Phenotypic divergence of patient-derived iPSC-RPE by complement polygenic risk can be rescued by CTX114, a novel complement inhibitor for the treatment of age-related macular degeneration (AMD)

Abstract

Purpose : Human genetic studies have revealed strong associations between variants in complement pathway genes and AMD disease risk. To study the mechanisms of complement-driven AMD, we used complement pathway-specific polygenic risk scores (cPRS) to stratify AMD patient-derived induced pluripotent stem cell (iPSC) lines by their level of cPRS risk. We hypothesized that retinal pigmented epithelium derived from such lines (iPS-RPE) would provide a useful in vitro system to identify phenotypic differences between extremes of cPRS risk and differential responses to CTX114, a novel complement inhibitor for the treatment of age-related macular degeneration (AMD).

Methods : AMD patient-derived iPS lines of divergent cPRS (6 high, 6 low) were obtained from the NEI/NYSCF AMD iPSC panel. iPSCs were differentiated to RPE and qualified using immunohistochemical and transepithelial resistance (TEER) measurements. Basal levels (C3, C3a) and activities (FH-mediated ligand binding and cofactor activity) of secreted complement factors were measured by ELISA. Following challenge of iPSC-RPE with 10% normal human serum (NHS), MAC deposition in the sub-RPE space was measured by C5b-9 immunolabeling and quantified by high-content imaging.

Results : At baseline, high cPRS iPSC-RPE had lower TEER values (p<0.01), higher levels of apical C3 (p<0.01), and higher levels of apical C3a (p<0.05) than low cPRS iPSC-RPE. CFH from conditioned media of high cPRS iPSC-RPE had reduced binding to C3b (p<0.01) and MDA (p<0.01) and reduced CFI cofactor activity (p<0.01). When exposed to 10% NHS, high cPRS iPSC-RPE lines had increased levels of sub-RPE MAC deposition compared to low cPRS iPSC-RPE lines (p<0.01). Treatment with CTX114 reduced sub-RPE MAC deposition to different extents between high and low cPRS groups (p<0.01 CTX114 compared to control).

Conclusions : AMD patient iPSC-RPE lines of divergent cPRS show differential ability to regulate the complement pathway and differential response to a complement inhibitor. These findings support a precision medicine approach for AMD where patients at high risk for complement-driven disease can be identified by genetic screening as promising candidates for treatment with complement inhibitors such as CTX114.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.