LB1531. Administration of Abatacept or Infliximab Reduces Mortality in Hospitalized Patients with COVID-19 Pneumonia: Results from the ACTIV-1 IM Master Protocol

Abstract Background Severe COVID-19 infection is characterized by a dysregulated hyperinflammatory state that contributes to morbidity and mortality. Immunomodulatory therapy has been shown improve outcomes. We investigated if abatacept, CTLA-4-Ig, selective costimulation modulator, provides additional benefit when added standard of care. Methods conducted double-blind, randomized, placebo-controlled trial evaluating abatacept (given as single infusion 10mg/kg, maximum 1000 mg) compared care (including remdesivir dexamethasone) in patients hospitalized with pneumonia. The primary outcome was median time recovery day 29. Key secondary endpoints included 28-day Results A total 1019 received an (509 assigned 510 placebo), constituting the analyzed modified intention-to-treat cohort. mean age 54.9 years (SD 14.65), 60.5% were male, 44.2% Hispanic or Latino 13.7% black. Patients evenly matched terms severity illness, comorbidities. Participants randomized did not show statistically significant difference endpoint rate ratio 1.135 (95% CI 0.996-1.294, p=0.057) placebo. (IQR) 9 days (8, 10) for both groups. mortality arm 11.0% control 15.0% (OR 0.62 0.41, 0.94)), 37.8% lower odds dying receiving abatacept. improvement demonstrated requiring low high flow O2 at baseline but seen who required mechanical ventilation ECMO randomization. Subgroup analysis identified strongest effect those CRP >75mg/L, >65 diabetics. Safety data slightly risk adverse events. Rates infections similar (abatacept 16.1% placebo 14.3%). Conclusion Although single-dose IV demonstrate recovery, it substantial reduction Disclosures All Authors: No reported disclosures.