Recombinant interleukin-2.

Recombinant interleukin (IL)-2 is a newly approved immunoregulatory protein produced by lymphocytes that exhibits a wide range of immunologic effects. It is a true biologic response modifier in that is has no known direct antitumor activity, but mediates its cytotoxicity through activation of effector cells including T cells, natural killer cells, and lymphokine-activated killer cells. Recombinant IL-2 has demonstrated activity in patients with renal cell carcinoma and melanoma, with objective response rates of approximately 15-20%. The median duration of response in renal cell carcinoma is 23 months. Toxicity experienced with high-dose IL-2 can be significant. The most common dose-limiting toxicities are hypertension, weight gain, oliguria, respiratory insufficiency, and neurotoxicity. These effects are generally manageable and reversible on discontinuation of therapy. Administration of low-dose IL-2 has emerged as a means of substantially reducing toxicity. At least in renal cell carcinoma, it appears that the response rate to low-dose IL-2 is comparable to that with higher dosages.