Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K51/00—Preparations containing radioactive substances for use in therapy or testing in vivo
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K51/00—Preparations containing radioactive substances for use in therapy or testing in vivo
  • A61K51/12—Preparations containing radioactive substances for use in therapy or testing in vivo characterised by a special physical form, e.g. emulsion, microcapsules, liposomes, characterized by a special physical form, e.g. emulsions, dispersions, microcapsules
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K51/00—Preparations containing radioactive substances for use in therapy or testing in vivo
  • A61K51/02—Preparations containing radioactive substances for use in therapy or testing in vivo characterised by the carrier, i.e. characterised by the agent or material covalently linked or complexing the radioactive nucleus
  • A61K51/04—Organic compounds
  • A61K51/08—Peptides, e.g. proteins, carriers being peptides, polyamino acids, proteins
  • A61K51/088—Peptides, e.g. proteins, carriers being peptides, polyamino acids, proteins conjugates with carriers being peptides, polyamino acids or proteins
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
  • A61P35/00—Antineoplastic agents

Definitions

• This invention relates to stabilizers that improve the radiostability of radiot-he-rapeutic and radiodiagnostic compounds, and formulations containing them.
• it relates to stabilizers useful in the preparation and stabilization of targeted radiodiagnostic and radiotherapeutic compounds, and, in a preferred embodiment, to the preparation and stab ⁇ li-J-ation of radiodiagnostic and radiotherapeutic compounds that are targeted to the Gastrm Releasing Peptide Receptor (GRP-Receptor).
• GRP-Receptor Gastrm Releasing Peptide Receptor
• Radiolabeled compounds designed for use as radiodiagnostic agents are generally prepared wi h a gar-c-raa-emitting isotope as the radiolabel. These gamma photons penetrate water and body tissues readily and can have a range in tissue or air of many centimeters-. In general-, such radiodiagnostic compounds do not cause significant damage to the organ systems that are imaged using these agents. This is because the gamma photons given off have no mass or charge and the amount of radioactive material that is injected is limited to the quantity required to obtain a diagnostic image, generally in the range of about 3 to 50 mCi, depending on the isotope and imaging agent used. This quantity is small enough to obtain useful images without significant radiation dose to the patient. Radionuclides such as 99 ⁇ n Tc, In, m l, 67 Ga and ⁇ Cu have been used for this purpose.
• radiolabeled compounds designed for use as radiotherapeutic agents are generally labeled with an Auger-, beta- or an alpha-emitting isotope, which may optionally also give off gamma photons, Radionuclides such as 9D Y, 177 Lu, 14J m, 153 Sm 4 l09 Pd, 67 Cu, l6e Ho, I, TMP, ,86 Re, 105 Rh, 21, At, ⁇ Ac, * 7 Sc, 213 Bi, and others, are potentially use&l for radiotherapy.
• Auger-, beta- or an alpha-emitting isotope which may optionally also give off gamma photons
• Radionuclides such as 9D Y, 177 Lu, 14J m, 153 Sm 4 l09 Pd, 67 Cu, l6e Ho, I, TMP, ,86 Re, 105 Rh, 21, At, ⁇ Ac, * 7 Sc, 213 Bi, and others, are potentially use&l
• the +3 metal ions of the lanthanide isotopes are of particular interest and include m Lu (relatively low energy ⁇ -emitter), z49 Pm, 153 Sm (medium energy) and 166 Ho (high energy).
• 90 Y also forms a +3 metal ion, and has coordination chemistry that is similar to that of the lanthanides.
• the coordination chemistry of the lanthanides is well developed and well known to those skilled in the art.
• the ionizing radiation given off from compounds labeled with these radioisotopes is of an appropriate energy to damage cells and tissue in sites where the radiolabelled compound has localized. The radiation emitted can either damage cellular components in the target tissue directly, or can cause water in tissues to form free radicals.
• Alpha particles dissipate a large amount of energy within one or two cell diameters, as their range of penetration in tissues is only ⁇ 50 ⁇ m. This can cause intense local damage, especially if the radiolabeled compound has been internalized into the nucleus of the cell.
• radiotherapeutic compounds labeled with Auger-electron emitters such las ' ⁇ In have a very short range and can have potent biological- effects at the desired site of action.
• the emissions from therapeutic beta-emitting isotopes such as 177 Lu or Y have somewhat longer ranges in tissue, but again, most of the damage produced occurs within a few millimeters or centimeters from the site of localization.
• radiolytic damage to the radiolabeled compound itself can be a serious problem during the preparation, purification, storage and/or shipping of a radiolabeled radiotherapeutic or radiodiagnostic compound, prior to its intended use.
• radiolytic damage can cause, for example, release of the radioisotope [e.g., by dehalogenation of radioiodinated antibodies or decomposition of the chelating moiety designed to hold the radiometal], or it can damage the targeting molecule that is required to deliver the targeted agent to its intended target.
• Both types of damage are highly undesirable as they can potentially cause the release of unbound isotope, e.g., free radioiodine or unchelated radiometal to the thyroid, bone and other organs, or cause a decrease or abolishment of targeting ability as a result of radiolytic damage to the targeting molecule, such as a receptor-binding region of a targeting peptide or radiolabeled antibody. Radioactivity that does not become associated with its target tissue may be responsible for unwanted side effects.
• Radiolytic damage to the methionine (Met) residue in these peptides is the most facile mode of decomposition, possibly resulting in a methionine sulfoxide derivative.
• Cell binding results show that the resulting radiolytically damaged derivatives are devoid of GRP-receptor binding activity (IC 50 values greater than micromolar).
• IC 50 values greater than micromolar.
• Preventing such radiolytic damage is a major challenge in the formulation of radiodiagnostic and radiotherapeutic compounds.
• compounds known as radical scavengers or antioxidants are typically used.
• 177 Lu, 2I2 Bi, 213 Bi, 68 Ga, 99m Tc, H 1 In and ]23 I can be stabilized by the addition of a hydrophilic thioether, and that the amino acid methionine, a hydrophilic thioether, is especially useful for this purpose.
• L-methionine 5 mg/mL was added to 177 Lu-A, to evaluate its ability to serve as a radical scavenger.
• reverse phase HPLC shows that after five days, almost complete decomposition of 177 Lu-A had occurred, indicating that the radiostabilizer used was insufficient to prevent radiolytic damage.
• the radical scavengers identified as a result of these studies have general utility in formulations for the preparation of compounds used for a variety of radiodiagnostic and radiotherapeutic applications, and may be useful to stabilize compounds radiolabeled with a variety of isotopes, e.g., 99m Tc, 186/188 Re, ⁇ ] In, 90 Y, I77 Lu, 213 Bi, 225 Ac, 166 Ho and others.
• the primary focus of the examples in this application is the radiostabilization of GRP -binding peptides, and in particular, the radioprotection of methionine residues in these molecules.
• the stabilizers identified should have applicability to a wide range of radiolabeled peptides, peptoids, small molecules, proteins, antibodies, and antibody fragments and the like. They are useful for the radioprotection of any compound that has a residue or residues that are particularly sensitive to radiolytic damage, such as, for example, tryptophan (oxidation of the indole ring), tyrosine (oxidative dimerization, or other oxidation), histidine, cysteine (oxidation of thiol group) and to a lesser extent serine, threonine, glutamic acid, and aspartic acid.
• tryptophan oxidation of the indole ring
• tyrosine oxidative dimerization, or other oxidation
• histidine cysteine (oxidation of thiol group) and to a lesser extent serine, threonine, glutamic acid, and aspartic acid.
• a radiolysis stabilizing solution containing a mixture of the following ingredients is added to the radiolabeled compound immediately following the radiolabeling reaction: gentisic acid, ascorbic acid, human serum albumin, benzyl alcohol, a physiologically acceptable buffer or salt solution at a pH of about 4.5 to about 8.5, and one or more amino acids selected from methionine, selenomethionine, selenocysteine, or cysteine).
• the physiologically acceptable buffer or salt solution is preferably selected from phosphate, citrate, or acetate buffers or physiologically acceptable sodium chloride solutions or a mixture thereof, at a molarity of from about 0.02M to about 0.2M.
• the reagent benzyl alcohol is a key component in this formulation and serves two purposes. For compounds that have limited solubility, one of its purposes is to solubilize the radiodiagnostic or radiotherapeutic targeted compound in the reaction solution, without the need for added organic solvents. Its second purpose is to provide a bacteriostatic effect. This is important, as solutions that contain the radiostabilizers of the invention are expected to have long post- reconstitution stability, so the presence of a bacteriostat is critical in order to maintain sterility.
• the amino acids methionine, selenomethionine, cysteine, and selenocysteine play a special role in preventing radiolytic damage to methionyl residues in targeted molecules that are stabilized with this radiostabilizing combination.
• M H + , Na + , K + , NH- + , M-methylglucamine, or other pharmaceutically acceptable +1 ions.
• M is a physiologically acceptable metal in the +2 oxidation state, such as Mg 2+ or Ca 2+
• Rl and R2 have the same definition as described above.
• formulations contain stabilizers that are water soluble organic selenium compounds wherein the selenium is in the oxidation state +2.
• stabilizers that are water soluble organic selenium compounds wherein the selenium is in the oxidation state +2.
• amino acid compounds selenomethionine, and selenocysteine and their esters and amide derivatives and dipeptides and tri peptides thereof which can either be added directly to the reaction mixture during radiolabeled complex preparation, or following complex preparation.
• the flexibility of having these stabilizers in the vial at the time of labeling or in a separate vial extends the utility of this invention for manufacturing radiodiagnostic or radiotherapeutic kits.
• selenium compounds in combination with sodium ascorbate or other pharmaceutically acceptable forms of ascorbic acid and its derivatives.
• the ascorbate is most preferably added after complexation is complete. Alternatively, it can be used as a component of the stabilizing formulation described above.
• a fourth approach involves the use of water soluble sulfur-containing compounds wherein the sulfur in the +2 oxidation state.
• Preferred thiol compounds include derivatives of cysteine, mercaptothanol, and di thiol threotol.
• reagents are particularly preferred due to their ability to reduce oxidized forms of methionine residues ⁇ e.g., methionine oxide residues) back to methionyl residues, thus restoring oxidative damage that has occurred as a result of "" " ⁇ " radiolysis.
• methionine residues e.g., methionine oxide residues
• the ascorbate is most preferably added after complexation is complete.
