Impact of Delay Between Administration of Inmazeb Administration and Vaccination by Ervebo on Vaccine Immune Response on Healthy Volunteers

Starting soon · Phase 2

Conditions studied: Ebola Virus Disease

In brief

Ebola virus disease (EVD) is emerging regularly in various African countries for various reasons: during contact with mortal remains, during an unsafe burial or following the viral dissemination around a recovered patient. However, tools to fight the spread of the disease are being made available to countries affected by EVD. A vaccine (Ervebo), developed by the Merck laboratory, demonstrated its efficacy in protecting contacts and contacts of contacts in the "Ebola That's Enough" trial and two monoclonal antibodies (Mabs) have demonstrated their efficacy in reducing mortality in patients with EVD: REGN-E3B (Inmazeb) and Mab114 (Ebanga). The question of their use in post-exposure prophylaxis (PEP), defined as the treatment of contacts at very high risk of contracting EVD, is essential. Vaccination with Ervebo does not appear to be a good standalone option for PEP, particularly because antibody synthesis is delayed, and the vaccine is likely to be inactive for 10 days after administration. Monoclonal antibodies, on the other hand, seem to be a promising avenue in this indication because of their rapid action on the inhibition of virus entry into the cell. Moreover, Ervebo vaccine expresses the viral target recognized by mAbs, GP EBOV. It is therefore possible that the vaccine response (production of vaccine antibodies) is inhibited by mAbs, which bind to GP EBOV and prevent vaccine replication, particularly in the case of concomitant administration. However, no data on vaccine efficacy in combination are available. The question of the interaction between the monoclonal antibody and Ervebo and the delay between the administration of these two strategies remains unresolved. The hypothesis of this trial is that Ervebo vaccine efficacy is diminished with the concomitant administration of a monoclonal antibody, especially if this administration is close (short time between Mabs and vaccination). We hypothesize that with an optimal delay between Mabs and vaccination, the immunogenicity of the vaccine when administered with monoclonal antibodies could be non-inferior to the vaccine alone, thus providing optimal short and long term protection. The main objective of this study is to evaluate the extent of effect, if any, of Inmazeb administration on vaccine-induced neutralizing antibody responses to Zaire Ebola virus by Ervebo vaccine. If an interaction is observed, this will possibly enable determination of the time interval required between the administration of Inmazeb and Ervebo vaccine. The trial will have 6 arms. A control arm of vaccination alone will serve to characterize the immune response to the vaccine and it will be used as a comparator of vaccine immune response in the intervention arms. A control arm of mAb alone will serve to characterize the pharmacokinetic profile of mAb in the Guinean population. The 4 arms including different doses of Inmazeb plus vaccination were designed to mimic a time interval between Ervebo and Inmazeb administration (15, 57 and 169 days after Inmazeb).

Key facts

Study ID

NCT05202288

Run by

ANRS, Emerging Infectious Diseases

People needed

132

Starts

2027-01-01

Expected to finish

2027-08-01

Last updated by the study team

2026-01-22

Who can join

Age: 18 and older. Sex: any. Healthy volunteers: accepted.

You may qualify if…

• Available for the duration of the protocol follow-up;
• Consent to participate ;
• Agreed not to participate in another clinical research study until the end of the trial follow-up.

You may not qualify if…

• Prior history of EVD (self-reported);
• Previous vaccination with r-VSV-ZEBOV or any other Ebola vaccine (self-reported);
• Previous administration of Ebola antibody;
• HIV-1 and/or 2 positive serology;
• Pregnant women (positive pregnancy test);
• Breastfeeding women;
• To the opinion of the investigator, any clinically significant acute/chronic condition that would limit the participant\'s ability to meet the requirements of the study protocol;
• Taking Immunosuppressive therapy;
• Participation in another clinical research study within the last 30 days;
• Allergy to any component of the vaccine or Mabs;
• Person deprived of freedom by a judicial or administrative decision;
• Any other reason that, at the investigator\'s discretion, would compromise the participant\'s safety and cooperation in the trial.

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