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L E Williams

Publications and source records attributed to L E Williams.

159 records · Page 9Linked to original sources
PubMedDate not supplied

Tumor targeting of radiometal labeled anti-CEA recombinant T84.66 diabody and t84.66 minibody: comparison to radioiodinated fragments.

Recombinant antibody fragments offer potential advantages over intact monoclonal antibodies in the radioimmunoscintigraphy (RIS) of solid tumors. Due to their smaller molecular size, antibody fragments have shown rapid tumor targeting and blood clearance, a more uniform tumor distribution and a lower potential to elicit a human immune response. Previously, we have expressed two genetically engineered antibody fragments, the T84.66 diabody (scFv dimer) and the T84.66 minibody (scFv-CH3 dimer), specific to carcinoembryonic antigen (CEA). When radioiodinated, both antibody fragments exhibited rapid tumor targeting and rapid blood clearance in xenografted mice. To extend and optimize their future clinical RIS utility with radiometals, these antibody fragments were conjugated with the macrocycle 1,4,7,10-tetraazacyclododecane N,N',N' ',N' "-tetraacetic acid (DOTA) and labeled with 111In. Tumor targeting and biodistribution studies were carried out in athymic mice xenografted with a human colorectal tumor cell line, LS174T. The [111In]T84.66 diabody (55 kDa) exhibited very rapid tumor targeting with 12.5 +/- 0.4% injected dose per gram (% ID g(-1) +/- standard error) at 2 h and reached a maximum of 13.3 +/- 0.9% ID g(-1) at 6 h. However, kidney uptake was observed to reached a peak of 183.5 +/- 21.0% ID g(-1) at 6 h, a result similar to that reported by others for other low molecular weight fragments labeled with radiometals. Preadministration of an oral dose of D-lysine resulted in a 59% lowering of the renal accumulation at 6 h, but was accompanied by a 31% reduction of tumor uptake to 9.2 +/- 1.2% ID g(-1). The second recombinant antibody fragment, the [111In]T84.66 minibody (80 kDa), displayed rapid tumor targeting of 14.2 +/- 6.1% ID g(-1) at 2 h, and reached a maximum activity of 24.5 +/- 6.1% ID g(-1) by 12 h. Renal uptake achieved a plateau of 12-13% ID g(-1) which cleared to 7.2% ID g(-1) at 72 h. However, hepatic uptake was elevated and reached a maximum of 26.0 +/- 1.0% ID g(-1) at 12 h in these xenograft-bearing mice. Experiments in nontumor bearing mice showed a reduction of hepatic activity at 12 h to 16.6 +/- 1.5% ID g(-1), indicative of an intrinsic hepatic accumulation of the [111In]DOTA-T84.66 minibody or metabolites. While the anti-CEA [111In]DOTA-T84.66 diabody and T84.66 minibody retain the rapid tumor targeting properties of the radioiodinated form, the normal organ accumulation (kidneys and liver, respectively) of the [111In]DOTA forms appeared problematic for RIS and RIT applications. Development of alternative blocking strategies or new metabolizable chelates are under investigation to enhance the utility of the radiometal form of these and other promising recombinant antibody fragments.

Animals↗
PubMedDate not supplied

Metabolism and renal clearance of 111In-labeled DOTA-conjugated antibody fragments.

Radiometal-labeled antibody fragments are promising reagents for radioimmunotherapy due to their high tumor uptake and rapid pharmacokinetics, but their therapeutic potentials are limited by high uptake and retention in the kidney. Identification of metabolic products is a first step in designing rationale approaches to lower kidney uptake. Previous studies in rats have shown that 111In-labeled DTPA-conjugated antibody fragments (via lysine residues) were degraded to an DTPA-epsilon-amino-lysine derivative and retained in the lysosomal compartments of the liver and kidney [Rogers et al. (1995) Cancer Res. 55, 5714s-5720s]. To determine the metabolic profile of another widely used metal-chelate, [111In]DOTA conjugated to lysines in antibody fragments via active ester chemistry, we analyzed kidney homogenates from nude mice injected with an [111In]DOTA-Fab generated enzymatically from the anti-lymphoma intact antibody Rituxan. The major kidney metabolite was identified as [111In]DOTA-epsilon-amino-lysine by comparison to an authentic synthetic standard. This end product was also identified in the urine, along with relatively small amounts of [111In]DOTA-Fab. Since injection of [111In]DOTA-epsilon-amino-lysine into nude mice resulted in rapid clearance into the urine without kidney retention, it is likely that the renal retention observed was due to kidney uptake of [111In]DOTA-Fab, followed by lysosomal degradation to [111In]DOTA-epsilon-amino-lysine, which is only slowly cleared from this compartment. This observation is supported by autoradiographs of the kidney showing rapid localization of radioactivity into the distal regions of the kidney cortex. To extend this analysis to clinical trials, we have also analyzed urine taken from a patient injected with the intact antibody [111In]DOTA-cT84.66. In that example, we found that the major radioactive species was also [111In]DOTA-epsilon-amino-lysine.

