67Cu-2IT-BAT-Lym-1 pharmacokinetics, radiation dosimetry, toxicity and tumor regression in patients with lymphoma.

UNLABELLED: Lym-1, a monoclonal antibody that preferentially targets malignant lymphocytes, has induced therapeutic responses and prolonged survival in patients with non-Hodgkin's lymphoma when labeled with 1311. Radiometal-labeled antibodies provide higher tumor radiation doses than corresponding 1311 antibodies. 67Cu has an exceptional combination of properties desirable for radioimmunotherapy, including gamma and beta emissions for imaging and therapy, respectively, a biocompatible half-time and absence of pathways contributing to myelotoxicity. The radioimmunoconjugate, 67Cu-21T-BAT-Lym-1, has been shown to be efficacious in nude mice bearing human Burkitt's lymphoma (Raji) xenografts. Based on these results, a clinical study of the pharmacokinetics and dosimetry of 67Cu-21T-BAT-Lym-1 in patients with lymphoma was initiated. METHODS: Eleven patients with advanced stage 3 or 4 lymphoma were given a preload dose of unmodified Lym-1, then an imaging dose of 126-533 MBq (3.4-14.4 mCi) 67Cu-21T-BAT-Lym-1. Total Lym-1 ranged from 25 to 70 mg dependent on the specific activity of the radioimmunoconjugate and was infused at a rate of 0.5-1 mg/min. Imaging, physical examination, including caliper measurement of superficial tumors, and analysis of blood, urine and fecal samples were performed for a period of 6-13 d after infusion to assess pharmacokinetics, radiation dosimetry, toxicity and tumor regression. RESULTS: In 7 patients, in whom superficial tumors had been accurately measured, tumors regressed from 18% to 75% (mean 48%) within several days of 67Cu-21T-BAT-Lym-1 infusion. The uptake and biological half-time of 67Cu-21T-BAT-Lym-1 in tumors were greater than those of normal tissues, except the mean liver half-time exceeded the mean tumor half-time. The mean tumor-to-marrow radiation ratio was 32:1, tumor-to-total body was 24:1 and tumor-to-liver was 1.5:1. Images were of very good quality; tumors and normal organs were readily identified. Mild and transient Lym-1 toxicity occurred in 6 patients; 1 patient developed a human antimouse antibody. There were no significant changes in blood counts or serum chemistries indicative of radiation toxicity. CONCLUSION: Because of the long residence time of 67Cu-21T-BAT-Lym-1 in tumors, high therapeutic ratios were achieved and, remarkably, numerous tumor regressions were observed after imaging doses. The results indicate considerable therapeutic potential for 67Cu-21T-BAT-Lym-1.

Maximum-tolerated dose, toxicity, and efficacy of (131)I-Lym-1 antibody for fractionated radioimmunotherapy of non-Hodgkin's lymphoma.

PURPOSE: Lym-1, a monoclonal antibody that preferentially targets malignant lymphocytes, has induced remissions in patients with non-Hodgkin's lymphoma (NHL) when labeled with iodine 131 ((131)I). Based on the strategy of fractionating the total dose, this study was designed to define the maximum-tolerated dose (MTD) and efficacy of the first two, of a maximum of four, doses of (131)I-Lym-1 given 4 weeks apart. Additionally, toxicity and radiation dosimetry were assessed. MATERIALS AND METHODS: Twenty patients with advanced NHL entered the study a total of 21 times. Thirteen (62%) of the 21 entries had diffuse large-cell histologies. All patients had disease resistant to standard therapy and had received a mean of four chemotherapy regimens. (131)I-Lym-1 was given after Lym-1 and (131)I was escalated in cohorts of patients from 40 to 100 mCi (1.5 to 3.7 GBq)/m2 body surface area. RESULTS: Mean radiation dose to the bone marrow from body and blood (131)I was 0.34 (range, 0. 1 6 to 0.63) rad/mCi (0.09 mGy/MBq; range, 0.04 to 0.17 mGy/ MBq). Dose-limiting toxicity was grade 3 to 4 thrombocytopenia with an MTD of 100 mCi/m2 (3.7 GBq/m2) for each of the first two doses of (131)I-Lym-1 given 4 weeks apart. Nonhematologic toxicities did not exceed grade 2 except for one instance of grade 3 hypotension. Ten (71 %) of 14 entries who received at least two doses of (131)I-Lym-1 therapy and 11 (52%) of 21 total entries responded. Seven of the responses were complete, with a mean duration of 14 months. All three entries in the 100 mCi/m2 (3.7 MBq/m2) cohort had complete remissions (CRs). All responders had at least a partial remission (PR) after the first therapy dose of (131)I-Lym-1. CONCLUSION: (131)I-Lym-1 induced durable remissions in patients with NHL resistant to chemotherapy and was associated with acceptable toxicity. The nonmyeloablative MTD for each of the first two doses of (131)I-Lym-1 was 100 mCi/m2 (total, 200 mCi/m2) (3.7 GBq/m2; total, 7.4 GBq/m2).

