FDA Grants Fast Track Designation to BW-20805 siRNA Therapy for HAE

The US Food and Drug Administration (FDA) has granted Fast Track designation to BW-20805, an investigational small interfering RNA (siRNA) therapy, for the treatment of hereditary angioedema (HAE). Argo Biopharmaceutical announced the news on March 16, 2026. 1

“Receiving FTD from the FDA highlights the significant unmet medical need for patients living with HAE and underscores the potential of BW-20805 as a novel therapeutic option," said Dongxu Shu, co-founder and chief executive officer of Argo Biopharma, in a statement.

The therapy is currently being evaluated in an ongoing global phase 2 open-label trial in adults with HAE, with primary study completion anticipated in the second half of 2026. Early clinical findings presented at the 2026 American Academy of Allergy, Asthma & Immunology (AAAAI) annual meeting in Philadelphia suggested that BW-20805 led to substantial pharmacodynamic suppression of prekallikrein and reductions in HAE attack frequency among treated participants.

“The drug BW-20805 is doing what we expect to do, reducing the plasma kallikrein activity and reducing it by more than 90% in a very stable way,” said investigator Markus Magerl, MD, from Charité-Universitätsmedizin Berlin, in an interview with HCPLive shortly after AAAAI.2

The trial continues to evaluate adults with HAE type 1 or 2 across 3 dosing regimens: 600 mg every 24 weeks, 300 mg every 24 weeks, and 300 mg every 12 weeks. As of February 2026, 80% of participants (n = 14; 10 with post-dose efficacy data) remained completely attack-free during the observation period. The 600 mg cohort experienced a 100% reduction in time-normalized HAE attack rates, compared to 89% and 97% reductions in the 300 mg every 24 weeks and every 12 weeks arms, respectively. Depending on the dosing regimen, prekallikrein levels declined by approximately 90% to 97% within the first month of administration and remained stable throughout follow-up.

BW-20805 uses RNA interference to silence messenger RNA encoding hepatic prekallikrein, the precursor of plasma kallikrein. By suppressing prekallikrein production in hepatocytes, the therapy is designed to reduce downstream activation of the kallikrein–kinin cascade and limit bradykinin formation, a key mediator of HAE attacks. The approach reflects a broader therapeutic strategy in HAE focused on inhibiting the kallikrein pathway, which has been validated by currently approved prophylactic agents such as the monoclonal antibody lanadelumab.3

Although these early findings suggest the potential for sustained suppression of the kallikrein pathway, investigators emphasized that the data remain preliminary. The phase 2 study has a relatively small sample size and an open-label design, which may introduce bias in reporting attack outcomes.2 Longer follow-up will be necessary to determine the durability of pharmacologic suppression and to assess long-term safety.

The phase 2 trial of BW-20805 is expected to reach primary completion later in 2026. Following completion of this study, Argo Biopharma has indicated plans to initiate a global phase 3 trial.

“We look forward to advancing the clinical development of BW-20805 and bringing a potentially long-acting treatment option to patients as effectively as possible,” Shu said.

References

1. PR Newswire. Argo Biopharma Receives FDA Fast Track Designation for BW-20805, an Investigational siRNA Therapy for the Treatment of HAE. Prnewswire.com. Published March 16, 2026. Accessed March 16, 2026. https://www.prnewswire.com/news-releases/argo-biopharma-receives-fda-fast-track-designation-for-bw-20805-an-investigational-sirna-therapy-for-the-treatment-of-hae-302714159.html

2. Magerl M. BW-20805 Reduces HAE Attacks in Phase 2 Trial, With Markus Magerl, MD. HCPLive. Published on March 10, 2026. Accessed on March 16, 2026. https://www.hcplive.com/view/bw-20805-reduces-hae-attacks-phase-2-trial-markus-magerl-md

3. FDA Approves Lanadelumab for Hereditary Angioedema. Hcplive.com. Published August 24, 2018. Accessed March 16, 2026. https://www.hcplive.com/view/fda-approves-lanadelumab-for-hereditary-angioedema