M. V. Pimm

RADIOIMMUNODETECTION OF HUMAN COLORECTAL CANCERS BY AN ANTI-TUMOUR MONOCLONAL ANTIBODY

In 10 out of 11 patients with colorectal cancer radiolabelled antitumour monoclonal antibody (791T/36) was localised to the tumour. The mean tumour to non-tumour uptake ratio of antibody demonstrated by imaging with a gamma camera was 4.4/1 after subtraction of background radioactivity. The antibody did not localise in one patient who had received radiotherapy to his tumour two weeks previously. In 5 patients with primary neoplasms localisation of the antibody was confirmed by further imaging of the resected specimens and in-vitro radioactivity counting of the tumour and comparison with the activity in adjacent normal colon.

Antitumor properties of vindesine-monoclonal antibody conjugates

SummaryThe anticancer alkaloid vindesine (VDS) was conjugated to four mouse monoclonal antibodies recognizing human tumor-associated antigens. The antibodies were 96.5 (antimelanoma, IgG2a); 791T/36 (antiosteogenic sarcoma, IgG2b); 11.285.14, and 14.95.55 (anticarcinoembryonic antigen, IgG1 and IgG2a respectively). Conjugates VDS-96.5 and VDS-791T/36 were tested in vitro and shown to be specifically cytotoxic for target cells expressing the appropriate antigen. The in vivo effects of the antibodies and conjugates were tested against human tumor xenografts in athymic or immunodeprived mice using multiple treatments. Conjugate VDS-96.5 retarded the initial growth of a melanoma xenograft, whereas free antibody was without effect. Similarly, VDS-791T/36 but not free antibody retarded the growth of osteogenic sarcoma 791T. The most marked antitumor effects observed were those obtained with VDS conjugates of the anti-CEA antibodies against a colorectal tumor xenograft. Antibody 14.95.55 suppressed tumor growth both alone and as a VDS conjugate, whereas 11.285.14 produced only a slight effect alone but an almost complete and lasting suppression of tumor growth as a VDS conjugate. Free VDS had little effect at nontoxic levels. Acute studies showed that VDS-11.285.14 conjugate was considerably less toxic than free VDS in Balb/c mice.

Tumour localization of monoclonal antibody against a rat mammary carcinoma and suppression of tumour growth with adriamycin-antibody conjugates

SummaryMonoclonal antibody to the rat mammary carcinoma Sp4 isolated from hybridoma supernatants and labelled with 125I showed preferential in vivo localization into subcutaneous growths of Sp4 compared with normal tissues and a range of other transplanted tumours. No specific localization was seen with 125I-labelled normal rat immunoglobulin. Adriamycin conjugated to monoclonal antibody significantly retarded Sp4 tumour growth at 1/25th of the effective dose of the free drug, and in some cases brought about total tumour regression. Normal rat immunoglobulin-adriamycin conjugates were relatively ineffective. These studies indicate that monoclonal antibody directed against tumour cell surface antigens may be highly effective for tumour targeting of therapeutic agents.

Differences in tumour and normal tissue concentrations of iodine- and indium-labelled monoclonal antibody

The blood, tumour and whole-body levels and survivals of 131I- and 111In-labelled monoclonal antibody (791T/36) have been compared in mice with human tumour xenografts. The blood levels and survivals of 131I- and 111In-labelled antibody were similar when expressed as proportions of the injected doses. However, the whole-body survival of 111In following administration of 111In-labelled antibody was over twice as long as that of 131I after administration of 131I-labelled antibody, principally because free 131I was rapidly excreted but free 111In was retained, primarily in liver, spleen and kidneys. Consequently, when expressed in relation to the whole body, blood levels of 131In became progressively lower than those of 131I following administration of labelled antibodies. In mice with human tumour xenografts the proportion of the injected dose of 111In from 111In-labelled antibody deposited in tumour tissue was 4–5 times higher than that of 131I from 131I-labelled antibody. When compared with the whole-body levels of radiolabel the difference was less marked, although 111In accumulation in tumour was more rapid. The higher levels and longer retention of 111In in tumour produced tumour-to-blood ratios that were 7–8 times those achieved with 131I-labelled antibody.

BCG in tumor immunotherapy.

Publisher Summary This chapter discusses the biological properties of Bacillus Calmette Guerin (BCG) that are thought to have potential in stimulating host responses to malignant cells. BCG is a highly complex organism that provokes many types of host response. The chapter also describes the current status of their evaluation in experimental animal systems. Immunotherapy is the treatment of human malignant disease. This approach indicates that immunity can be induced against syngeneic transplants of experimental animal tumors, particularly those induced by chemical carcinogens and oncogenic viruses. The mechanisms of tumor rejection mediated by immune responses to tumor-associated antigens in well-defined animal systems are still inadequately understood. Due to these uncertainties, most clinical trials have adopted empirical approaches utilizing bacterial adjuvants to stimulate in a specific or a nonspecific fashion host responses to the tumor. BCG has been widely used in these approaches because of its known adjuvanticity. The chapter concludes with several guidelines along which investigation into tumor therapy could be directed.

