(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2012/0065365A1
`(43) Pub. Date:
`Mar. 15, 2012
`Chen et al.
`
`US 20120065365A1
`
`(54)
`
`STABLE RADIOPHARMACEUTICAL
`COMPOSITIONS AND METHODS FOR
`THER PREPARATION
`
`Publication Classification
`
`(51) Int. Cl.
`(2006.01)
`C07K 7/06
`(2006.01)
`C07K I4/655
`(2006.01)
`C07K 7/18
`(2006.01)
`C07K I4/595
`(2006.01)
`C07K 7/23
`(2006.01)
`C07K 4/68
`(2006.01)
`C07K 7/16
`(2006.01)
`C07K I4/62
`(2006.01)
`C07K 4/545
`(52) U.S. Cl. ......... 530/303: 530/327: 530/315; 530/311;
`530/314:530/351; 530/399; 530/312:530/309
`
`ABSTRACT
`(57)
`Stabilized radiopharmaceutical formulations are disclosed.
`Methods of making and using stabilized radiopharmaceutical
`formulations are also disclosed. The invention relates to sta
`bilizers that improve the radiostability of radiotherapeutic
`and radiodiagnostic compounds and formulations containing
`them. In particular, it relates to stabilizers useful in the prepa
`ration and Stabilization of targeted radiodiagnostic and radio
`therapeutic compounds, and, in a preferred embodiment, to
`the preparation and stabilization of radiodiagnostic and radio
`therapeutic compounds that are targeted to the Gastrin
`Releasing Peptide Receptor (GRP-Receptor).
`
`(75)
`
`Inventors:
`
`(73)
`
`Assignee:
`
`Jianqing Chen, Bordentown, NJ
`(US); Karen E. Linder, Kingston,
`NJ (US); Edmund R. Marinelli,
`Lawrenceville, NJ (US); Edmund
`Metcalfe, Kingston, NJ (US);
`Adrian D. Nunn, Lambertville, NJ
`(US); Rolf E. Swenson, Princeton,
`NJ (US); Michael F. Tweedle,
`Princeton, NJ (US)
`BRACCO IMAGING S.P.A.,
`Milan (IT)
`13/280,485
`
`(21)
`(22)
`
`(63)
`
`(60)
`
`Appl. No.:
`
`Filed:
`
`Oct. 25, 2011
`
`Related U.S. Application Data
`Continuation of application No. 10/566,112, filed on
`Jul.9, 2007, filed as application No. PCT/US04/23930
`on Jul. 23, 2004.
`Provisional application No. 60/489,850, filed on Jul.
`24, 2003.
`
`AAA, Ex. 2007
`Evergreen Theragnostics, Inc. v. AAA SA
`PGR2021-0002
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`FIG. 7A
`
`ADC A, ADC CHANNEL ACH: WHPLCDA1A2002\OCT-1200\10-3-02\B237.2019.D)
`
`MAU
`350
`300
`250
`200
`150
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`
`CONTROL IN PBS
`
`200
`
`150
`
`100
`
`50
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`F.G. 7B
`
`ADC1 A, ADC CHANNEL ACH:\HPLCDA1V2002\AUG1.20\8-9-02\48HSTA05.D)
`MAU is METHIONINE
`
`400
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`
`
`
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`SO
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`FIG. 9
`
`ADC A, ADC CHANNEL ACH: \HPLCDA1V2002VSEP.1.20OV9-4-02\B2375000.D)
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`O is o f
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`
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`STABLE RADIOPHARMACEUTICAL
`COMPOSITIONS AND METHODS FOR
`THEIR PREPARATION
`
`CROSS REFERENCE TO RELATED
`APPLICATIONS
`0001. This application claims benefit of U.S. Provisional
`Application No. 60/489,850 filed Jul. 24, 2003, which is
`hereby incorporated by reference in its entirety.
`
`FIELD OF THE INVENTION
`0002 This invention related to stabilizers that improve the
`radioStability of radiotherapeutic and radiodiagnostic com
`pounds, and formulations containing them. In particular, it
`related to stabilizers useful in the preparation and stabiliza
`tion of targeted radiodiagnostic and radiotherapeutic com
`pounds, and, in a preferred embodiment, to the preparation
`and Stabilization of radiodiagnostic and radiotherapeutic
`compounds that are targeted to the Gastrin Releasing Peptide
`Receptor (GRP-Receptor).
