Novel type II anti-CD20 monoclonal antibody (GA101) evokes homotypic adhesion and actin-dependent, lysosome-mediated cell death in B-cell malignancies

Abstract

The anti-CD20 mAb rituximab has substantially improved the clinical outcome of patients with a wide range of B-cell malignancies. However, many patients relapse or fail to respond to rituximab, and thus there is intense investigation into the development of novel anti-CD20 mAbs with improved therapeutic efficacy. Although Fc-Fc␥R interactions appear to underlie much of the therapeutic success with rituximab, certain type II anti-CD20 mAbs efficiently induce programmed cell death (PCD), whereas rituximab-like type I anti-CD20 mAbs do not. Here, we show that the humanized, glycoengineered anti-CD20 mAb GA101 and derivatives harboring non-glycoengineered Fc regions are type II mAb that trigger nonapoptotic PCD in a range of B-lymphoma cell lines and primary B-cell malignancies. We demonstrate that GA101-induced cell death is dependent on actin reorganization, can be abrogated by inhibitors of actin polymerization, and is independent of BCL-2 overexpression and caspase activation. GA101-induced PCD is executed by lysosomes which disperse their contents into the cytoplasm and surrounding environment. Taken together, these findings reveal that GA101 is able to potently elicit actin-dependent, lysosomal cell death, which may potentially lead to improved clearance of B-cell malignancies in vivo. IntroductionThe addition of the anti-CD20 mAb rituximab to chemotherapy has substantially improved the clinical outcome for many patients with a wide range of B-cell malignancies. 1-3 However, despite the unprecedented success of rituximab, a substantial proportion of patients with CD20-positive B-cell malignancies fail to achieve a complete remission or relapse after receiving rituximab-containing immunochemotherapy. 4 These areas of unmet clinical need highlight the requirement to develop improved treatments for these patients. Given both the success with rituximab and the rapid development of mAb engineering technology, there is currently intense investigation into the development of novel anti-CD20 mAbs aimed at improving therapeutic efficacy. Central to this challenge, is an enhanced understanding of the mechanism of action of anti-CD20 mAbs.Anti-CD20 mAbs can activate a range of potential tumor cell killing pathways (reviewed in Lim et al 5 ) including Fc-Fc␥ receptor (Fc␥R) interactions (namely Ab-dependent cellular cytotoxicity [ADCC] and phagocytosis mediated by Fc␥R-expressing immune effector cells such as macrophages and/or NK cells), complement-dependent cytotoxicity (CDC), or the direct induction of programmed cell death (PCD). Although it is well established that Fc-Fc␥R interactions are critical for the in vivo efficacy of anti-CD20 mAbs, 6-8 the role of complement remains disputed as to whether it is beneficial, 9,10 inconsequential, 7,11,12 or even detrimental to anti-CD20 mAb efficacy. 13,14 However, the potential importance of PCD in enhancing anti-CD20 mAb potency remains largely underinvestigated, perhaps because it does not appear to play a major role in the therapeutic efficacy of rituximab. 15 We have c...

Antitumor activity of an anti‐CD98 antibody

“…26 Obinutuzumab not only possesses ADCC activity, but also exhibits multiple MOAs in vitro, including enhanced noncaspase-dependent induction of direct cell death. 25 Similarly, IGN523 possesses multiple mechanisms of action, as shown here in several cell lines in vitro (Fig. 6).…”

“…25 To assess whether similar effects are seen with IGN523 plus crosslinker, we investigated if the CD98-IGN523 complex was internalized to lysosomes and whether this led to increased lysosomal permeability (Fig. 5).…”

Refractory chronic lymphocytic leukemia - new therapeutic strategies

“…Also direct cytotoxicity is enhanced. CD20 binding leads to homotypic adhesion and following cell death induction is non-apoptotic, actin-dependent and lysosome mediated [23]. Further in vitro studies showed depletion of CLL cells in whole blood assays and the superior efficacy of GA-101 compared to rituximab [24].…”

Antibody modulation: Limiting the efficacy of therapeutic antibodies

“…Type I display a potent ability to activate complement through enhanced recruitment of C1q [12] due to the efficient clustering of antibody Fc regions [13]; an activity directly linked to their ability to redistribute CD20 to lipid raft microdomains of the plasma membrane. In contrast, type II anti-CD20 mAb do not display either of these properties but instead evoke strong homotypic adhesion [14] and a non-apoptotic form of lysosomal cell death [14][15][16][17]. In addition, we observed that type I anti-CD20 mAb undergo more rapid internalization from the cell surface, in contrast to type II mAb [18][19][20].…”