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PubMedDate not supplied

Biodistribution of 111In- and 90Y-labeled DOTA and maleimidocysteineamido-DOTA conjugated to chimeric anticarcinoembryonic antigen antibody in xenograft-bearing nude mice: comparison of stable and chemically labile linker systems.

Biodistributions of two radiometal chelate conjugates of the human/murine chimeric anticarcinoembryonic antigen monoclonal antibody cT84.66 were obtained in nude mice bearing LS174T human colorectal carcinoma xenografts. Derivatives of the macrocyclic chelating agent 1,4,7,10-tetraazacyclododecane-N,N',N",N"'-tetraacetic acid (DOTA) were covalently attached to the antibody by a stable amide linkage and by a maleimidocysteineamido side chain (MC-DOTA) that has been shown to be chemically labile at physiological temperature and pH. Biodistributions of both 111In and 90Y labels were obtained in these studies. At common biodistribution time points, it was found that the 111In label had greater uptake in the liver than 90Y for both conjugates. No significant differences were found with respect to bone uptake of 90Y using either chelate. Blood curves were generally lower at comparable time points for MC-DOTA, indicative of faster clearance as compared to DOTA. Tumor uptake was high for both conjugates (57-68% ID/g at 48 h), with a longer tumor residence time in the case of the DOTA conjugate, probably a result of its longer blood circulation times. We conclude that bone uptake of 90Y would be minimal if either DOTA or MC-DOTA were used as the bifunctional chelator. This would imply preference for these macrocyclic ligands if radiation doses to the bone marrow would be considered to be dominated by skeletal uptakes. Alternatively, if bone marrow radiation dose is dominated by circulating antibody, the chemically labile linker system employed by the MC-DOTA conjugate offers the advantage of enhanced blood clearance.

Animals↗
PubMedDate not supplied

Biodistribution and radioimmunotherapy of human breast cancer xenografts with radiometal-labeled DOTA conjugated anti-HER2/neu antibody 4D5.

HER2/neu oncogene encodes a 185 kDa trans-membrane protein which is overexpressed in 20-30% of breast and ovarian cancers and portends a poor prognosis. We have studied the targeting and therapy of this oncoprotein with 4D5, a murine monoclonal antibody which recognizes a distinct epitope on the extracelluar domain of HER2/neu. We conjugated the antibody with an active ester of the macrocyclic chelating agent DOTA, radiolabeled the conjugate with either (111)In or (90)Y, and studied the antibody distribution and therapy, respectively, in athymic mice bearing xenografts of MCF7/HER2/neu, a human breast cancer cell line transfected with the HER2/neu oncogene. For the biodistribution of (111)In-labeled DOTA-4D5, a high specificity of tumor localization (30% ID/g) was seen with a tumor-to-blood ratio of greater than 2 at 48 h postinjection. Compared to a previously published study with (125)I-labeled 4D5 in beige nude mice bearing NIH3T3/HER2/neu xenografts [De Santes et al. (1992) Cancer Res. 52, 1916-1923], (111)In-labeled 4D5 antibody gave superior antibody uptake in tumor (30% ID/g vs 17% ID/g at 48h). In the therapy study, treatment of the nude mice bearing MCF7/HER2/neu xenografts with 100 microCi (3 microg) of (90)Y-labeled DOTA-4D5 caused a 3-fold reduction of tumor growth compared to untreated controls (injected with human serum albumin) in 40 days. Treatment of animals with 100 microCi of nonspecific antibody (90)Y-labeled DOTA-Leu16 (3 microg) had no tumor growth inhibition. Treatment with unlabeled DOTA-4D5 (3 microg) had a slight effect on tumor growth compared to untreated controls. When analyzed at the level of single animals, no effect was seen in seven of nine animals; however, in two of the animals, tumor growth inhibition was observed. Although a cold antibody therapeutic effect was unexpected at this dose level (3 microg), it may be possible that in some animals that 3 microg of antibody of (90)Y-labeled DOTA-4D5 augmented tumor growth reduction. To further explore the effects of cold antibody treatment alone, animals were treated with 100 or 400 microg of unlabeled 4D5 administered in two doses. These animals showed a 1.7-1.8-fold reduction in tumor growth over 28 days, a result less than that obtained with RIT only.

