NZ314409A - Preparation of a coordination complex of an isonitrile ligand and a radionuclide (typically technetium (tc)) by replacing copper in a sulphate complex - Google Patents

Description

New Zealand Paient Spedficaiion for Paient Number 314409 New Zealand No. International No. 314409 PCT/ TO BE ENTERED AFTER ACCEPTANCE AND PUBLICATION Priority dates: 03.08.1993; Complete Specification Filed: 29.07.1994 Classification:^) C07F1/08; C07F13/00; C07F17/00; A61K51/04; A61K49/04// A61K103:10 Publication date: 27 April 1998 Journal No.: 1427 NEW ZEALAND PATENTS ACT 1953 COMPLETE SPECIFICATION Title of Invention: Tris(isonitrile)copperd) sulfates for preparing radionuclide conpplfexes i.

Name, address and nationality of applicant(s) as in international application form: THE DU PONT MERCK PHARMACEUTICAL COMPANY, a Delaware body corporate of Barley Mills Plaza, Building 25, Wilmington, Delaware 19898, United States of America 4 Und.r *. R,>9"' 1*1on 23 0) the t■ ~ Initials Patents Form No. 5 Our Ref: GL207893 NEW ZEALAND PATENTS ACT 1953 COMPLETE SPECIFICATION TRISdSONITRILE)COPPER(l) SULFATES FOR PREPARING RADIONUCLIDE COMPLEXES Divisional out of New Zealand Patent Application No. 269642 filed 29 July 1994 We, THE DU PONT MERCK PHARMACEUTICAL COMPANY, a body corporate under the laws of the State of Delaware, United States of America of Barley Mills Plaza, Building 25, Wilmington, Delaware 19898, United States of America, hereby declare the invention, for which We pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement: PT0510728 N.Z. PATENT OFFICE 1 - H MAR 1S37 . RfcCElv ollowed by page 1 a) 31 4 4 0 9 WO 95/04114 PCT/US94/07457 TRISfISONITRILE!COPPER (J) SULFATES rOR PREPARING RADTONPgLTDE COMPLEXES Field of thp TnwnHnn This invention relates to methods, compounds and formulations for preparing radiopharmaceutical imaging agents, in particular, Tc-99m isonitrile complexes.

Background of t.hP Invention Isonitrile complexes of a number of radionuclides that are useful as radiopharmaceuticals are described by Jones et. al. in U.S. Pat. No. 4,452,774. The complexes are described as being useful for visualizing cardiac tissue, detecting the presence of thrombi in the lungs and other IS types of blood perfusion defects, studying lung function, studying renal excretion and imaging the bone marrow and the hepatobiliary system. In practice, however, these complexes containing simple hydrocarbon isonitrile ligands have moderately high uptake in the lungs and liver of humans. See, 20 e.g., Holman et. al., J. Nucl. Mpri. 25, 1360 (1984). This uptake can interfere with the visualization of cardiac tissue.

The problem of lung and liver uptake can be partially overcome by using the isonitrile complexes 25 described by Jones et. al. in U.S. Patent Nos. 4,735,793 and 4,872,561. These ester or amide isonitrile complexes generally give better lung and liver clearance, thus allowing earlier or higher contrast imaging. A superior series of ether-substituted isonitrile complexes are described by 30 Bergstein and Subramanyan in U.S. Pat. No. 4,988,827. These ether-substituted isonitrile complexes have beer, extensively evaluated in vivo. Clinical evaluations of technetium-9 9iri (Tc-99m) ether-substituted isonitrile complexes are reported -la- J$t/Lm474s4 0 9 in Kahn et. al., Circulation 22, 1282-1293 (1989)/ Iskandriam et. al., Tuner. J. Cardiol. M, 270-275 (1989); and Christian et. al., Cirnilal-inn jQ, 1615-1620 (1991).

The development of a process for the commercial 5 manufacture of lyophilized kits for the preparation of Tc-99m isonitrile complexes was complicated by the volatility of the isonitrile ligands. Carpenter, Jr. et. al. described in U.S. Pat. No. 4,8 94,445 a solution to this problem by the synthesis of isonitrile adducts of non-radioactive metals 10 such as Cu, Mo, Pd> Co, Ni, Cr, Ag and Rh. The metal- isonitrile adducts are chosen so that when combined with a radioactive metal in an appropriate media, the metal will be displaced by the radioactive metal to form the desired radiopharmaceutical. The copper complexes described are 15 bis(isonitrile)phenanthroline and tetrakis(isonitrile) complexes. Many such adducts react with the desired metal radionuclide (e.g., Tc-99m) at elevated temperature to produce the radiopharmaceutical relatively rapidly. However, the heating requirement is inconvenient and cumbersome in the 20 hospital setting.

Iqbal et. al. describe in U.S. Pat. No. 4,885,100 tris(isonitrile)copper (1) adducts with an anion selected from BF4, PFg, CIO4, I, Br, CI and CF3COO. These adducts react with radionuclides, such as Tc-99m, and provide more rapid 25 preparation of radiopharmaceuticals at room temperature than the complexes described by Carpenter, Jr. et. al.- However, the technology described by Iqbal et. al. does not give sufficiently high yields of Tc-99m-isonitrile complexes after sufficiently short time periods to be practical in a busy 30 hospital setting.

Consequently, a need exists for facile, efficient and cost-effective reagents and methods for preparation of radionuclide complexes.

