Efficacy and Safety of 3 Doses of HL10 Given at Fixed Time Intervals Compared to Standard Therapy

Inclusion Criteria: * Patients intubated and on mechanical ventilation * Patients with Acute Lung Injury defined as (a, b, c and d are all applicable): a: PaO2/FiO2 \< or equal to 300 mmHg (40.0 kPa) (regardless of PEEP level), b: Acute onset, c: Pulmonary artery wedge pressure \< or equal to 18 mmHg when measured or no clinical evidence of left atrial hypertension, d: Bilateral infiltrates seen on frontal chest radiograph * Less than 60 hours from onset of the present period of mechanical ventilation to 1st instillation * Expected to continue on mechanical ventilation for more than 24 hours * 18 years of age or older * Following receipt of verbal and written information about the trial, the patient or legally acceptable representative must provide signed and dated informed consent before any trial related activity is carried out Exclusion Criteria: * Current diagnosis of acute bronchial asthma attack * History of or clinical suspicion of lung fibrosis * Current diagnosis of suspected pulmonary thrombo-embolism * Patients on daily medication for chronic obstructive pulmonary disease at time of admission to ICU * Patients who have received mechanical ventilation for more than 48 hours continuously within 1 month prior to the present period of mechanical ventilation * Patients with pneumonectomy or lobectomy * Patients with untreated pneumothorax at time of instillation * Patients having tracheostomy at time of instillation * Patients who have had surgical procedures under general anaesthesia performed within 6 hours prior to inclusion blood gas sample * Patients having mean arterial blood pressure \< 50 mmHg in spite of adequate fluid administration and/or vasoactive drugs at time of instillation * Patients having PaO2 \< 75 mmHg with a FiO2 = 1.0 not responding to adjustment of PEEP at time of instillation * Glasgow Coma Score \< or equal to 10 before sedation or major findings on CT/MR scan of the head such as: brain oedema, acute space occupying lesion, other acute lesions with bleeding or mass effect (patients with minor lesion which do not require further diagnostics or monitoring can be included) * Patients with life expectancy less than 3 months due to primary disease assessed by the attending physician (e.g., end-stage cancer, AIDS or generally poor health) * Known or suspected hypersensitivity to constituents(s) of the investigational product * Patients who have received treatment with any investigational drug within the previous 4 weeks * Current participation in any other interventional clinical trial until day 29 of the trial * Patients previously randomised in this trial * Patients known or suspected of not being able to comply with a study protocol (e.g., due to alcoholism, drug dependency or psychotic state) * Females of childbearing potential who have a positive pregnancy test or who are breast feeding * Patients suffering from highly infectious diseases where trial related procedures could pose a safety risk for the staff (e.g., SARS)