Activity of titanocene dihalides against a human colon carcinoma heterotransplanted to athymic mice.

The antitumor activity of cis-diamminedichloroplatinum (II) and of two metallocene derivatives, titanocene dichloride (C5H5)2TiCl2 and titanocene dibromide (C5H5)2TiBr2, was investigated against a human colon adenocarcinoma heterotransplanted to athymic mice. The substances were administered at various doses on a Q2DX5 or a Q3DX5 schedule. Whereas cis-diamminedichloroplatinum (II) induced an only marginal tumor-inhibiting effect, both titanocenes markedly suppressed tumor development (T/C values: 23-40%) and caused stagnation and relative decrease of tumor growth, when they were applied in subtoxic doses far below the LD10 level. The results are remarkable with respect to the general insensitivity of human colorectal carcinomas to cytostatic agents.