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M V Pimm

Publications and source records attributed to M V Pimm.

At least 37 records · Page 2Linked to original sources
PubMed1993

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.

Animals↗
PubMed1992

Evaluation of monoclonal idiotypic-specific antibodies as clearing antibodies for enhancement of target localisation by tumour-specific monoclonal antibodies: diversity of effects in nude mice with human tumour xenografts.

Three tumour-specific monoclonal antibodies (MoAbs) showed localisation in human tumour xenografts in nude mice, although the tumour discrimination was limited by the survival of a greater proportion of the MoAb in the blood and body as a whole. An attempt was made to increase tumour discrimination by the subsequent administration of syngeneic idiotypic-specific MoAbs (anti-id) directed against the first antibodies, in the expectation of clearing excess of the first MoAb from the circulation. With one MoAb (NCRC-2), its anti-id (NCRC-60) did effectively clear it from the blood, and, at least within a few hours, the tumour-to-blood ratios were increased. After longer periods, however, the tumour levels of NCRC-2 were also reduced, and the tumour discrimination was no longer increased. With another MoAb (NCRC-23) the tumour levels were reduced to a greater extent than were the blood levels in mice treated with its anti-id (NCRC-59), so that rather than being increased the tumour discrimination was actually reduced to about a third of that in control mice. With a third MoAb (NCRC-48), there was no effect on the tumour or blood levels within a few hours of injection of its anti-id (NCRC-62), and so there was no short-term effect on tumour discrimination. Subsequently, however, the tumour levels were slightly reduced, while the blood levels increased in mice treated with anti-id compared with control mice, so that the tumour-to-blood ratios decreased.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Scintigraphic evaluation of the pharmacokinetics of a soluble polymeric drug carrier.

There is a growing interest in the use of macro-molecular carriers for therapeutic agents. If these carriers can be labelled with an appropriate gamma-emitter, their biodistribution could be followed by scintigraphy. We have imaged the biodistribution of a synthetic branched polypeptide, based on a poly-L-lysine backbone (average molecular mass 45 kDa). The polymer was conjugated to diethylene triamine penta-acetic acid and labelled by chelation with indium-111. Mice were injected i.v. with labelled material and imaged with a gamma-camera with a pin-hole collimator. Images showed the majority of tracer remaining in the blood pool, but about 35% appeared in the urinary bladder within 1.5 h. When the 111In-polymer was fractionated by gel filtration chromatography on S-300, the imaging showed that the early eluting material was retained, the intermediate showed some renal clearance, and the late was rapidly excreted. These findings show the value of gamma-scintigraphy for biodistribution studies with such polymeric drug carriers and its potential for clinical pharmacokinetic studies.

Animals↗
PubMed1992

A role for gamma scintigraphy in cancer immunology and immunotherapy.

Facilities for radiolabelling and gamma scintigraphy are largely restricted to nuclear medicine departments or specialised research institutions and are therefore not widely available to workers in cancer research. Despite this, there is growing interest in gamma scintigraphy, which can provide information relevant to the entire field of cancer immunology. This review discusses the present and future roles of gamma scintigraphy in respect of antibody-targeted, cell-mediated and cytokine therapy. The authors aim to show that gamma scintigraphy is an investigative tool of great potential.

Animals↗
PubMed1992

Toxicity associated with the formation and clearance of immune complexes between antitumour monoclonal antibodies and syngeneic anti-idiotypic antibodies in mice.

We have previously shown that Balb/c mice immunised against syngeneic monoclonal antibodies (mAbs), so that they have anti-idiotypic responses against those mAbs, will clear the mAbs from the circulation as a result of immune complex formation. We report here that with three separate mAbs, this clearance of complexes can result in toxicity to the animals. This was particularly severe with one mAb (NCRC-2), in some cases leading to death. It was not seen with Fab/c or Fab fragments of NCRC-2. This toxic response could be passively transferred with serum, indicating that it was due to formation of immune complexes or to their subsequent clearance. Treatment of mice with cobra venom factor, to reduce complement levels, reduced clearance of complexes but had no effect on toxicity. The anti-histamine pyrilamine did not reduce toxicity. This is one of only a few situations in which an anti-(mouse antibody) response has been reported to be potentially dangerous, and is particularly remarkable since it occurs as a result of such a limited anti-antibody response.

Animals↗
PubMed1992

Capture of recombinant ricin A chain by a bispecific anti-RTA:anti-CEA monoclonal antibody pre-targeted to a human gastric carcinoma xenograft in nude mice.

A bispecific antibody against carcinoembryonic antigen (CEA) and ricin A chain has been shown to localise in a CEA-producing human tumour xenograft. When labelled recombinant ricin A chain was subsequently injected there was uptake into tumours, indicating that this bispecific antibody can capture or carry toxin into tumour deposits.

