New trial data show lasting cuts in HAE attacks with long-acting drug
Benefits seen for about 6 months after 1 use of injection therapy
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New trial data show that BW-20805, Argo Biopharma‘s long-acting injection therapy for hereditary angioedema (HAE), continues to substantially reduce swelling attacks among adults with HAE for as long as six months after treatment.
These findings come from a larger group of people with HAE taking part in the international Phase 2 clinical trial (NCT06846398) than data reported in an earlier analysis this year. The ongoing midstage trial is testing the safety and effectiveness of the experimental therapy in reducing HAE attacks in adults.
According to the researchers, the therapy candidate — administered only once every three or six months — also continued to lower levels of plasma prekallikrein (PKK), the protein targeted by BW-20805.
“The updated Phase [2] results … provide continued clinical evidence for BW-20805’s differentiated potential in HAE prophylaxis,” Dongxu Shu, PhD, Argo’s cofounder and CEO, said in a company press release providing “key data highlights.”
The updated trial data were presented at the Bradykinin Symposium 2026, held earlier this month in Germany.
A chronic condition, HAE is caused by genetic mutations that lead to the overproduction of bradykinin, a protein that causes blood vessels to dilate and leak fluid into surrounding tissues. This triggers unpredictable swelling attacks that can affect the abdomen, limbs, face, and airways.
Currently approved HAE treatments require frequent dosing
While several therapies are approved to prevent swelling attacks, they require either daily dosing or regular dosing every two to four weeks. BW-20805 is designed to be given at dosing intervals of 3-6 months, which is expected to ease the treatment burden for patients.
The therapy candidate uses a small interfering RNA (siRNA) that aims to block the production of PKK — the precursor of kallikrein, an enzyme involved in bradykinin generation — in liver cells. It is being developed for subcutaneous, or under-the-skin, injections.
The Phase 2 trial is open-label, meaning both researchers and participants know the treatment being given. It’s testing BW-20805’s safety and effectiveness in reducing HAE attacks in 25 people ages 18 to 70 with HAE type 1 or type 2. Each participant was randomly assigned to receive one of three dosing regimens: 600 or 300 mg once every six months, or 300 mg once every three months, for almost two years.
As of the June data cutoff, all participants had been randomized and treated across the three groups. The updated primary analysis covered 24 participants and assessed changes in the monthly HAE attack rate through day 169, or about the 5.5-month mark.
The new data show monthly attack rates fell by an average of 83% among participants receiving 600 mg every six months and 96% among those receiving 300 mg every six months. Among those receiving 300 mg every three months, monthly attack rates dropped by 93%. In all three regimens, attacks also became markedly milder after dosing, according to the researchers.
The analysis also reported the proportion of participants who experienced no HAE attacks during the assessment period. Half of those receiving BW-20805 at 600 mg every six months remained attack-free, compared with 75% of those receiving 300 mg every six months and 63% of those receiving the treatment every three months.
Additionally, among 19 participants with available PKK data, average blood PKK levels were reduced by about 85% for those receiving treatment every six months, and by 94% in those receiving treatment every three months.
These findings are particularly relevant to the company’s goal of developing a preventive, or prophylactic, HAE treatment that can be given less frequently than many existing options.
BW-20805 safe, tolerated well across dosing regimens
Safety data from all 25 treated participants showed that the therapy was generally well tolerated across all dosing regimens. Treatment-emergent adverse events were mostly mild, with temporary injection-site reactions being the most common.
No adverse event led to treatment discontinuation or withdrawal, and no deaths were reported. None of the participants met the study’s predefined criteria for liver-related laboratory abnormalities.
“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 as we work to address the need for effective therapies with less frequent dosing,” Shu said.
Earlier this year, the U.S. Food and Drug Administration granted fast track status to BW-20805. That designation aims to accelerate the development and review of drugs designed to address unmet medical needs in serious conditions.
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