Significant Durable HAE Attack Reduction with BW-20805, Phase 2 Update

Argo Biopharmaceutical Co., Ltd. (Argo Biopharma), a clinical-stage small interfering RNA (siRNA) therapeutics company, will present updated Phase II results for its investigational siRNA therapeutic BW-20805 at the Bradykinin Symposium 2026. The oral presentation, titled "Significant Durable HAE Attack Reduction with BW-20805, Phase 2 Update," will take place on September 3-4, 2026, in Berlin, Germany.

BW-20805, an investigational siRNA therapeutic designed to silence plasma prekallikrein (PKK) messenger RNA, is being evaluated for its potential to provide durable prevention of hereditary angioedema (HAE) attacks with infrequent dosing. The updated data from the ongoing Phase II trial continue to support the drug's differentiated clinical profile, characterized by high potency and less frequent dosing.

Dr. Dongxu Shu, co-founder and Chief Executive Officer of Argo Biopharma, commented on the significance of the findings: "The updated Phase II results being presented at the Bradykinin Symposium 2026 provide continued clinical evidence for BW-20805's differentiated potential in HAE prophylaxis. The magnitude and durability of attack-rate reduction observed through Day 169, together with sustained PKK suppression and a well-tolerated safety profile, support continued advancement of this program."

The presentation will include data from an open-label, global, multicenter Phase II study evaluating three long-interval dosing regimens of BW-20805 in adults with HAE type 1 or 2. As of the June 2026 data cut-off, 25 participants were randomized and dosed across three treatment groups: BW-20805: 600 mg every 24 weeks (Q24W), 300 mg Q24W, and 300 mg every 12 weeks (Q12W).

Key data highlights from the study include: - Substantial reductions in monthly HAE attack rates across all treatment groups: - 600 mg Q24W group: 83% reduction - 300 mg Q24W group: 96% reduction - 300 mg Q12W group: 93% reduction - Attack-free rates over Day 29 to 169: - 600 mg Q24W group: 50% - 300 mg Q24W group: 75% - 300 mg Q12W group: 62.5% - Rapid and sustained pharmacodynamic activity, with mean plasma PKK reductions of 86%, 85%, and 94% in the respective treatment groups by Day 169. - Generally well-tolerated across all regimens, with no treatment-emergent adverse events leading to treatment discontinuation, withdrawal, or death. The most common adverse events were mild and transient injection-site reactions.

Hereditary angioedema (HAE) is a rare genetic condition affecting approximately 1.5 people per 100,000 worldwide, with a mortality rate of up to 40% in severe cases. Current treatments require frequent dosing, underscoring the need for long-acting, preventive therapies. BW-20805 targets human hepatic PKK mRNA to inhibit PKK gene expression, offering the potential for effective prevention of HAE attacks with a significant and longer-lasting therapeutic effect.

Argo Biopharma is committed to developing next-generation RNAi therapeutics to provide better treatment options for patients worldwide. The company has established a robust and diverse pipeline of RNAi molecule candidates targeting a wide range of indications, including cardiovascular diseases, viral infections, metabolic conditions, and specialty/rare diseases. Currently, Argo Biopharma has eight RNAi candidates in clinical development.