Comparison of 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid (DOTA)-peptide-ChL6, a novel immunoconjugate with catabolizable linker, to 2-iminothiolane-2-[p-(bromoacetamido)benzyl]-DOTA-ChL6 in breast cancer xenografts.

Radioimmunotherapy using 131I-ChL6 antibody has shown promise in patients with breast cancer. To enhance this potential, a novel ChL6 immunoconjugate that is catabolizable and tightly binds 90Y and (111)In was developed. The immunoconjugate, 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid (DOTA)-peptide-ChL6, consists of the macrocyclic chelator DOTA linked to ChL6 by a peptide that is preferentially catabolized in the liver. The pharmacokinetic and dosimetric properties of the radioimmunoconjugates (RICs) (111)In- and 90Y-DOTA-peptide-ChL6 and (111)In- and 90Y-2-iminothiolane (2-IT)-2-[p-(bromoacetamido)benzyl]-DOTA-ChL6 were compared in athymic mice bearing HBT3477 human breast cancer xenografts. Each of the RICs was stable in vivo and concentrated well in the xenografts. Liver concentration, cumulative radioactivity (activity over time), and radiation dose of the DOTA-peptide-ChL6 RICs were one-third to one-half of those of the corresponding 2-IT-2-[p(bromoacetamido)benzyl]-DOTA-ChL6 RICs. Indium-111 RICs were imperfect tracers for corresponding 90Y RICs, although their pharmacokinetics and radiation dosimetries were similar. The results of this study were consistent with previously published in vitro data, which indicated that the peptide linker of DOTA-peptide-ChL6 was catabolized by cathepsin B. The cumulative activities and radiation doses to the liver of DOTA-peptide-ChL6 RICs were one-half of those of corresponding RICs with the 2-IT linker. Preliminary data from pilot studies in patients with breast cancer are in accord with these observations. These novel DOTA-peptide RICs seem to have excellent clinical potential for radioimmunotherapy associated with marrow transplantation, for which liver radiation is likely to be dose limiting for 90Y.

Maximum tolerated dose of 67Cu-2IT-BAT-LYM-1 for fractionated radioimmunotherapy of non-Hodgkin's lymphoma: a pilot study.

PURPOSE: Lym-1, a monoclonal antibody (MoAb) that preferentially targets malignant lymphocytes, has induced therapeutic responses in patients with non-Hodgkin's lymphoma (NHL) when labeled with iodine-131 (131I). Radiometal labeled antibodies provide a higher tumor radiation dose than the corresponding 131I labeled antibodies. Based on the strategy of fractionating the total radiation dose, this study was designed to define the maximum tolerated dose (MTD) of the first 2, of a maximum of 4, doses of 67Cu-2IT-BAT-Lym-1 given 4 weeks apart. Additionally, toxicity, radiation dosimetry and efficacy were assessed. MATERIALS AND METHODS: Patients had Ann Arbor stage IVB NHL, resistant to standard therapy, including multiple chemotherapy regimens. Each dose of 67Cu-2IT-BAT-Lym-1 was given after a preload of unmodified Lym-1. A 10 mCi imaging dose of 67Cu-2IT-BAT-Lym-1 was given in order to assess pharmacokinetics and radiation dosimetry prior to therapy. Based on the MTD for 131I-Lym-1 and comparative dosimetry for 131I-Lym-1 and 67Cu-2IT-BAT-Lym-1, the trial was initiated at 60 millicuries per square meter of body surface area (mCi/m2) in cohorts of 3 patients. RESULTS: A single cohort of patients proved sufficient to define the MTD as 60 mCi/m2 for each of the first 2 doses of 67Cu-2IT-BAT-Lym-1. The dose-limiting toxicities were grade 3-4 thrombocytopenia and neutropenia. Neutropenic sepsis and bleeding did not occur. Mean radiation dose contributed to the bone marrow by 67Cu in the body and blood was 0.2 (range, 0.2 to 0.3) rads/mCi. Copper-67 incorporated into ceruloplasmin contributed 25% of the dose to marrow from blood. Non-hematologic toxicities did not exceed grade 2. The three patients had substantial tumor regression even after imaging doses of 67Cu-2IT-BAT-Lym-1. After therapy, one response was complete with a duration of 12 months. Radiation doses to tumors in this patient varied from 7.0-21.9 rads/mCi or 5420-7000 total rads from the course of therapy. CONCLUSION: 67Cu-2IT-BAT-Lym-1 provided good imaging, favorable radiation dosimetry and a remarkably high therapeutic index (ratio of tumor to marrow radiation doses). The non-myeloablative MTD for each of 2 doses was 60 mCi/m2.