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PubMedDate not supplied

A technical analysis of an intraoperative radiation detection probe.

A technical evaluation was made of a commercial intraoperative radiation probe. This device utilizes a CsI (T1) scintillation detector and light pipe arrangement to count gamma radiation in vivo. After determining the optimal window and threshold setting, additional evaluations included linearity, distance response function, detector dead time, counter reproducibility, detector sensitivity, angular resolution, and energy resolution. Detector dead time (21.2 microseconds) was found to be characteristic of a nonparalysable system. Activity response for each radionuclide was linear (R = 0.99) both with and without collimation. Energy resolution, 25% at 210 keV, was not sufficient to separate the two photons (172 and 247 keV) emitted by 111In. Detector sensitivity was 1136 and 626 counts per s per microcurie of 111In and 99mTc, respectively. The mean effective distance from the face of the uncollimated probe to the crystal was determined to be 2.03 cm in air.

Antibodies↗
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Multicellular dosimetry for beta-emitting radionuclides: autoradiography, thermoluminescent dosimetry and three-dimensional dose calculations.

Inhomogeneities in activity distributions over distances from 10 to 10(4) microns are observed in many tumors treated with radiolabeled antibodies. Resulting nonuniformities in absorbed dose may have consequences for the efficacy of radioimmunotherapy. Activity variations may be directly studied with quantitative autoradiography (ARG). Converting these data to absorbed dose distributions requires additional information about pharmacokinetics, the use of a point source function and consideration of the complete three-dimensional activity distribution, as obtained from sequential autoradiographic slices. Thermoluminescent dosimetry with specially prepared CaSO4:Dy dosimeters implanted into tissue can directly measure absorbed dose in selected regions. The conditions under which thermoluminescent dosimeters (TLD) are used differ markedly from "normal" use conditions in external beam radiotherapy. Therefore special calibration and quality assurance precautions are needed to assure the precision of this technique. Procedures and pitfalls in the use of both techniques in radioimmunotherapy are described.

Autoradiography↗
PubMedDate not supplied

Dosimetry of solid tumors.

Dosimetry data arising from a decade of radioimmunotherapy are summarized along with techniques utilized to arrive at the reported dose estimates. Generality of the MIRD methodology allows it to serve as a vehicle for the calculation of solid tumor dosimetry although several limitations exist. Nonstandard geometries of solid tumors will ultimately necessitate determination of absorbed fractions for the individual tumors. Several approaches currently under investigation are described. For reasons of practicality, solid tumor dosimetry estimates continue to use the assumption of homogeneous activity distribution in a source organ, accounting for either all radiation or only nonpenetrating radiation. As computation tools become available for incorporating inhomogeneous cellular level data, the currently used "average dose" as an index of tumor sterilization will likely be replaced with a statistical distribution based on the number of viable cells in the tumor volume. Estimates of a tumor control dose would be based upon a linear extension of dose coupled with a threshold dose for cell sterilization.

Humans↗
PubMedDate not supplied

Considerations on the calibration of small thermoluminescent dosimeters used for measurement of beta particle absorbed doses in liquid environments.

