PRELIMINARY STUDIES OF TECHNETIUM-99m-LABELED ANTIMYOSIN MONOCLONAL ANTIBODY: DEVELOPMENT OF RADIOPHARMACEUTICAL FOR CARDIAC EVALUATION

In the acute myocardium infarction, the myocytes cell membrane loses its integrity, allowing the influx of extracellular macromolecules such as circulating antibody into the damaged cell. Specific antibodies to cardiac myosin can therefore bind to the acutely necrotic myocyte, allowing the noninvasive localization and dimension of myocardial infarction. Because of its favorable physical characteristics, low cost, and ready availability, technetium-99m (Tc) is the radionuclide of choice for scintigraphy. The purpose of this work was to study the labeling of the antimyosin monoclonal antibody with Tc for development of a radiopharmaceutical with high sensitivity and specificity used in the diagnostic of the myocardial infarction. The intact monoclonal antibody (IgG1) was reduced by treatment with dithiothreitol (DTT) with the consequent generation of free thiol groups (SH), responsible for the labeling of the antibody with Tc. The radiochemical yield was determined using Sephadex G-25 column (PD-10). The percentage of Tc-antibody was 90,06% and after purification procedure the radiochemical yield was > 98%. The biodistribution studies showed low uptake in the stomach and thyroid at different times (1, 4 e 24 hours) representing a small amount of unbounded Tc and a good stability of the purified Tc-antibody. The uptake in the normal heart was relatively low as expected. Based on these results, we concluded that the direct labeling procedure applied to the antimyosin monoclonal antibody allowed the easy preparation of the radiopharmaceutical with good stability to be used in the noninvasive diagnostic of the myocardial infarction.