ABSTRACT
Monoclonal antibodies (MAbs) targeting the Spike glycoprotein of SARS-CoV-2 is a key strategy to prevent severe COVID-19. Here, the efficacy of two monoclonal antibody bitherapies against SARS-CoV-2 was assessed on 92 patients at high risk of severe COVID-19 between March and October 2021 (Bichat-Claude Bernard Hospital, Paris, France). Nine patients died despite appropriate management. From 14 days following treatment initiation, we observed a slower viral load decay for patients treated with the bitherapy Bamlanivimab/Etsevimab compared to the Casirivimab/Imdevimab association therapy (P = 0.045). The emergence of several mutations on the Spike protein known to diminish antiviral efficacy was observed from 1 to 3 weeks after infusion. The Q493R mutation was frequently selected, located in a region of joint structural overlap by Bamlanivimab/Etsevimab antibodies. Despite that this study was done on former SARS-CoV-2 variants (Alpha and Delta), the results provide new insights into resistance mechanisms in SARS-CoV-2 antibodies neutralization escape and should be considered for current and novel variants. IMPORTANCE Monoclonal antibody bitherapies (MAbs) are commonly prescribed to treat severe SARS-CoV-2-positive patients, and the rapid growth of resistance mutation emergence is alarming globally. To explore this issue, we conducted both clinical and genomic analyses of SARS-CoV-2 in a series of patients treated in 2021. We first noticed that the two dual therapies prescribed during the study had different kinetics of viral load decay. Rapidly after initiation of the treatments, resistance mutations emerged in the interface between the MAbs and the target Spike glycoprotein, demonstrating the importance to continuously screen the viral genome during treatment course. Taken together, the results highlight that viral mutations may emerge under selective pressure, conferring a putative competitive advantage, and could rapidly spread, as observed for the Omicron variant.