Judge Michel, Other Amici File Briefs Opposing Sandoz’s Fourth Circuit Appeal in Enbrel Antitrust Case

This week, several amicus briefs were filed at the U.S. Court of Appeals for the Fourth Circuit supporting defendant-appellees Amgen in an antitrust suit brought by rival pharmaceutical firm Sandoz, which is appealing the dismissal of its complaint by the Eastern District of Virginia. Amici, including former Federal Circuit Chief Judge Paul Michel, free market institute Washington Legal Foundation, and trade organizations representing the pharmaceutical industry, all strongly urge the Fourth Circuit to dismiss Sandoz’s attempt to circumvent adverse patent rulings with an overly broad antitrust theory that would disrupt the entire U.S. patent system.

The Fourth Circuit appeal follows Sandoz’s complaint filed April 2025 in Eastern Virginia district court alleging violations of the Sherman Act caused by Amgen’s extension of market exclusivity for the inflammatory disease treatment etanercept, which Amgen markets as Enbrel, through patent acquisitions and filings. This February, the district court granted Amgen’s motion to dismiss. The district court found that Amgen’s patent prosecution and enforcement activities were protected under Noerr-Pennington doctrine as government petitioning conduct immune from antitrust liability.

Further, the district court ruled that Sandoz’s antitrust claims as to 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 ruling by the Federal Circuit 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.

Judge Paul Michel: Murky Mercoid Should Allow Collateral Attack on Final Judgment

Former Federal Circuit Chief Judge Paul Michel filed a brief supporting Amgen 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.

Sandoz’s appeal raised several policy points under the U.S. Supreme Court’s 1944 ruling in Mercoid Corp. v. Mid-Continent Investment Co., but these were undermined by Judge Michel’s brief. Although district courts often bifurcate patent cases from related antitrust claims, this is typically done to avoid jury confusion, or because resolution of underlying patent claims renders antitrust claims moot. While not every antitrust claim is intertwined with patent law issues, bifurcation does not indicate that claims should be litigated separately, especially when they are compulsory counterclaims to patent infringement allegations as in the present appeal.

Sandoz also cited the Ninth Circuit’s 1995 ruling in Hydranautics v. FilmTec Corp. to argue that its antitrust counterclaims were merely permissive. However, Judge Michel countered that Hydranautics misstated Congress’ intent in creating the Federal Circuit by suggesting that antitrust claims should instead be answered by regional circuit courts. The Federal Circuit’s approach in applying regional circuit law on antitrust claims accomplishes the uniformity in patent law Congress intended while avoiding Sandoz’s misplaced concern on generating circuit splits on antitrust law, Michel argued.

While Sandoz seeks a broad application of Mercoid, Judge Michel highlighted that the case’s holding on the permissive nature of antitrust counterclaims in the patent context has been recognized as murky by regional circuit courts. Significant lingering questions on Mercoid noted by legal scholars have led to various interpretations that undercut the strong policy interest of innovation certainty. Sandoz’s collateral attack on the outcome of previous patent litigation undermines confidence in the innovation marketplace, which the Federal Circuit was created to avoid according to Michel.

PhRMA and BIO: Noerr-Pennington Eliminates Essential Element of Injury from Antitrust Claim

Filing a joint amicus brief, the Pharmaceutical Research and Manufacturers of America (PhRMA) and Biotechnology Innovation Organization (BIO) also attacked Sandoz’s interpretation of Mercoid, an approach the district court properly declined without evidence of patent misuse. Further, the trade organizations argue that Mercoid is distinguishable because the complaint in that case did not demand a declaratory judgment on patent enforceability or license agreements.

Sandoz’s claim that Amgen engaged in an anticompetitive scheme to acquire patent rights from Roche is materially similar to Sandoz’s argument in the prior case that the Patent Act prevented Amgen from acquiring patents to extend protection over Enbrel. Jettisoning the compulsory counterclaim rule, which exists to preserve finality in court judgments, would double litigation in the biopharmaceutical and biotech industries while overriding Federal Rule of Civil Procedure 13(a), which requires parties to bring counterclaims that arise out of the same transaction or occurrence as the act forming the lawsuit’s basis.

PhRMA and BIO bristled at the Eastern Virginia district court’s adoption of erroneous conclusions from related CareFirst cases, which concluded that Amgen was not immune from antitrust liability for purchasing Roche’s patents. 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, activities the U.S. patent system was designed to encourage.

Washington Legal Foundation: Mercoid’s Unusual Facts Leads to Limited Application

The Washington Legal Foundation, which regularly appears as amicus to defend patent owners’ rights in the face of antitrust challenges, also argued that Sandoz’s Sherman Act claim is an invalid collateral attack on the Federal Circuit’s final judgment in Immunex, which already addressed whether Amgen improperly extended its exclusive rights to the etanercept molecule.

Tracing the unusual facts behind Mercoid, in which the Court dismissed antitrust claims against a home furnace manufacturer that defended a previous patent infringement case against a homeowner installing the accused furnace system, Washington Legal Foundation noted that other circuit courts have limited their application of the Court’s holding in that case. Even setting aside dispositive procedural issues, 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, amici argued.