SR Pharma subsidiary Atugen developed RTP-801i and later licensed it to Quark Biotech. The drug utilises a natural phenomenon called RNA interference (RNAi) to prevent a specific disease-related gene from functioning. The gene in question here is REDD-1 and is linked to the progression of wet Age-related Macular Degeneration (AMD) where aberrant blood vessels beneath the retina leak blood and fluid into the eye causing loss of vision. RNAi is a process in which short strands of RNA, called small interfering RNA (siRNA), block signals from a particular gene. This gene silencing prevents it from producing a protein and so doing its job. Since its discovery, many companies have started to develop siRNA therapies and now the world's largest pharma companies are beginning to take an interest. RTP-801i is licensed by Pfizer with Quark Biotech the main beneficiary. SR Pharma specialises in developing siRNA anti-cancer drugs and SR Pharma chairman Iain Ross, told DrugResearcher.com that he sees large license deals as a first step to vindication of siRNA. He said: "If RNAi can be shown to be delivered systemically, we will see a new drug class." He explained that, being based on natural molecules, RNAi drugs hold a number of advantages over traditional drugs, both small molecules and biopharmaceuticals. "RNAi drugs can remove years of screening and the drug candidates can get into the clinic very quickly," he continued. Not only does this save money, but it could also extend the patent life of the drug while it's actually on the market. The drugs also don't need to be stabilised like many other therapies based on RNA molecules. The interest from large pharma not only increases the incentive for new research but it also generates interest from other large companies that are keen not to miss out. "We are excited about the AMD clinical trial commencing as it marks the first clinical study with one of our AtuRNAi molecules," said Ross. "The fact that this is only the fourth clinical programme with siRNA therapeutics worldwide confirms SR Pharma's leading position in this young Nobel Prize winning technology." There are no marketed siRNA drugs as yet - indeed, RTP-801i is only the fourth to enter clinical trials. Sirna Therapeutics was the first company to take a siRNA drug into trials. It had two drug candidates in clinical development - one that also treated AMD - when Merck & Co recently bought it in a deal worth $1.1bn (€850m). Merck & Co has also, in the past, signed collaboration deals with SR Pharma and Alnylam Pharma. A third large pharmaceutical company that has taken an interest in siRNA drugs is Novartis. It owns a stake in Alnylam Pharma whose siRNA drug, ALN-RSV01, to treat respiratory syncytial virus is currently in Phase I trials. AMD is the leading cause of blindness in the developed world affecting about 15m Americans over the age of 50 alone. Current treatments only work in early AMD and include destroying the blood vessels using a laser or using drugs that prevent blood vessel growth. One such drug is Genentech's Lucentis (ranibizumab). The antibody fragment was approved in June 2006 and is administered via an injection directly into the eye. It works by inhibiting VEGF proteins, which play an important role in blood vessel growth and is also a target for several treatments designed to prevent cancer tumours from growing and spreading. Andrew Fire and Craig Mello first discovered that RNA could knockdown genes in 1998 and were recently awarded the Nobel Prize in Physiology or Medicine for their research. Ross also revealed that SR Pharma is "talking to a number of very large companies at the moment and I wouldn't be surprised if we are announcing our own license deal sometime this year." He also pointed out that it was interesting that the larger companies are showing interest in siRNA compounds that are still quite early in clinical development rather than wait for later, Phase II and III compounds.