The news raises the prospect of using siRNA as a viable treatment, initially for wet age-related macular degeneration (AMD) - a leading cause of blindness - but also any disease caused by inappropriate activity of specific genes. The ability to silence and regulate such genes selectively through siRNA is already being exploited in drug discovery and more recently in the development of siRNA-based therapeutics.
The siRNA, Cand5, is in Phase I clinical trials in patients with AMD: these are the first ever human clinical trials of an siRNA therapeutic.
Its developer, US based Acuity Pharmaceuticals has signed the agreement with Avecia Biotechnology for pharmaceutical grade supplies of the drug. Under the terms of the agreement, Avecia will supply Acuity with Cand5 through the clinical development process up to commercial launch of the drug. Financial details of the agreement were not disclosed.
Cand5's mechanism of action uses RNA interference (RNAi) technology to turn off genes that produce the growth factor vascular endothelial growth factor (VEGF), which is believed to be a primary cause of the excess leakage and blood vessel growth that lead to progressive blindness in patients with macular degeneration.
This is achieved by using short nucleic acid sequences that bind to and inactivate the machinery in the cell that leads to protein transcription. This is also known as gene silencing and its manner is similar to that achieved using antisense oligonucleotides. And this mechanism means it could also be of value in diabetic retinopathy (DR), another common cause of blindness.
Current treatments for wet AMD and DR are of limited efficacy and fail to halt disease progression in many patients. According to Acuity Pharmaceuticals, by 2010, the market for treatments for wet AMD and DR is forecast to grow to $10 billion (€7.7 billion).
Dale Pfost, CEO of Acuity said: "This is the first-ever manufacturing agreement for a pharmaceutical siRNA, and Avecia's expertise in the manufacture of clinical-grade oligonucleotides will be extremely valuable to Acuity's development program for Cand5."
Current treatments for wet AMD and DR are of limited efficacy and fail to halt disease progression in many patients. In the search for more effective treatments, researchers are targeting vascular endothelial growth factor (VEGF), which has been shown to be a key cause of the excess growth of blood vessels that results in loss of vision. By 2010, the market for treatments for wet AMD and DR is forecast to grow to $10 billion.
Michael McLean, president of DNA medicines at Avecia Biotechnology, added his endorsement to the collaboration saying the RNAi technology had tremendous therapeutic potential.
The wet form of AMD and DR are the number one and number two causes of irreversible vision loss in the developed world, and their incidence is growing rapidly. Advanced age is the main risk factor for wet AMD, and it is expected to become an increasingly common condition, as the population grows older.
An estimated 1.65 million Americans have wet AMD, and an estimated 30 million people have AMD worldwide. The incidence of diabetes is reaching epidemic proportions, with diabetic retinopathy estimated to affect 7 million Americans and more than 20 million people worldwide.