In a significant ruling for pharmaceutical patent holders, the U.S. Court of Appeals for the Federal Circuit has affirmed that patent term extensions (PTE) for drug products under regulatory review should be calculated based on the issue date of the original patent, not the reissue patent.
The March 13, 2025 decision in Merck Sharp & Dohme B.V. et al. v. Aurobindo Pharma USA, Inc. et al. upholds a district court ruling that granted Merck a full five-year patent term extension for its sugammadex patent, extending protection for its BRIDION® product through January 2026.
Case Background
Merck's original U.S. Patent No. 6,670,340 ('340 patent) covering 6-mercapto-cyclodextrin derivatives was issued on December 30, 2003. Shortly after, on April 13, 2004, Merck applied to the FDA for approval of sugammadex, the active ingredient in BRIDION®, which is used to reverse neuromuscular blockade during certain surgical procedures.
While sugammadex was still under FDA review, Merck filed a reissue application that included both the original claims and additional narrower claims specifically directed to sugammadex. This reissue patent (RE'733) was granted on January 28, 2014, and the FDA finally approved sugammadex on December 15, 2015.
The U.S. Patent and Trademark Office (PTO) granted Merck's request for a five-year patent term extension—the maximum allowed under 35 U.S.C. § 156(c)—based on the '340 patent's original issue date, extending protection until January 27, 2026.
The Legal Dispute
Aurobindo, which had submitted an Abbreviated New Drug Application (ANDA) for a generic version of BRIDION®, challenged the PTE calculation. They argued that the PTO should have calculated Merck's PTE based on the issue date of the reissue patent rather than the original patent.
Under Aurobindo's interpretation, Merck would have been entitled to only 686 days of PTE (the period between the reissue patent's January 28, 2014 issue date and FDA approval), rather than the full five years. This would have reduced the patent's protection by approximately 1,140 days, with an earlier expiration date of December 14, 2022.
The Court's Reasoning
The Federal Circuit rejected Aurobindo's argument, finding that the term "patent" as used in Section 156(c) refers to the original patent, not the reissued patent. The court emphasized that this interpretation aligns with the purpose and legislative intent of the Hatch-Waxman Act, which was "to compensate pharmaceutical companies for the effective truncation of their patent terms while waiting for regulatory approval of new drug applications."
"The statute contemplates a patentee receiving time lost in its patent term by reason of FDA delay, and the statute should be liberally interpreted to achieve this end," the court stated. It noted that Aurobindo's construction would "deny Merck compensation for all but a small period of the delay," contradicting the statute's purpose.
The court concluded that "a reissued patent is entitled to PTE based on the original patent's issue date where, as here, the original patent included the same claims directed to a drug product subject to FDA review."
Implications for Pharmaceutical Patents
This ruling maintains the status quo for how the USPTO calculates PTE based on FDA regulatory review periods. It provides important clarity for pharmaceutical companies that might consider filing reissue patents while their products are under regulatory review.
Dr. Sarah Johnson, a patent attorney specializing in pharmaceutical intellectual property, commented on the decision: "This ruling is significant because it allows innovator companies to pursue reissue patents to refine their claims without jeopardizing their patent term extension eligibility. Had the court ruled differently, companies might have been forced to choose between filing potentially valuable reissue applications and preserving their full PTE."
The Federal Circuit also noted that its analysis aligns with the PTO's Manual of Patent Examining Procedure, which instructs examiners to calculate PTE for reissued patents based on the original patent's issue date, provided both patents claim the approved product.
Important Caveat for Patent Owners
The court emphasized that its decision applies specifically to reissue patents that maintain the original claims covering the drug product under regulatory review. Patent owners should be cautious about canceling claims in reissue applications, as doing so could result in forfeiture of PTE if the canceled claims cover the drug product under review.
The Federal Circuit did not address how PTE should be calculated when a reissue patent significantly modifies the scope of the original claims without canceling them, leaving this as an open question for future cases.
This decision represents a significant win for innovator pharmaceutical companies, preserving the intended compensation for regulatory delays and maintaining predictability in patent term extension calculations for reissue patents.
