Master Protocol: Patients are excluded from the study if any of the following criteria apply (as well as all criteria from the appropriate candidate-specific trial protocol): 1. Alanine aminotransferase (ALT) and/or aspartate aminotransferase (AST) >5 times the upper limit of normal (ULN) 2.Stage 4 severe chronic kidney disease or requiring dialysis (i.e., estimated glomerular filtration rate <30 mL/min/1.73 m2) 3.Pregnant or breast feeding 4. Anticipated transfer to another hospital which is not a study site within 72 hours 5. Allergy to any study medication 6. Patients taking other prohibited drugs (as outline in CST protocol) within 30 days or 5 times the half-life (whichever is longer) of enrolment 7. Patients participating in another CTIMP trial Nomacopan Candidate-Specific Trial: For the purpose of the nomacopan candidate-specific trial, appendix exclusion criteria 6 has been amended from the Master protocol as follows, to restrict the population of patients that will be included in the trial: 6. Patients taking the following prohibited drugs: Other complement inhibiting drug such as eculizumab (Soliris®). Any other drug which directly inhibits cytokines, chemokines or proinflammatory mediators such as tocilizumab (Actemra®/RoActremra®), anakinra (Kineret®), etanercept (Enbrel®), infliximab (Remicade®) or adalimumab (Humira®). N.B. Whilst it is not thought that there is likely to be any adverse interaction between nomacopan and any of these drugs, in the context of a clinical trial, it would be impossible to distinguish the effects of those agents from that of nomacopan. Corticosteroids, antivirals and antibiotics are permitted in conjunction with nomacopan therapy. Additional exclusion criteria specific to this candidate specific appendix are: 8. Weight less than 50kg or more than 100kg CST-2 (EIDD-2801) additional exclusion criteria: 8. Has a febrile respiratory illness that includes pneumonia that results in hospitalisation, or requires hospitalisation, oxygenation, mechanical ventilation, or other supportive modalities. 9. Has a platelet count less than 50x10^9/L. 10. Is experiencing adverse events or laboratory abnormalities that are Grade 3 or above based on the CTCAE v5 grading. 11. Has clinically significant liver dysfunction or renal impairment. 12. Has history of Hepatitis C infection or concurrent bacterial pneumonia. 13. Has received an experimental agent (vaccine, drug, biologic, device, blood product, or medication) within 30 days prior to the first dose of study drug. 14. In the opinion of the investigator, has significant end-organ disease as a result of relevant comorbidities: chronic kidney disease, congestive heart failure, peripheral vascular disease including diabetic ulcers. 15. Has a SaO2<95% by oximetry or has lung disease that requires supplemental oxygen or maintenance steroids. 16. Has any condition that would, in the opinion of the investigator, put the patient at increased risk for participation in a clinical study.

Master Protocol: Patients are excluded from the study if any of the following criteria apply (as well as all criteria from the appropriate candidate-specific trial protocol): 1. Alanine aminotransferase (ALT) and/or aspartate aminotransferase (AST) >5 times the upper limit of normal (ULN) 2.Stage 4 severe chronic kidney disease or requiring dialysis (i.e., estimated glomerular filtration rate <30 mL/min/1.73 m2) 3.Pregnant or breast feeding 4. Anticipated transfer to another hospital which is not a study site within 72 hours 5. Allergy to any study medication 6. Patients taking other prohibited drugs (as outline in CST protocol) within 30 days or 5 times the half-life (whichever is longer) of enrolment 7. Patients participating in another CTIMP trial Nomacopan Candidate-Specific Trial: For the purpose of the nomacopan candidate-specific trial, appendix exclusion criteria 6 has been amended from the Master protocol as follows, to restrict the population of patients that will be included in the trial: 6. Patients taking the following prohibited drugs: Other complement inhibiting drug such as eculizumab (Soliris®). Any other drug which directly inhibits cytokines, chemokines or proinflammatory mediators such as tocilizumab (Actemra®/RoActremra®), anakinra (Kineret®), etanercept (Enbrel®), infliximab (Remicade®) or adalimumab (Humira®). N.B. Whilst it is not thought that there is likely to be any adverse interaction between nomacopan and any of these drugs, in the context of a clinical trial, it would be impossible to distinguish the effects of those agents from that of nomacopan. Corticosteroids, antivirals and antibiotics are permitted in conjunction with nomacopan therapy. Additional exclusion criteria specific to this candidate specific appendix are: 8. Weight less than 50kg or more than 100kg CST-2 (EIDD-2801) additional exclusion criteria: 8. Has a febrile respiratory illness that includes pneumonia that results in hospitalisation, or requires hospitalisation, oxygenation, mechanical ventilation, or other supportive modalities. 9. Has a platelet count less than 50x10^9/L. 10. Is experiencing adverse events or laboratory abnormalities that are Grade 3 or above based on the CTCAE v5 grading. 11. Has clinically significant liver dysfunction or renal impairment. 12. Has history of Hepatitis C infection or concurrent bacterial pneumonia. 13. Has received an experimental agent (vaccine, drug, biologic, device, blood product, or medication) within 30 days prior to the first dose of study drug. 14. In the opinion of the investigator, has significant end-organ disease as a result of relevant comorbidities: chronic kidney disease, congestive heart failure, peripheral vascular disease including diabetic ulcers. 15. Has a SaO2<95% by oximetry or has lung disease that requires supplemental oxygen or maintenance steroids. 16. Has any condition that would, in the opinion of the investigator, put the patient at increased risk for participation in a clinical study.