Antitrust Law Daily Wrap Up, ANTITRUST NEWS: Amicus briefs support affirming dismissal of Sandoz suit over Enbrel patent misuse, (Jul 14, 2026)

By Thomas K. Lauletta, J.D.

The briefs argue that Sandoz should be able to recast its unsuccessful patent validity challenge as a Section 2 Sherman Act claim.

Three amicus briefs were filed with the U.S. Court of Appeals for the Fourth Circuit in support of the district court decision granting Amgen’s motion to dismiss Sandoz’s suit alleging that Amgen, utilizing its Enbrel patent for treating arthritis, illegally prevented competitors from manufacturing biosimilar arthritis drugs (Sandoz Inc. v. Amgen Inc., No. 26-1309 (4th Cir. Jul. 6, 2026)).

Approximately eight years ago a district court upheld Amgen’s patent in Embrel in a suit brought by Sandoz. Subsequently, in 2025, Sandoz filed a lawsuit alleging that Amgen used its patent to illegally impose antitrust barriers to generic drug manufactures keeping them from marketing biosimilar drugs for treating arthritis and other inflammatory diseases. The federal district court in Norfolk dismissed Sandoz’s antitrust claims for failure to state a claim.

Three amicus briefs have been now been filed with the Court of Appeals for the Fourth Circuit arguing that the district court decision should be affirmed. The amicus briefs raise similar arguments, notably that Federal Rule 13(a) bars Sandoz’s antitrust claims because they constitute compulsory counterclaims that should have been raised in its suit to invalidate Amgen’s Enbrel patent.

Pharmaceutical Research and Manufacturers of America and the Biotechnology Innovation Organization. The brief filed by these two interest groups argues that Sandoz’s antitrust claims are compulsory counterclaims that should have been raised in its earlier attack on the Embrel patent. The brief also argued that the U.S. Supreme Court’s ruling in Mercoid Corp. v. MidContinent Inv. Co., which would have allowed a different result, is widely criticized and narrowly interpreted and limited to unusual facts.

Washington Legal Foundation. This brief notes that Federal Rule 13(a) requires a defendant to assert any counterclaims arising from the same “transaction or occurrence” as the plaintiff’s claim. A defendant that fails to do so is barred from raising the counterclaim in a later action.

Brief of former Federal Circuit Court Judge Paul R. Michel. This brief states that patent and antitrust laws promote innovation, competition, and the public interest. These interests are best served when related patient and antitrust disputes are litigated together. The compulsory counterclaim requirement of Federal Rule 13(a) furthers the important interests of finality, judicial economy and certainty in patent rights by preventing parties from withholding logically and largely related claims, only to litigate those related claims years later.

The Case is No. 26-1309.

Attorneys: Karla Michelle Doe (Alston & Bird, LLP) for Sandoz Inc. Elaine Janet Goldenberg (Munger, Tolles & Olson LLP) for Amgen Inc.

Companies: Sandoz Inc.; Amgen Inc.

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