Arrowhead files declaratory judgment suit against Ionis over '333 patent for plozasiran

ARROWHEAD PHARMACEUTICALS, INC.

Arrowhead filed a declaratory judgment action in Delaware against Ionis claiming the '333 patent is invalid and not infringed by plozasiran.
Plozasiran is Arrowhead's RNAi therapy for familial chylomicronemia syndrome (FCS); Phase 3 PALISADE study showed up to 80% triglyceride reduction.
FDA PDUFA action date for plozasiran is November 18, 2025.
Ionis sent a September 3, 2025 letter alleging patent infringement and threatening suit; Arrowhead acted preemptively.
Arrowhead's complaint alleges the '333 patent claims are invalid for anticipation and lack of written description/enablement.

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