European Commission Approves Ionis and Otsuka’s Dawnzera for Hereditary Angioedema Prevention

Ionis Pharmaceuticals and Otsuka Pharmaceutical have received European Commission approval for Dawnzera (donidalorsen) for the routine prevention of recurrent attacks of hereditary angioedema (HAE).

The therapy is approved across the European Union for:

• Adults and adolescents 12 years and older
• Prophylactic (preventive) treatment of recurrent HAE attacks

The decision follows a positive opinion from the Committee for Medicinal Products for Human Use (CHMP).

Phase 3 studies show strong and durable attack reduction

Approval is supported by results from the phase 3 OASIS-HAE and OASISplus clinical studies.

Key outcomes include:

• Significant and sustained reduction in mean monthly HAE attack rate
• 94% overall mean monthly attack rate reduction at one year in the OASISplus open-label extension study
• Consistent benefit across multiple disease activity measures

Dawnzera is self-administered via subcutaneous autoinjector every four or eight weeks.

First RNA-targeted prophylactic therapy for HAE

“As the first and only RNA-targeted therapy for hereditary angioedema, we believe Dawnzera has the potential to become the prophylactic therapy of choice,” said Brett P. Monia, CEO of Ionis.

Otsuka Europe CEO Andy Hodge added that the approval represents a key milestone in the long-standing Ionis–Otsuka collaboration focused on addressing unmet need in rare diseases.

About hereditary angioedema

Hereditary angioedema is a rare, potentially life-threatening genetic disorder characterized by recurrent swelling episodes affecting:

• Hands and feet
• Face and genitals
• Gastrointestinal tract
• Airway and throat

The condition is estimated to affect 1 in 50,000 people worldwide.

Regulatory status and commercial terms

• Approved in the United States in August 2025
• Approved in the European Union for patients aged ≥12 years
• Otsuka holds exclusive commercialization rights in Europe and Asia Pacific
• Ionis is eligible for a $15 million milestone payment and tiered royalties up to 30%

How Dawnzera works?

Dawnzera is an RNA-targeted medicine designed to inhibit plasma prekallikrein (PKK), a key driver of inflammatory mediator activation associated with HAE attacks.

Safety overview

• Contraindicated in patients with prior serious hypersensitivity to donidalorsen
• Hypersensitivity reactions, including anaphylaxis, have been reported
• Most common adverse reactions (≥5%):
  - Injection site reactions
  - Upper respiratory tract infection
  - Urinary tract infection
  - Abdominal discomfort

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