Anti-SARS-CoV-2 antibody titer transition and clinical course after casirivimab-imdevimab administration for the treatment of COVID-19: Evaluation of casirivimab-imdevimab efficacy and SARS-CoV-2 infection status

Abstract

Aims: In July 2021, the administration of casirivimab-imdevimab, a neutralizing antibody cocktail, was approved by the Ministry of Health, Labor and Welfare of Japan. We aimed to examine the transition of the anti-severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) antibody titer and the clinical course of patients after casirivimab-imdevimab administration. Materials and Methods: High-risk patients with coronavirus disease-19 (COVID-19) infection who did not require oxygen administration on admission were divided into antibody-treated and untreated groups. We measured the titers of anti-SARS-CoV-2 nucleocapsid (N) protein and anti-SARS-CoV-2 spike (S) protein antibodies and compared the clinical courses of both groups. Results: There was no significant difference in the patient background at admission between the two groups. The median times from onset to anti-S seroconversion were 8 and 12 days in the antibody-treated and untreated groups, respectively; it was significantly shorter in the antibody-treated group. The median titers of the anti-S antibody at the time of seroconversion were 125 and 7.8 U/mL in the antibody-treated and untreated groups, respectively; it was significantly higher in the antibody-treated group. There was no significant difference in the anti-N antibody titer transition between the two groups. The median times from onset to recovery were 9 and 14 days in the antibody-treated and untreated groups, respectively; it was significantly shorter in the antibody-treated group. Conclusions: Casirivimab-imdevimab can improve the clinical course of patients with COVID-19. The measurement of titers of anti-S protein antibodies is useful in the evaluation of casirivimab-imdevimab efficacy.