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USPTO Gives OK to Santaris Request for Re-Exam of Regulus miR-122 Patent

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Santaris Pharma this week announced that the US Patent and Trademark Office has accepted its request to re-examine a patent exclusively licensed by rival Regulus Therapeutics covering the use of microRNA-122 inhibitors to treat hepatitis C infection.

Both companies are developing miR-122-targeting agents for HCV.

The intellectual property row centers around US patent No. 7,838,504, entitled “Methods and Compositions for Reducing Viral Genome Amounts in a Target Cell,” which relates to the treatment of an HCV-infected cell with an antisense agent complementary to miR-122 and stems from the work of Stanford University's Peter Sarnow.

While Regulus has touted its exclusive license to the patent as key to preventing other companies from developing their own miR-122 inhibitors for HCV, Santaris has long said that it has freedom to operate with its own compound.

To validate its position, Santaris has sought reviews of the Sarnow IP in some of the various territories where it has been issued, including Europe and Australia. Now, the company has taken the fight to the US.

The stakes are particularly high for Santaris, as its miR-122 drug, called miravirsen, is the most advanced in its pipeline. According to Santaris CEO Henrik Stage, the company recently completed a phase II trial examining the drug in HCV patients as part of a combination therapy along with Johnson & Johnson's Telaprevir.

The company has also launched a phase II trial testing miravirsen as a 12-week monotherapy in order to extend the drug's safety data beyond the four weeks evaluated in a previous phase IIa study, he said, adding that Santaris is also in discussions with US regulators about a planned phase II trial combining miravirsen, Telaprevir, and the widely used anti-viral agent ribavirin.

That triple-drug study is expected to begin in the first half of this year, with data available by year-end, Stage said.

Notably, Santaris is the only company to have moved an miRNA drug into the clinic; Regulus has said that its own miR-122 inhibitor is currently in non-human primate testing and could be ready for the clinic by 2014.

Despite its first-mover advantage, Santaris missed out on reaching its longstanding goal of finding a big pharma partner for miravirsen when GlaxoSmithKline, which held an option to the drug, opted to partner with Regulus on its HCV agent in early 2010 (GSN 2/25/2010).

Stage told Gene Silencing News this week that his company still hopes to partner miravirsen before moving into phase III, in part because of the “financial challenge” pivotal clinical trials represent for a small, privately held biotech such as Santaris.

He declined to comment on rumors that Regulus' access to the Sarnow IP played a role in GlaxoSmithKline's partnering decision, but said that “all our business development discussions have been on the basis that we have freedom to operate.”

In any case, he noted that having a formal USPTO ruling on the matter would certainly help Santaris in negotiations with potential partners.

Santaris said this week that USPTO, as part of its order granting the re-examination request, indicated that the company has established “a reasonable likelihood” that it will prevail in its opposition to claims within the '504 patent, although Stage cautioned that this does not represent a final decision on the agency's part.

He declined to comment on the specifics of Santaris' objections to the patent. However, in its opposition to the IP's European counterpart, the company said that the patent does not disclose “the alleged invention in a manner sufficiently clear and complete for it to be carried out by a person skilled in the art;” that it lacks novelty in light of prior art; and that the patent “amounts, at best, to a discovery and/or scientific theory.”

Officials from Regulus did not return a request for comment.

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