The Federal Circuit held, in In re Cellect, LLC, 81 F. 4th 1216 (Fed. Circuit 2023), that obviousness-type double patenting (ODP) is analyzed based on an expiration date after patent term adjustment (PTA) is applied.  During reexamination, asserted claims from four related patents were found to be unpatentable under ODP with respect to a reference patent of the same family that did not receive PTA, and thereby had an earlier expiration date.  The opinion noted an ODP determination depends on “whether the claims of a later-expiring patent would have been obvious over the claims of an earlier-expiring patent owned by the same party.”  As the asserted claims expired after the reference patent, the claims were found to be unpatentable under ODP.

In a subsequent opinion, the Federal Circuit held, in Allergan USA, Inc. v. MSN Laboratories Private Ltd and Sun Pharmaceutical Indus. Ltd., No. 2024-1061 (Fed. Cir. 2024) 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.  In Allergen, the first-filed patent of a patent family received PTA, and thereby had a later expiration date than two related patents.  The opinion in Allergen noted the first-filed patent was first by filing date and first by issuance date, and that it therefore “does not extend any period of exclusivity on the claimed subject matter.”  Therefore, the opinion found that a first-filed member of a patent family cannot be used to invalidate related members of the same family.  In this regard, the decision in Allergen created an ODP safe-harbor for first-filed members of a patent family with respect to related patents.

The opinions in Cellect and Allergan highlight the importance of properly addressing double patenting issues, particularly in view of possible technical ambiguities that may arise due to PTA when terminal disclaimers are not filed.  Therefore, it is important to monitor for possible double patenting issues, particularly in complex patent families with multiple branches, to avoid subsequent findings of unpatentability.