`
`BACKGROUND OF THE INVENTION
`0003 Radiolabeled compounds designed for use as radio
`diagnostic agents are generally prepared with a gamma-emit
`ting isotope as the radiolabel. These gamma photons pen
`etrate water and body tissues readily and can have a range in
`tissue or air of many centimeters. In general. Such radiodiag
`nostic 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
`does to the patient. Radionucleotides such as "Tc, '''In,
`'*I, 7Ga and Cu have been used for this purpose.
`0004. In contrast, 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. Radionucleotides
`Such aS 90Y. 177Lu 149Pm lSm 109Pd 67Cu 166Ho 3. II
`32p, 18618sre, ORh. 2 At 225Ac, 47s 213Bi, and others,
`are potentially useful for radiotherapy. The +3 metal ions of
`the lanthanide isotopes are of particular interest, and include
`'77Lu (relatively low energy B-emitter), ''Pm, 'Sm (me
`dium energy) and 'Ho (high energy). 'Yalso 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.
`0005. 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 radiolabeled com
`pound 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. These radicals are very
`reactive and can damage proteins and DNA.
`0006. Some of the immediate products that form from the
`radiolysis of water are outlined below.
`
`0007 Of the products that form, (e.g. H", OH, H*, and
`OH), the hydroxyl radical IOH) is particularly destructive.
`This radical can also combine with itself to form hydrogen
`peroxide, which is a strong oxidizer.
`
`0008. In addition, interaction of ionizing radiation with
`dissolved oxygen can generate very reactive species such as
`Superoxide radicals. These radicals are very reactive towards
`organic molecules (see e.g. Garrison, W. M., Chem. Rev.
`1987,87,381-398).
`0009 Production of such reactive species at the site or
`sites that the radiotherapeutic or radiodiagnostic compound is
`targeted to (e.g., a tumor, bone metastasis, blood cells or other
`targeted organ or organ system) will, if produced in Sufficient
`quantity, have a cytostatic or cytotoxic effect. The key factor
`for successful radiotherapy is the delivery of enough radiation
`dose to the targeted tissue (e.g., tumor cells, etc.) to cause a
`cytotoxic or tumoricidal effect, without causing significant or
`intolerable side effects. Similarly, for a radiodiagnostic, the
`key factor is delivery of sufficient radiation to the target tissue
`to image it without causing significant or intolerable side
`effects.
`0010 Alpha particles dissipate a large amount of energy
`within one or two cell diameters, as their range of penetration
`in tissues is only ~50 Lum. This can cause intense local dam
`age, especially if the radiolabeled compound has been inter
`nalized into the nucleus of the cell. Likewise, radiotherapeu
`tic compounds labeled with Auger-electron emitters such as
`'In have a very short range and can have potent biological
`effects at the desired site of action. The emissions from thera
`peuticbeta-emitting isotopes such as 'Luor'Y have some
`what longer ranges in tissue, but again, most of the damage
`produced occurs within a few millimeters or centimeters from
`the site of localization.
`0011. However, the potentially destructive properties of
`the emissions of a radiotherapeutic isotope are not limited to
`their cellular targets. For radiotherapeutic and radiodiagnos
`tic compounds, radiolytic damage to the radiolabeled com
`pound itself can be a serious problem during the preparation,
`purification, storage and/or shipping of a radiolabeled radio
`therapeutic or radiodiagnostic compound, prior to its
`intended use.
`0012 Such radiolytic damage can cause, for example,
`release of the radioisotope e.g., by dehalogenation of radio
`iodinated antibodies or decomposition of the chelating moi
`ety 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 radio
`metal 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 recep
`tor-binding region of a targeting peptide or radiolabeled anti
`body. Radioactivity that does not become associated with its
`target tissue may be responsible for unwanted side effects.
`(0013 For example, DOTA-Gly-ACA-Gln-Trp-Ala-Val
`Gly-His-Leu-Met-NH. (ACA=3-Amino-3-deoxycholic acid)
`and DOTA-Gly-Abz4-Gln-Trp-Ala-Val-Gly-His-Leu-Met
`NH (Abz4-4-aminobenzoic acid) the two chelating ligands
`shown in FIGS. 1 and 2, respectively, have been shown to
`specifically target the Gastrin Releasing Peptide (GRP)
`Receptors. In the examples that follow, these have been
`
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`described as Compounds A and Compound B respectively.
