiety, as specified above, which appropriately coordinates225Ac.

[0181] In another embodiment, the targeting moiety linked to the chelating moiety of the precursor compound used in the radiolabeling step, in particular in step (a) and / or (a'), respectively, may target the glucagon-like peptide-1 (GLP-1 ) receptor. The GLP-1 receptor is overexpressed on essentially all benign insulinomas and also on gastrinomas. Benign insulinomas which emerge from P-cells of the pancreas and are present as small nodules, secrete insulin leading to potentially life-threatening hypoglycemia. Peptides e.g. based on the 39-mer peptide exendin- 4, which is a GLP-1 receptor agonist, may be labelled with225Ac using a suitable chelating moiety as described herein to provide radiopharmaceuticals targeting the GLP-1 receptor.

[0182] In another embodiment, the targeting moiety linked to the chelating moiety of the precursor compound used in the radiolabeling step, in particular in step (a) and / or (a'), respectively, of the inventive methods may target the gastrin releasing peptide (GRP) receptor. GRP receptors have been demonstrated in major human tumors, such as breast cancer and prostate cancer. Bombesin is a tetradecapeptide neurohormone and an amphibian homolog of mammalian GRP (a 27mer peptide). Several bombesin analogs and bombesin antagonists may be labeled with225Ac using an appropriate chelating moiety as defined herein to provide radiopharmaceuticals targeting GRP receptor.

[0183] In another embodiment, the targeting moiety linked to the chelating moiety of the precursor compound used in the radiolabeling step, in particular in step (a) and / or (a'), respectively, of the inventive methods may target the neurokinin type 1 receptor. The neurokinin type 1 receptor is consistently overexpressed on glioma cells and on tumor vessels (Hennig IM et al., Int J Cancer 1995; 61 : 786-792). The 11 -amino-acid peptide substance P (Arg Pro Lys Pro Gin Gin Phe Phe Gly Leu Met) acting via the neurokinin type 1 receptor may suitably be radiolabelled with225Ac using an appropriate chelating moiety as defined herein, e.g. DOTAGA, coordinating the radionuclide to provide radiopharmaceuticals targeting neurokinin type 1 receptor expressed e.g. on malignant gliomas.

[0184] Preferably, the molecule comprising a chelating moiety and a targeting moiety used in the (radiolabeling) methods of the present invention may be selected from PSMA-I&T, PSMA-617, Ibu-DAB-PSMA, DOTA-RGD, DOTATOC, DOTA-JR11 , and DOT AT ATE, in particular Ibu- DAB-PSMA having a DOTA chelator, more specifically (5)-lbu-DAB-PSMA having a DOTA chelator.

[0185] Particularly preferably, the radiolabeled complex (comprising the radionuclide, the targeting moiety and the chelating moiety coordinating the225Ac radionuclide) is225Ac-DOTATOC (225Ac-edotreotide),225Ac-DOTA-JR1 1 ,225Ac-DOTA-RGD,225Ac-lbu-DAB-PSMA (in particular,225Ac-DOTA-lbu-DAB-PSMA (albumin-binding entity conjugated via a linker entity composed of a diaminobutyric acid (DAB) and a lysine residue to the targeting moiety and comprising a DOTA chelator)),225Ac-DOTA-PSMA-617 or225Ac-PSMA-l&T, in particular225Ac-DOTA-lbu-DAB-PSMA, more specifically225Ac-DOTA-(5)-lbu-DAB-PSMA.

[0186] Preferably, the225Actinium radionuclide is present in the radiolabeling composition used in the radiolabeling step, in particular in step (a) and / or (a'), respectively, to form the radiolabeled complex, at a concentration providing volumetric radioactivity of 0.2 to 2 MBq / mL, 0.2 to 1 MBq / mL or 0.3 to 0.8 MBq / mL, or, in another embodiment, of 0.4 to 4.0 MBq / mL, preferably 0.5 to 3.0 MBq / mL, more preferably 0.6 to 2.0 MBq / mL, even more preferably 0.7 to 3.0 MBq / mL, such as about 0.8 MBq / mL.

[0187] In the radiolabeling composition obtained in step (a) and / or (a'), respectively, the precursor compound (targeting moiety linked to the chelating moiety) is preferably present at a concentration of 10 to 150 nmol / mL, preferably 10 to 130 nmol / mL, more preferably 1 1 to 129 nmol / mL, which corresponds to 13.7 to 41.2 nmol / MBq. The concentration of the targeting moiety linked to the chelating moiety is preferably in the range from 20 to 200 pg / mL, in particular 30 to 160 pg / mL.

