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
  • 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
  • A61K51/10—Antibodies or immunoglobulins; Fragments thereof, the carrier being an antibody, an immunoglobulin or a fragment thereof, e.g. a camelised human single domain antibody or the Fc fragment of an antibody
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07B—GENERAL METHODS OF ORGANIC CHEMISTRY; APPARATUS THEREFOR
  • C07B59/00—Introduction of isotopes of elements into organic compounds ; Labelled organic compounds per se
  • C07B59/008—Peptides; Proteins
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K2123/00—Preparations for testing in vivo

Definitions

• This invention relates to a procedure for attaching technetium-99m to antibodies using reducing metal reagents. These reagents play a dual role in the labeling reaction under the specified conditions.
• the method of this invention overcomes two problems with prior art methods, which are low specific activity and binding of Tc-99m to low affinity binding sites.
• This invention relates to a procedure for attaching technetium-99m to proteins such as monoclonal antibodies using reducing metal reagents such as tin and zinc according to which 99 Tc binds is to high affinity binding sites and high specific activity is maintained.
• the reagents play a dual role under the given experimental conditions by reducing disulfide bonds in the proteins to sulfhydral groups suitable for binding to technetium, and reducing pertechnetate from Tc(VII) to Tc ⁇ III) or Tc(V) .
• reduction of the disulfide groups on the protein is conducted initially with an excess of tin or zinc reagent, a pertechnetate reagent is added at the end of the protein reduction reaction and allowed to continue to reduce the technetium. Thereafter a chelator scavenger is added to remove poorly bound or unbound 99m Tc.
• Figure 1 illustrates stability studies of 99l TMTc bound to IgG 3 antibody 88BV59 in saline solution with excess DTPA in a ratio of IgG:DTPA of 1:1000 at 37°C.
• Figure 2 shows HPLC radiochromatographs of 99m Tc-88BV59 in the reaction medium after preparation according to the method of the invention.
• Figure 2a shows the peak of technetium antibody conjugate as the major peak. The minor peak is technetium bound to DTPA.
• Figure 2b shows the technetium antibody conjugate purified with all measurable chelator bound technetium removed.
• Figure 3 illustrates the immunoreactivity of the antibody technetium conjugate prepared according to the invention compared with the immunoreactivity of the antibody alone. Immunoreactivity was determined by indirect ELISA on specific antigen coated wells. The reactivity of the radiolabeled antibody (Tc-antibody conjugate) was determined by comparison with the reactivity of native (unbound) antibody by their ability to bind cognate antigen for which the antibody (88BV59) has specificity.
• Figure 4a illustrates the retention of antibody technetium conjugate by tumor xenografts in 6 to 8 week old athymic Balb/c mice.
• the xenografts were developed using enzymatically dissociated human tumor cells containing antigens recognizable by 88BV59.
• a comparison is made between conjugates with intact antibodies and conjugates with F(ab') 2 .
• Figure 4b illustrates serum retention of 88BV59 technetium conjugates in mice having human colon tumor xenografts.
• Figure 4c illustrates the tumor retention of antibody and F(ab * )_ 2 technetium conjugates in the mice.
• Figure 4d illustrates kidney retention of F(ab') 2 and intact antibody technetium conjugates in the mice.
• Figure 4e illustrates liver retention of F(ab')_ 2 and intact antibody technetium conjugates.
• Figure 5 shows a coronal view of the liver SPECT scan of a human patient who has received 15 mCi/lOmg 99m Tc-88BV59 at 4 to 5 hours after administration. Large numbers of lesions in the liver of a size less than or equal to 0.5 cm can be seen. These results were later confirmed by CT scan.
• This procedure describes the protocol for attaching technetium-99m ( S9m Tc) to proteins using reagents containing reducing metals such as tin and zinc. These reagents play a dual role under the given experimental conditions.
• binding to the protein is through a sulfhydral group (SH) obtained by reduction of disulfide in the protein.
• SH sulfhydral group
• the reagents contain well known reducing metals bound to ligands through covalent or coordination bonds. They are sufficiently powerful enough to reduce disulfide bonds present in the protein molecule, creating sulfhydryl groups suitable for attachment to technetium, but not so powerful as to form metal hydroxide colloids. Examples of the preferred metals are Sn, Zn, Rn and Co. They are bound to ligands such as oligosaccharides, polysaccharides and other sugar derivatives by covalent or coordinate bonds. The reagents also reduce pertechnetate for attachment to the protein. Tc(VII) is reduced to either Tc(III) or Tc(V) and concomitantly coupled to the sulfhydryl group on the protein.
• Any loosely bound technetium is chelated with DTPA, EDTA, iminodiacetate, cysteine, diaminedithiol or other chelators, which are added to the reaction mixture after reduction and binding of Tc to the protein to quench the reaction by scavenging unbound and loosely bound Tc.
• the ratio of MoAb to quencher is preferably from about 1:1 to 1:5, and should not to exceed about 1:8.
