MHRA Authorises Redemplo for Rare Lipid Disorder

The UK's medicines regulator has authorised Arrowhead Pharmaceuticals' plozasiran, branded Redemplo, for adults with familial chylomicronaemia syndrome (FCS) — an ultra-rare disorder that leaves patients unable to clear triglycerides from their blood. The 19 October 2026 decision makes MHRA the third major regulator to clear the siRNA therapy, after FDA's approval in November 2025 and the European Commission's in June 2026.

A disease small enough that every approval is a milestone

Familial chylomicronaemia syndrome is a genetic disorder so rare that most RA/QA professionals outside lipid metabolism will not encounter it directly: patients cannot adequately clear triglyceride-rich lipoprotein particles called chylomicrons from the bloodstream, leaving them at risk of recurrent, severe acute pancreatitis even on an extremely restricted low-fat diet. Before Redemplo, treatment options for FCS were limited largely to diet and, in some cases, apheresis; there was no approved pharmacologic therapy that reliably lowered triglycerides in this population. That context is why each regulator's authorisation — US, EU, now UK — is treated as a discrete milestone rather than a routine label extension: for a disease this rare, regulatory access in any given country is often the deciding factor in whether a diagnosed patient has a treatment option at all.

What the authorisation covers

MHRA's authorisation covers adults with FCS, used alongside a low-fat diet, and is supported by a study of 75 adults — 50 receiving plozasiran and 25 receiving placebo, all following a controlled diet throughout. At 10 months, participants on plozasiran saw triglycerides fall by a median of approximately 80%, against 17% on placebo, and the study recorded fewer episodes of acute pancreatitis among those receiving the drug. The most common side effects MHRA identified are hyperglycaemia, headache, nausea and injection-site reactions. Dosing is a 25 mg subcutaneous injection every three months, and MHRA's authorisation specifically notes that patients or caregivers can administer the injection themselves once trained — a meaningful access consideration for a chronic condition requiring lifelong management, rather than one requiring a clinic visit every quarter.

How plozasiran works

Plozasiran is a small interfering RNA (siRNA) therapeutic: rather than blocking a protein's activity after it is made, as most small-molecule drugs do, it silences the liver's production of apolipoprotein C-III, a protein that normally slows the clearance of triglyceride-rich particles from the blood. With less apoC-III produced, triglycerides clear faster. The approach places Redemplo in the same therapeutic class as other RNA-interference drugs that have reached the market in recent years for various lipid and metabolic disorders, and its quarterly dosing schedule is characteristic of that drug class's typically long duration of effect compared with daily oral therapies.

The approval sequence: US, then EU, then UK

FDA approved Redemplo in the United States on 18 November 2025, describing it at the time as the first FDA-approved drug specifically for FCS. The European Commission followed with EU-wide marketing authorisation on 22 June 2026, after a positive CHMP opinion, with Arrowhead describing it as the first siRNA medicine the Commission has authorised for FCS and noting the EU label covers patients diagnosed either by clinical criteria or by genetic testing. MHRA's 19 October 2026 decision brings the UK into that same regulatory set roughly eleven months after the US and four months after the EU — a sequencing pattern regulatory teams tracking multi-jurisdiction rare-disease launches will recognise: US approval first, EU centralised authorisation months later, and MHRA's independent national assessment, operating outside the EU's procedure since Brexit, following on its own timeline rather than in lockstep with either.

Frequently asked questions

What did MHRA authorise, and when?

On 19 October 2026, MHRA authorised plozasiran (Redemplo, Arrowhead Pharmaceuticals) as an add-on to a low-fat diet to reduce triglycerides in adults with familial chylomicronaemia syndrome, an ultra-rare genetic disorder.

How is Redemplo administered?

As a 25 mg subcutaneous injection given once every three months, which patients or caregivers can administer themselves after training.

What evidence supported the authorisation?

A 75-adult study (50 plozasiran, 25 placebo) in which triglycerides fell a median of about 80% on plozasiran versus 17% on placebo at 10 months, with fewer acute pancreatitis episodes in the treated group.

Had Redemplo been approved anywhere else first?

Yes. FDA approved it in the US on 18 November 2025, and the European Commission granted EU-wide authorisation on 22 June 2026. The 19 October 2026 MHRA decision is its first authorisation in the UK.