NM_000186.4(CFH):c.2596+1G>C

For CFH c.2596+1G>C, a pathogenic splice donor variant that disrupts complement factor H production and leads to uncontrolled alternative complement pathway activation in the retina, anti-complement antibody and aptamer therapies represent the first FDA-approved treatments for geographic atrophy (GA), the advanced form of dry AMD. Pegcetacoplan (Syfovre, Apellis, anti-C3) and avacincaptad pegol (Izervay, Astellas, anti-C5) received FDA approval in 2023 for GA secondary to AMD. CFH loss-of-function variants like c.2596+1G>C cause constitutive overactivation of complement C3 convertase on retinal surfaces, leading to membrane attack complex deposition and progressive RPE/photoreceptor death. Complement inhibition directly addresses this pathogenic mechanism.

The OAKS and DERBY Phase 3 trials for pegcetacoplan (intravitreal anti-C3 cyclic peptide-PEG conjugate) demonstrated significant reduction in GA lesion growth rate vs sham: 22% reduction at 24 months (monthly dosing) in pooled analysis. The GATHER2 Phase 3 trial for avacincaptad pegol (intravitreal C5 inhibitor) showed 18% reduction in GA growth at 12 months. For patients with rare CFH loss-of-function variants (as opposed to the common Y402H risk polymorphism), the complement dysregulation is more severe and genetically defined, potentially predicting stronger treatment responses — though no variant-stratified efficacy data have been published. Genetic studies confirm that CFH loss-of-function (including splice-site variants) is associated with earlier onset, more aggressive GA progression, and higher complement biomarker levels (elevated Ba, C3a, C5a in aqueous humor). The anti-C5 antibody eculizumab has shown efficacy in CFH-related atypical hemolytic uremic syndrome, validating complement blockade for CFH deficiency in non-ocular tissues.

Current intravitreal complement inhibitors slow but do not halt or reverse GA progression — they reduce lesion growth rate by 18-22%, a statistically significant but clinically modest effect. Treatment requires monthly or every-other-month intravitreal injections indefinitely, creating a substantial treatment burden. Both pegcetacoplan and avacincaptad have been associated with increased risk of exudative (wet) AMD conversion and, rarely, retinal vasculitis/occlusive events. For a splice-site variant like c.2596+1G>C that produces systemic CFH deficiency, intravitreal therapy addresses only the ocular manifestation — these patients may also be at risk for CFH-related renal disease (C3 glomerulopathy, aHUS) requiring systemic complement inhibition. No variant-specific clinical trial data exist for rare CFH loss-of-function carriers; efficacy extrapolation from the broader AMD GA population (driven largely by common variants) remains uncertain. Gene therapy to restore CFH expression (AAV-CFH) is being explored preclinically but faces the challenge of sustained secretion of a large complement regulatory protein.

For CFH c.2596+1G>C, a pathogenic splice donor variant that disrupts the C-terminal complement regulatory domains of factor H, systemic or intravitreal anti-complement antibody and aptamer therapies offer a pharmacologically validated approach to slowing geographic atrophy progression. Avacincaptad pegol (Izervay, anti-C5 aptamer, FDA-approved 2023) and pegcetacoplan (Syfovre, anti-C3 antibody fragment, FDA-approved 2023) both reduce GA lesion growth by inhibiting the terminal complement pathway that is overactivated when CFH function is compromised.

CFH is the primary negative regulator of the alternative complement pathway. The c.2596+1G>C variant disrupts the canonical GT splice donor at the exon 17/intron 17 boundary of CFH, likely causing exon skipping or intron retention that truncates or destabilizes the SCR17-20 region responsible for surface complement regulation at Bruch membrane. Loss of CFH surface-binding capacity leads to uncontrolled C3 convertase activity, C3b deposition, membrane attack complex formation, and chronic inflammatory damage to RPE and choriocapillaris. Avacincaptad pegol (anti-C5 aptamer) showed 14% reduction in GA growth rate vs. sham at 12 months in the GATHER2 Phase 3 trial (NCT04435366). Pegcetacoplan (anti-C3) showed 22% reduction at 24 months in OAKS/DERBY Phase 3 trials (NCT03525600/NCT03525613). Both target complement downstream of the CFH deficiency point, making them mechanism-appropriate for CFH loss-of-function carriers. Earlier, lampalizumab (anti-factor D) failed its Phase 3 SPECTRI trial despite initially promising Phase 2 results in CFH risk-allele stratified patients.

Current anti-complement therapies slow but do not halt GA progression — the 14-22% growth rate reduction is modest, and existing vision loss is not reversed. Monthly or bimonthly intravitreal injections impose significant treatment burden and carry risks of endophthalmitis and retinal vasculitis (a noted adverse event with pegcetacoplan). Lampalizumab's Phase 3 failure despite promising Phase 2 biomarker data in CFI/CFH risk-allele carriers is a cautionary tale about complement pharmacogenomic stratification. The c.2596+1G>C variant is rare — trial populations were not enriched for high-impact CFH variants, so the specific benefit in this genotype is extrapolated from mechanism rather than direct evidence. Systemic complement inhibition is not appropriate for a local ocular disease due to infection risk, so intravitreal delivery constraints apply. Whether patients with monogenic CFH deficiency (like this splice variant) derive greater benefit than common-variant polygenic AMD patients has not been studied.