Browsing by Author "Angerstein, C."

Derivatives of somatostatin (sms) are attracting increasing interest as part of the treatment of several cancer diseases expressing sins receptors (srs). Radiolabeled sms analogs can additionally be used for systemic radiotherapy and for diagnostic investigations. Glycosylated sms-14 (sms-dextran(70)) was characterized regarding in vitro srs binding, biodistribution, and blood half-life in mice. Rat brain cortex membranes (expressing srs 2) were used for the srs binding study. Tyr(3)-Octreotide was used as positive control. The binding data were analyzed by competition curve analysis. In the biodistribution study, the Bolton-Hunter reagent was used for the radioiodination of sms-dextran(70). Organs and blood were collected at different time-points and the percentage of the injected dose per gram of tissue (%ID/g) was calculated. The conjugate was administered subcutaneously (sc). The sms-dextran(70) showed high srs binding affinity (i.e., in the same nanomolar range as the reference ligand Tyr(3)-octreotide (IC(50)similar to2.5 nM). The blood half-life was approx 27 h after reaching maximum blood concentration 24 h postinjection. Because of the molecular weight of the conjugate (i.e., approx 75,000) being above the kidney threshold for dextran (i.e., 50,000), the digestion and excretion is assumed to be mainly through the hepatobiliary system. Increased uptake was seen in the adrenals, which are receptor-positive organs. Some accumulation was seen in the stomach, indicating certain deiodination of the conjugate label. The sms-dextran(70) showed promising properties and its clinical relevance is currently being evaluated in clinical phase I-II studies.

Aim: Formal and clinical comparison of a new 3(rd)-generation-Tg-IRMA (3-G-IRMA; Dynotest(R) Tg-plus) with a conventional Tg-IRMA (3-G-IRMA; SElco(R) Tg-assay) for patients with differentiated thyroid carcinoma. In addition we evaluated, if thyroglobulin (Tg) levels above a specific threshold concentration indicate the need for further investigations for residual disease. Patients, methods: Tg concentration of 105 sera of 93 consecutive patients with a differentiated thyroid cancer was determined with both assays and compared at different cut-off values (Dynotest(R) Tg-plus: 0.2, 1, 2 ng/ml; SElco(R) Tg-assay: 0.5, 1, 2 ng/ml) with the clinical results in respect to the corresponding TSH concentration. Results: Tg concentration did not show any significant difference (SElco(R) Tg-assay 0.5 ng/ml, Dynotest Tg-plus 0.2 ng/ml). The Tg-values of both assays correlated with 97%. However, correlation of recovery in both assays was small (40%). The sensitivities and specificities of both assays at different cut-offs and TSH values did not reveal significant differences. In patients with TSH concentration >30 muU/ml the functional assay sensitivity was superior to arbitrary cut-offs in the decision to start further evaluations. Conclusions: In our study neither formal nor clinical significant differences between two Tg-assays were found. In a hypothyroid patient (TSH > 30 muU/ml, Tg concentration exceeding the functional assay sensitivity) further investigations for residual disease are warranted. Higher thresholds are of limited value, due to a inacceptable high rate of false negative results.

The AMG implies far-reaching implications for the synthesis of new radiopharmaceuticals for clinical trials. Aim, methods: As a part of the DFG-funded Clinical Research Group (KFO 179) a project designated "Immuno-PET for assessment of early response to radiochemotherapy of advanced rectal cancer" was initiated. This trial is focused on a trivalent bispecific humanized monoclonal antibody, and a Ga-68-labeled peptide. Following the new regulatory framework we established a GMP-compliant cleanroom laboratory and applied for a manufacturing permission. Results: During the project constructural, personnel and organizational conditions for a successful application were established, including a quality management system. A GMP-compliant cleanroom laboratory class C was constructed, equipped with a two-chamber lock. The actual manufacturing is performed in a closed system with subsequent sterile filtration. The manufacturing processes have been automatised and validated as well as the necessary quality controls. The manufacturing permission was granted after an official inspection. Conclusions: The new German Drug Act is considered as a break in the production practice of nuclear medicine. The early involvement and communication with the authorities avoids time-consuming and costly planning errors. It is much to be hoped that the new legal situation in Germany will not cause serious impairments in the realization of clinical trials in German nuclear medicine.

