Amplification of the antitumor activity of phleomycins in rats and mice by heterocyclic analogues of purines.

Significant and often substantial enhancement of the antitumor properties of several individual phleomycins , by co- administration via intraperitoneal injection of a number of purine analogues, is demonstrated in rats and mice having three diverse tumors. It is evident that the dose levels of both the phleomycin and the amplifier are very significant and that optimal levels vary widely with the actual agents used. Constant serum levels of amplifier can be maintained for several days by administration via silastic-pellet implantation rather than injection, and this route of administration is an effective alternative for amplifiers of low solubility.