Case Name: CMP Development, LLC v. Amneal Pharms. LLC, Civ No. 21-549 (MN), 2023 WL 6387792 (D. Del. Sept. 29, 2023) (Noreika, J.)

Drug Product and Patent(s)-in-Suit: CaroSpir® (spironolactone); U.S. Patents Nos. 10,624,906 (“the ’906 patent”), 10,660,907 (“the ’907 patent”), and 10,888,570 (“the ’570 patent”)

Nature of the Case and Issue(s) Presented: CaroSpir is indicated for the treatment of heart failure, hypertension, and edema caused by cirrhosis. The patents-in-suit claim about 0.18% w/v to about 0.36% w/v of xanthan gum. Amneal argued that it did not infringe because it used tragacanth powder—not xanthan gum—as its suspending agent. After a two-day bench trial, the court found that CMP had not met its burden of proving infringement.

Why Amneal prevailed: The parties agreed that Amneal did not literally infringe, as Amneal’s product did not use xanthan gum. Rather, CMP argued that Amneal’s suspending agent—tragacanth powder—infringed the xanthan gum weight percent limitation under the doctrine of equivalents. Amneal did not contest that tragacanth powder performs substantially the same function to obtain substantially the same result as the recited xanthan gum. Instead, Amneal disputed that tragacanth powder worked in substantially the same way as xanthan gum.

CMP argued that tragacanth powder and xanthan gum work in substantially the same way because Amneal’s ANDA described a study examining four suspending agents and only tragacanth powder and xanthan gum prevented visually observable sedimentation. Other than this observation, CMP conducted no other scientific experiments to support its argument that each of the excipients work in substantially the same way. More particularly, the Court explained that “apart from his say-so and expertise as a polymer scientist, [CMP’s expert] offered no scientific support for the connection he made between … [the way] the two suspending agents work.” Conversely, Amneal argued that the suspending agents do not increase viscosity in substantially the same way. In particular, because of the presence of bassorin, tragacanth powder increases viscosity by a combination of swelling and polymer chain entanglement. It was undisputed that xanthan gum increases viscosity only by entanglement of dissolved polymer chains. Further, the amount of tragacanth powder in the ANDA product was 0.65% w/v, which was almost double the amount of xanthan gum recited in the patents-in-suit. CMP argued that due to the presence of bassorin, only 30-40% of the tragacanth powder will in fact be tragacanthin, and thus Amneal’s product infringed under the doctrine of equivalents. But the court found that there was no expert testimony or evidence to support this theory. In sum, there was no evidence that the amount of tragacanth powder in Amneal’s ANDA product is equivalent to the amount of xanthan gum in the patents-in-suit.