The engineering of bispecific antibodies that exhibit optimal affinity and functional activity presents a significant scientific challenge. To tackle this, investigators employ an assortment of protein assay techniques, such as label-free interaction methodologies, which offer rapidity and convenience for the evaluation of extensive sample sets. These assays yield intricate data pertaining to the affinity towards target antigens and Fc-receptors, instrumental in predicting cellular test outcomes. Nevertheless, the fine-tuning of affinity is of paramount importance to mitigate potential adverse effects while maintaining efficient obstruction of ligand–receptor interactions. In this research, biolayer interferometry (BLI) was utilized to probe the functional characteristics of bispecific antibodies targeting cluster of differentiation 47 (CD47) and programmed death-ligand 1 (PD-L1) antigens, encompassing affinity, concurrent binding to two disparate antigens, and the inhibition of ligand–receptor interactions. The findings derived from BLI were juxtaposed with data from in vitro signal regulatory protein-α (SIRP-α)/CD47 blockade reporter bioassays for two leading bispecific antibody candidates, each demonstrating distinct affinity to CD47.

The interaction of therapeutic antibodies with Fc receptors is an important property that is actively modified to improve pharmacokinetic profiles and optimize antibody-dependent mechanisms of action. Various modifications of the Fc and hinge regions of antibodies, leading to a change in affinity with various Fc receptors, are widely covered in the literature. However, data on changes in antibody and Fc receptor interactions after antibody binding to the target antigen are poorly covered in the literature. In this work, we demonstrated a change in the affinity of the interaction of antibodies with Fc receptors after binding to the target antigen via the method of biolayer interferometry. An interesting result was a significant weakening of the interaction of FcRn and FcγRIIIa with some of the antibodies when the latter bound to the target antigen, which suggests the importance of this effect for the pharmacokinetic properties and effector mechanisms of action necessary in the treatment of oncological diseases. The sensor-based biolayer interferometry methods presented in this paper allow antibody screening to be performed to detect the effects of the reduced affinity of interactions with Fc receptors, and can be a useful tool in the early development of therapeutic antibodies.