Our Patent Case Summaries provide a weekly summary of the precedential patent-related opinions issued by the Court of Appeals for the Federal Circuit and the opinions designated precedential or informative by the Patent Trial and Appeal Board.
Ascendis Pharma A/S, et al. v. BioMarin Pharmaceutical Inc.
No. 2026-1026 (Fed. Cir. (N.D. Cal.) Mar. 26, 2026). Opinion by Stoll, joined by Lourie and Chen.
Ascendis and BioMarin are both drug manufacturers developing treatments for children with achondroplasia. BioMarin launched an FDA-approved drug for treating that condition, and it owns a patent covering the drug. Once Ascendis filed a New Drug Application with the FDA seeking approval of its own drug, BioMarin filed an infringement complaint with the ITC.
Soon after being named a respondent in the ITC, Ascendis filed a declaratory-judgment complaint in district court. More than 30 days later, Ascendis filed a notice of voluntary dismissal without prejudice for purposes of refiling its action in order to seek a mandatory stay under 28 U.S.C. § 1659(a)(2), which must be requested within 30 days after being named a respondent in an ITC investigation.
After Ascendis re-filed the declaratory-judgment complaint, it moved for a mandatory stay under § 1659(a)(2). BioMarin opposed the motion, asserting that the request was untimely, and moved for a discretionary stay. The district court granted BioMarin’s motion for a discretionary stay and denied Ascendis’s motion for a mandatory stay as moot. Ascendis appealed.
The Federal Circuit affirmed. First, the court considered whether Ascendis had Article III standing to appeal. Ascendis asserted standing based on BioMarin’s repeated statements that upon FDA approval of Ascendis’s drug, BioMarin could seek to lift the discretionary stay and pursue a preliminary injunction.
The Federal Circuit agreed with Ascendis. “The FDA decision remained imminent” (and in fact issued shortly after oral argument in the appeal). The Federal Circuit thus ruled that “under these circumstances, Ascendis has shown that there exists a controversy of sufficient immediacy and reality to warrant the requested judicial relief.”
The Federal Circuit next considered whether it had jurisdiction under the collateral order doctrine, since the court’s jurisdiction “is typically limited to an appeal from a final decision of a district court.” The court confirmed that Ascendis’s appeal met all the requirements: the district court’s order conclusively determined the disputed question, resolved “an important issue completely separate from the merits of the underlying action,” and “is effectively unreviewable on appeal from a final judgment because a mandatory stay under § 1659(a)(2) is designed to prevent litigation from occurring while an ITC case is pending.”
Turning to the merits, the Federal Circuit ruled that any error by the district court in denying Ascendis’s motion for a mandatory stay under § 1659(a)(2) was harmless. To begin, the Federal Circuit “d[id] not agree that a temporary stay necessarily renders a stay under § 1659(a)(2) moot.” “That the district court can lift a discretionary stay is a significant difference between the relief granted and the relief Ascendis sought.” Thus, Ascendis’s request was not moot.
Even so, the Federal Circuit determined that “the district court’s error in this regard was nonetheless harmless, however, because we hold that Ascendis was not entitled to a mandatory stay under § 1659(a)(2).” The court explained that the pertinent “district court action” for purposes of § 1659(a)(2) refers to “Ascendis’s original action, not its refiled action regardless of whether it voluntarily dismissed the original action without prejudice.” The Federal Circuit explained that its decision “fit[s] squarely within the common-law principle of prohibiting the use of voluntary dismissal to accomplish indirectly what cannot be accomplished directly.”
The Federal Circuit thus affirmed the district court’s decision denying Ascendis’s motion for a mandatory stay.