Comparative toxicity studies of yttrium-90 MX-DTPA and 2-IT-BAD conjugated monoclonal antibody (BrE-3).

Background: BrE-3 is monoclonal antibody that has promise for imaging and therapy of human adenocarcinoma. Because of observations in therapeutic trials of yttrium-90 (90Y) escape from radioimmunoconjugates and uptake by the skeleton with resultant bone marrow toxicity, the authors attempted to evaluate the importance of this factor by a comparison of the LD50 in healthy mice treated with 90Y that had been chelated with either of two high affinity chelators, methylbenzyldiethylene-triaminepentaacetic acid (MX-DTPA) or bromoacetamidobenzyl-1,4,7,10-tetraazocyclododecane- N,N',N'',N'''-tetraacetic acid (BAD).

Methods And Results: Bone marrow hematopoietic toxicity was dose-limiting and the source of death for both chelators.

Tumor targeting in a murine tumor xenograft model with the (sFv')2 divalent form of anti-c-erbB-2 single-chain Fv.

This investigation has utilized novel forms of the single-chain Fv (sFv), wherein a cysteine-containing peptide has been fused to the sFv carboxyl terminus to facilitate disulfide bonding or specific cross-linking of this sFv' to make divalent (sFv')2. The 741F8 anti-c-erbB-2 monoclonal antibody was used as the basis for construction of 741F8 sFv, from which the sFv' and (sFv')2 derivatives were prepared. Recombinant c-erbB-2 extracellular domain (ECD) was prepared in CHO cells and the bivalency of 741F8 (sFv')2 demonstrated by its complex formation with ECD.

Highly specific in vivo tumor targeting by monovalent and divalent forms of 741F8 anti-c-erbB-2 single-chain Fv.

The in vivo properties of monovalent and divalent single-chain Fv (sFv)-based molecules with the specificity of the anti-c-erbB-2 monoclonal antibody 741F8 were examined in scid mice bearing SK-OV-3 tumor xenografts. 741F8 sFv monomers exhibited rapid, biphasic clearance from blood, while a slightly slower clearance was observed with the divalent 741F8 (sFv')2 comprising a pair of 741F8 sFv' with a C-terminal Gly4Cys joined by a disulfide bond. Following i.

Localization by whole-body autoradiography of intact and fragmented radiolabeled antibodies in a metastatic human colonic cancer model.

In this report, we have employed macroautoradiography to compare the tumor targeting of 125I-labeled anti-carcinoembryonic antigen (CEA) MAb (NP-4) to 125I-labeled anti-colon-specific antigen-p (CSAp) MAb (Mu-9) and their labeled F(ab')2 and Fab' fragments, in nude mice each bearing large dorsal human colonic tumor xenografts, and small nodular tumors in the liver and lungs. Using intact MAbs (NP-4 and Mu-9), clearance of background radioactivity was delayed to 3-7 days post-treatment. Treatment with F(ab')2 and Fab' fragments of both NP-4 and Mu-9 MAbs, however, promoted clearance of background 125I-radioactivity which was well advanced by 6-24 h and complete by 24-48 h after injection.

The effect of antibody protein dose on the uniformity of tumor distribution of radioantibodies: an autoradiographic study.

The inaccessibility of radiolabeled antibody to poorly vascularized regions of solid tumors may reduce the therapeutic efficacy of these macromolecules. Theoretical mathematical models have predicted that increasing the protein dose administered would reduce the heterogeneity of radioantibody distribution. This investigation was undertaken to evaluate this hypothesis in experimental animal models.

Selection of a DTPA chelate conjugate for monoclonal antibody targeting to a human colonic tumor in nude mice.

Our previous studies with a 90Y-labelled antibody against carcinoembryonic antigen (CEA) conjugated to the cyclic anhydride-DTPA (CA-DTPA) indicated that the accretion of 90Y in the bone may limit the application of 90Y-labelled antibodies for therapy. In this report, we have compared the tumor targeting of CA-DTPA-conjugated antibody to antibody conjugated with 4 isothiocyanatobenzyl (ITC-Bz) derivatives of DTPA in nude mice bearing a human colonic tumor xenograft. In biodistribution studies using an 111In-labelled anti-CEA murine monoclonal antibody (MAb), the CA-DTPA-conjugated MAb showed lower tumor uptake, faster blood clearance, and higher accretion in the liver than any of the 4 ITC-Bz-DTPA-conjugated MAbs.

