Imidazolium trans-imidazoledimethylsulphoxidetetrachlororuthenate ImH[trans-RuCl4(DMSO)Im] (NAMI-A), a ruthenium compound that replaces Na+ with ImH+ in the molecule of Na[trans-RuCl4(DMSO)Im] (NAMI), was studied for the anti-metastasis effects in models of solid metastasizing tumours of the mouse. NAMI-A, given i.p. at 35 mg/kg/day for six consecutive days, a dose equimolar to that of NAMI, to mice bearing Lewis lung carcinoma and MCa mammary carcinoma, markedly reduces lung metastasis weight by 80-90%, with an effect equal or even superior to that of NAMI, depending on the experimental system adopted. Correspondingly, NAMI-A increases the content of connective tissue in the tumour matrix, around blood vessels, and in the tumour capsule, augments the percentage of tumour cells in G2/M phase and reduces the amount of CD45+ cells infiltrating the tumour parenchyma. The effects of the same doses on spleen lymphocytes correspond to an increase of CD8+ subset without any change of the distribution of cells in G0/G1, S and G2/M phases. The study shows that NAMI-A behaves similarly to NAMI on the several parameters examined in comparison experiments and therefore we suggest to credit NAMI-A with all the biological actions already described for NAMI during the last 3 years. The replacement of Na+ with ImH+ therefore, besides the better chemical stability of the molecule, confers to [trans-RuCl4(DMSO)Im]- a closer similarity with a true drug to be used in humans, and suggests this molecule for future studies of preclinical toxicology and phase I and II clinical trials.

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The effects of the new molecule ImH[trans-RuCl4(DMSO)Im] (NAMI-A), administered orally or intraperitoneally to adjuvant-arthritic rats or orally to mice bearing s.c. or i.m. implants of MCa mammary carcinoma, were studied. NAMI-A was not able to modify the progression of chronic inflammation in the complete Freund-adjuvant injected animals. Histology indicated a significant worsening of the inflammatory process, characterised by an increased infiltration of inflammatory cells, as well as by a remarkable deposition of connective tissue fibres around the blood vessels and alveolar walls. NAMI-A had no effect on primary i.m. implanted MCa mammary carcinoma growth and its lung metastasis formation, but significantly interfered with the cell cycle of primary tumor cells following bolus oral administration. On the contrary, NAMI-A caused a significant inhibition of lung metastasis accompanied by a dramatic deposition of connective tissue fibres around the primary tumor mass, when given as medicated food to mice implanted s.c. with MCa tumor. These data indicated that NAMI-A is well absorbed after oral administration although there is no connection between lung concentration and the antimetastatic activity. Conversely, the marked deposition of connective tissues in NAMI-A treated animals is in agreement with the reported effects of the compound on extracellular matrix and tumor blood vessels.

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