Study of Abatacept in the Treatment of Hospitalized COVID-19 Participants With Respiratory Compromise

Adjusted Mean Change From Baseline in the Ordinal 8-Point Clinical Status Scale on Day 28

Adjusted mean change from baseline based on the following Ordinal 8-point Clinical Status Scale that was proposed for the National Institute of Allergy and Infectious Diseases (NIAID) Adaptive COVID-19 Treatment Trial (ACTT) and is recorded by the worst score (lowest number) state for each day: 1. Death; 2. Hospitalized, on invasive mechanical ventilation or extracorporeal membrane oxygenation (ECMO); 3. Hospitalized, on non-invasive mechanical 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 limitation on activities Baseline is defined as the last assessment done prior or on Day 1

Time frame: Baseline and on Day 28

Percentage of Participants Who Died

Percentage of participants who died due to any cause. Participants in the following Ordinal 8-point Clinical Status Scale that is recorded by the worst score (lowest number) state for each day meet this definition: 1\) Death

Time frame: From first dose to 28 days post first dose

Percentage of Participants Alive and Free of Respiratory Failure on Day 28±3

Respiratory failure is defined by the type of resources required as defined by the use of any of these: Mechanical ventilation, extracorporeal membrane oxygenation (ECMO) or oxygen delivery by noninvasive positive pressure or high flow nasal cannula. Participants in the following Ordinal 8-point Clinical Status Scale that is recorded by the worst score (lowest number) state for each day meet this definition: 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 limitation on activities