On December 15, 2009 the USPTO issued a ‘Notice of Intent to Issue an Ex Parte Reexamination Certificate’ confirming the patentability of Merck’s billion dollar Singulair patent, U.S. 5,565,473.  This development effectively concludes the reexamination of the Singulair patent.  In initiating the reexamination, the USPTO issued a single nonstatutory obviousness-type double patenting reexamination rejection.  Double patenting rejections relate to the ability of a Patent Holder to obtain multiple patents on obvious variations of a single invention.  This rejection, if maintained by the Office would not have invalidated the patent, but instead, could have potentially shortened the term of the Singulair patent.  However, the rejection was withdrawn by the USPTO.

The reexamination was initiated by a third party, Article One.  Article One claimed to have uncovered highly relevant prior art and alleged in 276 pages worth of obviousness rejections, the invalidity of the Singulair patent.  As noted above, the USPTO did not agree with the submitted invalidity arguments.

At issue in the double patenting rejection was whether an articulable rationale existed for one of ordinary skill in the art would have replaced the alkane linker (-CH2CH2-) of a prior Merck patent (The ‘033 Patent) with an olefinic linker (-CH=CH-) to arrive at the compounds of the ‘473 Patent.  Merck argued that at the time of the invention, compounds with the olefinic linker were known to undergo possible photoisomerization that would lead to undesirable pharmacological properties and phototoxicity.  Merck provided a side-by side comparison of an instantly claimed compound vs. the closest compound of ‘033 to illustrate that the shift value (ratio of a compound’s potency in the presence and absence of human serum albumen) of the ‘473 compound is unexpectedly much lower than that of the comparative ‘033 compound.

As explored in a previous post on Singulair’s patent term, although a terminal disclaimer was filed during the reexamination, this filing should not impact the patent term.  Furthermore, this terminal disclaimer will not affect the 430-day extension granted under § 156 for delays in FDA regulatory review, which are added on after the terminal disclaimer date.  Merck & Co. v. Hi-Tech Pharmacal Co., 82 USPQ2d 1203, 1208 (Fed. Cir. 2007).

This is not good news for Teva.  The reexamination ruling follows on the heels of a ruling by Judge Garrett E. Brown of the U.S. District Court for the District of New Jersey on (August 19, 2009) that Teva’s generic drug would infringe Merck’s ‘473 patent, ordering the FDA to stay market approval of the generic version of Singulair pending expiration of the ‘473 Patent in 2012.  Teva has appealed the District Court’s ruling and is due to file its brief in January 2010.

Absent appeal relief Singulair will remain protected by the ‘473 Patent until February 3, 2012.