Efficacy and Safety of Nirmatrelvir/Ritonavir in Severe Hospitalized Patients with COVID-19 and in Patients at High Risk for Progression to Critical Illness: A Real-World Study.

Background: Nirmatrelvir/Ritonavir is an orally administered anti-SARS-Cov-2 drug used in mild-to-moderate COVID-19 patients. Our retrospective cohort study aims to evaluate the efficacy and safety of Nirmatrelvir/Ritonavir in severe hospitalized patients with Omicron infection, as well as in patients at high risk for progression to critical illness in real-world settings. Methods: A total of 350 patients received Nirmatrelvir/Ritonavir while 350 matched controls did not. Patients with confirmed COVID-19 were administered Nirmatrelvir 300 mg and Ritonavir 100 mg orally twice a day for 5 days, with the medication initiated on the first day after admission. The primary endpoint of the study was a composite outcome of hospitalization or death from any cause within 28 days. Secondary endpoints included the occurrence of adverse events and the evaluation of serum levels of IL-6 and viral load. Results: We documented the mortality risk from any cause within 28 days, viral load, serum IL-6 levels, and adverse events. Nirmatrelvir/Ritonavir reduced the 28-day risk of all-cause mortality by 86% ( P  = .011, hazard ratio (HR) = 0.14, 95% confidence interval (CI) = 0.03, 0.64). At baseline, the serum level of IL-6 was significantly higher in the antiviral treatment group compared to the control group ( P  < .001), but no significant difference ( P  = .990) was found between the two groups at discharge. In CKD patients undergoing hemodialysis, no significant worsening of renal function was observed in the Nirmatrelvir/Ritonavir treatment group compared to the control group. Conclusion: Nirmatrelvir/Ritonavir may reduce the 28-day risk of all-cause mortality in critically ill patients with COVID-19 and in patients at high risk for critical disease progression.