Antibody-based medicines are widely used to treat cancers and autoimmune diseases, but their ability to cross the placenta raises safety concerns for fetal development.
A study published in Science Immunology tested whether fusing antibodies with albumin, a abundant blood protein, could restrict this placental transfer.
Researchers engineered antibody-albumin fusion proteins and compared their movement across the placenta with standard antibodies in mouse models.
The fusion proteins showed markedly reduced transfer to the fetal circulation compared with unmodified antibodies.
The effect is attributed to albumin's interaction with the neonatal Fc receptor (FcRn), which alters the trafficking pathway and limits transcytosis across the placental barrier.
The approach preserved the therapeutic activity of the antibodies in the mother while decreasing fetal exposure.
Further research is needed to confirm the findings in human pregnancy and assess long-term outcomes.
The study was led by Jan Terje Nilsen and colleagues, with the findings reported in the 2026 volume of Science Immunology.
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