The goal of this clinical trial is to learn if YD0743 works to treat sepsis-associated acute respiratory distress syndrome (ARDS) in adult patients admitted to the Intensive Care Unit. It will also learn about the safety of drug YD0743. The main questions it aims to answer are:

Does YD0743 injection shorten the ventilator-using days in sepsis-associated ARDS patients? What medical problems do participants have when accepting YD0743 treatment?

Researchers will compare YD0743 to a placebo (a look-alike substance that contains no active drug) to see if YD0743 works to treat sepsis-associated ARDS.

Participants will:

Accepting YD0743 injection at least for 7 days. Visit the clinic in person at the Day 28 to receive the follow-up check (D1 is defined as the first day starting the YD0743 or placebo treatment) .

Inclusion Criteria:

• Male or female, aged between 18 and 75 years (inclusive).
• Diagnosis of sepsis.
• Diagnosis of Acute Respiratory Distress Syndrome (ARDS) suspected or confirmed to be caused by sepsis.
• Time from ARDS diagnosis to signing the informed consent form (ICF) does not exceed 48 hours.
• The subject (or their legally authorized representative) has fully understood the study's purpose, nature, procedures, and potential adverse events, voluntarily agrees to participate, and provides written informed consent.

Exclusion Criteria:

• Known allergy or hypersensitivity to the active ingredient or any excipients of the investigational product; or a history of allergic disorders.
• Expected survival time is less than 48 hours at the time of screening.
• Sepsis with extensive burns as the primary cause.
• Currently diagnosed with active malignancy; or malignancy with distant metastasis; or cancer patients with cachexia; or patients with severe organ dysfunction or visceral hemorrhage due to tumor obstruction, space-occupying effect, or compression, for whom surgical intervention is difficult or has not yet been performed.
• Currently receiving or requiring Extracorporeal Membrane Oxygenation (ECMO) therapy.
• Presence of chronic severe organ failure or immunodeficiency/immunosuppression.
• Thrombocytopenia at screening, active/uncontrolled bleeding, or patients whom the investigator considers to have a current or prior high risk of bleeding.
• Diagnosis of neutropenia.
• Positive for Hepatitis B surface antigen (HBsAg) with HBV-DNA > 1000 copies/mL or 200 IU/mL; positive for Hepatitis C virus antibody (HCV-Ab); positive for Human Immunodeficiency Virus antibody (HIV-Ab); or positive for Treponema pallidum antibody.
• Participation in other drug or medical device clinical trials within 3 months prior to this study, or current participation in another clinical trial.
• Pregnant or breastfeeding women, or women planning to become pregnant within the next 6 months.
• Patients whose underlying primary disease cannot be effectively treated.
• Any other condition that, in the opinion of the investigator, makes the subject unsuitable for participation in this study.