[0188] After obtaining the radiolabeling composition in step (a) and / or (a'), respectively, elevated temperatures may be applied to the radiolabeling composition for a defined time window, in particular to facilitate the complex formation (radiolabeling). For example, a temperature in the range from 60 to 120°C, preferably from 70 to 110°C, more preferably from 80 to 100°C, still more preferably 80 to 95°C, most preferably 85 to 90 °C, such as about 87°C, may be applied to the radiolabeling composition in step (b) (of the radiolabeling method, as described herein) and step (a') (of the method for preparing a pharmaceutical composition, as described herein), respectively. Accordingly, step (b) and step (a'), respectively, is particularly preferably performed at a temperature of 87 + 4°C. The elevated temperature may be applied for a defined time window, preferably 5 to 30 min, more preferably 8 to 25 min, thereby obtaining a225Ac-labeled complex comprising the225Ac radionuclide and the targeting moiety covalently linked to the chelating moiety. As shown in the Examples below, a radiochemical yield of >99% and a radiochemical purity of >95% at the end of synthesis can be achieved with the radiolabeling method of the present invention.

[0189] In step (b') of the method for preparing a pharmaceutical composition, the (final) pharmaceutical composition is formulated, e.g. by dilution of the radiolabeling mix with a formulation buffer and water, in particular water for injection. In this respect, it should be noted that the reaction mixture resulting from the labeling reaction does not have to be removed, and the labeled product does not have to be purified or isolated before formulation.

[0190] The formulation buffer comprises sodium acetate and ethanol, and optionally comprises a salt of ascorbic acid, in particular Na-ascorbate. Thus, it is preferred that sodium acetate and ethanol are present during formation of the radiolabeled complex (step (a')) and, additionally, are added during formulation of the pharmaceutical composition (step (b')).

[0191] It is preferred to add in step (b1) a formulation buffer, which essentially consists of water, in particular water for injection, sodium acetate, ethanol, and sodium ascorbate.

[0192] Preferably, in step (b'), the formulation buffer comprising sodium acetate, ethanol, and optionally comprising a salt of ascorbic acid, in particular sodium ascorbate, is added in an amount so that the concentration of NaOAc in the formulation obtained in step (b') (by adding formulation buffer and water, in particular water for injection) is 9.0 mg / mL to 100 mg / mL. More preferably, the composition obtained in step (b') comprises 9.8 mg / mL to 98.4 mg / mL sodium acetate (corresponding to 2.7 mg / MBq to 65.6 mg / MBq) or 7 mg / mL to 20 mg / mL, 7 mg / mL to 15 mg / mL or 7 mg / mL to 12 mg / mL sodium acetate, preferably 7 mg / mL to 12 mg / mL sodium acetate). Preferably, the concentration of ethanol in the formulation obtained in step (b') is 2 to 20 vol.%, more preferably 2 to 7 vol.%, more preferably 3 to 5 vol.%, and the concentration of a salt of ascorbic acid, in particular sodium ascorbate, in the (final) formulation obtained in step (b') is below 40 mg / mL, i.e. 0 to 40 mg / mL, which corresponds to 0 to 9 mg / MBq, or 20 to 40 mg / mL or 30 to 40 mg / mL. Thereby, the composition obtained in step (b') may more preferably comprises 7 mg / mL to 12 mg / mL sodium acetate, the concentration of ethanol in the formulation obtained in step (b') may more preferably be 3 to 5 vol.%, and the concentration of a salt of ascorbic acid, in particular sodium ascorbate, in the (final) formulation obtained in step (b') may more preferably be 30 to 40 mg / mL. It is also preferred that sodium acetate and ethanol are the only stabilizers present during the radiolabeling step (step (a) or (a')), and that sodium acetate and ethanol, and optionally a salt of ascorbic acid, in particular sodium ascorbate, are the only stabilizers present during the formulation of the pharmaceutical composition (step (b'). In other words, preferably no other stabilizers (other than sodium acetate and ethanol, and optionally a salt of ascorbic acid, in particular sodium ascorbate) are used in the entire process, i.e. the radiolabeling step (a) and / or (a'), respectively, as well as the formulation step of the pharmaceutical composition (step (b')).

[0193] Preferably, also no sequestering agent, such as DTPA, is added to the pharmaceutical composition in the formulation step.

[0194] However, in some embodiments, also other diluents (such as saline) may be added. In this way, a final volume (and concentration) of the pharmaceutical composition may be reached, e.g. as ready-to-use pharmaceutical composition, for example as single-dose product. To this end, a final volume of about 1 to 20 ml of the pharmaceutical composition, preferably 1 to 10 ml of the pharmaceutical composition may be reached by appropriate dilution (and, optionally, addition of further pharmaceutical acceptable components).

[0195] As shown in the Examples below, the (pharmaceutical) composition obtained by the method according to the present invention has a radiochemical yield of > 94% over a period of at least 72 hours.

[0196] According to preferred embodiments, the pharmaceutical composition is administered parenterally, in particular via intravenous or intratumoral injection, and is accordingly formulated in liquid or lyophilized form for parenteral administration. Parenteral formulations may be stored in vials, IV bags, ampoules, cartridges, or prefilled syringes and can be administered as injections, inhalants, or aerosols, with injections being preferred.

