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Rachel DeVay Jacobson, Dan Dang, William Ngo, Janine Lu, Amy Duguay, Ons Harrabi, Xiaojian Huang, hong liang, D. Victor Perlroth; Development and characterization of a prototype antibody biopolymer conjugate targeting the complement system. Invest. Ophthalmol. Vis. Sci. 2018;59(9):219.
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Several members of the complement alternative pathway (AP) have a strong genetic association with risk of developing dry AMD, and AP proteins have been found in the drusen of AMD patients. Thus, we developed a humanized, monoclonal antibody conjugated with a half-life extending biopolymer to neutralize Complement Factor D (CFD), the rate-limiting molecule of the AP. This molecule showcases our extended durability biologics platform to facilitate chronic intravitreal treatment of retinal diseases.
Antibody secreting single cells from rodents immunized with CFD were enriched by FACS and screened for CFD binding in microfluidic chambers. Antibodies were further selected based on (1) CFD binding, (2) inhibition of AP specific hemolysis, and (3) blocking of CFD mediated proteolysis of a synthetic substrate. A lead candidate was humanized and affinity matured. Crystal structure analysis of a CFD complex with the resulting antibody, OG1965, was performed. OG1965 was conjugated with a phosphorylcholine based biopolymer to form OG1970, which was then evaluated for its effects on CFD mediated cleavage of a small substrate and CFD target Complement Factor B (CFB), AP mediated hemolysis, and a cell based assay to measure terminal C5b-9 complex assembly.
OG1965:CFD structures revealed that our molecule recognizes a charged region on CFD that overlaps with the CFB epitope and is geographically distant from the catalytic site. SPR analyses indicated that OG1970 binds with single digit pM affinity and, consistent with it occupying the CFB binding site, blocks CFD interactions with C3bB. Moreover, OG1970 inhibited CFD mediated cleavage of both CFB and a small substrate that concurrently binds OG1970:CFD, indicating that OG9170 inhibits CFD enzymatic function. OG1970 treatment also greatly diminished AP mediated hemolysis and formation of the terminal complement complex. Importantly, OG1970 was found to be as effective as the C3 inhibitor Compstatin at preventing C5b-9 assembly.
The AP has been linked to risk and progression of AMD. We therefore discovered and engineered a high-affinity, humanized monoclonal antibody conjugated with a half-life extending biopolymer that potently neutralizes the AP. This novel platform may be a powerful tool to develop potent, extended durability intravitreal therapies for patients suffering from retinal diseases such as dry AMD.
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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