Multispecific antibodies have the potential to activate or alter biological pathways in ways that are not easily achieved with monoclonal antibodies. Multispecific antibodies are able to cause high-order target clustering, conformational changes or act as ligand mimics by co-associating heterodimeric targets. Empirical testing is required to find the correct combination of epitopes, affinities and geometries that are able to produce the desired activity. B-Body™ fab arms are selected for diversity in epitope binding site and affinity. Invenra performs in-format high throughput discovery campaigns of 1,000 to 10,000 candidates using reporter-based assays or primary cell assays to identify the ideal combination of affinity, epitope, and B-Body™ format to achieve activity. Top candidates are optimized through protein engineering to maximize the potency and improve the developability profile.
Many signaling pathways are activated through high density clustering as a result of natural ligand binding to the receptor. Standard monoclonal, monospecific antibodies are only able to bind to two targets and are unable to form high density clusters without the additional binding of the Fc by immune effector cells or secondary antibodies. Multispecific antibodies binding to two different epitopes on the same receptor are able to form large networks or clusters that can efficiently activate the same signaling pathways without Fc-engagement. The identification of antibody geometries along with target epitopes that drive binding to two different receptors (trans binding) is necessary to maximize the level of agonism. The ClustR™ approach allows the high throughput empirical screening of combinations of epitopes, geometries, and affinities to identify candidates with the optimal activity level.
Signaling pathways can also be activated through trapping a receptor in an active conformation or forcing receptor heterodimerization in the absence of the natural ligand. Standard monoclonal, monospecific antibodies are only able to bind to a single epitope of the target and are less likely to achieve these activating conformations. Multispecific antibodies binding to two different epitopes on the same receptor or two different receptors have the advantage of being able to force novel conformations. The identification of antibody geometries along with target epitopes that results in activating conformations relies on the ability to screen larger combinations of binding partners in the final format in biologically relevant assays. ClustR™ uses Invenra’s B-Body™ platform to empirically screen of combinations of epitopes, geometries, and affinities in reporter-based or primary-cell assays to identify novel, first-in-class drug candidates.