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H Sands

Publications and source records attributed to H Sands.

At least 19 recordsLinked to original sources
PubMed1992

Tissue localization of methotrexate-monoclonal-IgM immunoconjugates: anti-SSEA-1 and MOPC 104E in mouse teratocarcinomas and normal tissues.

Methotrexate (MTX) was coupled to the tumor-targeting monoclonal IgM, anti-SSEA-1 and the non-targeting myeloma IgM, MOPC 104E. At 24-h intervals following injection, drug deposition in MH-15 teratocarcinomas and in several normal tissues was followed by immunoperoxidase microscopy using the M16 monoclonal antibody to MTX. MTX-anti-SSEA-1 was deposited on the surface and in the interior of living tumor cells 24 h after injection; at 48 h and after, only low-level binding to necrotic tissue was found. There was no significant gradation in staining from the outside to the interior of the tumors. In tumors, the control MOPC 104E immunoconjugate was detectable only in necrotic tissue. Binding to SSEA-1-expressing normal tissues was undetectable, except for pericryptal fibroblasts in the small intestine. No significant pathology was found in normal tissues that are SSEA-1 positive. High levels of the immunoconjugate were detected in the liver, where MTX was found predominantly in Kupffer cells and possibly in hepatocytes; again, no significant morphological changes were associated with this retention. Thus tumor-associated antigens can be suitable targets for antibody-drug conjugates even when present in normal tissues and in large quantities, provided that the antigens in normal tissues are inaccessible. Moreover, deposition in viable tumor tissue can be assessed using monoclonal antibodies to methotrexate.

Animals↗
PubMed1990

Pharmacokinetics of 99mTc-metallothionein-B72.3 and its F(ab')2 fragment.

The radionuclide of choice for use in diagnosis in most nuclear medicine diagnostic procedures is 99mTc. It is important, therefore, to establish whether there is potential clinical efficacy of an antitumor antigen directed monoclonal antibody labeled with 99mTc. We have investigated the potential use of a 99mTc labeled antibody complex which uses conjugation of the metal binding protein, metallothionein (MT), to bind the radiolabel. The stability and pharmacokinetics of the conjugates in normal and tumor bearing mice were compared to radioiodinated controls. Measurements done in CD-1 mice comparing either 99mTc-MT-B72.3 with 125I-B72.3 or 99mTc-MT-F(ab')2 with 125I-F(ab')2 indicated that the 99mTc-MT-B72.3 cleared at a rate which was faster than 125I-B72.3 while the two radiolabeled F(ab')2 fragments cleared at similar rates. The 99mTc from both labeled IgG and F(ab')2 was found in the kidneys and urine. While all the 99mTc in the urine was in the form of low molecular weight compounds, the serum contained radioactivity comigrating on size exclusion chromatography with the injected monoclonal antibody. With the exception of kidneys, organ values for 99mTc-MT-B72.3 were consistently lower than the 125I values, while the 99mTc-MT-F(ab')2 cleared other organs at similar rates to those for the iodinated monoclonal antibody. Both 99mTc-MT-B72.3 and F(ab')2 showed higher 24-h tumor:blood ratios than the iodinated proteins. Due to the pharmacokinetic properties of 99mTc-MT-F(ab')2 and the half-life of 99mTc, 99mTc-MT-F(ab')2 is the agent best suited for imaging.

Animals↗
PubMed1990

Uptake and metabolism of 111In-labeled monoclonal antibody B6.2 by the rat liver.

