Ionis sues Arrowhead for patent infringement over plozasiran, threatening FCS launch

ARROWHEAD PHARMACEUTICALS, INC.

Ionis filed complaint in Central District of California alleging Arrowhead's plozasiran infringes U.S. Patent No. 9,593,333.
Arrowhead had preemptively sought declaratory judgment in Delaware to invalidate the same patent on Sept. 10, 2025.
Arrowhead expects FDA decision on plozasiran NDA by Nov. 18, 2025 (PDUFA) and plans Q4 2025 launch.
The '333 patent covers method of reducing triglycerides in adults with familial chylomicronemia syndrome (FCS).
Ionis says it sent a pre-suit notice on Sept. 3, 2025; Arrowhead did not engage before filing DJ action.

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