Evaluation of neutralizing capacity of tixagevimab plus cilgavimab: a case-series study with comparison to a vaccinated population

Abstract

Abstract AZD7442 (150 mg of tixagevimab plus 150 mg cilgavimab) has been approved for the pre-exposure prophylaxis of COVID-19 and for the treatment of adults and adolescents with COVID-19 who do not require supplemental oxygen and who are at increased risk of severe COVID-19. In this study, two patients received AZD7442 for immunoprophylaxis. A cohort of subject who had received the BNT162b2 mRNA COVID‐19 vaccine has been included to compare strategies. Neutralizing antibodies (NAbs) against several variants were measured (wild-type, Alpha, Beta, Gamma, Delta, Omicron BA.5 and XBB.1.5). Binding antibodies have also been measured. NAbs T1/2 for AZD7442 was 8.1 days (95% CI: 5.1–19.5 days) and was 11.8 days (95% CI: 7.9–23.7 days) for the primo-vaccination cohort. The time to reach NAbs negativity was 108.3 days (95% CI: 66.9–130.7) for AZD7442 compared to 95.4 days (95% CI: 31.0–119.7 days) for primo-vaccination cohort. The time to reach NAbs negativity differs between variants with the maximum value obtained for the Alpha (i.e., 101.1 days (95% CI: 30.0–135.4 days)) and the minimum obtained for the Beta (i.e., 61.2 days (95% CI: 37.8–77.1 days)). Our results reinforces the need of reviewing the use of AZD7442 in relation to variant of concern and potentially adapting its administration schedule. AZD7442 could be indicated for short-term prophylaxis in frail patients who may be acutely exposed to SARS-CoV-2.