Yttrium-90-DOTA-peptide-chimeric L6 radioimmunoconjugate: efficacy and toxicity in mice bearing p53 mutant human breast cancer xenografts.

UNLABELLED: The novel radioimmunoconjugate, 90Y-DOTA-peptide-chimeric L6 (ChL6), was designed to reduce radiation to critical normal tissues with an exceptionally stable 90Y chelate moiety and a biodegradable linker. Human breast cancer tumors (HBT 3477) in mice were treated with 90Y-DOTA-peptide-ChL6 to examine the effects of increasing dose on the therapeutic efficacy and toxicity of this new agent. METHODS: Groups of athymic mice bearing HBT 3477 xenografts received 4.1- to 14.1-MBq doses of 90Y-DOTA-peptide-ChL6 intravenously. The lethal dose (LD)(50/30), general well-being (weight loss), hematotoxicity and therapeutic efficacy were studied. RESULTS: The LD(50/30) was 12.8 MBq, which corresponded to doses of 17.9 and 50.9 Gy to the total body and tumor (200 mm3), respectively. Deaths were associated with hematotoxicity; no deaths occurred at doses of 9.6 MBq or less. At sublethal doses, the rate of tumor response (cures +/- complete responses + partial responses) increased with increasing dose: 4.1 MBq, 27%; 5.9 MBq, 41%; 8.5 MBq, 69%; and 9.6 MBq, 79% (maximum tolerated dose, MTD). In mice receiving doses of 4.1-9.6 MBq, 6 of 74 (8%) of tumors were cured. Increasing the 90Y dose led to smaller tumor size at nadir and longer tumor regrowth delay but no increase in cure. Although the HBT 3477 p53 gene was found to be mutant resulting in p53 protein not binding DNA breaks, tumors at MTD demonstrated evidence of apoptosis. CONCLUSION: In the human breast cancer athymic mouse model, 90Y-DOTA-peptide-ChL6 had a high therapeutic index and LD(50/30) leading to a 79% response rate at the MTD. The evidence of apoptosis as a mechanism for this tumor response in p53 mutant breast cancer warrants further studies because these observations are relevant to the treatment of lethal breast cancer.

Effects of radiolysis on yttrium-90-labeled Lym-1 antibody preparations.

UNLABELLED: The physical half-life of 2.6 days and 2.2 MeV beta emissions of 90Y provide excellent properties for radioimmunotherapy applications. However, the clinically useful beta particles may be a source of radiation-induced damage of 90Y-labeled immunoconjugate radiopharmaceuticals during preparation or short-term storage. The stability of 90Y-labeled Lym-1 antibody was studied in standard radiopharmacy conditions to establish a formulation at which radiolysis is not a problem. METHODS: Lym-1-21T-BAD immunoconjugate intermediate was prepared according to our standard procedure, then labeled with 90Y at 1, 2, 4 and 9.4 mCi/mg Lym-1 using 0.5 M tetramethylammonium acetate, pH 7, labeling buffer. Each mixture was challenged in diethylenetriaminepentaacetic acid to remove nonspecifically bound 90Y. The 90Y-21T-BAD-Lym-1 products were purified by centrifuged molecular sieving column chromatography. The radiochemical purity and immunoreactivity of each preparation was monitored daily by high-performance liquid chromatography (HPLC) and solid-phase radioimmunoassay, respectively, for 3 days. The preparation at 2 mCi/mg was also formulated in 4% (wt/vol) human serum albumin (HSA) overall and at 9.4 mCi/mg in five-fold water, 4 and 10% (wt/vol) HSA overall; all were monitored as above. RESULTS: The monomeric quality and purity profile of products at 1 and 2 mCi/mg were retained (> or = 80%) as was their immunoreactivity (> or = 75%) over 3 days. The radiochemical purity and immunoreactivity of the product at 4 mCi/mg declined to 65% and 28%, respectively, by 3 days after preparation and in just 48 hr, the product at 9.4 mCi/mg had degraded to 21% in radiochemical purity with only 3% immunoreactivity. The current HPLC data and earlier published chromatographic evidence did not support a compromised radiochemical integrity of 90Y-DOTA complexes by loss of 90Y from the DOTA chelate. CONCLUSION: Radiolysis of 90Y-labeled antibody preparations did not appear to be a problem at 90Y-21T-BAD-Lym-1 products < or = 2 mCi/mg. Human serum albumin proved to be an effective radioprotectant as the initial 100% immunoreactivity of the product at 2 mCi/mg was retained for 72 hr. The results underscore the need for appropriate formulations and dilutions of clinical doses of 90Y immunopharmaceuticals immediately after manufacture.

