Purpose: Human interleukin-21 (IL-21) is a pleiotropic class I cytokine that activates CD8 + T cells and natural killer cells.We report a phase 1study of recombinant human IL-21in patients with surgically incurable metastatic melanoma. The primary objective was to investigate safety and tolerability by determining dose-limiting toxicity (DLT). The secondary objectives were to identify a dose response for various biomarkers in the peripheral blood, estimate the minimum biologically effective dose, determine the pharmacokinetics of IL-21, determine if anti-IL-21 antibodies were induced during therapy, and measure effects on tumor size according to Response Evaluation Criteria in Solid Tumors. Experimental Design: Open-label, two-arm, dose escalation trial of IL-21 administered by i.v. bolus injection at dose levels from 1 to 100 Ag/kg using two parallel treatment regimens: thrice weekly for 6 weeks (3/wk) or three cycles of daily dosing for 5 days followed by 9 days of rest (5+9). Results: Twenty-nine patients entered the study. IL-21was generally well tolerated and no DLTs were observed at the 1, 3, and 10 Ag/kg dose levels. In the 3/wk regimen, DLTs were increased in alanine aminotransferase, neutropenia, and lightheadedness with fever and rigors. DLTs in the 5+9 regimen were increased in aspartate aminotransferase and alanine aminotransferase, neutropenia, fatigue, and thrombocytopenia. The maximum tolerated dose was declared to be 30 Ag/kg for both regimens. Effects on biomarkers were observed at all dose levels, including increased levels of soluble CD25 and up-regulation of perforin and granzyme B mRNA in CD8 + cells. One partial tumor response observed after treatment with IL-21 for 2 Â 6 weeks (3/wk) became complete 3 months later. Conclusions: IL-21 is biologically active at all dose levels administered and is generally well tolerated, and phase 2 studies have commenced using 30 Ag/kg in the 5+9 regimen.

Purpose: Human interleukin-21 (IL-21) is a class I cytokine that mediates activation of CD8 + T cells, natural killer (NK) cells, and other cell types. We report final clinical and biological results of a phase II study of recombinant human IL-21 (rIL-21) in patients with metastatic melanoma. Experimental Design: Open-label, single-arm, two-stage trial. Eligibility criteria: unresectable metastatic melanoma, measurable disease by Response Evaluation Criteria in Solid Tumors, no prior systemic therapy (adjuvant IFN permitted), adequate major organ function, good performance status, no significant autoimmune disease, and life expectancy at least 4 months. Primary objective: antitumor efficacy (response rate). Secondary objectives: safety, blood biomarkers, and generation of anti-rIL-21 antibodies. rIL-21 (30 Ag/kg/dose) was administered by intravenous bolus injection in 8-week cycles (5 dosing days followed by 9 days of rest for 6 weeks and then 2 weeks off treatment). Results: Stage I of the study comprised 14 patients. One confirmed complete response (CR) was observed, and as per protocol, 10 more patients were accrued to stage II (total n = 24: 10 female and 14 male). Best tumor response included one confirmed CR and one confirmed partial response, both with lung metastases. Treatment was overall well tolerated. Biomarker analyses showed increases in serum soluble CD25, frequencies of CD25 + NK and CD8 + Tcells, and mRNA for IFN-g, perforin, and granzyme B in CD8 + Tand NK cells. Conclusions: rIL-21administered at 30 Ag/kg/d in 5-day cycles every second week is biologically active and well tolerated in patients with metastatic melanoma. Confirmed responses, including one CR, were observed.

Summary Interleukin (IL)‐21 is a novel cytokine that has been shown to enhance proliferation and activation of CD8+ T cells, enhance natural killer (NK) cell activity and costimulate anti‐CD40‐driven B‐cell proliferation in mice. Several studies have furthermore demonstrated antitumour effects of IL‐21 administration in mouse models. In this study we have investigated how IL‐21 affects the survival and cytotoxicity of human NK cells and modulates their expression of surface receptors and of the effector molecules granzyme B and perforin. In contrast to murine NK cells, where IL‐21 alone cannot sustain survival, IL‐21 and IL‐2 were equally efficient in sustaining survival of human NK cells. In the absence of other cytokines, IL‐21 had little effect on expression of a panel of surface receptors on human NK cells. However, IL‐21 synergized with IL‐2 to up‐regulate several surface receptors, including NKG2A, CD25, CD86 and CD69. The CD25+ CD86+ NK cells were CD56bright and were large and granular. Expression of the effector molecules perforin and granzyme A and B was up‐regulated by IL‐21 at both mRNA and protein levels. Furthermore, IL‐21 increased the cytotoxicity of NK cells against K562 target cells. These findings suggest that IL‐21 modulates NK cell activity through induction of intracellular effector molecules as well as modulation of surface receptor expression.

In the past 20 years researchers have attempted to activate the host immune defence system to kill tumour cells and eradicate cancer. In some cases, the response of patients to immunotherapy has been extremely successful; however, other trials have shown disappointing results, and so there is a clear need for more effective therapies that can effectively adjunct conventional approaches. Interleukin 21 (IL21) is a new immune-stimulating cytokine that has demonstrated antitumour activity in several preclinical models, and has recently undergone Phase I trials in metastatic melanoma and renal cell carcinoma. Here, we provide an overview of the antitumour effects of IL21 and describe strategies to combine IL21 with other drugs for future cancer therapies.

Purpose Human interleukin-21 (IL-21) is a class I cytokine previously reported in clinical studies on immune responsive cancers. Here we report the eVects of systemic IL-21 therapy on the immune system in two phase 1 trials with this novel cytokine. Experimental design Recombinant IL-21 was administered by intravenous bolus injection at dose levels from 1 to 100 g/kg using two planned treatment regimens: thrice weekly for 6 weeks (3/week); or once daily for Wve consecutive days followed by nine dose-free days (5 + 9). The following biomarkers were studied in peripheral blood mononuclear cells (PBMC) during treatment: phosphorylation of STAT3, alterations in the composition of leukocyte subsets, ex vivo cytotoxicity, expression of eVector molecules in enriched CD8 + T cells and CD56 + NK cells by quantitative RT-PCR, and gene array proWling of CD8 + T cells. Results EVects of IL-21 were observed at all dose levels. In the 5 + 9 regimen IL-21 induced a dose dependent decrease in circulating NK cells and T cells followed by a return to baseline in resting periods. In both CD8 + T cells and CD56+ NK cells we found up-regulation of perforin and granzyme B mRNA. In addition, full transcriptome analysis of CD8 + T cells displayed changes in several transcripts associated with increased cell cycle progression, cellular motility, and immune activation. Finally, cytotoxicity assays showed that IL-21 enhanced the ability of NK cells to kill sensitive targets ex vivo. Conclusions IL-21 was biologically active at all dose levels administered with evidence of in vivo NK cell and CD8 + T cell activation.