• the stabilizers and stabilizer combinations may be used to improve the radiolytic stability of targeted radiopharmaceuticals, comprising peptides, non-peptidic small molecules, radiolabeled proteins, radiolabeled antibodies and fragments thereof. These stabilizers are particularly useful with the class of GRP -binding compounds described herein. BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 shows the structure of Compound A.
• FIG. 2 shows the structure of Compound B.
• FIG. 3 illustrates the results of an HPLC analysis of a mixture of 177 Lu-A with
• FIG. 3A is a radiochromatogram of a reaction mixture for the preparation of 177 Lu-A, which was initially formed in >98% yield.
• FIG. 3B is radiochromatogram of [ 177 Lu-A], 25 mCi/mL, after five days at room temperature, demonstrating complete radiolytic destruction of the desired compound.
• the radiostabilizer added (5 mg/mL L-Methionine) was clearly insufficient for the level of radioprotection required.
• FIG. 4 is an HPLC trace [radiodetection] showing that 177 Lu-B (104 mCi) has
• FIG. 5 is an HPLC trace [radiodetection] showing that 177 Lu-A has >95% RCP for 5 days at a concentration of 55 mCi/2 mL if 1 mL of radiolysis protecting solution is added after the complex was formed.
• FIG. 6A and FIG. 6B show the structure of the methionine sulfoxide derivative of 177 Lu-A (FIG. 6A) and methionine sulfoxide derivative of ⁇ ⁇ In-B (FIG. 6B).
• FIG. 7A and FIG. 7B show stabilizer studies ,77 Lu-A (FIG. 7A) and 177 Lu-B (FIG. 7B). Radioactivity traces are shown from a study to compare the radiostabilizing effect of different amino acids, when added to ⁇ 7 Lu-A (FIG. 7A) and 177 Lu-B (FIG.
• Example 7B At an amino acid concentration of 6.6 mg/mL in 10 mM Dulbecco's phosphate buffered saline, pH 7.0 [PBS], and a radioactivity concentration of ⁇ 20 mCi/mL, after 48 hours of storage at room temperature. A total of 3.5 mCi of 177 Lu was added to each vial. A full description of the experimental procedure is given in Example 1.
• FIG. 8 shows an HPLC trace [radiodetection] showing the radiostability of
• FIG. 9 shows an HPLC trace [radiodetection] showing the stability of 177 Lu-B at a concentration of 50 mCi/2 mL in a radiolysis protecting solution containing L- ethionine. The details of this study are given in Example 4.
• FIGS. 10A-C show radiochromatograms and UN chromatograms comparing samples with and without 1 -pyrrolidine dithiocarbamic acid ammonium salt in the reaction buffer and containing zinc as a contaminant metal during the reaction of 177 Lu-B.
• the experimental procedure for this study is given in Example 20.
• the isotope is a non-metal, such as 123 1, 131 I or F, and is either coupled directly to the rest of the molecule or is bound to a linker.
• a metal chelator refers to a molecule that forms a complex with a metal atom.
• a metal chelator is a molecule that complexes to a radionuclide metal to form a metal complex that is stable under physiological conditions and which also has at least one reactive functional group for conjugation with a targeting molecule, a spacer, or a linking group, as defined below.
• the metal chelator M may >e any of the metal chelators known in the art for complexing a.medically useful metal ion or radionuclide.
• the metal chelator may or may not be complexed with a metal radionuclide.
• the metal chelator can include an optional spacer such as a single amino acid ⁇ e.g., Gly) which does not complex with the metal, but which creates a physical separation between the metal chelator and the linker.
• the metal chelators of the invention may include, for example, linear, macrocyclic, terpyridine, and N 3 S, N 2 S 2 , or N chelators ⁇ see also, U.S. 4,647,447, U.S.
• the chelator may also include derivatives of the chelating ligand mercapto-acetyl-glycyl-glycyl-glycine (MAG3), which contains an N 3 S, and N 2 S 2 systems such as MAMA (monoamidemonoaminedithiols), DADS (N 2 S diaminedithiols), COD ADS and the like.
• MAG3 chelating ligand mercapto-acetyl-glycyl-glycyl-glycine
• MAMA monoamidemonoaminedithiols
• DADS N 2 S diaminedithiols
• COD ADS COD ADS
• the metal chelator may also include complexes known as boronic acid adducts of technetium and rhenium dioximes, such as those described in U.S. Patent Nos. 5,183,653; 5,387,409; and 5,118,797, the disclosures of which are incorporated by reference herein, in their entirety.
• Examples of preferred chelators include, but are not limited to, derivatives of diethylenetriamine pentaacetic acid (DTPA), l,4,7,10-tetraazacyclotetradecane-l,4,7,10-tetraacetic acid (DOTA), 1 -substituted 1,4,7,- tricarboxymethyl 1,4,7,10 tetraazacyclododecane triacetic acid (DO3A), derivatives of the 1- l-(l-carboxy-3-(p-nitrophenyl)propyl-l,4,7,10 tetraazacyclododecane triacetate (PA-DOTA) and MeO-DOTA, ethylenediaminetetraacetic acid (EDTA), and 1,4,8,11- tetraazacyclotetradecane-1, 4,8,11 -tetraacetic acid (TETA), derivatives of 3,3,9,9- Tetramethyl-4,8-diazaundecane-2,10
• Additional chelating ligands are ethylenebis-(2-hydroxy-phenylglycine) (EHPG), and derivatives thereof, including 5-C1-EHPG, 5-Br-EHPG, 5-Me-EHPG, 5-t-Bu-EHPG, and 5-sec-Bu-EHPG; benzodiethylenetriamine pentaacetic acid (benzo-DTPA) and derivatives thereof, including dibenzo-DTPA, phenyl-DTPA, diphenyl-DTPA, benzyl-DTPA, and dibenzyl-DTPA; bis-2 (hydroxybenzyl)-ethylene-diaminediacetic acid (HBED) and derivatives thereof; the class of macrocyclic compounds which contain at least 3 carbon atoms, more preferably at least 6, and at least two heteroatoms (O and/or N), which macrocyclic compounds can consist of one ring, or two or three rings joined together at the hetero ring elements, e.g., benzo-DOTA, dibenzo-DOTA,
• chelators and chelating groups contemplated by the present invention are described in WO 98/18496, WO 86/06605, WO 91/03200, WO 95/28179, WO 96/23526, WO 97/36619, PCT/US98/01473, PCT/US98/20182, and U.S. 4,899,755, U.S. 5,474,756, U.S. 5,846,519 and U.S. 6,143,274, each of which is hereby incorporated by reference in its entirety.
• Particularly preferred metal chelators include those of Formula 1, 2 and 3a and
• Specific metal chelators of Formula 6 include N,N-dimethylGly-Ser-Cys; N,N-dimethylGly- Thr-Cys; N,N-diethylGly-Ser-Cys; N,N-dibenzylGly-Ser-Cys; and other variations thereof.
• Spacers which do not actually complex with the metal radionuclide such as an extra single amino acid Gly maybe attached to these metal chelators ⁇ e.g., N,N-dimethylGly-Ser-Cys- Gly; N,N-dimethylGly-Thr-Cys-Gly; N,N-diethylGly-Ser-Cys-Gly; N,N-dibenzylGly-Ser- Cys-Gly).
• Other useful metal chelators such as all of those disclosed in U.S. Pat. No.
• 6,334,996 are also incorporated by reference ⁇ e.g., Dimethyl gly-L-t-Butylgly-L-Cys-Gly; Dimethylgly-D-t-Butylgly-L-Cys-Gly; Dimethylgly-L-t-Butylgly-L-Cys, etc.).
• sulfur protecting groups such as Acm (acetamidomethyl), trityl or other known alkyl, aryl, acyl, alkanoyl, aryloyl, mercaptoacyl and organothiol groups may be attached to the cysteine amino acid of these metal chelators.
• useful metal chelators include:
• R is hydrogen or alkyl, preferably methyl.
• R_ and R 2 are as defined in U.S. 6,143,274, incorporated by reference herein its entirety.
• X is either CH 2 or O
• Y is either branched or unbranched alkyl
• Y is aryl, aryloxy, arylamino, arylaminoacyl
• Y is arylalkyl - where the alkyl group or groups attached to the aryl group are C]-C J O branched or unbranched alkyl groups, C]-Cio branched or unbranched hydroxy or polyhydroxyalkyl groups or polyalkoxyalkyl or polyhydroxy-polyalkoxyalkyl groups
• the metal chelator includes cyclic or acyclic polyaminocarboxylic acids such as DOTA (1,4,7,10-tetraazacyclododecane -1,4,7,10- tetraacetic acid), DTPA (diethylenetriaminepentaacetic acid), DTPA-bismethylamide, DTPA- bismorpholineamide, DO3A N-[[4,7, 10-Tris(carboxymethyl)-1 ,4,7, 10-tetraazacyclododec-l - yl]acetyl], HP-DO3A, DO3A-monoamide and derivatives thereof.
• DOTA 1,4,7,10-tetraazacyclododecane -1,4,7,10- tetraacetic acid
• DTPA diethylenetriaminepentaacetic acid
• DTPA-bismethylamide DTPA- bismorpholineamide
• chelating ligands encapsulate the radiometal by binding to it via multiple nitrogen and oxygen atoms, thus preventing the release of free (unbound) radiometal into the body. This is important, as in vivo dissociation of 3 radiometals from their chelate can result in uptake of the radiometal in the liver, bone and spleen [Brechbiel MW, Gansow OA, "Backbone-substituted DTPA ligands for 90 Y radioimmunotherapy", Bioconj. Chem.
• Radioisotopes Preferred radionuclides for scintigraphy or radiotherapy include 99 Tc, 67 Ga,
• the choice of isotope will be determined based on the desired therapeutic or diagnostic application.
• the preferred radionuclides include 64 Cu, 67 Ga, 68 Ga, 99m Tc, and m In, with 99m Tc and I U In being especially preferred.
• the preferred radionuclides include 4 Cu, 90 Y, ,05 Rh, n , In, , ]7ra Sn, 149 Pm, ,53 Sm, 161 Tb, ]66 Dy, ,66 Ho, ,75 Yb, ,77 Lu, , 86/188 Re, and ,99 Au, with ⁇ 7 Lu and 90 Y being particularly preferred.
• 99m Tc is particularly useful and is a preferred diagnostic radionuclide because of its low cost, availability, imaging properties, and high specific activity.
