As a long-term market leader and technique innovator in the field of antibody production and engineering, Creative Biolabs has earned great reputation from worldwide clients for our high-quality, cost-effective services in the past decade. Recently, we have successfully set up a novel assay system to better characterize the functional features of therapeutic antibody Fc regions, particularly FcRn binding interactions.
Antibody Fc constant regions, although not participating in target-binding, can contribute to many biological and pharmacological activities of therapeutic antibodies. Fc-FcγR complex plays a vital part in eliciting cytotoxicity by mediating ADCC and ADCP. On the other hand, Fc domains can also bind with FcRns, inducing prolonged or decreased in vivo half-life, which directly determines the effective serum concentration.
Fig 1. FcRn mediates the perinatal transfer of IgG. (Roopenian DC, Akilesh S. 2007)
Neonatal Fc-receptor (FcRn), is an MHC-I-like heterodimer that widely expresses on the surface of endothelial cells, macrophages, monocyte-derived dendritic cells. It can internalize and release serum components, i.e. antibodies and albumins, in a pH-dependent manner. FcRns can bind and intake serum antibodies in acidic pH (6.0) via pinocytosis, while dissociate and release in physiological pH (7.2) after recycling. As a result, antibodies can be protected from lysosomal degradation, leading to enhanced in vivo stability and efficacy. FcRn binding constitutes a major consideration for in vivo pharmacokinetic analysis of antibody drugs, which can be beneficial for early screening of lead candidates with favorable PK behaviors. Hence, comprehensive profiling of FcRn binding is commonly required by regulatory agencies as an integral part of Fc assessment.
Based on our state-of-the-art technology and extensive experience in conducting antibody function assays, Creative Biolabs now provides our elegant FcRn binding assay platform for in vitro estimating and predicting PK performance of therapeutic antibodies. In addition to conventional ELISA and bead-based proximity formats, we strongly recommend our real-time, label-free measurement system using surface plasmon resonance (SPR, from Biacore) or bio-layer interferometry (BLI, Octet) techniques. In contrast to ELISA method, this platform exhibits obvious advantages including:
Case Study
Fig.2 Binding and fitting curves between sample-1 with FcRn at different concentrations. (Creative Biolabs)
Table.1 SPR result summary between sample-1 with FcRn. (Creative Biolabs)
| Method | Ligand | Capture Level (RU) | Analyte | Analyte Conc. | ka (1/Ms) | kd (1/s) | KD (M) | Rmax (RU) | Chi² (RU²) | Fit method |
| His Capture | Human FcRn | 54.4 | Sample-1 | 1.953-500 nM | NA | NA | 1.20E-07 | 69.4 | 2.19 | Steady-state affinity |
We are capable of analyzing FcRn binding features of all four IgG subtypes using relevant positive controls and fine-quality reagents. An exhaustive report will be delivered by the end, and our seasoned scientists are also willing to apply our extensive expertise to help with data interpretation.
In addition, Creative Biolabs offers this exclusive Fc engineering service. Amino acid point mutagenesis will be employed within the FcRn binding site of Fc domain, seeking for a higher binding rate (pH 6.0), and a lower dissociation rate (pH 7.2). This strategy to achieve prolonged in vivo half-life can help to enable more appropriate clinical dosing. Our versatile, flexible and highly sensitive FcRn binding evaluation platform will greatly facilitate the selection of potent candidates in the early discovery phase, thereby ensure higher success rate in the later stage. For more detailed information, please feel free to contact us or directly sent us an inquiry.
References
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