Clinical and Immunological Effects of Recombinant Interleukin 2 Given by Repetitive Weekly Cycles to Patients with Cancer

Eleven patients received four consecutive weekly cycles of human recombinant interleukin 2 (IL-2) by continuous infusion for 4 days/week. Two dose levels were tested, 1 and 3 x 10⁶ units/m²/day. Toxicities experienced by most patients included fever, rigors, fatigue, anemia, eosinophilia, and liver function abnormalities. All side effects from treatment reversed and no severe or life-threatening problems occurred. A marked lymphocytosis was seen following the 4 weeks of therapy. Fresh lymphocytes obtained during this lymphocytosis mediated enhanced destruction in vitro of a natural killer cell-resistant tumor cell line (Daudi). The increase in the absolute number of circulating lymphocytes and their enhanced ability to mediate direct lysis of Daudi targets resulted in a >100-fold mean increase in cytotoxic potential by the end of IL-2 treatment. One patient, with renal carcinoma, who was treated at 3 x 10⁶ units/m²/day experienced a sustained measurable response with >50% regression of pulmonary and hepatic metastases. Five patients were retreated with a second course of IL-2, lasting 4 weeks. This therapy was well tolerated in four of these five patients, with similar immunological changes occurring. No further antitumor responses were seen in these patients. Thus, a relatively well tolerated immunotherapy regimen using IL-2 can induce dramatic increases in lymphocyte number and augment their in vitro antitumor reactivity.