Many powerful biologic drugs are antibodies — and a quirk of biology means they readily cross the placenta, raising safety questions for pregnant patients. Researchers now report a design tweak that sharply reduces that transfer.
Scientists at the University of Oslo and Oslo University Hospital, led by Jan Terje Andersen, found that fusing IgG antibodies to albumin significantly reduces their transport across the placenta while keeping the drugs’ long-lasting effectiveness. The findings appeared in Science Immunology.
Exploiting a receptor
The placenta uses a receptor called FcRn to ferry IgG antibodies to the fetus, while largely leaving albumin behind. By combining the two proteins, the researchers created biologics that sidestep that transport route — minimizing fetal exposure. In mouse studies and ex vivo human placental tissue, and in a test model of fetal/neonatal alloimmune thrombocytopenia, the approach substantially reduced fetal exposure and adverse effects.
Why it matters
Monoclonal antibodies treat many chronic conditions common in women of reproductive age — cancer, autoimmune diseases and migraine among them — yet standard versions actively cross the placenta. “We now have the opportunity to develop a new generation of biologic medicines that combine long-lasting efficacy with improved safety during pregnancy,” the researchers said. The work is preclinical, but points to a practical way to make existing drug classes safer to use in pregnancy. This article summarizes early research and is not medical advice.