Drug – bio-affecting and body treating compositions – Radionuclide or intended radionuclide containing; adjuvant... – In an organic compound
Reexamination Certificate
2000-09-18
2003-10-07
Jones, Dameron L. (Department: 1616)
Drug, bio-affecting and body treating compositions
Radionuclide or intended radionuclide containing; adjuvant...
In an organic compound
C424S001650, C424S001110, C530S300000, C530S311000, C530S317000, C514S002600, C514S005200, C514S009100, C514S806000
Reexamination Certificate
active
06630123
ABSTRACT:
This invention pertains to a method of increasing tissue accumulation and retention of radiolabeled compounds (radioligands), thus improving their therapeutic and diagnostic value.
Radiolabelled compounds are used for both tumor detection and tumor therapy. Many tumor cells have a higher density of cell receptors for various circulating compounds than do non-tumor cells; e.g., endocrine tumors show a high density of cell surface receptors for somatostatin, and brain gliomas show a high density of receptors for epidermal growth factor. Thus a radiolabeled compound that binds to these cellular receptors preferentially binds to the tumor cells. Additionally, angiogenesis, the formation of new blood vessels from established microvasculature, is a critical process for tumor growth. Primary tumors and metastases will not grow beyond 2 mm in diameter without an enhanced vascular supply. Angiogenic cells also have a higher density of cell receptors for various circulating compounds than do non-angiogenic vascular tissue; e.g., receptors for both somatostatin and vascular endothelial growth factor are higher in angiogenic tissue. Thus a tumor can also be detected by radiolabeled compounds binding to the angiogenic cells that are closely associated with the tumor cells.
An ideal tumor imaging agent would maximize the radioactivity at the target cells, and minimize the background signal, resulting in a well-defined image of the tumor foci. For example,
111
In-DTPA-D-Phe-1-octreotide and
123
I-vasoactive intestinal peptide, two receptor-based radioligands, have been used to localize primary endocrine tumors as well as metastaticliver lesions. See A. Kurtaran, et al., “Vasoactive Intestinal Peptide and Somatostatin Receptor Scintigraphy for Differential Diagnosis of Hepatic Carcinoid Metastasis,” The Journal of Nuclear Medicine, vol. 38, pp. 880-881 (1997).
An ideal radioligand therapy agent would accumulate selectively in target cells. The effectiveness of radiotherapy is due to the destruction of dividing cells resulting from radiation-induced damage to cellular DNA. See W. D. Bloomer et al., “Therapeutic Application of Iodine-125 Labeled Iododeoxyuridine in an Early Ascites Tumour Model,” Current Topics in Radiation Research Quarterly, vol. 12, pp. 513-25 (1977). In both therapeutic and imaging applications, any unbound, circulating radioligand is rapidly cleared by excretory systems, which helps protect normal organs and tissues. The radioligand may also be degraded by body processes which will increase the clearance of the free radioisotope. See G. A. Wiseman et al., “Therapy of Neuroendocrine Tumors with Radiolabelled MIBG and Somatostatin Analogues, ” Seminars in Nuclear Medicine, vol. XXV, No. 3, pp. 272-278 (1995).
In both tumor imaging and therapy, a clinical goal is to maximize the amount of radiolabeled compound taken up by the tumor. The amount of radidligand that accumulates in target cells depends on many factors, for example: (1) the concentration gradient of the radioligand between the blood and the targeted tissue; (2) the number of cellular receptors, membrane or intracellular, and the affinity of those receptors for the radioligand; (3) the relative concentrations of labeled and unlabeled ligand competing for a given receptor; (4) the recycling rate for the cellular receptors; (5) the capacity of the cell to store the radioligand; and (6) the degradation of the radioligaud inside the cell. See R. K. Rippley et al., “Effects of Cellular Pharmacology on Drug Distribution in Tissues,” Biophysical Journal, vol. 69, pp. 825-839 (1995).