The development of monofunctional DTPA derivatives has been a major breakthrough in the labelling of proteins or peptides with a variety of radiometals. Although this methodology is simple and useful for indium-111 labelling, the stability of these conjugates is too low for most therapeutic nuclides. Cyclic chelators, such as DOTA, have shown excellent kinetic stability with a variety of radiometals, but the labelling procedure is more difficult, requiring ultra-pure reagents and a heating step that sometimes endangers the biomolecule's integrity. The aim of this work was twofold: (a) to develop a novel, open chain chelator which can be easily labelled with various radiometals, displaying higher kinetic stability than monofunctional DTPA, and (b) to evaluate this chelator in vitro and in vivo when conjugated to a CCK-B receptor ligand as a detection modality for receptor-(over-)expressing tumours. DTPA derivatives of Leu(1)- and DGlu(1)-minigastrin were synthesised. All conjugates could be labelled with In-111 or Y-88/90 at high specific activities (8.5-44.4 GBq/mumol) and with high radiochemical purity. Serum stability testing was performed, and the labelled conjugates were compared concerning their stability against DTPA challenge. The biodistribution of the radiolabelled Leu(1)- and DGlu(1)-minigastrin derivatives was studied in tumour-bearing nude mice, in one healthy human volunteer and in three patients with metastatic medullary thyroid carcinoma. The transchelation of all tested radiometals to serum proteins was significantly slower with the DTPA-Glu conjugates as compared with their Leu analogues (e.g. transchelation t(1/2) of DTPA-DGlu(1)-minigastrin vs its Leu(1) analogue at 37degreesC in human serum for In-111: 239 h vs 91 h; for Y-90: 130 h vs 53 h). In animals, all labelled CCK-B receptor ligands showed fast and specific uptake in CCK-B-receptor-positive tissues, such as the stomach and tumour, as well as a fast renal clearance pattern. However, DTPA-Leu(1)-minigastrin showed higher background activity in the whole body and those organs known to accumulate the respective free radiometal (e.g. Y-88-DTPA-Leu(1)-minigastrin had bone uptake of 22%ID/g as compared to only 1.2%ID/g with its DGlu(1) analogue). In humans, fast tumour and stomach uptake was observed for both In-111-labelled compounds, but DTPA-DGlu(1)-minigastrin lacked the liver, spleen and bone marrow uptake observed with its Leu(1) analogue. In conclusion, anionic amino acid derivatives of DTPA may display improved metabolic stability as compared with monofunctional DTPA conjugates. DTPA-DGlu(1)-minigastrin is preferred to 'monofunctional' DTPA-Leu(1)-minigastrin for diagnostic application with In-111 for the in vivo detection of CCK-B receptor-expressing tissues.

BACKGROUND. Whereas radioimmunotherapy (RIT) has shown disappointing results in bulky, solid tumors, preclinical results in small-volume disease and in an adjuvant setting are promising. In a previous Phase I study, the authors had encouraging results with the iodine-131 (I-131)-labeled humanized anti-carcinoembryonic antigen (anti-CEA) antibody (MAb) hMN-14 in small-volume disease of colorectal cancer. The aim of this study was to evaluate, in a subsequent Phase II trial, the therapeutic efficacy of this I-131-labeled humanized anti-CEA antibody in colorectal cancer patients with small-volume disease or in an adjuvant setting. METHODS. Thirty colorectal cancer patients, with small-volume metastatic disease (n = 21; all lesions less than or equal to 3.0 cm, and chemorefractory to 5-fluorouracil and folinic acid) or in an adjuvant setting (n = 9), 4-6 weeks after surgical resection of liver metastases with curative intention, were studied. The patients were given a single injection of I-131 -hMN- 14 immunoglobulin G at a 60 mCi/m(2) dose level, which was shown to be the maximum tolerated dose in the previous Phase I study. Follow-up was obtained at 3-month intervals for as long as 36 months. RESULTS. At a mean blood-based red marrow dose of 1.8 +/- 0.8 Gy, myelotoxicity was the only toxicity observed, but only 1 of 28 assessable patients developed transient Grade 4 thrombocytopenia. Of the 21 patients with radiologically documented lesions, 19 were assessable. Three experienced partial remission and eight showed minor responses up to 15 months in duration (corresponding to an objective response rate of 16% and an overall response rate of 58%; the mean duration of response was 9 months). At the time this article was written, seven of nine patients in the adjuvant setting had remained free of disease for up to 36 months (one patient relapsed after 6 months and another after 30 months), whereas the relapse rate in a historical control group receiving chemotherapy was 67% over the same time period. Five patients with radiologically documented lesions, having experienced at least disease stabilization as a consequence of RIT, were retreated at the same 60-mCi/m(2) dose level at 8-16 months after the first therapy. No evidence of increased toxicity was observed (no hematologic toxicity was higher than Grade 3). Two of four assessable retreated patients experienced partial remissions; one of these four again experienced disease stabilization as a consequence of the second radioantibody therapy injection. CONCLUSIONS. These data suggest that RIT is a safe and effective form of therapy for small-volume colorectal cancer and has potential as treatment for colorectal. cancer in an adjuvant setting. Toxicity is restricted to mild and transient leuko- and thrombocytopenia. Retreatment seems to be a feasible option. A prospective randomized comparison with standard chemotherapy is indicated. Cancer 2002; 94:1373-81. (C) 2002 American Cancer Society.

