Design and evaluation of “3 + 1” mixed ligand oxorhenium and oxotechnetium complexes bearing a nitroaromatic group with potential application in nuclear medicine oncology

188Re(V) Nitrido Radiopharmaceuticals for Radionuclide Therapy

The favorable nuclear properties of rhenium-188 for therapeutic application are described, together with new methods for the preparation of high yield and stable ¹⁸⁸Re radiopharmaceuticals characterized by the presence of the nitride rhenium core in their final chemical structure. ¹⁸⁸Re is readily available from an ¹⁸⁸W/¹⁸⁸Re generator system and a parallelism between the general synthetic procedures applied for the preparation of nitride technetium-99m and rhenium-188 theranostics radiopharmaceuticals is reported. Although some differences between the chemical characteristics of the two metallic nitrido fragments are highlighted, it is apparent that the same general procedures developed for the labelling of biologically active molecules with technetium-99m can be applied to rhenium-188 with minor modification. The availability of these chemical strategies, that allow the obtainment, in very high yield and in physiological condition, of ¹⁸⁸Re radiopharmaceuticals, gives a new attractive prospective to employ this radionuclide for therapeutic applications.

⁹⁹mTc/Re complexes bearing bisnitroimidazole or mononitroimidazole as potential bioreductive markers for tumor: synthesis, physicochemical characterization and biological evaluation

Four monoamine-monoamide dithiol (MAMA) ligands containing two or one nitroimidazole moieties were synthesized and labeled with (99m)Tc (labeling yield > 95%). The proposed structures of (99m)Tc-complexes are identified by comparison with analogous Re-MAMA complexes. (99m)Tc-MAMA complexes show better physicochemical characters than (99m)TcO-(PnAO-1-(2-nitroimidazole)). Reduction potentials of nitro groups of the rhenium complexes are within the range for bioreductive compounds. As expected, biodistribution studies demonstrate that the 2-nitroimidazole complex shows better tumor-to-tissue ratios than 4-nitroimidazole analog for mononitroimidazole complexes, but not for MAMA-bisnitroimidazoles due to higher lipophilicity. Both the bisnitroimidazole compounds show rapider excretion, lower background activity in liver and higher tumor-to-tissue ratios than the mononitroimidazoles. Better biodistribution characteristic makes both the MAMA-bisnitroimidazole complexes, especially (99m)Tc-15, be potential tumor hypoxia marker.

Synthetic chalcones, flavanones, and flavones as antitumoral agents: biological evaluation and structure-activity relationships

A series of synthetic chalcones, flavanones, and flavones has been synthesized and evaluated for antitumor activity against the human kidney carcinoma cells TK-10, human mammary adenocarcinoma cells MCF-7 (estrogen receptor-positive), and human colon adenocarcinoma cells HT-29. The most active series is the chalcone ones with the best results against TK-10 and HT-29 cells. Fourteen out of 53 analyzed compounds resulted very active against at least two of the studied tumoral cells. Alkaline single cell gel electrophoresis, comet assay, was performed as a study of the chromosomal aberrations promoted by the compounds on normal cells. Four active and two inactive chalcones were studied in the comet assay against normal human kidney cells (HK-2). A structure-activity relationship analysis of these compounds was performed and for 4- and 3,4-disubstituted derivatives a quantitative correlation was obtained in the case of anti-HT-29 activity.