Summary of the Tnvention 31 4 4 0 9 Accordingly, one aspect of the invention is a method for preparing a coordination complex of an isonitrile iigand and a radionuclide comprising reacting a copper (I) sulfate complex of the isonitrile iigand with the radionuclide in a solvent to replace the copper with the radionuclide, thereby forming the coordination complex.

Another aspect of the invention is a sterile, non-pyrogenic kit for preparing a complex of a radionuclide and an isonitrile Iigand comprising the tris(isonitrile)copper(l) sulfate complex as described below, a transfer agent and a reducing agent capable of reducing a radionuclide in respective amounts sufficient to form the complex of the radionuclide and the isonitrile Iigand.

A tris(isonitrile)copper(l) sulfate complex which is useful for the rapid synthesis of radionuclide isonitrile complexes, in high yield, at about room temperature, is described and claimed in NZ 269642, from which this application has been divided.

A method for preparing a tris(isonitrile)copper(l) sulfate complex comprising: (a) reacting one equivalent of tetrakis(acetonitrile)copperd) sulfate with six equivalents of an isonitrile Iigand; and (b) isolating a solid tris(isonitrile)copperd) sulfate complex, is also described and claimed in NZ 269642.

Detailed Description ef the Preferred An aspect of the NZ 269642 invention is a tris(isonitrile)copper(I) sulfate complex which is useful for preparing radiopharmaceutical diagnostic imaging agents. In general, use of the tris(isonitrile)copper(I) sulfate complex for preparing imaging agents is more facile, efficient and provides higher yields than the prior art complexes. 314 4 The tris(isonitrile)copper(I) sulfate complex of the NZ 269642 invention can be prepared using any isonitrile Iigand. Exemplary isonitrile ligands include those having the formula CNR where R is an organic radical of 1-30 carbon 5 atoms which can be aliphatic or aromatic and can be substituted with a variety of groups which may or may not be charged. The aromatic R group can include phenyl, tolyl, xylyl, naphthyl and biphenyl, each optionally substituted with halo, hydroxy, nitro, alkyl of 1-15 carbon atoms, alkyl 10 ether of 1-15 carbon atoms and alkyl ester of 1-15 carbon atoms. The aliphatic R group can include alkyl, preferably containing 1-20 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl, isobutyl, n-hexyl, 2-ethylhexyl, dodecyl and stearyl, alkenyl, alkynyl or 15 cycloalkyl, each optionally substituted with halo, hydroxy, nitro, alkyl of 1-10 carbon atoms, alkyl ether of 1-10 carbon atoms and alkyl ester of 1-10 carbon atoms. Specific examples of suitable isonitrile ligands can be found in U.S. Patent Nos. 4,452,774, 4,735,793, 4,872,561 and 4,988,827, 20 which are incorporated herein by reference.

A preferred tris(isonitrile)copper(I) sulfate salt of the NZ 269642 invention is represented by the formula (I): [Cu(CNR)3]2 (SO4] (I) where R is alkyl of 1-20 carbon atoms or has the formula (II) 25 or (IIA): — A— 0— R1 or — A— O— R1 I OR2 (II) (IIA) where A is a straight or branched chain alkyl group and 30 R1 and R2 each independently is a straight or branched chain alkyl group or taken together are a straight or branched chain alkylene group, provided that: 314 4 0 (1) the total number of carbon atoms in A plus R1 in formula (II) is 4 to 6, provided further that when the total number of carbon atoms is 6, then th» carbon atom beta to the isonitrile group is a quaternary carbon, and (2) the total number of carbon atoms in A plus R^ plus R2 in formula (IIA) is 4 to 9.

A most preferred sulfate salt is where the isonitrile Iigand is methoxyisobutylisonitrile (MIBI), i.e., where R is a methoxyisobutyl radical. This compound, 10 tris(MIBI)copper (I) sulfate, also known by its IUPAC name, tris(l-isocyano-2-methoxy-2-methylpropane)copper(I) sulfate, is referred to hereinafter as [Cu(MIBI)3]2[SO4).

The tris (isonitrile)copper(I) sulfate complexes of the NZ 269642 invention are more water soluble than the 15 tris(isonitrile)copper (I) adducts disclosed by Iqbal et al. in U.S. Patent No. 4,885,100. The adducts of Iqbal et al. include an anion selected from BF4, PFg, C104, I, Br, CI and CF3COO and exist as cationic or neutral complexes having a maximum solubility in water of 2-3 mg/mL due to the limited 20 water .solubility of the anion or the absence of charge on the complex. In contrast, the sulfate complexes of the present invention exhibit water solubility in excess of 2-3 mg/mL ana preferably in excess of 100 mg/mL, such as in the case of [Cu(MIBI)332[SO4]• Another aspect of the NZ 269642 invention is a method for preparing the tris(isonitrile)copper(I) sulfate complexes described above. The sulfate complexes can be synthesized by the exchange of acetonitrile. molecules in tetrakis(acetonitrile)copper(I) sulfate, i.e., 30 [Cu(CH3CN)4]2[SO4], with isonitrile ligands of the formula CNR, where R is as defined above.

