A later-filed, later-issued, earlier-expiring child patent cannot be used as an obviousness-type double patenting (ODP) reference against its first-filed, first-issued, later-expiring parent patent having a common priority date. That was the holding from the Federal Circuit in its recent decision in Allergan USA, Inc. v. MSN Lab'ys Priv. Ltd., No. 2024-1061, 2024 WL 3763599 (Fed. Cir. Aug. 13, 2024). For patent owners, this hopefully provides a sense of certainty as they try to navigate the sometimes confusing and costly interplay between ODP and patent term adjustment (PTA).

One of the issues on appeal in this case was whether claim 40 of U.S. Patent No. 7,741,356 (the ’356 patent), the expiration date of which had been extended by 467 days due to PTA, was invalid on the grounds of ODP over certain claims from its “child” patents (U.S. Patent No. 8,344,011 (the ’011 patent) and U.S. Patent No. 8,609,709 (the ’709 patent), referred to collectively herein as “the reference patents”). The relationship between the ’356 patent and the reference patents is as follows:

Allergan conceded that claim 40 of the ’356 patent was not patentably distinct over the claims of the reference patents.

The court found that the claims of the reference patents are not proper ODP references that can be used to invalidate claim 40 of the ’356 patent. (Id. at *6). In reaching its decision, the court focused on the fact that the ’356 patent was the first patent to cover the claimed subject matter. The court stated, for example, that “[t]he ’356 patent is undoubtedly the ‘first’ patent to cover eluxadoline, whether we measure by filing date or by issuance date. And each of the ’011 and ’709 patents is unquestionably ‘second’ to that patent; neither of the applications leading to those patents was even filed until after the ’356 patent issued.” (Id. at *7). The court noted that it is the first-filed, first-issued patent in a family that sets the maximum period of exclusivity for the claimed subject matter and any patentably indistinct variants (id.), and therefore the court held 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.” (Id.).

In reaching its decision, the Federal Circuit made clear that its holding was specific to the facts of this case and suggested that the outcome may have been different had the ’356 patent not been the first patent to claim the subject matter at issue. The court stated, for example, that “the fact that the ’356 patent expires later is of no consequence here because it is not a ‘second, later expiring patent for the same invention.’” (Id.).

Of interest, the Federal Circuit distinguished its previous In re Cellect ruling. According to the court, In re Cellect “answered a different question than that at issue” in the Allergan case and is controlling in the Allergan case only to the extent that the expiration dates of the patents must be calculated:

Our holding in Cellect is only controlling in this case to the extent that it requires us to consider, in our ODP analysis, the ’356 patent’s June 24, 2026 expiration date (i.e., the expiration date after the addition of PTA), not the March 24, 2025 expiration date that it would have shared with the ’011 and ’709 reference patents in the absence of a PTA award. It does not follow, however, that the ’356 patent must be invalidated by the ’011 and ’709 reference patents simply because it expires later. Indeed, Cellect does not address, let alone resolve, any variation of the question presented here—namely, under what circumstances can a claim properly serve as an ODP reference—and therefore has little to say on the precise issue before us.

(Id. at *6; emphasis in original). And in a footnote, the Federal Circuit further addressed the scope of In re Cellect, stating that “Cellect did not involve the situation presented here of ODP with respect to a first-filed, first-issued patent. ... Cellect cannot be read as ‘confirming,’ much less holding, that a later-filed, later-issued, earlier-expiring claim is a proper ODP reference against a first-filed, first-issued, later-expiring claim having a common priority date.” (Id.).

Although this holding clarifies the interplay between ODP and PTA under these specific facts, there is little doubt that further fact patterns will arise – some that may clarify, and some that may add to the complexity of, the ODP space.

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