Anti-VEGF Treatments for Wet AMD

Ophthalmic Peptides

95% vision stabilized

In the MARINA trial, 95% of patients receiving monthly ranibizumab injections maintained or improved vision at 12 months, compared to 62% of controls.

Rosenfeld et al., NEJM, 2006

Rosenfeld et al., NEJM, 2006

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Wet age-related macular degeneration (AMD) destroys central vision by growing abnormal blood vessels underneath the retina. These vessels leak fluid and blood into the macula, the region responsible for sharp, detailed vision used for reading, driving, and recognizing faces. Before 2004, there was no effective treatment. The introduction of anti-VEGF (vascular endothelial growth factor) therapies transformed wet AMD from a disease of inevitable blindness into one where vision can be stabilized in over 90% of patients and improved in 30-40%. Every approved anti-VEGF agent works by the same principle: blocking the peptide growth factor VEGF from binding its receptors on retinal endothelial cells, preventing the abnormal blood vessel growth (choroidal neovascularization) that causes vision loss. For the history of the first anti-VEGF peptide aptamer approved for the eye, see our pillar article on Pegaptanib: The First Anti-VEGF Peptide Approved for Eyes.

VEGF: The Peptide Growth Factor Behind Wet AMD

Vascular endothelial growth factor A (VEGF-A) is a homodimeric glycoprotein produced by retinal pigment epithelium (RPE) cells, Muller glial cells, and ganglion cells in the retina. In the healthy eye, VEGF maintains the fenestrated endothelium of the choriocapillaris and supports retinal neuron survival. In wet AMD, VEGF production becomes pathologically elevated in response to hypoxia, oxidative stress, and inflammatory signaling beneath the RPE.

VEGF-A exists in multiple splice variants. VEGF-165 is the predominant isoform in the eye and the primary driver of choroidal neovascularization. It binds to VEGF receptor 1 (VEGFR-1/Flt-1) and VEGF receptor 2 (VEGFR-2/KDR) on endothelial cells, triggering proliferation, migration, and survival signals through the PI3K/Akt and MAPK/ERK pathways. VEGFR-2 mediates the majority of VEGF's angiogenic effects.

The result in wet AMD is choroidal neovascularization (CNV): abnormal blood vessels sprout from the choroidal vasculature, penetrate Bruch's membrane, and grow into the sub-RPE or subretinal space. These immature vessels are structurally abnormal, leaking plasma proteins and blood into the retina. The fluid accumulation distorts the macula, and repeated hemorrhages lead to fibrotic scarring and permanent photoreceptor loss.

The Anti-VEGF Revolution: From Pegaptanib to Faricimab

Pegaptanib (Macugen, 2004)

Pegaptanib was the first anti-VEGF agent approved for wet AMD. It is a pegylated RNA aptamer (a synthetic oligonucleotide that folds into a three-dimensional shape) that binds specifically to the VEGF-165 isoform. Pegaptanib reduced the rate of vision loss compared to sham injection but did not improve vision in most patients. It was rapidly superseded by ranibizumab, which blocks all VEGF-A isoforms and produces substantially better visual outcomes. Pegaptanib's legacy is proof-of-concept: blocking VEGF in the eye is safe and effective. For a detailed exploration, see Pegaptanib: The First Anti-VEGF Peptide Approved for Eyes.

Ranibizumab (Lucentis, 2006)

Ranibizumab is a 48 kDa humanized monoclonal antibody fragment (Fab) that binds and neutralizes all isoforms of VEGF-A. The MARINA trial (2006) established it as the standard of care: 95% of patients receiving monthly injections maintained or improved vision at 12 months, and 34% gained 15 or more letters (three lines) of visual acuity. This represented the first treatment in ophthalmology history that reliably improved vision in wet AMD rather than merely slowing its decline.

Ranibizumab requires monthly intravitreal injections for optimal results. The treatment burden is substantial: each injection requires an office visit, topical anesthesia, and a needle through the pars plana into the vitreous cavity. Treatment is indefinite in most patients.

Bevacizumab (Avastin, Off-Label)

Bevacizumab is a full-length monoclonal antibody (149 kDa) originally approved for metastatic colorectal cancer. It binds all VEGF-A isoforms. Ophthalmologists began using it off-label for wet AMD because it costs approximately $50 per injection compared to $1,850 for ranibizumab. The CATT trial (2011) demonstrated that bevacizumab was non-inferior to ranibizumab for visual acuity outcomes at one and two years, though with a slightly higher rate of systemic adverse events. Bevacizumab remains the most widely used anti-VEGF agent for wet AMD globally due to its cost advantage.

Aflibercept (Eylea, 2011)

Aflibercept is a 115 kDa recombinant fusion protein comprising the VEGF-binding domains of VEGFR-1 and VEGFR-2 fused to the Fc portion of human IgG1. This "VEGF trap" design gives it higher VEGF-binding affinity than ranibizumab and also binds placental growth factor (PlGF), which ranibizumab does not. The VIEW trials demonstrated that aflibercept dosed every 8 weeks was non-inferior to ranibizumab dosed monthly, reducing the injection burden by half. High-dose aflibercept (8 mg) approved in 2023 extends dosing intervals to 12-16 weeks in many patients.

