Importance: Fostamatinib, a spleen tyrosine kinase inhibitor, has been reported to improve outcomes of COVID-19.
Objective: To evaluate the efficacy and safety of fostamatinib in adults hospitalized with COVID-19 and hypoxemia.
Design, Setting, And Participants: This multicenter, phase 3, placebo-controlled, double-blinded randomized clinical trial was conducted at 41 US sites and 21 international sites between November 17, 2021, and September 27, 2023; the last follow-up visit was December 31, 2023.