When 111In-labeled murine monoclonal antibodies are used in radio-scintigraphic diagnostic procedures, a large fraction of the injected radionuclide is sequestered by the liver. Neither the cells responsible for the uptake nor the mechanism of uptake are known. Little is known about either the site within the liver of antibody metabolism or the form of the products of metabolism. In these studies, the uptake and metabolism of a monoclonal antibody, B6.2 radiolabeled with 111In or 125I [either intact B6.2 or F(ab')2] were determined in rats. One h after injection of either 125I- or 111In-diethylenetriaminepentaacetic acid (111In-DTPA)-labeled B6.2, the predominant liver cell in which the radionuclide was found was the parenchymal cell. At this time, the absolute uptake of 125I in the liver was 0.23 +/- 0.06% (SD) of the injected dose compared to 0.61 +/- 0.06% when the radionuclide was 111In. Removal of the Fc portion of the antibody reduced the absolute liver uptake of 125I to 0.10 +/- 0.01 and the absolute uptake of 111In to 0.16 +/- 0.06. Both radionuclides were still associated predominantly with the parenchymal cell. Using size exclusion high performance liquid chromatography analysis of liver supernatants the metabolism of radiolabeled B6.2 was followed for 24 h. Of the radioactivity recovered, 47.9% of the 125I was precipitable by centrifugation (and presumed bound to cell membranes) while 15.4% was attached to B6.2 found in the cytosol. In contrast, when 111In-DTPA-B6.2 was administered, 16.0% of 111In recovered from the liver was precipitable by centrifugation, and 6.5% was attached to B6.2 found in the cytosol. Sixty % of the 111In was recovered as a low molecular weight (less than 1000) component in the cytosol. This metabolite was not immunoreactive, nor did it comigrate with ferritin, and was resolved into four components by ion exchange high performance liquid chromatography. Of these, only a minor component cochromatographed with an 111In-DTPA standard. These data suggest that the large accretion of radionuclide by the liver is due to uptake of monoclonal antibodies by an Fc receptor-mediated mechanism and the subsequent accumulation of low molecular weight metabolites, presumably 111In-DTPA, attached to one or more amino acids. The reasons for the entrapment of metabolites in the liver are under investigation.

Animals↗
PubMed1990

Intraperitoneal immunoconjugates.

Intracavitary instillation of radioantibodies has been proposed as therapy for anatomically confined malignant disease. To evaluate this therapeutic strategy, a monoclonal antibody reactive with human transferrin receptor (7D3) was evaluated for localization in a human malignant mesothelioma transplanted i.p. in athymic nude mice. This antibody was purified and labeled with 131I, 125I, or 111In. Radiolabeled antibody was administered i.p. or i.v. to tumor-bearing mice. Three h after injection, the percentage of injected dose/g (ID/g) of tumor was higher in free-floating ascites tumor cells (31.0%/g tumor cell pellet) after i.p. injection than after i.v. injection (12.0%). However, localization of radiolabel in i.p. solid tumors was similar (5.37% ID/g i.p. versus 4.73% of ID/g i.v.), and by 24 h both routes of administration produced similar localization of radiolabel in both free-floating ascites cells and solid tumors. In contrast, uptake of radiolabel into liver, kidney, and to a lesser extent bone and bone marrow, was less with i.p. than with i.v. administration. In clinical studies with 111In and 90Y antibodies administered i.p. to patients with ovarian cancer, confined biodistribution of the radioantibody was again seen, although interpatient variability of rate of egress of the radiolabel was documented. Therefore, both preclinical and clinical data indicate that i.p. therapy with immunoconjugates may be advantageous for cancer confined to the peritoneal cavity. This advantage stems primarily from reduced localization of isotope in organs of catabolism or toxicity (liver, kidney, bone, and bone marrow), rather than greatly increased levels of isotope in tumor. Unresolved problems include degree of antibody penetration into solid tumors, microdosimetry, and radioantibody effectiveness for tumor killing.

Animals↗
PubMed1990

Experimental studies of radioimmunodetection of cancer: an overview.

During the past 8 years numerous patients have been treated by injection of radiolabeled monoclonal antibodies for both diagnosis and treatment of cancer. It has become common to refer to this approach by such terms as "antibody guided delivery" or "antibody guided targeting." In general the results, while somewhat promising, have failed to fulfill our initial expectations. It is now clear that there are many physiological barriers that antibodies face in their travel toward their tumor associated antigen. The papers in the "Experimental Studies of Radioimmunodetection" section of the symposium describe in detail these barriers. We must remember that antibody conjugates are no more "guided" than classical drugs and hormones and are subject to the same physiological principals.

