ChAd63-MVA Pfs25-IMX313

**ChAd63-MVA Pfs25-IMX313** is a heterologous prime-boost viral vector vaccine regimen against malaria transmission, consisting of a chimpanzee adenovirus serotype 63 (ChAd63) prime encoding Pfs25-IMX313 followed by a modified vaccinia Ankara (MVA) boost encoding the same antigen. Pfs25 is a leading sexual-stage antigen of *Plasmodium falciparum* expressed in the mosquito midgut, targeted by transmission-blocking vaccines (TBVs) to interrupt parasite development and prevent malaria transmission. The IMX313 molecular adjuvant fuses to Pfs25 to form heptameric nanoparticles, enhancing immunogenicity, antibody titers, germinal center responses, and transmission-reducing activity (TRA) compared to monomeric Pfs25 in preclinical mouse models using standard membrane feeding assays (SMFA). Developed by the Jenner Institute at the University of Oxford, it was evaluated in a Phase Ia open-label dose-escalation trial (NCT02532049, VAC062) in 26 healthy malaria-naive UK adults via intramuscular administration at an 8-week interval, demonstrating a favorable safety profile similar to prior ChAd63/MVA vaccines, with induced anti-Pfs25 antibodies, B cell, and T cell responses, though significant TRA was not observed in most participants by SMFA, suggesting need for optimized formulations.[1][2][3][5][6]

Other names

ChAd Pfs25-IMX313