MHRA licenses Arrowhead's quarterly plozasiran for familial chylomicronaemia syndrome

The Medicines and Healthcare products Regulatory Agency (MHRA) granted a UK marketing authorisation on 19 October 2026 for Arrowhead's plozasiran, sold as Redemplo, to lower triglycerides in adults with familial chylomicronaemia syndrome (FCS) when used with a low-fat diet¹. The licence holder is Arrowhead Pharmaceuticals Ireland Limited¹.

FCS is a rare disorder in which triglyceride levels in the blood run abnormally high, and patients are at risk of pancreatitis with severe abdominal pain¹. Plozasiran works by cutting the liver's output of apolipoprotein C3, a protein that slows the clearance of fats, so that triglycerides fall¹.

What the trial found

The MHRA based its decision mainly on one study of 75 adults with FCS, all of whom were kept on a controlled diet¹. Of these, 50 received plozasiran and 25 received placebo¹. At 10 months, the median fall in triglycerides was around 80% on plozasiran against 17% on placebo, and the plozasiran group had fewer episodes of acute pancreatitis¹.

The most frequent side effect was hyperglycaemia, which may affect more than one in 10 people¹. Headache, nausea and injection site reactions were listed as common, affecting up to one in 10¹.

Dosing is a 25 mg subcutaneous injection every three months, and patients or carers can give it themselves once trained¹. Julian Beach, the MHRA's Executive Director of Operations, said the authorisation "provides an additional treatment option for adults with familial chylomicronaemia syndrome" and that the agency would "continue to monitor the safety of plozasiran closely"¹.

What it means for the market

The route matters as much as the medicine. The MHRA approved plozasiran through Route B of its International Recognition Procedure, with the European Medicines Agency as the reference regulator¹. That procedure lets the UK agency lean on another regulator's assessment rather than run a full review of its own, and this decision is a further example of a rare disease product reaching the UK by that path¹.

For Arrowhead, the licence adds the UK to the markets where a quarterly RNA interference therapy for FCS can be sold¹. For NHS commissioners and specialist lipid services, it creates a licensed option in a condition where diet is the backbone of care¹. The MHRA release does not cover price, NICE appraisal or how the NHS will commission the drug, so access for patients in England is still to be settled¹.

Clinicians and pharmacists will also have to weigh the raised blood sugar signal, given that hyperglycaemia is the most common adverse effect reported¹.

Caveats

The evidence rests largely on a single study of 75 people, reflecting the rarity of FCS¹. The triglyceride result is given as a median of around 80%, and the release gives no figure for the reduction in pancreatitis episodes¹. The Summary of Product Characteristics and Patient Information Leaflet have not yet been published; the MHRA says they will appear on its Products website in due course¹.