Antibodies, Monoclonal↗
PubMed1990

Physiology of monoclonal antibody accretion by tumors.

During the past 8 years numerous patients have been injected with radiolabeled monoclonal antibodies for both the diagnosis and treatment of cancer. In general the results, while somewhat promising, have failed to fulfill initial expectations. It is now clear that there are many physiologic barriers that antibodies face in their trek toward their tumor-binding site. Use of terms such as antibody-guided delivery or antibody-guided targeting do not take into account the fact that the antibodies are subject to the same physiologic rules as drugs and hormones. Antibodies are no more 'guided' than any drug or hormone. They reach their binding site via the same delivery mechanisms and accumulate in proportion to their 'receptor's' (antigen's) density. Our knowledge and understanding of the physiologic barriers to the uptake of tumor-associated monoclonal antibodies is limited. To date very few studies have been reported that shed light on this problem. For radiolabeled monoclonal antibodies to fulfill their promise, a greater understanding of these physiologic barriers is needed in order to devise ways in which they may be overcome.

Antibodies, Monoclonal↗
PubMed1989

Biodistribution and pharmacokinetics of recombinant, human 125I-interleukin-2 in mice.

The pharmacokinetics and biodistribution of radioiodinated recombinant interleukin-2 (125I-IL-2) was studied after either intravenous (i.v.) or intraperitoneal (i.p.) injection into C57BL/6 mice. Beta-lactoglobulin radiolabeled with 131I served as a control protein. After i.v. injection, 125I-IL-2 preferentially accumulated in the liver and spleen. Liver accumulation was fast, peaking at 5 min, and was followed by rapid clearance. Spleen accumulation was slightly slower, peaking at 15 min. Blood values 1 min after i.v. injection were 22-34% of the injected doses (I.D.)/gram. These values declined quickly over the next hour. In contrast, after i.p. administration no organ showed specific uptake of 125I-IL-2. Blood values after i.p. injection were essentially constant over 3 h and were greater and more sustained than after i.v. administration. Kidney values for both 125I-IL-2 and 131I-beta-lactoglobulin, after either i.v. or i.p. injection, indicated that the major route of clearance for both compounds was rapid loss through the kidneys.

Animals↗
PubMed1988

Correlation of vascular permeability and blood flow with monoclonal antibody uptake by human Clouser and renal cell xenografts.

The specific uptake of 125I-A6H antibody by xenografts of the human renal cell carcinoma (RCC) TK177G in the athymic mouse was considerably greater than that seen for other human tumor xenografts and their associated antibodies (e.g., 125I-B6.2 uptake by the human breast carcinoma, Clouser). In addition the A6H-RCC model also demonstrated both greater localization indices and absolute amount of antibody bound than did the B6.2-Clouser model. Several physiological factors were studied to assess whether they might play a role in this greater specific uptake. Vascular volume was determined using the in situ labeling of red blood cells with 99mTc. Vascular permeability was determined by measuring the amount of 125I-labeled bovine serum albumin and 131I-labeled nonspecific IgG1 (anti-horseradish peroxidase) extravasated out of the tumor vasculature during 1 hr. Relative blood flow to the tumor was determined using the 86Rb method. Blood flow and vascular permeability were found to be significantly greater in the RCC tumor xenografts than in Clouser tumors. Differences in vascular permeability were especially dramatic, showing the vasculature of the RCC xenograft was twice as permeable as that of the Clouser tumor. Animals bearing either RCC or Clouser xenografts were injected with a monoclonal antibody to human major histocompatibility complexes (125I-labeled anti-human histocompatibility complex A, B, C). Tumor uptake of 125I-labeled anti-human histocompatibility complex A, B, C was found to be 5 times greater in RCC than Clouser xenografts. These results, therefore, suggest that the differences seen in the physiological factors studied can account for some of the greater specific 125I-A6H uptake by the RCC tumor than 125I-B6.2 uptake by the Clouser xenograft.

Animals↗
PubMed1987

Tumor-specific genetically engineered murine/human chimeric monoclonal antibody.