The [Cu (CH3CN)4]2[SO4] can be prepared in situ by heating a mixture of copper(II) sulfate, an excess of one equivalent of copper powder ana an excess of eight 31 4 4 0 9 equivalents of acetonitrile. Addition of six equivalents of isonitrile Iigand to one equivalent of [Cu(CH3CN)4]2[SO4] in a suitable organic solvent such as acetone, acetonitrile, methylene chloride or chloroform at about O'C quantitatively 5 yields [Cu(CNR)3]2tS04]. Equations 1 and 2 summarize the reaction steps, CuS04-xH20 4 Cu° + CH3CN »- [Cu (CH3CN) 4 ] 2 (SO4 ] (1) [Cu (CH3CN) 4 ] 2 [SO4 ] + 6 CNR— [Cu (CNR) 3} 2 [SO4 ] (2)' Crude tris (isonitrile)copper(I) sulfate complex product is isolated by filtration of the resulting solution, evaporation of the volatiles and precipitation from acetone by addition of diethyl ether. The product is then 15 recrystallized successively from hot acetone.

One aspect of the present invention is a method for preparing isonitrile radionuclide coordination complexes. The radionuclide is a radioactive isotope of Tc, Ru, Co, Pt, Fe, Os, Ir, W, Re, Cr, Mo, Mn, Ni/ Rh, Pd, Nb or Ta. 20 Preferably, the radionuclide is Tc-99m. The radiolabeled isonitrile complexes are prepared by mixing a copper isonitrile complex with the radionuclide in a solvent to replace the copper with the radionuclide and form the coordination complex. Exemplary solvents include water, 25 dimethyl sulfoxide, dimethyl formamide, methanol, ethanol, 1-or 2-propanol, acetone or acetonitrile. Preferably, the solvent is water or saline. The reaction temperatures can range from room temperature to reflux temperatures or even higher. Preferably, the reaction is carried out at about 30 room temperature. The radiolabeled Isonitrile complexes are isolable and are obtained in relatively high yields after relatively short reaction times.

WO 95/04114 PCT/US94/07457 31 441 In the case of technetium, Tc-99m isonitrile complexes are preferably made by mixing an amount of tris(isonitrile)copper(I) sulfate, an amount of a transfer agent and an amount of a reducing agent (capable of reducing 5 pertechnetate (99mTc04~) in aqueous medium) in respective amounts sufficient to form the radiolabelled isonitrile complex. Any order of addition of the components can be used. Optionally, an amount of a cyclodextrin sufficient to facilitate the formation of the radiolabelled isonitrile 10 complex can be added prior to the addition of the pertechnetate. Also optionally, a pharmaceutically acceptabl< buffering agent, such as citrate or phosphate, or a lyophilization aid, such as maltol or maltose, or both, may be added. Preferably, the amount of the 15 tris(isonitrile)copper(I) sulfate is about 0.1 mg to about 100 mg, the amount of the transfer agent is about 0.05 mg to about 5 mg, the amount of the reducing agent is about 5|ig to about 5 mg, the amount of the optional cyclodextrin is about 1 mg to about 100 mg, the amount of the optional buffering 20 agent is about 0.1 mg to 25 mg, and the amount of the optional lyophilization aid is 1 weight percent to 10 weight percent.

Preferably, the transfer agent is cysteine or a salt thereof. Alkyl esters of cysteine 25 such as cysteine methyl ester (CME) and cysteine ethyl ester (CEE) are also preferred. CME is most preferred.

Certain of the isonitrile ligands useful in the invention can act as a reducing agent, eliminating the need for an additional reducing agent. Additional reducing agent 30 are used when required or desired to increase the reaction rate. Exemplary reducing agents are stannous salts such as stannous chloride dihydrate, formamidine sulfinic acid, sodium dithionite, sodium bisulfite, hydroxylamine, ascorbic acid and the like.

An exemplary cyclodextrin which may also be included in the labeling reaction is gamma-cyclodextrir..

Intellectual Property Office of NZ 1 5 CZC 1997 f? C ^ r I \ I r« 31 4 4 0 9 Cyclodextrins are believed to function by providing preorganization of reactants in their hydrophobic cavities or pockets thus enhancing the rate of the reaction.

The reaction is generally complete after about 1 5 minute to about 2 hours, depending upon the particular reagents employed and the conditions used. Yields of radionuclide isonitrile coordination complexes prepared by the method of the invention ranne from about 71% to about 85% after about 15 minutes reaction time at about 26* C to about 10 87% to about 95% after 35 suinutes reaction time at about 26" C. The yields obtained at 15 minutes exceed the best obtained in 30 minutes using the technology disclosed in U.S. Patent 4,885,100 of Iqbal et al.

For example, when the appropriate amounts of 15 [Cu(MIBI)3]2[SO4], cysteine hydrochloride (as transfer agent) and the reducing agent stannous chloride dihydrate are reacted with 99mTc04~ at room temperature, yields of 99mTc(MIBI)6+ ranging from about 71 to about 7 6% at 15 minutes and reaching about 87% at 35 minutes are obtained.

When an ester of cysteine is used as the transfer agent, even higher yields of Tc-99m isonitrile complexes are obtained. For example, the reaction of appropriate amounts of [Cu(MIBI)3]2[SO4], cysteine ethyl ester hydrochloride and stannous chloride dihydrate with 99mTc04~ at room 25 temperature, results in about 74% yield of 99mTc(MIBI)6* at 15 minutes and about 90% at 35 minutes. The reaction of appropriate amounts of [Cu (MIBI)3]2[S043, cysteine methyl ester hydrochloride and stannous chloride dihydrate with 99mic04~ at room temperature, results in about 85% yield of 30 99mic(MIBI)g+ at 15 minutes and about 91% at 35 minutes.

