* endotracheal intubation and mechanical ventilation. * noninvasive positive pressure ventilation without endotracheal intubation. * requires chronic oxygen therapy. * treatment with conventional synthetic disease-modifying antirheumatic drugs (dmards)/immunosuppressive agents for ≥ 4 weeks duration within 3 months prior to the screening visit. * use of oral corticosteroids in a dose higher than prednisone 15 mg or equivalent per day for ≥ 4 weeks duration within 3 months prior to the screening visit. * systemic autoimmune disease. * participation in any clinical research study evaluating an investigational product or therapy within 3 months prior to the screening visit, * presence of any of the following abnormal laboratory values at screening: absolute neutrophil count \< 2,000/mm3, aspartate aminotransferase or alanine aminotransferase \> 5 × upper limit of normal (uln), platelets \< 50,000/mm3. * d-dimer \> 2 × uln at screening, as evidence of potential disseminated intravascular coagulation (dic). * has confounding medical conditions, including poorly controlled diabetes, uncontrolled new york heart association class iii congestive heart failure, clinically significant arrhythmias not controlled by medication, idiopathic pulmonary fibrosis, interstitial lung disease, or chronic obstructive pulmonary disease. * has bacterial sepsis currently or suspicion thereof. * has cancer currently and is receiving active treatment (including radiation therapy or chemotherapy) or malignancy within the last 5 years, with the exception of curable cancer (eg, basal or squamous cell skin cancer, cervical cancer in situ, nonmedullary thyroid carcinoma) that has been adequately treated (eg, excision). * prior history of myocardial infarction or angina, stroke or transient ischemic attack (tia), pulmonary embolism or deep vein thrombosis. * is moribund and not expected to survive 48 hours following screening or for whom no further aggressive treatment such as mechanical ventilation is planned.

* endotracheal intubation and mechanical ventilation. * noninvasive positive pressure ventilation without endotracheal intubation. * requires chronic oxygen therapy. * treatment with conventional synthetic disease-modifying antirheumatic drugs (dmards)/immunosuppressive agents for ≥ 4 weeks duration within 3 months prior to the screening visit. * use of oral corticosteroids in a dose higher than prednisone 15 mg or equivalent per day for ≥ 4 weeks duration within 3 months prior to the screening visit. * systemic autoimmune disease. * participation in any clinical research study evaluating an investigational product or therapy within 3 months prior to the screening visit, * presence of any of the following abnormal laboratory values at screening: absolute neutrophil count \< 2,000/mm3, aspartate aminotransferase or alanine aminotransferase \> 5 × upper limit of normal (uln), platelets \< 50,000/mm3. * d-dimer \> 2 × uln at screening, as evidence of potential disseminated intravascular coagulation (dic). * has confounding medical conditions, including poorly controlled diabetes, uncontrolled new york heart association class iii congestive heart failure, clinically significant arrhythmias not controlled by medication, idiopathic pulmonary fibrosis, interstitial lung disease, or chronic obstructive pulmonary disease. * has bacterial sepsis currently or suspicion thereof. * has cancer currently and is receiving active treatment (including radiation therapy or chemotherapy) or malignancy within the last 5 years, with the exception of curable cancer (eg, basal or squamous cell skin cancer, cervical cancer in situ, nonmedullary thyroid carcinoma) that has been adequately treated (eg, excision). * prior history of myocardial infarction or angina, stroke or transient ischemic attack (tia), pulmonary embolism or deep vein thrombosis. * is moribund and not expected to survive 48 hours following screening or for whom no further aggressive treatment such as mechanical ventilation is planned.

- endotracheal intubation and mechanical ventilation. - noninvasive positive pressure ventilation without endotracheal intubation. - requires chronic oxygen therapy. - treatment with conventional synthetic disease-modifying antirheumatic drugs (dmards)/immunosuppressive agents for ≥ 4 weeks duration within 3 months prior to the screening visit. - use of oral corticosteroids in a dose higher than prednisone 15 mg or equivalent per day for ≥ 4 weeks duration within 3 months prior to the screening visit. - systemic autoimmune disease. - participation in any clinical research study evaluating an investigational product or therapy within 3 months prior to the screening visit, - presence of any of the following abnormal laboratory values at screening: absolute neutrophil count < 2,000/mm3, aspartate aminotransferase or alanine aminotransferase > 5 × upper limit of normal (uln), platelets < 50,000/mm3. - d-dimer > 2 × uln at screening, as evidence of potential disseminated intravascular coagulation (dic). - has confounding medical conditions, including poorly controlled diabetes, uncontrolled new york heart association class iii congestive heart failure, clinically significant arrhythmias not controlled by medication, idiopathic pulmonary fibrosis, interstitial lung disease, or chronic obstructive pulmonary disease. - has bacterial sepsis currently or suspicion thereof. - has cancer currently and is receiving active treatment (including radiation therapy or chemotherapy) or malignancy within the last 5 years, with the exception of curable cancer (eg, basal or squamous cell skin cancer, cervical cancer in situ, nonmedullary thyroid carcinoma) that has been adequately treated (eg, excision). - prior history of myocardial infarction or angina, stroke or transient ischemic attack (tia), pulmonary embolism or deep vein thrombosis. - is moribund and not expected to survive 48 hours following screening or for whom no further aggressive treatment such as mechanical ventilation is planned.

- endotracheal intubation and mechanical ventilation. - noninvasive positive pressure ventilation without endotracheal intubation. - requires chronic oxygen therapy. - treatment with conventional synthetic disease-modifying antirheumatic drugs (dmards)/immunosuppressive agents for ≥ 4 weeks duration within 3 months prior to the screening visit. - use of oral corticosteroids in a dose higher than prednisone 15 mg or equivalent per day for ≥ 4 weeks duration within 3 months prior to the screening visit. - systemic autoimmune disease. - participation in any clinical research study evaluating an investigational product or therapy within 3 months prior to the screening visit, - presence of any of the following abnormal laboratory values at screening: absolute neutrophil count < 2,000/mm3, aspartate aminotransferase or alanine aminotransferase > 5 × upper limit of normal (uln), platelets < 50,000/mm3. - d-dimer > 2 × uln at screening, as evidence of potential disseminated intravascular coagulation (dic). - has confounding medical conditions, including poorly controlled diabetes, uncontrolled new york heart association class iii congestive heart failure, clinically significant arrhythmias not controlled by medication, idiopathic pulmonary fibrosis, interstitial lung disease, or chronic obstructive pulmonary disease. - has bacterial sepsis currently or suspicion thereof. - has cancer currently and is receiving active treatment (including radiation therapy or chemotherapy) or malignancy within the last 5 years, with the exception of curable cancer (eg, basal or squamous cell skin cancer, cervical cancer in situ, nonmedullary thyroid carcinoma) that has been adequately treated (eg, excision). - prior history of myocardial infarction or angina, stroke or transient ischemic attack (tia), pulmonary embolism or deep vein thrombosis. - is moribund and not expected to survive 48 hours following screening or for whom no further aggressive treatment such as mechanical ventilation is planned.