Study of Multiple Candidate Agents for the Treatment of COVID-19 in Hospitalized Patients

This adaptive, randomized, placebo-controlled platform study is designed to rapidly assess multiple candidate agents as treatments for COVID-19 in hospitalized patients. Candidate agents will be evaluated frequently (through ongoing monitoring) for futility and safety, with candidate agents being added to and/or removed from the study on an ongoing basis, depending on the results of their evaluation. For inclusion, participants will need to be hospitalized with a clinical status of Grade 2 to Grade 5, as defined by the following Clinical Severity Status 8-Point Ordinal Scale: 1. Death 2. Hospitalized, on invasive mechanical ventilation or extracorporeal membrane oxygenation (ECMO) 3. Hospitalized, on noninvasive ventilation or high-flow oxygen devices 4. Hospitalized, requiring supplemental oxygen 5. Hospitalized, not requiring supplemental oxygen, requiring ongoing medical care (COVID-19 related or otherwise) 6. Hospitalized, not requiring supplemental oxygen, no longer requires ongoing medical care 7. Not hospitalized, limitation on activities and/or requiring home oxygen 8. Not hospitalized, no limitations on activities Participants will be randomized equally to either the candidate agent plus standard of care (SoC) or placebo plus SoC in a double-blind fashion. Participants who are randomized to placebo plus SoC will subsequently be randomized equally to a matching placebo corresponding to an available agent whose sub-protocol the patient qualified for (ie, a 2-stage randomization). Each participant in the placebo plus SoC group will only receive one type of placebo. Randomization will be stratified by baseline clinical severity of 2 on the 8-point ordinal scale (yes/no) and remdesivir use at baseline (yes/no). The study will evaluate each candidate agent separately as an add-on to the SoC to assess safety and efficacy. The comparator group for a candidate agent will include participants randomized to the placebo arm of any sub-protocol according to the following conditions: * Apremilast sub-protocol: participants who were enrolled concurrently to apremilast and who would have been eligible for the apremilast sub-protocol. * Lanadelumab sub-protocol: at a site where at least one participant was randomized to either lanadelumab active or placebo arms. * Zilucoplan sub-protocol: at a site where at least one participant was randomized to either the zilucoplan active or placebo arms.