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3040 Background: Galiximab, a primatized monoclonal antibody that binds with high affinity to CD80 and mediates antibody- dependent, cell-mediated cytotoxicity in vitro, is currently under investigation for the treatment of follicular non-Hodgkin’s lymphoma (NHL). In a phase I/II monotherapy study, galiximab produced an overall response rate of 11%, and tumor reductions were observed in 46% of patients. Initial clinical trials also demonstrate that galiximab is well tolerated and suggest that combining galiximab with rituximab (anti-CD20) provides clinical benefit. These results are consistent with preclinical studies in murine lymphoma xenograft model systems, which demonstrate the superiority of combination therapy. Methods: To further define the therapeutic potential of galiximab, the Raji subcutaneous and the SKW disseminated lymphoma murine xenograft models were used to define the in vivo efficacy of galiximab alone or in combination with fludarabine or doxorubicin. Similar studies were performed with rituximab. Results: In the Raji model, both galiximab and rituximab exhibited maximal inhibition of the growth of preestablished (150-mg) tumors at a dose of 3 mg/kg/wk. Interestingly, higher doses of galiximab (but not rituximab) showed reduced inhibition. Galiximab (3 mg/kg/wk) inhibited tumor growth alone (P No significant financial relationships to disclose.