When gaituna-cyclodextrin is included in a mixture of appropriate amounts of [Cu (MIBI)3]2[SO4], cysteine methyl ester hydrochloride and stannous chloride dihydrate, the reaction with 99mTc04~ at room temperature results in about 35 78% yield of 99mTc(MIBI)6+ at 15 minutes and about 95% at 35 minutes.

WO 95/04114 PCT/Uf 31 4 4 Kits for preparing a complex of a radionuclide and an isonitrile Iigand in accord with the present invention are sterile and non-pyrogenic and comprise a tris(isonitrile)copper (I) sulfate complex, a transfer agent 5 and a reducing agent for reducing a radionuclide in respective amounts sufficient to form the complex of the radionuclide and the isonitrile Iigand. Optionally, the kits may contain a cyclodextrin, a buffering agent, a lyophilization aid, or any combination thereof. Preferably, 10 such kits contain about 0.1 to about 100 mg of the tris isonitrile copper (1) sulfate complex, about 0.05 to about 5 mg of the transfer agent, about 5//g to about 5 mg of the reducing agent and optionally about 1 to about 100 mg of a cyclodextrin, 0.1 to 25 mg of a buffering agent, or 1 to 10 15 weight percent of a lyophilization aid. It is also preferable that the contents of the kits be lyophilized, if possible, to facilitate storage. If lyophilization is not possible, the kits can be stored frozen. The components are preferably contained in sealed, non-pyrogenic, sterilized 20 containers.

The present invention will now be described in more detail with reference to the following specific, non-limiting examples.

EXAMPLES Analytical Methods High pressure liquid chromatography (HPLC) and thin layer chromatography (TLC) were used to determine the radiochemical purity (RCP) of Tc-99m labelled product. Radiochemical purity reflects percent yield of the 30 radionuclide isonitrile complex.

Aliquots of the labelling reaction mixtures described below were chromatographed on Whatman CI8 reverse- phase thin layer chromatographic plates developed with a 40% acetonitrile, 30% methanol, 20% 0.5 M ammonium acetate ana 10% tetrahydrofuran solvent system. The 99mTc labelling -S- Intellectual Property Office of NZ DEC 1997 Received 31 4 4 0 9 WO 95/04114 PCT/US94/07457 species produced from the pertechnetate and radionuclide isonitrile complex are separated in this system from colloidal material which is formed as a byproduct of the labelling reaction. Radioanalytical HPLC was performed on 5 ^lBondapak Ci8 (4.6 mm x 250 mm) column (Waters Associates). The column was eluted at a flow rate of 1.5 liiL/min with a linear gradient of 100% solvent A (700:300:1 waterracetonitrile:trifluoroacetic acid) to 100% solvent B (100:900:1 water:acetonitrile:trifluoroacetic acid) over 10 10 minutes, held at 100% solvent B for one minute and then returned to 100% solvent A. The RCP, colloid and corrected RCP data in the following Examples are reported in percent. Corrected RCP data were determined from the average of two RCP values from HPLC corrected for the average of three 15 colloid values as determined by TLC, i.e., where % corrected RCP = [(100-% colloid(by TLC))/100](% RCP(by HPLC)).

EXAMPLE 1 Multivariant Parametric Analysis of the Technology Described in U.S. Patent Ko. 4.885.100 20 Empirical evidence has indicated that the technology described by Iqbal et. al. in U.S. Patent No. 4, 885, 100 does not give sufficiently high yields of Tc-99rr. isonitrile complexes after sufficiently short time periods to be practical in a busy hospital setting. Based on an 25 extensive multivariant parametric analysis, it has been determined that the Iqbal et al. technology provides maximum yields of the Tc-99m isonitrile complex, [99mTc(MIBI)6]+> of only 30% and 68% at 10 minute and 30 minute time points, respectively.

