A reader on Philip Brooks’ Patent Infringement Updates asked about the downstream effects of the CAFC decision invalidating Pfizer’s Norvasc® patent (U.S. Patent No. 4,879,303). In this appeal, the CAFC held that the district court erred in holding that the subject matter of claims 1-3 of the ’303 patent would not have been obvious. Pfizer, Inc. v. Apotex, Inc. (f/k/a Torpharm) (2006-1261; Decided March 22, 2007).

But, Pfizer won in three earlier district court cases, including a case against Mylan Pharmaceuticals that was handed down just last month. In that case, a federal court in the Western District of Pennsylvania (Pittsburgh) upheld the patent covering the active ingredient in Norvasc.

The judge ruled that the ‘303 patent covering amlodipine besylate was valid, enforceable and would be infringed by Mylan’s product. The decision, which has already been appealed by Mylan, handed down an order barring Mylan from launching a generic version of amlodipine until September 2007.

On a related note, a federal court in the Northern District of Illinois ruled against Apotex in January 2006; and a federal court in the Middle District of North Carolina rejected a challenge by Synthon in August 2006.

A reader posed the following questions:

Mylan is engaged in a separate appeal of Norvasc litigation involving the same patent.

Does the reversal of patent validity in one case mean that the patent is no longer valid across the board, and that the Mylan appeal is now moot and Mylan can launch?

Or does the lower court injunction barring Mylan’s launch still apply?

If a patent is held invalid, it is invalid as to all parties (see Blonder-Tongue case). Therefore, Mylan’s appeal is moot (although I don’t know the details of the appeal). The Supreme Court’s decision in Blonder-Tongue Laboratories, Inc. v. University of Illinois Foundation, 402 U.S. 313 (1971), requires that Pfizer cannot assert patents against one party which have been found to be invalid or unenforceable against another party.

In Blonder-Tongue, the Supreme Court permitted accused infringers to plead collateral estoppel, also known as issue preclusion, when facing an infringement claim on a patent already declared invalid in a proceeding against another defendant, i.e., after the above CAFC case finding that Apotex has proven invalidity or unenforceability of Pfizer’s patents based on obviousness, Pfizer is not permitted to continue to assert the patents in proceedings against Mylan.

Blonder-Tongue permitted the use of defensive collateral estoppel when the accused infringer shows 1) that a patent was found invalid in a prior case that had proceeded through final judgment and in which all procedural opportunities were available to the patentee; 2) that the issues litigated were identical; and 3) that the party against whom estoppel is applied had a full and fair opportunity to litigate.

The injunction just doesn’t go away, however, so Mylan will have to go to the judge and move to have the injunction lifted in view of the finding that the patent is invalid.


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  1. Thank you for clarifying that the patent is invalid for all. However, does that mean that Mylan will have 180-day exclusivity as it is first to file?

    Or will the exclusivity be only until Mar 25, 2007, the date the patent expires without PED extension?

  2. I think, Mylan shall not be able to enjoy 180 day exclusivity b/s 180 day exclusivity is awarded only to that ANDA filer who was first to file and was able to win the case of non-infringement. In this case even though Mylan was first to file, but it lost the case in District Court when sued by Pfizer.

  3. Ria Sen is, I believe, incorrect- the successful defense rule was effectively overturned in Mova v Shalala. Mylan should therefore keep its 180 days exclusivity

  4. […] If a patent is held invalid, it is invalid as to all parties (see Blonder-Tongue case). Therefore, Mylan??s appeal is moot (although I don??t know the details … Source http://www.patentbaristas.com/archives/2007/03/22/patents-found-invalid-against-one-party-are-unenforceable-against-another-party/ […]

  5. I would think that the exclusitivty could only apply until the patent expriy date which is march 25, 2007. The pediatric exlcusivity only applies to valid patents so that would disappear with the patent being found invalid. So Mylan would have 3 days of exclusivity. Come Monday and assuming that other generics get final approval, everyone else could start selling also.