Chemotherapy-Refractory Diffuse Large B-Cell Lymphomas (DLBCL) Are Effectively Killed by Ofatumumab-Induced Complement-Mediated Cytoxicity.

Abstract

The combination of chimeric CD20 monoclonal antibody (mAb) rituximab (R) with chemotherapy (CHOP) has significantly improved clinical outcome in patients with diffuse large B-cell lymphoma (DLBCL). However, the efficacy of R-CHOP is variable and DLBCL remains fatal in 30–40% of the patients. We recently developed the novel fully human CD20 mAb, ofatumumab (2F2) that is currently in clinical development for CLL and follicular lymphoma (phase III) and rheumatoid arthritis (phase II). In this study, we compared ofatumumab with rituximab for their ability to induce complement dependent cytotoxicity (CDC) of isolated lymphoma cells of chemotherapy-refractory DLBCL patients. Human type II CD20 mAb 11B8 does not induce CDC and was used as a control. Ofatumumab and rituximab induced CDC of all DLBCL samples tested, including the DLBCL cell lines SUDHL4, SUDHL5 and HT and lymphoma cells derived from ten chemotherapy-refractory DLBCL patients. Ofatumumab was significantly more effective in inducing CDC in nine out of ten DLBCL tumor samples when compared to rituximab (p=0.001, Two-way-Anova). The lethal doses (LD50) for ofatumumab (0.1 ± 2.8 μg/ml) was significantly lower when compared to the LD50 for rituximab (6.4 ± 4.9 μg/ml, p=0.04, Mann-Whitney test). The control CD20 mAb 11B8 showed no CDC induction of DLBCL cells. Sensitivity of DLBCL patient cells to ofatumumab- and rituximab-induced CDC negatively correlated with expression of complement defense molecule CD59, but not with expression of CD46, CD55, as determined by immunohistochemistry or apoptosis inhibitors Bcl-2 and XIAP. Functional inhibition of CD55 and CD59 using blocking mAb demonstrated that ofatumumab-induced CDC of DLBCL tumor cells was less sensitive to expression of these complement defense molecules than rituximab-induced CDC. We conclude that chemotherapy-refractory DLBCL cases are sensitive to CD20 mAb induced CDC with ofatumumab being the most effective mAb, especially in patients expressing high levels of CD59. Based on our results ofatumumab should be considered as a valuable therapy option for chemotherapy-refractory DLBCL patients.

A multicentre, phase II trial of ofatumumab monotherapy in relapsed/progressive diffuse large B‐cell lymphoma

“…(Teeling et al , ) In vitro studies demonstrated that ofatumumab effectively induces complement‐dependent cytotoxicity of chemotherapy‐refractory DLBCL cells. (Cillessen et al , ) Ofatumumab is approved for the treatment of patients with chronic lymphocytic leukaemia refractory to fludarabine and alemtuzumab and is currently in development for the treatment of NHL and other haematological malignancies. (Wierda et al , ; Czuczman et al , ,b) The present study was designed to investigate the efficacy and safety of single‐agent ofatumumab in patients with relapsed/progressive DLBCL who were ineligible for ASCT or who had relapse/progression after ASCT.…”

Anti-CD20 monoclonal antibodies: reviewing a revolution

“…145 Regarding ADCC, most data demonstrate relative equivalence between rituximab and ofatumumab, though some studies suggest that ofatumumab displays greater efficacy in this modality also.- 146,147 Preclinical studies of ofatumumab demonstrated superior in vitro activity in comparison to rituximab providing justification for further clinical trials. 146,148 Indolent hematological malignancies…”

Current challenges and novel treatment strategies in double hit lymphomas

“…While these agents have not been specifically tested in DHL a number are proving promising in relapsed or refractory DLBCL more generally. Approaches currently being explored include optimized anti-CD20 antibodies [Cillessen et al 2007; Morschhauser et al 2013], anti CD40 antibodies [Advani et al 2006], anti-PD1 monoclonal antibodies [ClinicalTrials.gov identifier: NCT02362997] and vascular endothelial growth factor (VEGF) antibodies [Willett et al 2004; Stopeck et al 2012]. In the search for efficacy, some monoclonal antibodies have been conjugated to a variety of drugs and radioactive molecules [Bartlett et al 2013; Advani et al 2010; Ribrag et al 2014; Morschhauser et al 2004].…”