The study is part of a larger clinical program examining the use of Interleukin-21 (IL-21) both as a single agent and in combination with approved cancer therapeutics.
The study evaluated three dose levels of IL-21 (30, 100 and 150mcg/kg), given intravenously once per week in combination with a standard dose of rituximab (375mg/m2) for four weeks. While no dose-limiting toxicities were seen at any dose level, a dose of 100mcg/kg of IL-21 in combination with rituximab was selected for cohort expansion as re-treatment at 150mcg/kg was associated with increased toxicity. The majority of adverse events and lab abnormalities at all dose levels were Grade 1 or 2 and included flu-like symptoms, headache, fatigue and nausea. One subject with a prior history of cardiac disease who experienced chest pain during the study died of complications after a stenting procedure and was not evaluable for response.
Evidence of antitumor activity was seen in this heavily pretreated group of patients, most of whom had previously received rituximab. Best response during the study, per investigator assessment, included two complete responses, four partial responses, seven stable disease and one progressive disease. Final data from the study will provide more information about the overall safety and antitumor effects of this combination therapy.