TIXAGEVIMAB/CILGAVIMAB for Covid-19 Pre-exposition Prophylaxis in Solid Organ Transplanted Recipients

Covid-19 has a very bad prognosis in solid organ transplant recipients with a 60 days-mortality exceeding 20%. For this reason, transplant patients were prioritized to receive Covid-19 vaccination since December 2020 in France. Unfortunately, the vaccine response of these patients is insufficient after a standard vaccine regimen including 2 doses of mRNA (messenger ribonucleic acid) vaccine with a 50% seroconversion rate in many cohorts. As a result, on the advice of the "Conseil National d'Orientation Vaccinale", the French Health Authorities has authorized physicians to offer a 3rd dose of vaccine to organ transplant patients since April 11, 2021. The subsequent studies showed that half of the patients who did not seroconvert after the 2nd dose did develop a vaccine response after the third dose. For patients who do not respond after the 3rd dose, the clinicians are now allowed to offer a 4th dose of vaccine.

Unfortunately, approximately 25% of patients still remain non-responders to this 3- or 4-doses vaccine regimen. In addition, transplant recipients who do not developed a vaccine response after the 3rd dose are very unlikely to respond after the 4th dose. For patients who do not respond to the vaccination, the French Health Authorities had authorized the infusion of SARS Cov2 (Severe Acute Respiratory Syndrome Coronavirus 2) monoclonal antibodies as a pre-exposition prophylaxis in immunocompromised patients.

The value of using the TIXAGEVIMAB/CILGAVIMAB monoclonal antibody cocktail as primary prophylaxis has been demonstrated in the general population but this study did not include immunocompromised patients.

Here, the investigators propose to study the pharmacokinetics of TIXAGEVIMAB/CILGAVIMAB given in a pre-exposition prophylaxis scheme in non-responder solid organ transplanted patients after an adapted vaccinal scheme (i.e. 3 doses or more of mRNA vaccines).