• This isotope has a single photon energy of 140 keV and a radioactive half-life of about 6 hours, and is readily available from a 99 Mo- 99m Tc generator.
• ⁇ 'in is also particularly preferred diagnostic isotope, as this +3 metal ion has very similar chemistry to that of the radiotherapeutic +3 lanthanides, thus allowing the preparation of a diagnostic/therapeutic In/ Lu pair.
• Peptides labeled with Lu, r or other therapeutic radionuclides can be used to provide radiotherapy for primary tumors and metastasis related to cancers of the prostate, breast, lung, etc., and H 1 In analogs can be used to detect the presence of such tumors.
• the selection of a proper nuclide for use in a particular radiotherapeutic application depends on many factors, including:
• Radionuclide should have a physical half-life between about 0.5 and 8 days.
• Radionuclides that are particle emitters are particularly useful, as they emit highly energetic particles that deposit their energy over short distances, thereby producing highly localized damage.
• Beta emitting radionuclides are particularly preferred, as the energy from beta particle emissions from these isotopes is deposited within 5 to about 150 cell diameters.
• Radiotherapeutic agents prepared from these nuclides are capable of killing diseased cells that are relatively close to their site of localization, but cannot travel long distances to damage adjacent normal tissue such as bone marrow.
• Radionuclides that have high specific activity are particularly preferred.
• the specific activity of a radionuclide is determined by its method of production, the particular target that is used to produce it, and the properties of the isotope in question. 3. Linking Groups
• linker and “linking group” are used synonymously herein to refer to any chemical group that serves to couple the targeting molecule to the metal chelator while not adversely affecting either the targeting function of the targeting molecule or the metal complexing function of the metal chelator.
• Linking groups may optionally be present in the stabilized radiopharmaceutical formulations of the invention.
• Suitable linking groups include peptides ⁇ i.e., amino acids linked together) alone, a non-peptide group ⁇ e.g., hydrocarbon chain) or a combination of an amino acid sequence and a non-peptide spacer.
• the linking group includes L-glutamine and a hydrocarbon chain, or a combination thereof.
• the linking group includes a pure peptide linking group consisting of a series of amino acids ⁇ e.g., diglycine, triglycine, gly-gly-glu, gly-ser- gly, etc.), in which the total number of atoms between the N-terminal residue of the targeting molecule and the metal chelator in the polymeric chain is ⁇ 12 atoms.
• Rj is a group ⁇ e.g., H 2 N-, HS-, -COOH
• R is a group that is used for covalent coupling to the targeting molecule ⁇ e.g., to the N-terminal NH 2 -group of a targeting peptide ⁇ e.g., R
• the linking group is of the formula
• N-O-P contains at least one non-alpha amino acid.
• N is 0 (where 0 means it is absent), an alpha or non-alpha amino acid or other linking group; O is an alpha or non-alpha amino acid; and P is 0, an alpha or non-alpha amino acid or other linking group, wherein at least one of N, O or P is a non-alpha amino acid.
• N Gly
• O a non-alpha amino acid
• P 0.
• Alpha amino acids are well known in the art, and include naturally occurring and synthetic amino acids. Non-alpha amino acids also include those which are naturally occurring or synthetic.
• the linker is of the formula N- O-P and contains at least one substituted bile acid.
• N is 0 (where 0 means it is absent), an alpha amino acid, a substituted bile acid or other linking group
• O is an alpha amino acid or a substituted bile acid
• P is 0, an alpha amino acid, a substituted bile acid or other linking group, wherein at least one of N, O or P is a substituted acid.
• Bile acids are found in bile (a secretion of the liver) and are steroids having a hydroxy] group and a five carbon atom side chain terminating in a carboxyl group.
• substituted bile acids at least one atom such as a hydrogen atom of the bile acid is substituted with another atom, molecule or chemical group.
• substituted bile acids include those having a 3-amino, 24-carboxyl function optionally substituted at positions 7 and 12 with hydrogen, hydroxyl or keto functionality.
• substituted bile acids in the present invention include substituted cholic acids and derivatives thereof.
• Specific substituted cholic acid derivatives include: (3 ⁇ ,5 ⁇ )-3-aminocholan-24-oic acid; (3 ⁇ ,5 ⁇ ,12 ⁇ )-3-amino-12-hydroxycholan-24-oic acid; (3 ⁇ ,5 ⁇ ,7 ⁇ ,12 ⁇ )-3-amino-7,12-dihydroxycholan-24-oic acid; Lys-(3,6,9)-trioxaundecane-l ,11 -dicarbonyl-3,7-dideoxy- 3-aminocholic acid); (3 ⁇ ,5 ⁇ ,7 ⁇ )-3-amino-7-hydroxy-12-oxocholan-24-oic acid; and (3 ⁇ ,5 ⁇ ,7 ⁇ )-3-amino-7-hydroxycholan-24-oic acid.
• linker N-O-P contains at least one non-alpha amino acid with a cyclic group.
• N is 0 (where 0 means it is absent), an alpha amino acid, a non-alpha amino acid with a cyclic group or other linking group;
• O is an alpha amino acid or a non-alpha amino acid with a cyclic group; and
• P is 0, an alpha amino acid, a non-alpha amino acid with a cyclic group, or other linking group, wherein at least one of N, O or P is a non-alpha amino acid with a cyclic group.
• Non-alpha amino acids with a cyclic group include substituted phenyl, biphenyl, cyclohexyl or other amine and carboxyl containing cyclic aliphatic or heterocyclic moieties.
• Examples of such include: 4-aminobenzoic acid 4-aminomethyl benzoic acid trans-4-aminomethylcyclohexane carboxylic acid 4-(2-aminoethoxy)benzoic acid isonipecotic acid 2-aminomethylbenzoic acid 4-amino-3-nitrobenzoic acid 4-(3-carboxymethyl-2-keto- 1 -benzimidazolyl-piperidine 6-(piperazin-l -yl)-4-(3H)-quinazolinone-3-acetic acid (2S,5S)-5-amino-l,2,4,5,6,7-hexahydro-5-amino-l,2,4,5,6,7-hexahydro azepino[3,2,l -hi
• Any molecule that specifically binds to or reactively associates or complexes with a receptor or other receptive moiety associated with a given target cell population may be used as a targeting molecule in radiopharmaceutical formulations of the invention.
• This cell reactive molecule to which the metal chelator is linked optionally via a linking group, may be any molecule that binds to, complexes with or reacts with the cell population sought to be bound or localized to.
• the cell reactive molecule acts to deliver the radiopharmaceutical to the particular target cell population with which the molecule reacts.
• the targeting molecule may be non-peptidic such as, for example, steroids, carbohydrates, or small non-peptidic molecules.
• the targeting molecule may also be an antibody, such as, for example, a monoclonal or polyclonal antibody, a fragment thereof, or a protein, including , for example, derivatives of Annexin, anti-CEA, Tositumomab, HUA33, Epratuzumab, cG250, human serum albumin, Ibritumomab Tiuxetan and the like.
• the targeting molecule is a peptide, peptide mimetic or peptoid. Most preferably the targeting molecule is a peptide (a "targeting peptide").
• the targeting molecule used in a radiopharmaceutical formulation of the invention is a biologically active peptide.
• the targeting molecule is a peptide that binds to a receptor or enzyme of interest.
• the targeting molecule may be a peptide hormone such as, for example, luteinizing hormone releasing hormone (LHRH) such as that described in the literature ⁇ e.g., Radiometal -Binding Analogues of Luteinizing Hormone Releasing Hormone PCT/US96/08695; PCT/US97/12084 (WO 98/02192)); insulin; oxytocin; so atostatin; Neuro kinin-1 (NK-1); Nasoactive Intestinal Peptide (VIP) including both linear and cyclic versions as delineated in the literature, [e.g., Comparison of Cyclic and Linear Analogs of Vasoactive Intestinal Peptide. D. R. Bolin, J. M.
• LHRH luteinizing hormone releasing hormone
• Other useful targeting molecules include analogues of somatostatin which, for example, are Lanreotide ( ⁇ al-Cys-Thr-DTrp-Lys-Val-Cys-Thr- ⁇ H 2 ), Octreotide (Nal-Cys- Thr-DT -Lys-Val-Cys-Thr-ol), and Maltose-(Phe-Cys-Thr-DT ⁇ -Lys-Nal-Cys-Thr-ol).
• Lanreotide ⁇ al-Cys-Thr-DTrp-Lys-Val-Cys-Thr- ⁇ H 2
• Octreotide Nal-Cys- Thr-DT -Lys-Val-Cys-Thr-ol
• Still other useful targeting molecules include Substance P agonists [e.g., G.
• G Protein Antagonists A novel hydrophobic peptide competes with receptor for G protein binding, Hidehito Mukai, Eisuke Munekata, Tsutomu Higashijima, J. Biol. Chem.
• ⁇ PY(Yl) e.g., Novel Analogues of Neuropeptide Y with a Preference for the Yl -receptor, Richard M. Soil, Michaela, C.umbler, Ingrid Lundell, Dan Larhammer, Annette G. Beck-Sickinger, Eur. J. Biochem. 2001, 268, 2828-2837; 99 Tc-Labeled Neuropeptide Y Analogues as Potential Tumor Imaging Agents, Michael Langer, Roberto La Bella, Elisa Garcia-Garayoa, Annette G. Beck-Sickinger,
• Bioconjugate Chem. 2001, 12, 1028-1034 Novel Peptide Conjugates for Tumor-Specific Chemotherapy, Michael Langer, Felix Kratz, Barbara Rothen-Rutishauser, Heidi Wnderli- A-llenspach, Annette G. Beck-Sickinger, J. Med. Chem. 2001, 44, 1341-1348]; oxytocin; endothelin A and endothelin B; bradykinin; Epidermal Growth Factor (EGF); Interleukin-1 [Anti-IL-1 Activity of Peptide Fragments of IL-1 Family Proteins, I. Z. Siemion, A.
• TGF tumor growth factors
• NGF tumor growth factors
• IGF insulin-like growth factors
• IGF insulinlike growth factor
• peptides targeting receptors which are upregulated in angiogenesis such as NEGF receptors ⁇ e.g., KDR, ⁇ P-1, etc.
