Xifaxan® (rifaximin)
Case Name: Norwich Pharms., Inc. v. Kennedy, Jr., No. 25-5137 (D.C. Cir. Aug. 25, 2026) (Circuit Judges Pillard, Walker, and Garcia presiding; Opinion by Garcia, J.) (Appeal from D.D.C., Howell, J.)
Drug Product and Patent(s)-in-Suit: Xifaxan® (rifaximin)
Nature of the Case and Issue(s) Presented: Actavis was the first applicant to submit an ANDA for 550 mg generic rifaximin and included Paragraph IV (“PIV”) certifications to patents covering the drug and its use to treat irritable bowel syndrome with diarrhea (“IBS-D”) and hepatic encephalopathy (“HE”). Actavis subsequently settled patent litigation with Salix and obtained a license permitting generic entry no earlier than January 1, 2028. While Actavis’s ANDA remained pending, Norwich submitted ANDAs for generic rifaximin and ultimately amended one of those ANDAs to seek approval for the 550 mg dosage. Norwich included PIV certifications to certain patents but submitted a section viii statement as to the HE patent, carving the HE indication out of its proposed label.
In January 2025, FDA determined that Norwich’s ANDA otherwise satisfied the requirements for approval but granted only tentative approval because Actavis remained entitled to 180-day first-applicant exclusivity. Norwich challenged that determination under the APA, arguing that Actavis had forfeited its exclusivity under the (i) “failure to market” and (ii) “failure to obtain tentative approval” statutory provisions of the Hatch Waxman Act. The district court rejected both arguments and granted summary judgment to FDA, Teva, and Salix. The D.C. Circuit affirmed with respect to former and remanded with respect to the latter.
Why Norwich Prevailed: The D.C. Circuit first affirmed FDA’s determination that Actavis had not forfeited its exclusivity for failure to market. Under § 355(j)(5)(D)(i)(I), forfeiture requires a specified triggering event to occur as to “each of the patents with respect to which the first applicant submitted and lawfully maintained a certification qualifying the first applicant for the 180-day exclusivity period.” Norwich argued that only Actavis’s PIV certifications that “matched” certifications in Norwich’s later ANDA should count for purposes of determining forfeiture. Because Norwich used a section viii carveout rather than a PIV certification for the HE patent, Norwich contended that the absence of a triggering event for that patent should not preserve Actavis’s exclusivity. FDA and Actavis, by contrast, argued that all PIV certifications lawfully maintained in Actavis’s first-filed ANDA were qualifying certifications.
The D.C. Circuit adopted FDA’s interpretation. It held that each PIV certification contained and lawfully maintained in a timely, substantially complete ANDA is “a certification qualifying the first applicant for the 180-day exclusivity period.” The D.C. Circuit emphasized that the statute provides a first applicant with a single, indivisible exclusivity period, rather than exclusivity that may be forfeited on a patent-by-patent or subsequent-applicant-by-subsequent-applicant basis. Norwich’s proposed “relational” approach would effectively permit Actavis to forfeit exclusivity as against Norwich while retaining exclusivity against another subsequent applicant whose ANDA contained a PIV certification to the HE patent—a form of partial forfeiture for which the court found no statutory basis. Because Actavis had submitted and lawfully maintained a PIV certification to the HE patent and no statutory triggering event had occurred as to that patent, Actavis had not forfeited its exclusivity under the failure-to-market provision.
Norwich prevailed, however, on its alternative argument that FDA applied the wrong legal standard in determining whether Actavis had forfeited exclusivity for failure to obtain tentative approval. Section 355(j)(5)(D)(i)(IV) provides that a first applicant forfeits exclusivity if it fails to obtain tentative approval within 30 months of filing, unless that failure “is caused by a change in or a review of the requirements for approval” imposed after the ANDA was filed. Actavis did not obtain tentative approval by its June 18, 2018, statutory deadline. FDA nevertheless concluded that Actavis retained exclusivity because FDA’s March 2017 rifaximin-specific draft guidance—which recommended additional dissolution studies—was “one of the causes” of the delay. FDA expressly determined that the statute did not require but-for causation.
The D.C. Circuit rejected FDA’s interpretation and held that “caused by” requires but-for causation. Accordingly, the exception applies only if Actavis would have timely obtained tentative approval absent the post-filing change in or review of FDA’s approval requirements. The D.C. Circuit rejected FDA’s proposed “multiple sufficient causes” approach, reasoning that such an exception is generally reserved for unusual circumstances in which strict but-for causation would produce perverse results, such as independently sufficient acts of multiple wrongdoers. In the ANDA context, by contrast, FDA’s approach could allow a fundamentally deficient application to retain 180-day exclusivity merely because FDA happened to impose an additional requirement before the 30-month deadline—even where the applicant could not have obtained tentative approval regardless of that change. The D.C. Circuit found no indication that Congress intended such a result.
The court declined to decide whether FDA’s March 2017 guidance—or some other post-filing change or review of FDA requirements—was in fact a but-for cause of Actavis’s failure to obtain tentative approval. Because FDA had never applied the proper causation standard and the record before the court did not include Actavis’s ANDA record, the D.C. Circuit concluded that FDA should conduct that analysis in the first instance.
