-Global Phase II open-label study in adult HAE patients ongoing, company on track for primary completion of study in the second half of 2026

SHANGHAI, CHINA and NEW YORK, USA-March 16, 2026—Argo Biopharmaceutical Co., Ltd. (Argo Biopharma), a clinical-stage small interfering RNA (siRNA) therapeutics company, today announced that the U.S. Food and Drug Administration (FDA) has granted Fast Track Designation (FTD) to its novel siRNA therapy BW-20805, for the treatment of hereditary angioedema (HAE) .

BW-20805 is an investigational siRNA therapy that targets and significantly inhibits prekallikrein (PKK), a well-validated target for hereditary angioedema (HAE) treatment, offering the possibility of prevention of HAE attacks with a long-term effect. Argo Biopharma is currently conducting a global Phase II study in adult HAE patients. The Company anticipates primary completion of the Phase II study in the second half of 2026, followed by plans for a global Phase III study.

“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 Dr. Dongxu Shu, co-founder and Chief Executive Officer of Argo Biopharma. “We have generated a robust body of clinical evidence supporting BW-20805’s potential, including recent open-label study results presented at the AAAAI Annual Meeting, which demonstrated that BW-20805 provides remarkable plasma PKK reduction and meaningful time-normalized HAE attack rate reduction. 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.”

About Fast Track Designation (FTD)

The FDA's Fast Track designation is a program designed to facilitate the development and expedite the review of drugs intended to treat serious conditions that demonstrate the potential to address an unmet medical need. Fast Track designation allows for early and frequent communication with the FDA throughout the entire drug development and review process, and allows for a rolling review of a company's New Drug Application (NDA). Products with Fast Track designation may also be eligible for Priority Review, if relevant criteria are met at the time of NDA filing.

About Hereditary Angioedema (HAE)

Hereditary angioedema (HAE) is a rare genetic condition that causes sudden and unpredictable swelling in different parts of the body. In severe cases, it can affect the throat and become life-threatening, with a mortality rate of up to 40% ¹. HAE affects about 1.5 people per 100,000 worldwide ². Current prophylactic treatments are limited by frequent dosing, highlighting the need for long-acting, preventive therapies. BW-20805 targets human hepatic PKK mRNA to inhibit PKK gene expression, offering the potential for effective prevention of HAE attacks with a significant and longer-lasting therapeutic effect.

About Argo Biopharma

Argo Biopharma is a clinical-stage biotechnology company committed to developing next-generation RNAi therapeutics to provide better treatment options for patients worldwide. The company has established a robust and diverse pipeline of RNAi molecule candidates targeting a wide range of indications, including cardiovascular diseases, viral infections, metabolic conditions, and specialty/rare diseases. Currently, Argo Biopharma has seven RNAi candidates in clinical development.

For more information, please visit www.argobiopharma.com .

INVESTOR & MEDIA INQUIRIES
Argot Partners
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References：

1. Giavina-Bianchi P, et al. (2011). CLINICS 66(9): 1627–1636.

2. Aygören-Pürsün, E, et al. (2018). Orphanet J Rare Dis 13(1): 73.