Negative Claim Limitations – Is Silence Enough?
Negative claim limitations are often used during patent prosecution to overcome cited prior art. Unfortunately, patent drafters do not always consider the possible need for negative claim limitations, and specifications are often silent on what is excluded or why. Examples are often used as the sole basis for a negative limitation. A recent decision by the U.S. Court of Appeals for the Federal Circuit (CAFC) highlights the need for caution when considering amending a claim to include a negative claim limitation for which the specification is silent.
On June 21, 2022, in Novartis Pharmaceuticals Corp v. Accord Healthcare, Inc., [[1]] the CAFC vacated its previous decision [[2]] after a panel rehearing on the validity of Novartis’ claims based on the absence of sufficient written description to support a negative claim limitation. Further, the CAFC reversed the district court’s decision, finding that Novartis’ claims are invalid for inadequate written description.
Initially, in its original decision, the CAFC affirmed a district court finding that claims 1-6 of U.S. Patent No. 9,187,405 (the ’405 patent) were not invalid and that the Abbreviated New Drug Application (“ANDA”) filed by codefendant HEC infringed. Following HEC’s petition for rehearing and the replacement of Judge O’Malley with Judge Hughes, the CAFC vacated that original decision and reversed the district court’s decision, finding in favor of HEC.
The ’405 patent claims methods to treat relapsing remitting multiple sclerosis (RRMS), a type of multiple sclerosis (MS), requiring administration of fingolimod or a fingolimod salt “at a daily dosage of 0.5mg, absent an immediately preceding loading dose regimen.” A loading dose refers to a higher than daily dose which is administered as a first dose. Novartis owns the ’405 patent and manufactures a drug under the brand name GILENYA® that practices the patent. HEC filed an ANDA with the FDA with the intention of manufacturing a generic version of GILENYA®. In response, Novartis filed suit against HEC, alleging that the filed ANDA infringes the claims of the ’405 patent.
Among other issues, the district court found that the negative limitation included in claim 1 of the ’405 patent, “absent an immediately preceding loading dose regimen,” was supported by adequate written description under 35 U.S.C. §112(a). HEC appealed on this issue.
The addition of negative claim limitations is a strategy often employed during patent prosecution, particularly in cases which employ one or more examples to explain and demonstrate the invention to a reader.
The Patent Act, 35 U.S.C. § 112(a), states that a patent’s specification must contain a “written description of the invention, and of the manner and process of making and using it.” HEC argued that the negative limitation lacked written description in the specification, since the specification does not mention a loading dose at all. The CAFC has previously decided several cases involving the issue of adequate support in the written specification for negative claim limitations, including Santarus, Inc. v. Par Pharmaceutical, Inc. [[3]], In re Bimeda Research. & Development Ltd. [[4]], Inphi Corp. v. Netlist, Inc. [[5]], and Nike, Inc. v. Adidas AG [[6]].
In its previous cases, the CAFC has established that there is no “new and heightened standard for negative claim limitations.” Further, the court held in Santarus that “[n]egative claim limitations are adequately supported when the specification describes a reason to exclude the relevant limitation,” which does not require that the specification must describe such a reason. [A reason to exclude may, for example, be demonstrated “by properly describing alternative features of the patented invention.”
The CAFC has further held that an added negative claim limitation must be consistent with the disclosure, particularly with the provided reason to exclude. For example, the court in In re Bimeda held that a claim which excluded acriflavine, an anti-septic, from a sealing formula intended to prevent mastitis in dairy cows was inconsistent with the disclosure, which repeatedly emphasized that the described method was able to prevent mastitis without the use of antibiotics. As such, the court stated that the disclosure was “inconsistent with a claim which excludes acriflavine, but not the presence of other anti-infectives or antibiotics.”