Radioimmunotherapy for breast cancer using indium-111/yttrium-90 BrE-3: results of a phase I clinical trial.

UNLABELLED: BrE-3 is a murine IgG1 monoclonal antibody that binds to 97% of human ductal breast cancer specimens. A previous study documented the ability of 111In-labeled 1,4-methyl-benzyl isothiocyanate diethylenetriamine pentaacetic acid (111In-MX-DTPA) BrE-3 to specifically target breast cancer tissue in patients, and the dosimetry derived from the pharmacokinetics suggested that a useful therapeutic index could be obtained with 90Y-MX-DTPA BrE-3. A Phase I maximum tolerated dose study was, therefore, initiated. METHODS: Six patients received 111In/90Y-MX-DTPA BrE-3, three of them receiving 6.25 and the other three receiving 9.25 mCi/m2 of 90Y. Pharmacokinetics, dosimetry, human anti-mouse antibody (HAMA), toxicity and clinical responses were evaluated. RESULTS: Three of six patients demonstrated a minor and transient, but objective tumor response, and none of the patients had significant toxicity. Tumor dosimetry ranged from 39 to 167 rad/mCi of 90Y (442-1887 rad/ dose). HAMA response occurred in five of six patients. CONCLUSION: Minimal toxicity, dosimetric calculations and clinical assessment indicate that a useful therapeutic index can be achieved with this therapy. Indium-111/yttrium-90-MX-DTPA BrE-3 can be safely administered to patients with metastatic breast cancer, and therapy doses yielded pharmacokinetics similar to those of tracer doses. Clinical responses, albeit transient, were achieved with single-dose therapy. Rapid onset of the HAMA response will hinder multicycle therapy, unless it is prevented with immunosuppressive drugs or the use of a "humanized" antibody. Further studies are needed to determine the optimal use of BrE-3 for radioimmunotherapy.

Radioassay of yttrium-90 radiation using the radionuclide dose calibrator.

UNLABELLED: Yttrium-90 is used in radioimmunotherapy because of its favorable physical half-life and energetic pure beta emissions. However, it is often necessary to standardize 90Y sources to establish a dose calibrator dial setting for accurate calibration of clinical doses of 90Y preparations. METHODS: A solution of 90YCl3 containing 2.81 kBq/ml (by supplier's calibration) was prepared by serial dilution In 0.05 M HCl. Ten 100-microliters aliquots of this solution were counted in a Packard liquid scintillation analyzer; the mean radioactivity in becquerels was determined and used to evaluate dial settings 48 x 10,775 x 70 and 775 x 100 on a radionuclide dose calibrator for 90Y measurements. The dose calibrator response was also studied on 90Y sources at varying solution volumes in plastic and glass containers. RESULTS: Calibrator readings of 90Y sources in glass and plastic vials and plastic syringes were accurate at either dial setting 48 x 10 (commonly used by many 90Y laboratories) or 775 x 70. Measurements of 1.15 and 3.03 GBq (31 and 82 mCi, respectively) calibrated 90Y sources in either vial were -3.0 and +4.3%, respectively, at dial-setting 775 x 70 and -4.0 and +9.0% at 48 x 10. Yttrium-90 sources in plastic syringes gave higher readings than those in glass vials, therefore, requiring a container correction factor for accurate dose assay. Measurements of 90YCl3 shipments from four suppliers over a 3-yr period demonstrated concurring calibration measurements at both 775 x 70 and 48 x 10 settings for shipments from all suppliers. The dose calibrator response to 90Y radiation was linear within a 1-333 kBq range in a constant sample volume of 580 microliters. CONCLUSION: This work demonstrates the validity of using the 48 x 10 dial-factor combination on the standard radionuclide dose calibrator for calibration of 90Y radiopharmaceuticals.

Yttrium-90/indium-111-DOTA-peptide-chimeric L6: pharmacokinetics, dosimetry and initial results in patients with incurable breast cancer.

