Study in Intensive Care Patients to Investigate the Clinical Effect of Repetitive Orally Inhaled Doses of AP301 on Alveolar Liquid Clearance in Acute Lung Injury

Inclusion Criteria: * age ≥ 18 * intubated and mechanically ventilated male and female patients of the Intensive Care Units of the Department of Anesthesia, General Intensive Care and Pain Control * meets the criteria of ALI (as defined by the American-European Consensus Conference on ALI/ ARDS): * Onset of ALI within 48 hours * Bilateral infiltrates seen on frontal chest radiograph * PCWP ≤ 18 mm Hg or no clinical evidence of left atrial hypertension * paO2/ FiO2 ratio ≤ 300 mm Hg * EVLW in PiCCO® at screening ≥ 8 ml/PBW * Meeting criteria for extensive hemodynamic monitoring according to investigators discretion * ICU Patients being mechanically ventilated and are stable in this condition for at least 8 hours * Negative pregnancy test and adequate contraception in female patients of childbearing potential * Informed consent: * For patients that are temporarily unable to consent (e.g. comatose patients) a subsequent informed consent has to be provided. Exclusion Criteria: * History of clinically relevant allergies or idiosyncrasies to AP301 or any other inactive ingredient(s) of the investigational product * Brainstem death at screening * Current evidence of septic shock as defined by the Surviving Sepsis Campaign (Presence of acute organ dysfunction secondary to infection plus hypotension with systolic blood pressure \< 90 mm Hg or mean arterial pressure (MAP) \< 70 mm Hg for not less than one hour which cannot be reversed with fluid resuscitation) * Neutrophil count \<0.3 x 109 L * Patients under immunosuppression: high dose steroids (\> 80 mg Prednisolone /d; \> 300 mg hydrocortisone / d), cancer treatment (chemotherapy or biological) or therapy with other immunosuppressive agents for organ transplantation within 2 weeks * BMI \< 18.5 or \> 35 * Cardiogenic pulmonary edema diagnosed by echocardiography or pulmonary artery catheter * Pregnancy / lactation or intention to fall pregnant during the time course of the study * Women of childbearing potential as well as men of procreative capacity who are not using adequate contraception * Participation in other interventional drug trials