Pharmacological Characterization of a Novel Complement C3 Inhibitor Antibody Fragment

Area of Science:

• Ophthalmology
• Immunology
• Pharmacology

Background:

• Geographic atrophy (GA) is an irreversible cause of vision loss driven by the complement system.
• Novel therapeutic strategies targeting complement C3 are under investigation for GA treatment.
• This study characterizes a novel antibody fragment as a potential C3 inhibitor for GA.

Purpose of the Study:

• To evaluate the preclinical efficacy of a novel antibody fragment targeting complement C3.
• To assess the fragment's binding kinetics, C3 inhibition, and membrane permeation capabilities.
• To compare the fragment's performance against existing complement inhibitors.

Main Methods:

• Determined kinetic parameters for antibody fragment binding to C3 and its variants.
• Assessed inhibition of membrane attack complex (MAC) formation across complement pathways (CP, AP, LP).
• Investigated diffusion through Bruch's membrane (BrM) using in vitro models.

Main Results:

• The antibody fragment exhibited high picomolar affinity for C3 ligands, outperforming APL-1.
• Demonstrated dose-dependent inhibition of MAC formation across CP, AP, and LP pathways.
• Showed more efficient permeation through Bruch's membrane compared to a pegcetacoplan-similar molecule.

Conclusions:

• The antibody fragment is a potent and specific C3 inhibitor with broad complement pathway activity.
• Effective inhibition of MAC formation and superior BrM penetration suggest therapeutic potential for GA.
• The antibody fragment is currently under investigation in clinical trials for GA patients.