Mirror-Image <i>D</i>-Core Streptavidin Exhibits Reduced Immunogenicity and Comparable Biodistribution to Natural Core Streptavidin in Mice

The clinical application of natural core streptavidin remains unrealized owing to its immunogenicity and interference from endogenous D-biotin. These limitations could be addressed using D-core streptavidin, the mirror-image form. Here, we evaluated the immunogenicity and biodistribution of D-core streptavidin in mice. Intraperitoneal administration of natural core streptavidin induced antibodies against streptavidin, whereas no antibody production was observed for D-core streptavidin. The protease assay indicated that proteolysis by cathepsin B differed between D-core streptavidin and the natural core form. The difference in degradation by cathepsin B in non-denatured conditions may contribute to the reduced immunogenicity of D-core streptavidin. Biodistribution studies revealed no significant differences between D-core and natural core streptavidins in tumor-bearing mice. These findings support the further development of D-core streptavidin in combination with L-biotin for in vivo applications.