• the chelators may be attached to an immobile surface, or may be removed by gel filtration chromatography. Our imaging experiments with Tc-antibody conjugates clearly show that the presence of small amounts of Tc-DTPA does not affect the quality of imaging because Tc-DTPA is rapidly cleared from circulation by renal filtration. Thus, it is not always necessary to remove chelator bound 99 ⁇ n Tc from the preparation before administration.
• tin or zinc saccharate or glucarate is used to produce sulfhydryl groups and to reduce technetium for conjugation to sulfhydryls in the antibody.
• the process is unique in using chelators as quenchers, rather than competing for reduced technetium in the reaction mixture by adding them earlier.
• Our reducing reagent is preferably tin saccharate prepared by adding saccharic acid (e.g., 20 mg/ml, deaerated) solution to tin chloride solution (e.g., 5 mg/ml in 0.02M HCl) .
• Tin saccharate may also be prepared by treating tin chloride with excess saccharic acid, removing the precipitated tin saccharate and storing the precipitate in dry nitrogen. It is also possible to combine the metal chloride and the acid together and add that reaction mixture to the protein (e.g., combining stannous chloride and glucaric acid).
• the antibody (10 mg/ml or lyophilized powder) in a buffer solution, or alternatively in a reducing buffer solution is added to the tin saccharate solution and incubated at about 4° to 60°C for 5 to 60 minutes.
• This incubation leads to formation of sulfhydryl groups.
• the period of incubation varies inversely with temperature. Reaction temperature is limited by the stability of the protein. A temperature of incubation cannot be used that will denature the protein.
• Preferred reaction conditions are about 15 minutes to 60 minutes at about 20° to 37°C. Under experimental conditions 1 to 3 SH groups are generated per antibody molecule. This method of labeling has proved to be particularly suitable for antibodies such as an IgG's. Under the same reaction conditions use of tin chloride alone, not as a saccharic acid salt, leads to formation of a colloidal solution not suitable for further use.
• the reducing metal must be bound to a ligand for the method to work.
• Reduction of the antibody is followed by addition of pertechnetate.
• Incubation to reduce Tc(VII) to Tc(III) or Tc(V) and to conjugate with the sulfhydrals on the antibody is carried out at about 20° to 37°C for about two minutes to one hour.
• labeling is accomplished by incubation at about 23° - 37°C for about 30 to 60 minutes.
• a chelator is added (e.g., DTPA) to quench the reaction and to scavenge unbound Tc by conversion to Tc-DTPA.
• This resulting pharmaceutical preparation is purified before administering or, alternatively, directly administered to cancer patients without removing excess Tc-DTPA.
• Tc should be bound to the antibody. Otherwise it should be purified.
• non-antibody conjugated Tc in the original preparation in the form of Tc- DTPA will be removed by the kidneys.
• Patient studies with radiolabeled antibody preparations containing Tc-DTPA have shown good tumor localization. If the composition is to be purified before administration, excess Tc-DTPA is removed by gel filtration column chromatography, leaving pure radiolabeled antibody.
• Tc labeled antibodies prepared according to this invention are very stable. Results obtained with cancer patients using such preparations have clearly shown that even 4 hours after administration the technetium-99m is firmly bound to the antibody. Excellent localization of the radiolabeled antibody was also observed in these cases making it possible to obtain good radioimmunoscintigraphs. Loosely bound Tc, if any, would bind to human serum albumin. HPLC analysis of the serum from a patient treated with Tc-99m labeled 88BV59 did not show any transfer to human serum albumin even 4 hours after administration.
• Another advantage of this method is its ability to label relatively difficult systems, such as F(ab * ) 2 .
• Reductive labeling with technetium of F(ab') 2 frequently results in formation of ""Tc labeled F(ab) .
• many researchers use the reductive method to obtain ""Tc labeled Fab fragment from F(ab') 2 -
• using appropriate concentrations and reaction conditions, particularly reacting at room temperature (20°-25°C) one can mildly introduce technetium in F(ab' ) 2 without alteration.
• Tc0 4 (50-100 mCi) was added and reacted at 37°C for 15 min. (alternatively 23°-25°C for 30 min.). DTPA was then added (1-100 ⁇ m solution). DTPA to MoAb ratio was 0.1:1 to 5:1. Reaction yields of 10-15 mCi/ ⁇ g of protein was easily achieved.
• radiolabeling yields were less than 90%, the radiolabeled antibody would be purified by gel filtration chromatography. In general, yields were always >90% (with 88BV59). Results of purification are illustrated in Figure 2.

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• 1992
  • 1992-02-27 CA CA002104943A patent/CA2104943A1/en not_active Abandoned
  • 1992-02-27 AU AU14576/92A patent/AU658403B2/en not_active Ceased
  • 1992-02-27 JP JP4507406A patent/JPH06505990A/ja active Pending
  • 1992-02-27 EP EP92907824A patent/EP0573577A1/en not_active Withdrawn
  • 1992-02-27 WO PCT/US1992/001577 patent/WO1992015333A1/en not_active Application Discontinuation
  • 1992-02-27 KR KR1019930702561A patent/KR100238558B1/ko not_active IP Right Cessation
• 1993
  • 1993-08-26 FI FI933760A patent/FI933760A/fi unknown

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