Isoprinosine increases the antitumor action of interferon.

The association of relatively low doses of interferon with an immunostimulant, isoprinosine, enhanced the antitumor effect of interferon. Each mouse was inoculated with 10(6) Crocker Tumor 180/TG cells. The best results were obtained when both interferon and isoprinosine were injected three times a week for 1 month. Under these conditions, the mean survival time increased from 26 days in the controls to 45 days in the interferon-treated group to 64 days when both agents were used. Isoprinosine alone had no effect. The final survival rate increased from 1 mouse out of 50 mice in the control group to 10 mice out of 50 in the interferon-treated groups and to 25 mice out of 50 with the combined treatment.