New RSV drug tested in kids – but trial halted early

NCT ID NCT06102174

Terminated Disease control Sponsor: Pfizer Source: ClinicalTrials.gov ↗

First seen Jun 27, 2026 · Last updated Jun 27, 2026

Summary

This study tested the safety and dosing of sisunatovir, an experimental antiviral drug, in infants and children up to 5 years old with RSV lower respiratory tract infection. Ten participants received either the drug or a placebo. The goal was to find the right dose for future studies. However, the trial was terminated early, so the full results may not be available.

What this could mean

Our plain-language read of the trial. This is informational only — not medical advice or a prediction.

Active substance: Sisunatovir (also known as PF-07923568, RV521)
What this could lead to: If successful, this study could help determine the right dose of sisunatovir for future trials in children with RSV, potentially leading to a treatment for severe RSV infections.
What could go wrong: This is a very early (phase 1b) and small study (only 10 participants) focused on safety and dosing, not on proving the drug works. The trial was terminated, so results may be limited.

This is an AI summary of the original study and may miss details. Read our disclaimer.

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Conditions

The condition(s) this trial relates to.

respiratory syncytial virus infectious disease

As listed by the trial registrant

The condition terms exactly as the trial's registrant entered them.

RESPIRATORY SYNCYTIAL VIRUS INFECTIONS

Contacts and locations

Locations

Kaiser Permanente

Los Angeles, California, 90027, United States
Kaiser Permanente Los Angeles Medical center

Los Angeles, California, 90027, United States
Kojunkai Daido Hospital

Nagoya, Aichi-ken, 457-8511, Japan
Monti Clinical Research Centre

Mdantsane, Eastern Cape, 5219, South Africa
Nintenkai Kagoshima Children's Hospital

Hioki, Kagoshima-ken, 899-2503, Japan
Osaka City General Hospital

Osaka, 534-0021, Japan
University of Witwatersrand (WITS) - Vaccines and Infectious Diseases Analytics (VIDA)

Johannesburg, Gauteng, 2013, South Africa
Washington University School of Medicine

St Louis, Missouri, 63110, United States
Yamanashi Prefectural Central Hospital

Kofu, Yamanashi, 400-8506, Japan

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