Donidalorsen has received European Union marketing authorisation for the routine prevention of hereditary angioedema attacks in adults and adolescents aged 12 years and older.

The approval applies across all 27 EU member states, as well as Iceland, Liechtenstein and Norway, following a positive opinion from the Committee for Medicinal Products for Human Use in November 2025. The drug will be marketed in Europe by Otsuka Pharmaceutical Europe Ltd under the brand name Dawnzera.

Hereditary angioedema is a rare, potentially life-threatening genetic disorder characterised by recurrent episodes of swelling affecting the extremities, face, abdomen, genitals and airway. The condition affects around 15,000 people in Europe and is most commonly caused by deficiency or dysfunction of C1 esterase inhibitor, leading to excessive bradykinin production.

Donidalorsen is an antisense oligonucleotide therapy designed to reduce prekallikrein production in the liver, interrupting the pathway that leads to angioedema attacks. It is administered subcutaneously as a prophylactic treatment.

In the pivotal Phase 3 OASIS-HAE study, donidalorsen 80 mg every four weeks led to an 81% reduction in attack rate compared with placebo over 24 weeks. Dosing every eight weeks resulted in a 55% reduction in attacks. At week 24, 91% of patients receiving four-weekly dosing had well-controlled disease compared with 41% in the placebo group, measured using the Angioedema Control Test.

No major safety concerns were identified in the trial, with similar adverse event profiles across dosing schedules. The most common adverse events included injection site reactions, increased hepatic enzymes and hypersensitivity, including anaphylaxis.

Henrik Balle Boysen, president of HAE International, said: “As the first European-approved RNA-targeted therapy for HAE, donidalorsen represents a welcome development in therapeutic options for preventing attacks. Today’s approval gives people living with HAE and their physicians another choice for aligning treatment with individual needs.”

Danny Cohn, internist at Amsterdam University Medical Center, said: “The European Commission’s authorisation of donidalorsen is a welcome decision for the HAE clinical community. With encouraging trial results, donidalorsen has demonstrated clinical efficacy and offers a beneficial addition to our current treatment options.”

Ionis Pharmaceuticals and Otsuka entered a licensing agreement in 2023 covering commercialisation in Europe, with the collaboration later extended to Asia Pacific. Ionis continues to lead clinical development and is responsible for launch activities in the United States, while Otsuka is preparing for launches in other regions.

Andy Hodge, president and ceo of Otsuka Pharmaceutical Europe Ltd, said: “We are proud of the decision from the European Commission to authorise the use of donidalorsen in HAE. This represents another key milestone in the collaboration between Otsuka and Ionis which aims to address unmet need in a challenging rare disease.”

Donidalorsen was approved in the United States in August 2025 for prophylaxis of hereditary angioedema attacks in adults and children aged 12 years and older. The EU authorisation represents a regulatory milestone for RNA-targeted therapies in rare immunological diseases, although long-term real-world safety and effectiveness data will be required to define its clinical positioning.