negative limitation : CAFC Alert

When does the absence of evidence turn into evidence of absence? The CAFC vacate their prior decision to now hold that there must be evidence that a skilled artisan would understand silence regarding a limitation to necessarily exclude said limitation.

| September 9, 2022

Novartis Pharmaceuticals v. HEC Pharms Co, Ltd, & Accord Health Care et al.


HEC petitioned for rehearing of a CAFC prior decision in this case, (21 F 4th 1362 – Fed. Cir. 2022) in which the CAFC affirmed a final judgement of the Delaware district court determining that claims 1 to 6 of US Patent 9,187,405 are not invalid and that HEC infringes them. The CAFC Panel in the prior case was Judges, Moore (dissent) with Linn and O’Malley. Here, Chief Judge Moore with Circuit Judge Hughes (majority herein after) vacate the CAFC’s prior decision holding that the Novartis claims are invalid for inadequate written description pertaining to a negative limitation.

  • Background

Novartis owns the ‘405 patents and markets a drug for treating relapsing remitting multiple sclerosis that purportedly practices the patent. HEC filed an ANDA with the FDA seeking approval to market a generic version of the drug. Novartis sued. The Delaware district count found that the claims were not invalid either as anticipated or for inadequate written description of the no-loading-dose or daily dosage limitations. HEC appeals as to the written description issue of the no-loading dose.

Claim 1 at issue recites in part “a daily dosage of 0.5 mg, absent an immediately preceding loading dose regime.” The appeal at hand being related to the underlined negative limitation. A loading dose is a higher-than-normal daily dose.

The Majority go into detail regarding what is required to satisfy the written description, stating that “[F]or negative claim limitations…. there is adequate written description when., for example, “the specification described a reason to exclude the relevant [element]… A reason to exclude an element could be found in ‘statements in the specification expressly listing the disadvantages of using’ that element and alternatives to it…. Silence is generally not disclosure.” The Majority further noted that the negative limitation may not be recited verbatim in the specification, but there “generally must be something in the specification that conveys to a skilled artisan that the inventor intended the exclusion, such as a discussion of disadvantages or alternatives.” However, the Majority further noted that while “a written descriptions silence about a negative claim limitation is a useful and important clue and may often be dispositive, it is possible that the written description requirement may be satisfied when a skilled artisan would understand the specification as inherently disclaiming the negative limitation.”

The district count had found that the negative limitation was supported because the prophetic trial described therein states “initially” giving a daily dose, thus this would inform the skilled artisan that there was no loading dose. The Majority found this interpretation erroneous arguing that because the specification says “Initially patients receive treatment for 2 to 6 months” it is clear this sentence speaks to the initial length of treatment and not the dosage. The Majority believed that one of the two Novartis experts admitted this, and that the contrary testimony by the second Novartis experts was inconsistent with the plain text of the specification and therefore carried no weight.

Next, the Majority discussed the district courts finding that the specifications disclosure of a daily dosage combined with its silence regarding a loading dose would tell a person of skill that loading doses are excluded. However, the Majority countered that a patent is not presumed complete such that things not mentioned are necessarily excluded. The Majority noted that the applicants added the limitation during prosecution to address a prior art rejection arguing that the limitation was “to specify that the [daily dosage] cannot immediately follow a loading dose regiment” and “to further distinguish their claims.” The Majority argued that if reciting “daily dosage” without mentioning a loading dose necessarily excludes said loading dose, there would have been no reason for the applicants to add the limitation.

The Majority noted that the expert testimony focused on where in the specification the patentee would have mentioned a loading dose if they intended a loading dose to be included, but that is not the issue at hand, rather the question is whether the patentee precluded the use of a loading dose. The Majority concluded that there is no evidence that a skilled artisan would understand silence regarding a loading artisan to necessarily exclude a loading dose.

Thus, the Majority vacated their prior decision and reversed the distinct courts judgement that the claims of the ‘405 patent are not invalid.

  • Dissent:

Circuit Judge Linn dissented, her opinion being very reminiscent of her opinion in the prior judgment, for which she penned the Majority. CJ Linn stated that the “majority in its analysis employs the heightened standard of “necessary exclusion” against which to assess the district court’s fact findings in this case and uses that standard to conclude that the district court clearly erred.” CJ Linn argued that the central tenet of the written description jurisprudence is that the disclosure must be read from the perspective of a person of skill in the art. Here, CJ Lin argued that the district conducted an objective inquiry into the four corners of the specification and found sufficient written description, while also crediting the expert testimony. In particular, the testimony that one skilled in the art would understand the loading dose to be excluded, and that loading dose regiments have been used in the prior art for treating MS. CJ Linn concluded this is sufficient to show that claim language that precludes the administration of a loading dose is supported.


  • When express support for a negative limitation is absent, look for evidence that a skilled artisan would understand the silence regarding the limitation to necessarily exclude said limitation.
  • Be mindful of statements made during prosecution as to why an amendment is being made.

Amending to exclude a species via a negative limitation may violate the written description requirement

| August 7, 2013

In re Bimeda Research & Development Limited

July 25, 2013

Panel:  Rader, Clevenger, Prost.  Opinion by Clevenger.  Concurrence by Rader.


The court held a negative limitation to exclude a genus does not provide 112, first paragraph written description support to claim a negative limitation that excludes a species, which species was never mentioned in the application.

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