The study was statistically designed using a commercially available software package RSDiscover•(Bolt Beranek & Newman, Cambridge, MA). A five-factor, 32 experiment, Face Centered Cubic design was used. The factors included the [Cu(MIBI)3][BF4] level, stannous chloride dihydrate level, cysteine hydrochloride hydrate level, mannitol level and the pH and are listed in Table 1. The sodium citrate dihydrate buffer component was fixed. The 31 4 WO 95/04114 PCT/US94/07457 three levels chosen for each factor were: [Cu(MIBI)3][BF4] 0.5, 1.25 and 2.0 mg/vial; stannous chloride 10, 105 and 200 ^.g/vial; cysteine 3, 7.5 and 12 mg/vial; mannitol 5, 15 and 25 mg/vial and pH 3, 4.5 and 6. The required amounts of the 5 components mannitol, cysteine hydrochloride hydrate, [Cu(MIBI)3][BF4J, stannous chloride dihydrate as indicated in Table 1 and a constant amount of sodium citrate dihydrate were dissolved in a 10.0 mL volumetric flask using argon-sparged, deionized water, adjusting the pH, and diluting to 10 the mark. 1.0 mL of the resulting solution was dispensed into each of three vials that were then placed in a temperature controlled water bath at 26 °C. 1.0 mL of Na99mTc04~ solution (50 mCi/mL obtained from a 99Mo/99mTc radionuclide generator) prepared in 1.8 wt.% saline was added 15 to each vial. The yield of the product [99mTc(MIBI)6l+ at 10 and 30 minutes was determined by the TLC and HPLC methods described above. Two vials were analyzed by both TLC and HPLC, while the third vial was analyzed by TLC only. The data are reported in Table 2. 2 0 Table 1. Component Levels for Response Surface Study Run Mannitol (mo) Cysteine (mo) [Cu(MIBI)3] [BF4](mg) Stannous (|1Q) PH 1 .77 11.5 1 .95 200 6.17 2 .05 7 .77 1 .26 105 4 .37 3 .60 2 .94 0.51 3.22 4 4 .96 3.07 0.50 200 3.20 14 .95 2 .85 1.28 105 4 .33 6 .07 7 .90 1.30 105 4 .37 7 14 . 82 7.56 1.29 200 4.41 e 24 .93 12.16 0.47 200 3. CI 31 4 4 0 9 9 00 GO 12. 07 1.99 200 2.82 4.96 11. 96 0.49 200 6.25 11 14 .82 7.56 1.93 105 4.44 12 .00 7.69 1.30 105 4.50 13 24 .90 12.00 0.51 6.10 14 .00 7.40 1.30 105 4.57 4 . 91 2.98 1.95 200 6.12 16 .19 3.01 1.97 2.98 17 .11 12. 06 1.95 .90 18 14 .98 7.57 1.28 4.62 19 14.98 7.43 1.31 105 3.16 .03 12.12 2.01 3.17 21 .14 7.47 1.27 105 4.46 22 .31 3.06 2.01 200 3.01 23 .06 7.49 1.26 105 4.44 24 .14 2.95 0.55 200 . 97 .00 7.50 1.30 105 4.43 26 .30 7.40 0.60 105 4.43 27 24 .90 3.0C 2.00 . 97 28 4.93 2.9 0.50 .96 29 .03 12 .08 1 .24 105 4.63 ■ 14 .91 7.41 1.35 105 4. 61 31 4 31 .00 12. 03 0.53 3 .12 32 14 .89 7.41 1.31 105 6.07 Table 2. Response Surface Study Data Run # Colloid (avo.) RCP (avq.) Corrected RCP t=lOmin t=30min t=10min t=30min t=10min t=30min 1 2.29 1.92 18.16 51.08 17.74 50 .10 2 14 .14 17.12 .74 45.07 22.10 37 .35 3 16.29 .24 7.66 17.67 6.41 .86 4 .53 42.31 7.80 12.62 .42 7.28 11 .73 21.08 29.62 50.74 26.15 40 .04. 6 .88 18.52 .62 47.49 22.83 38 .69 7 14 .58 22.76 .60 51.32 21.87 39 .64 8 29.49 41.81 17.44 34.93 12.30 .33 9 22.46 33.65 31.42 60.12 . 24.36 39.89 12.22 21.48 9.03 37.15 7.93 29.17 11 8.13 .61 28.90 48.04 26.55 42.94 12 9 .37 13.27 .16 48.55 22.80 42 .11 13 0.0 0.0 0.0 0.0 0.0 0.0 14 .61 14 .53 26.06 51.41 23.30 43.94 4 .88 4 .65 32.14 70.32 .57 67 .05 16 € .86 9.85 28.70 46.96 26.73 42 .33 314 4 17 0.0 0.0 O O 0.0 O O O O 18 3.13 2.21 28.42 55.04 27.53 53. 82 19 19.16 34 .81 23.87 42.58 19.30 27.76 6.28 4.84 31.00 58.15 29.05 55.34 21 13.07 11.93 42.01 57.37 36.52 50.53 22 36.65 45.23 3B.02 55.22 24.09 .24 23 .23 IB.46 26.57 46.80 22.52 38.16 24 13.24 .01 .71 62.94 22.31 53.49 9.56 .16 24.80 47.81 22.43 40.56 26 .38 .54 .48 39.17 17.33 29.17 27 0.0 0.0 0.37 0.31 0.37 0.31 28 0.35 1 .37 23.49 55.48 23.41 54 .72 29 8 .78 13.29 24.71 55.19 22.54 47.86 9.57 14.24 31.29 53.52 28.30 45.90 31 . 7.20 7.04 17. 95 • 37.2 9 16.66 34 .66 32 2.55 2.20 .71 55.02 .05 53.81 The corrected % RCP of [99mTc(MIBI)6l+ data were entered as responses in the experimental design. The data were then modeled in RSDiscover. The Analysis of Variance 5 (ANOVA) tables for the resulting models of the 10 minute [99ititc (MIBI) 6]+ yield (Table 3) and the 30 minute [99mxc(MIBI)g]+ yield (Table 4) are shown below. In Tables and 4, M = mannitol, CY = cysteine, MI = [Cu(MIBI)3][BF4], T = SnCl2*2H20, and p = pH. 3144 Table 3. Least Squares Components ANOVA for RCP at 10 minutes Source deg. _freedom 1 Sum sq.

Mean sq.

F-ratio Signif.

Constant 12579.756 M 1 11 .203 11.203 0.53 0.4754 CY 1 61.130 61.130 2.89 0.1053 MI 276.770 276.770 13.10 0.0018 T 1 71.992 71.992 3.41 0.0806 P 1 96.000 96.000 4.54 0.0463 M* CY 1 144 .581 144.581 6. 84 0.0170 M*T 1 88.552 88.552 4.19 0.0547 CY*P 1 351 .481 351.481 16. 63 0.0006 MI**2 1 563.046 563.046 26. 65 0.0001 MI *T 1 86.777 86.777 4.11 0.0570 MI *P 1 312.008 312.008 14.77 0.0011 T*P 1 291.250 291.250 13.78 0.0015 Residual 19 401.465 21.130 .

