Master Protocol Co-primary endpoints: For dose finding (phase I) • Dose limiting toxicities (Safety and Tolerability of drug under study – CTCAE v5 Grade ≥3 adverse events) For efficacy evaluation (phase II) one of the following depending on the population the candidate is being evaluated in: • Group A (severe disease) Time to clinical improvement: Improvement will be determined according to the WHO Progression Scale. Improvement, defined by a minimum 2-step change in the scale, will be analysed as time to event, measured up to 29 days from randomisation. • Group B (mild-moderate disease) Pharmacodynamics of drug defined as time to negative viral titres in nose and/or throat swab, measured up to 29 days from randomisation. Nomacopan Candidate-Specific Trial: Time to clinical improvement: improvement will be determined according to the WHO clinical severity score (WHO Working Group on the Clinical Characteristics of COVID-19 infection 9-point ordinal scale). Improvement, defined by a minimum 2-step change in the scale, will be analysed as time to event, measured up to day 29. For CST-2 (EIDD-2801): To determine the safety and tolerability of multiple ascending doses of EIDD-2801. Efficacy Objective: To determine the ability of EIDD-2801 to improve viral clearance (time to negative PCR).

Master Protocol Co-primary endpoints: For dose finding (phase I) • Dose limiting toxicities (Safety and Tolerability of drug under study – CTCAE v5 Grade ≥3 adverse events) For efficacy evaluation (phase II) one of the following depending on the population the candidate is being evaluated in: • Group A (severe disease) Time to clinical improvement: Improvement will be determined according to the WHO Progression Scale. Improvement, defined by a minimum 2-step change in the scale, will be analysed as time to event, measured up to 29 days from randomisation. • Group B (mild-moderate disease) Pharmacodynamics of drug defined as time to negative viral titres in nose and/or throat swab, measured up to 29 days from randomisation. Nomacopan Candidate-Specific Trial: Time to clinical improvement: improvement will be determined according to the WHO clinical severity score (WHO Working Group on the Clinical Characteristics of COVID-19 infection 9-point ordinal scale). Improvement, defined by a minimum 2-step change in the scale, will be analysed as time to event, measured up to day 29. For CST-2 (EIDD-2801): To determine the safety and tolerability of multiple ascending doses of EIDD-2801. Efficacy Objective: To determine the ability of EIDD-2801 to improve viral clearance (time to negative PCR).