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Reissue applications are important tools for correcting errors in U.S. patents. However, the decision whether to pursue a reissue application is non-trivial, as it requires surrendering the original patent and certifying that the patent owner believes the original patent to be wholly or partly inoperative or invalid. 35 U.S.C. § 251; M.P.E.P. § 1414.
When a reissued patent is eligible for Patent Term Extension (PTE) under 35 U.S.C. § 156, an additional consideration is whether the amount of PTE is properly calculated using the issue date of the original patent or the issue date of the reissued patent. In this article, we explore how the Federal Circuit, in Merck Sharp & Dohme B.V. v. Aurobindo Pharma USA, Inc., 130 F.4th 1363 (Fed. Cir. 2025), addressed that question in the context of a patent that was reissued solely to add narrower claims directed to an active pharmaceutical ingredient. In a companion article, we will consider how the Merck court's reasoning could apply where a patent holder seeks reissue on different grounds.
The '340 Patent and Merck's Application for PTE
Merck Sharp & Dohme B.V., Merck Sharpe & Dohme LLC, and their predecessors-in-interest ("Merck") owned U.S. Pat. No. 6,670,340 ("the '340 patent"). Merck, 130 F.4that 1366. The claims of the '340 patent were directed to 6-mercapto-cyclodextrin derivatives. Id. The '340 patent issued in April 2004, and, four months later, Merck applied to the FDA for approval of sugammadex, which was one of the 6-mercapto-cyclodextrin derivatives within the scope of the '340 patent's claims and the active ingredient in Merck's product BRIDION®. Id. at 1366-67.
While FDA review of sugammadex was pending, Merck filed an application to reissue the '340 patent. Id. at 1367. The reissue application retained the original claims and added narrower claims specifically reciting sugammadex. Id. The reissued patent was granted in January 2014 as RE44,733 ("the RE'733 patent") with those additional, narrower claims. Id. The FDA approved sugammadex in December 2015—nearly twelve years after the '340 patent issued. Id. Merck subsequently filed a PTE application for the RE'733 patent and received the maximum five-year PTE term based on the issue date of the '340 patent, extending the expiration date of the RE'733 patent from January 27, 2021, to January 27, 2026. Id.
District Court Litigation
After the RE'733 patent issued, several companies (collectively, "Aurobindo") filed Abbreviated New Drug Applications with the FDA seeking approval to sell generic versions of BRIDION®. Id. at 1367. Merck sued the companies for infringement of the RE'733 patent. Id. at 1368.
At trial, Aurobindo argued that the USPTO erred in calculating PTE based on the '340 patent's issue date. Id. According to Aurobindo, the plain text of 35 U.S.C. § 156(c) required the USPTO to calculate PTE based on the issue date of "the patent" for which PTE was sought, which, it argued, was the RE'733 patent. Id. Under that approach, the RE'733 patent would only receive 686 days of PTE, since only 686 of the 4,265-day FDA regulatory review period for sugammadex occurred after the RE'733 patent's issue date. Id.
The district court disagreed, reasoning that Aurobindo's construction of Section 156(c) would undermine the purpose of the Hatch-Waxman Act. Id. Instead, the district court concluded that "the patent" in Section 156(c) must refer to the original patent, not the reissued patent. Id.
The Federal Circuit's Analysis
The Federal Circuit affirmed the district court's reasoning that resolving the dispute required determining the meaning of the term "the patent" in Section 156(c), which reads, in part:
The term of a patent eligible for extension under subsection (a) shall be extended by the time equal to the regulatory review period for the approved product which period occurs after the date the patent is issued.
Id. at 1368-69 (emphasis in original).
The court viewed the language of Section 156(c), standing alone, as ambiguous, so it looked to the specific context in which the term "the patent" is used and the broader context of the statute as a whole. Id. at 1369. While the court stated that "Congress does not appear to have contemplated the situation presented by reissued patents in drafting" Section 156, the court nevertheless reasoned that the clear purpose of Section 156 is "to compensate pharmaceutical companies for the effective truncation of their patent terms while waiting for regulatory approval of new drug applications." Id. at 1370. The Merck court thus concluded that, in the context of reissued patents, the Hatch-Waxman Act "contemplates PTE for those patents and only those patents with claims directed to drug products whose period of exclusivity was delayed by FDA review." Id.
Applying that statutory purpose, the court reasoned that construing "the patent" in Section 156(c) to refer to the '340 patent compensates Merck for the period of exclusivity lost due to regulatory delay. Id. Conversely, adopting Aurobindo's construction would deny Merck compensation "for all but a small period of the delay," and the court did not believe the purpose of the Hatch-Waxman Act would be served "by disabling extensions of [an] unexpired term solely based on a patent holder's decision to seek reissue." Id.
Beyond Merck
Thus, in the context of a patent that already contained claims covering the approved drug product and that was reissued solely to add narrower claims to that drug product, the Merck court concluded that PTE is properly calculated using the issue date of the original patent, not that of the reissued patent. In doing so, the court expressly acknowledged that the addition of narrower claims may constitute a proper basis for seeking reissue. Merck, 130 F.4th at 1367, n.2 (citing In re Tanaka, 640 F.3d 1246, 1251 (Fed. Cir. 2011)).
However, a Patentee may pursue reissue to correct other defects, such as incorrect inventorship or potential invalidity of one or more original claims. Our next article will explore those scenarios in more detail and will examine them through the lens of Merck.
Read Part II here.
The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.