Brolucizumab (Beovu, 2019)

Brolucizumab is a 26 kDa single-chain antibody fragment (scFv), the smallest anti-VEGF molecule approved for wet AMD. Its small size allows delivery of a higher molar concentration per injection. The HAWK and HARRIER trials showed non-inferiority to aflibercept with potential for extended dosing (every 12 weeks). However, post-marketing reports of retinal vasculitis and retinal vascular occlusion limited its adoption.

Faricimab (Vabysmo, 2022)

Faricimab is the first bispecific antibody approved for the eye. It simultaneously binds VEGF-A and angiopoietin-2 (Ang-2), targeting two distinct angiogenic pathways. Ang-2 destabilizes blood vessel walls and promotes vascular permeability independently of VEGF. By blocking both signals, faricimab addresses a limitation of VEGF-only blockade: some patients respond incompletely because Ang-2-driven vascular instability persists even when VEGF is fully suppressed. In the TENAYA and LUCERNE trials, faricimab achieved dosing intervals of 16 weeks in nearly 50% of patients.

Peptide-Based Approaches Beyond Anti-VEGF Antibodies

The approved anti-VEGF agents are antibodies or antibody fragments, not traditional peptides. However, several peptide-based strategies are being investigated for retinal vascular diseases.

PEDF Peptide Eye Drops

Pigment epithelium-derived factor (PEDF) is a 50 kDa glycoprotein with potent anti-angiogenic and neuroprotective properties in the retina. Liu and colleagues (2012) demonstrated that PEDF-derived peptide eye drops reduced retinal inflammation, cell death, and vascular leakage in a diabetic retinopathy model, raising the possibility of a non-invasive, topical peptide approach to retinal vascular disease.^[1] This is significant because current anti-VEGF therapies all require intravitreal injection; a topical peptide that penetrates to the retina would transform the treatment paradigm.

Neuroprotective Peptides

PACAP (pituitary adenylate cyclase-activating polypeptide) has demonstrated protective effects against retinal neurodegeneration in diabetic retinopathy models. Szabadfi and colleagues (2012) showed that PACAP protected retinal neurons from diabetes-induced damage through anti-apoptotic and anti-inflammatory mechanisms.^[2] While not directly targeting VEGF, neuroprotective peptides could complement anti-VEGF therapy by protecting the photoreceptors and retinal ganglion cells that anti-VEGF alone cannot rescue once damaged. Camelo and colleagues (2009) demonstrated that intravitreal injection of the neuropeptide CXCL12 (SDF-1) protected retinal ganglion cells from excitotoxic damage, further supporting the concept that peptides delivered to the vitreous cavity can produce neuroprotective effects beyond anti-angiogenesis.^[5] For the full evidence on PACAP's retinal effects, see PACAP: The Neuropeptide Protecting Against Retinal Damage.

GHRH (growth hormone-releasing hormone) agonists showed unexpected protective effects in early experimental diabetic retinopathy. Thounaojam and colleagues (2017) found that GHRH agonists reduced retinal inflammation and vascular pathology through mechanisms independent of growth hormone, suggesting direct peptide-receptor interactions in retinal tissue.^[3]

Endostatin: The Anti-Angiogenic Peptide

Endostatin, a 20 kDa C-terminal fragment of collagen XVIII, is one of the most potent endogenous anti-angiogenic peptides. It inhibits endothelial cell proliferation and migration and has been studied in retinal neovascularization models. While endostatin has not entered clinical trials for AMD specifically, it represents the class of endogenous peptide angiogenesis inhibitors that the body uses to counterbalance VEGF signaling. For a full analysis, see Endostatin: The Anti-Angiogenic Peptide That Starves Tumors.

The Treatment Burden Problem

The primary limitation of current anti-VEGF therapy is not efficacy but the treatment burden. Monthly or bimonthly intravitreal injections indefinitely represent a substantial commitment for patients, many of whom are elderly. Each injection carries a small but cumulative risk of endophthalmitis (infection inside the eye), retinal detachment, and elevated intraocular pressure.

Real-world visual outcomes are consistently worse than clinical trial results, primarily because patients in clinical practice receive fewer injections than the protocol-specified regimen. The gap between clinical trial and real-world outcomes is a treatment adherence problem driven by the injection burden.

This has motivated two parallel development strategies. First, engineering longer-acting anti-VEGF molecules that require less frequent injection: high-dose aflibercept (8 mg) extends to 12-16 weeks, and the port delivery system (a surgically implanted reservoir that continuously releases ranibizumab) extends to 6 months between refills. Second, developing non-injection delivery routes: PEDF peptide eye drops and gene therapy approaches that enable the eye to produce its own anti-VEGF protein indefinitely after a single treatment.^[1]

For the broader pipeline of peptide therapies targeting eye diseases beyond AMD, see Peptide Therapies for Age-Related Macular Degeneration: What's Available. For diabetic retinal disease specifically, see Peptide Therapies for Diabetic Eye Disease.

