⁹⁹mTc-N4amG: synthesis biodistribution and imaging in breast tumor-bearing rodents

Chelation-Tamoxifen Conjugates for Imaging of Estrogen Receptors

Background: The differential diagnosis of estrogen receptor-positive (ER+) pathway-activated systems by using a labeled antiestrogen helps to select the patients for optimal response to endocrine therapy and to discontinue the treatment when resistance occurs. The authors' purpose was to synthesize chelator-tamoxifen conjugates for imaging ER (+) diseases. Materials and Methods: A hydroxypropyl linker was incorporated between either cyclam or cyclam diacetic acid and tamoxifen analog to produce SC-05-L-1 (Z-1-(1,4,8,11-tetraazacyclotetradecan-1-yl)-3-((5-(4-(2-(diethylamino)ethoxy) phenyl) -4,5-diphenylpent-4-en-1-yl)oxy)propan-2-ol) and SC-05-N-1 (Z-2,2'-(4-(3-((5-(4-(2-(diethylamino)ethoxy)phenyl)-4,5-diphenylpent-4-en-1-yl)oxy)-2-hydroxy-propyl) -1,4,8,11-tetraazacyclotetradecane-1,8-diyl)diacetic acid), respectively. In vitro cell uptake and cell/media ratios of ^99mTc-SC-05-L-1 and ^99mTc- SC-05-N-1 in ER (+) ovarian cancer cells (TOV-112D and OVCAR3) were performed. To ascertain the specificity of cell uptake, the cell uptake was blocked with estrone. In vivo ^99mTc-SC-05-L-1 or ^99mTc-SC-05-N-1 single-photon emission computed tomography/computed tomography was conducted in tumor-bearing rodents and compared to ¹⁸F-fluoro-2-deoxy-d-glucose (¹⁸F-FDG) positron emission tomography/magnetic resonance imaging (a reference technology). Results: The radiochemical purities of ^99mTc-SC-05-L-1 and ^99mTc-SC-05-N-1 were greater than 99% (n = 10). ^99mTc-SC-05-L-1 had higher cell/media ratios than ^99mTc-SC-05-N-1 in OVCAR-3 ER (+) cells. The cell uptake of ^99mTc-SC-05-L-1 was blocked 80% by estrone indicating an ER-mediated process occurred. ^99mTc-SC-05-N-1 was further selected for in vivo imaging studies due to higher maximum tolerated dose and superior water solubility than ^99mTc-SC-05-L-1. ^99mTc-SC-05-N-1 showed higher tumor uptake and tumor/muscle count density ratios than ¹⁸F-FDG in tumor-bearing rodents. Conclusion: ^99mTc-SC-05-N-1 showed better differential diagnosis of ovarian tumors than ¹⁸F-FDG, indicating great promising in chelator-tamoxifen conjugate for ER pathway-directed systems imaging.

Synthesis, quality control, and bio-evaluation of 99m Tc-cyclophosphamide

Cancer is found to be the leading cause of death worldwide characterized by uncontrolled cell division. Nuclear medicines imaging using radiopharmaceuticals have pronounced potential for the diagnosis and treatment of cancers. Cyclophosphamide (CPH) is an antineoplastic drug which targets selectively cancer cells. In the present work, labeling of CPH with Tc-99m is performed for diagnostic purpose, which gave labeling yield as high as 99% using 20 μg SnCl₂ ·2H₂ O, 200 μg of ligand at pH 7 for 10 min reaction time at room temperature. The characterization of the prepared complex was performed using ITLC, electrophoresis, and HPLC. In vitro stability was analyzed in the presence of human serum at 37°C which has maximum value of 94 ± 0.5. The biodistribution studies of ^99m Tc-CPH were performed in normal and tumor bearing Swiss Webster mice. The high accumulation of ^99m Tc-CPH was observed in liver and tumours respectively at 4 hr after injection. Biodistribution results revealed that ^99m Tc-CPH may be a potential tumour diagnostic agent simultaneously with chemotherapy.