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Monthly Archive for: ‘August, 2013’
Genetic marker discovered for IOP
This article was published in Optometry, the UK Association of Optometrists professional journal.
It is of interest because in future it may be possible to better assess an individual’s risk of developing Glaucoma, perhaps even the severity of the disease if they do.
Research led by a Moorfields consultant has identified a common genetic marker for elevated intraocular pressure (IOP) – a major risk factor for the development and progressive worsening of glaucoma. It is of particular relevance as the only effective treatments for glaucoma work by lowering IOP.
The research was funded by the Wellcome Trust charitable foundation and could eventually enable the more effective identification of people at risk of raised IOP, as well as the development of new treatments for glaucoma, which affects 60 million people worldwide.
The findings of the five-year Genome Wide Association Study (GWAS) study were published in the journal Human Molecular Genetics. The £2m study was led by Moorfields consultant and ophthalmic surgeon Ananth Viswanathan, based on work by an international group of scientists and ophthalmologists from 37 different centres.
“The identification of the marker represents a significant milestone in the understanding of the genetic basis of glaucoma, the commonest cause of irreversible blindness worldwide,” said Mr Viswanathan.
“Our study identified that 99% of people will have the variant on at least one strand of their DNA, while 77% will have it on both. Using knowledge from epidemiology of the effect of IOP on glaucoma risk and risk of worsening, we estimated that each copy of the variant increases the risk of developing glaucoma by 8%, and in established glaucoma each copy gives an extra 6% likelihood of significant visual loss.
“The gene implicated is involved in a metabolic process known as vesicle handling. We know this is how the aqueous humour leaves the eye so the finding sheds light on the biological processes involved and may lead to new drug targets. Another group looking at glaucoma, not specifically IOP, also found genes elsewhere on the genome involved in vesicle handling, so an interesting picture is emerging.”
Avastin vs Lucentis
Recently studies have found that there is little difference in the success in treating Wet AMD between Lucentis (Ranibizumab) and Avastin (Bevacizumab). This may allow the heath services to save an awful lot of money, as Lucentis costs £741 per vial compared to £40 for Avastin. This could mean that many more people could be treated.
One of the recent most successful treatments for Exudative (Wet) Age Related Macular Degeneration (AMD), is a drug called Lucentis. This is an Anti VegF drug, which inhibits the growth of new blood vessels in the eye, which is the cause of Wet AMD. Injected directly into the Vitreous – the jelly at the back of the eye, it also causes the new vessels to become less leaky.
Lucentis was conceived because doctors tried Avastin, an anti cancer drug and another Anti VegF, to see if it would help Wet AMD, and found that it worked!
Avastin was “designed” on the basis that a tumour must acquire a blood supply to grow, and if this blood supply could be reduced or prevented, then the tumour would (hopefully) die, or at least it’s growth would be hampered. It has shown much success as an anti cancer drug. Because this “off label” use of a drug to treat another disease is not licenced, it leaves the treating doctor with increased risks of lawsuits should there be a problem- drugs are licenced to treat specific diseases.
Both Lucentis and Avastin were developed by Genentech, a California based company owned by Roche pharmaceutical. Avastin is marketed by Roche, but Lucentis is marketed in the UK and Ireland by Novartis.
Recently studies have found that there is little difference in the success in treating Wet AMD between Lucentis and Avastin. There was a slight suggestion in the increase in risk of serious complications, such as heart attacks in using Avastin, but as the dosage in treating the eye is so much less that when used as a cancer treatment, and there seem to be few worries in the Oncology reports, the study thinks that this may have been an incidental finding because of the relatively small trial size- as ever more research may be required there.
It does seem incredibly unfair that there is such a difference in prices between these two drugs, both manufactured by the same company, both similar in their method of working, but it is not as you might suspect down to company greed. It has been estimated that it can cost up to a $Billion* to get a drug licenced with the FDA in America, so the release of Lucentis required another FDA approval at another $Billion*, and the company has to be able to recoup this investment, before its patent expires. FDA approval only covers USA, so there will be similar costs in achieving European licencing. Some countries are much less regulated than ours- it seems that Doctors in India have been using Avastin to treat AMD for years.
Medical trials cost a lot of money, and most people would agree that they are necessary to ensure drug safety, the cost of Lucentis is the flip side.
The report can be viewed here– you may need to register or log in to view it, but registration is free.
