Sirna Granted Two UK Patents

The UK Patent Office recently granted Sirna Therapeutics two broad patents that cover short interfering RNAs, and the company has similar patents pending in the US Patent and Trademark Office and the European Patent Office.The patents lock up the use of short interfering RNAs (siRNAs) as therapeutics in the UK market, according to Sirna, but some say the company's intellectual property position is not that strong. Sirna Therapeutics, which is in the process of moving from Boulder, Colo., to San Francisco, changed its name from Ribozyme Pharmaceuticals in 2003 and has been publicly traded for several years. The company, which has roughly 80 employees, now specializes in developing RNA interference (RNAi)-based therapies for macular degeneration, hepatitis C, and Huntington disease, among other ailments. The company has filed for patents on hundreds of applications for siRNAs.The first patent (UK patent No. 2397818) broadly covers any chemical modifications that alter more than 20% of an siRNA used for therapeutic purposes. The second patent (UK patent No. 2396864) covers the use of any siRNA against the entire targeted vascular endothelial growth factor (VEGF) receptor gene. "In the UK, if you make a chemically modified siRNA, you're violating Sirna's IP," says Howard Robin, president and CEO of the company. "And that goes for companies that manufacture siRNAs also."What is at stake is a worldwide RNAi market with revenues expected to grow 31.5% a year, on average, reaching $328 million by 2010, up from an estimated $48 million in 2003, according to international consulting firm Frost & Sullivan. The validity of the patents and the way the courts handle any challenges has a potentially great effect on the RNAi field and Sirna's therapeutic competitors, which include Alnylam, Nucleonics, Benitec, and CytRx, as well as for siRNA manufacturers, such as Dharmacon, Ambion, and Qiagen."It is hard to imagine anyone could make an siRNA function as a therapeutic if you don't make an at least 20% chemical modification," says Robin.However, John Rossi, chairman of the division of microbiology at City of Hope's Beckman Research Institute in Duarte, Calif., and chairman of the scientific advisory board of Sirna's competitor, Benitec, disputes that idea. "I do not agree with Sirna that it would be difficult to make a therapeutic siRNA with less than 20% modified backbone/bases," he says.Rossi notes that he and CalTech researcher Mark Davis recently formed a start-up called Calando that will further develop a nanoparticle delivery vehicle that encapsulates unmodified siRNAs and effectively delivers them to cells in vivo.Others question if such broad patents will hold up in court. "These patent claims are not limited in any particular chemical modification, so on the one hand they would ostensibly cover any chemical modification as long as you're within those parameters that were mentioned," says Richard Warburg, a patent attorney and partner in the San Diego office of Foley & Lardner. "On the other hand, the broader [the claims] are, the more likely they are to bring in invalidating prior art."The VEGF patent specifically covers chemical modification at the 3' and 5' end, which may be optimal for therapeutic purposes. However, the patent could be challenged on grounds that it's an obvious modification. "Having modification at the 3' and 5' end is something that is well known in the art, but may never have been applied in this particular area," says Warburg. "Whenever you get into an obviousness issue, you can never tell when you're going to win or lose [a patent case]."Anna Hally, a biotech patent attorney with the UK-based law firm Lloyd Wise, notes that a corresponding European patent application (No. 1 458 741) making similar claims to the UK patent has been filed but has not yet started examination. Hally says, "I would be more interested in obtaining a granted European patent which can stand up to" legal challenges throughout the European Union. She also notes that if the firm does receive the European patent, it would be required to choose whether it will maintain the European or UK patent.Sirna's Robin notes that the firm has filed the same claims in the United States, but it could be two years before a decision is reached. The company has also filed patents on about 120 other targets that are important in Parkinson disease, hepatitis B and C, Huntington disease, and HIV."At some point, I believe that people are going to have to come to Sirna for a license," Robin says. "We do have an intellectual property estate that is second to none that's going to have to be addressed at some point."However, Warburg questioned whether such broad claims would survive a challenge in the United States. He says that given recent US case law, there is a possibility that claims of this sort of breadth could be judged invalid.

Sirna Granted Two UK Patents

The UK Patent Office recently granted Sirna Therapeutics two broad patents that cover short interfering RNAs, and the company has similar patents pending in the US Patent and Trademark Office and the European Patent Office.

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