Federal Circuit Addresses Written Description for Negative Claim Limitations and Clarifies Obviousness for CIP Applications

September 4, 2012

What This Means To You

  • Listing disadvantages of the prior art in the specification can provide written description support for negative claim limitations.
  • In a continuation-in-part application (CIP), include claims with non-overlapped ranges from the parent patent to avoid obviousness rejection.


In Santarus, Inc. v. Par Pharmaceutical, Inc., the U.S. Court of Appeals for the Federal Circuit (Federal Circuit) addressed the issues of written description for negative claim limitations and obviousness in CIP applications.

The panel majority affirmed in part and reversed in part the district court’s holding, finding that some of the asserted claims were not obvious over the prior art but that the district court erred in concluding the patents were invalid due to inadequate written description.

Case Background

Santarus was the exclusive licensee of patents directed to specific formulations of proton pump inhibitors (PPI) and marketed its product under the brand name Zegerid. Santarus sued Par Pharmaceutical upon Par’s filing of an abbreviated new drug application to sell a generic counterpart of Zegerid.

The district court found Par’s product would infringe but held the asserted claims invalid for obviousness and lack of written description. Santarus and Par cross-appealed.

Decision Analysis

The Federal Circuit began by reversing the district court’s ruling that the claim limitation of “wherein the composition contains no sucralfate” lacked written description. The district court held that the adequate written description for negative claim limitations required evidence in the specification to demonstrate that sucralfate is contraindicated. The Federal Circuit disagreed and held that “[n]egative claim limitations are adequately supported when the specification describes a reason to exclude the relevant limitation,” and that “[s]uch written description support need not rise to the level of disclaimer.”

According to the Federal Circuit, “[i]t is possible for the patentee to support both the inclusion and exclusion of the same material.” The Federal Circuit then found that the negative claim limitation was adequately supported by statements in the specification expressly listing the disadvantages of using sucralfate.

Addressing the obviousness of the asserted claims, the Federal Circuit affirmed the district court’s ruling that the parent patent would have rendered obvious all CIP claims to which it was prior art. The Federal Circuit rejected Santarus’s argument that the parent patent did not disclose nonenteric coated PPIs and buffer within the claimed ratios, noting that the parent patent’s disclosed ranges overlapped with the claimed ranges. The Federal Circuit also rejected Santarus’s argument that the claims reciting specific blood serum concentrations of PPI would have been nonobvious because the initial blood serum concentration resulting from administering a PPI dosage is an inherent property of the formulation.

Regarding the claims entitled to the priority of the parent patent, the Federal Circuit reversed the district court’s obviousness finding of certain claims since the prior art was explicit in teaching away from the claimed conventional nonenteric coated forms by specifying “conventional oral dosage forms with enteric-coated PPIs” offer the best possibilities. But the Federal Circuit affirmed other claims as obvious since the prior art would not teach away from all other non-enteric formulations such as the claimed “suspensions of buffered non-enteric coated forms.”


This case provides an additional approach to finding written description support for negative claim limitations by listing disadvantages of the prior art in the specification.

The case also highlights the importance of strategizing CIP applications. It is recommended to draft claims with non-overlapped ranges with the parent patent so that the parent patent would not render the CIP claims of the new ranges obvious.