An investigation has been carried out on the factors which affect the absolute calibration of thermoluminescent dosimeters (TLDs) used in beta particle absorbed dose evaluations. Four effects on light output (LO) were considered: decay of detector sensitivity with time, finite TLD volume, dose linearity, and energy dependence. Most important of these was the decay of LO with time in culture medium, muscle tissue, and gels. This permanent loss of sensitivity was as large as an order of magnitude over a 21-day interval for the nominally 20-microns-thick disc-shaped CaSO4(Dy) TLDs in gel. Associated leaching of the dosimeter crystals out of the Teflon matrix was observed using scanning electron microscopy. Large channels leading from the outside environment into the TLDs were identified using SEM images. A possibility of batch dependence of fading was indicated. The second most important effect was the apparent reduction of light output due to finite size and increased specific gravity of the dosimeter (volume effect). We estimated this term by calculations as 10% in standard "mini" rods for beta particles from 90Y, but nearly a factor of 3 for 131I beta particles in the same geometry. No significant nonlinearity of the log (light output) with log (absorbed dose) over the range 0.05-20.00 Gy was discovered. Energy dependence of the LO was found to be not detectable, within measurement errors, over the range of 0.60-6.0 MeV mean energy electrons. With careful understanding of these effects, calibration via gel phantom would appear to be an acceptable strategy for mini TLDs used in beta absorbed dose evaluations in media.(ABSTRACT TRUNCATED AT 250 WORDS)

Beta Particles↗
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Lomustine (CCNU) for the treatment of resistant lymphoma in dogs.

Forty-three dogs with lymphoma that had relapsed or had failed to achieve complete remission to previous chemotherapy were treated with lomustine (1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea [CCNU]) at a dosage of 90-100 mg/m2 body surface area p.o. every 3 weeks. Durable complete or partial responses occurred in 11 dogs for a median of 86 days. The acutely dose-limiting toxicosis was neutropenia 7 days after administration, resulting in a recommended dosage of 90 mg/m2. Cumulative thrombocytopenia occurred in dogs receiving continued CCNU treatment, and a dose interval of 3 weeks may be too short for continued administration of this drug. Toxicoses evident as fever or central nervous system signs or renal damage were uncommon or rare. CCNU is effective in the treatment of relapsed lymphoma.

Animals↗
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Treatment of canine mast cell tumors with CCNU (lomustine).

The efficacy and toxicity of CCNU (1-[2-chloroethyl]3-cyclohexyl-1-nitrosourea) were evaluated in 23 dogs with measurable mast cell tumors (MCT). Twenty-two dogs had cutaneous MCT and 1 dog had an intranasal MCT Nineteen (83%) dogs had biopsy of their original mass performed and 4 (17%) had aspiration cytology of masses. Of the 19 tumors histologically graded, 1 (5%) neoplasm was classified as grade I, 10 (53%) were grade II, and the remaining 8 (42%) were grade III. Dogs were treated with CCNU at a dosage of 90 mg/m2 body surface area every 3 weeks. Response could be evaluated in 19 dogs. Eight of the 19 dogs (42%) had a measurable response to CCNU. One dog had a durable complete response for 440 days. Seven dogs (37%) had a partial response for a median and mean duration of 77 days and 109 days, respectively (range, 21-254 days). Treatment with CCNU resulted in stable disease in 6 dogs (32%) for a median and mean duration of 78 days and 122 days, respectively (range, 42-347 days). The acute dose-limiting toxicity was neutropenia 7 days after administration of CCNU. The median and mean neutrophil counts 7 days after CCNU were 1,452 cells/microL and 1,683 cells/microL, respectively (n = 17). Other toxicoses were uncommon. CCNU should be considered an active agent in the treatment of MCT in dogs.

Animals↗
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Evaluation of ifosfamide for treatment of various canine neoplasms.

