Are genetics the reason anti-VEGF treatments are often ineffective?

Anti-VEGF treatmentsTailored medicine, or personalised medicine, is seen by many to be the future of medical care, as it provides the best outcome for the individual patient.

For those suffering with age-related macular degeneration (AMD) there are a number of treatments available, but often they aren’t effective for every patient, meaning some may continue to lose vision whilst undergoing certain therapies.

This being the case, a number of research teams have looked into the efficacy of anti- vascular endothelial growth factor (anti-VEGF) treatments for wet AMD. Some of these studies have shown that genetic differences are the reason anti-VEGF drugs don’t always work.

Vascular endothelial growth factor (VEGF) protein  promotes the growth of blood vessels in the body. However, when the retina overproduces the VEGF protein new blood vessels grow behind the eye causing leakage, swelling and ultimately leading to eye conditions like wet AMD, diabetic maculopathy or macular oedema. Anti-VEGF injections are intended to reduce the growth of new blood vessels and do slow down vision loss in the majority of patients, but for some patients this treatment doesn’t work and their vision continues to deteriorate.

A meta-analysis in the British Journal of Ophthalmology by Mingxing Wu et al shows that people with the polymorphism (a genetic variation within a population) rs833061 were more likely to benefit from anti-VEGF treatment. In this study it was noted that this was particularly the case when the treatment was ranibizumab and if the patients were of Asian heritage.

In their research they found eight studies that investigated nine different genetic variations in VEGF-related genes and data on seven studies that related to ethnicity. Mingxing Wu’s team believes this is the first systematic review of a series of small studies into the efficacy of anti-VEGF.

They concluded that whilst some studies found a link between genetic variations and response to treatment there are limitations in the existing research. There needs to be more research into this whole area and environmental factors – like smoking – should also be studied. Further research could identify biomarkers that help to predict a patient’s response and provide personalised medicine and treatment plans.

Another study of note, published in December 2016 in the JCI, suggested that the immune system has a part to play in vision loss during anti-VEGF treatment. A genetic variation in a part of the immune system called the ‘complement system’ could interact with VEGF signalling during treatment. The study looked at the genetic variations in the retinal cells and observed that they led to ‘complement system dysregulation.’ Using anti-VEGF treatments increased this dysregulation, potentially showing that there is a link between the complement system and VEGF.

The research concludes that screening wet AMD patients for genetic variations in the complement system would identify those at risk of an adverse reaction to anti-VEGF therapies.

Both studies show promise for providing better and more sophisticated treatment for wet AMD, which is essential as cases of the condition affect more and more people. Personalising treatment or identifying biomarkers gives clinicians the chance to slow or halt vision loss and preserve sight for as long as possible.

The onset of wet AMD can be prevented, or at least significantly reduced, by capturing those at risk of developing the ‘dry’ or wet forms of the condition early. This can be done through a programme of screening and monitoring, complemented by lutein and zeaxanthin supplementation.

Want to learn more about AMD and its key modifiable risk factors? Download our free whitepaper: ‘Age-related macular degeneration – the case for early screening’.

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