Antitumor monoclonal antibodies for radioimmunodetection of tumors and drug targeting

SummaryDevelopments in hybridoma technology leading to the production of monoclonal antibodies recognizing tumor-associated antigens are providing new approaches for the radioimmunodetection of, and drug targeting to, metastases. These developments are illustrated in a series of studies on the in vivo localization of an antihuman-osteogenic sarcoma monoclonal antibody (791T/36) in human tumor xenografts maintained in immunodeprived mice. 131I-labelled 791T/36 antibody localized specifically in osteogenic sarcomas but not in xenografts of other tumors, such as bladder carcinoma T24, which do not express the antigen identified by this antibody. Developing from these studies, various parameters influencing antibody localization in tumors were examined including the kinetics of antibody uptake, the relationshiop between tumor size and antibody binding, and the site of antibody deposition. This provides a basis for considering the potential of antitumor monoclonal antibodies for targeting antitumor agents. Of particular importance here is the observation that antibody is principally located at the periphery of tumors since this will influence the population of cells within a tumor which can be attacked by antibody-drug or antibody-toxin conjugates.Experiments with human tumor xenografts demonstrate tumor localization of radioisotope-labelled 791T/36 monoclonal antibody. Tumor localization by external gamma camera imaging of osteogenic sarcoma xenograft-bearing mice was also demonstrated. These studies illustrate the potential of antitumor monoclonal antibodies for imaging primary and metastatic tumors. This approach is further emphasized by the radioimmunodetection of primary and metastatic colorectal carcinomas.

Prevention of renal tubule re-absorption of radiometal (indium-111) labelled Fab fragment of a monoclonal antibody in mice by systemic administration of lysine

Systemic administration of lysine to mice injected with indium-111-labelled Fab fragment of a monoclonal antibody has been shown to reduce renal uptake/retention of the radiometal. This treatment should be applicable to clinical immunoscintigraphy and radioimmunotherapy with radiometal-labelled antibody fragments.

Targeting of N-(2-Hydroxypropyl)Methacrylamide Copolymer-Doxorubicin Conjugate to the Hepatocyte Galactose-Receptor in Mice: Visualisation and Quantification by Gamma Scintigraphy as a Basis for Clinical Targeting Studies

N-(2-hydroxypropyl)methacrylamide (HPMA) copolymers containing doxorubicin and galactosamine have been developed to target the hepatocyte galactose receptor with the aim of organ-specific chemotherapy of primary and metastatic liver disease. Previous biodistribution studies in rats and mice have used tyrosinamide incorporated into the copolymer structure to permit labelling with 125I, enabling quantification of polymer distribution by dissection analysis. Radiolabelling of this copolymer with 131I, a radionuclide suitable for gamma scintigraphy, and the imaging analysis of its biodistribution in mice are reported. The present studies are the first to confirm the feasibility of imaging HPMA copolymer biodistribution, and such gamma scintigraphy will be of great value for clinical pharmacokinetic studies with this compound. Gamma scintigraphy is virtually the only non-invasive method of assessing hepatic uptake of this and similar materials.

Gamma scintigraphy of the biodistribution of 123I-labelled N-(2-hydroxypropyl)methacrylamide copolymer-doxorubicin conjugates in mice with transplanted melanoma and mammary carcinoma.

AbstractAn N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer-doxorubicin conjugate is currently under clinical evaluation as a new antitumour agent. It has been shown previously that such conjugates exhibit selective tumour accumulation. In this study HPMA copolymer doxorubicin conjugates of low (LMW) or high (HMW) molecular weight were synthesised (which had a weight average molecular weight (Mw) of 25,000 and 94,000 respectively) and additionally contained a small amount (1 mol%) of the comonomer methacryloyltyrosinamide to permit labelling with [123I or 125I]iodide. Gamma camera imaging using the I-labelled probes was used to follow time-dependent biodistribution after intraperitoneal (i.p.) or intravenous (i.v.) administration to mice bearing subcutaneously either B16F10 melanoma or a mammary carcinoma. Imaging showed more rapid clearance of LMW conjugate from the peritoneal cavity than HMW conjugate. The images of mice given the LMW conjugate revealed rapid urinary excretion of radioactivity after b...

Gamma Scintigraphy of a 123I-Labelled N-(2-Hydroxypropyl)Methacrylamide Copolymer-Doxorubicin Conjugate Containing Galactosamine Following Intravenous Administration to Nude Mice Bearing Hepatic Human Colon Carcinoma

Polymer drug conjugates composed of N-(2-Hydroxypropyl)methacrylamide (HPMA) copolymer covalently bound doxorubicin, and containing additionally galactosamine to facilitate hepatocyte-specific targeting (HPMA copolymer-dox-gal), were synthesised to contain a small amount (approximately 1 mol%) of the monomer methacryloyltyrosinamide to permit radioiodination with [123I]iodide. After intravenous administration to both normal mice and nude mice bearing hepatic human colon carcinoma, the biodistribution of the conjugate was monitored using the gamma camera, and also by dissection analysis. Efficient liver accumulation of HPMA copolymer-dox-gal was seen in the gamma camera images within 20 min, both in normal and tumour-bearing animals. Quantitatively liver uptake was approximately 40% dose administered/g liver. Images of the tumour-bearing animals showed clearly a much lower accumulation of HPMA copolymer-dox-gal in the colon carcinoma deposits within the liver (3-9% dose/g tumour), and this lack of uptake was verified by ex vivo imaging of the tumour-containing liver and also by dissection analysis. It can be concluded that 123I-labelled HPMA copolymer conjugates offer great potential as effective imaging agents and can be used for future non-invasive clinical studies. This nuclear imaging method will enable optimisation of the dosing schedule by identification of doses of HPMA copolymer-dox-gal that display receptor saturation (and hence diminished targeting efficiency). In addition this conjugate can provide negative images of liver-associated tumour deposits that do not express the asialoglycoprotein receptor.