Indeed, coexpression of two different light chain (LC) and heavy chains (HC) can result in up to nine unwanted chain pairings in addition to the desired BsIgG, as first demonstrated with hybrid hybridomas

Indeed, coexpression of two different light chain (LC) and heavy chains (HC) can result in up to nine unwanted chain pairings in addition to the desired BsIgG, as first demonstrated with hybrid hybridomas.4 For efficient production of BsIgG in single host cells, it is desirable to achieve selective pairing of cognate LC and HC and heterodimerization of the two different HC. The first efficient method for recombinant BsIgG production was developed in the 1990s using knobs-into-holes mutations to promote selective HC heterodimerization and a common LC to avoid mispairing of LC with non-cognate HC.5-7 Briefly, a steric clash or knob at the CH3/CH3 interface was created by replacing a small amino acid with a larger and bulkier residue. human IgG1, IgG2 and IgG4 thereby allowing the heavy chain isotype to be tailored for specific therapeutic applications. Additionally, a reverse chimeric bispecific IgG2a with humanized variable domains and mouse constant domains was generated for preclinical proof-of-concept studies in mice. Efficient production of a bispecific IgG in stably transfected mammalian (CHO) cells was shown. Individual clones with stable titer and bispecific IgG composition for >120?days were readily identified. Such long-term cell collection stability is needed for commercial manufacture of bispecific IgG. The single-cell bispecific IgG designs developed here may be broadly relevant to biotechnology research, including screening bispecific IgG panels, and to support clinical development. KEYWORDS: Bispecific antibody, bispecific IgG, orthogonal Fab engineering, single-cell production, stable CHO cell lines Abbreviations BiPbinding immunoglobulin proteinBsIgGbispecific IgGCDRcomplementarity-determining regionCHOChinese hamster ovaryECDextracellular domainEGFRepidermal growth factor receptorEMRextended mass rangeFabantigen-binding fragmentHCheavy chainHER2human epidermal growth factor receptor 2LClight chainMSmass spectrometryPBSphosphate-buffered salinePDBProtein Data BankREURosetta energy unitsRMSDroot mean square deviationVEGFvascular endothelial growth factor Introduction Bispecific antibodies are of growing interest as therapeutics, with more than 50 such molecules in clinical development for numerous indications.1,2 Bispecific antibodies can expand the functionality of traditional monospecific antibodies such as targeting effector cells to kill tumor cells, enhancing tissue specificity,3 or combining the antigen binding of two monoclonal antibodies in a single molecule to simultaneously silence two cellular signaling pathways. The bispecific IgG (BsIgG) format is one of the more attractive of the >60 different bispecific antibody types described to date2 as it provides the option for long serum half-life and effector functions. However, BsIgG are challenging to produce given their complex hetero-tetrameric composition. Indeed, coexpression of two different light chain (LC) and heavy chains (HC) can result in up to nine unwanted chain pairings in addition to the desired BsIgG, as first demonstrated with hybrid hybridomas.4 For efficient production of BsIgG in single host cells, it is desirable to achieve selective pairing of cognate LC and HC and heterodimerization of the two different HC. The first efficient method for recombinant BsIgG production was developed in the 1990s using knobs-into-holes mutations to promote selective HC heterodimerization and a common LC to avoid mispairing of LC with non-cognate HC.5-7 Briefly, a steric clash or knob at the CH3/CH3 interface was created by replacing a small amino acid with a larger and bulkier residue. Amino acid residues surrounding the knob mutation around the opposing side of the dimer interface were optimized using phage display to form a compatible indented surface or hole.5 The knobs-into-holes mutations favor HC heterodimerization over competing homodimerization. The common LC antibodies were identified from a human scFv phage display library with limited LC diversity.6,8 A limitation of this original method is that it constrains the choice of antibodies that can be used for making BsIgG. This limitation has been partially overcome by novel transgenic animal platforms9 and also new combinatorial Rabbit polyclonal to CDC25C libraries with a common LC to facilitate the discovery of suitable antibodies. In recent years, a plethora of creative solutions for recombinant production of BsIgG and related Benzocaine hydrochloride antibody molecules have been developed that overcome or avoid the HC and LC pairing problems.2 For example, several dual-cell BsIgG technologies have been developed in which each IgG arm of the BsIgG is separately expressed and purified followed by in vitro assembly into BsIgG.10-14 The separate production of each component IgG avoids LC mispairing, whereas selective HC heterodimerization is achieved through a variety of different HC engineering strategies.10-14 These dual-cell BsIgG technologies are now well established and have been used to produce several BsIgG for clinical development. In generating related BsIgG that share one antibody arm these dual-cell BsIgG technologies provide the flexibility to repurpose a stable cell line Benzocaine hydrochloride or one of the purified components. In addition, the analytical characterization of the final BsIgG is relatively simple as only two IgG chain-mispairing contaminants are expected, i.e., the two homodimeric parent IgG. Drawbacks of dual-cell IgG technologies include the relatively high cost and complexity of manufacturing. Also, these dual-cell technologies are not well-suited to generating large BsIgG panels for screening for optimal antibody pairs. Multiple engineering strategies have been established to express BsIgG and related Benzocaine hydrochloride Benzocaine hydrochloride bispecific antibodies in single host cells. Some of these single-cell technologies utilize.