Merck Research Laboratories in South San Francisco, California

Pictured: Merck research laboratories in California/iStock, hapabapa

Merck in an SEC filing disclosed on Monday that Hikma Pharmaceuticals U.S. is seeking the FDA’s approval for its generic version of the muscle relaxant reversal injection Bridion (sugammadex) prior to the drug’s patent expiration.

Hikma notified Merck of its intention on Feb. 5, 2024, according to the SEC filing. The British pharma is making its regulatory request under the Hatch-Waxman Act—also known as the Drug Price Competition and Patent Term Restoration Act of 1984—which established the approval pathway for generics.

Specifically, Hikma is seeking approval for its Bridion copycat through a Paragraph IV Patent Certification letter, which according to the FDA’s website allows the approval of generics given that the patent for its reference product is “invalid, unenforceable, or will not be infringed by the generic product.”

Under the Paragraph IV process, Merck has 45 days from being notified of the patent challenge to file an infringement suit against Hikma. While the court resolves the complaint, the FDA’s approval for the generic product is generally postponed for 30 months, unless the patent expires or a judge decides against the patent holder before then.

Merck is “currently considering its options,” according to its SEC filing.

Bridion is a modified gamma cyclodextrin that works by diffusing through the patient’s plasma and capturing the neuromuscular blocking agents rocuronium and vecuronium. The injectable drug first won the FDA’s approval in 2015 for use in adults undergoing surgery. It carries warnings against anaphylaxis and bradycardia, while its most common adverse events include vomiting, pain and nausea.

The drug is one of Merck’s top-selling assets—and is still showing signs of growth. In 2023, Bridion brought in a little more than $1.84 billion, an increase from nearly $1.69 billion in revenue in 2022 and $1.53 billion in 2021, according to the SEC filing.

In June 2023, the U.S. District Court for the District of New Jersey ruled in favor of Merck, finding that the company had correctly calculated its Patent Term Extension duration for Bridion. The court ruling protects Bridion from generic competition in the U.S. through at least January 2026. Bridion’s protections have already expired in the EU, in Japan and in China.

At the time, Merck General Counsel Jennifer Zachary in a statement said that the decision will ultimately allow the company “to continue investing in research and development,” bringing new and innovative treatments to patients with unmet medical needs.