A recent decision by the Federal Circuit (Novartis Pharms. Corp. v. HEC Pharm Co., Ltd., No. 2021-1070 (Fed. Cir. 1/3/2022)) highlights the value of negative claim limitations as a tool to overcome rejections and patent challenges. The court addressed an attempt by a patent applicant to use a negative claim limitation that was not explicit in the original application, to support claims on an alternative feature of the invention. The court rejected a challenge that the negative limitation did not meet the written description requirement and this decision gives guidance on how to craft negative claim limitations that survive challenges.

The written description requirement is one of the trickier aspects of patent drafting. This requirement mandates that a patent includes a “written description of the manner and process of making and using the invention, in such full, clear, concise, and exact terms as to enable any person skilled in the art to which it pertains to make and use the invention.” (35 U.S.C. §112(a)). The written description requirement “serves both to satisfy the inventor’s obligation to disclose the technologic knowledge upon which the patent is based, and to demonstrate [to a person skilled in the art] that the patentee was in possession of the invention that is claimed.” Ariad Pharms., Inc. v. Eli Lilly and Co., 560 F.3d 1366, 1372 (Fed. Cir., 2009). But, it is difficult for a patent drafter to anticipate the range of objections that could come up during prosecution or in a later patent challenge. Patent drafters and inventors have often been in the position of wishing there was some aspect of the invention that could have been included in the original application, that in retrospect seemed like an obvious thing to say and could have addressed an argument from a patent examiner.

This case pertains to one approach applicants use in later prosecution – negative claim limitations. The patent in dispute in this case (US 9,187,405, owned by Novartis) claimed a method of treating multiple sclerosis with the drug fingolimod, at a dose of 0.5 mg per day, and included a negative claim limitation, “absent an immediately preceding loading dose regimen.” HEC challenged the ‘405 patent on the basis insufficient written description for the no-loading-dose limitation and for the dosage quantity. This claim limitation was not explicitly disclosed in the ‘405 patent application or a relevant priority application. 

The ‘405 patent described a rodent experiment, the “EAE” experiment, in which rats given the drug had a complete remission of symptoms. The patent also described a prophetic clinical trial, in which patients would receive 0.5, 1.25, or 2.5 mg per day of the drug. 

With respect to the negative claim limitation, the district court concluded that a person skilled in the art would have understood that there was no loading dose in the EAE experiment or prophetic clinical trial, so the written description requirement was met. 
The Federal Circuit, in a 2-1 split (O’Malley and Linn, dissent by Moore), affirmed the district court (D. Del, Jordan). The opinion first notes that there is no new and heightened standard for negative claim limitations. Inphi Corp. v. Netlist, Inc., 805 F.3d 1350, 1356 (Fed. Cir. 2015). The opinion then cites to Santarus, Inc. v. Par Pharmaceutical, Inc., (2012) in which claims to treatment with a pharmaceutical composition containing no sucralfate were adequately described. The Santarus court found that a skilled person would understand that sucralfate had disadvantages and the specification described a reason to exclude the relevant limitation. In Inphi, the court found that that the written description requirement is satisfied where the essence of the original disclosure conveys the necessary information, regardless of how it conveys such information. Further, the Inphi court found that the reason for the negative limitation (required by Santarus) could be properly described with alternative features. The Inphi patent did not expressly articulate a reason for the negative limitation, but it the court found it still met the written description requirement because of the requirements of a standards organization, and a table and language in the specification distinguishing the relevant features.

However, there is conflicting counsel in the Manual of Patent Examining Procedure (MPEP, which is persuasive but not binding on the Federal Circuit). The MPEP states the “mere absence of a positive recitation is not a basis for an exclusion.” MPEP § 2173.05(i). On the other hand, written description may take any form, so long as a skilled artisan would read the disclosure as describing the claimed invention. Id.  Moreover, MPEP §2163 states that “newly added claims or claim limitations must be supported in the specification through express, implicit, or inherent disclosure.” (Emphasis from the opinion). The use of alternative language in the disclosure supports an implicit disclosure. The majority finds that was the case with this patent. So, negative limitations can be useful and survive challenges.

The dissent in this case would have held that the negative claim limitation was not supported by the disclosure and would have found the patent invalid. 

Written description cases should be of great interest to patent prosecutors, because many problems down the road can be avoided by getting the drafting right on filing. The lesson here is that patent drafters must seek to anticipate objections that may arise in prosecution and other patent challenges and must include sufficient alternatives to the elements of the invention so that if a negative claim limitation later becomes desirable, it will be supported by the specification. Additionally, a key point in all the examples cited in the opinion was the reliance on expert testimony to determine what a person skilled in the art would understand. Thus, in prosecution, patent attorneys should rely on inventor or expert declarations to support a negative limitation.