MHRA approves plozasiran for adults with rare FCS
On 19 October 2026, the Medicines and Healthcare products Regulatory Agency authorised plozasiran, sold as Redemplo, for adults with familial chylomicronaemia syndrome, or FCS. The medicine is designed to reduce triglyceride levels and is meant to be used alongside a low-fat diet. **Why this matters:** this is not a medicine aimed at the general public. It is for a very small group of patients living with a rare condition that can bring serious and painful complications.
If you have never heard of FCS, that is understandable. MHRA describes it as a rare condition in which triglycerides, a type of fat in the blood, rise to abnormally high levels. When those levels stay very high, the pancreas can become inflamed. That is called pancreatitis, and it can cause severe abdominal pain. **In plain English:** FCS is one of those illnesses where a blood test result is not just a number on a page. Very high triglyceride levels can be tied to sudden, severe symptoms that affect daily life.
Plozasiran works by blocking the production of apolipoprotein C3, a protein made in the liver that slows the breakdown of fats. If less of that protein is produced, triglyceride levels can fall. The treatment is given as a 25 mg injection under the skin once every three months. Patients can give it themselves, or a carer can do it, after training. **What this means:** it is not a daily medicine, but it still needs support from a clinical team and it does not replace the low-fat diet.
The main evidence behind the decision came from a study of 75 adults with FCS. Everyone in the study followed a controlled diet. Of those patients, 50 received plozasiran and 25 received a placebo. After 10 months, the median reduction in triglyceride levels was around 80% in the plozasiran group, compared with 17% in the placebo group. The study also recorded fewer episodes of acute pancreatitis among people receiving plozasiran. For patients and families, that is likely to be the most important part of the result, because lower blood-fat levels matter most when they reduce real harm.
Approval, though, is not the same as saying a medicine is right for every patient or that all questions have been settled. What MHRA authorisation means is that the UK regulator judged the benefits and risks on the evidence available and decided the medicine could be used for this group of adults. The authorisation was granted to Arrowhead Pharmaceuticals Ireland Limited. MHRA says the medicine was approved through the International Recognition Procedure, Route B, with the European Medicines Agency acting as the reference regulator. **What that means for you:** the treatment has been through a formal regulatory process before reaching patients in the UK.
The most commonly reported side effect was hyperglycaemia, or raised blood sugar, which may affect more than one in 10 people. Other common side effects, which may affect up to one in 10 people, include headache, nausea and reactions at the injection site. MHRA also said it will continue to monitor plozasiran closely, as it does with all medicines. That is worth paying attention to, because approval is not the end of the safety story. Regulators keep watching once a medicine moves beyond a trial and into wider use.
If someone thinks they are having a side effect, the advice in the MHRA notice is straightforward: speak to a doctor, pharmacist or nurse and report it through the Yellow Card scheme or the MHRA Yellow Card app. For readers who want the official paperwork, the Summary of Product Characteristics and the Patient Information Leaflet are due to be published on the MHRA Products website. The bigger picture is simple. For most people, this announcement will pass quietly. For adults living with FCS, it could mean a new option that brings triglyceride levels down sharply and may help cut the risk of pancreatitis. That is why a technical medicines notice is also a very human story.