Synthesis of seleno- and thioguanine-platinum(II) complexes and their antitumor activity in mice.

Selenoguanine-, selenoguanosine-, thioguanine-, and thioxanthine-platinum(II) complexes were synthesized, and their antitumor activities were studied against L1210 cells in mice and in an in vitro system. These compounds exhibited antitumor activity of medium strength and showed very low toxicity. The effect of the selenoguanine-platinum(II) complex in mice was retained longer than that of the parent compound, selenoguanine, because the selenoguanine-platinum(II) complex very slowly released selenoguanine into the blood.