Originally published on 12/20/2024, updated on 12/23/2024 to reflect updates pertaining to Teva v. Amneal.
Over the past twelve months, the Federal Circuit has issued a number of noteworthy decisions that will impact litigation strategy and business planning. Several of those cases pertain particularly to cases brought under the Hatch-Waxman Act. Here, Taft provides a brief overview of a few key Hatch-Waxman decisions from 2024.
Salix v. Norwich: Polymorph Patent Claims Are Susceptible to Obviousness Challenges
About the case
In April, the Federal Circuit breathed new life into the use of obviousness challenges to claims drawn to a drug compound's solid state form.
At issue in Salix Pharmaceuticals Ltd. v. Norwich Pharmaceuticals Inc., 98 F.4th 1056 (Fed. Cir. 2024), was Norwich's proposed generic version of rifaximin, which is the active ingredient in Salix's commercial product Xifaxan', used to treat hepatic encephalopathy (HE) and irritable bowel syndrome with diarrhea (IBS-D). Id. at 1059-60. Salix asserted patents directed to methods of treating HE, patents directed to methods of treating IBS-D, and patents directed to a solid form of rifaximin, namely form β. Id. at 1060. Following the trial, the district court found the HE patents infringed and not invalid, and the IBS-D and polymorph patents infringed but invalid as obvious.
What did the court decide?
Relevant to this discussion, on appeal, Salix argued that the district court clearly erred in finding that a person of ordinary skill in the art would have had a reasonable expectation of success in obtaining the claimed rifaximin form β. Id. at 1064. Salix pointed to several prior Federal Circuit decisions finding polymorph claims non-obvious, including Grunenthal GmbH v. Alkem Laboratories Ltd., 919 F.3d 1333 (Fed. Cir. 1999), and Pharmacyclics LLC v. Alvogen, Inc., No. 2021-2270, 2022 WL 16943006 (Fed. Cir. Nov. 15, 2022). Those cases, as well as previous polymorph decisions, had seemed to render obviousness arguments difficult, to say the least, given the purported unpredictability of polymorph formation and preparation.
In Salix, the key prior art reference disclosed that "rifaximin exists in crystalline form," and although that reference did not "discuss rifaximin's crystal structure in detail," it "does disclose several preparation protocols for rifaximin that include solvents used for crystallization." Id. at 1064. Relying on expert testimony, the district court held that a person of ordinary skill in the art would have had reason to characterize the crystalline rifaximin obtained from the prior art protocols, that such characterization was routine, and that doing so would have led the person of ordinary skill to detect the claimed form. Id. at 1065. The court found no clear error by the district court. The court acknowledged and discussed Grunenthal and Pharmacyclics, both of which found no clear error in a district court finding of non-obviousness, but it distinguished those cases. Quoting Grunenthal, the court reiterated the fact-heavy analysis that undergirds polymorph obviousness considerations and returned to the teaching of the prior art: "In Grunenthal and Pharmacyclics, the issue was whether a skilled artisan would have had a reasonable expectation of success in producing a crystalline form of a compound[,] . . . Here, the prior art included a process to produce a crystalline form of rifaximin, and the dispute centered around characterizing the crystalline form resulting from that process." Id. at 1065 (citations omitted; italics in original).
Implications for polymorph claim obviousness arguments
Salix breathes new life into polymorph claim obviousness arguments, as it reaffirms that, as a practical matter, polymorph claims are susceptible to obviousness challenges. Salix also highlights the need for a carefully crafted litigation strategy. Conventional wisdom had suggested that anticipation and obviousness challenges to polymorph patents are served by testing of material reproduced following prior art teachings. That reproduction and testing are not required by Salix, though advocates and experts will be wise to present the teachings of the prior art in a compelling fashion in order to analogize either to Salix on the one hand or Grunenthal and Pharmacyclics on the other.
Amarin v. Hikma: Public Statements Can Have a Major Impact on Carve-Out Analysis
About the case
In June, the Federal Circuit illuminated the state of the law with respect to so-called "skinny labels," in which an ANDA applicant attempts to carve out label...
