(99m)Tc-labeled murine ior C5 monoclonal antibody in colorectal carcinoma patients: pharmacokinetics, biodistribution, absorbed radiation doses to normal organs and tissues and tumor localization.

Monoclonal Antibody (mAb) ior C5 is a murine IgG(1) that recognizes the tumor associated antigen (TAA) ior C2, a cell surface O-linked glycoprotein carbohydrate chain not present in most normal tissues and homogeneously expressed in the cytoplasm of normal colon epithelium and heterogeneously expressed in more than 83% of primary colorectal carcinomas. This study was designed to investigate the pharmacokinetics, biodistribution and the absorbed radiation doses of (99m)Tc-labeled mAb ior C5 antibody in colorectal tumor patients. Ten patients were administered 3 mg of anti-O-linked glycoprotein carbohydrate chain TAA ior C2 murine monoclonal antibody ior C5 radiolabeled with (99m)Tc activity of 1435.0 +/- 123 MBq by intravenous (i.v.) bolus infusion. Blood and urine samples were collected from 4 out of 10 patients at timed intervals from 10 min and up to 24 h after injection of the (99m)Tc-labeled mAb ior C5 for pharmacokinetic studies. Whole body images were taken in 5 out of 10 patients for quantitative normal organ biodistribution and dosimetry studies and planar anterior and posterior and SPECT images were taken in 5 out of 10 patients for tumor localization. Mean absorbed doses were estimated using the methods developed by the Medical Internal Radiation Dose (MIRD) committee. The effective dose equivalent (EDE) and effective dose (ED) were calculated as prescribed in International Commission on Radiological Protection (ICRP) publications 30 and 60. Plasma disappearance curves of (99m)Tc-labeled murine antibody ior C5 were best fit by a two-compartment model in all patients with (t(1/2alpha)) of 4.32 +/- 2.18 h and (t(1/2beta) of 32.6 +/- 3.82 h. Among the main target organs, accumulation of the radiolabeled antibody was found in liver (9.38 +/- 0.80%), heart (8.92 +/- 0.94%) and spleen (1.37 +/- 0.30%) at 5 min post-administration. These values were reduced at 24 h to (5.91 +/- 0.73%) and (0.62 +/- 0.22%), respectively, for the heart and spleen and increased to (9.78 +/- 1.99%) for liver. Estimates of radiation absorbed dose to normal organs in rad/mCi administered were: whole body, 0.0181 +/- 0.0017; heart wall, 0.0768 +/- 0.0090; kidneys, 0.0530 +/- 0.0260; liver, 0.0565 +/- 0.0109 and spleen, 0.0540 +/- 0.0128. The effective dose equivalent and effective dose estimates for adults were 0.0314 +/- 0.0031 and 0.0249 +/- 0.0027 rem/mCi administered. This feasibility study indicates that the O-linked glycoprotein carbohydrate chain TAA ior C2 is expressed in primary and metastatic colorectal carcinomas and shows very limited expression in normal adult tissues. The very good pattern of biodistribution of (99m)Tc-labeled mAb ior C5 in patients will allow imaging of colorectal carcinoma lesions.

Biodistribution of 99mTc-labeled anti-human epidermal growth factor receptor (EGF-R) humanized monoclonal antibody h-R3 in a xenograft model of human lung adenocarcinoma.

The anti-human epidermal growth factor receptor (EGF-R) humanized monoclonal antibody (MAb) h-R3 is an (IgG1), which binds to an extracellular domain of EGF-R. It was used to evaluate the biodistribution on nude mice xenografted with H-125 human lung adenocarcinoma cell line. Results were compared with its murine version of the MAb ior-egf/r3. Twenty-one athymic female 4NMRI nu/nu mice were injected intraperitoneally with 10 microg/100 muCi of 99mTc-labeled MAbs. Immunoreactivity of 99mTc-labeled MAbs were measured by enzyme-linked immunosorbent assay (ELISA) on H-125 cell line and the immunoreactive fractions was determined by the Lindmo method. Among all organs, significant accumulation was found in serum (27.05 +/- 2.08 %ID/g) and tumor (3.903 +/- 0.89 %ID/g) at 4 h after injection. These values decreased to 5.03 +/- 0.50 %ID/g and 2.19 +/- 0.56 %ID/g for serum and tumor, respectively. The immunoreactive fraction was found to be 0.70, with a correlation coefficient r = 0.9984. With the good biodistribution and tumor uptake of the 99mTc-labeled humanized antibody h-R3, a phase I diagnostic clinical trial of tumor with epithelial origin should be pursued.

