Purpose Interleukin-15 (IL-15) has significant potential in cancer immunotherapy as an activator of antitumor CD8 T and natural killer (NK) cells. The primary objectives of this trial were to determine safety, adverse event profile, dose-limiting toxicity, and maximum-tolerated dose of recombinant human IL-15 (rhIL-15) administered as a daily intravenous bolus infusion for 12 consecutive days in patients with metastatic malignancy. Patients and Methods We performed a first in-human trial of Escherichia coli–produced rhIL-15. Bolus infusions of 3.0, 1.0, and 0.3 μg/kg per day of IL-15 were administered for 12 consecutive days to patients with metastatic malignant melanoma or metastatic renal cell cancer. Results Flow cytometry of peripheral blood lymphocytes revealed dramatic efflux of NK and memory CD8 T cells from the circulating blood within minutes of IL-15 administration, followed by influx and hyperproliferation yielding 10-fold expansions of NK cells that ultimately returned to baseline. Up to 50-fold increases of serum levels of multiple inflammatory cytokines were observed. Dose-limiting toxicities observed in patients receiving 3.0 and 1.0 μg/kg per day were grade 3 hypotension, thrombocytopenia, and elevations of ALT and AST, resulting in 0.3 μg/kg per day being determined the maximum-tolerated dose. Indications of activity included clearance of lung lesions in two patients. Conclusion IL-15 could be safely administered to patients with metastatic malignancy. IL-15 administration markedly altered homeostasis of lymphocyte subsets in blood, with NK cells and γδ cells most dramatically affected, followed by CD8 memory T cells. To reduce toxicity and increase efficacy, alternative dosing strategies have been initiated, including continuous intravenous infusions and subcutaneous IL-15 administration.

Lymphomas express a tumor-specific antigen which can be targeted by cancer vaccination. We evaluated the ability of a new idiotype protein vaccine formulation to eradicate residual t(14;18)+ lymphoma cells in 20 patients in a homogeneous, chemotherapy-induced first clinical complete remission. All 11 patients with detectable translocations in their primary tumors had cells from the malignant clone detectable in their blood by PCR both at diagnosis and after chemotherapy, despite being in complete remission. However, 8 of 11 patients converted to lacking cells in their blood from the malignant clone detectable by PCR after vaccination and sustained their molecular remissions. Tumor-specific cytotoxic CD8+ and CD4+ T cells were uniformly found (19 of 20 patients), whereas antibodies were detected, but apparently were not required for molecular remission. Vaccination was thus associated with clearance of residual tumor cells from blood and long-term disease-free survival. The demonstration of molecular remissions, analysis of cytotoxic T lymphocytes against autologous tumor targets, and addition of granulocyte-monocyte colony-stimulating factor to the vaccine formulation provide principles relevant to the design of future clinical trials of other cancer vaccines administered in a minimal residual disease setting.

Interleukin-7 (IL-7) is important for thymopoiesis in mice and humans because IL-7 receptor ␣ (IL-7R␣) mutations result in a severe combined immunodeficiency phenotype with severe thymic hypoplasia. Recent evidence has indicated that IL-7 also plays an important role as a regulator of T-cell homeostasis. Here we report the immunologic effects of recombinant human IL-7 (rhIL-7) therapy in normal and simian immunodeficiency virus (SIV)-infected nonhuman primates. Cynomolgus monkeys receiving 10 days of rhIL-7 showed substantial, reversible increases in T-cell numbers involving a dramatic expansion of both naive and nonnaive phenotype CD4 ؉ and CD8 ؉ subsets. Although IL-7 is known to have thymopoietic effects in mice, we observed marked declines in the frequency and absolute number of T-cell receptor excision circlepositive (TREC ؉ ) cells in the peripheral blood and dramatic increases in the percentage of cycling T cells in the peripheral blood as measured by Ki-67 expression (baseline less than 5% to approximately 50% after 6 days of therapy) and ex vivo bromodeoxyuridine (BrdU) incorporation. Similarly, moderately CD4-depleted SIV-infected macaques treated with rhIL-7 also had significant increases in peripheral blood CD4 ؉ and CD8 ؉ T cells following rhIL-7 therapy. Thus, rhIL-7 induces dramatic alterations in peripheral T-cell homeostasis in both T-cellreplete and T-cell-depleted nonhuman primates. These results further implicate IL-7 as a promising immunorestorative agent but illustrate that a major component of its immunorestorative capacity reflects effects on mature cells. These results also raise the possibility that IL-7 therapy could be used to temporarily modulate Tcell cycling in vivo in the context of immunotherapies such as vaccination. (Blood. 2003;