Emerging Treatments for Dry Age-Related Macular Degeneration

Dry age-related macular degeneration (AMD) is the leading cause of irreversible vision loss in adults over 60 in the United States, affecting an estimated 11 million people (National Eye Institute). Until 2023, there was no approved treatment for the condition's most destructive late stage — geographic atrophy — which erases central vision with quiet, inexorable precision. That changed. Two complement-pathway inhibitors reached FDA approval within months of each other, opening a treatment era that had been theorized for decades. The pipeline behind them is deep, diverse, and moving fast.

What Makes Dry AMD So Difficult to Treat

The disease progresses in two broad stages. Early and intermediate dry AMD involves the accumulation of drusen — fatty protein deposits — beneath the retina, alongside gradual deterioration of retinal pigment epithelium (RPE) cells. Geographic atrophy (GA) is the late stage, where discrete patches of RPE and photoreceptor cells die off permanently, creating blind spots that expand outward from — or toward — the fovea.

The challenge is biological complexity. Dry AMD involves complement dysregulation, lipid metabolism dysfunction, oxidative stress, and mitochondrial failure, all interacting across decades of slow damage. Hitting one pathway has proven insufficient in most trials. Hitting the right pathway at the right time is the current research frontier.

Complement Inhibitors: The First Approved Treatments for Geographic Atrophy

The complement system — a branch of innate immunity — has long been implicated in AMD pathology. Genome-wide association studies identified variants in complement factor H (CFH) and C3 as significant risk factors (NCBI/PMC). Blocking complement activation became the most clinically developed strategy.

Pegcetacoplan (Syfovre), a C3 inhibitor developed by Apellis Pharmaceuticals, received FDA approval in February 2023 — the first-ever approval for geographic atrophy. Administered as an intravitreal injection every 25 to 26 days, it reduced GA lesion growth by approximately 22% at 12 months in the OAKS and DERBY phase 3 trials (FDA).

Avacincaptad pegol (Izervay), a C5 inhibitor from Astellas (originally IVERIC bio), followed in August 2023. Monthly intravitreal injections reduced GA growth by 35.4% at 12 months in the GATHER1 trial (FDA). Both drugs slow the disease — they do not reverse existing damage, a distinction worth holding clearly in mind.

Both approvals carry a post-marketing requirement to further characterize rates of exudative conversion (conversion to wet AMD), which occurred at a higher-than-background rate in some trial participants.

Cell-Based and Gene Therapy Approaches

Replacing what has already been lost requires a different strategy entirely. Two categories have moved into clinical testing.

Stem cell-derived RPE transplantation attempts to replenish the retinal pigment epithelium that geographic atrophy destroys. The NEI's own Phase 1 trial, NCT01691261, used human embryonic stem cell-derived RPE cells on a synthetic scaffold delivered sub-retinally. Early safety data were encouraging, with no serious adverse immune events reported (ClinicalTrials.gov).

Gene therapy aims to turn the retina into its own pharmaceutical factory. Notably, ADVM-022, developed by Adverum Biotechnologies, delivers a vectorized construct encoding aflibercept — the same anti-VEGF protein used in wet AMD injections — via a single intravitreal injection. While this is primarily relevant to wet AMD, the platform concept has been adapted for complement-pathway gene suppression in dry AMD contexts as well.

GT005, developed by Gyroscope Therapeutics (now part of Novartis), targets complement factor I (CFI) through subretinal AAV gene delivery. Phase 2 results from the FOCUS trial showed biological activity in complement biomarkers, though definitive visual endpoints are still accruing (ClinicalTrials.gov).

Neuroprotection and Visual Cycle Modulation

A quieter but legitimate branch of AMD research targets photoreceptor survival directly, independent of complement.

Brimonidine tartrate (a drug already approved for glaucoma) was tested in a sustained-release intravitreal implant format for its neuroprotective properties. The Phase 2 results from Allergan's trial showed a signal in slower GA progression in a subset of patients, though Phase 3 results were inconclusive.

Visual cycle modulators attempt to reduce toxic bisretinoid accumulation — particularly A2E, a byproduct of the visual cycle that accumulates in RPE cells and contributes to oxidative damage. Fenretinide (ReVision Therapeutics) and emixustat hydrochloride (Acucela) both targeted this pathway in Phase 2 trials; neither produced statistically significant results on their primary endpoints at the studied doses, though mechanistic interest in the pathway remains.

Nutritional Interventions with Clinical Evidence

Not all interventions require a syringe. The Age-Related Eye Disease Study 2 (AREDS2), conducted by the National Eye Institute, established that a specific supplement formulation — 500 mg vitamin C, 400 IU vitamin E, 10 mg lutein, 2 mg zeaxanthin, 80 mg zinc, and 2 mg copper — reduces the risk of progression from intermediate to advanced AMD by approximately 25% over 5 years (NEI/AREDS2). This remains the standard of care for intermediate-stage patients and the benchmark against which new interventions are compared.

The Horizon

The 2023 approvals were not a finish line. They were the first meaningful marker in a long race. Sub-retinal stem cell delivery, complement gene suppression, mitochondria-targeted antioxidants, and sustained-release drug platforms are all in active clinical development. Geographic atrophy progresses at roughly 1.78 mm² per year on average (Sunness et al., Ophthalmology, 1999), and the margin between a slower and faster trajectory compounds meaningfully over a decade of living with the disease. The science is finally catching up to the biology.

References

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