BACKGROUND: Radioimmunotherapy (RIT) using 131I-Chimeric L6 (ChL6) antibody has shown therapeutic promise for patients with breast cancer. To enhance this potential, a novel immunoconjugate was developed that targets adenocarcinomas like breast cancer and tightly binds yttrium-90 (90Y) for therapy and indium-111 (111In) for imaging. The radioimmunoconjugate consists of a macrocyclic chelator (DOTA) linked to ChL6 by a catabolizable peptide. 90Y-DOTA-peptide-ChL6 was designed to minimize the radiation dose to critical normal tissues, thereby improving the therapeutic index. MATERIALS AND METHODS: Three patients with incurable metastatic breast cancer received 90Y/111In-DOTA-peptide-ChL6 for 5 pharmacokinetics/dosimetry studies and one of these patients also received 2 therapy doses. Quantitative imaging of 111In and in vitro assay of 90Y and 111In in blood urine and bone marrow samples were obtained. RESULTS: 90Y/111In-DOTA-peptide-ChL6 was prepared at high purity and was stable in vivo. Assays of bone marrow revealed no evidence for escape of 90Y or 111In from the chelate. 111In imaging of tumors was excellent, providing a therapeutic index for tumor to marrow radiation as high as 229 to 1. 90Y and 111In provided comparable pharmacokinetics, as did tracer and therapeutic doses of radioimmunoconjugates. One patients that received 2 therapeutic doses of 90Y-DOTA-peptide-ChL6 showed regression of tumors and tumor markers. Toxicities were relatively minor and no anti-globulin response developed despite 5 immunoconjugate infusions. CONCLUSIONS: This first study in patients of radioimmunoconjugates with a catabolizable linker between the metal chelator and the antibody confirmed that these novel 90Y/111In-DOTA-peptide-ChL6 radioimmunoconjugates have significant potential. Tracer doses of 111In-DOTA-peptide-ChL6 for imaging predicted the behavior of therapeutic doses of 90Y-DOTA-peptide-ChL6. The latter radioimmunoconjugate induced regression of tumors and tumor markers without significant toxicity. When compared to earlier 131I-ChL6 dosimetry, 90Y-DOTA-peptide-ChL6 provided a therapeutic index several times better.

Analysis of long-lived radionuclidic impurities in short-lived radiopharmaceutical waste using gamma spectrometry.

Large hospitals and biomedical research centers utilize decay-in-storage programs to minimize the volume of their low level radioactive waste. However, some medically useful radionuclides often contain small amounts of long-lived radionuclidic impurities which may complicate simple waste management procedures. We have evaluated the extent of this problem in low level radioactive waste involving 67Cu and (111)In over a 6-mo cycle of decay-in-storage by identifying the residual radionuclides in our dry waste using a multichannel analyzer. The multichannel analyzer was also used to quantify the radionuclide constituents of our liquid waste at the beginning of a decay-in-storage cycle. Radionuclides were identified by the presence of characteristic photopeaks of each isotope in the gamma spectrum and quantified by region of interest analysis. After a decay-in-storage cycle, long-lived 58Co, 57Co, and 56Co isotopes were observed in dry 67Cu waste and (114m)In identified in dry (111)In waste. The (114m)In was detected in dry (111)In waste containing initial (114m)In activity of 740 kBq (20 microCi), while the cobalt radionuclides were detected in dry 67Cu waste containing initial 58Co, 57Co, and 56Co activities of 444, 148, and 148 kBq (12, 4, and 4 microCi), respectively. Such dry low level radioactive waste was thus disqualified from short-term radioactive waste storage programs. The radionuclide constituents in the liquid waste were quantified in microCi mL(-1) and confirmed to be within the Nuclear Regulatory Commission set limits of 2 x 10(-4), 6 x 10(-4) and 6 x 10(-5) microCi mL(-1) for 58Co, 57Co, and 56Co, respectively, before disposal. The highest levels of long-lived isotopes that have been found in our liquid low level radioactive waste at the beginning of decay-in-storage were 5.5 x 10(-4), 4.8 x 10(-4), and 1.4 x 10(-4) microCi mL(-1) for 58Co, 57Co, and 56Co, respectively. Gamma spectrometry can be used to aid waste segregation and final management decisions on low level radioactive waste.

Dosimetric evaluation of copper-64 in copper-67-2IT-BAT-Lym-1 for radioimmunotherapy.

