-Poster Presentation Selected as Late Breaking Abstract-

SHANGHAI, CHINA and BOSTON, MA, USA-February 26, 2026—Argo Biopharmaceutical Co., Ltd. (Argo Biopharma), a clinical-stage small interfering RNA (siRNA) therapeutics company, has been selected as a late breaking abstract to present Phase II interim data for BW-20805 during the American Academy of Allergy, Asthma & Immunology (AAAAI) 2026 Annual Meeting on February 27-March 2, 2026.

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.

"The selection of our Phase II interim data as a late breaking abstract presentation at the AAAAI Annual Meeting recognizes the strength and growing body of evidence supporting BW-20805, and highlights its potential to deliver remarkable, sustained reductions in HAE attack rates and rapid, profound suppression of plasma PKK levels along with a favorable safety profile that is well tolerated across all dose levels. The strength of this clinical data support further evaluation of a potentially best-in-class dosing regimen for patients' prophylactic needs," said Dr. Dongxu Shu, co-founder and Chief Executive Officer of Argo Biopharma.

The open-label study results, selected as a late breaking abstract presentation, titled "Significant HAE Attack Reduction with BW-20805, a Long-Acting Prophylactic Injection-An Ongoing Phase 2 Study in Adults with Hereditary Angioedema" (POSTER ID: L42), show that BW-20805 provides remarkable plasma PKK reduction, along with meaningful time-normalized HAE attack rate reduction. The sustained PKK suppression and the favorable safety and tolerability profile support further evaluation of a Q6M dosing regimen.

Key Data Highlights:

• As of cut-off, time-normalized HAE attack rate decreased by 100% in the 600 mg Q24W group, 89% in the 300 mg Q24W group, and 87% in the 300 mg Q12W group. Additionally, 80% (8/10) of treated patients remained attack-free.

• Plasma PKK levels showed a rapid and profound decrease. On Day 85, in the pooled 300 mg groups (Q24W and Q12W), the mean reduction in plasma PKK exceeded 92%; for 600 mg Q24W group, PKK reduction reached approximately 97%.

• Among the participants who completed 169 days of follow-up, PKK reductions were sustained at 98% in the 300 mg Q12W group and 97% in the 600 mg Q24W group on Day 169, respectively.

• BW-20805 was generally well tolerated, with mainly mild, transient injection-site reactions and no serious adverse events observed.

• These results demonstrate the robust pharmacodynamic effect of BW-20805 combined with the favorable safety and tolerability profile, supporting its potential as a long-acting prophylactic therapy for HAE.

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 treatments require 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
argobiopharma@argotpartners.com

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.