A recent Federal Circuit case, Senju Pharm. v. Apotex, Inc. (Fed. Cir. 3/31/14), highlights the importance for patent owners of finding and fixing any validity problems before asserting a patent. Senju holds U.S. Patent No. 6,333,045 (the ‘045 patent), which relates to an ophthalmic solution for eye drops. In 2007, Apotex filed an Abbreviated New Drug Application seeking approval to sell a generic version. In response, Senju filed a first suit against Apotex for infringement of the ‘045 patent. The trial court found infringement, but also held that the asserted claims were invalid as obvious. Prior to the entry of final judgment in that case, Senju filed a request for ex parte reexamination of its patent with the United States Patent and Trademark Office (USPTO) to address the validity issues. The USPTO also initially rejected the claims of the patent as obvious. In response, Senju amended its claims, and the USPTO allowed the amended claim set and issued a reexamination certificate.

With its patent validity issues seemingly cured, Senju filed a new lawsuit against Apotex alleging infringement of the reexamined claims just prior to the entry of final judgment in the first lawsuit. Apotex filed a motion to dismiss the second suit on the basis of claim preclusion, arguing that doctrine prevented Senju from proceeding with a second suit because the second suit raised the same issues as the first suit and was between the same parties. Senju argued that the reexamination created a new cause of action because the reexamined claims were substantially different from those in the original patent.

The trial court granted Apotex’s motion to dismiss, and the Federal Circuit affirmed in a 2-1 decision holding the reexamined claims did not create a new cause of action. Although the claims were amended, the reexamined claims could not be broader in any respect by statute. Accordingly, the Federal Circuit reasoned that since a reexamined patent claim could not contain within its scope any product or process that would not have infringed the original claims, the reexamined claims did not create a new cause of action that did not exist before. Senju’s second suit was bared by claim preclusion. Interestingly, as discussed in the dissenting opinion, the majority opinion did not explicitly analyze if its reasoning was equally applicable to validity and infringement issues.

The lesson from this case is clear for a patent owner contemplating enforcing a patent: cure any validity concerns early. A thorough investigation to uncover any validity issues should be conducted before a lawsuit is initiated. And if new and strong prior art is discovered, the patent owner should consider filing an ex parte reexamination to address the validity concerns prior to filing a lawsuit. Wait and the lawsuit may be too far along to effectively cure the validity problems through reexamination and assert the reexamined claims against the defendant, leaving the patent owner without relief in the face of a defendant infringing a presumptively valid reexamined patent.