Plozasiran CHMP Nod Opens siRNA Pathway for FCS Without Genetic Testing

Arrowhead Pharmaceuticals Ireland Limited has secured a positive CHMP opinion for Redemplo (plozasiran), positioning the first-in-class siRNA therapy as a viable treatment option for adults with familial chylomicronaemia syndrome (FCS) who lack genetic confirmation of their diagnosis. That eligibility distinction is operationally significant: existing authorised therapies for FCS require genetic testing, meaning a subset of clinically diagnosed patients has remained without a licensed treatment option. Redemplo's label removes that barrier, directly expanding the addressable patient population under EU marketing authorisation.

FCS is a rare inherited disorder characterised by severely elevated triglyceride levels, carrying risk of acute pancreatitis, hepatosplenomegaly, diabetes, and xanthomas. Dietary fat restriction is the primary management strategy, but it is not consistently feasible or sufficient to prevent pancreatitis episodes. Traditional lipid-lowering agents have demonstrated minimal efficacy in this population. Plozasiran works by blocking production of APOC3, a protein that inhibits fat breakdown, thereby reducing circulating triglyceride levels and expected pancreatitis risk. The therapy is administered subcutaneously every three months.

The CHMP recommendation rests on a single pivotal study of 75 adults with FCS, all maintained on a controlled diet throughout. At 10 months, patients receiving Redemplo achieved an average 80% reduction in triglyceride levels versus 17% in the placebo arm. The effect was observed in both genetically confirmed and clinically diagnosed FCS patients, was sustained across the one-year study duration, and persisted for at least 18 months. The study also recorded significantly fewer acute pancreatitis cases in the Redemplo group compared with placebo. Reported adverse effects included hyperglycaemia, headache, nausea, and injection-site reactions.

For regulatory affairs and pharmacovigilance teams, the orphan medicinal product designation -- granted on 19 July 2021 -- adds a procedural layer: following the CHMP opinion, the Committee for Orphan Medicinal Products (COMP) will assess whether that designation should be maintained. The CHMP opinion now moves to the European Commission for a formal EU-wide marketing authorisation decision. Pricing and reimbursement determinations will subsequently occur at the Member State level, introducing the country-by-country access variability that rare disease manufacturers routinely navigate in post-authorisation commercialisation planning.