Novel humanized anti‐CD20 antibody BM‐ca binds to a unique epitope and exerts stronger cellular activity than others

Abstract

Cellular activity of BM-ca, a novel humanized anti-CD20 antibody, was quantitatively compared with that of two other anti-CD20 antibodies used for clinical practice, rituximab and ofatumumab. The results of a complement-dependent cytotoxicity (CDC) assay revealed that the strongest antibody was ofatumumab, followed by BM-ca, with rituximab being the weakest. Ofatumumab and BM-ca were effective not only against rituximab-sensitive SU-DHL-4 cells but also against rituximab-resistant RC-K8 cells. In an antibody-dependent cell-mediated cytotoxicity (ADCC) assay, although the effective concentrations against SU-DHL-4 cells were almost the same among these three antibodies, the maximum cytotoxic level was the highest for BM-ca. In an anti-cell proliferation assay using SU-DHL-4 cells, BM-ca was the most effective and ofatumumab, the weakest. Against RC-K8 cells, only BM-ca was effective. When combined with each of four cancer chemotherapeutics (prednisolone, vincristine, hydroxydaunorubicin, and cisplatin), BM-ca exerted the most effective combinatorial anti-cell proliferation activity. To assess the in vivo effect of BM-ca, we intravenously administered BM-ca into cynomolgus monkeys and found that the peripheral B-cell levels did not decrease in half of the animals. Sequencing of cDNA encoding CD20 of cynomolgus monkeys revealed that the responders and nonresponders had Leu/Pro (hetero) and Leu/Leu (homo) at amino acid (a.a.) position 160, respectively, suggesting that the epitope recognized by BM-ca was around this a.a. By analyzing reactivity to synthetic peptides, the epitope recognized by BM-ca was estimated to be a.a.'s 156–166, not shared with rituximab and ofatumumab. These results suggest BM-ca to be a promising anti-CD20 antibody having superior properties and recognizing a unique epitope.

A curative combination cancer therapy achieves high fractional cell killing through low cross-resistance and drug additivity

“…Rituximab kills B-cell lymphomas through multiple CD20-dependent mechanisms that include complement-mediated cytotoxicity (CMC), antibody-dependent cell cytotoxicity (ADCC) and direct killing via CD20 cross-linking (Weiner, 2010). Consistent with previous reports (Kobayashi et al, 2013), we observed that rituximab can kill DLBCL cells in culture via CMC when human serum is included in the culture media (Figure 1—figure supplement 1A). Among seven DLBCL cell lines tested, none exhibited a cytotoxic response to prednisolone alone at clinically relevant concentrations, although the rate of cell division was reduced (Figure 1—figure supplement 1B).…”

An update on newer monoclonal antibodies in lymphoma therapy

“…[30] BM-ca A novel humanized anti-CD20 antibody similar to ofatumumab with regards to its potent effect against rituximab-sensitive SU-DHL-4 cells and rituximab-resistant RC-K8 cells. [34] BM-ca binds to a unique epitope and possesses properties of both Type I and II antibodies. Kobayashi et al, study showed that ADCC and anti-proliferative effect of BM-ca was more potent than other anti-CD20 mAb.…”

“…Kobayashi et al, study showed that ADCC and anti-proliferative effect of BM-ca was more potent than other anti-CD20 mAb. [34] Vega et al conducted a study and hypothesized that BM-ca may be superior to rituximab in inhibiting the pathways (NF-kB and p38 MAPK) and are partly responsible for cell growth and response to cytotoxic therapy. [35] This is accounted to the fact that BM-ca binds to a different epitope than rituximab or ofatumumab that results in its higher affinity and exhibits different molecular signaling.…”

Anti-drug Antibodies Against a Novel Humanized Anti-CD20 Antibody Impair Its Therapeutic Effect on Primary Biliary Cholangitis in Human CD20- and FcγR-Expressing Mice

“…In this study, we studied a novel humanized IgG1 antibody against hCD20 that is less immunogenic compared with chimeric antibodies, enabling intermittent administration with much lower risk of anti-humanized antibody development during treatment of human PBC [Figure 1A ; ( 41 )]. This antibody (TKM-011, formerly called BM-ca) has significant direct cytotoxic activity as well as antibody-dependent cell-mediated cytotoxicity (ADCC) activity, similar to rituximab and ofatumumab ( 42 – 44 ). To better reflect human immunobiology, we generated dnTGF-βRII mice expressing hCD20 as well as human Fcγ receptors (hFcγRs) (Figure 1B ).…”