UNLABELLED: Copper-67 (67Cu) is an attractive radionuclide for radioimmuno-therapy because of its favorable physical and biologic characteristics. Current supplies of 67Cu, however, contain as much as 60% of 64Cu at the time of delivery. Scatter photons from 64Cu enter the 67Cu energy window, affecting image resolution and counting accuracy. The radiation dose to tissue is also altered. METHODS: A line source and a small vial source of 67Cu containing varying amounts of 64Cu were used to evaluate the impact of 64Cu on image resolution and activity quantitation, respectively. Identical pharmacokinetics for 67Cu and 64Cu was assumed, and the radiation dosimetry of 64Cu was assessed using quantitative imaging data for 67Cu because the amount of 64Cu could be calculated for any time after 67Cu production. MIRD formalism was used to estimate the therapeutic index, defined as the ratio of radiation dose to tumor divided by the radiation dose to bone marrow. RESULTS: As the amount of 64Cu increased, the full width at tenth maximum of the line spread function increased, although there was no significant change in full width at half maximum. The number of scatter counts from 64Cu increased as the amount of 64Cu or the size of the source region of interest increased. When 64Cu was 25% of the total activity, less than 10% of the total 67Cu photopeak counts detected with a scintillation camera were attributable to 64Cu. Although the tumor radiation dose per unit of activity (cGy/GBq) from 67Cu was five times greater than that from 64Cu, the marrow dose (CGy/GBq) from 67Cu was only three times greater than that from 64Cu. Therefore, the therapeutic index was diminished by the presence of 64Cu. When 64Cu radioimpurity was less than 25% of the total activity, there was less than a 10% decrease in the therapeutic index. CONCLUSION: The shorter physical half-life of 64Cu relative to that of 67Cu and slower uptake and longer retention of antibody by tumor than by marrow result in a lower therapeutic index for 64Cu. The 25% radioimpurity of 64Cu causes less than 10% deviation in activity quantitation and diminution in the therapeutic index. The change in therapeutic index is predictable over time and can be used to determine the optimal time for radiopharmaceutical administration.

Prelabeling of chimeric monoclonal antibody L6 with 90yttrium- and 111indium-1,4,7,10-tetraazacyclododecane-N,N',N",N"'-tetraacetic acid (DOTA) chelates for radioimmunodiagnosis and therapy.

90Y and 111In have been attached to chimeric monoclonal antibody L6 with a bifunctional chelating agent (DOTA-peptide isothiocyanate). The bifunctional chelating agent was prelabeled with either radiometal and then conjugated to the antibody. Studies in human patients showed excellent 111In single-photon emission computed tomography images of breast cancer lesions 24 h after injection.

Pharmacokinetics of chimeric L6 conjugated to indium-111- and yttrium-90-DOTA-peptide in tumor-bearing mice.

UNLABELLED: A bifunctional chelating agent, DOTA-Gly3-L-(p-isothiocyanato)-phenylalanine amide (DOTA-peptide-NCS), was studied in nude mice bearing human breast cancer xenographs (HBT 3477) to determine its potential for radioimmunoconjugate therapy. METHODS: Indium-111 and yttrium-90 were attached to an anti-adenocarcinoma chimeric L6 (ChL6) monoclonal antibody (MAb) after pre-chelation to the DOTA-peptide-NCS and the desired neutral radiochelates were obtained by purification. The unique characteristic of the DOTA-peptide-NCS to form neutral complexes with trivalent metals was utilized to separate the resulting 111In and 90Y radiochelates from excess chelating agent and other anionic by-products resulting from metal impurities. The purified radiochelates were then conjugated to ChL6. The pharmacokinetics of 111In- and 90Y-DOTA-peptide-ChL6 were obtained for 5 days after injection in nude mice bearing HBT 3477 xenographs. The results were compared with the pharmacokinetics of 125I-ChL6 obtained in the same mouse model. RESULTS: The whole-body clearance of 125I-ChL6, 90Y- and 111In-DOTA-peptide-ChL6 was monoexponential with biologic half-times of 92, 104 and 160 hr, respectively. Blood clearances of the three radiopharmaceuticals were biphasic. The radiometal immunoconjugates had greater tumor uptake and slower clearances. CONCLUSION: Indium-111- and 90Y-DOTA-peptide-ChL6 can be produced at high specific activity with fewer than one chelate per MAb by using a pre-labeling method that permits radiochelate purification by charge selection. Studies in mouse xenografts indicate that tumor uptake is enhanced and a favorable therapeutic index is achieved using these agents.