Root mean square error .= 0.84 91 Root mean square error adjusted = 0.7538 Table A . Least Squares Components ANOVA for RCP at 30 minutes 31 4 4 0 9 PCT/US94/07457 .

Source deg. freedom s Sum sq.

Mean sq.

F-ratio Signif.

Constant 1 43001.447 M 49.237 49.237 0.80 0.3827 CY 1 56.214 56.214 0.91 0.3517 MI 432.923 432.923 7.04 0.0162 T 1 352.968 352.968 .74 0.0277 P 1 66.529 66.529 1.08 0.3121 M*CY 1 605.900 605.900 9.85 0.0057 M*T 1 324.563 324.563 .28 0.0338 CY*MI 1 142.077 142.077 2.31 0.1459 CY*P 1 1640.296 1640.296 26.67 0.0001 MI**2 ' 1 993.176 . 993.176 16.15 0 .0008 MI*T 1 424 .118 424.118 6.90 0.0171 MI*P 1 846.989 846.989 13.77 0.0016 T*P 1 2380.371 2380.371 38.71 0.0000 Residual 18 1106.913 61.495 Root mean sqfuare error = 0.8780 Root mean square error adjusted = 0.7898 The ANOVA tables show that a model can be generated for the 10 minute [99mTc(MIBI)g]+ yield data that explains 75% of the 5 variability in the data. A similar model can be generated for the 30 minute [ "mTc(MIBI)6]+ yield data that explains 79% of the variability. 314 4 0 9 CT/US94/074571 v « WO 95/04114 per Using these models, the predicted maximum yield of [99mi<c (MIBI) g]+ using the methodology and reagents disclosed by Iqbal et al, in U.S. Patent No. 4,885,100 is 31% at 10 minutes and 75% at 30 minutes. The values of the 5 factors 5 at the predicted maximum were [Cu(MIBI)3][BF4] = 1.9 mg, SnCl2*2H20 «= 192 jig, pH.*= 6, mannitol = 5 mg and cysteine = 3 mg. When this formulation was tested, a 30% yield at 10 minutes and a 68% yield at 30 minutes were obtained. The observed yields were slightly lower than the predicted 10 yields, but well within the standard deviations of the predicted values.

EXAMPLE 2 Synthesis gf TCufMIBI) « 0.5 acetone CuS04«5H20 (24.5 g, 98.1 mmol) and copper metal 15 (12.6 g, 198 mmol) were placed in a 500 mL Schlenk flask under a nitrogen atmosphere followed by 200 mL nitrogen-sparged acetone and 75 mL nitrogen-sparged acetonitrile. The reaction mixture was refluxed under nitrogen for 1.5 hours and then cooled in an ice bath. A large amount of white 20 crystalline solids formed. 2-methoxyisobutylisonitrile (MIBI) (66.6 g, 588 mmol) was then added dropwise over 2 hours. The reaction mixture was allowed to warm to room temperature and stirred for 12 hours. The excess copper metal was filtered off using Schlenk techniques and the 25 volatiles evaporated from the green-colored filtrate. The yellow-green syrupy residue was dissolved in a minimal amount (-200 mL) of acetone(distilled from B2O3, degassed) and then 4 00 mL of anhydrous diethyl ether was added dropwise with vigorous stirring. An off-white oily solid precipitated ana 30 was isolated on a medium Schlenk filter then dried under vacuum.. The crude product was recrystallized three times from a minimal amount of hot acetone in an ar^on glovebox yielding a white crystalline solid (15.0 g, 16.1 mmol). !h NMR (CDC13, 270 MHz) spectral data were as follows: 3.58 (s, 35 12K, CH2), 3.20 (s, 18H, OCH3), 2.12 (s, 3H, acetone), 1.24 (s, 36H, CH3). Calculated elemental analysis for 314 4 WO 95/04114 PCT/US94/07457 . C37.5H69N6O10.5SCU2 was: %C, 45.37. %H, 7.47/ %N, 9.03; %Cu, 13.65.; found was: %C, 48.56; %H, 7.43/ %N, 8.79/ %Cu, 13.4.

EXAMPLES 3-5 Effect Of Tria (iaonitrilel copper Sulfate and Transfer 5 Agent on Yielri of + Amounts of [Cu (MIBI) 3]2 [SO4] • 0.5 acetone and cysteine hydrochloride hydrate as indicated in Table 5 were dissolved together with 0.27 mmol of mannitol, 0.17 mmol sodium citrate dihydrate and 0.009 mmol stannous chloride 10 dihydrate in a 10.0 mL volumetric flask using argon-sparged, deionized water, adjusting the pH and diluting to the mark. 1.0 mL of the resulting solution was dispensed into each of three vials that were then placed in a temperature controlled water bath at 26° C. 1.0 mL of Na99ltlTcC>4 (50 mCi/mL) solution prepared as in Example 1 was added to each vial and the corrected % RCP determined at 15 and either 35 or 4 0 minutes. The data are reported in Table 5.

Table 5. Effect of [Cu(MIBI)3]2[SO4] Level and Cysteine Level on [99i"Tc (MIBI) 6]+ Yield Example No.

Cys (mmol) MIBI* (mmol) pH Colloid t=15min Colloid t=35min RCP coirr. t = 15 RCP corr. t=35 3 0.008 O.OS7 .8 3.3 n.d. 71 n.d. 4 0.008 0.200 .8 2.2 n.d. 74 n.d. 0.016 0.067 .2 4.6 4.0 76 87 * MIBI refers to molar concentration of MIBI in the form of [Cu(MIBI)3)2ISO4], calculated by [Cu salt) x 6.

