(2016) Heavy and light chain pairing of bivalent quadroma and knobs-into-holes antibodies analyzed by UHR-ESI-QTOF mass spectrometry, mAbs, 8:1, 49-55, DOI: 10.1080/19420862.2015 To link to this article: https://doi.org/10. 1080/19420862.2015 Keywords: bispecific antibody, CrossMab, chain pairing, ESI-QTOF mass spectrometry, knobs-into-holes, quadromaAbbreviations: Ang2, angiopoietin-2; bsAbs, bispecific antibodies; ESI, electrospray ionization; GuA HCl, guanidine hydrochloride; HEK, human embryonic kidney; HC, heavy chain; IgG1, immunoglobulin G1; ISCID, ion source collision induced dissociation; KiH, knobs-into-holes; LC, light chain; MS, mass spectrometry; TCEP, tris(2-carboxyethyl)phosphine; UHR, ultrahigh-resolution; VEGF-A, vascular endothelial growth factor A; QTOF, quadrupole time-of-flightThe quadroma antibody represents the first attempt to produce a bispecific heterodimeric IgG antibody by somatic fusion of 2 hybridoma cells each expressing monoclonal antibodies with distinctive specificities. However, because of random heavy and light chain pairing, the desired functional bispecific antibody represents only a small fraction of the protein produced. Subsequently, the knobs-into-holes (KiH) approach was developed to enforce correct heavy chain heterodimerization. Assuming equimolar expression of 4 unmodified chains comprising 2 heavy and 2 light chains, the statistical distribution of all paired combinations can be calculated. With equimolar expression as the goal, we transfected HEK cells with 1:1:1:1 plasmid ratios and analyzed the protein A affinity-purified antibodies from the quadroma and KiH approaches qualitatively and quantitatively with regard to the estimated relative amounts of the products using electrospray quadrupole time-of-flight mass spectrometry. Our results show that all expected species are formed, and that, within the methodological limits, the species distribution in the mixtures corresponds approximately to the statistical distribution.