The Effectiveness of the Use of Regdanvimab (CT-P59) in Addition to Remdesivir in Patients with Severe COVID-19: A Single Center Retrospective Study

Introduction: Coronavirus disease 2019 (COVID-19) still has a high mortality rate when it is severe. Regdanvimab (CT-P59), a neutralizing monoclonal antibody that has been proven effective against mild to moderate COVID-19, may be effective against severe COVID-19. This study was conducted to determine the effectiveness of the combined use of remdesivir and regdanvimab in patients with severe COVID-19. Methods: From March to early May 2021, 124 patients with severe COVID-19 were admitted to Ulsan University Hospital (Ulsan, Korea) and received oxygen therapy and remdesivir. Among them, 25 were also administered regdanvimab before remdesivir. We retrospectively compared the clinical outcomes between the remdesivir alone group [n = 99 (79.8%)] and the regdanvimab/remdesivir group [n = 25 (20.2%)]. Results: The oxygen-free days on day 28 (primary outcome) were significantly higher in the regdanvimab/remdesivir group [mean +/- SD: 19.36 +/- 7.87 vs. 22.72 +/- 3.66, p = 0.003]. The oxygen-free days was also independently associated with use of regdanvimab in the multivariate analysis, after adjusting for initial pulse oximetric saturation (SpO(2))/fraction of inspired oxygen (FiO(2)) ratio (severity index). Further, in the regdanvimab/remdesivir group, the lowest SpO(2)/FiO(2) ratio during treatment was significantly higher (mean +/- SD: 237.05 +/- 89.68 vs. 295.63 +/- 72.74, p = 0.003), and the Kaplan-Meier estimates of oxygen supplementation days in surviving patients (on day 28) were significantly shorter [mean +/- SD: 8.24 +/- 7.43 vs. 5.28 +/- 3.66, p = 0.024]. Conclusions: In patients with severe COVID-19, clinical outcomes can be improved by administering regdanvimab, in addition to remdesivir.