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GS-101 is an antisense oligonucleotide (DNA strand) that inhibits the expression of scaffold protein Insulin Receptor Substrate 1 (IRS-1) in pro-angiogenic conditions. GS-101 has recently been associated with positive phase II findings published in the September 2009 “Ophthalmology” (Journal of the American Academy of Ophthalmology), indicating that GS-101 is an effective agent to inhibit and regress corneal neovascularisation.
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On 17 April 2007, Orphan designation (EU/3/07/445) was granted by the European Commission to Gene Signal for GS-101 for the prevention of Corneal Graft Rejection (Doc. Ref.: EMEA/COMP/108186/2007, 30th November 2007)
According to Regulation (EC No 141/2000 of 16 December 1999), the Committee for Orphan Medicinal Products (COMP) adopted on 8 March 2007 a positive opinion recommending the grant of the above-mentioned designation.
After transplantation of the cornea (the round transparent part of the eye, external to the iris), there is a risk that the transplant (graft) will not be accepted by the patient’s immune system, which would lead to a phenomenon called “rejection”.
The cornea does not have blood vessels, so it is usually difficult for white blood cells and antibodies (both mediators of rejection) to reach it and activate rejection mechanisms. For this reason, rejection tends to occur less frequently in corneal transplants compared to other organs that do have blood vessels, such as the kidney, but it is still a feared complication as it can lead to loss of vision in the affected eye. In some eye diseases, however, there can be formation of new blood vessels in the cornea, and this also may occur (or worsen) in the new transplanted cornea, thus allowing easier access for white blood cells and antibiotics, and an increased likelihood of rejection.
Currently, no satisfactory methods exist in the European Union that were authorised at the time of application, for the prevention of corneal graft rejection. However, eye drops containing corticosteroids (cortisone-like substances) are commonly prescribed after corneal transplantation to prevent rejection; other drugs that have been employed are cyclosporin and tacrolimus, both for the treatment and the prevention of corneal graft rejection.
What is the estimated number of patients at risk of developing the condition?
According to the information provided by the sponsor, the population of patients eligible for prevention of corneal graft rejection was estimated to be approximately 46,000 persons in the European Union.
This antisense oligonucleotide acts by blocking the production of a protein that is required for the formation and growth of new blood vessels. It does not act on already existing blood vessels. Since formation of new blood vessels in the cornea is believed to be one of the principal mechanisms by which the immune system may reject a corneal transplantation, the medicinal product is expected to reduce the likelihood of rejection itself.
