Higher antitumor efficacy of daunomycin when linked to dextran: in vivo and in vitro studies.

Daunomycin was coupled to dextrans of various molecular sizes. The binding to the dextran carriers augmented the therapeutic efficacy of the antitumor agent in a murine lymphoma line (YAC). When the treatment with the drug or its conjugates was given concomitantly with the tumor cells at separate sites, the unbound drug was able, at its optimally effective doses, to prevent tumors in 40% of the mice, whereas the drug-dextran was efficient in 80% of the mice. The advantage of the drug-dextran over the free drug was also manifested when the treatment was given 6 days after tumor transplantation. However, a further delay of the treatment resulted in a decrease in the potency of the drug-dextran. Similar behavior was observed when increasing tumor loads were transplanted (10(5)-10(8) cells) and when the treatment was administered immediately. The most favorable effect of the drug-dextran was obtained with 10(7) cells, but against 10(8) cells neither the free drug nor the bound one was effective.