MP0423

**MP0423** is a tri-specific DARPin (Designed Ankyrin Repeat Protein) antiviral therapeutic candidate originally developed by Molecular Partners for the prevention and treatment of COVID-19. Unlike ensovibep (MP0420), which binds three distinct epitopes within the receptor-binding domain (RBD) of the SARS-CoV-2 spike protein, MP0423 is engineered with three DARPin domains that simultaneously target three different domains of the spike protein: the RBD, the N-terminal domain (NTD), and the S2 domain. This tripartite binding configuration is designed to maintain potent neutralization, even if one domain loses binding due to viral mutation, thereby reducing the likelihood of viral escape. Preclinical studies demonstrated that MP0423 maintains neutralizing activity against multiple SARS-CoV-2 variants, although with some loss of potency against certain strains, such as the UK variant, while remaining in the therapeutic range. Clinical development for MP0423 is less advanced compared to MP0420, with the molecule not progressing beyond early clinical and preclinical phases before being discontinued[1][2][3][7][9][10][11][12].