Antitumor metallocenes: new developments and toxicologic features.

Recent results concerning new antitumor metallocene derivatives have shown that not only numerous titanocene dihalides and bis(pseudohalides) exhibit antiproliferative activity, but that also some titanocene complexes (C5H5)2TiX2 containing carboxylates or hydrochlorinated aminothiophenolates as ligands X, are characterized by pronounced antineoplastic efficacy. Whereas antitumor activity of metallocene derivatives has originally been established against Ehrlich ascites tumor, recent experimental results demonstrate antiproliferative activity also against B16 melanoma, sarcoma 180, as well as against human tumors heterotransplanted to athymic mice. Studies upon the organ toxicity of titanocene dichloride indicate a pattern of toxicity markedly differing from that observed after treatment with cytostatic platinum compounds.