• RGD-containing peptides melanocyte-stimulating hormone (MSH) peptide
• neurotensin calcitonin
• peptides from complementarity determining regions of an antitumor antibody glutathione
• YIGSR leukocyte-avid peptides, e.g., P483H, which contains the heparin-binding region of platelet factor-4 (PF-4) and a lysine-rich sequence
• analogues include molecules that target a desired site receptor with avidity that is greater than or equal to the targeting molecule itself.
• analogues include muteins, retropeptides and retro-inverso-peptides of the targeting peptide.
• modifications which include substitutions, and/or deletions and/or additions of one or several amino acids, insofar that these modifications do not negatively alter the biological activity of the targeting molecules.
• substitutions in targeting peptides may be carried out by replacing one or more amino acids by their synonymous amino acids. Synonymous amino acids within a group are defined as amino acids that have sufficient physicochemical properties to allow substitution between members of a group in order to preserve the biological function of the molecule.
• amino acids as used herein include synthetic derivatives of these amino acids (such as for example the D-forms of amino acids and other synthetic derivatives), and, the D- forms of amino acids and other synthetic derivatives).
• amino acids are abbreviated interchangeably either by their three letter or single letter abbreviations, which are well known to the skilled artisan.
• T or Thr stands for threonine
• K or Lys stands for lysine
• P or Pro stands for proline
• R or Arg stands for arginine.
• Deletions or insertions of amino acids may also be introduced into the defined sequences of targeting peptides provided they do not alter the biological functions of said sequences.
• insertions or deletions should be limited to 1, 2, 3, 4 or 5 amino acids and should not remove or physically disturb or displace amino acids which are critical to the functional conformation.
• Muteins of targeting peptides or polypeptides may have a sequence homologous to the original targeting peptide sequence in which amino acid substitutions, deletions, or insertions are present at one or more amino acid positions.
• Muteins may have a biological activity that is at least 40%, preferably at least 50%, more preferably 60-70%, most preferably 80-90% of the original targeting peptide. However, they may also have a biological activity greater than the. original targeting peptide, and thus do not necessarily have to be identical to the biological function of the original targeting peptides.
• -Analogues of targeting peptides also include peptidomimetics or pseudopeptides inco ⁇ orating changes to the amide bonds of the peptide backbone, including thioamides, methylene amines, and E-olefins. Also molecules based on the structure of a targeting peptide or its analogues with amino acids replaced by N-substituted hydrazine carbonyl compounds (also known as aza amino acids) are included in the term analogues as used herein.
• a targeting peptide may be attached to a linker via the N or C terminus or via attachment to the epsilon nitrogen of lysine, the gamma nitrogen or ornithine or the second carboxyl group of aspartic or glutamic acid.
• the targeting molecule is a gastrin releasing peptide (GRP) receptor targeting molecule.
• GRP receptor-targeting molecule is a molecule that specifically binds to or reactively associates or complexes with one or more members of the GRP receptor family. In other words, it is a molecule which has a binding affinity for the GRP receptor family.
• the targeting molecule is a GRP receptor targeting peptide ⁇ e.g., a peptide, equivalent, analogue or derivative thereof with a binding affinity for one or more members of the GRP receptor family).
• the GRP receptor targeting molecule may take the form of an agonist or an antagonist.
• a GRP receptor targeting molecule agonist is known to "activate" the cell following binding with high affinity and may be internalized by the cell.
• GRP receptor targeting molecule antagonists are known to bind only to the GRP receptor on the cell without stimulating internalization by the cell and without “activating" the cell.
• the GRP receptor targeting molecule is an agonist and more preferably it is a peptide agonist.
• the GRP agonist is a bombesin (BBN) analogue and/or a derivative thereof.
• BBN derivative or analog thereof preferably contains either the same primary structure of the BBN binding region ⁇ i.e., BBN(7-14) [SEQ ID NO:l]) or similar primary structures, with specific amino acid substitutions that will specifically bind to GRP receptors with better or similar binding affinities as BBN alone ⁇ i.e., Kd ⁇ 25nM).
• Suitable compounds include peptides, peptidomimetics and analogues and derivatives thereof.
• the presence of L-methionine (Met) at position BBN-14 will generally confer agonistic properties while the absence of this residue at BBN-14 generally confers antagonistic properties [Hoffken, 1994].
• Analogues of BBN receptor targeting molecules include molecules that target the GRP receptors with avidity that is greater than or equal to BBN, as well as muteins, retropeptides and retro-inverso-peptides of GRP or BBN.
• analogues may also contain modifications which include substitutions, and/or deletions and/or additions of one or several amino acids, insofar that these modifications do not negatively alter the biological activity of the peptides described therein. These substitutions may be carried out by replacing one or more amino acids by their synonymous amino acids.
• the stabilizers of the present invention may also be used for compounds that do not have a distinct targeting or linking group, and wherein the metal/chelator combination alone provides targeting to the desired organ or organ system.
• the stabilizers described here have potential utility in the stabilization of compounds such as Ho- DOTMP, 188 Re-HEDTMP, 153 Sm-EDTMP, 99m Tc-MDP and the like, all of which target bone. 5. Labeling And Administration Of Compounds
• Inco ⁇ oration of the radioisotope within the stabilized conjugates of this invention can be achieved by various methods commonly known in the art of coordination chemistry. Where inco ⁇ oration of, for example, 1 H In or 177 Lu is desired, the methods set forth in the Examples may be used. When the metal is 99m Tc, a preferred radionuclide for diagnostic imaging, the following general procedure can be used to form a technetium complex.
• a peptide-chelator conjugate solution is formed by initially dissolving the conjugate in an aqueous solution of dilute acid, base, salt or buffer, or in an aqueous solution of an alcohol such as ethanol. The solution is then optionally degassed to remove dissolved oxygen.
• a thiol protecting group such as Acm (acetamidomethyl), trityl or other thiol protecting group may optionally be used to protect the thiol from oxidation.
• the thiol protecting group(s) are removed with a suitable reagent, for example with sodium hydroxide, and are then neutralized with an organic acid such as acetic acid.
• the thiol protecting group can be removed in situ during technetium chelation.
• sodium pertechnetate obtained from a molybdenum generator is added to a solution of the conjugate with a sufficient amount of a reducing agent, such as stannous chloride, to reduce technetium and is either allowed to stand at room temperature or is heated.
• a reducing agent such as stannous chloride
• the labeled conjugate can be separated from the contaminants ra TcO " and colloidal 99m TcO 2 chromatographically, for example with a C-18 Sep Pak cartridge [Millipore Co ⁇ oration] or by HPLC using methods known to those skilled in the art.
• the labeling can be accomplished by a transchelation reaction.
• the technetium source is a solution of technetium that is reduced and complexed with labile ligands prior to reaction with the selected chelator, thus facilitating ligand exchange with the selected chelator.
• suitable ligands for transchelation includes tartrate, citrate, gluconate, and heptagluconate.
• the conjugate can be labeled using the techniques described above, or alternatively, the chelator itself may be labeled and subsequently coupled to the peptide to form the conjugate; a process referred to as the "prelabeled chelate" method.
• Re and Tc are both in row VIIB of the Periodic Table and they are chemical congeners.
• the complexation chemistry of these two metals with ligand frameworks that exhibit high in vitro and in vivo stabilities are the same [Eckelman, 1995] and similar chelators and procedures can be used to label with Re.
• the stabilized radiopharmaceuticals and radiopharmaceutical formulations of the present invention can be used to image or deliver radiotherapy to selected tissues. In a preferred embodiment, they may be used to treat and/or detect cancers, including tumors, by procedures established in the art of radiodiagnostics and radiotherapeutics. [Bushbaum, 1995; Fischman et al., 1993; Schubiger et al., 1996; Lowbertz et al., 1994; Krenning et al., 1994]. [0089] Indeed the stabilized radiopharmaceutical formulations of the examples are able to target GRP receptor expressing tissues, including tumors and thus to image or deliver radiotherapy to these tissues.
• GRP receptors are well documented to be over-expressed in a number of cancer types such as prostate, breast and small cell ' lung cancer, a radiodiagnostic or radiotherapeutic agent that targets such receptors has the potential to be widely useful for the diagnosis or treatment of such cancers.
• the diagnostic application of the stabilized radiopharmaceuticals of the invention can be as a first line diagnostic screen for the presence of a disease state such as, for example, neoplastic cells using scintigraphic imaging, as an agent for targeting particular tissues ⁇ e.g., neoplastic tissue) using hand-held radiation detection instrumentation in the field of radio guided surgery (RIGS), as a means to obtain dosimetry data prior to administration of the matched pair radiotherapeutic compound, and as a means to assess, for example, receptor population as a function of treatment over time.
• a disease state such as, for example, neoplastic cells using scintigraphic imaging, as an agent for targeting particular tissues ⁇ e.g., neoplastic tissue
• RIGS radio guided surgery
• the therapeutic application of the stabilized radiopharmaceuticals of the invention can be as an agent that will be used as a monotherapy in the treatment of a disease, such as cancer, as combination therapy where these radiolabeled agents could be utilized in conjunction with adjuvant chemotherapy, and as the matched pair therapeutic agent.
• the matched pair concept refers to a single unlabeled compound which can serve as both a diagnostic and a therapeutic agent depending on the radioisotope that has been selected for binding to the appropriate chelate. If the chelator cannot accommodate the desired metals appropriate substitutions can be made to accommodate the different metal whilst maintaining the pharmacology such that the behaviour of the diagnostic compound in vivo can be used to predict the behaviour of the radiotherapeutic compound.
• the stabilized compounds and formulations of the present invention can be administered to a patient alone or as part of a composition that contains other components such as excipients, diluents, and carriers, all of which are well-known in the art.
• the compounds can be administered to patients intravenously, subcutaneously, intra-arterially, intraperitoneally, intratumorally or by installation into resection cavities in, e.g., the brain.
• Stabilized radiolabeled scintigraphic imaging agents provided by the present invention are provided having a suitable amount of radioactivity.
• radioactive complexes in solutions containing radioactivity at concentrations of from about 0.01 millicurie (mCi) to 100 mCi per mL.
• the unit dose to be administered has a radioactivity of about 0.01 mCi to about 100 mCi, preferably 1 mCi to 30 mCi.
• the solution to be injected at unit dosage is from about 0.01 mL to about 10 mL.
• the unit dose to be administered typically ranges from about 0.01 mCi to about 10 mCi, preferably 3 to 6 mCi for diagnostic applications, and from 10 mCi to about 2 Curies for radiotherapeutic applications, preferably ,30 mCi to 800 mCi.
