Systematic Review of the Clinical Effectiveness of Tixagevimab/Cilgavimab for Prophylaxis of Covid-19 in Immunocompromised Patients

ABSTRACT

Background/Aims Immunocompromised patients have a reduced ability to generate antibodies after COVID-19 vaccination, and are at a high risk of SARSPOSTERS CoV-2 infection, complications and mortality. Tixagevimab/Cilgavimab (Evusheld) is a combination of two monoclonal antibodies which bind to the SARS-CoV-2 spike protein, preventing the virus entering human cells. Tixagevimab/Cilgavimab has been approved as COVID-19 prophylaxis for immunocompromised individuals, and is being used in over 32 different countries. The phase III PROVENT clinical trial found that high-risk participants prophylactically administered Tixagevimab/Cilgavimab had a significantly reduced risk of COVID- 19 infection after three and six months compared to controls. However, the PROVENT trial was conducted prior to the SARS-CoV- 2 Omicron wave, and did not include participants who had been previously vaccinated or infected. This systematic review provides an updated summary of the real-world clinical evidence of the efficacy of Tixagevimab/Cilgavimab for immunocompromised patients. The review reports breakthrough COVID-19 infections as its primary outcome. COVID-19-related hospitalisations, ITU admissions and mortality were included as secondary outcomes. Methods Two independent reviewers conducted electronic searches of PubMed and Medxriv, on 03/08/22 and 01/10/22. Clinical studies which reported the primary outcome of breakthrough COVID-19 infections after Tixagevimab/Cilgavimab administration were included. Clinical effectiveness was determined using the case-control clinical effectiveness methodology. Odds ratios and 95% confidence intervals (CI) between intervention and control groups were also calculated. The GRADE tool was used to assess the level of certainty for the primary outcome. Results 17 clinical studies were included in the review, with a total of 24,773 immunocompromised participants from across the world, of whom 10,775 received Tixagevimab/Cilgavimab. One randomised controlled trial, ten retrospective cohort studies (two of which were preprints) and six prospective cohort studies (one preprint) were included. The majority of studies reported clinical outcomes during the SARS-CoV-2 Omicron wave. Six studies compared a Tixagevimab/Cilgavimab intervention group to a control group. Reasons for participant immunocompromise included rheumatology patients treated with immunosuppressant drugs, transplant recipients and those with malignancies. Overall, the clinical effectiveness of prophylactic Tixagevimab/Cilgavimab against COVID- 19 breakthrough infection was 40.47% (CI 29.82-49.67;p<0.0001), COVID-19 hospitalisation- 69.23% (CI 50.78-81.64;p<0.00001), ITU admission- 87.89% (CI 47.12-98.66;p=0.0008), all-cause mortality- 81.29% (66.93-90.28;p<0.0001 and COVID-19-specifc mortality- 86.36% (CI-6.21-99.70;p=0.0351). Conclusion There is a growing body of real-world evidence validating the original PROVENT phase III study regarding the clinical effectiveness of Tixagevimab/Cilgavimab as prophylaxis for immunocompromised groups, notably demonstrating effectiveness during the Omicron wave. This systematic review demonstrates the significant clinical effectiveness of prophylactic Tixagevimb/Cilgavimab at reducing COVID-19 infection, hospitalisation, ITU admission and mortality for immunosuppressed individuals. It is critically important that largerscale and better-controlled studies are performed to highlight the significant clinical benefit of prophylactic antibody treatment in immunocompromised groups.