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NCT Number: NCT07658534

A Study of Ziresovir (AK0529) in High-risk Adult With Respiratory Syncytial Virus (RSV) Infection.

Respiratory syncytial virus (RSV) is recognized worldwide as a significant pathogen causing lower respiratory tract infection in infants, the elderly, and immunocompromised patients, which may cause bronchiolitis or pneumonia, and affect the cardiovascular system, central nervous system and the renal system, resulting in hospitalization and death risks in children and also high-risk adults, particularly the elderly. The purpose of this study is to evaluate the efficacy of Ziresovir (AK0529) compared to placebo with respect to the time to resolution of RSV lower respiratory tract disease (LRTD) symptoms.

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Key information

Conditions

Respiratory Syncytial Virus Infections Cardiovascular Diseases Heart Diseases Infections Mononegavirales Infections Paramyxoviridae Infections Pneumovirus Infections RNA Virus Infections Virus Diseases

Age range

18 year–85 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Phase 2 / Phase 3

Primary location

China-Japan Friendship Hospital, Beijing, Beijing Municipality, China

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Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Aged 18-85 years (inclusive), regardless of gender.
  • Diagnosed with RSV infection by antigen or nucleic acid test within 36 hours before first dose.
  • Have at least one of the following high-risk conditions for RSV infection: Chronic respiratory disease; heart disease; immunocompromised status; other chronic disease; age ≥65 years.
  • Presence of at least one new LRTD symptom or worsening of a pre-existing LRTD symptom (specifically: cough, expectoration, wheezing, shortness of breath), with at least one individual symptom rated as moderate or severe (score 2 or 3 per RiiQ Symptom Scale).
  • Time from symptom onset (or worsening of pre-existing symptoms) to first dose ≤5 days. (Onset defined as time of first RSV-related symptom/sign confirmed by investigator; pre-existing symptoms are those due to underlying conditions)

Exclusion criteria

  • Diagnosed with influenza or COVID-19 infection within 7 days prior to providing informed consent.
  • Suspected bacterial co-infection.
  • Received any potentially anti-RSV agents (e.g., ribavirin, long-acting interferon) within 5 half-lives prior to the first study dose, or plans to use such agents during the study.
  • Received prohibited medications, or plans to use prohibited medications during the study.
  • Has a severe or unstable gastrointestinal, hepatic, renal, hematologic disorder, or malignancy.
  • Has a known allergy, hypersensitivity, or intolerance to AK0529 or to any excipients in the AK0529 or placebo formulation.
  • Female participants with a positive pregnancy test result, or who are breastfeeding.
  • Refusal to use effective contraception during the trial period.

Treatment and study plan

Ziresovir (AK0529)

Drug

Active Substance: AK0529 Pharmaceutical Form: Enteric Capsules Route of Administration: Oral

Placebo

Drug

Active Substance: Placebo Pharmaceutical Form: Enteric Capsules Route of Administration: Oral

Primary outcomes

  1. Time from first dose to resolution of LRTD symptoms

    Time frame: Up to Day 27

    LRTD symptoms (cough, shortness of breath, wheezing, expectoration) are assessed by the RiiQ symptom scale, which includes 13 symptoms: 2 upper respiratory (stuffy nose, sore throat), 4 lower respiratory (cough, expectoration, wheezing, shortness of breath), and 7 systemic (feeling feverish, headache, body aches/pains, neck pain, trouble sleeping, tiredness, poor appetite). Each symptom is scored as None (0), Mild (1), Moderate (2), or Severe (3), with a total score range of 0-39.

Secondary outcomes

  1. Resolution rates of LRTD symptoms after treatment

    Time frame: Day 3, Day 6, Day 13, Day 27

    LRTD symptoms (cough, shortness of breath, wheezing, expectoration) are assessed by the RiiQ symptom scale, which includes 13 symptoms: 2 upper respiratory (stuffy nose, sore throat), 4 lower respiratory (cough, expectoration, wheezing, shortness of breath), and 7 systemic (feeling feverish, headache, body aches/pains, neck pain, trouble sleeping, tiredness, poor appetite). Each symptom is scored as None (0), Mild (1), Moderate (2), or Severe (3), with a total score range of 0-39.

