The Lancet Child&Adolescent Health Publishes Phase III Trial and 24-Month Follow-Up Results of Ziresovir for RSV in Infants Under 6 Months

SHANGHAI,April 16, 2025/PRNewswire/ --The Lancet Child& Adolescent Health, a leading international journal in pediatric and adolescent medicine, has published the Phase III clinical trial results ofziresovir, a novel RSV-targeted antiviral drug developed by Shanghai Ark Biopharmaceutical Ltd. The article, titled"Efficacy and safety of ziresovir in hospitalised infants aged 6 months or younger with respiratory syncytial virus infection inChina: findings from a phase 3 randomised trial with 24-month follow-up", presents detailed subgroup analysis of infants under six months of age, following the primary results published inThe New England Journal of MedicineinSeptember 2024.

RSV: An Urgent Unmet Medical Need

Respiratory syncytial virus (RSV) is a leading cause of hospitalization and mortality in children under six years old. With millions of cases annually worldwide, especially among infants under six months, RSV imposes a significant burden on families and healthcare systems. Current treatments are limited to symptomatic and supportive care, with no approved direct-acting antiviral therapies available.

Ziresovir's Phase III results mark a significant milestone, representing thefirst clinical validation of an antiviral's efficacy in hospitalized infants ≤6 months, and demonstratinglong-term benefits in reducing recurrent wheezing and asthma.

Study Design

This multicenter, randomized, double-blind, placebo-controlled Phase III trial was conducted at 30 sites in 28 hospitals acrossChina. The trial included two parts:

• Part 1assessed safety and pharmacokinetics
• Part 2evaluated clinical efficacy and antiviral effects

Infants were randomized in a 2:1 ratio to receive ziresovir or placebo for five days, with a 24-month follow-up. The latest publication focuses on infants aged six months or younger.

Key Findings

1. Significant Efficacy

• Improved Bronchiolitis Symptoms:By Day 3, ziresovir-treated infants had a 3.5-point reduction in Wang Bronchiolitis Clinical Score (WBCS), compared to 2.2 points in the placebo group—a 54.5% difference (p<0.001). Improvements in respiratory rate, wheezing, and retractions were also statistically significant (p<0.05).
• Rapid Viral Load Reduction:By Day 5, viral load decreased by 2.51 log₁₀ copies/mL in the treatment group, versus 1.87 log₁₀ in the placebo group (p=0.024), confirming ziresovir's antiviral activity.
• Faster Symptom Relief:Time to wheezing resolution (HR=1.53,p=0.021) and retraction relief (HR=1.49,p=0.018) were shorter in the treatment group. Hospital stay and oxygen use showed a reduction trend, though not statistically significant.

2. Long-Term Safety and Respiratory Health Benefits

• Favorable Safety Profile:Treatment-emergent adverse events (TEAEs) occurred in 18% of the treatment group vs. 11% in placebo. No drug-related severe adverse events or deaths were reported.
• Reduced Risk of Recurrent Wheezing and Asthma:
• Wheezing incidence was 3.6 times lower in the treatment group (0.18% vs. 0.65%,p=0.0048).
• Wheezing episodes were reduced by 2.6 times (1.2 vs. 3.1 episodes).
• Asthma rates were also lower (3% vs. 5%).

These long-term benefits suggest early antiviral intervention may reduce the risk of chronic respiratory conditions.

A New Era in RSV Treatment

Unlike existing RSV treatments focused solely on symptom relief, ziresovir is thefirst RSV-targeted antiviral therapywith demonstrated clinical efficacy in infants under six months—those most at risk of severe complications. These findings introduce a new therapeutic paradigm for RSV treatment and prevention of long-term sequelae.

The results were presented byDr.Jim Wu, CEO of ArkBio, at the 13th International RSV Symposium inBrazil, receiving recognition from the global RSV research community.

Prof.Xin Ni, principal investigator of the Airflo study and professor at Beijing Children's Hospital, Capital Medical University, commented:

"This pivotal Phase III trial provides the first solid evidence of an effective antiviral treatment for RSV in high-risk infants. Following our initial publication inThe New England Journal of Medicine, this deeper analysis in infants under six months published inThe Lancet Child& Adolescent Healthfurther validates ziresovir's safety, efficacy, and long-term benefit. We are proud of our team's commitment and look forward to bringing this drug to patients inChinaand worldwide."

For public readers, the article can be accessed at the following link:

https://www.thelancet.com/journals/lanchi/article/PIIS2352-4642(25)00067-7/fulltext 

About Ziresovir

Ziresovir is a first-in-class, oral small-molecule inhibitor targeting the RSV fusion (F) protein. It prevents viral entry and cell-to-cell transmission by blocking syncytia formation, a hallmark of RSV infection. It is the first oral RSV antiviral to successfully complete a pivotal Phase III trial with positive results and has been grantedBreakthrough Therapy Designationby the National Medical Products Administration (NMPA) ofChina.

About ArkBio

ArkBiois a global biotech company focused on developing innovative therapies for respiratory, infectious, and pediatric diseases. Founded in 2014, it has built core technology platforms and a differentiated R&D pipeline through in-house research and collaborations. Key assets includeziresovir, the first direct-acting RSV antiviral with positive pivotal phase III results globally, andAK0901, an FDA-approved pediatric ADHD therapy with commercialization rights inGreater China.

ArkBiohas established strategic partnerships with several multinational pharmaceutical companies and academic institutes, including Roche, Genentech, theScripps Research Institute, the Institute of Microbiology, Chinese Academy of Sciences, domestic and international biotechnology companies, as well as venture investment institutions.

For more information about the company, please visit our website:www.arkbiosciences.com 

Investor Inquiries:IR@arkbiosciences.com

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