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Carrie Su, Fernando Correa, Hong Liang, Rachel Jacobson, Victor Perlroth, Long Pham; Characterization of Antibody Biopolymer Conjugate reveals superior biophysical properties compared to naked antibodies. Invest. Ophthalmol. Vis. Sci. 2020;61(7):4237.
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© ARVO (1962-2015); The Authors (2016-present)
Current therapies to treat retinal diseases are often intravitreally administered and require frequent injections due to short duration of action after each injection. To mitigate this, we developed an antibody biopolymer conjugate (ABC) platform, in which a large (800 kDa) hydrophilic and branched phosphorylcholine based biopolymer is site-specifically conjugated to an engineered antibody. Here, we present the biophysical characterization of KSI-301, a novel anti-VEGF ABC, which is currently in clinical testing for the treatment of retinal vascular diseases.
Intermolecular interactions of KSI-301 Conjugate or KSI-301 Protein (IgG only) were assessed by A2 (SEC-MALS) and KD (DLS) measurements at various pH and salt concentrations. The effect of the biopolymer on the IgG secondary and tertiary structure was evaluated by circular dichroism (CD) at the near and far-UV spectral regions. CD melt data was collected to evaluate KSI-301 Conjugate and KSI-301 Protein thermal stabilities. Lastly, the relative structural orientations of the antibody and biopolymer portions of the Conjugate were visualized by electron microscopy.
A2 and KD measurements showed biopolymer conjugation places the protein in a chemical environment where non-specific attractive interactions between protein molecules are largely reduced or removed. This effect is not affected by high salt concentrations or pH changes, which suggest biopolymer might prevent protein self-association mostly through steric stabilization. Electron microscope images displayed only one biopolymer per conjugate, which is visualized as a highly branched structure connected to the terminus of IgG. CD analysis showed the biopolymer does not affect the IgG secondary or tertiary structures despite physical proximity.
Biopolymer conjugation to antibody resulted in preferential changes in the protein colloidal properties while keeping the IgG structure and function unaffected. These results are consistent with our previous report that ABC conjugates are more stable compared to unconjugated naked antibody. These underlying biophysical properties may also contribute to the observed enhanced tissue penetration and improved ocular distribution seen for ABC. Altogether, our continuing studies demonstrate the ABC system is an important new platform with the potential to treat a wide array of retinal diseases.
This is a 2020 ARVO Annual Meeting abstract.
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