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Amy Duguay, Wayne To, Jonathan Zhang, hong liang, D. Victor Perlroth, carrie Su; Superior stability of a class of novel antibody biopolymer conjugates for the treatment of retinal diseases. Invest. Ophthalmol. Vis. Sci. 2018;59(9):212. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
One drawback to current retinal protein therapeutics is the need for frequent intravitreal injections, which results in low patient compliance, thus disease progression. We designed a high molecular weight (MW) branched hydrophilic phosphorylcholine based biopolymer (OG1802) and covalently conjugated it to protein therapeutics to extend ocular half-life and decrease need for frequent injections. To prolong dosing intervals, the therapeutic must also be stable at physiological conditions during the interval to maintain efficacy. Experiments were designed to test bioconjugate stability: baseline purity; stability in formulation; stability in use; and accelerated stability.
Two bioconjugates, KSI301, an anti-VEGF Ab conjugated to biopolymer OG1802, and OG1448, an anti-VEGF anti-PDGF dual inhibitor fusion protein conjugated to the biopolymer OG1802, were tested. Protein not conjugated to biopolymer was used as a comparator. Bioconjugates were first tested for baseline purity and characterized by SDS-PAGE, IEX, SEC-MALS, and ELISA. The same tests were used for individual stability conditions and compared to a sample kept frozen at -80°C. For accelerated stability studies, high temp (65°C), 1% H2O2, high pH (8.5), and repeat freeze-thaws were used to force degradation. For in use stability, bioconjugate was tested in vitreous humor samples.
Baseline purity and potency for both bioconjugates were similar to unconjugated Ab controls. For OG1448, stability in formulation was carried out for one yr at 2-8°and 25°C, showing no change at 2-8°C, and no change at 25°C up to 6mos, with an increase in MW after 12mos, when compared to a frozen control. KSI301 in formulation stability was carried out for 6mos at both 2-8°C and 25°C, with no change. Most notably, after 24hrs at 65°C, KSI301 maintained solubility with greater than 50% of the protein non-aggregated and potent, as compared to the Ab-alone control, which became a solid precipitate.
Bioconjugates show improved stability over unconjugated proteins and are expected to have favorable stability profiles as compared to current commercially available intravitreal protein therapeutics. It's possible that the biopolymer component helps to maintain bioconjugate stability by acting as a colloidal system as defined by particles remaining suspended in solution at equilibrium, making the protein less prone to aggregation.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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