Anti-VEGF Therapy: Five Molecules, One Target

Panretinal photocoagulation stopped a hundred thousand eyes from going blind long before anyone knew the molecule responsible.

That molecule turned out to be vascular endothelial growth factor, and blocking it directly has since become the single most consequential advance in modern retinal treatment.

Anti-VEGF therapy now underpins the management of the three commonest sight-threatening retinal vascular diseases: wet macular degeneration, diabetic retinopathy and retinal vein occlusion.

Five agents are now in clinical use, each with a different molecular target and a different durability profile.

Choosing between them, and choosing how often to inject, has become one of the highest-stakes decisions in outpatient ophthalmology.

What Is Anti-VEGF Therapy?

Anti-VEGF therapy is treatment that neutralises vascular endothelial growth factor, the principal signalling molecule driving pathological angiogenesis and vascular permeability in the retina.

The agents in current use are:

Bevacizumab – a full-length antibody developed for oncology and used off-label intravitreally; low cost and widely used where approved formulations are unaffordable
Ranibizumab – an antibody fragment specifically developed and licensed for intraocular use
Aflibercept – a fusion protein “trap” binding VEGF-A, VEGF-B and placental growth factor with high affinity, allowing longer dosing intervals
Brolucizumab – a small single-chain antibody fragment permitting high molar dosing, associated with a distinct intraocular inflammation risk
Faricimab – a bispecific antibody blocking both VEGF-A and angiopoietin-2, the newest agent and the first to target vessel stability as well as VEGF

The differences between these molecules are not academic – they translate directly into how long a given patient can safely go between injections.

Mechanism of Action

All disease processes treated with anti-VEGF share a common final pathway that the drug class interrupts.

Retinal ischaemia or RPE dysfunction upregulates VEGF secretion
VEGF binds its receptors on vascular endothelium, driving new vessel growth, breakdown of tight junctions and vascular leakage
Anti-VEGF agents bind circulating and tissue VEGF, preventing receptor activation
The result is reduced vascular permeability, regression of much of the abnormal neovascular complex, and resolution of oedema
Angiopoietin-2, blocked additionally by faricimab, independently destabilises vessels and amplifies VEGF’s effects – blocking both pathways together produces more durable vessel stabilisation than blocking VEGF alone

Suppression, not cure, is the operative word – VEGF drive typically returns once drug levels fall, which is the basis for ongoing treatment.

Indications

Established

Neovascular age-related macular degeneration
Diabetic macular oedema
Macular oedema secondary to branch and central retinal vein occlusion
Myopic choroidal neovascularisation

Expanding

Proliferative diabetic retinopathy, as an adjunct or alternative to panretinal photocoagulation in selected patients
Retinopathy of prematurity, now a guideline-supported option alongside laser in appropriate infants
Neovascular glaucoma, used to regress iris and angle neovascularisation before or alongside definitive glaucoma treatment

The expansion into proliferative diabetic retinopathy is a genuine shift from laser as the default – it is not simply a rescue therapy any more.

Clinical Evidence

ANCHOR and MARINA established ranibizumab’s superiority over prior standard care in neovascular AMD
VIEW 1 and VIEW 2 established aflibercept’s non-inferiority to ranibizumab with a longer dosing interval
Protocol T, run by the DRCR Retina Network, directly compared aflibercept, bevacizumab and ranibizumab in diabetic macular oedema and found aflibercept had an advantage in eyes with worse baseline vision
TENAYA and LUCERNE demonstrated faricimab could match aflibercept’s efficacy with substantially extended treatment intervals in many patients
CATT and IVAN found bevacizumab broadly comparable to ranibizumab in AMD, supporting its continued off-label use where cost is a barrier

Protocol T remains particularly influential because it was designed and funded independently of any single manufacturer, giving its head-to-head comparisons unusual credibility.

Treatment Strategy

Loading and Maintenance

Most regimens begin with monthly loading injections – typically three to five – to achieve maximal anatomical control before spacing treatment out
Maintenance then follows a fixed, PRN or treat-and-extend schedule depending on the disease and the agent’s durability

Selecting an Agent

Durability needs – a patient struggling to attend frequent visits benefits from a longer-acting agent
Disease severity – Protocol T’s subgroup findings still inform first-line choice in diabetic macular oedema with poor baseline vision
Cost and access – bevacizumab remains the dominant choice in many health systems purely on cost grounds, with comparable efficacy
Inflammation risk – brolucizumab’s association with retinal vasculitis has narrowed its use in practice since post-marketing data emerged

No single agent is correct for every patient – the choice is a genuine clinical trade-off between durability, cost and individual risk profile.

Safety Considerations

Endophthalmitis remains the most feared acute complication of the injection procedure itself, not the drug
Intraocular inflammation, including retinal vasculitis, is a recognised class effect with a higher reported incidence for brolucizumab
Systemic arterial thromboembolic events are a theoretical concern from systemic VEGF suppression; large pooled analyses have not shown a clear excess risk, but caution is exercised in patients with recent stroke or myocardial infarction
Geographic atrophy progression with long-term anti-VEGF exposure has been reported in some cohort studies of AMD, though whether this reflects the drug or the natural history of treated eyes remains actively debated

The safety conversation with patients should distinguish clearly between injection-related risk, which is procedural, and drug-related risk, which is pharmacological – conflating the two undermines informed consent.

Prognosis

Anti-VEGF therapy has transformed the natural history of every disease it is used to treat.

Neovascular AMD, once reliably progressive to legal blindness, now stabilises or improves in the large majority of eyes treated promptly and consistently
Diabetic macular oedema shows sustained improvement in visual acuity with regular treatment, exceeding what laser alone achieved
Vein occlusion-related oedema responds well, though the underlying occlusion and ischaemic burden still shape the long-term ceiling on vision
Real-world outcomes consistently trail trial outcomes, and the gap is explained almost entirely by under-treatment relative to trial protocols

The technology has outpaced the delivery systems built to support it – the next gains in this field are as likely to come from better adherence and longer-acting agents as from a fundamentally new mechanism.

References

Wells JA, Glassman AR, Ayala AR, et al. Aflibercept, bevacizumab, or ranibizumab for diabetic macular edema (Protocol T). New England Journal of Medicine. 2015.
Heier JS, Khanani AM, Quezada Ruiz C, et al. Efficacy, durability, and safety of faricimab up to every 16 weeks: TENAYA and LUCERNE. The Lancet. 2022.
CATT Research Group. Ranibizumab and bevacizumab for neovascular age-related macular degeneration. New England Journal of Medicine. 2011.
Anti-VEGF Agents. EyeWiki, American Academy of Ophthalmology.
Anti-VEGF Therapy. StatPearls, NCBI Bookshelf.