ArkBio's RSV Antiviral Ziresovir Receives FDA Approval for Phase II Trial in Critically Ill Infants
核心洞察
Shanghai Ark Biopharmaceutical Co., Ltd. announced FDA approval of ziresovir (AK0529) for a phase II clinical trial in severely ill RSV-infected infants, including those in the pediatric intensive care unit (PICU).
Ziresovir is the first direct RSV antiviral drug to successfully complete a phase III trial with positive results, demonstrating reduced viral load and accelerated symptom resolution.
RSV causes approximately 33 million lower respiratory tract infection cases, 3.6 million hospitalizations, and more than 100,000 deaths annually, with no approved RSV-specific antiviral therapy currently available worldwide.
Shanghai Ark Biopharmaceutical Co., Ltd. ("ArkBio") announced on Aug. 14, 2026 that the U.S. Food and Drug Administration (FDA) has approved ziresovir (AK0529) for a phase II clinical trial in severely ill RSV-infected infant patients, including those admitted to the pediatric intensive care unit (PICU). The approval marks a key milestone in the global clinical development of ziresovir, extending its evaluation into the most critically ill RSV patient population.
Severe RSV Infection: An Urgent Unmet Need in PICU
Respiratory syncytial virus (搜索) (RSV) is the leading pathogen of lower respiratory tract infections (搜索) (LRTIs) in infants and young children globally, causing approximately 33 million LRTI cases, 3.6 million hospitalizations, and more than 100,000 deaths annually. Severely ill RSV-infected infants often require admission to the PICU for intensive care such as respiratory support, with rapid disease progression, high risk, and a heavy medical burden.
There is currently no approved RSV-specific antiviral therapy worldwide. Clinical management remains limited to symptomatic and supportive care, such as oxygenation, leaving an urgent unmet need for effective antiviral treatment in hospitalized RSV-infected patients with severe disease.
Ziresovir Advances to Treat Severely Infected Infant Patients
Ziresovir is the first direct RSV antiviral drug to successfully complete a phase III clinical trial with positive results. The clinical study conducted in China in patients aged 1–24 months demonstrated that ziresovir can significantly reduce viral load, accelerate the resolution of respiratory symptoms, and significantly lower the risk of recurrent wheezing and asthma over a 24-month follow-up period, with a favorable safety profile.
Key findings from the clinical study have been published in The New England Journal of Medicine and The Lancet Child & Adolescent Health. In 2025, ziresovir was included as the only therapeutic drug in the WHO's Paediatric Drug Optimization for Respiratory Syncytial Virus (搜索) publication.
FDA-Approved Phase II Clinical Trial Design
The newly approved multicenter, randomized, double-blind, placebo-controlled phase II clinical trial will focus on severely ill RSV-infected infants requiring hospitalization in the PICU, one of the most critical RSV patient populations with the most urgent clinical treatment needs. The trial is designed to evaluate the clinical efficacy of ziresovir, especially the length of oxygen treatment and sustained recovery time, providing the clinical basis for future registrational trials.
About ArkBio
ArkBio is a commercial-stage biotechnology company focused on the discovery and development of innovative therapeutics for respiratory/lung and pediatric diseases. Founded in 2014, the company has established proprietary technology platforms and a differentiated R&D pipeline through internal innovation and strategic collaborations.
Key pipeline assets include ziresovir (AK0529), the first direct-acting antiviral for RSV with positive phase 3 results; AK3280, a potentially best-in-class anti-fibrotic agent with positive phase 2 results in idiopathic pulmonary fibrosis, currently in phase 3 registrational trials; and AK0901, approved and commercialized in China for ADHD treatment. ArkBio has established strategic partnerships with multinational pharmaceutical companies including Roche and Genentech, leading academic institutions including The Scripps Research Institute and the Institute of Microbiology of the Chinese Academy of Sciences, Qilu Pharmaceutical, as well as other domestic and international biotech companies and CROs.