Bispecific antibodies (bsAbs) represent a fast-growing class of molecules offering new therapeutic perspectives. Their development is still hampered by the difficulty to produce such complex molecules composed of multiple
polypeptide chains. Indeed, in contrast to classical IgG antibodies, which are produced under an homodimeric format, bsAbs offer a wide variety of heterodimeric formats. The difficulty to produce them is even higher when
by-side homodimer products cannot be distinguished with the heterodimer product of interest based on molecular weight sizing. If forced pairing by introducing point mutations such as knob into holes has been the focus of many efforts these last decades to maximize heterodimer formation, identification of clonal cell lines expressing high levels of heterodimer forms of bsAb has remained challenging. Currently, bsAbs are mainly produced in vitro after assembling half antibodies produced separately or in vivo from co-culture of two cell lines producing each half antibody. Therefore, producing bsAb in a single-cell system, whatever the format, turns out to be the most attractive
By use of independent proprietary vectors, each harboring a different polypeptide chain from a bsAb model, chain-to-chain ratios could be controlled at the transfection level. Early screening of stable pools by microcapillary electrophoresis allowed to rapidly distinguish the different hetero- versus homodimeric populations. High-expressing clonal cell lines were then evaluated for their productivity using fed-batch cultures. Characterization of the final purified product was assessed by SEC HPLC analytical platform at Selexis.