• the unit dose to be administered typically ranges from about 10 mCi to about 200 mCi, preferably from about 100 to about 200 mCi.
• the amount of labeled conjugate appropriate for administration is dependent upon the distribution profile of the chosen conjugate in the sense that a rapidly cleared conjugate may need to be administered in higher doses than one that clears less rapidly.
• In vivo distribution and localization can be tracked by standard scintigraphic techniques at an appropriate time subsequent to administration; typically between thirty minutes and 180 minutes depending upon the rate of accumulation at the target site with respect to the rate of clearance at non-target tissue.
• a gamma camera calibrated for the gamma ray energy of the nuclide inco ⁇ orated in the imaging agent can be used to image areas of uptake of the agent and quantify the amount of radioactivity present in the site. Imaging of the site in vivo can take place in a few minutes. However, imaging can take place, if desired, hours or days after the radiolabeled compound is injected into a patient.
• the compounds made in accordance with the present invention form stable, well-defined ⁇ ⁇ In or 7 Lu labeled compounds. Similar stabilized compounds and formulations of the invention can also be made by using appropriate chelator frameworks for the respective radiometals, to form stable, well-defined products labeled with 153 Sm, 90 Y, ,66 Ho, J05 Rh, )99 Au, 149 Pm, 99m Tc, 186/18 ⁇ Re or other radiometal.
• the stabilized radiolabeled GRP receptor targeting peptides selectively bind to neoplastic cells expressing GRP receptors, and if an agonist is used, become internalized, and are retained in the tumor cells for extended time periods. Because of the high radiostability obtained, the radioactive formulations do not undergo significant decompositon, and thus can be prepared at, for example, a central radiolabeling facility and then shipped to distant sites without significant decomposition and loss of targeting ability.
• Radioisotope therapy involves the administration of a radiolabeled compound in sufficient quantity to damage or destroy the targeted tissue.
• the stabilized -radiolabeled pharmaceutical localizes preferentially at the disease site ⁇ e.g., tumor tissue that expresses a member of the GRP receptor family). Once localized, the radiolabeled compound then damages or destroys the diseased tissue with the energy that is released during the radioactive decay of the isotope that is administered.
• the design of a successful radiotherapeutic involves several critical factors: 1. selection of an appropriate targeting group to deliver the radioactivity to the disease site; 2. selection of an appropriate radionuclide that releases sufficient energy to damage that disease site, without substantially damaging adjacent normal tissues; and 3. selection of an appropriate combination of the targeting group and the radionuclide without adversely affecting the ability of this conjugate to localize at the disease site. For radiometals, this often involves a chelating group that coordinates tightly to the radionuclide, combined with a linker that couples said chelate to the targeting group, and that affects the overall biodistribution of the compound to maximize uptake in target tissues and minimize uptake in normal, non-target organs. 4. Selection of appropriate radiostabilizers such that once formed, the radiotherapeutic compound does not undergo significant radiolytic decomposition prior to administration.
• the present invention provides stabilized radiotherapeutic agents that satisfy all of the above criteria, through proper selection of stabilizer or stabilizers, targeting group, radionuclide, metal chelate [if present] and optional linker.
• any of the chelators for therapeutic radionuclides disclosed herein may be used.
• forms of the DOTA chelate [Tweedle MF, Gaughan GT, Hagan JT, "1 -Substituted- 1 ,4,7-triscarboxymethyl- 1,4,7, 10- tetraazacyclododecane and analogs.” US Patent 4,885,363, Dec. 5, 1989] are particularly preferred, as the DOTA chelate is expected to lose the bound radionuclide less in the body than DTPA or other linear chelates.
• Coupling can also be performed on DOTA-type macrocycles that are modified on the backbone of the polyaza ring.
• the selection and amount of the proper stabilizer or stabilizer combination used to stabilize the radionuclide selected will also depend on the properties of the isotope selected, as, in general, nuclides that emit high energy alpha or beta radiation will have a requirement for more radiostabilizer than those that emit low energy radiation.
• Many of the lanthanides and lanthanoids include radioisotopes that have nuclear properties that make them suitable for use as radiotherapeutic agents, as they emit beta particles. Some of these are listed in the table below.
• isotopes that are essentially isotopically pure (t.e., free of their nonradioactive congeners) be used, to allow delivery of as high a dose of radioactivity to the target tissue as possible.
• Stabilized radiotherapeutic derivatives of the invention containing beta- emitting isotopes of lutetium and yttrium ( Lu and Y) are particularly preferred.
• the stabilized compounds of the present invention can be administered using many methods which include, but are not limited to, a single or multiple IV or IP injections, using a quantity of radioactivity that is sufficient to permit imaging or, in the case of radiotherapy, to cause damage or ablation of the targeted tissue, but not so much that substantive damage is caused to non-target (normal tissue).
• the quantity and dose required for scintigraphic imaging is discussed supra.
• the quantity and dose required for radiotherapy is also different for different constructs, depending on the energy and half-life of the isotope used, the degree of uptake and clearance of the agent from the body and the mass of the tumor.
• the radiopharmaceutical compositions of the invention can include physiologically acceptable buffers, non-aqueous solvents, bulking agents and other lyophilization aids or solubilizing agents. They can be either in a liquid formulation [either frozen or at room temperature, or can be lyophilized (freeze dried).
• a single, or multi-vial kit that contains all of the components needed to prepare the stabilized radiopharmaceuticals of this invention, other than the radionuclide, is an integral part of this invention.
• a single- vial kit for the preparation of stabilized compounds preferably contains a chelator/optional linker/targeting peptide molecule, an optional source of stannous salt or other pharmaceutically acceptable reducing agent (if reduction is required, e.g., when using technetium or rhenium), and is appropriately buffered with pharmaceutically acceptable acid or base to adjust the pH to a value of about 3 to about 9.
• reducing agent if reduction is required, e.g., when using technetium or rhenium
• the quantity and type of reducing agent used will depend highly on the nature of the exchange complex to be formed. The proper conditions are well known to those that are -skilled in the art.
• the kit contents are in lyophilized form.
• such a single vial kit may optionally contain labile or exchange ligands such as acetate, glucoheptonate, gluconate, mannitol, malate, citric or tartaric acid and can also contain reaction modifiers such as diethylenetriamine-pentaacetic acid (DPTA), ethylenediamine tetraacetic acid (EDTA), or ⁇ , ⁇ , or ⁇ -cyclodextrins and derivatives that serve to improve the radiochemical purity and stability of the final product.
• the kit may also contain bulking agents such as mannitol that are designed to aid in the freeze-drying process, and other additives known to those skilled in the art.
• a multi-vial kit preferably contains the same general components but employs more than one vial in reconstituting the radiopharmaceutical.
• one vial may contain all of the ingredients that are required to form a labile Tc(V) or Re(N) complex on addition of pertechnetate ⁇ e.g., the stannous source or other reducing agent).
• Pertechnetate is added to this vial, and after waiting an appropriate period of time, the contents of this vial are added to a second vial that contains the chelator and targeting peptide, as well as buffers appropriate to adjust the pH to its optimal value and stabilizers sufficient to prevent radiolytic damage. After a reaction time of about 5 to 60 minutes, the complexes of the present invention are fo ⁇ ned. It is advantageous that the contents of both vials of this multi-vial kit be lyophilized. As above, reaction modifiers, exchange ligands, stabilizers, bulking agents, etc. may be present in either or both vials.
• radiostabilizers described herein are a requirement in stabilized formulations of the invention.
• the pu ⁇ ose of these stabilizers is to slow or prevent radiolytic damage to both the unlabeled and radiolabeled radiopharmaceuticals.
• some radiostabilizers are known, none of the literature has revealed the need for radiostabilizers for radiodiagnostic or radiotherapeutic GRP-receptor binding compounds.
• stabilizers are required, especially as the amount of radioactivity in the formulation is increased, and when beta-emitting radiotherapeutic isotopes are used.
• many stabilizers have been identified that, alone or in combination, inhibit radiolytic damage to radiolabeled compounds.
• a radiolysis stabilizing solution containing a mixture of the following ingredients is added to the radiolabeled compound immediately following the radiolabeling reaction: gentisic acid, ascorbic acid, human serum albumin, benzyl alcohol, a physiologically acceptable buffer or salt solution at a pH of about 4.5 to about 8.5, and in a preferred embodiment, one or more amino acids selected from methionine, selenomethionine, selenocysteine, or cysteine.
• the physiologically acceptable buffer or salt solution is preferably selected from phosphate, citrate, or acetate buffers or physiologically acceptable sodium chloride solutions or a mixture thereof, at a molarity of from about 0.02M to about 0.2M.
• concentrations are used: gentisic acid (2-20 mg/mL, most preferably about 10 mg/mL), ascorbic acid (10 to 100 mg/mL, most preferably about 50 mg/mL), human serum albumin (0.1 to 0.5%.
• benzyl alcohol (20 to 100 ⁇ L/mL, most preferably about 90 ⁇ L/mL), pH 4.5 to 8.0, most preferably about pH 5.0 citrate buffer (0.05 molar), and D- or L-methionine, L- selenomethionine, or L-cysteine (2 mg/mL).
• Physiologically acceptable salts of the reagents may also be used (e.g. sodium ascorbate or sodium gentistate).
• D-, L-, and DL- forms of the amino acids may be used. Indeed, reference to a particular amino acid herein is intended to encompass use of the D-, L- and DL- forms of that amino acid.
• the reagent benzyl alcohol is a key component in this formulation and serves two pu ⁇ oses.
• one of its piuposes is to solubilize the radiodiagnostic or radiotherapeutic targeted compound in the reaction solution, without the need for added organic solvents.
• Its second pu ⁇ ose is to provide a bacteriostatic effect. This is important, as solutions that contain the radiostabilizers of the invention are expected to have long post-reconstitution stability, so the presence of a bacteriostat is desirable in order to maintain sterility.
• the amino acids methionine, selenomethionine, cysteine, and selenocysteine are also key components in this formulation and play a special role in preventing radiolytic damage to methionyl residues in targeted molecules that are stabilized with this radiostabilizing combination.
• stabilization is achieved via the use of dithiocarbamate compounds having the following general formula:
• Rl and R2 are each independently H; C1-C8 alkyl; -OR3, wherein R3 is C1-C8 alkyl; or benzyl (Bn) (either unsubstituted or optionally substituted with water solubilizing groups), or wherein R1R2N combined are 1 -pyrrolidinyl-, piperidino-, mo ⁇ holino-, 1 -piperazinyl - and M may be H + , Na + , K + , NH + , N-methylglucamine or other pharmaceutically acceptable +1 ion.
