Purpose: This phase I study in patients with metastatic melanoma (MM) and renal cell carcinoma (RCC) evaluated the safety and maximum tolerated dose (MTD), pharmacokinetics, pharmacodynamics, and preliminary antitumor activity of s.c. treatment of human recombinant interleukin 21 (IL-21).

Experimental Design: Phase I dose-escalation trial with treatment of three to six patients at each dose level, escalating from 3 to 300 μg/kg. Treatment was administered s.c. on an outpatient basis 3 days per week for 8 or 16 weeks.

Results: Twenty-six patients entered the study. Recombinant IL-21 was generally well tolerated, and dose-limiting toxicities (DLT) were first seen at dose levels of 200 and 300 μg/kg. The following four DLTs were observed in three patients: increased transaminases, increased hyperbilirubinemia, hypersensitivity reaction, and lethargy. The MTD was declared to be 200 μg/kg, although five of seven patients at the 300 μg/kg dose level experienced no DLTs. A treatment-related effect on soluble CD25 was observed at all dose levels and increased with dose level. Furthermore, higher doses induced interferon-γ, perforin, and granzyme B mRNA expression in peripheral blood, and granzyme B protein expression in both CD8⁺ T cells and natural killer cells, consistent with the activation of cytotoxic lymphocytes. Three patients, one patient with MM and two with RCC, obtained a partial response.

Conclusion: Outpatient treatment with s.c. administered IL-21 was tolerated and had dose-dependent pharmacodynamics. rIL-21 showed antitumor activity in patients with MM and RCC. Clin Cancer Res; 16(21); 5312–9. ©2010 AACR.