`Other GRP receptor-binding ligands are described in U.S.
`Pat. No. 6,200,546, to Hoffman et al., published U.S. appli
`cation US. 2002/0054855, and in copending application Ser.
`No. 10/341,577, tiled Jan. 13, 2003, the entire contents of
`which are incorporated by reference.
`0014 When radiolabeled with diagnostic and radiothera
`peutic radionuclides such as '''In and ''Lu, Compounds A
`and B have been shown to have high affinity for GRP recep
`tors, both in vitro and in vivo. However, these compounds can
`undergo significant radiolytic damage that is induced by the
`radioactive label if these radiolabeled complexes are prepared
`without concomitant or Subsequent addition of one or more
`radioStabilizers (compounds that protect against radiolytic
`damage). This result is not surprising, as the hydroxyl and
`Superoxide radicals generated by the interaction of B-par
`ticles with water are highly oxidizing. Radiolytic damage to
`the methionine (Met) residue in these peptides is the most
`facile mode of decomposition, possibly resulting in a
`methionine sulfoxide derivative.
`0015 Cell binding results show that the resulting radi
`olytically damaged derivatives are devoid of GRP-receptor
`binding activity (ICso values greater than micromolar).
`Hence, it is critical to find inhibitors of radiolysis that can be
`used to prevent both methionine oxidation and other radi
`olytic decomposition routes in radiodiagnostic and radio
`therapeutic compounds.
`0016 Preventing such radiolytic damage is a major chal
`lenge in the formulation of radiodiagnostic and radiothera
`peutic compounds. For this purpose, compounds known as
`radical scavengers or antioxidants are typically used. These
`are compounds that react rapidly with, e.g., hydroxyl radicals
`and Superoxide, thus preventing them from reaction with the
`radiopharmaceutical of interest or reagents for its prepara
`tion.
`0017. There has been extensive research in this area. Most
`of it has focused on the prevention of radiolytic damage in
`radiodiagnostic formulations, and several radical scavengers
`have been proposed for such use. However, it has been found
`in the studies described herein that the stabilizers reported to
`be effective by others, provide insufficient radiostabilization
`to protect ''Lu-A and ''Lu-B, the Lutetium complexes of
`Compounds A and B, respectively, from radiolytic damage,
`especially when high concentrations and large amounts of
`radioactivity are used.
`0018 For example, Cyr and Pearson Stabilization of
`radiopharmaceutical compositions using hydrophilic thioet
`hers and hydrophilic 6-hydroxy chromans. Cyr, John E.;
`Pearson, Daniel A. (Diatide, Inc., USA), PCT Int. Appl.
`(2002), WO 200260491 A2 20020808 state that diagnostic
`and therapeutic radiopharmaceutical compositions radiola
`beled with ?I, II, ''At, 7Sc, 7 Cu, 7°Ga, Y,
`Sm,
`159Gd, 165Dy, 166Ho, 175Yb. 177Lu,212Bi, 213Bi,68Ga,99mTc,
`'In and 'I can be stabilized by the addition of a hydro
`philic thioether, and that the amino acid methionine, a hydro
`philic thioether, is especially useful for this purpose.
`0019. A study was therefore performed wherein L-me
`thionine (5 mg/mL) was added to '77Lu-A, to evaluate its
`ability to serve as a radical scavenger. As will be described in
`more detail below, reverse phase HPLC shows that after five
`days, almost complete decomposition of 'Lu-A had
`occurred, indicating that the radioStabilizer used was insuffi
`cient to prevent radiolytic damage. In vitro binding results
`indicate that such decomposition can dramatically decrease
`
`the potency and targeting ability, and hence the radiothera
`peutic efficacy, of the compound thus damaged. To attain the
`desired radiotherapeutic effects one would need to inject
`more radioactivity, thus increasing the potential for toxicity to
`normal organs.
`0020. In order to identify suitable antioxidant radical scav
`engers that might be useful for the radiostabilization of GRP
`receptor binding radiodiagnostic and radiotherapeutic com
`pounds, several studies were performed. One or more
`potential radiostabilizers was added after complex formation
`(a two-vial formulation) or they were added directly to the
`reaction mixture prior to complexation with a radiometal (or
`both). Ideally, the radiostabilizer should be able to be added
`directly to the formulation without significantly decreasing
`the radiochemical parity (RCP) of the product, as such a
`formulation has the potential to be a single-vial kit.
