Section 112 written description requirements present a challenge for patentees claiming negative limitations, as the extent to which a specification needs to disclose the absence of a feature is not entirely clear, especially following the recent Federal Circuit case Novartis v. HEC Pharm Case No. 1:18-cv-01043-KAJ (Fed. Cir. June 21, 2022). In its review of negative claim limitations, a split Federal Circuit panel reversed a prior split panel decision and ultimately found a pharmaceutical dosing patent invalid as lacking written description support for negative claim limitations.

Plaintiff Novartis markets fingolimod hydrochloride treatment for relapsing remitting multiple sclerosis under the name Gilenya®. Numerous defendants sought to market a generic version of the drug, and ANDA litigation concerning U.S. Patent No. 9,1867,405 ensued.  At trial, HEC Pharm (“HEC”) (the sole appellant) argued that that the patent was invalid for failing to meet the 35 U.S.C. § 112 written description requirement for the negative claim limitation “absent an immediately preceding loading dose regimen,” which was added during prosecution to overcome prior art.

The district court found that the specification provided adequate written description because it “indicated to a person of ordinary skill that the claimed invention did not include the administration of a loading dose.” The Federal Circuit initially affirmed, rejecting HEC’s argument that the negative limitation must be mentioned, or its potential benefits or disadvantages discussed. The panel stated that there is no “heightened standard for negative claim limitations.”

The case was initially decided on January 3, 2022, with Judges Linn and O’Malley in the majority, and Chief Judge Moore writing the dissent. Defendant quickly petitioned for a panel rehearing. In this time, Judge O’Malley was replaced by Judge Hughes. Unexpectedly, on June 21, 2022, the new panel (Judges Linn, Moore, and Hughes) granted rehearing, reversed its original decision, and reached an opposite conclusion. Judge Hughes fervently supported Chief Judge Moore’s position, reversing the district court’s judgement with Chief Judge Moore authoring the new opinion, and Judge Linn, who was previously in the majority, dissenting.

The second panel again stated that there is no heightened standard for negative claim limitations, but it explained that the specification must convey a reason to exclude a negative claim limitation. While negative limitations need not be stated in the specification verbatim, the specification must reasonably convey to a skilled artisan that the exclusion was intentional, for example, by discussing the disadvantages of alternatives. Because the ’405 patent failed to disclose the absence of a loading dose, either expressly or inherently, the panel found it invalid.

Despite the majority’s assertion, as evident by Judge Linn’s dissent, it appears that a heightened standard for negative limitation disclosure in satisfying the written description requirements may be on the horizon.  The differing outcomes of two split panels indicate that this is an area that is still somewhat unsettled.  In the meantime, patent challengers should pay special attention to later-added negative limitations and scrutinize the specification to identify potential written description challenges.

Thanks to Justin Oakland, University of Minnesota Law School student, for his contributions to this post.