Recent studies suggest a higher anti-tumour efficacy of internalizing monoclonal antibodies (MAbs) when labelled with Auger electron emitters, as compared with beta-emitters. The aim of this study was to compare the anti-tumour efficacy and toxicity of the internalizing MAb, CO17-1A, labelled with Auger electron emitters (I-125, In-111) versus conventional beta(-)-emitters (I-131, Y-90) in a colon cancer model, and to assess whether the residualizing radiometals may have therapeutic advantages over the conventionally iodinated conjugates. Biodistribution studies of I-125-, In-111- or Y-88-labelled CO17-1A were performed in nude mice bearing subcutaneous human colon cancer xenografts. For therapy, the mice were injected with either unlabelled or I-125-, I-131-, In-111- or Y-90-labelled CO17-1A IgG(2a), whereas control groups were left untreated or were given a radiolabelled isotype-matched irrelevant antibody. The influence of internalization was assessed by comparing the results with those obtained with an anti-carcinoembryonic antigen (CEA) antibody which does not internalize to a relevant extent. The maximum tolerated activities (MTA) and doses (MTD) of each agent were determined. Myelotoxicity and potential second-organ toxicities, as well as tumour growth, were monitored. Bone marrow transplantation (BMT) was performed in order to enable dose intensification. Radiometals showed significantly better tumour-to-blood ratios than the respective iodinated conjugates. The MTAs of I-131- and I-125-CO17-1A without artificial support were 11.1 MBq (300 mu Ci) and 111 MBq (3 mCi), respectively; the MTA of the metals was reached at 4 MBq (100 mu Ci) for Y-90-, and at 85 MBq (2.3 mCi) for In-111-CO17-1A. Myelotoxicity was dose limiting in all cases. BMT enabled an increase in the MTA to 15 MBq (400 mu Ci) of I-131-labelled CO17-IA, to 4.4 MBq (120 mu Ci) of Y-90-labelled CO17-IA, and to 118 MBq (3.2 mCi) of In-111-labelled CO17-1A, while the MTA of I-125-CO17-1A had not been reached at 185 MBq (5 mCi) with BMT. Whereas no significant therapeutic effects were seen with unlabelled CO17-1A, tumour growth was retarded significantly with its radiolabelled forms. The therapeutic results were significantly (P<0.01) better with both Auger electron emitters (I-125 and In-111) than with the p-emitters, and, in accordance with the biodistribution data, a trend towards better therapeutic results was found with radiometals (more complete remissions) as compared with radioiodine. In contrast, at equitoxic doses, no significant difference was observed in the therapeutic efficacy of I-131- versus I-125-labelled non-internalizing anti-CEA antibody, F023C5. These data suggest that, at equitoxic doses, the therapeutic efficacy of internalizing MAbs labelled with Auger electron emitters, such as I-125 or In-111, is superior to that of internalizing MAbs labelled with conventional beta-emitters. The lower toxicity of Auger electron emitters may be due to the short path length of their low-energy electrons, which can reach the nuclear DNA only if the antibody is internalized las is the case in antigen-expressing tumour tissue, but not in the stem cells of the red marrow).