Animals↗
PubMed1991

Anomalies in reduction-mediated technetium-99m labelling of monoclonal antibodies.

A reduction-mediated technetium-99m labelling method has been evaluated with a range of tumour-specific monoclonal antibodies. Antibodies reduced with 2-mercaptoethanol (2-ME) had free sulphydryl groups, but their number was much higher than could be accounted for by only limited intra-chain reduction of disulphide bonds. Reduced antibody could be labelled efficiently with 99mTc using an methylene diphosphonate (MDP) bone-scanning kit, although this seemed to depend on the presence of residual 2-ME in the preparations. With a carcinoembryonic antigen (CEA)-specific antibody, immunoreactivity of labelled antibody was confirmed, and after injection into nude with CEA-producing xenografts there was localisation into the tumours. Sephacryl S300 gel filtration showed the radiolabel eluting at a single discrete peak at the expected 150 kDa. However, examination of all of the labelled antibodies by polyacrylamide gel electrophoresis (PAGE) and autoradiography showed the presence of a large number of radiolabelled low molecular weight degradation products of the antibodies. These degradation products seemed to be formed in previously reduced antibodies during processing for PAGE, indicating some fragility of the reduced antibody.

Antibodies, Monoclonal↗
PubMed1991

Influence of recombinant tumour necrosis factor alpha on blood flow and antibody localisation in human tumour xenografts in nude mice.

Mice with s.c. grafts of gastric carcinoma MKN45 or osteosarcoma 788T were injected i.v. with recombinant tumour necrosis factor alpha (rTNF alpha) and tumour blood flow rates were determined 4 h later as a fraction of the cardiac output g tissue-1. With MKN45, the tumour blood flow rate was significantly reduced from a mean of 1.86% cardiac output g-1 to 0.84% and 0.65% with 50 and 200 micrograms kg-1 rTNF alpha respectively. With 788T, the tumour blood flow rate was reduced at 50 micrograms kg-1 rTNF alpha from 1.13% cardiac output g-1 to 0.56%. There were essentially no changes in blood flow rates in other organs. The effect of rTNF alpha on localisation of monoclonal antibodies into these xenografts were examined. When a single dose of rTNF alpha (50 micrograms kg-1) was given at the same time as labelled NCRC-2 antibody there was a significant reduction in localisation into 788T osteosarcoma xenografts. In other tests, mice were injected daily for 3 days with 50 micrograms kg-1 rTNF alpha. They were injected i.v. with monoclonal antibody 4 h after the first injection and dissected on the 4th day. With 788T there was a small but not statistically significant reduction in the absolute amount of NCRC-2 antibody localising in tumour, although this reduction was greater when results were expressed as tumour-to-blood ratios. With MKN45 xenografts, treatment with rTNF alpha had little effect on tumour localisation of an anti-(carcinoembryonic antigen) monoclonal antibody (NCRC-24). These studies show that TNF can be administered so as to reduce tumour blood flow and with little effect on tumour localisation of antibody, suggesting that combination therapy with TNF and antibodies or their immunoconjugates is feasible. Other studies have suggested that TNF can increase antibody localisation into tumours, but this was not seen here, and in some cases administration could reduce tumour localisation. It appears that this method of enhancing antibody localisation may be critically dependent on scheduling, and therefore it may not be extensively applicable.

Animals↗
PubMed1991

Differences between the catabolism and tumour distribution of intact monoclonal antibody (791T/36) and its Fab/c fragment in mice with tumour xenografts revealed by the use of a residualizing radiolabel (dilactitol-125I-tyramine) and autoradiography.

Radioiodine-labelled 791T/36 monoclonal antibody (mAb) and its Fab/c fragment, consisting of one Fab arm and the Fc portion, have identical whole-body survival curves in BALB/c mice (t1/2 = 3.75 days). Therefore, these two forms of this antibody provide a suitable model for studying the role of valency in the targeting efficiency of antibodies to tumours in vivo. 791/T36 antibody and its Fab/c fragment were labelled either by direct iodination using the iodogen method (125I) or by dilactitol-125I-tyramine (125I-DLT), a residualizing label, which accumulates in the cells involved in degradation of the carrier protein. In tumour-bearing nude mice, the percentage of injected dose of mAb or Fab/c fragment reaching the specific 791T tumour was similar, and these proteins appeared to be catabolized at a similar rate in this tissue. mAb, but not the Fab/c fragment, was found to be very actively catabolized by the liver and spleen of tumour-bearing mice compared to control nude mice, this probably resulting from clearance of immune complexes. This effect was most pronounced when the mAb was labelled with 125I-DLT, the percentage of injected dose of mAb reaching the spleen and liver being higher than the percentage of injected dose reaching the tumour. This effect was not seen with the Fab/c fragment. Autoradiographic studies on tumour sections, which exhibit antigenic sites throughout the tumour mass, showed that the Fab/c fragment was already homogeneously distributed in the tumour 12 h after injection whereas the whole antibody was mainly localized at the periphery of the tumour. Those results suggest a "binding site barrier" effect. Overall, these results indicate that the highest valency and affinity may not be the optimal choice for mAb to be used for therapeutic purposes.

