Drug – bio-affecting and body treating compositions – Radionuclide or intended radionuclide containing; adjuvant... – In an organic compound
Reexamination Certificate
1993-03-19
2001-03-20
Dees, José G. (Department: 1616)
Drug, bio-affecting and body treating compositions
Radionuclide or intended radionuclide containing; adjuvant...
In an organic compound
C530S391300, C530S391900, C530S391700, C530S391500, C424S001110
Reexamination Certificate
active
06203775
ABSTRACT:
BACKGROUND OF THE INVENTION
The field of the invention is protein labelling.
An important issue in clinical radiology is the labelling of proteins, such as monoclonal antibodies, for diagnostic and therapeutic purposes. The radioactive metals, indium (
111
-In) and technetium (
99m
Tc) are useful for diagnostic imaging, whereas rhenium (
186 and 188
-Re) is useful for targeted tumor therapy.
SUMMARY OF THE INVENTION
A problem with
99m
-Tc and
186 Or 188
-Re labeling is the non-specific incorporation of chemically-reduced metal into the protein; the reduced metal is associated with a large number of low-affinity binding sites on the protein. Upon injection into the bloodstream of a patient, this weakly-bound metal can detach from the protein and bind to non-target tissues. The non-specifically-bound metal complicates the detection of target-bound metal by increasing biological background counts, the chance for artifacts, and the time necessary to obtain accurate target
on-target discrimination.
The invention addresses this problem by providing a method of labelling proteins, in particular with binding specificity for cell surface molecules, with a metal, such as a radioisotope or a paramagnetic metal, by first chelating the metal to a compound having a molecular weight of at least 1,000. The protein is then labelled by reacting the labelled compound, which contains a first reactive group capable of forming a covalent bond with a protein, with the protein, which contains or is modified to contain a second reactive group, forming a covalent bond between the first and second reactive groups.
The compound is preferably a polymer such as a polypeptide, e.g., poly-L-lysine.
The reactive group of the chelating compound is preferably one that forms a covalent bond with a sulfhydryl group on the protein, such as a maleimido group.
Preferably, the protein to be labelled is an antibody, more preferably a monoclonal antibody and most preferably, the Fab′ fragment of a monoclonal antibody.
The method of the invention results in the formation of a metal-labelled protein that is substantially devoid of unchelated metal. By making use of a compound with a molecular weight of at least 1,000, the method of the invention provides a way to amplify the specific activity of the labelled protein by chelating multiple atoms of metal to the compound prior to conjugating the chelating compound to the target protein. Another advantage this method is the ability to easily purify the high molecular weight chelated compound from the very low molecular weight unchelated metal.
The labelled protein of the invention, which specifically binds to certain mammalian cells, can be used in diagnostic methods for labelling cells in a mammal. For detection, the metal is preferably a paramagnetic metal such as gadolinium (Gd), or a radioisotope such as
111
-In or
99m
-Tc.
Certain labelled proteins of the invention, which specifically bind to certain mammalian cells, can be used for killing unwanted cells, such a tumor cells, in a mammal. For radiotherapy, the metal is preferably a cytotoxic radioisotope, such as
186
-Re or
188
-Re.
Other features and advantages of the invention will be apparent form the following detailed description, and from the claims.
DETAILED DESCRIPTION
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Torchilin Vladimir P.
Trubetskoy Vladimir S.
Dees Jos,e G.
Fish & Richardson P.C.
Jones Dameron
The General Hospital Corporation
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