Inphi involved a patent that perhaps bears the most similarity to the ’405 patent. In particular, the added claim limitation recited “DDR chip selects that are not CAS, RAS, or bank address signals,” though the disclosure did not explicitly include a reason to exclude CAS and RAS signals. However, in contrast to the ’405 patent, the exclusion present in Inphi was supported by standards provided by the Joint Electron Device Engineering Council, the contents of which were incorporated by reference into the specification, a table in the specification excluding RAS and CAS signals, and passages and a figure in the specification which served to distinguish the various signal types. As such, the court found that the specification sufficiently disclosed alternative features and complied with the written description standard.
Negative limitations may also be supported by figures. For example, in Nike, a limitation of “flat knit edges,” which Adidas asserted was a negative limitation, was appropriately supported by three figures depicting a claimed textile element that could be manufactured using flat knitting, which contrasted with an additional figure depicting a textile element that could be manufactured using a circular knitting machine.
In contrast to its own prior rulings, however, the CAFC in Novartis seems to require “not only a ’reason to exclude’ but a showing that the negative limitation in question was ’necessarily excluded.’” In fact, the court seems to explicitly go against its own ruling in Inphi, where it held that a negative limitation added during prosecution was sufficiently described by the specification which did not expressly exclude the elements of the negative limitation.
However, it should be noted that this case does differ from Inphi in some key ways. First, Novartis’ specification provides an example prophetic trial, where a dosing regimen is described. In this trial, a daily dose is administered, with no mention of a loading dose, like the subject matter discussed in the claims. Novartis argued that this example demonstrated an exclusion of a loading dose, since starting with a daily dose implies that a loading dose is not administered. In contrast, Inphi focused on the exclusion of certain signal types, where the exclusion was supported not by an example, but by incorporated reference materials and tables embedded in the specification.
Novartis had originally claimed “at a daily dosage of 0.5mg,” but later amended the claim to further recite “absent an immediately preceding loading dose regimen,” In order to distinguish cited prior art. In its argument filed with this amendment, Novartis asserted that they were simply clarifying that a daily dose cannot immediately follow a loading dose. But the CAFC said, “[i]f reciting ‘daily dosage’ without mentioning a loading dose necessarily excluded a loading dose, there would have been no reason for the applicants to add the no-loading-dose limitation.”
The CAFC’s Novartis decision raises a question of whether the standard has now changed—does a negative limitation now have to be described as necessarily excluded in the specification in addition to the specification having a reason to exclude? In a dissenting opinion, Circuit Judge Linn sees it that way but disagrees that it is the correct decision. Judge Linn notes that “[t]he question is not whether the patentee precluded the use of a loading dose but whether the claim language that precludes the administration of a loading dose is supported by the written description passages that disclose the effective administration of nothing more than a ’daily dose.’”
Though there is prior precedent allowing for implicit support of negative limitations, applicants are best advised in view of Novartis to be wary of adding such limitations during prosecution if there is not explicit support for the negative limitations in the original specification. Further, this should serve as a reminder to patent drafters to ensure that every specification should fully encompass as many potential alternatives as possible to avoid similar issues arising during future prosecution or patent litigation disputes.
Lastly, if a negative limitation is being considered for which a specification is silent, it may be preferable to recite a positive claim limitation instead of the negative limitation, if at all possible. For example, in this instance, one could consider an amendment reciting something like “on the first and subsequent treatment days, administering a dose of X…” to possibly convey and claim the intended dosing regimen. The recitation of a positive limitation, properly supported by the specification, may avoid the issues raised in the Novartis case that was caused by silence in the specification.
In conclusion, patent drafters should be wary about employing negative limitations in prosecution, given the changing and perhaps heightened standard for what constitutes adequate written support for such limitations under 35 U.S.C. § 112(a). The Novartis decision demonstrates that including a reason to exclude may no longer provide sufficient support for negative claim limitations. It may be prudent for patent drafters to turn to other strategies in order to convey the same intended limitation. Though there is prior precedent in favor of silence as appropriate support for negative claim limitations, silence may no longer be good enough.
