Ranbaxy Obtains Inter Partes Review of HIV Prodrug Patent

Scott Daniels | March 19, 2013

Traditionally, most reexamination proceedings have involved electronic or mechanical inventions, and relatively few have concerned pharmaceuticals.  Thus far, that pattern has continued with the new AIA inter partes review trials.

There have, however, been a few requests challenging pharmaceutical patents, and earlier this month the APJs decided to institute a trial in Ranbaxy Labs. v. Vertex Pharmaceuticals, IPR2013-00024, involving U.S. Patent No. 6,436,989.  The ‘989 patent claims a set of HIV aspartyl protease inhibitors, specifically derivatives of an inhibitor known as “VX-478.”  Also claimed are treatment methods involving the administration of the protease inhibitors.  The ‘989 patent is the subject of the infringement action ViiV Healthcare Co. v. Mylan, Inc., Case No. 12-cv-1065 (D. Del.)).

In finding “a reasonable likelihood that the petitioner would prevail with respect to at least” one claim, the APJs undertook the customary “lead compound” analysis.  They determined that the primary reference relied upon by the Petitioner Ranbaxy disclosed a protease inhibitor similar those claimed, except that the prior art compound did not have a solubilizing salt.  They also found that the disclosed protease inhibitors were known to have a solubility problem and that various salts, including the patent owner Vertex’s preferred phosphate ester salt were known to improve solubility.

Citing heavily from an expert declaration filed with the Petition, the APJs concluded that one skilled in the art would have a reason to attach a phosphate ester salt to the protease inhibitors of the primary reference, specifically to improve solubility, to obtain a compound within the scope of the ‘989 patent claims.

They also concluded that one would have a reasonable expectation of success.  “We credit Dr. Fisher with having knowledge of the solubility of HIV protease inhibitors generally and find his testimony consistent with the teaching of [the primary reference] that VX-478 has a solubility [problem].

Of course, Vertex has the opportunity to submit its own expert declarations, as well as other arguments supporting the patentability of the ‘989 patent claims.  Still, Ranbaxy has convincingly won the first round.

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