Rhodium(I) square planar complexes [RhCl(COD)(NH3)], [RhCl(COD)(piper-idine)] and [Rh(acac)(COD)] (COD = 1,5-cyclooctadiene) are efficient agents against leukemia L1210, Ehrlich ascites carcinoma, sarcoma 180 and Lewis lung carcinoma, and inhibit the development of metastases. Acetylacetonato complexes are significantly more active than complexes containing piperidine, 2,2'-bipyridine and 1,10-phenanthroline. The anti-tumor activity of these complexes is interesting because it is comparable with that of cisplatin. Furthermore, they are only marginally nephrotoxic.8 10 The 1,5-cyclooctadiene complexes show better anti-tumor properties than coordination complexes with norbor-nadiene (NBD), and complexes with 1,5-hexadiene are not active anti-tumor agents. The cationic complexes [Rh(COD)(N—N—R)]Cl, where N—N—R = 2-pyridinalmethylimine, 2-pyridinalethylimine and 2-pyridinaliso-propylimine, exhibit activity against Lewis lung carcinoma, P388 lymphocytic leukemia and a mammary carcinoma (MC) and on lung metastatic tumor.11 13 The anti-neoplastic properties of these complexes do not seem related to a cytotoxic action. It is more probable that modifications occurring at the primary tumor level, most likely different from lethal effects directed to tumor cells, lead to the reduction of spontaneous lung metastasis in the treated animals. Complexes possessing nitrogen leaving-groups show similarly pronounced effects on the primary tumor and on lung metastases, while the dimeric rhodium(I) complexes [Rh2Cl2(COD)2], [Rh2Cl2(NBD)2] and [Rh2Cl2(CH2 = CHCH2CH2CH = CH2)2] display negligible effects on subcutaneous tumor growth, showing instead a remarkable anti-metastatic effect.8 14
The square-planar rhodium(I) carbonyl complexes [RhX(CO)2], where X = sulfonamide derivatives, were prepared, characterized and assayed as cytotoxic and anti-tumor agents in vitro against KB oral carcinoma and in vivo against P388, Ehrlich ascites and advanced B16 melanoma. Assays against three Trypanosoma strains were also performed. The coordination complex [Rh(sulfamethoxydiazine)(CO)2] appeared to be active in all mentioned biological systems. This examined complex did not show nephrotoxicity. Relationships between biological activity and ^-electronic charge localization on the nitrogen atom of the amidic group were also discussed.15 Dithiocarbamate and xanthate rhodium(I) carbonyl complexes - [Rh(S2CNR2)(CO)2] and [Rh(S2COR)(CO)2] - were also synthesized and assayed as cytostatic and antitumor agents in vitro against KB cells and in vivo against P388 leukemia, Ehrlich ascites carcinoma, Sarcoma 180 ascites and ADJ/PC6A solid tumor as well as against five Trypanosoma strains. The dicarbonyl(diphenyldithiocarbamato)-
rhodium(I) complex [Rh(S2CNPh2)(CO)2] was active in all aforenamed biological systems without showing evident nephrotoxicity.16 The NBD xanthate complexes [Rh(S2COR)(NBD)] show activity against Ehrlich and Landschutz ascitic tumors.17,18
The cationic complexes [Rh(NBD)(N—N)]ClO4, where N—N = 3,3'-dimethylene-2,2'-1,8-naphthyridine and 3,3'-trimethylene-2,2'-1,8-naphthyridine, were assayed against ascitic tumors and primary solid tumors in the form of pure complexes and coordination complexes adsorbed on polymers (polyethylene glycols). These complexes appear to be promising drugs because of their solubility in polymer dissolved in water, which make them easier to use in comparison with neutral complexes. These complexes are similar to cisplatin in reducing tumor growth and in increasing the survival lifespan of mice.19
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