The results show the effect of using higher concentrations of [Cu(MIBI)3]+, attainable by using the more soluble sulfate salt [Cu (MIBI)3)2 [SO4] . The 15 minute yields of [99mTc(MIBI)e]+ are significantly increased over those obtained using the technology disclosed in Iqbal et al. U.S. 314 4 0 Patent 4,885,100. In fact, the 15 minute yield surpass those obtained at 30 minutes using the prior technology. There is also a beneficial effect on the yield by increasing the cysteine level, so that an 87% yield of [99mTc(MIBI)£]+ can 5 be obtained after a 35 minute incubation under the conditions of Example No. 5.

EXAMPLES fi *7 Effect of Cysteine Alkvl Esters on f^^TcfMIBI\c1+ Yield Amounts of [Cu (MIBI)332[SO4]*0.5 acetone and either 10 cysteine methyl ester hydrochloride(CME) or cysteine ethyl ester hydrochloride(CEE) as indicated in Table 6 were dissolved together with 0.27 mmol of mannitol, 0.17 mmol sodium citrate dihydrate and 0.009 mmol stannous chloride dihydrate in a 10.0 mL volumetric flask using argon-sparged, 15 deionized water, adjusting the pH and diluting to the mark. 1.0 mL of the resulting solution was dispensed into each of three vials that were then placed in a temperature controlled water bath at 26 "C. 1.0 mL of Na^9mTc04 (50 mCi/mL) solution prepared as in Example 1 was added to each vial and 20 the reactions monitored at 15 and 35 minutes. The data are presented in Table 6.

Table 6. Effect of Cysteine Alkyl Esters as Transfer Agents on [99r"Tc (MIBI) 6+) Yield EX.

Transfer TA MIBI* PH Colloid Colloid RCP RCP No.

Agent mmol mmol t=15m t=35m corr. corr. t^lSm t=35m 6 CME 0.016 0.067 .6 0 0 85 91 7 CEE 0.016 0.067 .6 0.8 0.6 7 A 90 * MIBI refers to molar concentration of MIBI in the form of (Cu(MIBI)3)2[SO4]» calculated by (Cu salt) x 6. 314 4 The results demonstrate the beneficial effect of substituting alkyl esters of cysteine for cysteine as the transfer agent. The improvement in yield is mostly due to a significant lessening of the amount of "mTc colloid by-5 product formed. Yields as high as 85% can be obtained at 15 minutes using the preferred cysteine methyl ester as the transfer agent(Example No.7). The 35 minute yields in both Example Nos. 6 and 7 are 90%.

EXAMPLE 6 Effect of Cvclodgxti-ln on t*+1 Yield 0.011 mmol [Cu(MIBI)3]2[SO4]*0.5 acetone, 0.022 mmol cysteine methyl ester hydrochloride, 0.38 mmol gamma-cyclodextrin , 0.008 mmol sodium citrate dihydrate, 0.008 mmol anhydrous chromium(II) chloride and 0.0009'mmol stannous 15 chloride dihydrate were dissolved in a 10.0 mL volumetric flask using argon-sparged, deionized water, adjusting the pH, and diluting to the mark. 1.0 mL of the resulting solution was dispensed into each of three vials that were then placed in a temperature controlled water bath (26 °C) . 1.0 mL of 20 . Na99rnTc04~ (50 mCi/mL) solution prepared as in Example 1 was added to each vial and the reactions monitored at 15 and 35 minutes. The data are presented in Table 7.

Table 7. Effect of gamma-cyclodextrin on [99mTc(MIBI)6+] Yield Ex. gamma- CME MIBI* PH Colloid Colloid RCP RCP No. cyclodextrin mmol mmol t=15m t«=35m corr. corr. mmol t=15m t=35r. 8 0.038 0.002 0.006 6.4 0.7 CO O 78 95 * MIBI refers to molar concentration of MIBI in the form of [Cu(MIBI)3]2[SO4), calculated by [Cu salt] x 6.

These data demonstrate the beneficial effect of adding gamma-cyclodextrin to the reaction mixture. A yield of 78% is obtained at 15 minutes and 95% at 35 minutes while using Lli 4 0 3 WO 95/04114 PCT significantly less [Cu (MIBI) 3] 2 [SO4] (0 . 001 vs. 0.01 mmol) and significantly less cysteine methyl ester (0.002 vs. 0.016 mmol) under these reaction conditions. This effect is due to the impact of preorganization of the reactants on the 5 reaction rate.

The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing 10 specification, as indicating the scope of the invention. 74 / / U I 4

Claims (35)

WHAT WE CLAIM IS:

1. A method for preparing a coordination complex of an isonitrile Iigand and a radionuclide comprising mixing a copper(l) sulf^. complex of the isonitrile Iigand with the radionuclide in a solvent to replace the copper with the radionuclide, thereby forming the coordination complex.

2. The method of claim 1 wherein the radionuclide is a radioactive isotope of Tc, Ru, Co, Pt, Fe, Os, Ir, W, Re, Cr, Mo, Mn, Ni, Rh, Pd, Nb or Ta.

