Biomedical subjects

N Iznaga Escobar

Publications and source records attributed to N Iznaga Escobar.

5 recordsLinked to original sources

PubMed1998

Pharmacokinetics, biodistribution and dosimetry of 99mTc-labeled anti-human epidermal growth factor receptor humanized monoclonal antibody R3 in rats.

The pharmacokinetics, biodistribution and dosimetry of 99mTc-labeled anti-human epidermal growth factor receptor (anti-hEGF-r) humanized monoclonal antibody (MAb) R3 was investigated following intravenous injection in normal Wistar rats. Serum disappearance curves were best fit by a two-compartment model having a mean distribution half-life (t 1/2alpha) of 0.250 h and a mean elimination (t 1/2beta) of 13.89 h. Among the various organs, a little accumulation of the radiolabeled antibody was found only in kidneys. Biodistribution and dosimetry studies in humans were performed by extrapolation of the animal data to humans. Absorbed dose to normal organs and the remainder of the whole body were estimated using the medical internal radiation dose formula, and dose contributions from radioactivity in transit through the gastrointestinal tract were estimated using a compartment model. Extrapolated values of radiation absorbed dose to normal organs in rads per millicurie administered were whole body, 0.0085; lower large intestine wall, 0.0898; small intestine, 0.0530; upper large intestine wall, 0.0731; and kidneys, 0.0455. The effective dose equivalent predicted was 0.0162 rem/mCi and the effective dose was found to be 0.015 rem/mCi. On the basis of the pharmacokinetics, biodistribution and internal radiation dosimetry information obtained in this study, a diagnostic phase I clinical trial with 99mTc-labeled humanized MAb R3 conjugate in patients should be supported.

Animals↗

PubMed1998

Technetium-99m direct radiolabeling of monoclonal antibody ior egf/r3.

Monoclonal antibodies (MAbs) are being widely used for imaging studies, coupled mainly with 99mTc. The antibody ior egf/r3 is a MAb against human epidermal growth factor receptor (hEGF-r), and we have developed a method for optimum labeling of this MAb with 99mTc. The reduction was performed with 2-mercaptoethanol (2-ME) at a molar ratio of 2000:1 (2-ME:MAb) and methylene diphosphonate as transchelant. The integrity of reduced MAb was checked by mean of native polyacrylamide gel electrophoresis (PAGE) and gel filtration chromatography on Superose 12 (purity >99%). Radio colloids remained lower than 2%, and the labeling efficiency was 98.5%. The number of sulfhydryl groups generated was quantified using Ellman's reagent and was found to be 6.65+/-0.69 per antibody molecule. In vitro stability studies in several challenging conditions (DTPA, human serum albumin and human serum) were performed, and no significant loss in binding percentage was seen. Radio receptor assay was used to test immunoreactivity of the reduced MAb. Both labeled and unlabeled MAbs were able to compete for binding to the hEGF-r with radioiodinated EGF. Biodistribution studies in BALB/c mice are reported.

Animals↗

PubMed1996

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.

Antibodies↗

PubMed1996

A computer program for quantification of SH groups generated after reduction of monoclonal antibodies.

Reduction of disulfide bonds to sulfhydryl (SH) groups for direct radiolabeling of antibodies for immunoscintigraphic studies of colorectal and other cancers continues to be of considerable research interest. We have developed a general strategy and a versatile computer program for the quantification of the number of SH per molecule of antibody (Ab) generated after the treatment of monoclonal antibodies (MAbs) with reducing agents such as 2-mercaptoethanol (2-ME), stannous chloride (SnCl2), dithiothreitol (DTT), dithioerythritol (DTE), ascorbic acid (AA), and the like. The program we describe here performs an unweighted least-squares regression analysis of the cysteine standard curve and interpolates the cysteine concentration of the samples. The number of SH groups per molecule of antibody in the 2-mercaptoethanol and in the other reducing agents was calculated from the cysteine standard curve using Ellman's reagent to develop the yellow color. The linear least-squares method fit the standard data with a high degree of accuracy and with the correlation coefficient r of 0.999. A program has been written for the IBM PC compatible computer utilizing a friendly menu to interact with the users. The package allows the user to change parameters of the assay, to calculate regression coefficients slope, intercept and its standard errors, to perform statistical analysis, together with detailed analysis of variance, and to produce an output of the results in a printed format.

Animals↗

PubMed1996

Micromethod for quantification of SH groups generated after reduction of monoclonal antibodies.

A simple, rapid, and reproducible micromethod for quantification of sulfhydryl (SH) groups generated after reduction of monoclonal antibody (MAb) disulfide bonds with 2-mercaptoethanol (2-ME) is described. The number of SH groups per molecule of antibody in the 2-ME and in the other reducing agents was calculated from the cysteine standard curve using Ellman's reagent to develop the yellow color. Results were plotted as absorbance at 405 nm vs. cysteine concentration (microgram/mL). After subtraction of the background due to Ellman's reagent, a straight-line relationship passing through the origin was obtained. Absorption spectrum of the yellow products was controlled, and no significative differences were found between optical density at 412 nm and 405 nm. Using a small quantity of antibody in the order of 37 micrograms, the lowest detection limit for cysteine quantification was 0.03 microgram. An excellent linear correlation was found between both cysteine concentration and absorbance (r = 0.999), and the mean value of the relative error in the quantification of cysteine from samples was 2.8%. A statistical Student t-test showed an excellent linearity and parallelism between cysteine standard and samples.

Animals↗