1339. Effects of Tixagevimab-Cilgavimab in Clinical Practice is Consistent with Preliminary Neutralization Studies

Abstract

Abstract Background Emergency use of tixagevimab-cilgavimab was based on data collected prior to the emergence of SARS-CoV-2 omicron variant and subvariants. Dosing recommendations changed twice based on neutralization data alone, leading to patients receiving different doses at varying intervals. We provide real-world data on efficacy of tixagevimab-cilgavimab in immunocompromised patients throughout 2022, including the incidence and timing of infection based on dosing scheme. Methods Charts of 471 patients who received and 126 patients who declined administration of tixagevimab-cilgavimab were analyzed through December 14th, 2022. We evaluated incidence of SARS-CoV2, severity, risk factors and vaccination status. For analysis, we grouped patients with similar dosing: Group A received one initial dose of 150mg/150mg of tixagevimab-cilgavimab, Group B received at least 300 mg/300 mg of tixagevimab-cilgavimab before July 1st, and Group C patients were up to date with the FDA dosing guidelines. Results The tixagevimab-cilgavimab group had higher incidence of stem cell transplant or CAR T-cell therapy (115/471, 24% compared to 18/126, 14% p < 0.01) and had higher vaccination status (411/471, 89% compared to 37/126, 29%, p < 0.0001). Patients that received tixagevimab-cilgavimab had a trend towards higher incidence of SARS-CoV-2 infection (70/471, 15% compared to 11/126, 9%; p = 0.08). Incidence of SARS-CoV-2 was similar amongst all dosing groups (6/21, 29% in Group A; 37/251, 15% in Group B, and 27/199, 14% in Group C, p = 0.188). Group C experienced the most infections in November and early December 2022.Figure 1.Number of SARS-CoV-2 infections per month based on dosing regimen Group A patients received one initial dose of 150 mg/150mg of tixagevimab-cilgavimab. Group B patients received at least 300 mg/300 mg of tixagevimab-cilgavimab before July 1st, 2022 . Group C patients were up to date with the FDA dosing guidelines. Conclusion The tixagevimab-cilgavimab group demonstrated increased incidence of SARS-CoV-2. This may reflect increased healthcare system utilization, as most infections were self-reported in this study. Those with the FDA recommended dose were most likely to develop SARS-CoV-2 in November and December 2022 when circulating variants were not neutralized by tixagevimab-cilgavimab in vitro. This suggests in vitro neutralization data correlates with clinical efficacy. Disclosures All Authors: No reported disclosures