`0021. The radical scavengers identified as a result of these
`studies have general utility informulations for the preparation
`of compounds used for a variety of radiodiagnostic and radio
`therapeutic applications, and may be useful to stabilize com
`pounds radiolabeled with a variety of isotopes, e.g., "Tc,
`186/188Re,
`In, 90Y. 77Lu, 213Bi, 225Ac, 166Ho, 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 mol
`ecules. However, the stabilizers identified should have appli
`cability to a wide range of radiolabeled peptides, peptoids,
`Small molecules, proteins, antibodies, and antibody frag
`ments and the like. They are useful for the radioprotection of
`any compound that has a residue or residues that are particu
`larly sensitive to radiolytic damage, such as, for example,
`tryptophan (oxidation of the indole ring), tyrosine (oxidative
`dimerization, or other oxidation), histidine, cysteine (oxida
`tion of thiol group) and to a lesser extent serine, threonine,
`glutamic acid, and aspartic acid. Unusual amino acids com
`monly used in peptides or drugs that contain sensitive func
`tional groups (indoles, imidazoles, thiazoles, furans,
`thiophenes and other heterocycles) could also be protected.
`
`SUMMARY OF THE INVENTION
`0022. It is the aim of this invention to provide stabilizers
`and stabilizer combinations that slow or prevent radiolytic
`damage to targeted radiotherapeutic and radiodiagnostic
`radiolabeled compounds, especially compounds labeled with
`radiometals, and thus preserve the targeting ability and speci
`ficity of the compounds. It is also an aim to present formula
`tions containing these stabilizers. As described by the
`examples below, many stabilizers have been identified that,
`alone or in combination, inhibit radiolytic damage to radio
`labeled compounds. At this time, four approaches are particu
`larly preferred. In the first approach, 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).
`0023 The physiologically acceptable buffer or salt solu
`tion is preferably selected from phosphate, citrate, or acetate
`buffers or physiologically acceptable sodium chloride solu
`tions or a mixture thereof at a molarity of from about 0.02M
`to about 0.2M. Thereagent benzyl alcohol is a key component
`in this formulation and serves two purposes. For compounds
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`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 radio
`stabilizers of the invention are expected to have long post
`reconstruction 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 methio
`nyl residues in targeted molecules that are stabilized with this
`radioStabilizing combination.
`0024. In the second approach, stabilization is achieved via
`the use of dithiocarbamate compounds having the following
`general formula:
`
`R1
`
`S
`
`V -(
`N
`M
`R2
`
`SM
`
`wherein R1 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 solubiliz
`ing groups).
`or wherein R1R2N combined=1-pyrrolidinyl-, piperidino
`morpholino-, 1-piperazinyl- and M-H, Na', K", NH.",
`M-methylglucamine, or other pharmaceutically acceptable
`+1 ions.
`0025. Alternatively, compounds of the form shown below
`may be used, wherein Mis a physiologically acceptable metal
`in the +2 oxidation state, such as Mg" or Ca", and R1 and R2
`have the same definition as described above.
`
`X-(
`
`S
`
`S
`
`N
`M
`
`0026. These reagents can either be added directly into
`reaction mixtures during radiolabeled complex preparation,
`or added after complexation is complete, or both.
`0027. The compound 1-Pyrrolidine Dithiocarbamic Acid
`Ammonium salt (PDTC) proved most efficacious as a stabi
`lizer, when either added directly to the reaction mixture or
`added alter complex formation. These results were unex
`pected, as the compound has not been reported for use as a
`stabilizer for radiopharmaceuticals prior to these studies.
`Dithiocarbamates, and PDTC in particular, have the added
`advantage of serving to scavenge adventitious trace metals in
`the reaction mixture.
`0028. In the third approach, formulations containstabiliz
`ers that are water soluble organic selenium compounds
`wherein the selenium is in the oxidation state +2. Especially
`preferred are the amino acid compounds selenomethionine,
`and selenocysteine and their esters and amide derivatives and
`dipeptides and tripeptides thereof, which can either be added
`directly to the reaction mixture during radiolabeled complex
`preparation, or following complex preparation. The flexibil
`ity 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.
`
`0029. It is highly efficacious to use these selenium com
`pounds in combination with sodium ascorbate or other phar
`maceutically acceptable forms of ascorbic acid and its deriva
`tives.
