Argo Biopharma Reports Updated Phase 2 Data for BW-20805 in Hereditary Angioedema

Investigational siRNA Therapy Shows Durable Reduction in HAE Attacks

Argo Biopharmaceutical Co., Ltd. has presented updated Phase 2 data for BW-20805, an investigational siRNA therapy being developed to prevent attacks in people with hereditary angioedema (HAE).

The updated findings from the ongoing Phase 2 study were selected for an oral presentation at the Bradykinin Symposium 2026, held in Berlin, Germany, on September 3-4.

The data showed that BW-20805 continued to produce substantial reductions in monthly HAE attack rates across all three dosing groups. The treatment also maintained strong suppression of plasma prekallikrein (PKK), an important protein involved in the pathway that drives HAE attacks.

The results also showed that the therapy was generally well tolerated, supporting Argo Biopharma's plans to continue developing BW-20805 as a potentially longer-acting preventive treatment.

What Is BW-20805?

BW-20805 is an investigational small interfering RNA, or siRNA, therapy.

The treatment is designed to silence the messenger RNA that produces plasma prekallikrein, also known as PKK. PKK is part of the biological pathway involved in hereditary angioedema.

By reducing the production of PKK in the liver, BW-20805 is intended to reduce the activity of this pathway and help prevent HAE attacks.

One of the main goals of the program is to provide longer-lasting protection with less frequent dosing.

This could be important for people with HAE because preventive treatments can require regular administration, creating an ongoing treatment burden.

Phase 2 Study Tested Three Dosing Schedules

The Phase 2 study is an open-label, global, multicenter clinical trial.

It is 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 received treatment across three dosing groups.

The groups received either 600 mg of BW-20805 every 24 weeks, 300 mg every 24 weeks, or 300 mg every 12 weeks.

The study's primary endpoint measured the change from baseline in the time-normalized monthly HAE attack rate between Days 29 and 169.

Researchers also evaluated safety, pharmacokinetics, and pharmacodynamics during the study.

HAE Attacks Fell Across All Treatment Groups

The updated results showed substantial reductions in HAE attack rates across all three BW-20805 dosing schedules.

Among the 24 participants included in the primary endpoint analysis, the mean time-normalized monthly attack rate decreased by 83% in the 600 mg every 24 weeks group.

The reduction was even greater in the 300 mg every 24 weeks group, where the monthly attack rate fell by 96%.

In the 300 mg every 12 weeks group, the monthly attack rate decreased by 93%.

These results indicate that BW-20805 produced a large reduction in attack frequency regardless of the dosing schedule tested.

The findings also support the company's interest in long-interval dosing, particularly the possibility of administering treatment only once every several months.

Some Patients Remained Attack-Free

The study also looked at how many participants experienced no HAE attacks during the evaluation period from Day 29 through Day 169.

In the 600 mg every 24 weeks group, 50% of participants, or four out of eight, remained attack-free.

In the 300 mg every 24 weeks group, 75%, or six out of eight participants, remained attack-free.

In the 300 mg every 12 weeks group, 62.5%, or five out of eight participants, remained attack-free.

Argo Biopharma also reported that attacks became noticeably less frequent and milder after participants received BW-20805.

BW-20805 Maintained Strong PKK Suppression

The treatment also showed sustained pharmacodynamic activity.

Among the 19 participants whose PKK levels could be evaluated, plasma PKK levels remained substantially reduced through Day 169.

At that point, mean PKK reductions were 86% in the 600 mg every 24 weeks group, 85% in the 300 mg every 24 weeks group, and 94% in the 300 mg every 12 weeks group.

These results are important because PKK is the specific biological target of BW-20805.

The sustained reduction suggests that the treatment can continue suppressing PKK for an extended period after dosing.

For Argo Biopharma, this supports the potential of BW-20805 to provide long-lasting preventive activity without requiring frequent administration.

Safety Results Remain Favorable

Safety was also assessed across all 25 participants who received BW-20805.

