MHRA approves resmetirom for UK adults with MASH

On 3 June 2026, the Medicines and Healthcare products Regulatory Agency, or MHRA, authorised resmetirom, sold as Rezdiffra, for adults with metabolic dysfunction-associated steatohepatitis, known as MASH. The regulator says it is the first medicine approved for patients with MASH and moderate to advanced liver fibrosis, and it is aimed at adults with stage 2 or stage 3 fibrosis. (gov.uk) If you are hearing several new terms at once, that matters. This is not a general approval for every kind of fatty liver disease. It is a treatment decision for adults whose illness has already moved into inflammation, cell damage and scarring. (gov.uk)

MASH can sound technical, but the basic picture is easier to follow than the name suggests. The MHRA says fat builds up in the liver, which can then lead to inflammation and damage to liver cells; over time, that process can cause scarring and affect how the liver works. (gov.uk) Cambridge University Hospitals explains that fatty liver does not always lead to severe damage, but in some people it progresses to MASH, where inflammation and scarring become part of the story. The same NHS trust says fatty liver disease is now the most common cause of liver disease and estimates that about one in five people in the UK have it, which helps explain why a new treatment has drawn so much attention. (cuh.nhs.uk)

Resmetirom is being used for a very specific job. According to the MHRA, in people with MASH a protein called thyroid hormone receptor beta, or THR-β, is less active in liver cells called hepatocytes. Resmetirom binds to that receptor and activates it, which increases fat breakdown in the liver. (gov.uk) **What this means:** the medicine is designed to help the liver handle fat better rather than simply papering over symptoms. The MHRA says that by reducing the fat stored in the liver, resmetirom can help reduce inflammation and fibrosis and improve liver function, and it is taken by mouth as a tablet. (gov.uk)

The approval rests on evidence from a main study of 917 adults with MASH and moderate or advanced liver fibrosis who took either resmetirom or a placebo for 12 months. The MHRA reports that, depending on dose, about 26 to 30 per cent of patients on resmetirom achieved MASH resolution with no worsening of fibrosis, compared with 10 per cent on placebo. (gov.uk) The same study found that 27 to 29 per cent of people taking resmetirom had an improvement in liver fibrosis with no worsening of MASH, compared with 17 per cent of those on placebo. Put plainly, the medicine helped more people reach those liver goals than placebo did, but it was not a guaranteed response for everyone. (gov.uk)

The authorisation covers 60 mg, 80 mg and 100 mg film-coated tablets, and the MHRA says it was granted through the International Recognition Procedure, or IRP. GOV.UK guidance says this route, which has been in place since 1 January 2024, allows the MHRA to use prior approvals from a set of trusted regulators while still making its own licensing decision for the UK. (gov.uk) **What approval means in practice:** a medicine being authorised is a big regulatory step, but it is not always the final access step. Separate GOV.UK guidance on the NHS medicines pathway says that after marketing authorisation, medicines can still need health technology evaluation, pricing and funding decisions before routine NHS availability is settled. (gov.uk)

For patients, the next questions are usually about safety and day-to-day use. The MHRA says resmetirom is taken orally, and that the most common side effects, affecting more than 1 in 10 people, are diarrhoea and nausea. Anyone who thinks they may be having a side effect is being advised to speak to a doctor, pharmacist or nurse and to report it through the Yellow Card scheme. (gov.uk) There is a genuine shift here: until this decision, the MHRA had not approved a medicine in the UK for patients with MASH and moderate to advanced liver fibrosis. The authorisation was granted on 3 June 2026 to Madrigal Pharmaceuticals EU Limited, and the MHRA says fuller product information and patient leaflets will be published on its products website within seven days of approval. (gov.uk)