[0197] Liquid pharmaceutical compositions administered via injection and in particular via intravasal, more preferably intravenous (i.v.) injection should preferably be sterile and stable under the conditions of manufacture and storage. Such compositions are typically formulated as parenterally acceptable aqueous solutions that are pyrogen-free, have suitable pH, are isotonic and maintain stability of the active ingredient(s). The pharmaceutical composition may comprise a pharmaceutically acceptable excipient, diluent or carrier. The term "pharmaceutically acceptable", as used herein, refers to a compound or agent that is compatible with the components of the pharmaceutical composition, in particular the active (anti-cancer) compounds, and does not interfere with and / or substantially reduce its therapeutic activities. Pharmaceutically acceptable carriers preferably have sufficiently high purity and sufficiently low toxicity to make them suitable for administration to a subject to be treated.

[0198] For liquid pharmaceutical compositions, suitable pharmaceutically acceptable excipients and carriers include water, typically pyrogen-free water; isotonic saline or buffered (aqueous) solutions, e.g. phosphate, citrate etc. buffered solutions. Particularly for injection of the (pharmaceutical) compositions, water or preferably a buffer, more preferably an aqueous buffer, may be used, which may contain a sodium salt, e.g. at least 50 mM of a sodium salt, a calcium salt, e.g. at least 0.01 mM of a calcium salt, and optionally a potassium salt, e.g. at least 3 mM of a potassium salt.

[0199] The sodium, calcium and, optionally, potassium salts may occur in the form of their halogenides, e.g. chlorides, iodides, or bromides, in the form of their hydroxides, carbonates, hydrogen carbonates, or sulfates, etc. Without being limited thereto, examples of sodium salts include e.g. NaCI, Nal, NaBr, Na2CC>3, NaHCCh, Na2SO4, examples of the optional potassium salts include e.g. KCl, KI, KBr, K2CC>3, KHCO3, K2SO4, and examples of calcium salts include e.g. CaCI2, Cal2, CaBr2, CaCO3, CaSO4, Ca(OH)2. Furthermore, organic anions of the aforementioned cations may be contained in the buffer.

[0200] Buffers suitable for injection purposes as defined above, may contain salts selected from sodium chloride (NaCI), calcium chloride (CaCl2) and optionally potassium chloride (KCl), wherein further anions may be present additional to the chlorides. Typically, the salts in the injection buffer are present in a concentration of at least 50 mM sodium chloride (NaCI), at least 3 mM potassium chloride (KCl) and at least 0,01 mM calcium chloride (CaCI2). The injection buffer may be hypertonic, isotonic or hypotonic with reference to the specific reference medium, i.e. the buffer may have a higher, identical or lower salt content with reference to the specific reference medium, wherein preferably such concentrations of the afore mentioned salts may be used, which do not lead to damage of cells due to osmosis or other concentration effects.

[0201] The pharmaceutical composition may be provided in lyophilized form. Lyophilized pharmaceutical compositions are preferably reconstituted in a suitable buffer, advantageously based on an aqueous carrier, prior to administration.

[0202] The present invention also provides a pharmaceutical composition obtained by the method of the invention as described above. Such a pharmaceutical composition typically exhibits the features of the above-described pharmaceutical composition. The present inventors have found that a pharmaceutical composition obtained by the method of the present invention has excellent stability.

[0203] The pharmaceutical compositions are also provided for use in the preparation of a medicament for the treatment of cancer, as described above.

[0204] EXAMPLES

[0205] In the following, particular examples illustrating various embodiments and aspects of the invention are presented. However, the present invention shall not to be limited in scope by the specific embodiments described herein. The following preparations and examples are given to enable those skilled in the art to more clearly understand and to practice the present invention. The present invention, however, is not limited in scope by the exemplified embodiments, which are intended as illustrations of single aspects of the invention only, and methods which are functionally equivalent are within the scope of the invention. Indeed, various modifications of the invention in addition to those described herein will become readily apparent to those skilled in the art from the foregoing description and the examples below. All such modifications fall within the scope of the appended claims.

[0206] Example 1 : Effect of various buffer systems on radiolabeling yield of [225AclAc-DOTA- PSMA

[0207] Various buffer systems of different kinds and concentrations were investigated in the radiolabeling reaction regarding the yield of radiolabeling of [225Ac]Ac-DOTA-PSMA. The conjugate used in the labeling studies was Ibu-DAB-PSMA.