Animals↗
PubMed1991

Recombinant ricin toxin A chain cytotoxicity against carcinoembryonic antigen expressing tumour cells mediated by a bispecific monoclonal antibody and its potentiation by ricin toxin B chain.

A bispecific monoclonal antibody recognising both carcinoembryonic antigen (CEA) and ricin toxin A chain (RTA) was tested for its ability to target recombinant RTA (r-RTA) to CEA-expressing tumour cells, alone and in combination with ricin B chain (RTB). The antibody, 636 (Robins et al., 1990), induced significant RTA cytotoxicity against MKN45 gastric carcinoma cells which express high levels of CEA, using the r-RTA at a concentration below that known to be intrinsically cytotoxic. The addition of ricin toxin B chain (RTB) also potentiated cytotoxicity of r-RTA, and there was an additive increase in potentiation against CEA-positive cells when both RTB and 636 were included. The bispecific antibody restored potentiation by RTB after blocking of its binding site with excess galactose, and also the cytotoxic activity of whole ricin which had been blocked with galactose. It was concluded that the 636 bispecific antibody was highly effective in targeting the toxic moiety of the molecule to CEA-expressing cells, and allowed exploitation of the additional ability of the B chain to facilitate cellular incorporation. The facilitating function of the B chain was equally effective whether or not its lectin site was active.

Antibodies, Monoclonal↗
PubMed1990

Comparison of biodistribution of 791T/36 monoclonal antibody and its Fab/c fragment in BALB/c mice and nude mice bearing human tumor xenografts.

Fab/c fragments, purified from pepsin digest of mouse IgG2b monoclonal antibody (MoAb) 791T/36, consist of one Fab arm and the intact Fc portion. Pharmacokinetic and biodistribution studies in BALB/c mice of radioiodine-labeled 791T/36 MoAb and its Fab/c fragments showed that, due to the presence of the Fc portion, the Fab/c fragment has the same catabolic rate as whole antibody (T1/2 = 64 h). Due to its lower molecular weight (105,000), the Fab/c fragment extravasated more quickly and to a greater extent than whole MoAb in organs in which the vascular endothelium was fenestrated or continuous. In organs in which the vascular endothelium is sinusoidal, such as in liver and spleen, their diffusion capacities were identical. Therefore, Fab/c fragments reconcile advantages of the intact antibody molecule (slow catabolic rate) and Fab or F(ab)2 fragments (increased extravascular diffusion), features required to improve targeting to solid tumors. Data from biodistribution studies in nude mice bearing subcutaneous 791T tumor (antigen positive) and Colo205 tumor (antigen negative) contralaterally showed important differences in the behavior of whole MoAb and Fab/c fragment: (a) Whole MoAb was cleared more rapidly from the body and from the blood than Fab/c fragment; (b) The MoAb was taken up by the spleen (tissue to blood ratio greater than 1 from 12 h after injection over the 3 days of the experiment) and the liver (0.6), whereas Fab/c fragment tissue to blood ratios were only slightly increased (0.34 and 0.35) compared to control nude mice (0.25 and 0.28) for the spleen and liver, respectively, 3 days after injection. Since both MoAb and Fab/c fragment bear the Fc portion, these data suggest that the reputed "nonspecific uptake" of antibodies due to the Fc portion could be an Fc-mediated specific uptake, e.g., uptake of immune complexes; (c) The tumor to blood ratios were 1.7 and 1.2 for MoAb and Fab/c fragment, respectively, from 24 h throughout the experiment, whereas the percentage of injected dose (% of ID) present/g of 791T tumor was at any time greater for Fab/c fragment (8% maximum of ID) than for MoAb (5% of ID). These results were not expected in view of the low immunoreactivity in vitro of Fab/c fragments compared to whole antibody. It is suggested that the distribution and the catabolic rate of whole antibody and its Fab/c fragment at the tumor level are modulated by their respective valency and immunoreactivity for the target cell.

Animals↗
PubMed1990

Mouse-specific antibody responses to a monoclonal antibody during repeated immunoscintigraphy investigations: comparison of antibody titres and imaging studies in a rat model.