`0030 The ascorbate is most preferably added after com
`plexation is complete. Alternatively, it can be used as a com
`ponent 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 cys
`teine, mercaptothanol, and dithiol threotol. These reagents are
`particularly preferred due to their ability to reduce oxidized
`forms of methionine residues (e.g., methionine oxide resi
`dues) back to methionyl residues, thus restoring oxidative
`damage that has occurred as a result of radiolysis. With these
`thiol compounds, if is highly efficacious to use these stabiliz
`ing 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.
`0031. The stabilizers and stabilizer combinations may be
`used to improve the radiolytic stability of targeted radiophar
`maceuticals, comprising peptides, non-peptidic Small mol
`ecules, 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
`
`0032 FIG. 1 shows the structure of Compound A.
`0033 FIG. 2 shows the structure of Compound B.
`0034 FIG. 3 illustrates the results of an HPLC analysis of
`a mixture of '77Lu-A with 2.5 mg/mL L-Methionine over 5
`days at room temperature at a radioconcentration of 25 mCi/
`mL, 50 mCi total. FIG. 3A is a radiochromatogram of a
`reaction mixture for the preparation of 'Lu-A, which was
`initially formed in >98% yield. FIG. 3B is radiochromato
`gram of 77Lu-A, 25 mCi/mL, after live days at room tem
`perature, demonstrating complete radiolytic destruction of
`the desired compound. The radiostabilizer added (5 mg/mL,
`L-Methionine) was clearly insufficient for the level of radio
`protection required
`0035 FIG. 4 is an HPLC trace radiodetection showing
`that '77Lu-B (104 mCi) has >99% RCP for 5 days when
`diluted 1:1 with radiolysis protecting solution that was added
`after the complex was formed.
`0036 FIG. 5 is an HPLC trace radiodetection showing
`that '77Lu-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.
`0037 FIG. 6A and FIG. 6B show the structure of the
`methionine sulfoxide derivative of 77Lu-A (FIG. 6A) and
`methionine sulfoxide derivative of '''In-B (FIG. 6B).
`0038 FIG. 7A and FIG. 7B show stabilizer studies
`'77Lu-A (FIG. 7A) and '77Lu-B (FIG. 7B). Radioactivity
`traces are shown from a study to compare the radioStabilizing
`effect of different amino acids, when added to '77Lu-A (FIG.
`7A) and ''Lu-B (FIG.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 mCiof'77Lu was added to each vial. A full description of
`the experimental procedure is given in Example 1.
`
`AAA, Ex. 2007
`Page 19 of 48
`
`

`

`US 2012/0065365 A1
`
`Mar. 15, 2012
`
`0039 FIG.8 shows an HPLC trace radiodetection show
`ing the radiostability of 77Lu-A over 5 days at room tem
`perature at a radioconcentration of 25 mCi/mL in presence of
`2.5 mg/mL L-methionine (50 mCi total). The details of this
`study are given in Example 2.
`0040 FIG.9 shows an HPLC trace radiodetection show
`ing the stability of '77Lu-Bata concentration of 50 mCi/2 mL
`in a radiolysis protecting solution containing L-methionine.
`The details of this study are given in Example 4.
`0041
`FIGS. 10A-C show radiochromatograms and UV
`chromatograms comparing samples with and without 1-pyr
`rolidine dithiocarbamic acid ammonium salt in the reaction
`buffer and containing Zinc as a contaminant metal during the
`reaction of 77Lu-B. The experimental procedure for this
`study is given in Example 20.
`
`DETAILED DESCRIPTION OF THE INVENTION
`0042. In the following description, various aspects of the
`present invention will he further elaborated. For purposes of
`explanation, specific configurations and details are set forthin
`order to provide a thorough understanding of the present
`invention. However, it will also be apparent to one skilled in
`the art that the present invention may be practiced without the
`specific details.
`0043. Furthermore, well known features may be omitted
`or simplified in order not to obscure the present invention.
