The Use of a GroEL-BLI Biosensor to Rapidly Assess Preaggregate Populations for Antibody Solutions Exhibiting...

An automated method using biotinylated GroEL-streptavidin biosensors with biolayer interferometry (GroEL-BLI) was evaluated to detect the formation of transiently formed, preaggregate species in various pharmaceutically relevant monoclonal antibody (mAb) samples. The relative aggregation propensity of various IgG1 and IgG4 mAbs was rank ordered using the GroEL-BLI biosensor method, and the least stable IgG4 mAb was subjected to different stresses including elevated temperatures, acidic pH, and addition of guanidine HCl. The GroEL-BLI biosensor detects mAb preaggregate formation mostly before, or sometimes concomitantly with, observing soluble aggregates and subvisible particles using size-exclusion chromatography and microflow imaging, respectively. A relatively unstable bispecific antibody (Bis-3) was shown to bind the GroEL biosensor even at low temperatures (25^°C). During thermal stress (50°C, 1 h), increased Bis-3 binding to GroEL-biosensors was observed prior to aggregation by size-exclusion chromatography or microflow imaging. Transmission electron microscopy analysis of Bis-3 preaggregate GroEL complexes revealed, in some cases, potential hydrophobic interaction sites between the Fc domain of the Bis-3 and GroEL protein. The automated BLI method not only enables detection of transiently formed preaggregate species that initiate protein aggregation pathways but also permits rapid mAb formulation stability assessments at low volumes and low protein concentrations.