Background and Importance Some COVID-19 authorised drugs target the entry of SARS CoV-2 into the host cell, such as the combination of monoclonal antibodies tixagevimab/cilgavimab (T/C), while others prevent viral replication, such as the antivirals remdesivir and nirmatrelvir/ritonavir. Pre-exposure prophylaxis with T/C is indicated in frail patients at risk of developing severe COVID-19. One pivotal study reported a 77% reduction in disease risk compared to placebo, with protection estimated at least six months.

Aim and Objectives To evaluate how many patients have developed COVID-19 that required treatment with a specific antiviral among the ones in prophylaxis with T/C in our hospital.

Material and Methods Through the analysis of AIFA Monitoring Registers it was possible to obtain data of patients in prophylaxis with T/C and subsequently treated with COVID-19 antiviral. The data obtained refers to the period between 10th March 2022 (date of the first administration of prophylaxis in the hospital) and 10th September 2023. Cases of ineffectiveness of T/C have been reported in the National Pharmacovigilance Network.

Results During the considered period, 314 patients were treated with T/C prophylaxis. Of these, 9 (2.9%) received remdesivir, 6 (1.9%) remdesivir early treatment, 4 (1.3%) nirmatrelvir/ritonavir. 1 patient (0.3%) contracted the infection 3 times after prophylaxis (the first within 1 month and the following after 6 months) requiring 3 antiviral treatments: nirmatrelvir/ritonavir, remdesivir early treatment and remdesivir. Overall, 6.4% of patients undergoing prophylaxis were subsequently treated with at least one antiviral, 85% of them within 6 months. The average time between prophylaxis and antiviral treatment was 113 days.

Conclusion and Relevance The AIFA Monitoring Registers have been a useful tool for the clinical evaluation of the therapeutic efficacy of T/C prophylaxis and for pharmacovigilance activities. In the sample considered, 93,6% of patients who received prophylaxis didn’t develop COVID-19 that required antiviral treatment in a hospital setting. Our data only refers to inpatients subjects, thus representing a limitation for the analysis; T/C prophylaxis for frail patients has however proved to be a valuable resource in addition to vaccination.

References and/or Acknowledgements 1. EVUSHELD-EPAR.

2. Studio PROVENT https://classic.clinicaltrials.gov/ct2/show/NCT04625725

3. https://www.aifa.gov.it/registri-farmaci-sottoposti-a-monitoraggio

Conflict of Interest No conflict of interest.