Six-month BW-20805 regimen cuts monthly HAE attack rates by up to 99%
Open-label Phase 2 data support further testing of twice-yearly dosing
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A six-month dosing regimen of Argo Biopharma‘s long-acting investigational therapy BW-20805 reduced monthly attacks in people with hereditary angioedema (HAE) by up to 99%.
That’s according to new data from an ongoing open-label Phase 2 clinical trial (NCT06846398) testing the therapy in up to 25 adults, ages 18-70, with HAE type 1 or type 2. The findings support the further evaluation of a six-month dosing regimen, which could require less frequent dosing than currently approved preventive HAE therapies, which are given daily or every two to four weeks.
Updated trial data will be presented in a late-breaking poster session at the European Association of Allergy & Clinical Immunology (EAACI) 2026 Congress, held this month in Turkey, the company announced in a press release.
BW-20805 may offer longer dosing intervals
“We are pleased that the updated analysis from the ongoing Phase 2 data for BW-20805 has been selected for presentation at EAACI 2026,” said Dongxu Shu, PhD, co-founder and CEO of Argo. “We look forward to sharing the latest findings and advancing our efforts to develop a potentially meaningful treatment option for patients.”
HAE is a rare disorder caused by genetic mutations that can lead to excessive production of bradykinin, a signaling molecule that causes blood vessels to leak fluid into surrounding tissue, resulting in swelling (angioedema). Attacks can occur in the abdomen, limbs, face, and airway, and are unpredictable in timing and severity.
Currently approved preventive (prophylactic) therapies can reduce swelling attacks but require dosing either every two to four weeks or daily.
BW-20805 is being developed for longer dosing intervals of three to six months and is given as a subcutaneous, or under-the-skin, injection. The therapy uses a small interfering RNA to target the messenger RNA that carries instructions for producing prekallikrein, or PKK, in liver cells. PKK is converted into kallikrein, an enzyme involved in bradykinin generation.
By acting at the level of gene activity in liver cells and persisting within those cells for extended periods, a single injection can suppress PKK production for weeks or months, lowering plasma PKK levels and reducing bradykinin generation, thereby lowering the frequency of attacks.
In March, the U.S. Food and Drug Administration (FDA) granted fast-track status to BW-20805. This designation is intended to accelerate the development and review of therapies for serious conditions that address unmet medical needs.
HAE attack rates fell across dosing groups
So far, the Phase 2 study has randomized and dosed 18 participants across three treatment groups, testing 600 mg and 300 mg doses every 24 weeks (about six months) and 300 mg doses every 12 weeks (about three months). The study’s main goal is a change in the monthly HAE attack rate from before treatment to 24 weeks.
Of those dosed, 16 had post-dose data beyond Day 29, and 17 had post-dose PKK data available.
Among those given BW-20805 every six months, the monthly HAE attack rate was reduced by 99% in the 600 mg group and 93% in the 300 mg group. More participants in the 600 mg group remained attack-free (83% vs. 60%). Similarly, those who received 300 mg of BW-20805 every three months showed a 95% reduction in HAE attack rate, with 60% attack-free.
In the pooled 300 mg groups, average plasma PKK reductions exceeded 94% by Day 85 (about three months), while the 600 mg every six months group saw average reductions exceeding 96% by the same point. Among participants who completed 169 days, or about 24 weeks, of follow-up, average PKK reductions exceeded 90% across all three groups.
“The sustained and robust PKK suppression supports further evaluation of a [six-month] dosing regimen,” the company stated in its release.
Regarding safety, BW-20805 was well tolerated across all 18 participants. No drug-related serious or severe adverse events were reported, and no participants discontinued the study due to a treatment-emergent adverse event. The most common adverse event was an injection site reaction, described as mild and transient, resolving without medication.
According to Shu, the updated analysis “reflects the continued strength and progress of the program.”
