Evaluation of the effect of TRU-016, an anti-CD37 directed SMIP in combination with other therapeutic drugs in models of non-Hodgkin's lymphoma

Abstract

8571 Background: TRU-016, a single chain anti-CD37 Fc fusion molecule has been shown to display pro-apoptotic and Fc-dependent cellular cytotoxicity activities against primary CLL cells and NHL cell lines. The pro-apoptotic signal generated by TRU-016 binding to CD37 on CLL cells has been shown to be caspase-independent and distinct from the signal generated by many other therapeutics including rituximab. We have tested drug combinations using the mantle cell lymphoma line Rec-1 and diffuse large B-cell lymphoma line SU-DHL-6 in vitro and extended these results to in vivo settings using the follicular lymphoma cell line DOHH2 treated with the combination of TRU-016 and bendamustine. Methods: To determine TRU-016 interactions with the established therapeutics rituximab, doxorubicin, rapamycin, and bendamustine, drugs were tested alone or in combination with TRU-016 and the anti-proliferative effects on cell lines measured after 96 hours. Combination index analysis was performed for drug combinations over the 20–90% effect levels using the Calcusyn software package. To determine if in vitro synergy could be recapitulated in vivo, SCID mice were implanted with DOHH2 cells and therapeutic treatment was initiated when tumor volumes reached 200 mm3. Treatments consisted of TRU-016, bendamustine, or the combination of TRU-016 and bendamustine. Results: Combination index analyses determined that TRU-016 is synergistic with rituximab, bendamustine, or rapamycin and additive with doxorubicin in NHL models. In vivo results show that treatment with the combination of TRU-016 and bendamustine resulted in increased efficacy compared to the efficacy attained with the individual drugs. This demonstrates that the in vitro synergy results were extendable to a more complex in vivo disease model. Conclusions: TRU-016 in combination with rituximab, rapamycin, or bendamustine increases cell killing of NHL cells. Furthermore, the combination of TRU-016 and bendamustine displayed greater in vivo anti-tumor activity than either agent alone against a follicular lymphoma tumor model. [Table: see text]