Does the antitumoral activity of platinum (IV) derivatives result from their in vivo reduction?

The antitumoral activity of some octahedral platinum(IV) and square-planar platinum(II) derivatives against Yoshida ascites tumor in the rat is reported. It is shown that only those octahedral platinum(IV) complexes which give active reduction products are active. These results support the hypothesis that the antitumor activity of octahedral complexes involves activation by in vivo reduction. Anticancer drugs functioning by this mechanism may be preferentially toxic to or may localize in hypoxic areas of tumors.