Anti-tumor properties of the organometallic complex cis-dimethylbis[sulfinylbis[methane]-S]platinum(II)

The water-soluble organometallic complex cis-[Pt(Me)2(Me2SO)2] (Me = methyl; Me2SO = dimethyl sulfoxide) (cis-dimethyl platinum(II); CDMP) was evaluated for its toxicity on the rat and for its efficacy against two tumors of this animal: the Yoshida ascites sarcoma and the T8 sarcoma of Guérin. The lethal dose for 50% of normal animals was 46.4 mg/kg; the predominant toxic effects were loss of weight, decrease in leukocytes and necrosis of the kidneys after i.v. or of the liver after i.p. administration. Doses of drug varying from 2 to 40 mg/kg were administered once by i.p., i.v., i.m. and intra-tumor (i.t.) route from 1 to 7 days after i.p. injection of 10(6) Yoshida ascites sarcoma cells and s.c. implantation of approximately 300 mg of T8 sarcoma of Guérin. The compound showed anti-tumor activity increasing both the average life span and survival of the rats. A comparison between the therapeutic properties of the title complex with those of cis-[PtCl2(NH3)2] (CDDP) reveals that cis-dimethyl platinum(II) exhibits the same anti-tumor activity associated with 6 times reduced toxicity.