Phase 2b study of S-337395 in symptomatic nonhospitalized adults with respiratory syncytial virus (RSV) who are at high risk of progression to severe disease

Overview

Sponsor-declared trial summary

Key facts

Sponsor

Shionogi B.V.

Participant type

Patients

Age range

18-64 years, 65+ years

Gender

Male and Female

Therapeutic area

Diseases [C] - Virus Diseases [C02]

Trial duration

17 Mar 2026 → ongoing

Decision date (initial)

2025-11-18

Transition trial

No

Low-intervention

No

Rare-disease indication

No

Vulnerable population

Yes

Funding sources

Shionogi B.V.; Herengracht 464, 1017 CA, Amsterdam, the Netherlands

External identifiers

EU CT number

2025-523156-31-00

ClinicalTrials.gov

NCT07214571

Trial design

CTIS Part I — objectives, methods, condition coding

Main objective

Scope: Therapy, Dose response, Efficacy, Safety

To investigate the antiviral effect of S-337395 in participants with RSV infection

Secondary objectives 4

1. To investigate the safety and tolerability following administration of S-337395 in participants with RSV infection
2. To investigate the effect of S-337395 on the clinical symptoms in participants with RSV infection
3. To investigate the antiviral effect of S‑337395 other than the primary endpoint in participants with RSV infection
4. To investigate the PK of S-337395 in participants with RSV infection

Conditions and MedDRA coding

Respiratory Syncytial Virus

Eligibility criteria

Principal inclusion / exclusion criteria as submitted by sponsor

Inclusion criteria 4

1. Age 1. Participant must be ≥ 18 years of age (or the minimum age of informed consent if the minimum age of informed consent determined by local regulations is >18 years) at the time of screening.
2. Type of Participant and Disease Characteristics 3. Participants diagnosed with RSV infection preferably using a rapid polymerase chain reaction (PCR) or other molecular-based diagnostic assay. Note: If a participant had a positive RSV test result using a molecular-based diagnostic assay from another study for which he/she was otherwise ineligible or from a standard-of-care molecular-based diagnostic test within 72 hours prior to start of screening and meets all eligibility criteria for inclusion in this study, this diagnostic test result can be used for determination of eligibility. 5. With the exception of the RSV disease, medically stable on the basis of medical history, physical examination, vital signs, and 12-lead ECG performed at screening. Any abnormalities must be consistent with the underlying illness in the study population and/or the RSV infection.
3. Sex and Contraceptive/Barrier Requirements The following criteria apply to male and female participants: 6. Contraceptive use by men or women should be consistent with local regulations regarding the use of contraceptive methods for those participating in clinical studies. Men must refrain from semen donation a. Male participants: Male participants are eligible to participate if they agree to the following during the intervention period and for at least 10 days after the last dose of investigational intervention: ● Refrain from donating fresh unwashed semen PLUS either: ● Be abstinent from heterosexual intercourse as their preferred and usual lifestyle (abstinent on a long-term and persistent basis) and agree to remain abstinent OR ● Must agree to use contraception/barrier as detailed below – Agree to use a male condom when having sexual intercourse with a woman of childbearing potential who is not currently pregnant – Agree to use a male condom when engaging in any activity allowing for passage of ejaculate to another person
4. Informed Consent 7. Capable of giving signed informed consent as described in Appendix 1 (Section 10.1.3), which includes compliance with the requirements and restrictions listed in the informed consent form (ICF) and in this protocol. Each participant has signed an ICF indicating he/she: a. Understands the purpose of, and procedures required for, the study b. Is willing and able to adhere to the prohibitions and restrictions with respect to the concomitant medication c. Is willing and able to adhere to the study procedures and assessments to be performed

