REGEN-Cov antibody combination to prevent COVID-19 infection in kidney transplant recipient without detectable antibody response to optimal vaccine scheme.

To the editor:

Many kidney transplant recipients (KTRs) do not respond to an anti–severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine. Indeed, concordant data indicate that about 30% of KTRs do not develop antibodies after 3 doses of mRNA vaccines. , However, KTRs are at a high risk of severe forms of coronavirus disease 2019 (COVID-19) infection. Mortality rates are reported to reach 15% to 20%, and the need for hospitalization in an intensive unit care is even more likely.

In this setting, consideration for an alternative prevention strategy of COVID-19 infection is particularly required. Recently, the REGEN-Cov antibody combination (casirivimab + imdevimab; Regeneron Pharmaceuticals) has been proven to be efficient to prevent infection in persons at risk for infection because of household exposure to a person with SARS-CoV-2 infection.

Nevertheless, no data are available for preexposition prevention in patients at risk.

The French government recently authorized the use of REGEN-Cov to prevent COVID-19 infection in immunocompromised patients without any antibody response after 3 doses of anti–SARS-CoV-2 vaccine (https://www.has-sante.fr/jcms/p_3281999/fr/covid-19-autorisation-d-acces-precoce-accordee-a-un-traitement-prophylactique).

We report the use of REGEN-Cov in preexposition prevention in KTRs.

Among 402 KTRs having received 3 doses of vaccines and for whom serology was available, 119 (29.6%) had no antibody response (anti-S titer < 50 arbitrary units [AU]; SARS-CoV-2 immunoassay; Abbott; designed to detect IgG antibodies to the receptor-binding domain of the S1 subunit of the spike protein of SARS-CoV-2). Preexposition prevention was proposed to all of them.

During the study period, the delta variant accounted for >99% of COVID-19 cases. REGEN-Cov is effective against the delta variant.

The first dose of REGEN-Cov (1200 mg) was administered i.v. The subsequent doses (600 mg) were administered s.c. every 4 weeks. Nasopharyngeal swabs were obtained for patients to test for SARS-CoV-2 by quantitative reverse transcription polymerase chain reaction before each administration of REGEN-Cov. Anti-S antibodies were also measured before each treatment.

Ninety-one patients (76%) accepted, whereas 28 refused. Among the 91 patients, only 88 received a first dose of REGEN-Cov. One experienced COVID-19 infection 3 days before the scheduled perfusion of REGEN-Cov, and 2 declined treatment after initial acceptance.

Characteristics of the patients are depicted in Table 1 .

Table 1

Characteristics of study patients

Characteristics	Participants (n = 88)	Nonparticipants (n = 31)	P value
Age, yr	62 [55–70]	61 [51–70]	0.973
Sex, % male	63	59	0.664
Transplant vintage, mo	29 [14–91]	158 [60–194]	0.145
eGFR, ml/min per 1.73 m2	48 [30–68]	47 [31–79]	0.352
CNI use, %	81	74	0.629
MPA use, %	81	84	0.695
mTORi use, %	8	10	0.767
Belatacept use, %	10	10	0.928

CNI, cancineurin inhibitors; eGFR, estimated glomerular filtration rate; MPA, mycophenolic acid; mTORi, mammalian target of rapamycin.

Data are presented as median [interquartile range], 25th–75th interquartiles.

All of the 88 patients received at least 2 maintenance injections after the initial perfusion. No patient reported having been in contact with a COVID-19–positive person. No adverse effect was observed in any patient. No acute rejection occurred during the study period. Immunosuppressive treatment was not modified.

During treatment, anti-S antibody titers were >40,000 AU in all patients.

During the observed period, no patient of the prophylaxis group developed COVID-19 infection. By contrast, in those without prevention, 5 (16%; P < 0.001) experienced COVID-19 infection, and 2 of them required hospitalization in intensive care unit. One died 3 weeks after admission.

REGEN-Cov is safe in preexposition prevention in KTRs without detectable vaccine response. High antibody titers are achieved in all patients. Preliminary data suggest efficient prevention of COVID-19 infection in this high-risk population.