Glycan variants of a respiratory syncytial virus antibody with enhanced effector function and in vivo efficacy

Abstract

Respiratory syncytial virus (RSV) can cause devastating lower respiratory tract infections in preterm infants or when other serious health problems are present. Immunoprophylaxis with palivizumab (Synagis), a humanized IgG1 mAb, is the current standard of care for preventing RSV infection in at-risk neonates. We have explored the contribution of effector function to palivizumab efficacy using a plant-based expression system to produce palivizumab N-glycan structure variants with high homogeneity on different antibody isotypes. We compared these isotype and N-glycoform variants with commercially available palivizumab with respect to both in vitro receptor and C1q binding and in vivo efficacy. Whereas the affinity for antigen and neutralization activity of each variant were indistinguishable from those of palivizumab, their Fcγ receptor binding profiles were very different, which was reflected in either a reduced or enhanced ability to influence the RSV lung titer in challenged cotton rats. Enhanced Fcγ receptor binding was associated with reduced viral lung titers compared with palivizumab, whereas abrogation of receptor binding led to a drastic reduction in efficacy. The results support the hypotheses that classic antibody neutralization is a minor component of efficacy by palivizumab in the cotton rat and that antibody-dependent cell-mediated cytotoxicity activity can significantly enhance the efficacy of this antiviral mAb.

Monoclonal antibody therapy for Junin virus infection

“…These observations support the use of the guinea pig model for studying the efficacy of antibodies with human constant regions (e.g., chimeric or fully human mAbs). The difference in efficacy between IgG and F(ab′) 2 reported by Kenyon et al is consistent with a growing body of evidence with a variety of viruses suggesting classic neutralization of free virus (i.e., antibody bound to virus sterically hinders binding to, fusion with, or internalization by a host target cell) may not be the primary mechanism by which anti-viral mAbs function in vivo, and that Fcγ receptor-mediated immune functions play a pivotal role (14,15,(19)(20)(21). Although all three chimeric mAbs contained the same human Fc isotype (IgG 1 ), the protective efficacy directly correlated with virus neutralization.…”

“…Email: larry.zeitlin@mappbio.com or twgeisbe@UTMB.EDU. transgenic N. benthamiana (14,15), with greater than 75% of the GnGn glycoform.…”

The “less-is-more” in therapeutic antibodies: Afucosylated anti-cancer antibodies with enhanced antibody-dependent cellular cytotoxicity

“… 133 Humanized IgG1     TrasGEX/ GT-MAB7.3-GEX/Glycooptimized Trastuzumab-GEXHER2ReducedHuman glycoengineered production cell lines (GlycoExpress technology)Potent Her2 + BT474 tumor growth inhibition in nude mice but exhibited similar tumor volume and number of regression between fucosylated and reduced fucosylated antibodies(c)Humanized IgG1     Lumretuzumab /RG7116/RO5479599/ GE-HuMAb-HER3HER3ReducedCoexpression with GnT-III and α-ManII in CHO cells (GlycoMAb Technology)Enhanced survival of SCID-beige mice with A549-B34 NSCLC xenograftsMirschberger et al. 134 Humanized IgG1   Enhanced tumor inhibition in A549 orthotopic mouse models over WT-huMab-HER3 Palivizumab-NRespiratory syncytial virus (RSV)afucosylatedTransgenic N. benthamiana with RNAi to eliminate the expression of plant specific xylosyl and fucosyl transferase genesEnhanced RSV protection in rat models over fucosylated counterpart(d)Humanized IgG1     h-13F6Heavily glycosylated mucin-like domain of EBOV glycoprotein (GP)afucosylated N. benthamiana plants with RNAi to eliminate the expression of plant specific xylosyl and fucosyl transferase genesEnhanced anti-viral protection over CHO cells-produced fucosylated counterpartHiatt et al, 114 Zeitlin et al, 115 Chimeric IgG1     LSEVh-LS-F Hexavalent fusion protein with IgG1 FcCD4 and HIV-1 gp120-binding sitesafucosylatedGDP-fucose transporter −/− CHO cells…”

“…Antibodies against RSV, EBOV and HIV have been glycoengineered to become afucosylated to further improve their anti-viral activity 84 114 , 115 Enhanced binding to the FcγR by these afucosylated antibodies was correlated with enhanced efficacy in murine models 114 115 For example, the afucosylated gp120-bispecific and hexavalent broadly neutralizing fusion protein – LSEVh-LS-F also showed potent inhibition of HIV-1 and simian-HIV infection in humanized mouse and macaque models through NK-cell mediated ADCC 84 …”

Afucosylated Biosimilars need Afucosylation Specific Assays

“…Afucosylated IgG1 exhibit greatly enhanced FcγRIIIa binding and increased FcγRIIIa-mediated antigen dependent cellular cytotoxity (ADCC). These considerations directly impact biologics such as Rituximab and Palivizumab whose MOA involves Fc mediated effector functions [3,4]. Therefore follow-on biologics in this class are faced with the task of reproducing the distribution of afucosylated glycoform and demonstrating equivalent biological activity.…”