Barr and Mylan Invalidate Boehringer Ingelheim's Patent on Mirapex

Includes: BRL, MYL
by: Aaron F. Barkoff

A week ago, following a bench trial held in March, the U.S. District Court for the District of Delaware held that Boehringer Ingelheim's patent on Mirapex (pramipexole dihydrochloride) is invalid for obviousness-type double patenting.  Mirapex, indicated for the treatment of Parkinson's disease and Restless Leg Syndrome, has annual U.S. sales of approximately $380 million.

Barr Labs (BRL) filed its ANDA for a generic version of Mirapex in 2005 with paragraph IV certifications to Boehringer's U.S. Patent Nos. 4,843,086 and 4,886,812.  Mylan (NASDAQ:MYL) filed its ANDA, with paragraph IV certifications to the same patents, shortly thereafter.  Barr's approval letter confirms that Barr was the first to file, and therefore is entitled to 180-day exclusivity.

Boehringer responded by filing suit against Barr and Mylan, and the cases were consolidated for trial.  The '086 patent expired while the litigation was pending, leaving only the '812 patent in suit.

The district court's opinion explains that the "basic premise of double patenting is that the same invention cannot be patented twice."  Here, the '086 patent claimed methods of treating certain diseases by administering tetrahydrobenzthiazoles, while the '812 patent claims the tetrahydrobenzthiazole compounds themselves, including the active ingredient in Mirapex, pramipexole dihydrochloride.  The court concluded that,


although there are differences between the '812 patent and the '086 patent, . . . those differences are insufficient to support the patentability of the '812 patent in light of the '086 patent.


Of course, obviousness-type double patenting can be avoided by a terminal disclaimer.  Interestingly, Boehringer filed a terminal disclaimer of the '812 patent on the second day of trial of the case, on March 12, 2008.  Boehringer terminally disclaimed:

only the terminal part of the statutory term of the '812 patent which would extend beyond the 1,564 days after the full statutory term of the '086 patent as that term is defined in 35 U.S.C. § 154, so that by virtue of this disclaimer, the '812 patent will expire on October 8, 2010.

Boehringer received a 1,564-day extension under 35 USC § 156 due to FDA regulatory review of Boehringer's New Drug Application for Mirapex.  As a result of this patent term extension, the original expiration date of the '812 patent, December 12, 2006, was extended to March 25, 2011.  Thus, by its terminal disclaimer, Boehringer disclaimed five and a half months of patent term - the period of time between the expiration date of the '086 patent and the original expiration date of the '112 patent.

Boehringer argued that the terminal disclaimer obviated Barr and Mylan's double-patenting argument.  However, the court noted that,


a dual problem is presented in that the terminal disclaimer was not only filed at or near the conclusion of trial in this action, but it was also filed after the expiration of the earlier '086 patent.


Citing two cases, the court observed that "the Federal Circuit has at least suggested in dicta that for a terminal disclaimer to be effective, the earlier filed patent must not have expired at the time of the filing of the disclaimer." 

Boehringer tried to distinguish these cases "because neither case involved a terminal disclaimer in the context of a Section 156 patent term extension," but the court was not persuaded.  The district court held that Boehringer's terminal disclaimer was ineffective to moot the double patenting issue because it was filed after the '086 patent had expired.

According to an investor note from Bernstein Research, the decision was surprising because the district court was not expected to


make a controversial opinion on what is likely to be a precedent-setting ruling by the appellate court on patent extensions and terminal disclaimers.


In addition, the note indicates that Bernstein expects Barr to "maximize the value of the challenge through settlement."  According to Bernstein,


the most likely settlement is that Barr would have a date-certain launch of generic Mirapex in 2010 with an agreement protecting it from both an authorized generic and a potential Boehringer win on appeal.


The "failure to market" forfeiture provisions, however, will likely complicate any settlement discussions.  Under the MMA, the 180-day exclusivity period may be forfeited if the first applicant does not launch its generic drug product within 75 days after "a court enters a final decision from which no appeal (other than a petition to the Supreme Court for a writ of certiorari) has been or can be taken that the patent is invalid or not infringed." 

If Boehringer and Barr settle the case, for example, with an agreement that Boehringer will not appeal, Barr's 180-day exclusivity would be forfeited later this summer.  For at least this reason, Boehringer is expect to appeal the district court decision.