On September 4, 2012, the Federal Circuit issued an opinion in an appeal from the U.S. District Court for the District of Delaware. Santarus, Inc., et al. v. Par Pharm., Inc., No. 2010-1360, -1380 (Fed. Cir. Sept. 4, 2012). Plaintiff Santarus is the exclusive licensee of patents on specified formulations of proton pump inhibitors (PPIs) used in the brand name drug Zegerid. Par filed an Abbreviated New Drug Application (ANDA) seeking FDA approval to sell generic Zegerid prior to the expiration of these patents, thus invoking a patent infringement suit under the Hatch-Waxman Act. The district court found that Par's ANDA products infringed the patents, but held that the asserted claims were not entitled to priority and that all of the asserted claims were invalid for obviousness. In addition, the district court held that certain claims were invalid for lack of written description. The district court also found the patents enforceable.

The Federal Circuit affirmed the district court's ruling that the patents were enforceable, reasoning that the inventor did not commit inequitable conduct and, in particular, that intent to deceive was not found. However, the Federal Circuit held that the district court erred in finding (1) that the asserted claims failed to meet the written description requirement; (2) that some of the asserted claims were not entitled to priority; and (3) that some of the asserted claims were obvious over the prior art. With respect to the written description issue, the Federal Circuit held specifically that the district court erred by holding that, when a claim includes a negative limitation (i.e., "contains no sucralfate"), it is necessary for the specification to include evidence demonstrating that the negative limitation is contraindicated. Rather, the majority stated that negative claim limitations are adequately supported when the specification describes a reason to exclude the relevant limitation. Such written description support need not rise to the level of disclaimer.

With respect to the priority and obviousness issues, for those claims for which Santarus appealed priority, the Federal Circuit reversed and held that the claims were entitled to a priority filing date and were not obvious over a parent patent. The primary issue on appeal was whether a solid dosage form of non-enteric coated PPI, such as omeprazole, would have been obvious to one of ordinary skill in the art. The Federal Circuit concluded that the prior art "ruled out" the use of non-enteric coated conventional oral dosage forms such as tablets, capsules, or granules so claims limited to those dosage forms were found valid. The court nevertheless affirmed that the broader claims, not limited to tablets, capsules or granules, were invalid.

Judge Newman dissented to three aspects of the majority opinion. First, Judge Newman agreed that the district court erred in finding no written description, but disagreed that negative claim limitations only find written description support if the specification states a reason to exclude the relevant limitation. Second, Judge Newman stated that the panel majority created another new ground of invalidity in holding that the common disclosure in a parent patent is prior art to the chain of continuing patents. Third, Judge Newman dissented to any finding of obviousness, stating that the prior art and the expert witnesses were explicit and uniform, that benzimidazole PPIs require an enteric coating for practical oral administration to patients. There was no evidence contrary to the position that an enteric coating was believed to be necessary. This is a classic example of "teaching away."

What This Means for You

Based on the majority opinion, there is now a question of whether negative claim limitations can only find written description support if the specification states a reason to exclude the relevant limitation.

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