Stanley L. Mills

Treatment of a patient with B cell lymphoma by I-131 LYM-1 monoclonal antibodies.

A patient with Richters syndrome, a malignant lymphomatous transformation of chronic lymphocytic leukemia, had become moribund with rapidly enlarging masses, granulocytopenia and thrombocytopenia despite the use of conventional chemotherapy and radiotherapy. Greater than ten percent of a test dose of I-131 Lym-1, a murine monoclonal antibody produced against Burkitts African B cell lymphoma, was accumulated by her tumor. The patient was subsequently treated with a series of injections of I-131 Lym-1 with dramatic clinical response, reduction of tumor volume by x-ray computerized tomography and progression of circulating cellular elements toward normality. Her course over the next ten months was not like that to be expected for Richters syndrome, which has an average survival of four months. This mode of treatment appears promising.

Radioimmunotherapy for breast cancer: treatment of a patient with I-131 L6 chimeric monoclonal antibody.

We report the first treatment of metastatic breast cancer by systemic radioimmunotherapy. The serial therapy doses were chosen based on quantitative imaging data in a treatment planning approach. A terminally ill patient with aggressive, locally advanced breast cancer who had failed radiation treatment and chemotherapy was injected intravenously with radiolabeled I-131 chimeric L6, a human-mouse chimeric IgG1 monoclonal antibody to adenocarcinoma. Initially, an imaging 10 mCi dose of 1-131 chimeric L6 (dose 1) deposited 8.8% of the injected dose in her chest wall tumor at 48 hours. Ten days later the patient was given a 150 mCi I-131 chimeric L6 dose (dose 2) followed three weeks later by a 100 mCi dose (dose 3). Tumor uptake and retention were comparable for doses 1 and 2, and decreased for dose 3. Following dose 3 the patient developed a manageable thrombocytopenia and transient Grade IV granulocytopenia. The tumor was observed to decrease in size with peak tumor regression occurring two weeks after dose 3. This partial response (PR) was achieved by radioimmunotherapy at a time when conventional therapy had been unable to impact the growth of the patients massive and aggressive tumor.

Quantitative imaging of mouse L-6 monoclonal antibody in breast cancer patients to develop a therapeutic strategy

L-6, a mouse IgG2a anti-adenocarcinoma monoclonal antibody (MoAb) with favorable immunopathology and mouse biokinetics, was evaluated for cancer radioimmunotherapy by pharmacokinetic studies in 10 patients with breast cancer. The effect of escalating the preinfused protein dose was studied in two patients at each level, using 50, 100, 150, 200 and 400 mg of unlabeled L-6 prior to a 10 mCi imaging dose of 131I L-6. Quantitative imaging, and blood and urine clearances were obtained. After the 50 mg preinfusion, rapid blood clearance and lung extraction of the radiopharmaceutical occurred immediately post injection. Greater preload amounts of L-6 were associated with an increase in the intercept of the slow phase of the blood clearance from 17 to 22% injected dose (ID) with 50 mg to 70 to 80% ID with 400 mg (P less than 0.01). Lung uptake of the radiopharmaceutical immediately post injection decreased from 15 to 19% ID (50 mg) to 6 to 8% ID (400 mg). Tumors were visualized only after larger L-6 preloads, but in these patients small chest tumors contained 0.6-1.2% ID (0.1% ID/g maximum). This study suggests that L-6 reactive sites that are readily available in the lung can be saturated, so that a subsequent dose of I-131 L-6 is delivered to the tumor. This approach provides a new strategy for developing an effective method for radioimmunotherapy using a MoAb that has some cross-reactivity. Quantitative imaging contributed to detection of the cross-reactivity and the strategy for overcoming it.

Immunochemical aspects of monoclonal antibodies important for radiopharmaceutical development

Successful development of radiopharmaceuticals from monoclonal antibodies will require the control of several immunochemical aspects of the antibody molecules. A proposed set of methods is presented here for evaluating these immunochemical parameters. This approach consists of monitoring each monoclonal antibody harvest by selective affinity chromatography to determine the presence of detectable alterations in molecular homogeneity. The products are then evaluated by radioimmunoassay technique standardized for total immunoglobulin immunoreactivity. These assays are utilized to detect variation in the immunoreactivity secondary to changes in the hybridoma cell lines, and to measure any detectable denaturation secondary to purification, fragment production and radiolabeling. HPLC molecular sieving chromatography is presented as a practical and informative monitor of molecular stability of these radiopharmaceuticals in vitro and in vivo.

Non-dehalogenation mechanisms for excretion of radioiodine after administration of labeled antibodies.

In patients or mice with cancer the pharmacokinetic behavior of radioiodinated and radiometal chelated antibodies has been observed to be different. Rapid clearance from the tissues and excretion into the urine can occur after injection of radioiodinated antibodies. These observations have been interpreted to reflect in vivo dehalogenation of the antibody. This publication describes a variety of other mechanisms that can underlie these phenomena. These mechanisms include receptor uptake and catabolism of antibody and instability of the labeled antibody due to the labeling conditions. Specifically, the relative masses of chloramine-T and antibody in the iodination reaction mixture, the level of iodination of the antibody, and the amount of antibody administered to the recipient are all factors which can influence the clearance of radioiodinated antibody from the recipient. The final determinant for the different behavior of radioiodinated and In-111 metal chelated antibody relate to the different biologic pathways of indium when compared to iodine

The Design of a Radiolabeled Monoclonal Antibody for Radioimmunodiagnosis and Radioimmunotherapy

Monoclonal antibodies have become recognized as promising carrier molecules for the development of target specific radiopharmaceuticals. Since the hybridoma technology can be used to discriminate small epitopes on products of either normal or abnormal cells and to produce antibodies which react uniquely with those epitopes, a new generation of biologic targets are being sought on hormones, hormone precursors, myosin, fibrin, blood cells, infectious agents, tumor cells, tumor associated antigen products and so forth. Although critical for ultimate imaging and therapeutic success, epitope recognition and appropriate target selection is only the first step toward immunologically derived radiopharmaceuticals.

EFFECTS OF PROTEIN MASS ON THE PHARMACOKINETICS OF MONOCLONAL ANTIBODIES (MoAb)

MoAb can be labeled with I-123 at high specific activities, so that only small amounts of protein are required for injection of large amounts of radioactivity for radioimmunoimaging or radioimmunotherapy. This can conserve antibody and decrease the possibilities of foreign protein reactions and target tissue binding site saturation. However, some investigators have suggested the use of milligram quantities of MoAb. In order to assess the effects on pharmacokinetics and imaging, we have administered microgram or milligram amounts of MoAb on separate occasions to 2 patients with a target tumor and 2 patients without a target tumor. Pharmacokinetics were observed in blood and urine by counting whole samples and HPLC fractions of these samples and in organs by serial imaging. Blood clearance and urinary excretion were faster during the early hours after injection of microgram amounts of MoAb, but subsequently were comparable to those obtained after milligram amounts. HPLC revealed rapid accumulation of radioiodide in the blood after microgram amounts, whereas the rate of accumulation and amount of radioiodide were less after milligram amounts. Complexes occurred earlier after milligram and later after microgram amounts of MoAb. Images confirmed rapid clearance of accumulation in stomach, thyroid and bladder. When a target cancer was present, there was also relatively greater activity in the lungs with microgram MoAb amounts compared to milligram amounts. This was not true in the absence of a target cancer. These observations have significant, but as yet, incompletely clear implications for radioimmunoimaging and radioimmunotherapy.