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

Otsuka Pharmaceuticals UK announces MHRA authorisation of new treatment option for the routine prevention of recurrent attacks of hereditary angioedema in adults and adolescents aged 12 years and older

May 21, 2026 – Biotechnology, Clinical Trials, Drug Discovery, Other, Pharmaceutical – MHRA, Otsuka Pharmaceuticals UK, approvals, clinical trials, hereditary angioedema

The first ribonucleic acid (RNA)-targeted prophylactic therapy for patients with hereditary angioedema (HAE) to be authorised by the MHRA
HAE is a rare and potentially life-threatening genetic condition affecting approximately 1 in 59,000 people in the UK
The treatment was shown to reduce HAE attack rates compared with placebo in the Phase 3 OASIS-HAE study.

21 May 2026 — Windsor, UK — Otsuka Pharmaceuticals UK Ltd (Otsuka UK) today announced that the UK Medicines and Healthcare products Regulatory Agency (MHRA) has authorised Dawnzera (donidalorsen) for the routine prevention of recurrent attacks of hereditary angioedema (HAE) in adults and adolescents aged 12 years and older.

HAE is a rare, genetic condition characterised by unpredictable swelling episodes that can affect the extremities, face, abdomen, genitals and the larynx. In the UK, it is estimated to affect around 1 in 59,000 people. Attacks can be unpredictable and, when they involve the throat, may become life-threatening without prompt treatment. Although effective therapies are available to prevent and manage attacks, HAE still remains under-recognised and diagnosis is often delayed by several years.

Approximately 50% of people with HAE experience their first symptoms by the age of 10 with the majority experiencing symptoms or their first attack by 18 years of age. The unpredictable nature, frequency and potential severity of swelling episodes can have a significant psychological impact, and anxiety and depression are commonly reported in patients living with HAE. “For people living with HAE, the unpredictability of attacks can take a profound toll on both their physical health and emotional wellbeing,” said Angela Metcalfe, CEO, HAE UK. “Living with the constant uncertainty of when the next attack may occur can affect work, family life and overall wellbeing.”

The MHRA’s decision was based on results from the pivotal, double-blind, randomised, placebo-controlled, Phase 3 OASIS-HAE clinical trial, which evaluated the safety and efficacy of the treatment in patients with HAE (n=90). The primary endpoint was the time-normalised number of investigator-confirmed HAE attacks per 4 weeks (attack rate) from baseline to week 24. In the study, 80 mg of this medicine every four weeks (Q4W, n=45) led to an 81% reduction (95% Confidence interval [CI]: -89, -65; P<0.001) in 4-weekly HAE attack rate compared to placebo (n=22) (least-squares mean attack rates 0.44 [95% CI:0.27, 0.73] vs. 2.26 [95% CI: 1.66, 3.09] respectively) over 24 weeks. A 55% reduction (95% CI: -74, -22; P = 0.004) compared to placebo was observed with dosing every eight weeks (Q8W, n=23; least-squares mean attack rate 1.02 [95% CI: 0.65, 1.59]). Therefore, the study met its primary endpoint.

At week 24, 91% (41/45) of Q4W and 74% (17/23) of Q8W had well-controlled disease compared to 41% (9/22) of patients in the placebo group, as measured by the Angioedema Control Test (a score of ≥10).

The most common adverse events include injection site reactions, increased hepatic enzymes (both very common) and hypersensitivity, including anaphylaxis (common).

“Managing HAE is a long-term challenge for patients,” said Professor Sinisa Savic, Professor of Clinical Immunology at The University of Leeds. “As UK clinicians we see first-hand the physical, emotional and practical toll this condition can take on individuals and their families. Despite advances in care, unmet needs persist in everyday disease management.”

Ionis Pharmaceuticals, Inc. and Otsuka Pharmaceutical Co., Ltd entered the initial license agreement for the commercialisation of the treatment in Europe in 2023, with the agreement later broadening to Asia Pacific. Ionis has maintained responsibility for the clinical development of the medicine as well as the responsibility for its launch in the United States with Otsuka utilising its expertise in rare disease and commercial infrastructure to prepare for future market launches.

“In the UK, access criteria for HAE prophylactic treatments have historically been inflexible and have not always reflected the individual impact of the disease,” said Ryan Gynne, Managing Director at Otsuka Pharmaceuticals UK, Ireland and CEE. “We are proud of the MHRA’s authorisation of this medicine and the opportunity it presents to offer eligible patients an additional preventative treatment option, supporting more personalised decision-making based on individual needs. We are committed to working with NICE and the NHS to help ensure appropriate access to this treatment.”

About Otsuka
Otsuka Pharmaceutical Co., Ltd. is a total healthcare company that focuses on each individual’s potential to enhance their well-being. Our medical-related business provides treatments and diagnostics for both physical and mental health. Our nutraceutical business supports daily health maintenance and improvement. Otsuka’s products and services are based on scientific evidence, under the guidance of our corporate philosophy: Otsuka-people creating new products for better health worldwide. Otsuka Europe employs around 500 people and focuses on psychiatric and neurologic disorders, nephrology andimmunology, haemato-oncology, and digital therapeutics.
Otsuka Pharmaceutical Europe Ltd. is a part of Otsuka Pharmaceutical Company, Ltd., a subsidiary of Otsuka Holdings Co., Ltd. headquartered in Tokyo, Japan. For further information on Otsuka, please visit www.otsuka-europe.com.