REEVALUATION OF THE SUPERIORITY OF POLYETHYLENE GLYCOL-MODIFIED INTERLEUKIN-2 OVER REGULAR RECOMBINANT INTERLEUKIN-2

Other groups have reported a superior antitumor efficacy of polyethyle ne glycol-modified interleukin-2 (PEG-IL-2) compared with regular reco mbinant interleukin-2 (rIL-2). However, detailed comparison of the ant itumor efficacies of locally applied PEG-IL-2 and rIL-2 in the well-es tablished DBA/2-SL2 model shows a higher antitumor efficacy of PEG-IL- 2 only at doses < 800 mu g IL-2 protein/kg body weight, At doses > 800 mu g IL-2 protein/kg body weight, rIL-2 has better therapeutic effica cy. The superiority of rIL-2 at doses > 800 mu g IL-2 protein/kg body weight is a result of the toxicity of PEG-IL-2 at these doses. With ei ther IL-2 preparation, cure rates of approximately 90% can be obtained at nontoxic doses. We conclude that PEG-LL-2 does not have superior a ntitumor efficacy to rIL-2, The main advantage of PEG-IL-2 is that for optimal therapeutic efficacy a daily injection schedule is not requir ed as seems to be the case for rIL-2.