SHANGHAI, China & NEW YORK, USA – June 8, 2026
Argo Biopharma has announced positive updated Phase 2 results for BW-20805, its investigational small interfering RNA (siRNA) therapy for hereditary angioedema (HAE), ahead of a late-breaking presentation at the European Academy of Allergy and Clinical Immunology (EAACI) 2026 Congress in Istanbul, Türkiye. The updated analysis from the ongoing clinical study highlights remarkable and sustained reductions in HAE attack rates, durable suppression of plasma prekallikrein (PKK), and a favorable safety profile, reinforcing the therapy’s potential as a next-generation long-acting prophylactic treatment. Importantly, the results support further development of a once-every-six-month dosing regimen, which could represent a major advancement for patients living with this rare and potentially life-threatening genetic disorder. With current preventive therapies often requiring more frequent administration, BW-20805 is emerging as a promising candidate capable of transforming long-term disease management through durable efficacy and convenient dosing.
Phase 2 Results Show Significant Reduction in HAE Attacks
The updated Phase 2 data demonstrate robust clinical activity across all evaluated treatment groups. As of the study cutoff date, 18 patients had been randomized and dosed, with 16 participants providing post-treatment data beyond Day 29. Investigators reported a 99% reduction in time-normalized HAE attack rates in patients receiving 600 mg every 24 weeks, with an impressive 83% of patients remaining completely attack-free. Additional treatment groups also demonstrated strong efficacy, including a 93% reduction in attack rates for the 300 mg every 24 weeks cohort and a 95% reduction in attack rates for the 300 mg every 12 weeks cohort.
Across these groups, a substantial proportion of patients achieved complete elimination of attacks, highlighting the potential of BW-20805 to provide durable protection against one of the most debilitating aspects of hereditary angioedema. The findings suggest that long-term disease control may be achievable with significantly reduced treatment frequency compared with currently available therapies.
Durable PKK Suppression Supports Long-Acting Treatment Potential
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BW-20805 is designed to target hepatic prekallikrein (PKK) messenger RNA, reducing production of a key protein involved in the kallikrein-kinin pathway that drives HAE attacks. Updated biomarker data demonstrated rapid and sustained suppression of PKK levels across all dosing groups. Among 17 participants with available post-dose PKK measurements, average reductions exceeded 94% in pooled 300 mg treatment groups and 96% in the 600 mg every-24-week cohort by Day 85. Furthermore, participants who completed 169 days of follow-up maintained greater than 90% PKK suppression, providing strong evidence of prolonged biological activity.
This sustained target engagement supports the possibility of administering BW-20805 only twice annually while maintaining meaningful disease control. The ability to combine profound efficacy with extended dosing intervals could offer a substantial quality-of-life advantage for patients, reducing treatment burden while maintaining consistent protection against recurrent swelling attacks.
Favorable Safety Profile Advances Clinical Development
Safety findings from the ongoing study continue to support the advancement of BW-20805 into later-stage clinical development. Across all 18 treated participants, the therapy was generally well tolerated, with no drug-related serious adverse events, no severe treatment-related adverse events, and no discontinuations due to treatment-emergent adverse events. The most commonly reported adverse event was mild, transient injection-site reactions that resolved without medical intervention. These safety observations are particularly important given the chronic nature of hereditary angioedema and the need for long-term preventive treatment. HAE affects approximately 1.5 individuals per 100,000 people worldwide and can cause sudden episodes of severe swelling affecting the skin, gastrointestinal tract, and airways. In severe cases, airway involvement can become life-threatening.
As Argo Biopharma continues to expand its RNAi development portfolio, BW-20805 is emerging as one of the company’s most promising rare disease programs. The positive Phase 2 results strengthen confidence in the therapy’s potential to become a differentiated, long-acting treatment option capable of significantly improving outcomes for patients living with hereditary angioedema.
Source: Argo Biopharma press release