Murine variable and human constant region exons were fused to produce "chimeric" immunoglobulin gamma and kappa genes. These constructs were cotransfected into murine myeloma cells which then produced and secreted intact, functional antibody. Cells secreting the chimeric antibody were introduced into mice. The engineered immunoglobulin was subsequently harvested from ascites fluid and was purified by affinity chromatography. Its immunological properties were compared to those of the parental murine monoclonal (B6.2), which exhibits specificity for human breast, lung, and colon carcinoma cells. Competitive binding, immunofluorescent cell staining, and analysis of immunoprecipitated antigen gave similar results for the chimeric and murine B6.2. The biodistribution of chimeric and murine B6.2 after injection into mice bearing human tumors was found to be identical. These results suggest that murine/human chimeric antibodies may be viable clinical replacements for murine monoclonals with the potential for better immunological tolerance and pharmacological efficacy.

Animals↗
PubMed1987

Pharmacokinetics of the monoclonal antibody B72.3 and its fragments labeled with either 125I or 111In.

A comparison of the pharmacokinetics of intact B72.3 (a murine monoclonal antibody specific for human breast and colon carcinoma) with F(ab')2 and Fab fragments labeled with 111In and 125I was done in athymic mice bearing target (LS174T) and non-target (HCT-15) tumors. IgG B72.3 labeled with either isotype imaged LS174T. Biodistributions of both labels were similar in all organs except liver. F(ab')2 also imaged the LS174T tumor, while Fab bearing either isotype did not. The blood clearance was Fab greater than F(ab')2 greater than immunoglobulin G B72.3 for both isotopes. 111In-labeled fragments yielded large accumulations in the kidneys which persisted for 2 days. The different patterns of biodistribution for the various forms of B72.3 labeled with the two isotopes suggest that the most desirable combination of fragment and isotope will depend on the intended use.

Animals↗
PubMed1987

Characterization of in vivo chemistry of cations in the heart.

A variety of laboratory procedures can be used to define the chemistry and pharmacokinetics of myocardial cationic imaging agents. These methods are utilized to define the in vivo chemistry of cationic heart agents, in order to understand the kinetics and mechanisms of: tissue and cellular transport, subcellular distribution, and intracellular localization. Transport across cell membranes can be active, passive or facilitated. Studies performed in erythrocytes, heart cells, slices and isolated perfused hearts using methods for separation of metabolites have shown a high degree of myocardial specificity for [99mTc]hexakis alkyl isonitrile by an uptake mechanism different from 201Tl. These studies demonstrate the importance of in vivo chemistry and pharmacokinetics in the development of new radiopharmaceuticals.

Animals↗
PubMed1987

Lymphoscintigraphy of human colorectal carcinoma metastases in athymic mice by use of radioiodinated B72.3 monoclonal antibody.

The potential of radioiodinated monoclonal antibody B72.3 for lymphoscintigraphy was evaluated, using suitable animal models of a human colorectal carcinoma. LS174T xenografts were grown at various sites in beta-estradiol-pretreated athymic mice, and the development of metastases in different organs was assessed histologically. After iv inoculation of the mice, 66% of the animals developed "metastases" to the axillary lymph nodes. Of these mice, 100% also developed multiple tumors on their backs and 79% had lung micrometastases. Livers, kidneys, and spleens showed no evidence of tumor growth. In 33% of the mice in which primary LS174T tumors had been removed from the hindfoot pad, metastases to the popliteal lymph nodes were observed 3 1/2 weeks after tumor implantation. BALB/c (nu/nu) female mice bearing axillary and popliteal lymph node metastases were used to test the potential of radiolabeled B72.3 antibody (an IgG1) as a lymphoscintigraphic agent. A monoclonal antibody against horseradish peroxidase (also an IgG1), which did not bind LS174T tumor cells in vitro, served as a control. Both normal and tumor-bearing axillary and popliteal lymph nodes imaged up to 6 hours after the sc injection of 20-40 mu Ci of 125I-labeled B72.3 into either the forefoot or hindfoot pads. The localization index (L.I.) (specific/nonspecific antibody in tumor divided by specific/nonspecific antibody in blood) for LS174T tumors in lymph nodes was approximately 1 during the first 6 hours after antibody injection, thus indicating no specific antibody accumulation. Twenty-four hours and later after sc injection, images of nodal metastases (14-477 mg) and specific antibody accumulations were observed. At these times the L.I.'s ranged 1.5-3.5. Tumor-negative nodes did not image at 24 hours after injection of 125I-labeled B72.3. The L.I.'s of the normal nodes and of other tissues from these mice were about 1.0 at 24 hours, indicating no specific antibody accumulation. Autoradiographic analysis of lymph nodes containing LS174T tumor showed heterogeneous antibody distribution of B72.3 within tumor sections with heavy patches of antibody accumulation in mucin globules. In lymph nodes the normal lymphocytes adjacent to the LS174T tumor cells showed no antibody accumulation. The lack of specific, early antibody accumulation by LS174T tumor-bearing nodes in mice suggests that B72.3 does not accumulate in nodal metastases to the degree necessary to consider it a potential agent for use in lymphoscintigraphy.