[0208] Radiolabeling was performed in a qualified heating block (Thermo Fisher Scientific Inc. USA). To this end, test buffer (100-200 pl / MBq [225Ac] AcCh), ethanol (10-30 % of the volume of the labeling solution), and the chemical DOTA precursor (about 14 nmol / MBq [225Ac]AcCl3), were added directly to a 2 mL vial containing the radionuclide precursor [225Ac]AcCb dissolved in 0.04 M HCI (40 MBq / mL) (ITM Medical Isotopes GmbH, Munich, Germany). The reaction mixture was heated for 8 -25 min at 87°C to obtain225Ac labeled DOTA-PSMA. Free Actinium radionuclide,225Ac labeled DOTA-PSMA, and impurities, were determined employing radio thin-layer chromatography (TLC) and radio-HPLC, respectively, as described below.

[0209] Radio thin-layer chromatography (TLC):

[0210] Silica on aluminum strip 60 F254 (Merck Millipore) and a qualified ScanRAM Radiograph with LAURA software (both LabLogic Systems Ltd.) were used for radio thin-layer chromatography. Approximately 5 kBq or 5 pL of the Ac-225 labeled substance, respectively, was spotted onto the thin-layer chromatography strips (TLC strips) and developed in 0.1 M sodium citrate (pH = 7.5) in the first step. After drying in an air stream, the TLC strips were developed again in a second step with 0.1 M ammonium acetate-acetonitrile mixture (1 :1 ). The TLC strips were read out on a radiograph after 6 hours at the earliest, in the best case only after 24 hours after development, in order to ensure that the decay equilibrium was set at the time of measurement. Alternatively, the TLC strips were cut into pieces and the Fr-221 gamma emission line was measured on an HPGe gamma detector at the earliest after setting the Ac- 225 / Fr-221 equilibrium (1 hour after development). An Rf value = 0.4 - 0.6 was determined for the radiolabeled compound, an Rf value = 0.8 - 0.9 for [225Ac]Ac citrate and an Rf value = 0.001 for insoluble 225Ac colloids. If only the citrate method was used, the Rf value for the radiolabeled substances is Rf = 0.0 - 0.1 .

[0211] Radio-HPLC:

[0212] Radio-UVA / IS-HPLC was performed on a qualified Agilent system (Agilent Infinity II) with connected radio detector (GABI, Raytest) and fraction collector (Agilent). The analysis of radiolysis products and uncomplexed Ac-225 was performed on a Waters XSelect CSH C18 XP, 150 x 2.1 mm, 2.5 pm column at a temperature of 50°C, with a gradient of ammonium formate, acetonitrile and DTPA. The entire run of HPLC was collected in a fraction collector into 1 min or 0.5 min fractions. After the Ac-225 / Fr-221 equilibrium was obtained (1 h after collecting the fractions), the Fr-221 gamma emission line was quantified in an HPGe gamma detector. Based on the Fr-221 activity in the collected fractions, the HPLC chromatogram was subsequently reconstructed and the radiochemical purity of the Ac-225-labeled compounds was determined. A distinction was made between uncomplexed "free"225Ac3+, "sum of impurities" and the molecular peak.

[0213] Activity measurements were performed in a qualified activimeter (ISOMED 2010, NUVIA Instruments GmbH). Gamma spectroscopic measurements were carried out on a nitrogen- cooled HPGe (high pure germanium) detector from ORTEC.

[0214] Buffer systems tested and results are shown below in Table 1 : Table 1 : Labeling yield and radiochemical purity (RCP) of Ac-225-DOTA-PSMA in different buffer systems

[0215] M: mo ar (mol / L); NaOAc: sodium acetate; EtOH: ethanol; Ac: Actinium-225; PSMA: Ibu- DAB-PSMA; EOS: end of synthesis; RAC: concentration of radioactivity; RCP: radiochemical purity; n. d.: not determined

[0216] The results of the labeling study shown in Table 1 indicate that a radiochemical purities of > 96% and free Ac content < 0.3% can be achieved at the end of the synthesis with a labeling buffer containing a 0.6 to 3 M sodium acetate solution (corresponding to 2.7 mg / MBq to 65.6 mg / MBq or 9.8 mg / mL to 98.4 mg / mL sodium acetate, respectively, and containing 5 to 30% ethanol (see labeling solutions # 1 .2 to 1 .7).

[0217] In comparison, a labeling solution comprising only NaOAc as a stabilizer (#1.8) provides <96% radiochemical activity and increased free Ac content (0.6%). Remarkably, a labeling solution comprising Na-ascorbate as stabilizer (# 1.9 to 1.1 1 ), or comprising NaOAc in combination with Na-ascorbate as stabilizers (#1.12 to 1.15) provided less favorable results with radiochemical purities of < 96% and free Ac of > 1.1 %.

[0218] Example 2: Protective effects of various formulations regarding auto-radiolysis of [225Ac]Ac-DOTA-PSMA

[0219] Next, various formulations of different kinds and concentrations were tested regarding the protective effects with regard to radiochemical stability of [225Ac]Ac-DOTA-PSMA (^Ac- labeled DOTA-lbu-DAB-PSMA) over a period of 48 hours.