• compounds of the form shown below may be used, wherein M is a physiologically acceptable metal in the +2 oxidation state, such as Mg 2+ or Ca 2+ , and Rl and R2 have the same definition as described above.
• formulations contain stabilizers that are water soluble organic selenium compounds wherein the selenium is in the oxidation state +2.
• stabilizers that are water soluble organic selenium compounds wherein the selenium is in the oxidation state +2.
• amino acid compounds selenomethionine, and selenocysteine and their esters and amide derivatives and dipeptides and tri peptides thereof which can either be added directly to the reaction mixture prior to or during radiolabeled complex preparation, or following complex preparation.
• a fourth approach involves the use of water soluble sulfur-containing compounds wherein the sulfur is in the +2 oxidation state.
• Preferred thiol compounds include derivatives of cysteine, mercaptothanol, and dithiolthreitol. These reagents are particularly preferred due to their ability to reduce oxidized forms of methionine residues ⁇ e.g., methionine oxide residues) back to methionyl residues, thus restoring oxidative damage that has occurred as a result of radiolysis.
• stabilizing reagents it is highly efficacious to use these stabilizing reagents in combination with sodium ascorbate or other pharmaceutically acceptable forms of ascorbic acid and its derivatives.
• the ascorbate is most preferably added after complexation is complete.
• the thiol compound is an amino acid derivative such as cysteine or cysteine ethyl ester, then D-, L- and DL isomers of this amino acid derivative may be used.
• stabilizing formulations containing examples of the four classes of reagents above are described. It should be understood that the four classes of agents can be used separately or in combination, as required to provide adequate radiostability to the radiodiagnostic or radiotherapeutic compound that is being stabilized.
• oxidative stabilization may be used to protect other radiodiagnostic or radiotherapeutics derived from, e.g., peptides, monoclonal antibodies, monoclonal antibody fragments, aptamers, oligonucleotides and small molecules, from oxidative degradation (not necessarily just methionine oxidation).
• Potential stabilizers were evaluated for their ability to prevent or slow the decomposition of Lu complexes of Compound A, referred to as Lu-A, and Lu complexes of Compound B, referred to as 177 Lu-B, their Indium-labeled analogs In-A and ⁇ ⁇ In-B, and other compounds in this class.
• Potential scavengers were evaluated in different ways: by either adding them directly to the reaction mixture used to form the 177 Lu or n 'in complexes, or by adding the stabilizer(s) after the radiometal complex was formed (or both). Several efficacious stabilizers and stabilizer combinations have been identified.
• L-cysteine and the cysteine derivatives L-cysteine ethyl ester or L-cysteine methyl ester, D-, L-, and DL- methionine, L-selenomethionine, gentisic acid (Sodium salt), ascorbic acid (Sodium Salt) and 1-pyrrolidine dithiocarbamic acid ammonium salt (PDTC) were shown to be most efficacious in this respect when used as individual stabilizers.
• a radiolysis protecting solution that contained a mixture of stabilizers proved especially useful. Formulations stabilized by such cocktails maintained excellent radiochemical purity (RCP) values (>95% RCP) for as long as 5 days at room temperature. This stabilizing cocktail is added immediately after formation of the radioactive complex, so would be the second vial of a two-vial kit.
• RCP radiochemical purity
• FIG. 4 shows the results obtained when 1 mL of a reaction mixture containing 104 mCi of 177 Lu-B was incubated at room temperature with 1 mL of the above radiolysis protecting solution that contained 2 mg/mL DL-methionine, 10 mg/mL gentisic acid, 50 mg/mL ascorbic acid, 0.2% HSA and 90 ⁇ l benzyl alcohol in 0.05 M citrate buffer, pH 5.3.
• effective radiostabilization RCP>95%) was achieved for I77 Lu-A if the concentration of methionine in the radiolysis protecting solution was increased to 3 mg/mL and all other reagents were held at their previous levels.
• 177 Lu-A was also stable for 5 days when methionine in the stabilizing cocktail is replaced by methionine, L-cysteine or L-selenomethionine.
• the data in FIG. 5 show the results obtained when 55 mCi of 177 Lu-A was incubated for 5 days at room temperature with the following mixture: 1.5 mg/mL L-cysteine; 5 mg/mL gentisic acid; 25 mg/mL ascorbic acid; 1 mg/mL HSA, 45 ⁇ L benzyl alcohol in 0.05M citrate buffer, pH 5.3.
• Methionine has been reported recently to be a stabilizer for radiodiagnostic compounds. However, in the present application (vide infra), it was determined that that methionine alone was insufficient to protect the compounds from radiolytic damage when high radioactivity levels are used, although some radiostabilization was observed ⁇ see, e.g., FIG. 3). However, the addition of the methionine-containing radiolysis protecting solution described above gives a strong protective effect that is not present when only methionine is used.
• Organic compounds containing selenium in the +2 oxidation state Organic compounds containing selenium in the +2 oxidation state, including selenomethionine and selenocysteine have not been reported as a radioprotectant for radiopharmaceuticals, nor has cysteine or other organic compounds containing thiols in the +2 oxidation state. Both of these compounds were found to be radioprotectants in their own right, and to have valuable properties if added to a radiolysis stabilizing solution as described in this disclosure.
• Cysteine derivatives L-cysteine, when added into a radiolysis stabilizing solution, appears to help prevent the oxidation of the methionine residue present in the GRP receptor-binding peptides.
• Dithiocarbamates provide evidence that dithiocarbamates, in particular the ammonium salt of 1 -pyrrolidine dithiocarbamic acid, provide excellent stability as a single reagent without any additional stabilizers, when added to a radiolabeled peptide after complex formation (2 -vial kit).
• 1 -pyrrolidine dithiocarbamic acid (PDTC) and other dithiocarbamates have not been reported as radioprotectants for either radiodiagnostic or radiotherapeutic applications.
• the structure of PDTC is shown below.
• This compound is also extremely effective if added directly to the formulation during complex formation. At concentrations where it is an effective radiostabilizer, it does not interfere with complex formation. This is a clear advantage, as this allows a single- vial formulation, with all components in one vial.
• Dithiocarbamates such as PDTC also have the added advantage of serving to scavenge adventitious trace metals in the reaction mixture. It has long been known that many radioisotopes ⁇ e.g., °Y, ⁇ ⁇ In) can contain contaminating non-radioactive metals such as Fe, Zn, or Cu that can compete with the radiometal for the chelate. As the molar concentration of the radiometals used for radiotherapy is often very low, even a small amount of contaminating metal can be highly detrimental to a labeling reaction.
• Rl, R2 combinations are: -Me, -Me; -Me, -OMe; -Et, -Et; -Et, -OEt -Et, -n-Bu; -Me, -CH 2 CH 2 NMe 2 ; -Me, -CH 2 CH 2 NMe 3 + ; -Me, -CH 2 COOMe), -Bn, -Bn
• M is a physiologically acceptable metal in the +2 oxidation state, such as Mg 2+ or Ca 2+
• Rl and R2 have the same definition as described above.
• the stereochemistry of the amino acid is not critical to the stabilization the D-, L-, and D,L-mixtures of all amino acids previously cited are useful, as are pharmaceutically acceptable salts thereof.
• Simple derivatives of these amino acids including, but not limited to, N-alkylation, N-acetylation, C-terminus amidation or esterification are useful as well. It is anticipated that simple dipeptides, tripeptides, tetrapeptides and pentapeptides containing one or more of these amino acids could also be used to stabilize radiodiagnostic or radiotherapeutic formulations.
• PDTC 2-hydroxybenzothiazole, 2,1,3-benzothiadiazole, 5-thio-D-glucose
• cystamine dihydrochloride L-cysteine hydrochloride monohydrate, L-cysteine ethyl ester hydrochloride, L-cysteine diethyl ester dihydrochloride, L-cysteine methyl ester hydrochloride, L-cysteine dimethyl ester dihydrochloride, L-cysteinesulfinic acid monohydrate, sodium L-ascorbate (ascorbic acid), 2,5-dihydroxybenzoic acid sodium salt hydrate (gentisic acid), thiamine hydrochloride, L-glutathione reduced, 2-ethyl-4- pyridinecarbothioamide (ethionamide), trithiocyanuric acid trisodium salt nonahydrate, sodium dimethyldithiocarbamate hydrate, sodium diethyldithiocarbamate trihydrate, 3-hydroxyc
• Acetic acid, glacial (ultra-pure) were purchased from J.T. Baker.
• Acetonitrile and sodium acetate, anhydrous (ultra-pure) was purchased from EM Science.
• D-methionine was purchased from Avocado Research Chemicals Ltd.
• L-selenomethionine was purchased from Calbiochem. Methanol, citric acid, anhydrous and sodium citrate were purchased from Fisher Scientific Company. Human serum albumin (HSA) was purchased from Sigma. All reagents were used as received. High-specific activity 177 LuCl 3 (in 0.05 N HCl) was obtained from the University of Missouri Research Reactor, Columbia, Missouri. ⁇ n InCl 3 (in 0.05N HCl) was obtained from either PerkinElmer or Mallinckrodt.
• COMPOUND A (or Compound A) is the unmetallated ligand DOTA-Gly-
• the radiolabeled complexes prepared from these compounds are designated herein by the isotope-compound letter, i.e., 177 Lu-A is the 177 Lu complex of DOTA-Gly-ACA-Gln-T ⁇ -Ala-Nal-Gly-His-Leu-Met-NH 2 ) and ,77 Lu-B is the 177 Lu complex of DOTA-Gly-Abz4-Gln-Trp-Ala-Val-Gly-His-Leu-Met- ⁇ H 2 .
• the synthesis of Compounds A and B is described in applicants' copending patent application Serial No. 10/341,577, filed January 13, 2003, which is hereby entirely inco ⁇ orated by reference.
• the mobile phase flow rate was 1 mL/min. with a gradient starting at 32% B to 34% B over 30 minutes, 34% to 40% B in 5 minutes, back to 32%) B in 5 minutes, then a 5-minute hold for re-equilibration.
• the injection volume was 20 ⁇ L.
• the mobile phase flow rate was 1 mL/min with a gradient starting at 29% B to 32% B over 20 minutes, back to 29% B in 2 minutes, then a 5- minute hold for re-equilibration.
