Overview

Age-related macular degeneration (AMD) is the leading cause of irreversible blindness. Progression of AMD to geographic atrophy significantly threatens vision, leading to progressive and irreversible loss of visual function. There are currently no approved therapeutics commercially available for GA patients.

Mutations in numerous genes in the complement cascade result in increased risk of AMD such as Factor H, Factor I, C9, and C3. There is substantial interest in blocking complement activation in the eye by inhibiting C3, with clinical data from a Phase 2 C3 inhibitor (APL-2) significantly inhibiting the progression of GA, albeit with limitations in feasibility. Mosaic and Catalyst engineered a PEGylated long-acting protease, which eliminates C3 catalytically, improving upon efficacy and patient burden.

Method Highlights

Protein Engineering: CB 2782 was engineered in E. coli from a human serine protease to degrade human C3 into inactive fragments. A single unpaired cysteine was added to CB 2782 and modified with a 40 kDa linear PEG by maleimide coupling.

Functional Assays: Enzymatic activity and specificity of CB 2782 and PEG-CB 2782 were evaluated with peptide hydrolysis assays and human C3 cleavage. Inhibition of complement activation was evaluated in standard sheep red blood cell hemolysis assays.

PK/PD Studies: Pharmacokinetics and pharmacodynamics (C3 level) were evaluated in rabbit and African green monkey primate models. Vitreous humor was sampled at multiple time points up to sacrifice at 1, 14, and 28 days. Drug concentrations were determined by enzyme activity, while C3 levels were determined by ELISA.