The company reported that the treatment was generally well tolerated across the three dosing groups.

Most treatment-emergent adverse events were mild.

Temporary injection-site reactions were the most common adverse events of special interest reported during the study.

Importantly, no treatment-emergent adverse event resulted in treatment discontinuation or withdrawal from the study. No deaths were reported.

The company also said that no participant met the protocol-defined criteria for hepatic laboratory abnormalities.

These findings will continue to be monitored as clinical development progresses.

Why Long-Acting Treatment Could Matter in HAE

Hereditary angioedema is a rare genetic condition that can cause sudden and unpredictable swelling in different parts of the body.

Swelling can affect the hands, feet, face, abdomen, and other areas. In severe cases, it can affect the throat and become a medical emergency.

The condition affects an estimated 1.5 people per 100,000 worldwide.

Because HAE attacks can happen unexpectedly, prevention is an important part of disease management.

However, current preventive approaches can require frequent treatment. Regular injections or other repeated dosing can become a significant burden for patients over time.

A treatment that can maintain protection for several months could therefore make preventive therapy easier to manage.

Targeting the Disease Pathway Instead of Treating Individual Attacks

One of the main ideas behind BW-20805 is to prevent HAE attacks by targeting an important part of the disease pathway.

Instead of waiting for an attack and then treating the symptoms, BW-20805 is designed to reduce PKK production before attacks occur.

The therapy uses RNA interference, or RNAi, technology to silence the messenger RNA responsible for PKK production in the liver.

By reducing PKK production, the company hopes to lower activity in the pathway associated with swelling attacks.

The strong PKK suppression observed through Day 169 provides clinical evidence that the treatment is engaging its intended biological target.

Argo Biopharma Sees Potential for Infrequent Dosing

The Phase 2 study is testing dosing schedules ranging from every 12 weeks to every 24 weeks.

The attack-rate reductions observed across these groups are particularly relevant to the company's goal of developing a long-acting preventive treatment.

The 300 mg every 24 weeks group recorded a 96% reduction in the mean monthly HAE attack rate.

The same dose administered every 12 weeks produced a 93% reduction.

While the study remains ongoing and additional data are needed, the findings suggest that BW-20805 could potentially provide sustained disease control with relatively infrequent administration.

Argo Biopharma Highlights the Updated Findings

Dr. Dongxu Shu, co-founder and chief executive officer of Argo Biopharma, said the updated Phase 2 findings provide further evidence supporting BW-20805 as a potential treatment for HAE prevention.

He highlighted the reduction in attack rates through Day 169, along with continued PKK suppression and the favorable safety profile seen so far.

According to Shu, these findings support continued development of BW-20805 as the company works to address the need for effective HAE therapies that do not require frequent dosing.

The oral presentation at the Bradykinin Symposium gives the scientific community an opportunity to review the updated clinical findings as the Phase 2 program continues.

What Comes Next for BW-20805?

The Phase 2 study remains ongoing.

The current data provide information on attack frequency, PKK suppression, and safety through Day 169, but additional follow-up will be needed to better understand the longer-term performance of BW-20805.

Researchers will continue evaluating the treatment across the different dosing schedules.

Further clinical development will also help determine the dose and dosing frequency that can provide the best balance of efficacy, safety, and convenience for people with HAE.

Argo Biopharma's Broader RNAi Pipeline

Argo Biopharma is a clinical-stage biotechnology company focused on developing next-generation RNAi therapies.

The company's pipeline includes investigational RNAi medicines targeting a range of diseases.

Its research programs cover cardiovascular diseases, viral infections, metabolic disorders, and specialty and rare diseases.

BW-20805 is part of this broader strategy and represents Argo Biopharma's effort to apply RNAi technology to a rare disease where long-lasting preventive treatment remains an important need.

The ongoing Phase 2 program will provide additional information on whether sustained PKK suppression with BW-20805 can translate into durable prevention of hereditary angioedema attacks with less frequent dosing.