Use of whole-body autoradiography in cancer targeting with radiolabeled antibodies.

Methods of single-tracer whole-body autoradiography (WBAR) have been developed in our laboratory which allow imaging and measurement of the zonal distribution of radioiodinated antibodies and their fragments within GW-39 colon carcinoma xenografts varying in size from large, cystic masses with necrotic cores to micrometastases. The whole-animal distribution of 90Y-labeled anti-carcinoembryonic antigen monoclonal antibody NP-2 was evaluated by WBAR in nude mice bearing s.c.

Selective delivery of boron by the melanin precursor analogue p-boronophenylalanine to tumors other than melanoma.

The melanin precursor analogue p-boronophenylalanine (BPA) has been used to deliver 10B to melanoma tissue for boron neuron capture therapy. Uptake studies in tumor models other than melanoma now indicate that BPA is capable of delivering therapeutic amounts of boron to tumors other than melanoma. The KHJJ murine mammary tumor carried s.

Optimization of boron and neutron delivery for neutron capture therapy.

A number of groups in the United States have received funding that will permit evaluation of the clinical efficacy of the neutron capture therapy (NCT) procedure. Various reactors are being modified to allow the construction of an epithermal neutron beam. At the Brookhaven Medical Research Reactor (BMRR), the patient irradiation facility is being modified to produce an optimized epithermal neutron beam.

Recent developments in neutron capture therapy.

The conditions for the possible initiation of clinical trials with neutron capture therapy at a number of locations in the U.S. is reviewed.

Radioimmunotherapy of human colonic cancer xenografts with 90Y labeled monoclonal antibodies to carcinoembryonic antigen.

Monoclonal antibodies (MAbs) to carcinoembryonic antigen (CEA) or alpha-fetoprotein (AFP) were conjugated with diethylenetriaminepentaacetic acid and radiolabeled with 90Y at a specific activity of 4.0-6.0 mCi/mg.

Whole-body autoradiographic localization of [3H]phencyclidine and its metabolites in mice.

When evaluated by whole-body autoradiography (WBAR) and quantitative densitometry, [3H]phencyclidine (PCP) equivalents were found to be removed rapidly from blood, after a single iv dose in mice, and avidly taken up as early as 1 min after dosage by glandular tissues including thyroid, salivary glands, pancreas, pituitary and, most prominently, by stomach mucosa. Stomach:blood [3H]PCP concentration ratios showed that rapid secretion of [3H]PCP from mucosa to the stomach contents occurred within 2 min after dosing. During early intervals, chromatographic analysis of tissue sections demonstrated that PCP was present in brain, liver, and gut primarily in its unaltered chemical form.

Selective targeting of boronophenylalanine to melanoma in BALB/c mice for neutron capture therapy.

Melanoma cells actively accumulate aromatic amino acids for use as precursors in the synthesis of the pigment melanin. Using the Harding-Passey melanoma carried s.c.

Relationship of radioantibody localization and cell viability in a xenografted human cancer model as measured by whole-body autoradiography.

The simultaneous distribution of monoclonal 131I-labeled anti-carcinoembryonic antigen (CEA) immunoglobulin (IgG) (NP-2) or 131I-labeled irrelevant myeloma IgG (Ag8) and [3H]thymidine was studied in hamsters bearing transplants of the GW-39 human colon carcinoma by qualitative double-tracer whole-body autoradiography. Autoradiography showed that large solid GW-39 tumors are characterized by heterogeneity of radioantibody retention and uneven [3H]thymidine accumulation, reflecting zonal variations in antibody reactivity and tumor cell proliferation, respectively. The autoradiographic images showed that both 131I-labeled-monoclonal antibody and control 131I-labeled IgG targeted nonproliferating tumor zones, suggesting a mechanism of nonspecific tumor uptake of radioantibodies in these areas.

Iodothiouracil as a melanoma localizing agent.

