Ark Biosciences Reports Successful Completion of Phase II Proof-of-Concept Clinical Trial of Ziresovir for Treatment of Infants Hospitalized with Respiratory Syncytial Virus (RSV) Infection
Release date:2019-04-11

SHANGHAI, CHINA - November 6, 2019 - Ark Biosciences, a global biotech company developing innovative therapeutics for viral infection and respiratory diseases, today announced positive topline results of its Phase II proof-of-concept study of Ziresovir (AK0529).

For the first time ever, an antiviral agent has proven successful in treating infants hospitalized with Respiratory Syncytial Virus (RSV) infection. In the successfully completed phase II VICTOR (Viral Inhibition in Children for Treatment Of RSV) study for the treatment of infants hospitalized with RSV infection, Ziresovir, Ark Bioscience´s proprietary antiviral, demonstrated a clear dose-dependent clinical efficacy. It reduced patients’ signs and symptoms scores and concomitantly viral loads.

The study, “A Randomized, Double-blind, Placebo-controlled, 2-Part Study of Orally Administered AK0529 (Ziresovir) to Evaluate the Safety, Tolerability, Pharmacokinetics and Antiviral Effect of Single and Multiple Dosing in Hospitalized Infants with Respiratory Syncytial Virus Infection”, demonstrated significant clinical benefits and efficacy in reducing signs and symptoms, in both single and multiple doses. It also demonstrated a significant antiviral effect compared to placebo. This study further confirmed Ziresovir’s excellent drug safety profile from Phase I studies, with no drug related SAEs, no AEs of concern and no particular AE pattern. There were also no concerns raised with hematology, clinical chemistry, ECGs and vital signs. The detailed clinical results will be published and reported at medical conferences in due course. As a result of this positive Proof of Concept study, Ark Biosciences is pleased to announce that it is proceeding with Phase III registration trials.

Ark Bioscience´s anti-RSV drug Ziresovir, a novel RSV F-protein inhibitor, has completed multiple clinical studies with the molecule, including two phase I clinical studies in healthy adult volunteers in Australia and China respectively, and one phase I human mass balance study in the United Kingdom.

Dr Stephen Toovey, MD PhD, Chief Medical Officer of Ark Biosciences, said: “There is an enormous need for an efficacious medication to treat the millions of pediatric and elderly patients who suffer RSV infection every year. In the completed phase II VICTOR study for the treatment of infants hospitalized with RSV infection, this is the first time that an antiviral agent has shown clinical benefit for these RSV infected patients. Ziresovir clearly demonstrated dose-dependent clinical efficacy and clearly reduced viral loads in treated patients”.  Dr Jim Wu, CEO of Ark Biosciences, commented: "We have made great progress in the clinical development of Ziresovir as first-line antiviral therapy for the treatment of RSV infected patients, especially in hospitalized infants. With the development of Ziresovir, Ark aims to be the industry leader in anti-RSV drug development, and to develop the first-in-disease anti-RSV drug to satisfy the extremely large unmet medical need posed by RSV infection". 

About the VICTOR Study

The “VICTOR” study that stands for “Viral Inhibition in Children for Treatment Of RSV” was a Phase II, Randomized, Double-blind, Placebo-controlled Study of Orally Administered AK0529 to Evaluate the Safety, Tolerability, Pharmacokinetics and Antiviral Effect of Single and Multiple Dosing in Hospitalized Infants with RSV Infection. It enrolled 73 hospitalized RSV infected infant patients at the age of 1 to 24 months old and was conducted in Australia, Taiwan, Malaysia, Israel and Turkey.

About Respiratory Syncytial Virus

RSV is the most significant viral pathogen globally causing acute lower respiratory tract infections in children under 5 years old. It is also the primary cause of hospitalization for infant virus-related respiratory infections. In recent years, mounting research has demonstrated that RSV also plays a pivotal role in severe lung diseases in adults, primarily the elderly. It is estimated that in 2019, there were approximately 33 million cases of RSV-ALRTI (RSV viral infection with symptoms of acute lower respiratory tract infection) in children under 5 years old worldwide, which resulted in approximately 3.6 million hospitalizations and 100,000 deaths. Currently, there are no effective treatments specifically for RSV.

About Ziresovir

Ziresovir, formerly known as AK0529, was discovered following the optimization of hits obtained through screening a very large compound library against RSV replication in cell culture. Thereafter the drug completed rigorous preclinical and toxicological evaluation, including juvenile animal toxicology studies. Ziresovir is a structurally novel compound that binds to the viral 'F' or fusion protein of RSV, preventing entry of the virus into human cells and their infection, and thereby disease; this F-protein inhibition can also exert an anti-pathogenic action, preventing the cell-to-cell fusion (or "syncytium") that is a hallmark of RSV infection. Ziresovir’s mechanism of action is thus distinct from that of the common nucleoside class of antiviral drugs, which target and interfere with the production of nucleic acid within infected human cells.

About Ark Biosciences Inc.

Ark Biosciences is a privately held, clinical stage global biotechnology company with its corporate office located in Zhang Jiang Hi-Tech Park in Shanghai, its R&D Center in Suzhou BioBay, China, and offices in the United States, Australia and Switzerland. Ark Biosciences has its own active R&D programs and programs in collaboration with external partners.  Through these efforts, Ark Biosciences aims to be a global biotechnology company, discovering and developing innovative drugs for treatment of viral infections and respiratory diseases. For more information, please visit:

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