Clinical and immunomodulatory effects of repetitive 2-day cycles of high-dose continuous infusion IL-2.

High-dose interleukin-2 (IL-2) treatment has demonstrated promising antitumour activity in renal cell carcinoma (RCC) and malignant melanoma (MM) and has been shown to induce broad immunological effects. The optimal IL-2 dose and schedule, however, still remain to be defined. We studied a treatment protocol consisting of five repetitive cycles of high-dose recombinant (rh) IL-2 (24 x 10(6) U/m2/day) administered weekly on two consecutive days by continuous intravenous infusion. 17/19 were RCC patients, 2 of whom responded with a complete remission (CR) and 3 with a partial response (PR) (CR + PR: 29%; median response duration of 11.5+ months (range: 3-14 months)). IL-2 induced a pronounced increase of lymphocytes and pro-inflammatory cytokines IL-8, IL-5, gamma-IFN, TNF- alpha and TNF-beta (p < 0.05) that peaked in cycle 3. With subsequent therapy, serum levels of these cytokines, NK, T cells and eosinophils decreased, whereas serum IL-10 levels progressively increased with maximum levels achieved after the fifth week of treatment, suggesting that it may be involved in dampening the inflammatory response induced by IL-2. Absolute numbers of activated T cells and NK cells remained elevated as compared to baseline for at least 4 weeks after treatment cessation. Based on these observations, future scheduling of IL-2 will be done at 3 weekly 2-day cycles separated by a week 4 treatment-free interval in order to increase further the 29% objective response rate achieved in this study.