Post-Exposure Prophylaxis with a monoclonal antibody cocktail Following 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 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 following 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.