The inquiry into the sufficiency of written description support turns on whether the disclosure of the application reasonably conveys to those skilled in the art that the inventor has possession of the claimed subject matter as of the filing date.  See Ariad Pharm., Inc. v. Eli Lilly & Co., 598 F.3d 1336, 1351 (Fed. Cir. 2010) (en banc).  But when the claim is directed to a genus, is disclosure of a single species sufficient to support the claim?  That issue was addressed by Synthes USA, LLC v. Spinal Kinetics, Inc., 734 F.3d 1332, 1338 (Fed. Cir. 2013).

Synthes sued Spinal Kinetics (SK) for infringement of claims directed to an intervertebral implant.  The claims at issue in the litigation were added by amendment almost five years into the prosecution of the patent and after SK’s accused infringing devices were on the market.  Id. at 1341.  In relevant part, the claims recite “a central part substantially located between the third and fourth plates, the central part including a flexible core and a fiber system, . . . wherein the fiber system . . . is at least partially received within the plurality of openings formed in the third and fourth plates so that the fiber system is joined to the third and fourth plates.”  Id. at 1336 (citation omitted).  With these new claims, Synthes introduced the concept of “openings.”  The “opening” limitations were important because SK’s devices thread their core fibers through circular slots within the cover plates to anchor the fiber system.  The patent specification, on the other hand, disclosed only “grooves” on the perimeter of the plates.  The parties agreed that “groove” is a type of “opening,” but did not agree that it constitutes adequate disclosure to claim all openings located anywhere on the plates.  Id. at 1342.

During litigation, the district court construed a number of terms, including “the third plate including a plurality of openings.”  As expected, SK argued that “plurality of openings” should be limited to “grooves on the circumference of the cover plate that radially penetrate into the lateral surface of the plate,” as described in the specification.  Id. at 1338.  The court adopted a broader construction closer to Synthes’s proposal: “the third plate including two or more openings to allow the fiber system to be joined or anchored to that plate.”  Id. at 1339 (citation omitted).

The jury concluded that the accused devices did not infringe the asserted claims, and that SK proved by clear and convincing evidence that the claims were invalid for lack of written description support for four limitations, including “plate including a plurality of openings.”  Synthes moved for judgment as a matter of law (JMOL) or new trial as to invalidity.  The district court denied-in-part Synthes’s motion, finding that SK had produced substantial evidence to support the jury’s conclusion that two limitations, including “plate including a plurality of openings,” lacked written description support, and were therefore invalid.

In a split opinion, the Federal Circuit affirmed the district court’s conclusion.  While broadening claims during prosecution is not improper, even to capture a competitor’s product, the broadened claims must be adequately supported by the specification.  Id. at 1341 (citing Liebel-Flarsheim Co. v. Medrad, Inc.,358 F.3d 898, 909 n.2 (Fed. Cir. 2004)).  The court reiterated that a “disclosure of a species may besufficient written description support for a later claimed genus including that species.”  Id. at 1344 (quoting Bilstad v. Wakalopulos, 386 F.3d 1116, 1124 (Fed. Cir. 2004)).  But if the difference between members of a species is such that a person skilled in the art would not readily discern that other species of the genus would perform similarly to the disclosed members, i.e., if the art is unpredictable, then disclosure of more species may be necessary to adequately show possession of the entire genus.  See id. (citing Bilstad, 386 F.3d at 1125).

Here, SK’s expert testified that there were “significant biomechanical property differences between using peripheral grooves and interior slots.”  Id. at 1342.  SK’s research and development manager also explained that SK began its development process with peripheral grooves and ended with internal slots, finding that the peripheral grooves and that the shape and location of the slots were important design decisions that affected the rate of wear on the system.  Id. at 1342-43.  He also noted that SK “had to overcome technical hurdles through its development process.”  Id. at 1343.  Synthes argued, in contrast, that the art in this case was not unpredictable and that “the ‘mechanical world’ is a ‘fairly predictable field.’”  See id. at 1345 (quoting Bilstad, 386 F.3d at 1126).  The court sided with SK and found “at least circumstantial evidence” that “the written description did not support the broad claim limitations in the asserted claims.”  Id. at 1343.  The court clarified that while Bilstad stated that the mechanical field was “fairly predictable,” it did not hold that “all inventions that may be characterized as ‘mechanical’ allow claiming a genus based on disclosure of a single species.”  Id. at 1345 (discussing Bilstad, 386 F.3d at 1126).

Writing in dissent, Judge Taranto concluded that SK failed to present the proof required to show an insufficient written description. Id. at 1348 (Taranto, J., dissenting).  To prevail on a written description challenge of structural claim language, the challenger must identify the differences between the claim language and the disclosed embodiments, and demonstrate, at a minimum, that the particular differences have a material effect on whether the products would achieve the aim of the claim at issue.  Id.  According to Judge Taranto, SK failed to prove that the difference between the claimed “openings” and the disclosed “grooves” had any material effect on the ability of the invented implants to fulfill their purpose to prevent sideways movement of the fibers, along the perimeter of the plate, as they hold the components of the implant together. Id. at 1349.

For patent drafters, Synthes is a reminder that describing several alternative common features, or a range of alternative representative species, can help ensure written description support for later-added genus claims.  This approach requires the inventor and the patent drafter to think about potential alternative embodiments of the invention when preparing the application.  From a litigation standpoint, the case also calls for careful analysis of the proposed claim construction.  While a broad construction may be useful to advance infringement theories, broad constructions can also make the claims more vulnerable to enablement and written description challenges, as well as to prior art challenges.  The case is also useful to remind practitioners in the mechanical arts that, while predictability of the art is generally not an issue that appears as prominently as in chemical or biotechnological cases, it should still be taken into account in considering the patentability of the claims.