GLP-1 Agonists and Retinopathy Risk

An unexpected intersection between peptide pharmacology and retinal disease emerged from GLP-1 receptor agonist trials. Semaglutide was associated with a higher incidence of diabetic retinopathy complications compared to placebo in the SUSTAIN 6 trial. Peter and Bain (2020) reviewed the evidence and concluded the risk appears to be related to the speed of glycemic improvement rather than a direct toxic effect: rapid blood sugar lowering can transiently worsen diabetic retinopathy regardless of the drug used.^[4] This finding is relevant because many AMD patients also have diabetes, and their ophthalmologists and endocrinologists must coordinate care across both peptide-based treatment domains.

Limitations and Ongoing Challenges

Anti-VEGF therapy has transformed wet AMD treatment but has clear limitations. Approximately 10-15% of patients are "non-responders" who show minimal improvement despite regular injections, likely due to VEGF-independent angiogenic pathways. Faricimab's dual VEGF/Ang-2 blockade addresses one such pathway, but others (PDGF, FGF, SDF-1) remain unblocked. Long-term studies show that retinal atrophy (geographic atrophy) develops in 20-30% of eyes receiving chronic anti-VEGF therapy, raising questions about whether prolonged VEGF suppression harms the normal retina.

The neuropeptide approach (PACAP, PEDF, GHRH agonists) remains preclinical. The challenge of delivering therapeutic peptide concentrations to the retina through topical or systemic routes is substantial given the blood-retinal barrier. Intravitreal peptide injection is feasible but offers no advantage over existing anti-VEGF antibodies unless the peptide provides a mechanistically distinct benefit (neuroprotection, longer duration, or combination effects).

The Bottom Line

Anti-VEGF therapies block the peptide growth factor VEGF-A from driving abnormal blood vessel growth in wet AMD, stabilizing vision in over 90% of patients. Five agents are approved, progressing from the VEGF-165-selective aptamer pegaptanib to the bispecific antibody faricimab that simultaneously targets VEGF-A and Ang-2. The treatment burden of repeated intravitreal injections remains the primary limitation. Peptide-based approaches including PEDF eye drops, neuroprotective peptides (PACAP, GHRH agonists), and endogenous anti-angiogenic peptides (endostatin) represent potential complements or alternatives to antibody-based therapy, though all remain preclinical for AMD.

Frequently Asked Questions

What is anti-VEGF treatment for macular degeneration?

Anti-VEGF treatment involves injecting a drug directly into the eye that blocks vascular endothelial growth factor (VEGF), a peptide growth factor that drives abnormal blood vessel growth underneath the retina in wet AMD. By neutralizing VEGF, these drugs stop new vessel growth and reduce fluid leakage, stabilizing or improving vision. Five agents are currently approved: ranibizumab, aflibercept, bevacizumab (off-label), brolucizumab, and faricimab.

How often do you need anti-VEGF injections for wet AMD?

Injection frequency depends on the agent and individual response. Ranibizumab was originally given monthly. Aflibercept can be given every 8 weeks after initial loading doses, and high-dose aflibercept extends to 12-16 weeks. Faricimab achieves 16-week intervals in nearly 50% of patients. Treatment is typically indefinite; stopping injections usually leads to recurrence of fluid and vision loss.

What is the difference between ranibizumab and aflibercept?

Ranibizumab is an antibody fragment (48 kDa) that blocks VEGF-A. Aflibercept is a larger fusion protein (115 kDa) that blocks VEGF-A, VEGF-B, and placental growth factor with higher binding affinity. Clinical trials show equivalent visual outcomes, but aflibercept can be dosed less frequently (every 8 weeks vs monthly). Aflibercept is the more commonly used agent in current practice.

Are there peptide eye drops for macular degeneration?

Not yet approved, but research is active. PEDF (pigment epithelium-derived factor) peptide eye drops reduced retinal inflammation and vascular leakage in diabetic retinopathy animal models (Liu et al., 2012). A topical peptide that reaches the retina would eliminate the need for intravitreal injections, but delivering therapeutic concentrations through the eye's surface barriers remains a major challenge.

Why do some patients not respond to anti-VEGF injections?

About 10-15% of wet AMD patients show minimal improvement despite regular anti-VEGF therapy. This likely reflects VEGF-independent angiogenic pathways driving their disease. Angiopoietin-2 (Ang-2), platelet-derived growth factor (PDGF), and fibroblast growth factor (FGF) can all promote abnormal vessel growth independently of VEGF. Faricimab addresses the Ang-2 pathway; drugs targeting other pathways are in development.

Can GLP-1 drugs affect your eyes?

Semaglutide was associated with increased diabetic retinopathy complications in the SUSTAIN 6 trial. The risk appears related to the speed of blood sugar improvement rather than a direct drug effect on the retina; rapid glycemic correction can transiently worsen diabetic retinopathy regardless of the medication used. Patients with pre-existing diabetic retinopathy starting GLP-1 therapy should have ophthalmological monitoring (Peter and Bain, 2020).