Purpose:
The first-in-human clinical trial with human bolus i.v. infusion IL-15 (rhIL-15) was limited by treatment-associated toxicity. Here, we report toxicity, immunomodulation, and clinical activity of rhIL-15 administered as a 10-day continuous intravenous infusion (CIV) to patients with cancers in a phase I trial.
Patients and Methods:
Patients received treatment for 10 days with CIV rhIL-15 in doses of 0.125, 0.25, 0.5, 1, 2, or 4 mcg/kg/day. Correlative laboratory tests included IL-15 pharmacokinetic (PK) analyses, and assessment of changes in lymphocyte subset numbers.
Results:
Twenty-seven patients were treated with rhIL-15; 2 mcg/kg/day was identified as the maximum tolerated dose (MTD). There were 8 serious adverse events including 2 bleeding events, papilledema, uveitis, pneumonitis, duodenal erosions and 2 deaths (one due to likely drug-related gastrointestinal ischemia). Evidence of antitumor effects were observed in several patients, but stable disease was the best response noted. Patients in 2 mcg/kg/day group had a 5.8-fold increase in number of circulating CD8+ T cells, 38-fold increase in total NK cells, and 358-fold increase in CD56bright NK cells. Serum IL-15 concentrations were markedly lower during the last 3 days of infusion.
Conclusion:
This phase I trial identified the MTD for CIV rhIL-15 and defined a treatment regimen that produced significant expansions of CD8+ T and NK effector cells in circulation and tumor deposits. This regimen has identified several biological features, including dramatic increases in numbers of NK cells, supporting trials of IL-15 with anticancer monoclonal antibodies to increase antibody-dependent cell-mediated cytotoxicity (ADCC) and anticancer efficacy.