Development of enhanced complement regulators for the treatment of Geographic atrophy

Abstract

Purpose : Geographic atrophy (GA) is a complex multifactorial disease. Multiple studies indicate complement cascade overactivation as a key contributor to the onset and progression of GA. Complement activation is downregulated by a protease and associated cofactor proteins. The “recyclable” nature and domain modularity of these cofactor proteins make them promising targets for therapeutic development. Here, we present a novel class of potent complement inhibitors based on components from cofactor proteins Factor H (FH) and complement receptor 1 (CR1). These fusions are modular and can be combined with other therapeutic formats to generate multispecific drugs.

Methods : Novel cofactor proteins were designed by combining domains of FH and CR1. Binding affinity and biological activity were investigated using surface plasmon resonance (SPR), complement cleavage activity, and hemolysis assays for alternative and classical pathways. The modularity of the engineered cofactors was assessed by fusing them with an anti-VEGF Fab. The bispecific molecules were investigated for their affinities for C3b and VEGF-A165 using SPR, and inhibitory activities using hemolysis assay and VEGF cell reporter bioassay.

Results : The engineered cofactors exhibited enhanced binding to C3b and promoted cleavage of C3b by Factor I into iC3b and further downstream degradation products C3c and C3dg. Hemolysis assays showed these engineered cofactors were up to 140-fold more effective than native human FH in inhibiting the alternative pathway. These molecules also showed potent inhibitory activity for classical pathway. Fusion of these complement inhibitors to anti-VEGF Fab demonstrated engineered cofactors can be used as module to generate multispecific molecules. This bispecific exhibited tight binding to both C3b and VEGF-A165, and inhibitory activities were comparable to their respective monospecific moieties.

Conclusions : We have engineered potent complement inhibitors by combining domains of FH and CR1. The novel cofactor molecules are modular and can be integrated to other protein modules, such as antibody fragments to generate multispecific drugs.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.