Radiolabeled compounds have typically been administered by intravenous, bolus injection. In a few instances, radiolabeled compounds have been given as infusions over 30 to 60 min, usually to limit side effects of the drug, not to increase efficacy. See e.g., H. P. Kalofonos et al., “Antibody Guided Diagnosis and Therapy of Brain Gliomas using Radiolabeled Monoclonal Antibodies Against Epidermal Growth Factor Receptor and Placental Alkaline Phosphatase,” The Journal of Nuclear Medicine, vol. 30, pp. 163-645 (1989); I. Virgolini et al., “Vasoactive Intestinal Peptide-Receptor Imaging for the Localization of Intestinal Adenocarcinomas and Endocrine Tumors,” The New England Journal of Medicine, vol. 331, pp., 1116-21 (1994); G. A. Wiseman et al., “Therapy of Neuroendocrine Tumors with Radiolabelled MIBG and Somatostatin Analogues,” Seminars in Nuclear Medicine, vol. XXV, no. 3, pp. 272-78 (1995); S. W. J. Lamberts et al., “Somatostatin-Receptor Imaging in the Localization of Endocrine Tumors,” The New England Journal of Medicine, vol. 323, pp. 126-49 (1990); E. P. Krenning et al., “Somatostatin Receptor Scintigraphy with Indium-111-DTPA-D-Phe-1-Octreotide in Man: Metabolism, Dosimetry and Comparison with Iodine-123-Tyr-3-Octreotide,” The Journal of Nuclear Medicine, vol. 33, pp. 652-58 (1992); E. P. Krenning et al., “Localisation of Endocrine-Related Tumours with Radioiodinated Analogue of Somatostatin,” The Lancet, vol. 1989, no. 1, pp. 242-244 (1989). There is one report of an infusion duration of two (2) hours. See J. A. Carrasquillo et al., “Indium-111 T101 Monoclonal Antibody is Superior to Iodine-131 T101 in Imaging of Cutaneous T-Cell Lymphoma,” The Journal of Nuclear Medicine, vol. 28, pp. 281-87 (1987).
The ability of a cell to take up a radiolabeled compound in the short term is limited by the number of cellular receptors or transport proteins for the compound on the cell membrane or within the cell. When the radioligand is administered by bolus injection, the binding pharmocokinetics dictate that uptake of the radioligand is linearly related to the amount injected only at low concentrations of the radioligand. At higher concentrations, the receptors for the radioligand become saturated. See H. Zhu et al., “Potential and Limitations of Radioimmunodetection and Radioimmunotherapy with Monoclonal Antibodies,” The Journal of Nuclear Medicine, vol. 38, no. 5, pp. 731-41 (1997); and R. M. Kessler et al., “High Affinity Dopamine D2 Receptor Radioligands. 1. Regional Rat Brain Distribution of Iodinated Benzamides,” The Journal of Nuclear Medicine, vol. 32, pp. 1593-1600 (1991). These saturated receptors are not able to bind more radioligand until either the receptor releases the radioligand, or the receptor-radioligand complex has been transported to another part of the cell and the receptor has been recycled to again bind a new molecule of the radioligand. Because the circulating unbound radioligand is rapidly eliminated, by the time the receptors are free to accept another molecule of the radioligand, the radioligand may no longer be present. Thus, the accumulation of radioligand depends on the availability of unbound radioligand, and on the recycling time of the cellular receptors and transport proteins.
The recycling of the cellular receptors depends on the fate of the ligand-receptor complex. Many, if not most, peptide compounds (including peptide and protein hormones) that bind to surface receptors are internalized as a ligand-receptor complex by endocytosis, i.e., invagination of the plasma membrane. Examples of peptides that have been shown to be internalized as part of a ligand-receptor complex include nerve growth factor, fibroblast growth factor, epidermal growth factor, platelet-derived growth factor, cholecystokinin, vascular endothelial growth factor, vasoactive intestinal peptide, gastrin-releasing peptide, leukemia inhibitory factor, somatostatin, oxytocin, bombesin, calcitonin, arginine vasopressin, angiotensin II, atrial natriuretic peptide, insulin, glucagon, prolactin, growth hormone, gonadotropin, thyrotropin-releasing hormone, growth hormone-releasing hormone, gonadotropin-releasing hormone, corticotropin-releasing hormone, interleukins, interferons, transferrin, substance P, neuromedin, neurotensin, neuropeptide Y, and various opioids. This internalization takes time—minutes or even hours. See G. Morel, “Internalization and Nuclear Localization of Peptide Hormones,” Biochemical Pharmacology, vol. 47(1), pp. 63-76 (1994
Espenan Gregory D.
Woltering Eugene A.
Board of Supervisors of Louisiana State University and Agricultu
Davis Bonnie J.
Jones Dameron L.
Runnels John H.
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