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CompletedNCT03258502Updated Jul 31, 2025

A Study to Learn About the Effects of Multiple Doses of Sisunatovir on People With Respiratory Syncytial Virus (RSV) Infection

A Phase 2 interventional study of RV521 and Placebo in Respiratory Syncytial Virus Infections, sponsored by Pfizer. Completed at 1 site in United Kingdom. Open to participants aged 18 Years to 45 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2025-07-31.

Sponsored by Pfizer · Phase 2, Interventional, and Treatment

Phase
Phase 2
Study type
Interventional
Enrollment
66
Allocation
Randomized
Ages
18 Years to 45 Years
Sex
All
01

Study summary

The purpose of the study is to learn about the safety, pharmacokinetics and antiviral activity of the study medicine (called sisunatovir/RV521) for the potential treatment of respiratory syncytial virus (RSV). Sisunatovir will be given as multiple doses during the treatment period. RSV is a highly contagious virus that can lead to serious lung infections in patients with reduced ability to fight infection. Most vulnerable populations include babies, the elderly and patients that have received a bone marrow transplant.

This study is seeking healthy participants who are:

  1. Aged 18 to 45 years old and will agree to the use of highly effective methods of contraception.
  2. with a body mass index (BMI) of 18.0 to 30.0 Kg/m2 This study will consist of 2 cohorts of 33 participants each. In both cohorts participants will be exposed to the challenge virus on study day 0. Cohort 1 will receive either 200 mg of sisunatovir or placebo (looks the same as sisunatovir but contains no active medicine) 2 times a day for 5 days. Cohort 2 will receive either 350 mg of sisunatovir or placebo 2 times a day for 5 days. Participants will start taking the study medicine upon confirmation of RSV infection (or evening of Day 5 if not positive to RSV). The study medicine will be administered 12 hours apart (or twice daily). Each participant will remain in the quarantine unit until discharge on Day 12.
02

Conditions studied

  • Respiratory Syncytial Virus Infections
03

Who can participate

Ages eligible
18 Years to 45 Years
Sexes eligible
All
Accepts healthy volunteers
Yes

Inclusion criteria

  • Age 18 to 45 years, inclusive
  • In good health with no history of major medical conditions
  • A total body weight ≥ 50 kg and a body mass index (BMI) of >/=18kg/m2 and \</=30kg/m2

Exclusion criteria

Exclusion Criteria:

  • Evidence of any clinically significant or currently active major medical condition
  • Positive for Human Immunodeficiency Virus, active Hepatitis A, B or C test
  • Significant nose or nasopharynx abnormalities
  • Abnormal lung function
  • History or currently active symptoms suggestive of upper or lower respiratory tract infection
04

Study design

Phase
Phase 2
Primary purpose
Treatment
Allocation
Randomized
Intervention model
Parallel assignment
Masking
Double (Participant, Investigator)
Enrollment
66 participants (actual)

Study arms

  • Experimental
    RV521

    RV521 drug substance in capsule for oral administration

    Drug: RV521

  • Placebo comparator
    Placebo

    Micro-crystalline cellulose in capsule for oral administration

    Drug: Placebo

Interventions

  • DrugRV521

    RV521 drug in capsules

  • DrugPlacebo

    Placebo in capsules

05

What researchers measure

Primary outcomes

  1. Change in viral load

    Time frame: Baseline to study day 12

06

Study locations

1 site
  • hVIVO Services Ltd
    London, United Kingdom
07

References and documents

Publications

  • DeVincenzo J, Tait D, Efthimiou J, Mori J, Kim YI, Thomas E, Wilson L, Harland R, Mathews N, Cockerill S, Powell K, Littler E. A Randomized, Placebo-Controlled, Respiratory Syncytial Virus Human Challenge Study of the Antiviral Efficacy, Safety, and Pharmacokinetics of RV521, an Inhibitor of the RSV-F Protein. Antimicrob Agents Chemother. 2020 Jan 27;64(2):e01884-19. doi: 10.1128/AAC.01884-19. Print 2020 Jan 27. PubMed 31712214 ↗

Individual participant data

Plan to share: Yes — Pfizer will provide access to individual de-identified participant data and related study documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Study Report (CSR)) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions. Further details on Pfizer's data sharing criteria and process for requesting access can be found at: https://www.pfizer.com/science/clinical\_trials/trial\_data\_and\_results/data\_requests.

08

Registry details

Key details

Study ID
NCT03258502
Lead sponsor
Pfizer
Responsible party
Sponsor
First posted
Aug 23, 2017
Start date
Jul 19, 2017
Primary completion
Oct 31, 2017
Completion
Oct 31, 2017
Last update
Jul 31, 2025

Study contacts

Pfizer CT.gov Call Center
study director · Pfizer

Oversight

Data monitoring committee
No
FDA-regulated drug
No
FDA-regulated device
No
View the source record on ClinicalTrials.gov ↗

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This study is completed, as verified in Jul 2025. You cannot join it, but the record below documents what was studied.

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