Post-exposure prophylaxis with a monoclonal antibody cocktail after Bundibugyo ebolavirus exposure in adults and children.

Five individuals from a single family cluster-one rVSV-ZEBOV-vaccinated adult and four unvaccinated children aged 1-7 years-received investigational MBP134 as post-exposure prophylaxis (PEP) 5-6 days after high- to intermediate-risk occupational or household exposure to Bundibugyo ebolavirus (BDBV). MBP134 is a broadly neutralizing monoclonal antibody cocktail that has conferred protection against BDBV in non-human primates but, to our knowledge, has not previously been evaluated as PEP in humans. Given the absence of approved preventive interventions against BDBV and the substantial case-fatality rate of Bundibugyo virus disease (BVD), MBP134 was administered as an individual treatment attempt under emergency Investigational New Drug (eIND) authorizations. Administration was well tolerated, with no treatment-related adverse events. Throughout the 21-day monitoring period, all family members remained free of clinical or laboratory evidence of BVD, as assessed by daily medical evaluation and serial polymerase chain reaction (PCR) testing. Plasma Orthoebolavirus-reactive antibodies were detected after infusion, persisted throughout follow-up and mediated broad neutralizing activity against multiple Orthoebolavirus species, including authentic BDBV. Notably, endogenous BDBV-reactive IgM and IgA were detected in the adult after high-risk exposure despite persistently negative PCR results. Together, these findings support prospective evaluation of MBP134 as PEP for high-risk adult and pediatric contacts during BDBV outbreaks.