Technetium-99m-antiepidermal growth factor-receptor antibody in patients with tumors of epithelial origin: part II. Pharmacokinetics and clearances.

UNLABELLED: Radiolabeled antitumor antibodies hold promise for diagnostic imaging and therapy in oncology. The purpose of this study was to investigate the pharmacokinetics, clearances and possible differences of two dosage administrations of the 99mTc-labeled antiepidermal growth factor (EGF)-receptor antibody and to predict the best dose and schedule for future clinical evaluations of this radiopharmaceutical. METHODS: Nine patients (4 women, 5 men; mean age 46.4 +/- 14.0 yr) were administered 1-3 mg 99mTc-labeled anti-EGF-receptor antibody (a murine IgG2a isotype) by intravenous bolus infusion. After administration, blood samples were collected from 7 patients from an antecubital vein opposite to the injection side at intervals from 2 min to 24 hr after injection, and plasma samples were obtained for pharmacokinetic analysis. Appropriate plasma samples were examined for isotope clearance (i.e., microCi/ml at various intervals) and 99mTc complexation to plasma proteins by fast protein liquid chromatography (FPLC) analysis. Urine was collected from each patient at 3 hr intervals up to 24 hr after monoclonal antibody administration to monitor 99mTc clearance. Plasma time-activity curves were fitted to a two-compartment model using nonlinear least-squares regression analysis by the method of flexible polyhedrals. RESULTS: Plasma disappearance curves of 99mTc-labeled anti-EGF-receptor antibody were best fit by biexponential equation with a distribution half-life (t(1/2alpha)) of 0.137 +/- 0.076 hr (n = 7) and elimination half-life (t(1/2beta)) of 20.3 +/- 8.0 hr. Analysis of urine showed that activity clearance by this route amounted to 4.9% +/- 0.6% of the injected dose in 24 hr, and FPLC analysis showed no evidence of decomposition, only 6%-7% of 99mTc was in a low molecular weight species. CONCLUSION: Plasma pharmacokinetics and urine clearance indicate comparability in both doses. The pharmacokinetic properties of the 99mTc-labeled anti-EGF-receptor antibody were found to be dose-independent. These findings provide an initial characterization of the radiopharmaceutical disposition in patients and may be used as the basis for calculating a better estimate of biodistribution and dosimetry for patients who will receive 188Re-labeled anti-EGF-receptor antibody (MAb ior egf/r3) injection for radioimmunotherapy and warrants further controlled clinical trials to define the efficacy of the radiopharmaceutical.

Multianalytical system (MAS): software for enzyme-linked immunosorbent assay (ELISA) data processing with applications to screening and diagnostic tests.

A microcomputer software package for determining the concentration of either the antibody or antigen from ELISA data for IBM PC compatible is presented. In the program optical densities (OD) and fluorescence obtained from 96-well ELISA plate can be input either directly, by interfacing with different brands of microplate reader such as Multiskan II Plus and Organon Teknika to the computer or manually. This software utilizes some mathematical and statistical models to fit the standard curve of each assay and interpolate analyte concentration using data from OD or fluorescence measurements. Cubic spline (Guardabasso et al., 1988), bezier and polynomial (Rodbard, 1979; Baud et al., 1991) interpolation formulas can be used to fit the data over the entire range for estimating the antibody or antigen concentration of the unknown samples whose OD or fluorescence is beyond the entire range. This software package, based on the concentration values of the analyte determined in different fluids (Núnez et al., 1994; Morales et al., 1994) and with some rules and algorithms, is used to calculate the parameters of screening and diagnostic tests such as sensitivity, specificity and predictive values (Coughlin et al., 1992). With the construction of the Receiver Operating Characteristic (ROC) curve it is possible to analyse different values of the sensitivity and specificity of the screening and diagnostic tests. A comparative statistical test for two populations that are non-normally distributed using a non-parametric Mann-Whitney test is provided. This software is an expandable tool designed for general use in clinical and experimental applications, including diagnostic and screening tests.