As a model for human mouse-specific antibody responses in patients undergoing immunoscintigraphy, we have investigated in rats the production of mouse-specific antibodies (MA) to the mouse monoclonal antibody 791T/36. At intervals of between 5 and 16 weeks the rats were given repeated cycles of intravenous (IV) injections of antibody with or without a simultaneous intradermal (ID) injection. The IV dose was 60 micrograms/kg, a dose similar to that used in many clinical immunoscintigraphy studies. The ID injection was 2 micrograms, which mimicks the skin test dose often given in clinical imaging protocols. The study was carried out with both 131I-labelled antibody and with antibody labelled with 111In by diethylenetriamine-penta-acetic acid (DTPA) chelation. MA was measured with a passive haemagglutination assay using sheep red blood cells coated with the monoclonal antibody. Of rats given ID injections of unlabelled antibody at the same time as the IV imaging doses, 9/20 produced MA during 4 cycles of injections. In contrast, only 2/16 rats given only the IV dose produced MA. Both 131I- and 111In-labelled antibody appeared equally immunogenic with 5/18 and 6/18 overall responders, respectively. The production of MA was associated with a significant perturbation in the biodistribution of the IV dose of labelled antibody as seen by gamma-camera imaging of the rats given 111In-labelled antibody. There was clearance of immune complexes to the liver, this organ accumulating up to 90% of the whole body count rate of radiolabel. MA titres of between 1/100 and 1/78,000 caused equal perturbation of biodistribution, although below 1/100 the effect was more variable.

Animals↗
PubMed1990

The influence of anti-(ricin toxin A chain) monoclonal antibodies on the pharmacokinetics of ricin toxin A chain and recombinant ricin A chain in mice.

Two monoclonal antibodies against ricin toxin A chain (RTA) have been examined for their effects on the blood survival and biodistribution of RTA and recombinant ricin A chain in mice. When admixed with the toxins at 1:1 molar ratios prior to intravenous injection, the antibodies prolonged blood survival and whole-body retention of both species of RTA, and this was due essentially to reduced renal clearance of the toxins. Immune complexes were identified by gel filtration chromatography and immune precipitation with anti-IgG antiserum in mixtures prior to injection and in the serum of mice injected with the mixtures. An irrelevant monoclonal antibody showed no complex formation, and no effect on biodistribution. These studies have shown that immune complexes formed between monoclonal antibodies and protein antigens of molecular mass up to at least 30 kDa survive in the circulation, rather than being cleared by the reticuloendothelial system. Such antibodies could be used to modulate the biodistribution of toxic molecules such as ribosome-inhibiting proteins like RTA. This might be exploited therapeutically, for example in the construction of bispecific antibodies against ribosomal inhibiting proteins and tumour-associated antigens.

Animals↗
PubMed1990

Syngeneic anti-idiotypic antibody prevents localization of a murine monoclonal antibody in human tumour xenografts.

BALB/c mice were immunized against syngeneic mouse monoclonal antibody (Mab) 791T/36 to produce anti-idiotypic antibody. To examine the effect of this antibody on tumour localization of the Mab, serum from these mice was transferred to nude mice with human tumour xenografts and distribution was studied with I-125 labelled Mab. Serum containing anti-idiotypic antibody prevented tumour localization of the Mab. This finding has implications for the clinical use of human or humanized Mab since, if these evoke anti-idiotypic antibody, this alone may be sufficient to prevent tumour targeting.

Animals↗
PubMed1990

A bispecific monoclonal antibody against methotrexate and a human tumour associated antigen augments cytotoxicity of methotrexate-carrier conjugate.

A bispecific monoclonal antibody, reactive with methotrexate (MTX) and a tumour associated antigen (gp72) has been produced by fusing spleen cells from MTX immunised mice with 791T/36/3 (anti-gp72) hybridoma. The hybrid antibody was purified from anti-MTX and anti-gp72 antibodies present in the hybridoma culture supernatant by combinations of affinity chromatography on a MTX-agarose immunoabsorbent and stepwise acid elution from Sepharose-Protein A. A particular feature of the present antibody is that it reacts with conjugated MTX; this would allow in vivo targeting of conjugates, increasing many fold the number of molecules of drug carried or localising to pre-targeted antibody. Dual binding between tumour cell surface antigen and MTX was demonstrated by the ability of the hybrid antibody to bridge between tumour cells and MTX as MTX-HSA conjugate, reaction here being detected by flow cytofluorimetry. Purified hybrid antibody specifically enhanced the in vitro cytotoxicity of MTX-HSA for gp72 positive tumour cells.

Antibodies, Monoclonal↗