How antibodies enter the cell fluid: methods and design to escape from cell compartments

Cytosol-penetrating immunoglobulin G (IgG) antibodies face significant challenges in reaching the cytosol due to inefficient endosomal escape.

• Inefficient endosomal escape is primarily caused by the difficulty of large hydrophilic molecules passing through hydrophobic endosomal membranes.
• Current strategies for cytosolic delivery include both passive and active methods, with a focus on rational engineering to improve antibody design.
• A proposed mechanistic framework identifies distinct energy barriers in the process of endosomal escape, which include receptor dissociation and membrane translocation.
• The framework highlights actionable design principles to enhance the effectiveness of cytosol-penetrating antibodies.
• Considerations for developing these antibodies include receptor selection, potential immunogenicity, and methods for quantitatively assessing delivery efficiency.

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