ABSTRACT
OBJECTIVES: There is a scarcity of data on the outcomes and predictors of therapeutic failure of monoclonal antibodies (mAbs) in frail patients with COVID-19. METHODS: Prospective study including consecutive COVID-19 outpatients referred by primary care physicians for mAb treatment. The outcomes evaluated were 60-day mortality, time to SARS-CoV-2 clearance, need for hospitalization, and O2 therapy. RESULTS: Among 1026 COVID-19 patients enrolled, 60.2% received casirivamab/imdevimab and 39.8% sotrivimab. Median age was 63 years, 52.4% were males and median time from positive nasopharyngeal swab to mAbs administration was 3 days (interquartile range, 2-5). 78.1% were vaccinated. Overall, the 60-day mortality was 2.14%. No differences in outcomes were observed between the two mAbs used. No difference was observed in mortality between vaccinated and unvaccinated patients (P = 0.925); although, lower rate of hospitalization (P <0.005), less need for O2 therapy (P <0.0001) and reduced nasopharyngeal swab negativity time (P <0.0001) were observed in vaccinated patients. Early administration of mAbs was associated with lower mortality (P <0.007), whereas corticosteroid use worsened prognosis (P <0.004). The independent predictors associated with higher mortality were older age (P <0.0001), presence of active hematologic malignancies (P <0.0001), renal failure (P <0.041), and need for O2 therapy (P <0.001). CONCLUSION: This study shows similar effectiveness among mAbs used, regardless of vaccination status and identifies patients with COVID-19 in whom mAbs have poor activity.