[0220] To this end, the reaction mixtures from Example 1 (radiolabeled according to #1.7) were diluted with formulation buffer in the reaction vial, transferred to the product vial by sterile filtration, and the shelf life was determined in a stability study by regular analysis at predefined points in time (24 h, 48 h).

[0221] Formulations tested and results are shown below in Table 2. The conjugate used in the labeling and formulation studies was Ibu-DAB-PSMA (DOTA-lbu-DAB-PSMA). Table 2: Stability studies of [225Ac]Ac-DOTA-PSMA in different formulations, radiolabeled according to #1.7

[0222] M: molar (mol / L); NaOAc: sodium acetate; EtOH: ethanol; Ac: Actinium-225; PSMA: Ibu- DAB-PSMA; EOS: end of synthesis; RAC: concentration of radioactivity; RCP: radiochemical purity; n. d.: not determined The results shown in Table 2 indicate that considerable radiolysis is observed after 48h if the formulation does not contain ethanol (see # 2.8 and #2.9). In absence of ethanol, radiolysis is still considerable, in particular after 48h, even if the composition contains Na-ascorbate (see #2.8). In contrast thereto, if the composition comprises NaOAc and ethanol, a strong protective effect against radiolysis is observed (see #2.1 to 2.7), in particular at 48h, even in absence of Na-ascorbate in the composition (see #2.1 ). Example 3: Protective effects of various formulations comprising different concentrations of [225Ac]Ac-DOTA-PSMA

[0223] In this study, various formulations comprising different amounts of225Ac-labeled DOTA-PSMA (225Ac-labeled Ibu-DAB-PSMA) were tested regarding the protective effects with regard to radiochemical stability of [225Ac]Ac-DOTA-PSMA over a period up to 96 hours.

[0224] To this end, the reaction mixtures from example 1 (radiolabeled according to #1.7) were diluted with formulation buffer in the reaction vial, transferred to the product vial by sterile filtration, and the shelf life was determined in a stability study by regular analysis at predefined points in time (24 h, 48 h, 72h, 96h).

[0225] Formulations tested and results are shown in Table 3 below. Table 3: Stability studies of [225Ac] Ac-DOT A-PSMA in different formulations, radiolabeled according to #1.7

[0226] M: molar (mol / L); NaOAc: sodium acetate; EtOH: ethanol; Ac: Actinium-225; PSMA= Ibu- DAB-PSMA; EOS: end of synthesis; RAC: concentration of radioactivity; ART: activity reference time; RCP: radiochemical purity; n. d.: not determined

[0227] The results shown in Table 3 indicate that even with different concentrations of [225Ac]Ac- DOTA-PSMA a strong protective effect against radiolysis is observed up to 96 hours after the synthesis with a formulation containing NaOAc, ethanol and sodium ascorbate. In particular, a radiochemical purity of >95% is obtained with all tested formulation at 72 hours, and at 96 hours, still >94% (94.5%) radiochemical purity can be observed (see #3.4).

[0228] Example 4: Protective effects of various [225Ac] Ac-DOT A-PSMA formulations comprising different concentrations of radioactivity

[0229] In this study, various formulations comprising different concentrations of radioactivity were tested regarding the protective effects with regard to radiochemical stability of [225Ac]Ac- DOTA-PSMA (225Ac-labeled Ibu-DAB-PSMA) over a period up to 48 hours.

[0230] To this end, the reaction mixtures from example 1 (radiolabeled according to #1 .7) were diluted with formulation buffer in the reaction vial, transferred to the product vial by sterile filtration, and the shelf life was determined in a stability study by citrate TLC and HPLC-FC analysis at predefined points in time (24 h, 48 h).

[0231] Formulations tested and results are shown in Table 4 below. Table 4: Stability studies of [225Ac] Ac-DOT A-PSM A in formulations comprising different concentrations of radioactivity stored up to 48 hours at RT DAB-PSMA; EOS: end of synthesis; RAC: concentration of radioactivity; RCP: radiochemical purity

[0232] *AI I samples have the same EOS results, since they were diluted from a single bulk-labeling solution at the end of synthesis The results shown in Table 4 indicate that even with different concentrations of radioactivity, a strong protective effect against radiolysis is observed up to 48 hours after the synthesis with a formulation containing NaOAc, ethanol and sodium ascorbate. In particular, a radiochemical purity of >95% is obtained with all tested formulation at 48 hours, while the content of free (uncomplexed) Ac present in the final composition is < 0.9%.

[0233] Example 5: Protective effects of various formulations comprising further [225AclAc-labeled compounds

[0234] In this study, various formulations comprising different225Ac-labeled conjugates targeting PSMA (PSMA-I&T, PSMA-617), or targeting integrin (DOTA-RGD), or targeting the somatostatin receptor (JR1 1 , DOTATOC), respectively, were tested regarding the protective effects with regard to radiochemical stability of the225Ac-labeled conjugates over a period up to 72 hours.

