Argo Biopharma Reports Positive Phase II Data for BW-20805 in HAE

Shanghai, China and New York, USA, September 4, 2026

BW-20805 Shows Strong Reduction in HAE Attack Rates

The updated results came from an open-label, global, multicenter Phase II study evaluating BW-20805 in adults with type 1 or type 2 hereditary angioedema. As of the June 2026 data cutoff, 25 participants had been randomized and dosed across three treatment groups: 600 mg every 24 weeks, 300 mg every 24 weeks, and 300 mg every 12 weeks. The primary endpoint assessed the change from baseline in the time-normalized monthly HAE attack rate from Day 29 through Day 169, while safety, pharmacokinetics and pharmacodynamics were evaluated as secondary measures. In the primary endpoint analysis population of 24 participants, BW-20805 produced substantial reductions in monthly HAE attack rates across all three regimens. The mean time-normalized monthly attack rate declined by 83% with 600 mg every 24 weeks, 96% with 300 mg every 24 weeks, and 93% with 300 mg every 12 weeks. The study also found that attacks became markedly less frequent and milder following treatment. The proportion of participants who remained attack-free between Day 29 and Day 169 was 50% in the 600 mg Q24W group, 75% in the 300 mg Q24W group and 62.5% in the 300 mg Q12W group.

Sustained PKK Suppression Supports Long-Interval Dosing

BW-20805 is designed to silence PKK messenger RNA in the liver, reducing production of prekallikrein and potentially limiting downstream bradykinin generation, a key biological pathway associated with swelling attacks in HAE. This RNA interference approach is intended to provide durable pharmacological activity while potentially reducing the frequency of preventive treatment. The updated pharmacodynamic findings supported sustained target suppression. Among the 19 participants evaluable for PKK, mean plasma PKK reductions at Day 169 reached 86% for 600 mg Q24W, 85% for 300 mg Q24W and 94% for 300 mg Q12W. These results are particularly relevant to Argo Biopharma’s objective of developing a long-acting preventive therapy that could require substantially fewer administrations than frequently dosed HAE treatments. Earlier 2026 data had also indicated robust and sustained attack-rate reductions, supporting continued evaluation of longer dosing intervals.

BW-20805 Generally Well Tolerated in Phase II Study

The safety analysis included all 25 treated participants, with treatment-emergent adverse events described by the company as predominantly mild. Transient injection-site reactions were the most common adverse events of special interest. Importantly, no treatment-emergent adverse event resulted in treatment discontinuation, study withdrawal or death, and no participant met the protocol-defined hepatic laboratory criteria. HAE is a rare genetic disorder characterized by unpredictable episodes of swelling, which can affect the skin, gastrointestinal tract and, in severe cases, the upper airway. Because recurrent attacks can be serious or potentially life-threatening, effective long-term prophylaxis remains an important area of therapeutic development. Argo Biopharma previously reported that BW-20805 received FDA Fast Track designation, highlighting the company’s ongoing efforts to advance the investigational program. The latest findings strengthen the clinical rationale for further development of BW-20805 as a potentially long-acting HAE prophylactic therapy. However, the candidate remains investigational, and the Phase II findings will need to be confirmed in later-stage clinical development before any conclusions can be drawn regarding regulatory approval or routine clinical use.

Source: Argo Biopharma press release