Hatch-Waxman PTE for Reissue Patents Should Be Calculated From the Original Patent’s Issue Date

On March 13, 2025, the United States Court of Appeals for the Federal Circuit issued a decision about Patent Term Extensions (PTEs) under the Hatch-Waxman Act for reissue patents. In Merck Sharp & Dohme B.V. v. Aurobindo Pharma USA, Inc. (No. 2023-2254), the Court confirmed that the PTE provision under 35 U.S.C. § 156 refers to the original patent’s issue date, not the reissue patent’s issue date. Thus, the issue date of the original patent should be used when calculating the extension period.

35 U.S.C. § 156 provides a process for extending patent terms by up to five years to compensate patent owners for time lost during the regulatory review of new drug applications. The formula for calculating PTE is set forth in subsection 156(c), and includes the statement that “[t]he term of a patent ... shall be extended by the time equal to the regulatory review period ... occur[ring] after the date the patent is issued.” [emphasis added] The Court’s decision hinged on whether the term “the patent” in subsection 156(c) refers to the original patent or the reissue patent. Using the issue date of the reissued patent would usually result in shorter PTE because any review that occurs before the issue date does not affect PTE.

Merck owned the original patent, U.S. Patent No. 6,670,340, issued on December 30, 2003, for a class of 6-mercapto-cyclodextrin derivatives. A few months after the original patent was issued, Merck applied for FDA approval of sugammadex (an active ingredient in BRIDION® for the treatment of paralysis), which was covered by the claims of the ‘340 patent. While awaiting FDA approval for sugammadex, Merck filed a reissue application with the USPTO that retained the claims of the original patent and added additional claims directed specifically to sugammadex. The original patent was reissued as U.S. Patent No. RE44,733 on January 28, 2014.

Sugammadex received FDA approval on December 15, 2015, nearly twelve years after the original patent’s issue date and about two years after the reissued patent’s issue date. Merck applied for the maximum five-year PTE for the reissued patent, based on the original patent’s issue date. The USPTO granted the PTE, extending the reissued patent’s expiration from January 27, 2021, to January 27, 2026.

After the original patent reissued and around the time the FDA granted Merck's PTE application, Aurobindo filed an Abbreviated New Drug Application, along with Paragraph IV certifications, seeking FDA approval to market a generic version of BRIDION®. In response, Merck sued Aurobindo for patent infringement under 35 U.S.C. § 271(e)(2)(A) in the District of New Jersey.

During the pendency of the district court case, the issues were narrowed to the patent term extension. Prior to trial, the defendants withdrew all invalidity defenses. At trial, Aurobindo argued that the RE’733 patent was not entitled to a five-year PTE and had therefore expired. It argued that the PTO erred in calculating the RE’733 patent’s PTE based on the ’340 patent’s original issue date, urging that the plain text of subsection 156(c) required the PTO to calculate PTE based on the issue date of “the patent” for which PTE was sought: the RE’733 patent. The district court disagreed, finding that Aurobindo’s construction of subsection 156(c) would undermine the purpose of the Hatch-Waxman Act, and holding that the PTE was properly calculated using the original patent’s issue date. Aurobindo appealed to the Federal Circuit.

The sole issue on appeal was whether a PTE for a reissued patent should be calculated based on the issue date of the original patent or the reissued patent. Aurobindo argued that, under subsection 156(c)’s plain meaning, “the patent” refers to the reissued patent, since “the ‘patent eligible for extension’ is the [reissued] patent.” Merck urged the opposite interpretation, arguing that subsection 156(c)'s “text, together with other patent statutes and the history of patent reissue, demonstrate that [subs]ection 156(c) refers to the original issue date.” The USPTO filed a brief in support of Merck.

The court sided with Merck, concluding that the term “the patent” in 35 U.S.C. § 156(c) refers to the original patent. The court explained that the meaning of the term “patent” as used in subsection 156(c) was ambiguous but should be interpreted in a manner consistent with the Hatch-Waxman Act’s purpose. The court noted construing subsection 156(c) as using the original patent's issue date to calculate the PTE fulfills the Hatch-Waxman Act's purpose of compensating pharmaceutical companies for patent term lost due to the regulatory approval process for new drugs. Under these circumstances, the RE’733 patent was entitled to a five-year PTE based on the ’340 patent’s issue date, since regulatory review effectively prevented the patent owner from enforcing the patent during that period.

As a result of this ruling, a reissue patent that includes the original patent’s claims that were directed to a drug product subject to FDA review will be eligible for the full benefit of a PTE based on the original patent’s issue date. The Federal Circuit’s decision only applies to reissue patents that include the same claims as the original patent. Thus, patentees should carefully consider if they want to cancel the claims in a reissue patent application that cover the drug under regulatory review, as doing so could result in forfeiture of PTE. Note that the Federal Circuit did not address how PTE should be calculated when a reissue patent modifies the scope of the original claims but does not cancel them.