WLF Urges Fourth Circuit to Reject Antitrust End-Run Around Prior Patent Judgment

“Antitrust law does not allow one district court to sit in review of another, nor does it permit parties to relitigate old theories under new labels.”
—Jay DeSanto, WLF Senior Litigation Counsel

Click HERE to read amicus brief.

Washington, DC—Washington Legal Foundation (WLF) today urged the U.S. Court of Appeals for the Fourth Circuit to affirm the dismissal of antitrust claims against pharmaceutical company Amgen over patents for “etanercept,” a molecule used to treat arthritis. In an amicus brief supporting Amgen, WLF contends that the lower court correctly rejected Sandoz’s attempt to relitigate issues already resolved in prior litigation over those patents.

The case concerns a long-running dispute over patents covering etanercept, the active ingredient in the arthritis drug Enbrel. In prior litigation, Sandoz challenged the validity of Amgen’s etanercept patents, but those challenges were rejected, and the patents were upheld through final judgment and appeal. In this action, Sandoz brings a Sherman Act Section 2 claim alleging that Amgen’s acquisition and enforcement of those same patents unlawfully extended its exclusivity over the etanercept molecule.

WLF’s brief contends that Sandoz’s claims are barred by claim-preclusion principles. It explains that Rule 13(a) and res judicata prohibit parties from repackaging previously litigated patent-validity theories in follow-on suits, and that antitrust claims are not exempt from those rules. WLF warns that accepting Sandoz’s theory would invite collateral attacks on final judgments, encourage duplicative litigation, and undermine the certainty essential to the patent system.