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. The LD50 for 90Y-BrE-3-MX-DTPA was 220.9 microCi, and that for 90Y-BrE-3-2IT-BAD and was 307.8 microCi. Whole-body autoradiography revealed substantially greater uptake of 90Y in the skeleton when MX-DTPA was used as the chelator. CONCLUSIONS: These observations suggest that 90Y escape to bone is a significant factor in the maximum tolerated dose of radioimmunoconjugate that can be used in therapeutic trials. These results probably underestimate the importance of 90Y escape since 90Y in the skeleton of patients is likely to be more significant than in mice because more of the 90Y energy is absorbed in the marrow of larger species.

A comparative study of copper-67 radiolabeling and kinetic stabilities of antibody-macrocycle chelate conjugates.

BACKGROUND: The development of new chelating agents and radiolabeling protocols is essential to progress in radioimmunotherapy with antibody-chelate conjugates. METHODS: Immunoconjugates of four polyazamacrocycles with N-bonded acetate groups were prepared by conjugation via 2-iminothiolane to Lym-1, a murine antilymphoma immunoglobulin G2a MoAb. To optimize 67Cu radiolabeling, complexation conditions were explored. The kinetic stabilities in vitro in human serum of four 67Cu labeled immunoconjugates were investigated. RESULTS: Lym-1-2IT-6-BAT-67Cu, the chelate conjugate of 6-[p-(bromoacetamido)benzyl]-1,4,8,11-tetraazacyclotetradecane- N,N',N''N'''-tetraacetic acid, exhibited excellent kinetic stability in human serum, while Lym-1-2IT-2-BAT-67Cu, prepared from the structural isomer 2-[p-(bromoacetamido)benzyl]-1,4,8,11- tetraazacyclotetradecane-N,N',N'',N'''-tetraacetic acid, exhibited a markedly higher rate of loss of radiometal. It was observed that the radiolabeling ratio of Lym-1-2IT-6-BAT-67Cu, in mCi per mg immunoconjugate, was limited solely by the specific activity of the radiometal, which varied significantly from lot to lot. This ratio for a given lot of 67Cu can be predicted by a preliminary titration. CONCLUSIONS: The preparation of 67Cu labeled immunoconjugates of therapeutic quality has been improved by the determination of optimum radiolabeling conditions, and by development of a titration protocol which rapidly and accurately predicts the radiolabeling ratio in mCi per mg immunoconjugate. The surprising difference in the properties of 6-BAT and 2-BAT shows the exquisite dependence of kinetic stability on structure.

The effect of different extraction methods on the antiglycolytic and antiureolytic properties of Sorindeia warneckei--a Nigerian chewing stick.

Experiments were carried out to determine the best partition reagents for extracting the active biological agents in Sorindeia warneckei--chewing stick. Results show the Soxhlet extraction method to be the most effective.

A quantitative assessment of the Nigerian mothers' ability to prepare salt-sugar solution for the home management of diarrhoea.

This study aimed at assessing qualitatively and quantitatively the ability of Nigerian mothers to prepare salt-sugar solutions (SSS) (according to the Nigerian standard formula) under the usual home environment. Mothers were provided with the ingredients but not with measurement spoons nor containers. 274 mothers randomly selected from a peri-urban community participated in the study. Of the 192 (70.1%) who claimed knowledge on SSS preparation, only 47 (24.5%) gave a correct description of its constitution and 103 (54.2%) were willing to prepare the solution. Of the 103 who prepared the solution, 34 (33.0%) used the correct number of teaspoons of salt and of sugar. The composition of the solutions prepared by the mothers varied greatly with sodium levels ranging from 0-760 mmols/l (mean 225.8 +/- 155.3, median 177.3) and glucose, 0-262.6 mmols/l (mean 68.7 +/- 54.4, median 52.0). Only 7 mothers (6.8%) prepared solutions with acceptable sodium and glucose levels. It is concluded that salt-sugar solutions prepared by Nigerian mothers are not safe. There is a great need to review the oral rehydration therapy (ORT) promotion strategies and messages in order to avoid the dangers associated with improperly constituted solutions.

