Arrowhead Pharmaceuticals Inc. won U.S. FDA approval of plozasiran in familial chylomicronemia syndrome (FCS), the second drug to gain clearance for use in the rare genetic disease following the late 2024 nod for Ionis Pharmaceuticals Inc.’s Tryngolza (olezarsen), setting up a battle in the marketplace even as the firms wage a patent dispute regarding the two RNA-based therapies.