Exclusion criteria 20

1. 1. Hospitalized or expected to be hospitalized within 24 hours of screening. Any stay in the emergency room or in the observational unit of at least 24 hours will be considered hospitalization for the purposes of the study.
2. 2. Is considered by the investigator to be immunocompromised, due to an underlying medical condition (eg, HIV infection, malignancy, or genetic disorder other than immunoglobulin A deficiency) or medical therapy (eg, immunomodulators other than corticosteroids for the treatment of COPD or asthma exacerbations), chemotherapy, radiation, stem cell or solid organ transplant
3. 3. Major surgery within 28 days prior to enrolment in the study or planned major surgery during the study
4. 4. Has a neuromuscular disease affecting swallowing or the thoracic muscles
5. 5. Has a known or clinically suspected acute or chronically active hepatitis B or C infection
6. 6. Has known allergies, hypersensitivity, or intolerance to S-337395 or to any of the excipients of the S-337395 or placebo formulation
7. 7. Suspicion or known severe renal impairment (defined as estimated glomerular filtration rate < 30 mL/min/1.73 m2) or ongoing dialysis
8. 8. Aspartate aminotransferase or alanine aminotransferase > 3 times the upper limit of normal (ULN) or total bilirubin ≥ 2 × ULN (except for Gilbert syndrome) within the past 3 months, active liver disease (except direct bilirubin > ULN), or the presence of liver dysfunction grade B or C according to the Child-Pugh classification
9. 9. Any other medical or psychiatric condition making the participant unsuitable for the current study or interfering with the evaluation of response to the study intervention in the opinion of the investigator/subinvestigator
10. Prior/Concomitant Therapy 13. Has received a therapy intended to treat RSV infection (eg, ribavirin, traditional Chinese medicines, or complementary therapies) within 14 days prior to screening
11. 14. Is receiving chemotherapy or immunotherapy for malignancy
12. 15. Has received RSV vaccination within 7 days prior to screening Note: RSV vaccination is not prohibited, unless administered within 7 days prior to screening.
13. Prior/Concurrent Clinical Study Experience 16. The participant is currently participating or planned to participate in another clinical interventional study, during their participation in this study.
14. Diagnostic Assessments 17. Has had either confirmed SARS-CoV-2 or influenza infection (test was positive) during the 28 days prior to screening,
15. 18. Has any other confirmed clinically relevant respiratory infection by any pathogen at, or within 28 days of screening
16. Other Exclusion Criteria 19. Women who are of childbearing potential
17. 20. Men who plan to father a child while enrolled in this study or within 10 days after the last dose of study intervention
18. 21. Participants unable to take medications orally or with a known gastrointestinal-related condition considered by the sponsor or investigator to be likely to interfere with study intervention ingestion or absorption
19. 22. Participants unwilling to undergo nasal nasopharyngeal swab procedures or with any physical abnormality which limits the ability to collect regular nasal specimens
20. 23. At the US sites, site staff and their families who are directly involved in the conduct of the study, site staff who are otherwise under the supervision of the investigator, and sponsor and sponsor representative employees and their families who are directly involved in the conduct of this study. For sites in all other countries, apply local country regulations.

Endpoints

Primary and secondary outcome measures (English text)

Primary endpoints 1

1. Change from baseline in RSV RNA load by qRT-PCR (nasopharyngeal swab) on visit 2 (day 2), visit 3 (day 4), and visit 4 (day 6)

Secondary endpoints 4

1. Assessment of TEAEs, clinical laboratory test results, 12-lead ECGs, physical examination findings, and vital signs measurements
2. Change from baseline over time in severity of RSV symptoms using RiiQ™: respiratory (RiiQ-RSS), systemic (RiiQ-SSS), and total (RiiQ-RSS + RiiQ-SSS). Time to resolution defined as return to baseline per PSQ. Includes time to first and sustained (2 days) resolution of respiratory, systemic, and combined symptoms, and resolution of each symptom separately, based on RiiQ subscales.
3. Based on RSV virological assay (nasopharyngeal swabs): Change from baseline in RSV RNA load and infectious titer at each time point; AUC through day 6; time to first/sustained negative or
4. > Plasma concentrations of S-337395 after repeated oral doses of S-337395 > Plasma concentrations of S 337395 12 and 24 hours after the first dose and the last dose (C12 and C24)

Investigational products

Investigational medicinal products (IMPs), comparators, placebo, auxiliary

Test 1

Placebo 1

Sponsors and contacts

Sponsor organisations, regulatory contacts, third parties

Shionogi B.V.

Sponsor organisation

Shionogi B.V.

Address

Herengracht 464

City

Amsterdam

Postcode

1017 CA

Country

Netherlands

Scientific contact point

Organisation

Shionogi B.V.

Contact name

Shionogi B.V. Medical Sciences

Public contact point

Organisation

Shionogi B.V.

Contact name

Shionogi B.V. Medical Sciences

Third parties 9

Locations

2 EU/EEA countries · 8 investigational sites

By country

Investigational sites

Country notifications

Trial-start, recruitment-start, end and early-termination notifications submitted per Member State

Results and documents

Annex IV summary of results, Annex V layperson summary, and all documents registered in CTIS for this trial

Documents 21 files

Public protocol annexes, IB summaries, regulatory submissions and post-authorisation documents registered in CTIS.

Application history

4 submissions — initial application plus substantial / non-substantial modifications