Enhanced anti-tumor activity of the glycoengineered type II CD20 antibody obinutuzumab (GA101) in combination with chemotherapy in xenograft models of human lymphoma.

Obinutuzumab (GA101) is a novel glycoengineered type II CD20 antibody in development for non-Hodgkin lymphoma. We compared the anti-tumor activity of obinutuzumab and rituximab in preclinical studies using subcutaneous Z138 and WSU-DLCL2 xenograft mouse models. Obinutuzumab and rituximab were assessed alone and in combination with bendamustine, fludarabine, chlorambucil, doxorubicin and cyclophosphamide/vincristine. Owing to strong single-agent efficacy in these models, suboptimal doses of obinutuzumab were applied to demonstrate a combination effect. Obinutuzumab plus bendamustine achieved superior tumor growth inhibition versus rituximab plus bendamustine and showed a statistically significant effect versus the respective single treatments. Combinations of obinutuzumab with fludarabine, chlorambucil or cyclophosphamide/vincristine demonstrated significantly superior activity to rituximab-based treatment. Obinutuzumab monotherapy was at least as effective as rituximab plus chemotherapy in vivo, and obinutuzumab plus chemotherapy was superior to the respective monotherapies. These data support further clinical investigation of obinutuzumab plus chemotherapy.

Preclinical activity of the type II CD20 antibody GA101 (obinutuzumab) compared with rituximab and ofatumumab in vitro and in xenograft models.

We report the first preclinical in vitro and in vivo comparison of GA101 (obinutuzumab), a novel glycoengineered type II CD20 monoclonal antibody, with rituximab and ofatumumab, the two currently approved type I CD20 antibodies. The three antibodies were compared in assays measuring direct cell death (AnnexinV/PI staining and time-lapse microscopy), complement-dependent cytotoxicity (CDC), antibody-dependent cell-mediated cytotoxicity (ADCC), antibody-dependent cell-mediated phagocytosis (ADCP), and internalization. The models used for the comparison of their activity in vivo were SU-DHL4 and RL xenografts. GA101 was found to be superior to rituximab and ofatumumab in the induction of direct cell death (independent of mechanical manipulation required for cell aggregate disruption formed by antibody treatment), whereas it was 10 to 1,000 times less potent in mediating CDC. GA101 showed superior activity to rituximab and ofatumumab in ADCC and whole-blood B-cell depletion assays, and was comparable with these two in ADCP. GA101 also showed slower internalization rate upon binding to CD20 than rituximab and ofatumumab. In vivo, GA101 induced a strong antitumor effect, including complete tumor remission in the SU-DHL4 model and overall superior efficacy compared with both rituximab and ofatumumab. When rituximab-pretreated animals were used, second-line treatment with GA101 was still able to control tumor progression, whereas tumors escaped rituximab treatment. Taken together, the preclinical data show that the glyoengineered type II CD20 antibody GA101 is differentiated from the two approved type I CD20 antibodies rituximab and ofatumumab by its overall preclinical activity, further supporting its clinical investigation.