Exploiting light chains for the scalable generation and platform purification of native human bispecific IgG.

Bispecific antibodies enable unique therapeutic approaches but it remains a challenge to produce them at the industrial scale, and the modifications introduced to achieve bispecificity often have an impact on stability and risk of immunogenicity. Here we describe a fully human bispecific IgG devoid of any modification, which can be produced at the industrial scale, using a platform process. This format, referred to as a κλ-body, is assembled by co-expressing one heavy chain and two different light chains, one κ and one λ. Using ten different targets, we demonstrate that light chains can play a dominant role in mediating specificity and high affinity. The κλ-bodies support multiple modes of action, and their stability and pharmacokinetic properties are indistinguishable from therapeutic antibodies. Thus, the κλ-body represents a unique, fully human format that exploits light-chain variable domains for antigen binding and light-chain constant domains for robust downstream processing, to realize the potential of bispecific antibodies.

Ion exchange-high-performance liquid chromatography (IEX-HPLC).

The ion exchange-high-performance liquid chromatography is a high-throughput analytical method that allows to determine the charge profile of purified antibodies. Here, we describe the preparation of the samples, chromatographic conditions to be used (buffer preparation, salt gradient, quantity injected, flow rate, run time, column suitability, etc.), validity of the analysis, and integration of the chromatogram in order to calculate the proportion of the different isoforms.

Size exclusion-high-performance liquid chromatography (SEC-HPLC).

The size exclusion-high-performance liquid chromatography is a high-throughput analytical method, through isocratic condition, that allows to determine and quantify the level of aggregates and fragments of purified antibodies. Here, we describe the preparation of the samples, chromatographic conditions to be used (buffer preparation, quantity injected, flow rate, run time, column suitability, etc.), validity of the analysis, and integration of the chromatogram in order to calculate the proportion of the different components.

In vitro and in silico processes to identify differentially expressed proteins.

We present an integrated proteomics platform designed for performing differential analyses. Since reproducible results are essential for comparative studies, we explain how we improved reproducibility at every step of our laboratory processes, e.g. by taking advantage of the powerful laboratory information management system we developed. The differential capacity of our platform is validated by detecting known markers in a real sample and by a spiking experiment. We introduce an innovative two-dimensional (2-D) plot for displaying identification results combined with chromatographic data. This 2-D plot is very convenient for detecting differential proteins. We also adapt standard multivariate statistical techniques to show that peptide identification scores can be used for reliable and sensitive differential studies. The interest of the protein separation approach we generally apply is justified by numerous statistics, complemented by a comparison with a simple shotgun analysis performed on a small volume sample. By introducing an automatic integration step after mass spectrometry data identification, we are able to search numerous databases systematically, including the human genome and expressed sequence tags. Finally, we explain how rigorous data processing can be combined with the work of human experts to set high quality standards, and hence obtain reliable (false positive < 0.35%) and nonredundant protein identifications.