Argo Biopharma Presents Promising Phase 2 Data for Hereditary Angioedema Treatment

SHANGHAI and BOSTON – February 26, 2026 – Argo Biopharmaceutical Co., Ltd. Announced today that interim data from its Phase 2 study of BW-20805, an investigational small interfering RNA (siRNA) therapy for hereditary angioedema (HAE), have been selected as a late-breaking abstract for presentation at the American Academy of Allergy, Asthma & Immunology (AAAAI) 2026 Annual Meeting, February 27-March 2, 2026.¹

Understanding Hereditary Angioedema

Hereditary angioedema (HAE) is a rare, genetic condition characterized by unpredictable swelling in various body parts. Severe cases involving the throat can be life-threatening.² Approximately 1.5 people per 100,000 worldwide are affected by HAE.² Current treatments often require frequent administration, creating a need for long-acting preventative therapies.

BW-20805: A Novel Approach to HAE Prevention

BW-20805 is designed to target and inhibit prekallikrein (PKK), a validated therapeutic target for HAE. By reducing PKK levels, the therapy aims to prevent HAE attacks with a potentially long-lasting effect.¹

Phase 2 Interim Results: Significant Attack Reduction

The open-label Phase 2 study demonstrates significant reductions in HAE attack rates and substantial decreases in plasma PKK levels with BW-20805. Key findings include:

• HAE Attack Rate Reduction: A 100% reduction in time-normalized HAE attack rates was observed in the 600 mg Q24W (every 24 weeks) group. Reductions of 89% and 87% were seen in the 300 mg Q24W and 300 mg Q12W (every 12 weeks) groups, respectively.¹
• Patient Response: 80% (8 out of 10) of patients treated with BW-20805 remained attack-free.¹
• PKK Level Reduction: Rapid and profound reductions in plasma PKK levels were achieved. Mean reductions exceeded 92% in the pooled 300 mg groups and approximately 97% in the 600 mg Q24W group on Day 85.¹
• Sustained Suppression: PKK suppression was sustained at 98% in the 300 mg Q12W group and 97% in the 600 mg Q24W group on Day 169.¹
• Safety and Tolerability: BW-20805 was generally well-tolerated, with mostly mild and transient injection-site reactions. No serious adverse events were reported.¹

About Argo Biopharma

Argo Biopharma is a clinical-stage biotechnology company focused on developing RNAi therapeutics. The company has a pipeline of seven RNAi candidates in clinical development, targeting conditions including cardiovascular diseases, viral infections, metabolic conditions, and rare diseases.¹

Looking Ahead

These Phase 2 interim results support further evaluation of BW-20805 as a potential best-in-class prophylactic therapy for HAE. The favorable safety profile and sustained efficacy suggest a promising future for this innovative treatment approach.

References:

1. Argo Biopharma to Present Positive Phase II Interim Results of siRNA Therapeutic BW-20805 for HAE at the 2026 AAAAI Annual Meeting. PR Newswire. February 25, 2026.
2. Giavina-Bianchi P, et al. (2011). CLINICS 66(9): 1627–1636.
3. Aygören-Pürsün, E, et al. (2018). Orphanet J Rare Dis 13(1): 73.