Animals↗
PubMed1987

Methods for the study of the metabolism of radiolabeled monoclonal antibodies by liver and tumor.

Methods for elucidating the mechanisms by which radiolabeled antibodies are taken up and accumulated in tumor and liver are reviewed. These include the use of isolated perfused rat livers, RES blockade using dextran sulfate, single and double labeled antibodies, micropore chambers for the accumulation of the interstitial fluid, and in vitro tissue culture studies of antibody metabolism. Each method has its utility, examples of which will be discussed along with the methods' limitations. All of the methods have value in furthering our understanding of the metabolism of monoclonal antibodies both in vivo and in vitro. Use of these procedures to create a greater understanding of radiolabeled antibody metabolism, hopefully, will result in improved clinically useful agents for diagnosis and therapy.

Animals↗
PubMed1986

Autoradiographic analysis of monoclonal antibody distribution in human colon and breast tumor xenografts.

The targeting of monoclonal antibodies to human tumor xenografts in nude mice was investigated by analysis of the cellular distribution of two radioiodinated monoclonal antibodies, B6.2 and B72.3, which recognize different tumor-associated antigens. The time course of distribution of each antibody within Clouser human mammary carcinoma (B6.2 positive, B72.3 negative) and LS174T human colorectal carcinoma (B6.2 positive, B72.3 positive) following i.v. injections was compared using autoradiographic techniques, which were also used to determine the pattern of binding after in vitro incubation with radiolabeled antibody. Both in vivo and in vitro localization of 125I-B72.3 in LS174T were characterized by the binding of antibody to antigen-rich mucin globules. In contrast, in vivo localization of B6.2 was restricted to groups of cells in well vascularized regions. Thus, the in vivo accumulations of B6.2 and B72.3 although quantitatively similar showed very different spatial distributions within LS174T tumors. The in vivo binding of B6.2 in Clouser tumors was restricted to small clusters of cells scattered fairly evenly throughout the tumor. There was no evidence for the presence of such antigen-rich foci after in vitro incubation of tumor sections with B6.2 suggesting that heterogeneity of regional uptake may be due to differences in antibody delivery. This type of information may provide a rational basis for the selection of appropriate therapeutic isotopes for radioimmunotherapy studies using these and other tumor models.

Animals↗
PubMed1986

Site-related differences in the localization of the monoclonal antibody OX7 in SL2 and SL1 lymphomas.

The uptake of a monoclonal antibody (OX7) by murine lymphomas (SL1, SL2) growing in two sites in the mouse were compared. SL2 tumors grown in the subrenal site showed greater specific antibody uptake than did the same tumor grown in the subcutaneous site. Major differences in membrane bound antibody, in vitro antibody binding patterns, and gamma scintillation camera imaging were also observed between the two sites. These differences may be due to the greater blood flow measured in tumors growing in the subrenal capsule than those growing at the subcutaneous site. The differences observed in antibody uptake of the same tumor growing in two different sites raises questions concerning the choice of animal model systems that can be used to predict clinical utility.

Animals↗