The Medicines and Healthcare products Regulatory Agency (MHRA) has today, 7 May 2026, approved donidalorsen (Dawnzera) for use in patients 12 years and older with hereditary angioedema (HAE) to prevent angioedema attacks. 

Hereditary angioedema (HAE) is an inherited condition characterised by a deficiency or dysfunction of the C1 inhibitor protein. This can lead to swelling around the body and stomach pains. These attacks can be life-threatening when swelling around the throat presses against the airway. 

Donidalorsen works by inhibiting the production of plasma kallikrein, thereby reducing bradykinin levels in the bloodstream. This helps to prevent the symptoms associated with hereditary angioedema (HAE). 

Donidalorsen is administered as an injection from a pre-filled pen under the skin. 

In a main study, donidalorsen significantly reduced the number of attacks in people with hereditary angioedema compared with placebo. 

The main study involved 91 patients from 12 years of age with hereditary angioedema. The patients received donidalorsen either every 4 weeks or every 8 weeks, or placebo.  

After 24 weeks, the average number of attacks per month was around 0.4 in patients given donidalorsen every 4 weeks and around 1 attack for those given Dawnzera every 8 weeks. This was lower compared with around 2.3 for those given placebo.  

Donidalorsen was also shown to improve patients’ quality of life, based on a validated questionnaire assessing how symptoms affect daily life. 

Julian Beach, MHRA Executive Director of Healthcare Quality and Access, said: 

“This approval provides a new treatment option for patients aged 12 years and older living with hereditary angioedema, an inherited condition that can cause recurrent swelling attacks and significant impact on daily life.  

“As with all medicines, we will continue to closely monitor the safety and effectiveness of donidalorsen as it is used more widely.” 

The most common side effects with Dawnzera (which may affect more than 1 in 10 people) are: 

  • Reactions where the injection is given. Symptoms may include redness, change in skin colour, pain, itching, hardening, haematoma (bleeding under the skin at the site of the injection), bruising, scaling of the skin, allergic reaction or swelling. 

  • Blood tests showing liver changes. 

For the full list of all side effects reported with this medicine, see Section 4 of the PIL or the SmPC available on the MHRA website. 

Notes to editors    

  • The approval was granted on 07//2026 to Otsuka Pharmaceutical Netherlands B.V. 

  • This product was submitted and approved via International Recognition Procedure (IRP). 

  • More information can be found in the Summary of Product Characteristics and Patient Information Leaflets which will be published on the MHRA Products website within 7 days of approval.   

  • The Medicines and Healthcare products Regulatory Agency (MHRA) is responsible for regulating all medicines and medical devices in the UK by ensuring they work and are acceptably safe. All our work is underpinned by robust and fact-based judgements to ensure that the benefits justify any risks.   

  • The MHRA is an executive agency of the Department of Health and Social Care.   

  • For media enquiries, please contact newscentre@mhra.gov.uk or call 020 3080 7651.