This study is a randomized, blank-controlled, open-label, single-dose, dose-escalation clinical study of rhKGF-2 in patients with ARDS.

The trial is designed with three dose groups (5 mg, 10 mg, and 15 mg), which will be escalated sequentially from the lowest dose group to the highest dose group. Each dose group will enroll 8 subjects, randomized in a 6:2 ratio according to the order of enrollment, to receive either the corresponding dose of rhKGF-2 (6 subjects) or serve as a blank control (2 subjects). Each subject will receive a single dose, administered once via a disposable bronchoscopic catheter.

All subjects will receive the trial intervention on top of standard ARDS treatment (see Concomitant Medications for details). Following the completion of drug administration, subjects will enter a 28-day follow-up period. Outcome measures include adverse events (AE), vital signs, laboratory parameters, oxygenation index (PFR), chest imaging changes, etc., to evaluate the safety, tolerability, and efficacy of the treatment.

Inclusion Criteria:

1. Aged ≥18 years and <80 years, male or female.

2. Definite diagnosis of acute respiratory distress syndrome (ARDS) according to the Berlin Definition.

3. Patients with PaO₂/FiO₂ < 200 mmHg and receiving invasive mechanical ventilation via endotracheal intubation.

4. Diagnosis of ARDS confirmed no more than 72 hours prior to enrollment.

5. No plan for parenthood within 1 year and agree to take effective contraceptive measures during the study period. Female participants of childbearing potential must have a negative serum pregnancy test.

6. The subject fully understands the purpose of the study, as well as the nature, methods, and potential reactions of the investigational drug. The subject voluntarily signs the informed consent form to participate in the study and agrees to comply with the requirements of the study protocol. If the subject is unable to provide consent or has limited capacity to consent, consent must be obtained from the subject's legal guardian.

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Exclusion Criteria:

1. Use of inhaled pulmonary vasodilators (e.g., nitric oxide or prostaglandins).
2. Current receipt or planned receipt of extracorporeal membrane oxygenation (ECMO) during the study period.
3. Expected survival < 3 months due to causes other than respiratory failure.
4. Cerebrovascular or cardiovascular events within 3 months prior to study drug administration, including unstable angina, congestive heart failure, myocardial infarction within the past 12 months, hemodynamic instability, known left ventricular ejection fraction (LVEF) < 40%, or clinically significant arrhythmia or conduction abnormality.
5. Inability to tolerate single-use bronchoscopic imaging catheter examination, including but not limited to the following: active massive hemoptysis; severe hypertension and arrhythmia; myocardial infarction or unstable angina within 4-6 weeks prior to screening; severe cardiac dysfunction; uncorrectable bleeding tendency (platelet count < 60 × 10⁹/L), such as severe coagulation disorders, uremia, or severe pulmonary hypertension; severe superior vena cava syndrome; suspected aortic aneurysm; multiple pulmonary bullae.
6. History of severe allergic reaction, or known allergy or hypersensitivity to any component of the investigational product.
7. Breastfeeding or pregnant women.
8. Participation in any drug clinical trial within 3 months prior to enrollment.
9. Any other condition that, in the opinion of the investigator, makes the subject unsuitable for participation in this study.

All IPD that underlie results in a publication.

Sharing will begin within 6 months after article publication.

IPD and supporting information will be avaible to researchers upon reasonable request (e.g. with a practical and meaningful research proposal).