1. Patient is not expected to survive for more than 24 hours. 2. Patient is on invasive mechanical ventilation with intubation for more than 48 hours prior to Screening. 3. Severe pre-existing cardiac disease (ie, New York Heart Association Class 3 or Class 4, acute coronary syndrome or persistent ventricular tachyarrhythmias). 4. Patient has an unresolved Neisseria meningitidis infection. 5. Use of the following medications and therapies: a. Current treatment with a complement inhibitor, b. Intravenous immunoglobulin (IVIg) within 4 weeks prior to randomization on Day 1. 6.Treatment with investigational therapy in a clinical study within 30 days before randomization, or within 5 half -lives of that investigational therapy, whichever is greater Exceptions: a.Investigational therapies will be allowed if received as part of best supportive care through an expanded access protocol or emergency approval for the treatment of COVID 19. b.Investigational antiviral therapies (such as remdesivir) will be allowed even if received as part of a clinical study. 7. Female patients who are breastfeeding or who have a positive pregnancy test result at Screening. 8. History of hypersensitivity to any ingredient contained in the study drug, including hypersensitivity to murine proteins. 9.Patient who is not currently vaccinated against N. meningitidis, unless the patient agrees to receive prophylactic treatment with appropriate antibiotics for at least 8 months after the last infusion of study drug or until at least 2 weeks after the patient receives vaccination against N. meningitidis.

1. Patient is not expected to survive for more than 24 hours. 2. Patient is on invasive mechanical ventilation with intubation for more than 48 hours prior to Screening. 3. Severe pre-existing cardiac disease (ie, New York Heart Association Class 3 or Class 4, acute coronary syndrome or persistent ventricular tachyarrhythmias). 4. Patient has an unresolved Neisseria meningitidis infection. 5. Use of the following medications and therapies: a. Current treatment with a complement inhibitor, b. Intravenous immunoglobulin (IVIg) within 4 weeks prior to randomization on Day 1. 6.Treatment with investigational therapy in a clinical study within 30 days before randomization, or within 5 half -lives of that investigational therapy, whichever is greater Exceptions: a.Investigational therapies will be allowed if received as part of best supportive care through an expanded access protocol or emergency approval for the treatment of COVID 19. b.Investigational antiviral therapies (such as remdesivir) will be allowed even if received as part of a clinical study. 7. Female patients who are breastfeeding or who have a positive pregnancy test result at Screening. 8. History of hypersensitivity to any ingredient contained in the study drug, including hypersensitivity to murine proteins. 9.Patient who is not currently vaccinated against N. meningitidis, unless the patient agrees to receive prophylactic treatment with appropriate antibiotics for at least 8 months after the last infusion of study drug or until at least 2 weeks after the patient receives vaccination against N. meningitidis.