On Nov. 18, 2025, Arrowhead Pharmaceuticals announced that the U.S. Food and Drug Administration (FDA) has approved REDEMPLO (plozasiran), a small interfering RNA (siRNA) medicine, as an adjunct to diet to reduce triglycerides in adults with familial chylomicronemia syndrome (FCS).

FCS is a severe, rare disease, with an estimated 6,500 people in the U.S. living with genetic or clinical FCS, characterized by triglyceride levels that can be 10 to 100 times higher than normal leading to a substantially higher risk of developing acute, recurrent, and potentially fatal pancreatitis.

FCS is a severe and rare disease leading to extremely high triglyceride (TG) levels, typically over 880 mg/dL. Such severe elevations can lead to various serious signs and symptoms including acute and potentially fatal pancreatitis, chronic abdominal pain, diabetes, hepatic steatosis, and cognitive issues. Currently, there are limited therapeutic options to adequately treat FCS.

REDEMPLO is the first and only FDA-approved siRNA medicine for people living with FCS and can be self-administered at home with a simple subcutaneous injection once every three months. REDEMPLO utilizes the proprietary and differentiated Targeted RNAi Molecule (TRiM™) platform and is Arrowhead’s first FDA-approved medicine, marking a major milestone for the company as it transitions into commercial-stage.

The FDA approval was supported by clinical data from the Phase 3 PALISADE study, a randomized, double-blind, placebo-controlled trial in adults with clinically diagnosed or genetically confirmed FCS.

The PALISADE study met its primary endpoint and all multiplicity-controlled key secondary endpoints, including demonstrating significant reductions in triglycerides and APOC3. In PALISADE, 25 mg REDEMPLO achieved deep and durable reductions in triglycerides, with a median change from baseline of -80% versus -17% in the pooled placebo group, and a lower numerical incidence of acute pancreatitis compared with placebo.

The most common adverse reactions in REDEMPLO treated patients (incidence ≥10% of patients treated with REDEMPLO and > 5% more frequently than with placebo) are hyperglycemia, headache, nausea, and injection site reaction. The US approved package insert contains no contraindications, warnings, or precautions associated with the use of REDEMPLO.