[0235] To this end, radiolabeling of the different conjugates was performed as described in Example 1 (radiolabeled according to #1 .7), except that precursors of the respective conjugates (DOTA conjugates9 were used instead of the DOTA-PSMA precursor (DOTA-lbu-DAB-PSMA) used in Example 1 . The radiolabeled conjugates were diluted with formulation buffer in the reaction vial, transferred to the product vial by sterile filtration, and the shelf life was determined in a stability study by regular analysis at 72 hours.

[0236] Formulations tested and results are shown in Table 5 below.

[0237] Table 5: Stability studies of different [225Ac]Ac-labeled conjugates radiolabeled according to #1.7

[0238] M: molar (mol / L); NaOAc: sodium acetate; EtOH: ethanol; Ac: Actinium-225; EOS: end of synthesis; RAC: concentration of radioactivity; ART: activity reference time; RCP: radiochemical purity; n. d.: not determined The results shown in Table 5 indicate that even with different concentrations of radioactivity, a strong protective effect against radiolysis is still observed 72 hours after the synthesis with a formulation containing NaOAc, ethanol and sodium ascorbate. In particular, a radiochemical purity of >95% is obtained with all tested formulation at 72 hours. The content of free (uncomplexed) Ac present at the end of synthesis is < 0.5% for all tested formulations, and the content of free (uncomplexed) Ac in the final composition is still low (< 1 .4) after 72 h.

[0239] The radiolabeling and formulation methods of the present invention ensure a radiochemical yield of > 99% and a radiolysis stability of the [225Ac]Ac-labeled conjugate (targeting moiety covalently linked to a chelating moiety) with a radiochemical purity of > 94% over 72 hours in defined concentration ranges. This results in a high purity and a prolonged stability of a [225Ac]Ac-labeled radiopharmaceutical. Due to the prolonged stability of 72 h with consistently high quality, centralized production with subsequent distribution of the drug to the treatment centers can be guaranteed. In addition, there is no need to purify the labeled end product or to add weak complexing agents to the formulation.

Claims

CLAIMS1 . A pharmaceutical composition comprising(a) a radiolabeled complex comprising (i) an225Ac (Actinium-225) radionuclide, and (ii) a targeting moiety targeting the prostate specific membrane antigen (PSMA) or av03 integrin, covalently linked to a chelating moiety; and(b) a stabilizer against radiolytic degradation, wherein the stabilizer comprises sodium acetate (NaOAc) and ethanol (EtOH).

2. The pharmaceutical composition according to claim 1 , wherein the concentration of sodium acetate in the composition is in a range from 9 mg / mL to 100 mg / mL, preferably 15 mg / mL to 100 mg / mL, more preferably 20 mg / mL to 90 mg / mL, more preferably 30 mg / mL to 80 mg / mL, even more preferably 40 mg / mL to 70 mg / mL, still more preferably 50 mg / mL to 60 mg / mL or wherein the concentration of sodium acetate in the composition is in a range from 7 mg / mL to 20 mg / mL, preferably 7 mg / mL to 15 mg / mL, more preferably 9 mg / mL to 15 mg / mL or most preferably 7 mg / mL to 12 mg / mL.

3. The pharmaceutical composition according to any one of the previous claims, wherein the concentration of ethanol in the composition is in the range from 1 to 30 % (vol / vol), preferably 2 to 20% (vol / vol), more preferably 2 to 7 vol.%, even more preferably 3 to 5 vol.%, most preferably 3.5 to 4.5 vol.%.

4. The pharmaceutical composition according to any one of the previous claims, wherein the composition is an aqueous solution.

5. The pharmaceutical composition! according to any one of the previous claims, wherein the stabilizer additionally comprises ascorbic acid and / or a salt thereof.

6. The pharmaceutical composition according to claim 5, wherein the salt of ascorbic acid is sodium ascorbate.

7. The pharmaceutical composition according to any one of the previous claims, wherein the concentration of the salt of ascorbic acid, in particular sodium ascorbate, in thecomposition is below 40 mg / mL, preferably in the range of from 20 to 40 mg / mL, more preferably in the range of from 30 to 40 mg / mL.

8. The pharmaceutical composition according to any one of the previous claims, wherein the excipients of the pharmaceutical composition consist essentially of sodium acetate, ethanol, optionally sodium ascorbate, and water.

9. The pharmaceutical composition according to any one of the previous claims, wherein the composition comprises 9.0 mg / mL to 100 mg / mL NaOAc, 2 to 20 vol.% Ethanol and 0 to 40 mg / mL Na-Ascorbate.

10. The pharmaceutical composition according to any one of the previous claims, wherein (i) the composition comprises 7 mg / mL to 12 mg / mL NaOAc, 3 to 5 vol.% Ethanol, and 30 mg / mL to 40 mg / mL Na-Ascorbate, (ii) wherein the composition does not comprise a sequestering agent, and (iii) wherein the composition does not comprise any of gentisic acid or a salt thereof, methionine, histidine, melatonine, and Se-methionine.1 1 . The pharmaceutical composition according to any one of the previous claims, wherein the concentration of the targeting moiety linked to the chelating moiety in the composition is in the range from 10 to 150 nmol / mL, preferably 10 to 130 nmol / mL.