• the injection volume was 20 ⁇ L.
• the mobile phase flow rate was 1 mL/min with a gradient starting at 29% B to 32% B over 20 minutes, back to 29% B in 3 minutes, then an 8- minute hold for re-equilibration.
• the injection volume was 20 ⁇ L.
• the mobile phase flow rate was 1 mL/min. with a gradient starting at 21% B to 24% B over 20 minutes, back to 21% B in 3 minutes, then an 8 minute hold for re-equilibration.
• the injection volume was 20 ⁇ L.
• the mobile phase flow rate was 1 mL/min. with a gradient starting at 20% B, ramping to 24% B over 20 minutes, back to 20% B in 2 minutes, then a 3 minute hold for re-equilibration.
• the injection volume was 10 ⁇ L.
• EXAMPLE 1 shows the results obtained for a series of amino acids that were 1 TT t TT added individually to a solution of Lu-A or Lu-B and then incubated at room temperature over 48 hours, as well as results for an unstabilized control.
• 1 TT 1 TT the amino acid concentration was 6.6 mg/mL
• Lu-A and Lu-B had a concentration of -20 mCi/mL
• 3.5 mCi of 177 Lu was used in each reaction.
• 177 Lu-A and 177 Lu-B were prepared by adding 300 ⁇ L of 0.2 M NaOAc (pH
• RCP radiochemical purity
• Table 3 Evaluation of amino acids as radioprotectants for 177 Lu-A. Stability 177 comparison made by adding different individual amino adds ⁇ 6.6 mg mL) to Lu-A at a radioactive concentration of ⁇ 20 mCi mL, followed by storage at room temperature for up to 48 hours. (3.5 mCi total)
• EXAMPLE 1 methionine at a concentration of 2.5 mg/mL was able to stabilize 3.5 mCi of 17 Lu-A against radiolysis for 5 days.
• EXAMPLE 2 show that methionine is unable to stabilize the same complex when the amount of radioactivity is increased to 50 mCi. Almost complete decomposition of the complex was observed over 5 days, when only L-methionine was used as a stabilizer.
• L-cysteine, selenomethionine, sodium ascorbate, gentisic acid and HSA None of them provided sufficient stabilization to use alone with the high radioactivity levels tested.
• Reagents 6-8 are compounds that were tested to determine their ability to serve as reducing agents for any methionine sulfoxide residues that formed as a result of radiolysis. Reagent 9 was used in the unstabilized control.
• 177 Lu-A was prepared by adding 300 ⁇ L of 0.2 M NaOAc (pH 5.0), 40 ⁇ g Compound A and 20 mCi of 177 LuCl 3 into a reaction vial. The mixture was incubated at 100 °C for five minutes, and then cooled to room temperature. Free I77 Lu was scavenged by adding 10 ⁇ L of 10% Na 2 EDTA-2H 2 O.
• Table 5 Stability of • 177 L ⁇ u-A at a radioactivity concentration of ⁇ 20 mCi/mL, when incubated at room temperature over time with potential non-amino acid radiolysis protecting agents at a concentration of 6.6 mg mL, or as otherwise mentioned*.
• Table 5 above shows the results of a comparative study to determine the radiostabilizing effect of several compounds when added to 177 Lu-A after complex formation. Both the ability of these additives to prevent a decrease in RCP and their ability to inhibit the oxidation of the Methionine residue in 177 Lu-A were studied.
• a Radiolysis Protecting Solution was prepared to contain 10 mg/mL gentisic acid; 50 mg/mL ascorbic acid sodium salt; 2 mg/mL HSA; 2.98 mg mL L-methionine, 0.9% (v:v) benzyl alcohol and 1 mg/mL of Na 2 EDTA.2H 2 O in 0.05 M, pH 5.3 citrate buffer.
• Table 6 Stability comparison of 177 Lu-A or m Lu-B (50 mCi 2 mL) in a Radiolysis Protecting Solution containing L-methionine over 5 days incubation at room temperature (% RCP)
• 177 Lu-A and 177 Lu-B were prepared at a 50 mCi level as described in EXAMPLE 4. Immediately after cooling the reaction mixtures to room temperature, 1 mL of a Radiolysis Protecting solution was added, containing 10 mg/mL gentisic acid; 50 mg/mL ascorbic acid sodium salt; 2 mg/mL HSA; 3.92 mg/mL L-selenomethionine, 0.9% (v:v) benzyl alcohol and 1 mg/mL of Na 2 EDTA.2H 2 O in 0.05 M, pH 5.3 citrate buffer. The reaction vials were stored in the autosampler chamber and the stability was analyzed by RP- HPLC over time using HPLC Methods 3 [ 177 Lu-A] or 4 [ 177 Lu-B]. The results are shown in Table 7 below.
• Table 7 Stability of 177 Lu-A or 177 Lu-B in Radiolysis Protecting Solution containing L- selenomethionine over 5 days incubation at room temperature (% RCP).
• EXAMPLE 6 Effect of L-Cysteine-containing Radiolysis Protecting Solution on RCP of 177 Lu-A and ⁇ 77 Lu-B (50 mCi 2 mL) [00176] Lu-A and Lu-B were prepared at a 50 mCi level as described in EXAMPLE 4.
• Table 8 Stability of 177 Lu-A (50 mCi/2 mL) in Radiolysis Protecting Solution containing L-cysteine at 1.0 or 1.75 mg/mL over 5 days incubation at room temperature (% RCP)
• 177 Lu-B was formulated as follows: To a 5-mL glass vial, 1 mL of 0.2 M NaOAc buffer (pH 4.8), 12 ⁇ L (50 mCi) of 177 LuCl 3 and 30 ⁇ L of a 5 mg/mL solution of COMPOUND B in 0.01N HCl were added, and the vial was heated at 100 °C for 5 min. After being cooled in a water bath, the reaction mixture was diluted 1 :1 by addition of 1 mL of one of the stabilizing solutions below. The samples were then stored in an autosampler (which maintained an average temperature that was -6 °C higher than room temperature) and analyzed by RP- HPLC for up to 120 hours.
• an autosampler which maintained an average temperature that was -6 °C higher than room temperature
• HSA Human Serum Albumin
• AA Sodium ascorbate 99+% was dissolved to a concentration of 100 mg/mL in N 2 -purged 0.05 M, pH 5.0 citrate buffer containing J mg/mL Na 2 EDTA-2H 2 O
• AA Sodium ascorbate 99+% was dissolved to concentration of 50 mg/mL in N 2 -purged 0.05 M, pH 5.0 citrate buffer containing 0.9% Benzyl alcohol and 1 mg/mL Na 2 EDTA-2H 2 O
• Table 10 Stability of • 177, Lu-B mixed 1:1 with stabilizing solutions a-c to provide a) HSA with a final concentration of 50 mg/mL b) AA with a final concentration of either 50 177 mg/mL or c) 25 mg/mL.
• Final Lu-B concentration is 25 mCi/mL:
• Example 8 The results of Example 8 above indicate that either HSA alone or ascorbic acid alone could not maintain an RCP of >95% for times longer than 24 hours.
• the results of Example 1 -8 indicate that a Radiolysis Protecting Solution containing gentisic acid, ascorbic acid, Human Serum Albumin, benzyl alcohol and either cysteine, selenomethionine, or methionine and (ethanol in 0.05M citrate buffer) will stabilize
• each of the reagents in the stabilizing buffer was tested individually by adding 1.0 mg/mL of the individual reagent directly to radiolabeling reactions containing a small amount of radioactivity (3.5 mCi). None interfered with the labeling reaction, but only selenomethionine and methionine showed good protection over time at the low radioactivity levels used.
• Each individual stabilizer was prepared at a concentration of 1 mg/mL in sodium acetate (NaOAc) buffer (0.2 M, pH 4.8). To lead-shielded 4-mL vials was added 200 ⁇ L of the individual NaOAc-stabilizer solutions, 2.72 - 3.64 mCi ,77 LuCl 3 and 4.6 - 6 ⁇ g COMPOUND A (dissolved in water). The ratio of COMPOUND A to Lutetium was 3:1 for all samples. The reaction mixture was heated to 100°C for 5 minutes, and then cooled for 5 minutes in an ambient-temperature water bath. To each sample, 10 ⁇ L of 2%> Na 2 EDTA.2H 2 O in water was added, and then each was divided into two 100- ⁇ L aliquots.
• NaOAc sodium acetate
• reagents in the stabilizing buffer were tested individually by adding 2.5 mg/mL (Example 10) or 5.0 mg/mL (Example 11) of the individual reagents directly to radiolabeling reactions containing a small amount of radioactivity (3.5 mCi).
• the amount of stabilizers was increased to 2.5 mg/mL and 5 mg/mL to decrease the potential for radiolytic damage at high activity levels, it was found again that gentisic acid, ascorbic acid and cysteine could not provide adequate radioprotection for 24 hours, even at radioactivity amounts less than 5 mCi.
• Each stabilizer was prepared at a concentration of 2.5 mg/mL in sodium acetate (NaOAc) buffer (0.2 M, pH 4.8). To lead-shielded 4-mL vials was added 200 ⁇ L of the individual NaOAc-stabilizer solutions, 3.58 mCi 177 LuCl 3 (avg) and 5.08 ⁇ g COMPOUND A (dissolved in water). The ratio of COMPOUND A to Lutetium was 3:1 for all samples. The reaction mixtures were heated to 100°C for 5 minutes, then cooled, treated with Na EDTA-2H 2 O, subdivided and stored as described in Example 9. The radiochemical purity (RCP) percentage data obtained are listed in-Table 12.
• RCP radiochemical purity
• Table 12 RCP Data for 177 L, u-A when Prepared in the Presence of L-Cysteine Hydrochloride Monohydrate, Gentisic acid, Ascorbic acid, L-Selenomethionine or D- Methionine (2.5 mg/mL) as Stabilizers
• Each stabilizer was prepared at a concentration of 5 mg/mL in sodium acetate
• Each individual stabilizer was prepared at a concentration of 10 mg/mL in water. Ethionamide was dissolved in EtOH. To a lead-shielded 4-mL vial was added 500 ⁇ L of NaOAc buffer (0.2M, pH 4.8), 19.6 mCi I77 LuCl 3 and 30 ⁇ g COMPOUND A (dissolved in water). The ratio of COMPOUND A to Lutetium was 3:1. The reaction mixture was heated to 100°C for 5 minutes, then cooled for 5 minutes in an ambient-temperature water bath.
