ZymoGenetics announced that a Phase I clinical trial is under way using Interleukin 21 (IL-21) in combination with the monoclonal antibody Rituxan. The open-label, dose-escalation trial is enrolling patients with advanced non- Hodgkin's lymphoma (NHL) in a multisite study conducted in the U.S. Patients will be treated with Rituxan and IL-21 once weekly for four weeks. Responding patients will be offered the combination regimen for four additional weeks.

The primary objective of the study is to evaluate the safety and tolerability of IL-21 when administered with Rituxan. Secondary objectives are to characterize the pharmacokinetics, immunogenicity and preliminary evidence of tumor activity of this combination.

Preclinical research into this combination offers evidence for entering clinical trials, largely because IL-21 appears to enhance a principal mechanism by which Rituxan is thought to work.