1. patients with moderate or severe acute respiratory failure or requiring noninvasive ventilation or oxygen or with spo2 \< 92% or tachypnea (respiratory rate ≥ 30 breaths/min). 2. patients treated with immunosuppressors and/or immunomodulators. 3. engrafted patients (organ and/or hematopoietic stem cells). 4. patients with uncontrolled auto-immune disease. 5. patients with known or suspected active (i.e. not controlled) bacterial, viral (excluding covid-19) or fungal infections. 6. patients with preexisting, severe and not controlled organ failure. 7. history or active malignancy requiring chemotherapy or radiation therapy (excluding 2 years disease free survivor patients). 8. pregnant or breast-feeding women. 9. illicit drug or alcohol abuse or dependence that may compromise the patient's safety or adherence to the study protocol. 10. use of any investigational or non-registered product within 3 months or within 5 half-lives preceding baseline, whichever is longer. 11. hypersensitivity to abx464 and/or its excipients. 12. any condition, which in the opinion of the investigator, could compromise the patient's safety or adherence to the study protocol.

1. patients with moderate or severe acute respiratory failure or requiring noninvasive ventilation or oxygen or with spo2 \< 92% or tachypnea (respiratory rate ≥ 30 breaths/min). 2. patients treated with immunosuppressors and/or immunomodulators. 3. engrafted patients (organ and/or hematopoietic stem cells). 4. patients with uncontrolled auto-immune disease. 5. patients with known or suspected active (i.e. not controlled) bacterial, viral (excluding covid-19) or fungal infections. 6. patients with preexisting, severe and not controlled organ failure. 7. history or active malignancy requiring chemotherapy or radiation therapy (excluding 2 years disease free survivor patients). 8. pregnant or breast-feeding women. 9. illicit drug or alcohol abuse or dependence that may compromise the patient's safety or adherence to the study protocol. 10. use of any investigational or non-registered product within 3 months or within 5 half-lives preceding baseline, whichever is longer. 11. hypersensitivity to abx464 and/or its excipients. 12. any condition, which in the opinion of the investigator, could compromise the patient's safety or adherence to the study protocol.

patients with moderate or severe acute respiratory failure or requiring noninvasive ventilation or oxygen or with spo2 < 92% or tachypnea (respiratory rate ≥ 30 breaths/min). patients treated with immunosuppressors and/or immunomodulators. engrafted patients (organ and/or hematopoietic stem cells). patients with uncontrolled auto-immune disease. patients with known or suspected active (i.e. not controlled) bacterial, viral (excluding covid-19) or fungal infections. patients with preexisting, severe and not controlled organ failure. history or active malignancy requiring chemotherapy or radiation therapy (excluding 2 years disease free survivor patients). pregnant or breast-feeding women. illicit drug or alcohol abuse or dependence that may compromise the patient's safety or adherence to the study protocol. use of any investigational or non-registered product within 3 months or within 5 half-lives preceding baseline, whichever is longer. hypersensitivity to abx464 and/or its excipients. any condition, which in the opinion of the investigator, could compromise the patient's safety or adherence to the study protocol.

patients with moderate or severe acute respiratory failure or requiring noninvasive ventilation or oxygen or with spo2 < 92% or tachypnea (respiratory rate ≥ 30 breaths/min). patients treated with immunosuppressors and/or immunomodulators. engrafted patients (organ and/or hematopoietic stem cells). patients with uncontrolled auto-immune disease. patients with known or suspected active (i.e. not controlled) bacterial, viral (excluding covid-19) or fungal infections. patients with preexisting, severe and not controlled organ failure. history or active malignancy requiring chemotherapy or radiation therapy (excluding 2 years disease free survivor patients). pregnant or breast-feeding women. illicit drug or alcohol abuse or dependence that may compromise the patient's safety or adherence to the study protocol. use of any investigational or non-registered product within 3 months or within 5 half-lives preceding baseline, whichever is longer. hypersensitivity to abx464 and/or its excipients. any condition, which in the opinion of the investigator, could compromise the patient's safety or adherence to the study protocol.

1. patients with moderate or severe acute respiratory failure or requiring noninvasive ventilation or oxygen or with spo2 < 92% or tachypnea (respiratory rate ≥ 30 breaths/min). 2. patients treated with immunosuppressors and/or immunomodulators. 3. engrafted patients (organ and/or hematopoietic stem cells). 4. patients with uncontrolled auto-immune disease. 5. patients with known or suspected active (i.e. not controlled) bacterial, viral (excluding covid-19) or fungal infections. 6. patients with preexisting, severe and not controlled organ failure. 7. history or active malignancy requiring chemotherapy or radiation therapy (excluding 2 years disease free survivor patients). 8. pregnant or breast-feeding women. 9. illicit drug or alcohol abuse or dependence that may compromise the patient's safety or adherence to the study protocol. 10. use of any investigational or non-registered product within 3 months or within 5 half-lives preceding baseline, whichever is longer. 11. hypersensitivity to abx464 and/or its excipients. 12. any condition, which in the opinion of the investigator, could compromise the patient's safety or adherence to the study protocol.

1. patients with moderate or severe acute respiratory failure or requiring noninvasive ventilation or oxygen or with spo2 < 92% or tachypnea (respiratory rate ≥ 30 breaths/min). 2. patients treated with immunosuppressors and/or immunomodulators. 3. engrafted patients (organ and/or hematopoietic stem cells). 4. patients with uncontrolled auto-immune disease. 5. patients with known or suspected active (i.e. not controlled) bacterial, viral (excluding covid-19) or fungal infections. 6. patients with preexisting, severe and not controlled organ failure. 7. history or active malignancy requiring chemotherapy or radiation therapy (excluding 2 years disease free survivor patients). 8. pregnant or breast-feeding women. 9. illicit drug or alcohol abuse or dependence that may compromise the patient's safety or adherence to the study protocol. 10. use of any investigational or non-registered product within 3 months or within 5 half-lives preceding baseline, whichever is longer. 11. hypersensitivity to abx464 and/or its excipients. 12. any condition, which in the opinion of the investigator, could compromise the patient's safety or adherence to the study protocol.