Background and Importance Cilgavimab/tixagevimab are recombinant human IgG1ĸ monoclonal antibodies, which are indicated for COVID-19 pre-exposure prophylaxis in adults and adolescents ≥12 years of age weighing ≥40 kg.

Aim and Objectives To assess patients who are potential candidates for treatment with cilgavimab/tixagevimab in a tertiary care hospital and to describe the search strategy.

Material and Methods In Spain, potential candidates for treatment with cilgavimab/tixagevimab are people with a high degree of immunosuppression (due to pathology or treatment) who do not respond adequately to vaccination. The Spanish Agency of Medicines and Health Products establishes the conditions for patients who are candidates for treatment with cilgavimab/tixagevimab¹ . A search for patients was carried out, prioritising the following criteria: haematological patients on treatment with rituximab during the last 9 months, patients with solid organ transplant, patients with multiple sclerosis on treatment with ocrelizumab/rituximab, and patients with recent infection by COVID-19 who belong to any risk group. All of them underwent serology, including in the study those with negative serology (anti-anati-S antibodies < 260 BAU/ml). Those patients were scheduled for cilgavimab/tixagevimab administration.

Results 112 patients (38 = haematological patients on rituximab treatment, 50 = multiple sclerosis patients on rituximab/ocrelizumab treatment and 24 = kidney transplantation) were enrolled. 72 patients were included, 38 women (52.8%), median age 59.5 years old (27-77). The cause of exclusion was positive serology in all cases. 64 patients (88.9%) were on treatment with biologic immunomodulators (35 haematologic patients treated with rituximab <9 months, 27 patients with multiple sclerosis on treatment with rituximab/ocrelizumab/interferon beta-1A and 1 patient on treatment with adalimumab) and the rest were kidney transplant patients. Cilgavimab/tixagevimab was administered to 62 patients (86.1%), 7 patients with unknown reasons, 2 patients had COVID-19 infection and 1 patient had to be excluded for deep vein thrombosis due to the development of symptoms at the time of the appointment.

Conclusion and Relevance More than half of the patients enrolled did not have an adequate response to COVID-19 vaccination. The search strategy was a good tool for administering pre-exposure prophylaxis of COVID-19 to these more vulnerable patients. Further studies are needed to evaluate the effectiveness of the treatment.

References and/or Acknowledgements 1. https://www.aemps.gob.es/la-aemps/ultima-informacion-de-la-aemps-acerca-del-covid%E2%80%9119/prevencion-frente-a-la-covid-19/personas-candidatas-a-recibir-evusheld-en-espana/#:~:text=En%20Espa%C3%B1a%2C%20son%20potenciales%20candidatas,responden%20adecuadamente%20a%20la%20vacunaci%C3%B3n.

Conflict of Interest No conflict of interest