3. The method of claim 2 wherein the radionuclide is a radioactive isotope of Tc.

4. The method of claim 3 wherein the radionuclide is Tc-99m.

5. The method of claim 1 wherein the isonitrile Iigand has the formula CNR, where

R is an aromatic organic radical of6 -30 carbon atoms which is optionally substituted by phenyl, tolyl, naphthyl or biphenyl, each optionally substituted with halo, hydroxy, nitro, alkyl of 1-15 carbon atoms, alkyl ether of 1-15 carbon atoms or alkyl ester of 1-15 carbon atoms, or

R is an aliphatic organic radical of 1-30 carbon atoms which is optionally substituted by alkyl, alkenyl, alkynyl or cycloalkyl, each optionally substituted with halo, hydroxy, nitro, alkyl of 1-10 carbon atoms, alkyl ether of 1-10 carbon atoms or alkyl ester of 1-10 carbon atoms,

where each optional substituent is optionally charged.

Intellectual Property Office of NZ

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received

31 4 4 0 9

6. The method of claim 5 wherein R is alkyl of 1-20 carbon atoms or aryl of phenyl, tolyl, xylyl, naphthyl or biphenyl.

7. The method of claim 1 wherein the copper(I) sulfate complex of the isonitrile Iigand has the formula (1):

[Cu(CNR)3]2 tSO4] (I)

where R is alkyl of 1-20 carbon atoms or has the formula (II) or (IIA):

— A— 0—R1 or —a—0— R1

I

OR2

(II) (IIA)

where A is a straight or branched chain alkyl group ana R1 and R^ each independently is a straight or branched chain alkyl group or taken together are a straight or branched chain alkylene group, provided that:

(1) the total number of carbon atoms in A plus R1 in formula (II) is 4 to 6, provided further that when the total number of carbon atoms is 6, then the carbon atom beta to the isonitrile group is a quaternary carbon, and

(2) the total number of carbon atoms in A plus rI plus R2 in formula (IIA) is 4 to 9.

- 23 -

31 4 4 0 9

8. The method of claim 7 wherein the solubility of the complex in water is in excess of .3 mg/mL.

9. The method of claim 8 wherein the solubility of the complex in water is in excess of 100 mg/ml

10. The method of claim 7' wherein the copper (I) sulfate complex of the isonitrile Iigand is tris (1-isocyano-2-methoxy-2-methylpropane)copper(I) sulfate.

11. The method of claim 1 further comprising including a transfer agent in the reaction.

^2. xhe method of claim H wherein the transfer agent is cysteine or a salt thereof.

13. The method of claim 12 wherein the transfer agent is an alkyl ester of cysteine.

14. The method of claim 13 wherein the transfer agent is cysteine methyl ester.

15. The method of claim 13 wherein the transfer agent is cysteine ethyl ester.

16*. The method of claim 1 further comprising including a reducing agent in the reaction.

17. The method of claim 16 wherein the reducing agent is a stannous salt/ formamidine sulfinic acid/ sodium dithionite, sodium bisulfite, hydroxylamine or ascorbic acid

18. The method of claim 17. wherein the stannous salt is stannous chloride dihydrate.

19. The method of claim 1 further comprising including a cyclodextrin in the reaction.

20. The method of claim 19 wherein the cyclodextrin is gamma-cyclodextrin.

— 24 «

21. The method of claim 1 wherein the copper (1) sulfate complex of the isonitrile Iigand and the radionuclide are mixed in water or saline at about room temperature.

22. The method of claim 1 wherein the radionuclide isonitrile coordination complex is formed in a yield of about 71 mole percent to about 95 mole percent.

23. A sterile, non-pyrogenic kit for preparing a complex of a radionuclide and an isonitrile Iigand comprising a the tris(isonitrile)copper (I) sulfate complex, a transfer agent and a reducing agent capable of reducing a radionuclide in respective amounts sufficient to form the complex of the radionuclide and the isonitrile Iigand.

24. The kit of claim 23 wherein the amount of the tris(isonitrile)copper (I) sulfate complex is about 0.1 to about 100 mg, the amount of the transfer agent is about 0.05 to about 5 mg and the amount of the reducing agent is about

5 /jg to about 5 mg.

25.. The kit of claim23 wherein the components are lyophilized or frozen and the radionuclide is Tc-99m.

26. The kit of claim- 23 wherein the transfer agent is cysteine or a salt thereof.

27. The kit of claim 26 wherein the transfer agent is an alkyl ester of cysteine.

28. The kit of claim27 wherein the cysteine alkyl ester is cysteine methyl ester.

29. The kit of claim 21 wherein the cysteine alkyl ester is cysteine ethyl ester.

30. The kit of claim"23 wherein the reducing agent is stannous chloride dihydrate.

31. The kit of claim 23 further comprising a cyclodextrin in an amount sufficient to facilitate the

25 intellectual Property

Office of NZ

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31 4 4 0 9

-26-

formation of the complex of the radionuclide and the isonitrile Iigand.

32. The kit of claim 31 wherein the cyclodextrin is gamma-

cyclodextrin.

33. The kit of claim 32 wherein the amount of the gamma-cyclodextrin is about 1 to about 100 mg.

34. A method as claimed in claim 1 suustantially as herein described with reference to the Examples.

35. A sterile, non-pyrogenic kit as claimed in claim 23 substantially as herein described.

THE DU PONT I 'ARMACEUTICAL COMPANY

By The^r Attorneys BALDWIN,4ON AND CAREY

END OF CLAIMS

N.Z. PATENT OFFICE "7

14 MAR 1997

. RECEIVED j