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A series of 18 ruthenium(III) complexes, structurally related to the selective antimetastatic drug Na[trans-RuCl4(DMSO)Im], and characterized by the presence of sulfoxide and nitrogen-donor ligands were tested on TLX5 lymphoma and some of them on MCa mammary carcinoma to evaluate the dependence of the degree of cytotoxicity and of antimetastatic activity on the chemical properties. In vitro cytotoxicity is present only at high concentrations (> 10(-4) M), depends upon lipophilicity and is markedly affected by the presence of 5% serum or plasma samples in the culture medium. The comparison of the effects on in vitro cytotoxicity with in vivo antitumor and antimetastatic action points out that these compounds reduce metastasis formation by a mechanism unrelated to a direct tumor cell cytotoxicity. If on one hand Na[trans-RuCl4(TMSO)Iq], the compound that shows the most potent in vitro cytotoxic effects, is the least effective against metastases, on the other Na[trans-RuCl4(DMSO)Im], the compound that better reduces metastasis formation, is rather devoid of cytotoxic effects on tumor cells kept in vitro. In particular, Na[trans-RuCl4(DMSO)Im] seems to distinguish between artificially induced metastases and spontaneous metastases and reduces only the former by a cytotoxic mechanism. Out of all the tested compounds, with the exception of Na[trans-RuCl4(DMSO)Ox], Na[trans-RuCl4(DMSO)Im] is confirmed to be the most selective antimetastatic agent of the group.

An asymmetric rutheniumIII complex containing dimethylsulphoxide ligands, namely mer-trichlorobisdimethylsulphoxideaminorutheniumIII (BBR2382), has been tested in mice bearing solid metastasizing tumors. The effects of i.p. treatment with BBR2382 on primary tumor growth and on the survival time of hosts carrying s.c. or i.m. tumors have been compared to those of cisplatin and of a rutheniumIII complex with imidazole ligands, ImH[RuIm2Cl4], described as a potent antitumor agent in a number of experimental models of murine neoplasms. In mice bearing Lewis lung carcinoma, BBR2382 results as effective as cisplatin on s.c. primary tumor growth and more potent than cisplatin on the prolongation of host survival time. The combined treatment of mice bearing Lewis lung carcinoma with cisplatin and BBR2382 causes a reduction of s.c. tumors higher than that caused by each single agent; the effects on host survival time are similar to those caused by BBR2382 alone but significantly superior to those caused by cisplatin alone. In CBA mice bearing MCa mammary carcinoma, the effects of BBR2382 are slightly lower than those of cisplatin on i.m. tumors but are equivalent on host survival time. The comparison of the antineoplastic action of BBR2382 with that of ImH[RuIm2Cl4] is always in favor of the former, independently of the parameter chosen and of the tumor system used. Qualitatively, the antitumor action of BBR2382 seems different from that of cisplatin and of ImH[RuIm2Cl4]; it is supposed that this agent, like other "rutheniumIII dimethylsulphoxide" complexes, could have a particular efficacy for tumors localized in the lungs.

The antitumour effects of some ruthenium (II) complexes were tested in mice bearing the solid metastasizing tumour, Lewis lung carcinoma. The toxicity of trans-RuCl2 (DMSO)4 is 10-fold higher than that of its cis-isomer. Qualitatively the antitumour activity of these two complexes is comparable, although trans-isomer is more potent. Both exhibit only marginal effects on primary tumour growth while significantly lowering lung metastasis formation. The effects of trans-RuCl2 (DMSO)4 on primary tumour depend on the inoculum size, being more pronounced with low tumour inocula; significant antitumour effects can be achieved also by replacing Cl with I in the molecule. trans-RuCl2(DMSO)4 markedly reduces the number of lung metastases and particularly their volume; the reduction is comparable to that obtained with equitoxic treatments of cisplatin. Treatment with trans-RuCl2(DMSO)4 for 10 consecutive days, after surgical amputation of primary tumour, significantly prolongs the survival time of the treated mice; cisplatin, at equitoxic doses, is less effective. These data show that dimethylsulphoxide ruthenium(II) complexes possess a significant antitumour and antimetastatic activity in the Lewis lung system, also exhibiting an interesting therapeutic potential when combined with surgical amputation of the primary tumour.

A series of alicyclic amine complexes of the cis-Pt(am)2Cl2 type, showed specific antitumour activity against various animal tumours. We have tested these compounds in a number of bacterial systems indicative of their interaction with bacterial DNA.

The effects of square planar rhodium, [RhacacCOD]o and iridium, [IracacCOD]o complexes and of octahedral ruthenium, [cis-RuCl2 (DMSO)4]o complex have been examined in comparison with cis-dichlorodiammino platinum(II) (cis-PDD). The toxicity in BDF1 mice varies widely and decreasing LD50-values, ranging from 0.94 mg/kg to 1000 mg/kg, have been obtained for cis-PDD, [RhacacCOD]o, [IracacCOD]o and [cis-RuCl2(DMSO)4]o, respectively. All the tested complexes similarly inhibit the growth of subcutaneous Lewis lung carcinoma and the development of spontaneous as well as of artificial metastases, with the exception of [IracacCOD]o which is inactive on metastases. The antitumor activity of [RhacacCOD]o and [cis-RuCl2(DMSO)4]o appears interesting, since it is of the same magnitude as that of cis-PDD, considering also that they were found to be only marginally nephrotoxic.

Several rhodium(I) and iridium(I) complexes displayed different degrees of antitumour activity when tested in mice bearing Ehrlich ascites carcinoma. Rhodium (I) and iridium (I) acetylacetonate derivatives caused a high percentage of cures. The rhodium (I) dimers were particularly interesting, since (bis(cycloocta-1,5-diene)micromicron' dichlorodirhodium(I) [RhCODCl]2) was highly effective, whereas its analogues, bis(bicyclo[2,2,1]hepta-2,5-diene)micromicron'-dichlorodirhodium(I) [RhNBDCl]2) and bis(1,5-hexadiene)micromicron' dichlorodirhodium(I) [RhEDCl]2) were virtually inactive. The absence of significant inhibition of DNA, RNA and protein syntheses in tumour cells found for [RhCODCl]2 at therapeutically active dosages, indicates that this substance has a different mechanism of action from that of cis-dichlorodiammine Pt(II) (cis-PDD). The amount of rhodium found in tumour cells after administration of active [RhCODCl]2 was higher than that for [RhEDCl]2, while the rhodium concentration in the ascitic fluid was much higher for [RhEDCl]2. A mechanism based on the chemical properties of the complexes is tentatively proposed for explaining these findings and selective toxicity for tumour cells.