`
`1. Metal Chelator
`0044. In some radiopharmaceuticals, the isotope is a non
`metal, such as 'I, "'I or 'F, and is either coupled directly
`to the rest of the molecule or is bound to a linker. However, if
`the radioisotope used is a metal, it is generally incorporated
`into a metal chelator. The term “metal chelator” refers to a
`molecule that forms a complex with a metal atom. For radio
`diagnostic and radiotherapeutic applications it is generally
`preferred that said complex is stable under physiological
`conditions. That is, the metal will remain complexed to the
`chelator backbone in vivo. In a preferred embodiment, a
`metal chelator is a molecule that complexes to a radionuclide
`metal to form a metal complex that is stable under physiologi
`cal conditions and which also has at least one reactive func
`tional group for conjugation with a targeting molecule, a
`spacer, or a linking group, as defined below. The metal chela
`tor M may be any of the metal chelators known in the art for
`complexing a medically useful metalion or radionuclide. The
`metal chelator may or may not be completed with a metal
`radionuclide, Furthermore, 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.
`0045. The metal chelators of the invention may include,
`for example, linear, macrocyclic, terpyridine, and NS, NS,
`or Na chelators (see also, U.S. Pat. No. 4,647.447, U.S. Pat.
`No. 4,957,939; U.S. Pat. No. 4,903,344, U.S. Pat. No. 5,367,
`080, U.S. Pat. No. 5,364,613, U.S. Pat. No. 5,021,556, U.S.
`Pat. No. 5,075,099, U.S. Pat. No. 5,886,142, the disclosures
`of which are incorporated by reference herein in their
`entirety), and other chelators known in the art including, but
`not limited to, HYNIC, DTPA, EDTA, DOTA, TETA, and
`bisamino bisthiol (BAT) chelators (see also U.S. Pat. No.
`5,720.954). For example, macrocyclic chelators, and in par
`ticular Nchelators are described in U.S. Pat. Nos. 4.885.363:
`5,846,519; 5,474,756; 6,143,274; 6,093,382; 5,608, 110:
`
`5,665,329; 5,656,254; and 5,688,487, the disclosures of
`which are incorporated by reference herein in their entirety.
`Certain NS chelators are described in PCT/CA94/00395,
`PCT/CA94/00479, PCT/CA95/00249 and in U.S. Pat. Nos.
`5,662,885; 5,976,495; and 5,780,006, the disclosures of
`which are incorporated by reference herein in their entirety.
`The chelator may also include derivatives of the chelating
`ligand
`mercapto-acetyl-glycyl-glycyl-glycine (MAG3),
`which contains an NS, and NS systems such as MAMA
`(monoamidemonoaminedithiols), DADS (NS diaminedithi
`ols), CODADS and the like. These ligand systems and a
`variety of others are described in Liu and Edwards, Chem Rev.
`1999, 99, 2235-2268; Caravan et al., Chem. Rev. 1199, 99,
`2293-2352; and references therein, the disclosures of which
`are incorporated by reference herein in their entirety.
`0046. The metal chelator may also include complexes
`known as boronic acid abducts of technetium and rhenium
`dioximes, such as those described in U.S. Pat. Nos. 5,183,
`653: 5,387,409; and 5,118,797, the disclosures of which are
`incorporated by reference herein, in their entirety.
`0047. Examples of preferred chelators include, but are not
`limited to, derivatives of diethylenetriamine pentaacetic acid
`(DTPA).
`1,4,7,10-tetraazacyclotetradecane-1,4,7,10-tet
`raacetic acid (DOTA). 1-substituted 14.7-tricarboxymethyl
`1,4,7,10 tetraazacyclododecane triacetic acid (DO3A),
`derivatives of the 1-1-(1-carboxy-3-(p-nitrophenyl)propyl-1,
`4,7,10 tetraazacyclododecane triacetate (PA-DOTA) and
`MeO-DOTA, ethylenediaminetetraacetic acid (EDTA), and
`14.8, 11-tetraazacyclotetradecane-1,4,8,11-tetraacetic acid
`(TETA), derivatives of 3.39.9-Tetramethyl-4,8-diazaunde
`cane-2,10-dione dioxime (PnAO); and derivatives of 3.39.9-
`Tetramethyl-5-oxa-4,8-diazaundecane-2,10-dione dioxime
`(oxa Pn AO). 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 pen
`taacetic acid (benzo-DTPA) and derivatives thereof, includ
`ing 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 com
`pounds can consist of one ring, or two or three rings joined
`together at the hetero ring elements, e.g., benzo-DOTA,
`dibenzo-DOTA, and benzo-NOTA, where NOTA is 1,4,7-
`triazacyclononane N.N',N'-triacetic acid, benzo-TETA,
`benzo-DOTMA, where DOTMA is 1,4,7,10-tetraazacy
`clotetradecane-1,4,7,10-tetra