PIP: In June-August 1989, in Nigeria, the College of Medicine at the University of Lagos conducted qualitative and quantitative assessments to determine mothers' ability to make salt-sugar solutions (SSS) under typical home conditions to manage diarrhea in their children. 234 (85.4%) of the 274 mothers knew about oral rehydration therapy (ORT) and 192 (70.1%) said that they knew how to prepare SSS. Just 47 (24.5%) of the mothers who knew the recipe for and how to prepare SSS could actually describe the correct recipe. Only 103 (37.1%) of the mothers claiming to know the recipe were willing to prepare SSS. Just 34 (33%) of these mothers used the right number of teaspoons of salt and sugar to prepare SSS. Most mothers (92.2%) used the correct amount of water (600 ml equal to the volume of 1 standard beer bottle or 2 bottles of soft drink). Considerable variability occurred in both the sodium and glucose levels of the SSS prepared by mothers (range = 0-760 mmols/l, mean = 225.8 mmols/l, median = 177.3 mmols/l, and range = 0-262.6 mmols.l, mean = 68.7 mmols/l, median = 52 mmols/l, respectively). High sodium content ( 100 mmols/l) and low glucose content ( 50 mmols/l) were the norm for SSS that mothers prepared (92% and 49.5%, respectively). Just 7 (6.8%) of the mothers made SSS within the acceptable range for sodium and glucose. These findings showed that SSS prepared at home in Nigeria is dangerous, indicating a need to reexamine ORT promotion strategies and messages to prevent the risks linked to incorrectly prepared solutions. The Nigerian Federal Ministry of Health could also target ORT messages to primary school pupils and teachers to expand SSS knowledge and correct preparation. Standard plastic measurement cups clearly marked and indicating salt and sugar levels could help achieve compliance.

Radioimmunolocalization of metastatic breast carcinoma using indium-111-methyl benzyl DTPA BrE-3 monoclonal antibody: phase I study.

Pharmacokinetics of radiolabeled BrE3 monoclonal antibody (Mab), reactive against a breast mucin epitope, were assessed in 15 patients with advanced breast cancer. Patients received 5 mCi (185 MBq) of 111In-methyl benzyl isothiocyanate DTPA (MX-DTPA) conjugated BrE-3 Mab intravenously with total antibody doses of 10, 50 or 100 mg. Serial quantitative imaging, blood and urine clearance were obtained to measure pharmacokinetics, assess tumor localization and estimate radiation dose. Organ function was followed to determine toxicity. Mild allergic reactions occurred in four patients. Eighty-six percent of 70 known lesions and 5 unsuspected lesions were detected by antibody imaging. Biexponential modeling of radiolabeled antibody in serum showed a T1/2 alpha = 9.5 +/- 2.7 hr and T1/2 beta = 56 +/- 25.4 hr. Total urinary excretion averaged 35.5% +/- 19.3% injected dose (ID) by Day 8. Quantitative imaging showed that 0.02-2.56% ID localized in tumors. Extrapolating dosimetry from 111In-MX-DTPA-BrE-3 to 90Y-MX-DTPA-BrE-3, we estimate therapeutic radiation doses could be delivered to some tumors with tolerable toxicity.

Structure-distribution relationship studies of 99mTc-2,3-diamine complexes.

In order to develop an organ specific radiopharmaceutical a structure-distribution relationship study was carried out in mice using a homologous series of cationic 99mTc-2,3-diaminoalkanes. The results showed that specific organ uptakes were uniformly low, generally less than 5% of the injected dose. Rapid removal of the lower homologues from the circulation through the excretory organs and an excessive blood retention of the higher homologue complexes were observed. Evidence of preferential renal clearance (over the hepatobiliary clearance) by the complexes was obtained from both linear and multiple regression analyses. Using the combined biodistribution data for the cationic diamino complexes and the equivalent anionic 99mTc-2,3-dioximinoalkane complexes, the multiple correlation was evaluated between the % urinary tract uptake data at 4 h post injection and a combination of log P, molecular diameter and charge (+1 or -1) of the complexes. From the magnitude and sign of the coefficients in the equation for the regression line, it was found that the dependence of the amount of complex cleared renally on the physico-chemical parameters tested is in the order; log P, cationic charge and molecular diameter.

Structure-distribution relationship studies of 99mTc-2,3-dioxime complexes.

The structure-distribution relationship studies of a homologous series of anionic 99mTc-2,3-dioximinoalkanes in mice, showed very low specific organ uptakes due to a combination of rapid clearance and excessive blood binding factors as found for the cationic 99mTc-diamine analogues (Salako and Theobald, Nucl. Med. Biol. 17, 437-441; 1990. The dioxime complexes showed a preference for hepatobiliary clearance unlike the diamine complexes which were cleared through the renal tract. The relationship between the amount cleared through the biliary tract and molecular weight of the dioxime complexes is binomial, with the optimum about the C-8 chain homologue. The hepatobiliary clearance model which was discovered for these complexes follows a multiple correlation equation which has a combination of four physico-chemical properties in the order: log P, charge, protein binding and molecular weight. It was observed particularly that the log P and charge have broadly similar magnitudes (to those in the urinary model of the diamine complexes) but reversed signs. The sign on the charge coefficient is negative, indicating that an overall negative charge is required for efficient hepatobiliary extraction and excretion of these Tc-complexes.