lfosfamide (3-[2-chloroethyl]-2[(2 chloroethyl)amino]tetrahydro-2H-1,3,2-oxazaphosphorine 2-oxide) is an alkylating agent with a broad spectrum of antitumor activity. The efficacy and toxicity of ifosfamide were evaluated in 72 dogs with spontaneously occurring tumors. Forty dogs (56%) had lymphoma, 31 (43%) had sarcomas, and 1 had a metastatic carcinoma. Five dogs received ifosfamide at dosages <350 mg/m2 IV. Neither toxicity nor response were observed, and the remaining dogs received ifosfamide at 350 mg/m2 (n = 18) and 375 mg/m2 body surface area IV (n = 49). Saline diuresis and the thiol compound mesna were used to prevent urothelial toxicity. Fifty-two dogs had measurable tumors and could be evaluated for response. Complete responses were seen in 1 dog with metastatic leiomyosarcoma of the urinary bladder and in 1 dog with metastatic cutaneous hemangiosarcoma. One dog with lymphoma had a partial response for 112 days. Six dogs with splenic hemangiosarcoma received ifosfamide postsplenectomy and their median survival time was 147 days. The acute dose limiting toxicity was neutropenia 7 days after administration of ifosfamide. The median and mean neutrophil counts 7 days after ifosfamide at 350 mg/m2 were 2,035 cells/microL and 4,773 cells/microL, respectively (n = 12). The median and mean neutrophil counts 7 days after ifosfamide at 375 mg/m2 were 2,500 cells/microL and 3,594 cells/microL, respectively (n = 37). No dog developed clinical or microscopic evidence of hemorrhagic cystitis. Ifosfamide appears safe to use in tumor-bearing dogs, and the evaluation of combination chemotherapy protocols that include ifosfamide should be considered.

Animals↗
PubMedDate not supplied

Phase I evaluation of CCNU (lomustine) in tumor-bearing cats.

1-(2-Chloroethyl)3-cyclohexyl-1-nitrosourea (CCNU) is an alkylating agent in the nitrosourea subclass. A prospective evaluation of CCNU was done to determine the maximally tolerated dosage of CCNU in tumor-bearing cats. Response data were obtained when available. Twenty-five cats were treated with CCNU at a dosage of 50-60 mg/m3 body surface area. Complete hematologic data were available for 13 cats. Neutropenia was the acute dose-limiting toxicity. The median neutrophil count at the nadir was 1,000 cells/microL (mean, 2,433 cells/microL; range, 0-9,694 cells/microL). The time of neutrophil nadir was variable, occurring 7-28 days after treatment, and counts sometimes did not return to normal for up to 14 days after the nadir. Based on these findings, a 6-week dosing interval and weekly hematologic monitoring after the 1st treatment with CCNU are recommended. The nadir of the platelet count may occur 14-21 days after treatment. The median platelet count at the nadir was 43,500 cells/microL. No gastrointestinal, renal, or hepatic toxicities were observed after a single CCNU treatment, and additional studies to evaluate the potential for cumulative toxicity should be performed. Five cats with lymphoma and 1 cat with mast cell tumor had measurable responses to CCNU. Phase II studies to evaluate antitumor activity should be completed with a dosing regimen of 50-60 mg/m3 every 6 weeks.

Administration, Oral↗
PubMedDate not supplied

Evaluation of a discontinuous treatment protocol (VELCAP-S) for canine lymphoma.

Eighty-two dogs with lymphoma received a single 15-week course of chemotherapy, after which treatment was ceased until relapse. Fifty-six dogs (68%) achieved complete remission for a median 1st remission duration of 20 weeks. Forty-eight dogs relapsed, of which 30 repeated the induction cycle. In 22 of these dogs, 1st remission had been short, and they received maintenance chemotherapy; the other 8 dogs received 2 or 3 cycles of induction chemotherapy. Second remission rate for these 30 dogs was 87% (26 dogs). Overall disease control for the 38 dogs that remained on protocol was 44 weeks, which was not markedly shorter than for dogs treated with a previously reported protocol in which maintenance chemotherapy was instituted in all dogs after an identical 1st induction (VELCAP-L). Dogs that were febrile and dogs that were dyspneic were less likely to achieve a complete remission to induction chemotherapy. Of dogs that achieved a complete remission, those that were thrombocytopenic at entry had a shorter 1st remission, and dogs that were anorexic at entry had shorter overall disease control. There was a correlation between 1st remission duration and length of any subsequent remission obtained. The incidence of toxicity was high, particularly after the combination of doxorubicin and vincristine. Dose reductions because of toxicity did not markedly reduce remission duration. We conclude that discontinuous chemotherapy may reduce patient visits in a small number of patients because of long-term disease control. Delaying maintenance chemotherapy until after 2nd remission is achieved does not markedly affect overall disease control.

Animals↗