• Table 14 RCP Data for 177 Lu-A When Stabilized After Complex Preparation Using 2- Ethyl-4-pyridinecarbothio amide (Ethionamide), Trithiocyanuric acid trisodium salt nonahydrate, Sodium dimethyldithiocarbamate hydrate or Sodium diethyldithiocarbamate trihydrate as Stabilizers. (13.9 mCi mL)
• EXAMPLE 14 Preparation. Labeling Efficiency and Solution Stability of 177 Lu-A When Prepared in the Presence of Thiamine Hydrochloride, L-Glutathione, 3-Hydroxycinnamic Acid, 4- Hydroxyantipyrine, Acetylsalicylic Acid, 2-HvdroxybenzothiazoIe or 2,1,3- Benzothiadiazole as Stabilizers
• Table 18 RCP Data for ,77 Lu-A When Stabilized After Complex Preparation Using Cystamine dihydrochloride, L-Cysteine ethyl ester hydrochloride, L-Cysteine diethyl ester dihydrochloride, L-Cysteine methyl ester hydrochloride, L-Cysteine dimethyl ester dihydrochloride, or L-Cysteinesulfinic acid monohydrate (5 mg/mL) as Stabilizers
• PDTC l-pyrrolidine dithiocarbamic acid ammonium salt
• Solutions of l-pyrrolidine dithiocarbamic acid ammonium salt (PDTC) were prepared at concentrations of 20-, 10-, 5- and 1 mg/mL by dissolving it in a sodium acetate (NaOAc) buffer solution (0.2 M, pH 4.8).
• NaOAc sodium acetate
• 300- ⁇ L sample vials were added, individually, 50- ⁇ L aliquots of the PDTC-NaOAc buffer solutions, including an aliquot of the NaOAc buffer only, to serve as a control sample.
• To each buffer aliquot was added 9.95 mCi ]77 LuCl 3 (avg) and 17.2 ⁇ g COMPOUND A (dissolved in water).
• the molar ratio of COMPOUND A:Lu (total Lu) for each sample was 3:1.
• the concentration of COMPOUND A was 287- ⁇ g/mL and the activity concentration was 167-mCi/mL.
• the samples were heated to 100°C for 5 minutes, then cooled for 5 minutes in an ambient-temperature water bath.
• Table 20 shows the results obtained. Table 20: RCP Data for 177, Lu-A When Prepared in the Presence of l-pyrrolidine dithiocarbamic acid ammonium salt (PDTC) at 0-20 mg/mL
• PDTC 177 Lu-B was formulated as follows: To a 5-mL glass vial was added 5 mg of PDTC dissolved in 1 mL 0.2 M NaOAc buffer (pH 4.8), 15 ⁇ L (44 mCi) of m LuCl 3 and 30 ⁇ L of a 5 mg/mL solution of COMPOUND B in 0.01N HCl. The reaction vial was crimp-sealed and heated at 100 °C for 5 min. After cooling with a water bath, 1 mL of Bacteriostatic 0.9% NaCI, Injection containing 0.9% Benzyl Alcohol and 1 mg/mL Na 2 EDTA-2H 2 O was added. The sample was stored in an autosampler in which the temperature is -6 °C higher than room temperature, and analyzed by RP-HPLC for up to 24 hours. The table below shows the results obtained.
• L-Selenomethionine: )77 Lu-B was prepared, diluted and analyzed as described above, but 5 mg of L-Se-Met was used in place of PDTC, the heating time was 10 minutes, and the quantity of radioactivity used was 52 mCi.
• L-cysteine ethyl ester, HCl: 177 Lu-B was prepared, diluted and analyzed as described above, but 5 mg of L-CEE, hydrochloride salt was used in place of PDTC, the heating time was 8 minutes and the quantity of radioactivity used was 50 mCi.
• L-cysteine.HCl.H 0: 177 Lu-B was prepared, diluted and analyzed as described above, but 5 mg of L-Cys HCl.H 2 O was used in place of PDTC, the heating time was 8 minutes and the quantity of radioactivity used was 53 mCi.
• Table 21 RCP Data for 1 J 7"7,Lu-B When Prepared in the Presence of PDTC, L- Selenomethionine, L-Cysteine ethyl ester or L-Cysteine.HCl.H 2 O
• EXAMPLE 20 Determination of the Effects of a Contaminant Metal (Zinc) During the Reaction of 177 Lu-B With and Without l-pyrrolidine dithiocarbamic acid ammonium salt in the Reaction Buffer [00217] During the investigations with PDTC, it was found that its addition to reaction 1 T 1 TT mixtures containing LuCl 3 provided a very unexpected benefit. At times, LuCl 3 isotope solutions are contaminated with non-radioactive metals that can interfere with radiolabeling.
• Example 22 The concentration of COMPOUND B in each sample was 150 ⁇ g/mL and the molar ratio of COMPOUND B: 177 Lu:Zinc for each sample was 3:1 :3.
• the samples were heated to 100°C for 5 min, and then cooled for 5 min in an ambient-temperature water bath. To each sample, 10 ⁇ L of 2% Na 2 EDTA-2H 2 O in water was added, and then each was analyzed by HPLC, using HPLC Method 5.
• FIG. 10 shows the results obtained.
• FIG. 10A shows an HPLC chromatogram of COMPOUND B (UV), which has a retention time of 15.4 min. in the system used.
• FIG. 10B shows a radiochromatogram (top) and UN chromatogram (bottom) of Sample 1 (control reaction; no PDTC); which was obtained following the reaction of COMPOUND B with 7 Lu in the presence of zinc.
• the resulting RCP was 0%.
• the primary product formed was the zinc complex of COMPOUND B, which has a retention time of 17.3 minutes. Very little COMPOUND B remains, and very little 177 Lu-B was formed.
• the results illustrated in FIGS. 10A-10C demonstrate that 1 -pyrrolidine dithiocarbamic acid ammonium salt is effective in serving to scavenge adventitious trace metals in the reaction mixture, as radiochemical purity obtained is dramatically improved when PDTC is added to labeling reactions containing an excess of zinc.
• a solution of L-selenomethionine (20 mg/mL) was prepared by dissolving it in NaOAc buffer (0.2 M, pH 4.0). To a lead-shielded 2-mL vial was added 111 ⁇ L of NaOAc buffer (0.2 M, pH 4.0), 25 ⁇ L selenomethionine solution (0.5 mg of Se-Met), 4 ⁇ L of COMPOUND B (20 ⁇ g in 0.01 N HCl) and 1.0 mCi ⁇ ⁇ InCl 3 in 60 ⁇ L of 0.05 N HCl. A control reaction was run containing all reagents above, but substituting NaOAc buffer for the Se-Met solution.
• the reaction mixtures were heated at 100°C for 15 minutes, and then cooled for 1 minute in an ambient-temperature water bath.
• 200 ⁇ L of stabilizing solution (0.2% HSA, 5% ascorbic acid, 0.9% benzyl alcohol, 20 mM Se-Met in 50 mM citrate buffer, pH 5.3) and 2 ⁇ L of 1% Na 2 EDTA-2H 2 O in water were added, and then each was analyzed stored at room temperature for up to 6 hours and analyzed by HPLC as described below.
• the RCP data obtained are listed in Table 21.
• HPLC conditions Nydac CI 8 column, 4.6 x 250 mm, 5 ⁇ M, 1.5 mL/min flow rate at 30°C.
• Solvent A 0.1 % TFA in water
• Solvent B 0.085% TFA in acetonitrile.
• 177 Lu-B was formulated as follows: To a 5-mL glass vial was added 2.94 mg of L-Selenomethionine dissolved in 1 mL of 0.2 M NaOAc buffer (pH 4.8), 25 ⁇ L (110.5 mCi) of 177 LuCl 3 and 30 ⁇ L of a 5 mg/mL solution of COMPOUND B in 0.01N HCl. The reaction vial was crimp-sealed and heated at 100 °C for 10 min.
• Table 23 RCP Data for 177 Lu-B When Prepared in the Presence of L-Selenomethionine (2.94 mg/mL).
• Stabilizer Solution A One part 500 mg/ml L-Ascorbic acid, pH 5.7 containing 0.25 mg/ml Na 2 -EDTA was diluted with 9 parts of normal saline solution [no benzyl alcohol].
• Stabilizer Solution B One part 500 mg/ml L-Ascorbic acid, pH 5.7 containing 0.25 mg/ml Na 2 -EDTA was diluted with 9 parts of Bacteriostatic saline, which contained 0.9 %> (w/v) benzyl alcohol.
• a 100 ⁇ L aliquot of 0.2M NaOAc buffer, pH 4.8 containing 1 mg/mL L- selenomethionine and 13 ⁇ g of Compound B was added to each of two 2-mL sample vials, designated Sample 1 and Sample 2, respectively. Approximately 10 mCi of 177 LuCl 3 was added to each vial and the samples were heated at 100° C for 10 minutes in a temperature- controlled heating block. They were then removed and cooled in an ambient temperature water bath for 5 minutes. After cooling, 400 ⁇ L of Solution A was added to Sample 1, and 400 ⁇ L of Solution B was added to Sample 2. [00231] Both samples were analyzed by HPLC using Method 3 and allowed to stand at room temperature for 24 hours.
• Sulfur compounds, particularly thiols, in the oxidation state +2 were evaluated for the ability to convert methionine oxide residues to the reduced methionyl form.
• the methionine oxidized form of Compound B was synthesized. This oxidized compound is referred to as Compound C.
• Compound C was radiolabelled to form 177 Lu-C, which was mixed with various +2 sulfur derivatives, stored at room temperature and analyzed over time to determine how much methionine oxide in the peptide had been converted to methionine.
• Sample preparation Aliquots [40 ⁇ l, 0.75 mCi] of this reaction solution were mixed with a 100 ⁇ l aliquot of one of the solutions above, e.g., 20 mg/ml Cys; DTT; Met; Se- Met; or 2% ME. The solutions were stored at room temperature over time and analyzed by RP-HPLC at 1 and 3 days. The results obtained are shown in Table 25 below.
• Table 25 Percentage (%) of 177 Lu-C converted [reduced] to 177 Lu-B, following room temperature storage in the presence of Cys, DTT, ME, Met, or Se-Met for 1 to 3 days

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