12. The pharmaceutical composition according to any one of the previous claims, wherein the concentration of the targeting moiety linked to the chelating moiety in the composition is in the range from 20 to 200 pg / mL, in particular 30 to 160 pg / mL.

13. The pharmaceutical composition according to any one of the previous claims, wherein the chelating moiety is DOTA or a derivative thereof.

14. The pharmaceutical composition according to any one of the previous claims, wherein the targeting moiety is selected from peptides, peptidomimetics, antibodies, antibody fragments, and antibody mimetics.

15. The pharmaceutical composition according to any one of the previous claims, wherein the radiolabeled complex comprises or consists of (i) the225Ac (Actinium-225) radionuclide and (ii) a DOTA-linked or DOTA derivative-linked peptide selected from the group consisting of PSMA-617, PSMA-I&T, Ibu-DAB-PSMA, and DOTA-RGD.

16. The pharmaceutical composition according to any one of the previous claims, wherein the radiolabeled complex comprises or consists of (i) the225Ac (Actinium-225) radionuclide and (ii) Ibu-DAB-PSMA, more preferably (5)-lbu-DAB-PSMA.

17. The pharmaceutical composition according to any one of the previous claims, wherein the225Ac radionuclide is present at a concentration providing volumetric radioactivity of 0.4 to 4.0 MBq / mL, preferably 1 to 4.0 MBq / mL or wherein the225Ac radionuclide is present at a concentration providing volumetric radioactivity of 0.2 to 2.0 MBq / mL, preferably 0.2 to 1 .0 MBq / mL, more preferably 0.3 to 0.8 MBq / mL, most preferably 0.35 to 0.45 MBq / mL.

18. The pharmaceutical composition according to any one of the previous claims, wherein (i) the composition comprises 7 mg / mL to 12 mg / mL NaOAc, 3 to 5 vol.% Ethanol, and 30 mg / mL to 40 mg / mL Na-Ascorbate, (ii) wherein the composition does not comprise a sequestering agent, (iii) wherein the composition does not comprise any of gentisic acid or a salt thereof, methionine, histidine, melatonine, and Se-methionine, and (iv) wherein the225Ac radionuclide is present at a concentration providing volumetric radioactivity of 0.3 to 0.8 MBq / mL, preferably 0.35 to 0.45 MBq / mL.

19. The pharmaceutical composition according to any one of the previous claims, wherein (i) the composition comprises 7 mg / mL to 12 mg / mL NaOAc, 3 to 5 vol.% Ethanol, and 30 mg / mL to 40 mg / mL Na-Ascorbate, (ii) wherein the composition does not comprise a sequestering agent, (iii) wherein the composition does not comprise any of gentisic acid or a salt thereof, methionine, histidine, melatonine, and Se-methionine, (iv) wherein the22SAc radionuclide is present at a concentration providing volumetric radioactivity of 0.3 to 0.8 MBq / mL, preferably 0.35 to 0.45 MBq / mL, and (v) wherein the radiolabeled complex comprises or consists of the225Ac (Actinium-225) radionuclide and Ibu-DAB-PSMA, more preferably (5)-lbu-DAB-PSMA.

20. The pharmaceutical composition according to any one of the previous claims, wherein the composition has a shelf life of at least 72 h.21 . The pharmaceutical composition according to any one of the previous claims, wherein the radiochemical purity of the composition is maintained at > 94% for at least 72 h.

22. The pharmaceutical composition according to any one of the previous claims, wherein the composition is provided in a volume of 1 to 10 mL.

23. The pharmaceutical composition according to any one of the previous claims, wherein a single dose allows delivery of 0.5 to 40 MBq± 10% of radioactivity at injection time, preferably of 1 to 20 MBq + 10% of radioactivity at injection time, more preferably of about 2 to 12 MBq ± 10% of radioactivity at injection time.

24. The pharmaceutical composition according to any one of the previous claims for use in medicine.

25. The pharmaceutical composition according to any one of the previous claims for use in the treatment of cancer.

26. A method for treating cancer or initiating, enhancing or prolonging an anti-tumor- response in a subject in need thereof comprising administering to the subject the pharmaceutical composition according to any one of claims 1 to 25.

27. A method for radiolabeling a targeting moiety covalently linked to a chelating moiety with 225-Actinium comprising the steps of(a) combining a225Ac radionuclide, a radiolabeling precursor comprising a targeting moiety covalently linked to a chelating moiety, and a radiolabeling buffer comprising sodium acetate and ethanol; and(b) heating the mixture for a predetermined period of time to obtain a225Ac-labeled complex comprising the225Ac radionuclide and the targeting moiety covalently linked to the chelating moiety.

