Two mechanisms of the enhanced antibody-dependent cellular cytotoxicity (ADCC) efficacy of non-fucosylated therapeutic antibodies in human blood

Abstract

BackgroundAntibody-dependent cellular cytotoxicity (ADCC) has recently been identified as one of the critical mechanisms underlying the clinical efficacy of therapeutic antibodies, especially anticancer antibodies. Therapeutic antibodies fully lacking the core fucose of the Fc oligosaccharides have been found to exhibit much higher ADCC in humans than their fucosylated counterparts. However, data which show how fully non-fucosylated antibodies achieve such a high ADCC in human whole blood have not yet been disclosed. The precise mechanisms responsible for the high ADCC mediated by fully non-fucosylated therapeutic antibodies, even in the presence of human plasma, should be explained based on direct evidence of non-fucosylated antibody action in human blood.MethodsUsing a human ex vivo B-cell depletion assay with non-fucosylated and fucosylated anti-CD20 IgG1s rituximab, we monitored the binding of the therapeutic agents both to antigens on target cells (target side interaction) and to leukocyte receptors (FcγR) on effector cells (effector side interaction), comparing the intensities of ADCC in human blood.ResultsIn the target side interaction, down-modulation of CD20 on B cells mediated by anti-CD20 was not observed. Simple competition for binding to the antigens on target B cells between fucosylated and non-fucosylated anti-CD20s was detected in human blood to cause inhibition of the enhanced ADCC of non-fucosylated anti-CD20 by fucosylated anti-CD20. In the effector side interaction, non-fucosylated anti-CD20 showed sufficiently high FcγRIIIa binding activity to overcome competition from plasma IgG for binding to FcγRIIIa on natural killer (NK) cells, whereas the binding of fucosylated anti-CD20 to FcγRIIIa was almost abolished in the presence of human plasma and failed to recruit NK cells effectively. The core fucosylation levels of individual serum IgG1 from healthy donors was found to be so slightly different that it did not affect the inhibitory effect on the ADCC of fucosylated anti-CD20.ConclusionOur results demonstrate that removal of fucosylated antibody ingredients from antibody therapeutics elicits high ADCC in human blood by two mechanisms: namely, by evading the inhibitory effects both of plasma IgG on FcγRIIIa binding (effector side interaction) and of fucosylated antibodies on antigen binding (target side interaction).

Glycovariant anti-CD37 monospecific protein therapeutic exhibits enhanced effector cell-mediated cytotoxicity against chronic and acute B cell malignancies

“…Previous studies have shown that changing the glycosylation pattern of the Fc portion of antibodies can influence their ability to elicit effector function by enhancing their binding affinity to FcγRIIIa on human immune cells. 14,27 We saw similar enhanced affinity to FcγRIIIa with SMIP-016 GV (Fig. 1C).…”

“…Radio-labeled mouse monoclonal antibodies Fc oligosaccharides elicit high ADCC responses by two mechanisms. 14 On the effector cell side, afucosylated anti-CD20 antibodies were less inhibited by human plasma IgG. On the target cells, cells treated with non-fucosylated anti-CD20 antibodies showed markedly stronger binding to NK cells than fucosylated anti-CD20.…”

“…On the target cells, cells treated with non-fucosylated anti-CD20 antibodies showed markedly stronger binding to NK cells than fucosylated anti-CD20. 14 Due to the success of the parent compound SMIP-016, we sought to determine if modifying the Fc oligosaccharides of a SMIP protein would enhance its activity. Herein, we describe a second generation anti-CD37 SMIP molecule, SMIP-016 GV , with an afucosylated Fc receptor binding region designed for enhanced effector function.…”

Novel anti–B-cell maturation antigen antibody-drug conjugate (GSK2857916) selectively induces killing of multiple myeloma

“…38 Defucosylation of Fc glycans could also circumvent the inhibitory effects both of plasma IgG on the binding of FcgRIIIa on NK cells and of fucosylated counterparts on the binding of the antigen on target cells. [39][40][41] Importantly, J6M0-mcMMAF and naked J6M0 significantly enhanced ADCC in vitro and anti-MM activity in vivo, when compared with its fucosylated normal Fc version. To our knowledge, J6M0-mcMMAF would be the first therapeutic ADC with defucosylated oligosaccharides entering clinical trials in MM.…”

Tailoring recombinant protein quality by rational media design

“…It is not surprising that increasing effector functions by means of Fc-glycosylation engineering has gained considerable interest 196 . As a consequence, the pharmaceutical industry has allocated remarkable research efforts to glycan engineering, aiming to increase ADCC of mAbs, in particular by limiting core fucosylation 48,65,91,[308][309][310][311][312][313] . Many reports have described the significant increase of ADCC whenever the fucose attachment to the glycan backbone was precluded 42,196,308,312 .…”