In an announcement published on GOV.UK, the Medicines and Healthcare products Regulatory Agency said it approved donidalorsen, marketed as Dawnzera, on 7 May 2026 for patients aged 12 years and over with hereditary angioedema. The licence covers prevention of angioedema attacks, adding a new option for a rare inherited condition that can be severe and, when swelling affects the throat, potentially life-threatening. The approval was granted to Otsuka Pharmaceutical Netherlands B.V. The MHRA presented the decision as a UK regulatory authorisation based on its assessment that the medicine’s benefits outweigh its risks in the approved patient group.
Hereditary angioedema, often shortened to HAE, is linked to deficiency or dysfunction of the C1 inhibitor protein. According to the MHRA, that defect can lead to recurrent swelling episodes in different parts of the body and can also cause significant abdominal pain. For some patients, the main policy issue is not only rarity but unpredictability: attacks can disrupt education, work and routine care, and urgent treatment may be needed if the airway is affected. Donidalorsen is designed as a preventive treatment rather than a medicine used only after an attack has started. The MHRA said it works by inhibiting production of plasma kallikrein, which in turn lowers bradykinin levels in the bloodstream and helps prevent the swelling symptoms associated with HAE.
The evidence highlighted by the MHRA came from a main study involving 91 patients aged 12 years and older with hereditary angioedema. Participants received donidalorsen every four weeks, donidalorsen every eight weeks, or placebo over a 24-week period. By the end of that study window, the average number of attacks per month was about 0.4 in the group treated every four weeks and about 1.0 in the group treated every eight weeks, compared with about 2.3 in the placebo group. The agency also said the medicine improved quality of life scores on a validated questionnaire measuring how symptoms affect daily life.
For readers following medicines regulation, the route matters as much as the result. The application was submitted and approved through the International Recognition Procedure, or IRP. In plain terms, that is an MHRA route that allows the UK regulator to consider prior work from an accepted overseas reference regulator as part of its own decision-making, while still issuing a distinct UK approval. For patients and clinicians, that does not remove MHRA oversight. The practical point is that the procedure can reduce duplicated regulatory work where a medicine has already been examined elsewhere, but the UK regulator remains responsible for deciding whether the product should be authorised for the UK market and under what terms.
The MHRA’s public statement also set out how the medicine is given and what safety issues clinicians and patients should expect to monitor. Dawnzera is administered under the skin using a pre-filled pen, which places it in a treatment format already familiar to many patients using long-term specialist medicines. The most commonly reported adverse effects, affecting more than one in 10 people, were reactions at the injection site and blood test findings showing liver changes. The agency listed possible injection-site symptoms including redness, skin colour change, pain, itching, hardening, bruising, swelling, haematoma and allergic reaction. The full side-effect profile will appear in the Patient Information Leaflet and the Summary of Product Characteristics published on the MHRA products site.
Julian Beach, the MHRA’s Executive Director of Healthcare Quality and Access, said the approval gives patients aged 12 and over another treatment option for a condition that can cause repeated swelling attacks and major disruption to daily life. He also said the agency would continue to monitor the safety and effectiveness of donidalorsen as use becomes more widespread. That post-authorisation follow-up is a standard part of medicines regulation, but it carries particular weight in rare disease treatment where patient numbers are smaller at launch than they are for common conditions. In practical terms, the decision means specialists now have a newly licensed preventive medicine to consider for eligible HAE patients, while product information and routine safety monitoring will shape how the treatment is used in day-to-day care.