Thiouracil and various derivatives are selectively incorporated into the melanin pigment of melanomas during biosynthesis by serving as false melanin precursors. Using the transplantable Harding-Passey melanoma carried in BALB/c mice, we have extended our previous studies with sulfur-35 (35S) thiouracil. The persistence of high levels of [35S]thiouracil in tumor for periods of up to 2 wk has been demonstrated; during this time the drug content in normal tissues returned to near background levels.

A human colon cancer metastasis model for radioimmunodetection.

One important issue in radioimmunodetection is how well the current methods can locate and disclose small metastatic foci in visceral sites. We have developed a human colonic tumor metastasis model by surgically implanting GW-39 tumor cells in the liver of unconditioned hamsters. Tumors were produced in 71 of 73 animals and were macroscopically apparent within 1 wk.

Quantitative whole-body autoradiography of radiolabeled antibody distribution in a xenografted human cancer model.

Quantitative whole-body autoradiography (WBAR) was used to study the biodistribution of goat anti-carcinoembryonic antigen and normal goat IgG, each labeled with 125I, in hamsters bearing the carcinoembryonic antigen-producing GW-39 human colonic carcinoma xenograft. Comparisons between computer-assisted videodensitometric profiles of WBARs and tissue radioactivity counts were made at 1, 3, and 7 days following administration of the radiolabeled IgGs. The results indicated that maximal tumor accretion of the radiolabeled antibody and normal IgG occurred within 1-3 days, with a marked selective accretion of antibody in the tumor being evidenced at 3-7 days because of clearance of normal IgG.

Regional distribution of lead in the brains of lead-intoxicated adult mice.

The susceptibility of adult neural tissues to the detrimental effects of Pb poisoning has prompted the present distributional analysis of lead in the brains of chronically lead-exposed mice. A high-resolution microPIXE method was developed for measuring Pb in whole-brain cryosections derived from chronically lead-exposed mice. Spatial resolutions as small as 20 micron were obtained.

Quantitative autoradiography with radiopharmaceuticals, Part 2: Applications in radiopharmaceutical research: concise communication.

We describe the application of macroautoradiography, a relatively simple, quantifiable method for the evaluation of positron-emitting and gamma-emitting radiopharmaceuticals. We have investigated the response properties of two types of film to positron (F-18) and negatron (C-14) emitters. Variations in the response of film to increasing film-to-source distance are described, along with the effects of different intensifying screens and mounting tape.

Quantitative autoradiography with radiopharmaceuticals, Part 1: Digital film-analysis system by videodensitometry: concise communication.

A simple low-cost digital film-analysis system using videodensitometry was developed to quantitate autoradiograms. It is based on a TV-film analysis system coupled to a minicomputer. Digital sampling of transmitted light intensities through the autoradiogram is performed with 8-bit gray levels according to the selected array size (128 X 128 to 1024 X 1024).

Chlorpromazine distribution in hamsters and mice bearing transplantable melanoma.

Chlorpromazine (CPZ) distribution was measured in tissues of Syrian golden hamsters bearing Greene melanoma and in BALB/c mice bearing Harding-Passey melanoma. Distribution was evaluated as a function of time (0.5 to 14 days) and as a function of single and multiple doses (up to five) of from 5 to 50 mg CPZ per kg body weight.

Whole-body localization of 14C-tocopheryl acetate in the rat following oral administration.

The whole-body localization of dl-alpha-[3, 4-14C2]-tocopheryl acetate was examined in the rat for intervals ranging between 12-96 hr following administration of a single oral dose. Quantitative evaluation of the macroautoradiograms revealed a rapid removal of 14C-vitamin E equivalents from the blood and gut and their accumulation in body tissues. When the densitometric data were expressed as dpm/mm2, the values for radioactivity uptake by the adrenal cortex were systematically the highest of all tissues examined for all time periods.

Cilioinhibitory effect of phenothiazines in vitro and its antagonism by Ca++.

The inhibition of ciliary beating in vitro by physiologic concentrations of chlorpromazine (CPZ) and prochlorperazine (PCP) was demonstrated in two experimental systems. CPZ had a greater cilioinhibitory effect than PCP on the rotational velocity of tissue explants from the frog palate in amphibian Ringers, and on the frequency of ciliary beating in rat tracheal rings in culture medium. Addition of calcium acetate in equal molarity to CPZ, within a time limit dependent on the drug concentration, reversed this inhibition, while dibutyryl cyclic AMP did not.