  2. Time from first dose to resolution of upper respiratory, systemic, and total symptoms

    Time frame: Up to Day 27

    Upper respiratory, systemic, and total symptoms are assessed by the RiiQ symptom scale, which includes 13 symptoms: 2 upper respiratory (stuffy nose, sore throat), 4 lower respiratory (cough, expectoration, wheezing, shortness of breath), and 7 systemic (feeling feverish, headache, body aches/pains, neck pain, trouble sleeping, tiredness, poor appetite). Each symptom is scored as None (0), Mild (1), Moderate (2), or Severe (3), with a total score range of 0-39.

  3. Resolution rate of upper respiratory, systemic, and total symptoms

    Time frame: Day 3, Day 6, Day 13, Day 27

    Upper respiratory, systemic, and total symptoms are assessed by the RiiQ symptom scale, which includes 13 symptoms: 2 upper respiratory (stuffy nose, sore throat), 4 lower respiratory (cough, expectoration, wheezing, shortness of breath), and 7 systemic (feeling feverish, headache, body aches/pains, neck pain, trouble sleeping, tiredness, poor appetite). Each symptom is scored as None (0), Mild (1), Moderate (2), or Severe (3), with a total score range of 0-39.

  4. Change from baseline in RSV viral load (VL)

    Time frame: Day 2 to Day6, Day 13, Day 27

    RSV VL in nasopharyngeal samples from participants will be measured by quantitative reverse transcription polymerase chain reaction (qRT-PCR)

  5. Change from baseline in RiiQ total score and domain scores

    Time frame: Day 3, Day 6, Day 13, Day 27

    RSV symptoms are assessed by the RiiQ symptom scale, which includes 13 symptoms: 2 upper respiratory (stuffy nose, sore throat), 4 lower respiratory (cough, expectoration, wheezing, shortness of breath), and 7 systemic (feeling feverish, headache, body aches/pains, neck pain, trouble sleeping, tiredness, poor appetite). Each symptom is scored as None (0), Mild (1), Moderate (2), or Severe (3), with a total score range of 0-39.

  6. Trough plasma concentration of AK0529

    Time frame: Day 5

    Plasma concentration of AK0529 is reported. This outcome measure is planned to be analyzed for specified arm only. In this outcome measure, only those time points for which individual participants had data are reported.

  7. Incidence and severity of treatment-emergent AEs (TEAEs), SAEs, and other AEs

    Time frame: Up to Day 27

    An adverse events (AEs) is any untoward medical occurrence in a clinical study participant administered a pharmaceutical (investigational or non-investigational) product. An AE does not necessarily have a causal relationship with the intervention. Any clinically significant physical examinations, vital signs, clinical laboratory tests (including biochemistry, hematology, cardiac enzymes and urine analysis), 12-lead electrocardiograms (ECGs) and spirometry results were recorded as adverse events. Any AE which occurred at or after the initial administration of study intervention through the end of the study (that is, Day 27) was considered treatment-emergent. A Serious Adverse Events (SAEs) is any adverse event that results in death, is life-threatening, requires hospitalization, causes persistent disability, or results in a congenital anomaly. The severity of AEs/ SAEs is categorized by CTCAE6.0.

Other outcomes

  1. Proportion of participants hospitalized

    Time frame: Up to Day 27

    Proportion of outpatient participants who experienced at least one hospitalization during the study period.

  2. Hospitalization duration

    Time frame: Up to Day 27

    Duration of hospitalization among participants who were hospitalized during the study period.

  3. Supplemental oxygen use

    Time frame: Up to Day 27

    The proportion of participants who received supplemental oxygen at any point during the study, as well as the duration of use.

  4. ICU admission rate

    Time frame: Up to Day 27

    The proportion of participants with at least one ICU admission during the study.

Study contacts

Contact information is provided by the study sponsor or research team.

Chao Yu, Mater

CONTACT

[email protected]

+86 021-50681677

Sponsors and collaborators

Lead sponsor

Shanghai Ark Biopharmaceutical Co., Ltd.

Industry

Registry information

Official study title

A Randomized, Double-blind, Two-stage, Placebo-controlled Phase 2b/3 Clinical Study to Evaluate the Efficacy and Safety of Ziresovir (AK0529) in Adult Patients at High Risk for Respiratory Syncytial Virus (RSV) Infection.

Important dates

Study start
2026
Primary completion
2028
Study completion
2029
First posted
Jun 22, 2026
Registry last updated
Jun 22, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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