Abstract A12: Small molecule inhibitor of BCL2 in combination with RCHOP is effective in CD20 negative DLBCL.

Abstract

Abstract Rituximab alone or in combination with chemotherapeutics is the first-line therapy for diffuse large B cell lymphomas (DLBCL). Although the complete response rate is quite impressive, vast majority of patient presents recurrent disease. The association between CD20 expression and clinical outcome in patients strongly suggests that reduced CD20 expression leads to inferior response to RCHOP (rituximab, cyclophosphamide, vincristine, doxorubicin and prednisone). In order to understand how loss of CD20 leads to development of RCHOP resistance, we developed rituximab resistant DoHH2 model in vivo by chronic exposure to rituximab. Characterization of several resistant in vivo xenografts revealed one model that maintained resistance to an acute dose of rituximab and demonstrated loss of CD20. Further characterization of the model demonstrated a loss of CD20 is associated with over expression of BCL2 and BIM. In vivo efficacy studies showed resistant line is insensitive to acute dose of RCHOP and treatment with an inhibitor of BCL2 (ABT199) in combination with chemotherapy resulted in better efficacy than RCHOP alone. We have identified an in vivo model of DLBCL where loss of CD20 and over expression of anti-apoptotic protein BCL2 leads to RCHOP resistance. These data suggest the addition of BCL2 inhibitor to chemotherapy might be effective in treating CD20 negative lymphomas. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):A12. Citation Format: Chaitali Dutta, Michele Mayo, Mike Collins, Christopher Brueckner, Deborah Lawson, Zhongwu Lai, Larry Bao, Corinne Reimer. Small molecule inhibitor of BCL2 in combination with RCHOP is effective in CD20 negative DLBCL. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr A12.