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Introduction: The choice of optimal radionuclides for radioimmunotherapy depends on several factors, especially the radionuclide and antibody. The dosimetric characteristics of a non-internalizing and an internalizing monoclonal antibody (MAb) labeled with beta emitting radionuclides were investigated. Methods: Using Geant4-DNA Monte Carlo simulation, we carry out dosimetric calculations for different subcellular distributions of beta-emitting radionuclides; 131I, 177Lu, 64Cu, 186Re and 153Sm. Results: The dependency of the radial dose profiles on the energy spectra of electrons (beta particles and Auger and internal conversion electrons) and also their relative yield of emission is clear. The highest difference between the radionuclides tested was observed when the activity was localized in the nucleus. There was not considerable difference in the nucleus dose when radionuclides were localized in cytoplasm and over the cell membrane. Conclusion: There is a very significant increase in the dose deposited to the nucleus if 153Sm localized at the nucleus. Although subcellular localization of activity isn't a critical factor for beta emitting radionuclides, but the use of internalizing MAbs leads to an increase in nucleus dose and to the killing of single cells in addition to the tumors. [ABSTRACT FROM AUTHOR]

Introduction: This report describes the synthesis of 2-Amino-2-deoxy(S-benzoylthioacetyl)-D-glucose (S-Bz-TA-DG), radiolabeled with [99mTc(CO)3(OH2)3]+ complex with a procedure including deprotection of the benzoyl group, characterization by HPLC using a Cl 8 reverse phase colunm and preliminary biodistribution study in normal mice. Methods: [99mTc(cO)3(H2O)3]+ complex was used to label TA-DO with 99mTc This complex was prepared using up to 46 mCi of Na99mTcO4 in 1 mL saline. The radiochemical purity (>95%) was determined by TLC in normal saline solution as the mobile phase. Radio-HPLC analysis of [99mTc]-(TA-DG) at pH=9.5-10, revealed that labeling with 99mTc resulted in the formation of three radiochemical species (Na99mTcO4 with tR=5.7 min, [99mTc(CO)3(H2O)3]+ complex with tR=27.5 min and [99mTc]-(TA-DG) [yield >85%] with tR=8.2 min) with different HPLC-profiles. Results:. The biodistribution of the [99mTc]-(TA-DG) complex was studied in normal mice (body mass 25-35 g) at 30 min and 1 h post-injection, according to a published procedure. This complex showed negligible brain uptake (0.13%±0.03 ID) at 30 min post-injection, an efficient clearance from the blood, a rapid excretion to the urine and a low retention in the liver and kidneys. Conclusion: Nonfunctionalized carbohydrate compounds such as glucose are generally weak ligands for chelating with 99mTc. Therefore, functionalization with an external chelating group or the insertion of some functional groups is essential to obtain strong metal-binding compounds. On the basis of our results, it seems that [99mTc]-(TA-DG) has not most of the favorable properties as an imaging agent for brain tumors. [ABSTRACT FROM AUTHOR]