28. A method for preparing a pharmaceutical composition comprising the following steps: (a') formation of a radiolabeled complex (radiolabeling) by heating a radiolabeling solution comprising (i) a225Ac (Actinium-225) radionuclide, (ii) a radiolabeling precursor comprising a targeting moiety covalently linked to a chelating moiety, and (iii) a radiolabeling buffer comprising sodium acetate (NaOAc) and ethanol for a defined period of time;(b1) formulating the pharmaceutical composition by adding a formulation buffer comprising water, in particular water for injection, sodium acetate and ethanol, and optionally comprising a salt of ascorbic acid, in particular Na-ascorbate; and(c') optionally sterile filtrating the obtained solution of the225Ac-labeled complex.

29. The method according to claim 27 or 28, wherein sodium acetate is present during step (a) and / or step (a1), respectively, at a concentration of 9 mg / mL to 100 mg / mL, preferably 10 mg / mL to 100 mg / mL, more preferably 20 mg / mL to 90 mg / mL, more preferably 30 mg / mL to 80 mg / mL, even more preferably 40 mg / mL to 70 mg / mL, still more preferably 50 mg / mL to 60 mg / mL.

30. The method according to any one of claims 27 to 29, wherein ethanol is present during step (a) and / or step (a'), respectively, at a concentration of 1 to 30 % (vol / vol), preferably 2 to 20% (vol / vol).

31. The method according to any one of claims 27 to 30, wherein the formation of a radiolabeled complex (radiolabeling) is performed in an aqueous solution.

32. The method according to any one of claims 27 to 31 , wherein the radiolabeling buffer does not comprise ascorbic acid or a salt thereof, preferably sodium ascorbate, and / or does not comprise gentisic acid or a salt thereof.

33. The method according to any one of claims 27 to 32, wherein the radiolabeling buffer consists essentially of sodium acetate, ethanol and water.

34. The method according to any one of claims 27 to 33, wherein in step (a) and (a'), respectively, the223Actinium radionuclide is present in the radiolabeling composition at a concentration providing volumetric radioactivity of 0.4 to 4.0 MBq / mL, preferably 1 to 4 MBq / mL, or 0.2 to 2.0 MBq / mL, preferably from 0.2 to 1 .0 MBq / mL.

35. The method according to any one of claims 27 to 34, wherein the targeting moiety linked to the chelating moiety is present in the radiolabeling composition at a concentration of 10 to 150 nmol / mL, preferably 10 to 130 nmol / mL.

36. The method according to any one of claims 27 to 35, wherein the radiolabeling buffer has a pH of about 6.0 to 9.0, preferably of about 7 to 8, more preferably of about 7.0.

37. The method according to any one of claims 27 to 36, wherein the radiolabeling of the precursor is performed at a temperature of 80°C to 95°C, preferably of 85°C to 90°C, more preferably of about 87°C.

38. The method according to any one of claims 27 to 37, wherein radiolabeling of the precursor is performed for 5 to 30 minutes, preferably 8 to 25 minutes.

39. The method according to any one of claims 28 to 38, wherein the formulation buffer added in step (b’) comprises a salt of ascorbic acid, in particular sodium ascorbate.

40. The method according to any one of claims 28 to 39, wherein the formulation buffer added in step (b1) essentially consists of water, in particular water for injection, sodium acetate, ethanol, and sodium ascorbate.

41. The method according to claim 39 or 40, wherein the formulation buffer comprising sodium ascorbate is added in an amount so that the concentration of sodium ascorbate in the composition is below 40 mg / mL, preferably from 20 to 40 mg / mL, more preferably from 30 to 40 mg / mL.

42. The method according to any one of claims 27 to 41, wherein the targeting moiety is selected from peptides, peptidomimetics, antibodies, antibody fragments, and antibody mimetics.

43. The method according to any one of claims 27 to 42, wherein the targeting moiety targets prostate specific membrane antigen (PSMA), integrin, or somatostatin receptor.

44. The method according to any one of claims 27 to 43, wherein the chelating moiety is DOTA or a derivative thereof.

45. The method according to any one of claims 27 to 44, wherein the radiolabeled complex comprises or consists of (i) the225Ac (Actinium-225) radionuclide and (ii) a DOTA-linked or DOTA derivative-l inked peptide selected from the group consisting of PSMA-I&T, PSMA-617, Ibu-DAB-PSMA, DOTA-RGD, DOTA-JR11, DOTATOC, and DOTATATE.

46. The method according to any one of claims 28 to 45, wherein the method is for preparing a pharmaceutical composition according to any one of claims 1 to 25.

47. A pharmaceutical composition obtained by the method according to any one of claims 27 to 46.

48. The pharmaceutical composition of claim 47, wherein the pharmaceutical composition is as defined in any one of claims 1 to 25.

Images