The primary object of this clinical study is to investigate the efficacy of HLCM051 in patients with ARDS caused by pneumonitis.

The objectives of this clinical study are as follows(ARDS caused by pneumonia cohort):

1. Primary objective To investigate the efficacy of HLCM051 in patients with ARDS caused by pneumonia
2. Secondary objective To confirm the safety of HLCM05 in patients with ARDS caused by pneumonia
3. Exploratory objective To investigate changes of biomarkers in patients with ARDS caused by pneumonia

The number of patients enrolled is 30 (20 patient in the HLCM051 group and 10 patients in the standard therapy group)

The objectives of this clinical study is as follows(ARDS caused by COVID-19 cohort):

1. Exploratory objective To investigate the safety and the efficacy of HLCM051 in patients with ARDS caused by SARS-Cov-2 infection

The number of patients enrolled is Approximately 5 (the HLCM051 group only)

Inclusion Criteria(ARDS caused by pneumonia cohort):

1. Provision of informed consent by the patient or his/her legal representative in case the patient is incapable of giving consent due to sedation etc
2. Male or female aged 20 to 90 years at informed consent (Asians only)
3. Patients with ARDS caused by pneumonia of those who were diagnosed as having ARDS according to the Berlin Definition
4. Patients who are confirmed to have the following findings in the Berlin Definition within the same 24 hours 1)PaO2/FiO2 (P/F) ratio ≤ 300 mmHg with positive end-expiratory pressure (PEEP) ≥ 5 cmH2O 2)Bilateral opacities on chest X-ray or CT (not fully explained by effusions, lobar/lung collapse, and nodular shadow) 3)Respiratory failure that cannot be explained by cardiac failure and fluid overload
5. Patients who underwent chest high-resolution computed tomography (HRCT)
6. Patients with HRCT score ≥211 according to the abbreviated HRCT scoring system
7. Patients with APACHE II score <27 at the diagnosis of ARDS
8. Patients who underwent artificial respiration with intubation
9. Patients who can start receiving the investigational product within 72 hours (3 days) after the diagnosis of ARDS
10. Patients whose condition is expected to be stable for at least 4 hours after initiating investigational product administration "Stable" means the condition where there is no need for significant sustained increase in FiO2 or PEEP and the supportive care for the cardiovascular system is not required (e.g. an increase in the dose of norepinephrine or epinephrine by ≥0.1 mcg/kg/min or an increase in the dose of inotropic agent or vasopressor by ≥20% besides norepinephrine and epinephrine for blood pressure control)
11. Women who are neither pregnant, breastfeeding, planning to become pregnant during the study period. Women of childbearing potential must agree on the use of appropriate contraceptive methods under the guidance of investigators through the completion of the clinical study
12. Male patients who have female partners of childbearing potential must agree on the use of appropriate contraceptive methods under the guidance of investigators through the completion of the clinical study

Exclusion Criteria(ARDS caused by pneumonia cohort):

1. Patients without life expectancy of 48 hours
2. Patients who are under artificial dialysis at screening
3. Patients whose life expectancy is <6 months because of complications at screening
4. Patients under ventilator at home due to chronic respiratory disease
5. Patients who have been on mechanical ventilation for ≥ 1 week
6. Patients with obvious honeycomb lung at screening consistent with pre-existing late-stage interstitial lung disease
7. Patients with clinically evident findings consistent with diffuse alveolar hemorrhage
8. Patients with chronic respiratory disease that requires continuous domiciliary oxygen therapy
9. Patients with severe COPD (stage III or severe according to the GOLD Classification)
10. Patients with chronic pulmonary hypertension (class III or IV according to the World Health Organization Classification of Functional Status of Patients With Pulmonary Hypertension)
11. Patients with a history of lung lobectomy, single-lung pneumonectomy or pulmonary transplantation
12. Patients who are appropriate to be treated with extracorporeal membrane oxygenation (ECMO) at screening
13. Patients who were resuscitated after cardio-respiratory arrest
14. Patients with a history of ST-segment elevation myocardial infarction within 6 months before informed consent
15. Patients with mean arterial (blood) pressure (MAP) <60 mmHg despite treatment with one or more vasopressor or cardiotonic agent
16. Patients with severe chronic liver disease (Child-Pugh >10)
17. Patients with a history of transplantation with autologous or allogeneic, bone marrow or peripheral stem cells for other purposes than the treatment of hematological tumor
18. Patients with malignancy requiring treatment at screening
19. Patients infected with human immunodeficiency virus (HIV)
20. Patients with a history of acute allergic reaction to the preparations derived from human tissues, bovine or swine materials, and those who refuse the use of biological products due to religious reasons
21. Patients for whom ARDS is not judged as the chief complaint by the investigator (sub-investigator) based on clinical findings
22. Patients who received other investigational drugs or products within 30 days prior to informed consent
23. Patients who are participating or planned to participate in other clinical studies (except for observational clinical researches that do not require intervention) during this clinical study
24. Patients who are inappropriate to participate in this clinical study because of significant complications (such as pneumothorax ) or psychiatric disorders as judged by the investigator
25. Patients who is suspected SARS-CoV-2 infection

