China-Developed Pediatric Innovation Drug Ziresovir Included in WHO Priority List for RSV Mediciness

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On 16 July 2025, the World Health Organization (WHO), together with its Global Accelerator for Paediatric Formulations Network (GAP-f), released the RSV Paediatric Drug Optimization (PADO-RSV) Meeting Report. Ziresovir (10 mg), an innovative antiviral drug targeting respiratory syncytial virus (RSV), was formally included in the WHO PADO-RSV priority list for pediatric RSV medicines.

The drug was developed by Shanghai Ark Biopharmaceutical Co., Ltd., and its Phase III clinical trial was led by Professor Xin Ni's team at the National Center for Children's Health, Beijing Children's Hospital, Capital Medical University, under the National Major Scientific and Technological Special Project for “Significant New Drug Development” — Pediatric Drug Varieties and Key Technology R&D Platform.

Ziresovir is the first and only RSV antiviral therapeutic currently included in the PADO-RSV priority list. It also represents the first time that a China-developed anti-RSV medicine has been incorporated into the WHO/GAP-f pediatric drug optimization priority framework. Its inclusion marks an important milestone for China-developed pediatric innovation medicines and highlights their growing contribution to global public health efforts.

Global Burden of RSV and the Need for Targeted Therapies

RSV is the leading cause of lower respiratory tract infections among infants and young children worldwide. Each year, RSV is responsible for approximately 33 million episodes of lower respiratory tract infection in children under five years of age, 3.6 million hospitalizations, and an estimated 101,400 deaths. Approximately 97% of RSV-related deaths occur in low- and middle-income countries.

Despite its substantial disease burden, specific antiviral treatment options for RSV remain limited. There is an urgent need for safe, effective, and child-appropriate antiviral medicines.

The WHO/GAP-f “RSV Paediatric Drug Optimization (PADO-RSV)” initiative aims to systematically review the global RSV development pipeline, define research and development priorities, and promote the development and global accessibility of optimized preventive and therapeutic medicines for children.

Mechanism of Action and Clinical Evidence

Ziresovir is a novel small-molecule inhibitor targeting the RSV fusion (F) protein. By binding to the viral F protein, it prevents viral entry into host cells and blocks virus-induced cell-to-cell fusion, thereby inhibiting the formation of syncytia — a characteristic feature of RSV infection — and exerting antiviral effects.

The Phase III clinical trial was conducted through collaboration between Professor Xin Ni's team and Shanghai Ark Biopharmaceutical Co., Ltd. The study demonstrated:

　　· A favorable safety profile

　　· Significant antiviral efficacy

　　· Rapid symptom improvement

　　· Sustained clinical benefit

The clinical findings have been published in The New England Journal of Medicine and The Lancet Child & Adolescent Health. Ziresovir is the first targeted RSV antiviral globally to successfully complete a Phase III clinical trial with positive outcomes. It represents a key candidate addressing a long-standing unmet therapeutic need in RSV treatment for children.

With its demonstrated safety profile, clear clinical value, and child-friendly formulation design, Ziresovir is the only antiviral agent currently included in the PADO-RSV priority list. Its continued development and broader implementation have the potential to significantly expand global therapeutic options for RSV in children and enhance access to safe, effective, and affordable treatment for children worldwide.

About GAP-f

The Global Accelerator for Paediatric Formulations Network (GAP-f) is hosted by the World Health Organization. It works across the medicine development lifecycle to accelerate the research, development, and uptake of optimized pediatric formulations.

Priority setting is a critical step toward targeted research and development. Identifying a portfolio of urgently needed pediatric formulations helps align global researchers, manufacturers, and other stakeholders around medicines and dosage forms that address the most pressing needs of children.

About PADO

Paediatric Drug Optimization (PADO) is a WHO initiative mandated under World Health Assembly Resolution WHA69.20. It provides a structured international priority-setting mechanism to accelerate the development of urgently needed pediatric medicines through consensus among regulatory authorities, funders, and manufacturers.

PADO work includes identifying priority products for development and outlining preferred product characteristics. The approach has been implemented in areas including HIV, hepatitis C, tuberculosis, COVID-19, antibiotics, tropical diseases, and pediatric oncology. In the context of fragmented and relatively small pediatric medicine markets, this mechanism has demonstrated practical value in accelerating the availability of optimized pediatric formulations.

Reference

World Health Organization. RSV Paediatric Drug Optimization (PADO-RSV) Meeting Report. Geneva: World Health Organization; 2025. Available at: https://www.who.int/publications/i/item/B09464