A highly potent nanobody-based bispecific therapeutic provides broad-spectrum protection against ebolavirus

The highly lethal Ebola virus species-Zaire (EBOV), Sudan (SUDV), and Bundibugyo (BDBV)-pose persistent threats to global health. Current antibody therapies target EBOV but lack broad neutralization across ebolaviruses. Recent pan-ebolavirus strategies rely on antibody cocktails. Here, we identified two camelid-derived nanobodies (1A10 and BA2) that neutralize EBOV, SUDV, and BDBV in vitro and protect female rodents against these pathogens. High-resolution cryo-EM structures of their GP complexes showed that 1A10 and BA2 bind conserved but non-overlapping epitopes near the GP1 base and GP2's internal fusion loop (IFL), and biochemical analyses revealed their distinct neutralization mechanisms. To further improve efficacy, we engineered a bispecific antibody (BA2-1A10) via GS linker-mediated IgG-Fc fusion, which provided highly potent protection against all three viruses in female rodents model and positions it as a strong broad-spectrum anti-ebolavirus candidate. Our work demonstrates a structure-guided bispecific nanobody strategy for pan-ebolavirus therapy and highlights compact antibodies for next-generation antivirals.