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Engineered IgG1-Fc--one fragment to bind them all.

ABSTRACT: The crystallizable fragment (Fc) of the immunoglobulin class G (IgG) is a very attractive scaffold for the design of novel therapeutics due to its quality of uniting all essential antibody functions. This article reviews the functionalization of this homodimeric glycoprotein by diversification of structural loops of CH3 domains for the design of Fcabs, i.e. antigen-binding Fc proteins. It reports the design of libraries for the selection of nanomolar binders with wildtype-like in vivo half-life and correlation of Fc receptor binding and ADCC. The in vitro and preclinical biological activity of selected Fcabs is compared with that of clinically approved antibodies. Recently, the great potential of the scaffold for the development of therapeutics for clinical use has been shown when the HER2-binding Fcab FS102 entered clinical phase I. Furthermore, methods for the engineering of biophysical properties of Fcabs applicable to proteins in general are presented as well as the different approaches in the design of heterodimeric Fc-based scaffolds used in the generation of bispecific monoclonal antibodies. Finally, this work critically analyzes and compares the various efforts in the design of highly diverse and functional libraries that have been made in the engineering of IgG1-Fc and structurally similar scaffolds.

SUBMITTER: Lobner E

PROVIDER: S-EPMC4755133 | biostudies-literature | 2016 Mar

REPOSITORIES: biostudies-literature

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Engineered IgG1-Fc--one fragment to bind them all.

Lobner Elisabeth E Traxlmayr Michael W MW Obinger Christian C Hasenhindl Christoph C

Immunological reviews 20160301 1

The crystallizable fragment (Fc) of the immunoglobulin class G (IgG) is a very attractive scaffold for the design of novel therapeutics due to its quality of uniting all essential antibody functions. This article reviews the functionalization of this homodimeric glycoprotein by diversification of structural loops of CH3 domains for the design of Fcabs, i.e. antigen-binding Fc proteins. It reports the design of libraries for the selection of nanomolar binders with wildtype-like in vivo half-life ...[more]

PMID: 26864108

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Project description:The inhibition of Fcγ receptors (FcγR) is an attractive strategy for treating diseases driven by IgG immune complexes (IC). Previously, we demonstrated that an engineered tri-valent arrangement of IgG1 Fc domains (SIF1) potently inhibited FcγR activation by IC, whereas a penta-valent Fc molecule (PentX) activated FcγR, potentially mimicking ICs and leading to Syk phosphorylation. Thus, a precise balance exists between the number of engaged FcγRs for inhibition versus activation. Here, we demonstrate that Fc valency differentially controls FcγR activation and inhibition within distinct subcellular compartments. Large Fc multimer clusters consisting of 5-50 Fc domains predominately recruited Syk-mScarlet to patches on the plasma membrane, whereas PentX exclusively recruited Syk-mScarlet to endosomes in human monocytic cell line (THP-1 cells). In contrast, SIF1, similar to monomeric Fc, spent longer periods docked to FcγRs on the plasma membrane and did not accumulate and recruit Syk-mScarlet within large endosomes. Single particle tracking (SPT) of fluorescent engineered Fc molecules and Syk-mScarlet at the plasma membrane imaged by total internal reflection fluorescence microscopy (SPT-TIRF), revealed that Syk-mScarlet sampled the plasma membrane was not recruited to FcγR docked with any of the engineered Fc molecules at the plasma membrane. Furthermore, the motions of FcγRs docked with recombinant Fc (rFc), SIF1 or PentX, displayed similar motions with D ~ 0.15 μm2/s, indicating that SIF1 and PentX did not induce reorganization or microclustering of FcγRs beyond the ligating valency. Multicolor SPT-TIRF and brightness analysis of docked rFc, SIF1 and PentX also indicated that FcγRs were not pre-assembled into clusters. Taken together, activation on the plasma membrane requires assembly of more than 5 FcγRs. Unlike rFc or SIF1, PentX accumulated Syk-mScarlet on endosomes indicating that the threshold for FcγR activation on endosomes is lower than on the plasma membrane. We conclude that the inhibitory effects of SIF1 are mediated by stabilizing a ligated and inactive FcγR on the plasma membrane. Thus, FcγR inhibition can be achieved by low valency ligation with SIF1 that behaves similarly to FcγR docked with monomeric IgG.

Project description:BackgroundIgG4 anbibodies are deficient in stability and may contribute to tumor-associated escape from immune surveillance. We developed an IgG1 backbone anti-programmed cell death protein-1 (PD-1) antibody, penpulimab, which is designed to remove crystallizable fragment (Fc) gamma receptor (FcγR) binding that mediates antibody-dependent cell-mediated cytotoxicity (ADCC), antibody-dependent cellular phagocytosis (ADCP) and proinflammatory cytokine release.MethodsAggregation of different anti-PD-1 antibodies was tested by size exclusion chromatography, and melting temperature midpoint (Tm) and aggregation temperature onset (Tagg) were also determined. The affinity constants of penpulimab for PD-1 and human FcγRs were measured by surface plasmon resonance and biolayer interferometry. ADCC and ADCP were determined in cellular assays and antibody-dependent cytokine release (ADCR) from human macrophages was detected by ELISA. Binding kinetics of penpulimab to human PD-1 was determined by Biacore, and epitope/paratope mapping of PD-1/penpulimab was investigated using x-ray crystallography. Additionally, patients from six ongoing trials were included for analysis of immune-related adverse events (irAEs).ResultsPenpulimab demonstrated better stability and a lower level of host-cell protein residue compared with IgG4 backbone anti-PD-1 antibodies. As expected, penpulimab exhibited no apparent binding to FcγRIa, FcγRIIa_H131, FcγRIIIa_V158 and FcγRIIIa_F158, elicited no apparent ADCC and ADCP activities, and induced no remarkable IL-6 and IL-8 release by activated macrophages in vitro. Penpulimab was shown in the co-crystal study to bind to human PD-1 N-glycosylation site at N58 and had a slower off-rate from PD-1 versus nivolumab or pembrolizumab. Four hundred sixty-five patients were analyzed for irAEs. Fifteen (3.2%) patients had grade 3 or above irAEs. No death from irAEs was reported.ConclusionsIgG1 backbone anti-PD1 antibody penpulimab has a good stability and reduced host cell protein residue, as well as potent binding to the antigen. Fc engineering has eliminated Fc-mediated effector functions of penpulimab including ADCC, ADCP and reduced ADCR, which may contribute to its more favorable safety profile.Clinical trial registrationwww.ClinicalTrials.gov, identifier: AK105-101: NCT03352531, AK105-201: NCT03722147, AK105-301: NCT03866980, AK105-202:NCT03866967, AK105-203: NCT04172571, AK105-204: NCT04172506.

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Engineered IgG1-Fc--one fragment to bind them all.

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Engineered IgG1-Fc--one fragment to bind them all.

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