Antitrust Battle Over Enbrel Monopoly Escalates as Amici Clash in Fourth Circuit Appeals
核心洞察
Amgen faces antitrust challenges over its alleged use of acquired Roche patent rights to extend Enbrel's market exclusivity until 2029, blocking lower-cost biosimilar competitors.
The Open Markets Institute (搜索) filed an amicus brief urging the Fourth Circuit to allow the CareFirst v. Amgen lawsuit to proceed, arguing acquisitions of pending patents can constitute illegal monopolization under the Sherman Act.
Sandoz's separate antitrust appeal was dismissed by the Eastern District of Virginia, which found Amgen's patent enforcement protected under Noerr-Pennington doctrine and barred as a compulsory counterclaim.
A high-stakes legal confrontation over the blockbuster biologic Enbrel (etanercept) has intensified at the U.S. Court of Appeals for the Fourth Circuit, where competing amicus briefs now frame a pivotal question: whether a dominant pharmaceutical company can use acquired patent rights to extend its monopoly and keep lower-cost biosimilar competitors off the market.
Enbrel, a biologic drug used to treat rheumatoid arthritis (搜索) and other autoimmune conditions, generates billions of dollars in annual revenue for Amgen. At the center of the dispute is Amgen's alleged acquisition of pending patent applications related to the drug from Roche, roughly two years after Amgen obtained rights to Enbrel through its 2002 buyout of Immunex (搜索). These patent rights were subsequently used to prevent biosimilar competitors from entering the market until 2029.
Open Markets Urges Court to Allow Antitrust Challenge
The Open Markets Institute (搜索) filed an amicus brief urging the Fourth Circuit to allow an antitrust lawsuit, CareFirst v. Amgen, to proceed. The lawsuit challenges Amgen's use of acquired patent rights to extend its monopoly over Enbrel, arguing that this alleged strategy can constitute illegal monopolization under Section 2 of the Sherman Act, which prohibits companies from acquiring or maintaining monopoly power through exclusionary conduct, including acquisitions of assets such as patents and pending patents.
"Patent law is supposed to reward innovation, not provide a playbook for monopolists to buy up potential threats and perpetuate their dominance," said Tara Pincock, Policy Counsel at the Open Markets Institute (搜索). "When a dominant pharmaceutical company acquires patent rights and uses them to extend an existing monopoly, antitrust law has a critical role to play. Patients should not be forced to pay monopoly prices for years longer because a powerful corporation found another way to block competition."
The brief argues that if Roche had retained the patent rights, it likely would have licensed them to other companies or used them to enter the Enbrel market itself. Instead, Amgen allegedly acquired those rights and used them to erect barriers against biosimilar competitors, extending its monopoly until 2029. The resulting exclusion has cost patients and payors billions of dollars in potential savings, the brief contends.
A federal district court rejected Amgen's attempt to dismiss the lawsuit in September 2025. Amgen is now asking the Fourth Circuit to reverse that ruling and terminate the case, while Open Markets urges the appeals court to affirm the lower court and allow the antitrust challenge to proceed.
Pending Patents Carry Competitive Significance
Open Markets further argues that pending patent applications have genuine economic and competitive significance even before patents are formally granted. Companies license pending patents and use them as collateral to obtain credit precisely because they may ultimately confer the power to exclude competitors. In Amgen's case, the acquisition allegedly paid off: the applications ultimately produced valuable patents that helped keep biosimilar competitors out of the Enbrel market for years.
"Amgen's alleged conduct illustrates exactly why courts must look at how monopolists actually maintain their power," said Sandeep Vaheesan, Legal Director at the Open Markets Institute (搜索). "A monopolist should not be able to purchase assets that could otherwise enable competition and use them to build a moat around its monopoly. Antitrust law has long prohibited acquisitions used to exclude rivals, and pending patent rights should be no exception."
Sandoz's Appeal and the Noerr-Pennington Defense
A parallel antitrust suit brought by rival pharmaceutical firm Sandoz has taken a different trajectory. Sandoz filed its complaint in April 2025 in Eastern Virginia district court, alleging violations of the Sherman Act caused by Amgen's extension of market exclusivity for etanercept through patent acquisitions and filings. In February, the district court granted Amgen's motion to dismiss, finding that Amgen's patent prosecution and enforcement activities were protected under Noerr-Pennington doctrine as government petitioning conduct immune from antitrust liability.
The district court also ruled that Sandoz's antitrust claims regarding Amgen's acquisition of patents from Roche should have been raised as a compulsory counterclaim in prior patent infringement proceedings between the parties. That infringement suit resulted in a July 2020 Federal Circuit ruling affirming that Sandoz had failed to show that patent claims covering Enbrel were invalid for obviousness-type double patenting, preventing Sandoz from marketing Erelzi, its biosimilar version of Enbrel.
Industry Amici Warn Against Disrupting the Patent System
Several amicus briefs filed in support of Amgen strongly urge the Fourth Circuit to dismiss Sandoz's appeal, warning that its broad antitrust theory would disrupt the entire U.S. patent system.
Former Federal Circuit Chief Judge Paul Michel filed a brief arguing that Sandoz's collateral attack on validly enforced patent rights threatens the vitality of the innovation ecosystem. While patent law is the only personal right enshrined in the U.S. Constitution, Michel highlighted that antitrust law plays a complementary role that encourages competition when properly coordinated with patent law. Michel contended that Sandoz's collateral attack on the outcome of previous patent litigation undermines confidence in the innovation marketplace.
The Pharmaceutical Research and Manufacturers of America (PhRMA (搜索)) and Biotechnology Innovation Organization (BIO) filed a joint amicus brief attacking Sandoz's interpretation of the Supreme Court's 1944 ruling in Mercoid Corp. v. Mid-Continent Investment Co. The trade organizations argue that Noerr-Pennington doctrine forbids activity pre-dating government action from serving as the predicate for antitrust liability because it eliminates the causation of injury, an essential element of antitrust claims. Advancing a rule that would transform patent enforcement injuries into antitrust exposure would chill patent enforcement and licensing in the biopharmaceutical industry, they warned.
The Washington Legal Foundation also argued that Sandoz's Sherman Act claim is an invalid collateral attack on the Federal Circuit's final judgment in Immunex (搜索), which already addressed whether Amgen improperly extended its exclusive rights to the etanercept molecule. Even setting aside dispositive procedural issues, the foundation argued, Sandoz's antitrust claims fail because neither acquiring patents nor the Federal Circuit's ruling upholding patent validity qualifies as exclusionary conduct under the Sherman Act.
The Fourth Circuit's resolution of these competing arguments will carry significant implications for the biopharmaceutical industry, shaping the boundaries between patent rights and antitrust liability in the context of biosimilar competition.