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.

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.

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.