The U.S. Court of Appeals for the Federal Circuit delivered a significant victory for pharmaceutical patent holders on August 13, 2024, reversing a district court's invalidation of Allergan's patent claims covering eluxadoline, the active ingredient in Viberzi® used to treat irritable bowel syndrome with diarrhea (IBS-D). The decision in Allergan USA, Inc. v. MSN Laboratories Private Ltd. clarifies critical aspects of obviousness-type double patenting (ODP) doctrine and written description requirements.
Key Patent Ruling on Double Patenting
The Federal Circuit established a narrow but important precedent, holding that "a first-filed, first-issued, later-expiring claim cannot be invalidated by a later-filed, later-issued, earlier-expiring reference claim having a common priority date." This ruling directly addressed the complex interplay between Patent Term Adjustment (PTA) and the ODP doctrine.
The case centered on claim 40 of U.S. Patent No. 7,741,356 (the '356 patent), which was issued in 2010 and claimed eight chemical compounds, including eluxadoline. The District of Delaware had invalidated this claim under ODP doctrine because it was not patentably distinct from claims in later-filed U.S. Patents No. 8,344,011 and 8,609,709, which expired earlier than the '356 patent due to PTA differences.
The '356 patent received a longer term because it was awarded PTA due to delays caused by the U.S. Patent and Trademark Office during prosecution, extending its expiration to June 24, 2026, while the related patents expired on March 24, 2025.
Clarification of Cellect Precedent
The Federal Circuit corrected the district court's interpretation of its previous decision in In re Cellect, explaining that the lower court had misapplied the precedent. The court noted that "Cellect answered a different question than that at issue here" and emphasized that the purpose of ODP doctrine "is to prevent patentees from obtaining a second patent on a patentably indistinct invention to effectively extend the life of a first patent to that subject matter."
As the first-filed and first-issued patent in its family, the '356 patent "sets the maximum period of exclusivity for the claimed subject matter and any patentably indistinct variants," according to the Federal Circuit. The court emphasized that the extended term due to PTA did not unjustly extend Allergan's monopoly since it was the foundational patent in the family.
Written Description Requirements Clarified
The Federal Circuit also reversed the district court's invalidation of claims in four related patents (U.S. Patents Nos. 11,007,179, 11,090,291, 11,160,792, and 11,311,516) for lack of written description. These patents contained claims directed to pharmaceutical formulations of eluxadoline without a "glidant" - an inactive ingredient that appeared in all detailed embodiments described in the patents' specifications.
The district court had concluded that the patents failed to meet written description requirements because they "claimed, but did not adequately disclose, formulations of the drug product without a glidant." However, the Federal Circuit found this analysis flawed, noting that the patents' general description included formulations comprising eluxadoline "and an inert ingredient selected from" a list that included both glidants and non-glidant ingredients.
Distinguishing ICU Medical Precedent
The Federal Circuit distinguished this case from its previous decision in ICU Medical, Inc. v. Alaris Medical Systems, Inc., where a patent claiming a "spikeless" valve was invalidated because the specification only described valves with spikes that performed essential functions. Here, the court noted that while glidants appeared in detailed embodiments, the patents "attribute no particular function or significance to the glidant" and the specification contemplated formulations both with and without glidants.
The court rejected expert testimony suggesting that inclusion of glidants in disclosed formulations would signal their necessity, explaining that such testimony was "untethered to the inventors' own description of the invention" and would "improperly take the written description inquiry outside the four corners of the specification."
Implications for Patent Strategy
This decision provides important guidance for pharmaceutical companies managing patent portfolios with multiple related applications. The ruling clarifies that applicants are entitled to PTA awarded for USPTO delays during prosecution of first-filed patent applications, regardless of when the patent issues or how long the PTA extends the patent term.
The Federal Circuit recognized that first-filed applications often require "greater time and effort by the applicant and examiner alike" and thus are often awarded PTA, whereas later-filed continuing applications "proceed much more efficiently through prosecution" and receive little or no PTA. This decision removes the risk of ODP invalidation based solely on expiration date comparisons when the first-filed patent receives PTA.
Hatch-Waxman Context
The case arose under the Hatch-Waxman Act framework, where MSN Laboratories filed an Abbreviated New Drug Application seeking FDA approval to market a generic version of Viberzi®. MSN included a Paragraph IV certification asserting that Allergan's patents were invalid, unenforceable, or not infringed. Following a three-day bench trial focused solely on patent validity after MSN stipulated to infringement, the District of Delaware initially ruled in favor of MSN on both ODP and written description grounds.
The Federal Circuit's reversal on both issues represents a significant win for Allergan and establishes important precedents for future patent disputes involving PTA and written description requirements in pharmaceutical cases. The decision emphasizes that ODP analysis must consider the full factual context, including filing dates, issuance dates, and priority relationships between related patents.