Inclusion Criteria(ARDS caused by COVID-19 cohort ):

1. Provision of informed consent by the patient or his/her legal representative in case the patient is incapable of giving consent due to sedation etc.
2. Male or female aged 20 to 70 years at informed consent (Asians only)
3. Patients tested positive for COVID-19
4. Patients with ARDS caused by COVID-19 of those who were diagnosed as having ARDS according to the Berlin Definition
5. Patients who are confirmed to have the following findings in the Berlin Definition within the same 24 hours 1)PaO2/FiO2 (P/F) ratio ≤ 300 mmHg with positive end-expiratory pressure (PEEP) ≥ 5 cmH2O 2)Bilateral opacities on chest X-ray or CT (not fully explained by effusions, lobar/lung collapse, and nodular shadow) 3)Respiratory failure that cannot be explained by cardiac failure and fluid overload
6. Patients who underwent Chest X-ray, chest CT or high-resolution computed tomography (HRCT) as far as possible
7. Patients with APACHE II score <27 at the diagnosis of ARDS
8. Patients who underwent artificial respiration with intubation
9. Patients who can start receiving the investigational product within 72 hours (3 days) after the diagnosis of ARDS
10. Women who are neither pregnant, breastfeeding, planning to become pregnant during the study period. Women of childbearing potential must agree on the use of appropriate contraceptive methods under the guidance of investigators through the completion of the clinical study
11. Male patients who have female partners of childbearing potential must agree on the use of appropriate contraceptive methods under the guidance of investigators through the completion of the clinical study

Exclusion Criteria(ARDS caused by COVID-19 cohort ):

1. Patients without life expectancy of 48 hours
2. Patients who are under artificial dialysis at screening
3. Patients whose life expectancy is <6 months because of complications at screening
4. Patients under ventilator at home due to chronic respiratory disease
5. Patients who have been on mechanical ventilation for ≥ 1 week
6. Patients with obvious honeycomb lung at screening consistent with pre-existing late-stage interstitial lung disease
7. Patients with clinically evident findings consistent with diffuse alveolar hemorrhage
8. Patients with chronic respiratory disease that requires continuous domiciliary oxygen therapy
9. Patients with severe COPD (stage III or severe according to the GOLD Classification)
10. Patients with chronic pulmonary hypertension (class III or IV according to the World Health Organization Classification of Functional Status of Patients With Pulmonary Hypertension)
11. Patients with a history of lung lobectomy, single-lung pneumonectomy or pulmonary transplantation
12. Patients who are appropriate to be treated with extracorporeal membrane oxygenation (ECMO) at screening
13. Patients who were resuscitated after cardio-respiratory arrest
14. Patients with a history of ST-segment elevation myocardial infarction within 6 months before informed consent
15. Patients with mean arterial (blood) pressure (MAP) <60 mmHg despite treatment with one or more vasopressor or cardiotonic agent
16. Patients with severe chronic liver disease (Child-Pugh >10)
17. Patients with a history of transplantation with autologous or allogeneic, bone marrow or peripheral stem cells for other purposes than the treatment of hematological tumor
18. Patients with malignancy requiring treatment at screening
19. Patients infected with human immunodeficiency virus (HIV)
20. Patients with a history of acute allergic reaction to the preparations derived from human tissues, bovine or swine materials, and those who refuse the use of biological products due to religious reasons
21. Patients for whom ARDS is not judged as the chief complaint by the investigator (sub-investigator) based on clinical findings
22. Patients who have used other investigational drugs or products within 30 days before informed consent (excluding other investigational drugs or products used for the purpose of treating COVID-19)
23. Patients who are participating or planning to participate in other clinical studies during the study period (excluding other clinical studies, clinical researches and observational clinical researches that do not require intervention for the purpose of treating COVID-19)
24. Patients who are inappropriate to participate in this clinical study because of significant complications (such as pneumothorax ) or psychiatric disorders as judged by the investigator