Homing peptides: targeting drugs to the placenta

Natalie Cureton, Anna King, Frances Beards, Dr Karen Forbes, Professor Nicola Tirelli, Professor John Aplin, Dr Lynda Harris

Drugs which could help prevent pregnancy complications can’t reach the placenta effectively. Tommy’s researchers are making use of ‘homing peptides’ to deliver drugs directly to the placenta. This work could help to prevent pregnancy complications and stillbirth.

Start: October 2017

End: September 2020

Why do we need this research?

We already have drugs which lab experiments have shown can improve how the placenta works. However, at the moment there is no way of safely getting these to the placenta in pregnant women. This is because drugs circulate in the blood throughout the whole body, meaning that drugs become diluted and can cause unwanted side effects.

This means that we can’t treat complications like fetal growth restriction, even though we have drugs which might help. We therefore need to find ways to deliver drugs directly to the placenta.

Homing peptides deliver drugs to where they’re needed

Researchers funded by Tommy’s have developed a way to target drugs straight to the placenta, so that there is no risk of harm to the unborn child.

Every organ in the body has a unique combination of molecules on its surface – a molecular ‘postcode’. By studying the postcode of the placenta, they have created molecules called ‘homing peptides’, which home and bind to the surface of the placenta or the blood vessels in the womb.

What’s happening in this project?

Our researchers are now using these homing peptides to create a targeted drug delivery system. They have made tiny hollow particles called liposomes which drugs can be packaged into. These liposomes are coated with homing peptides. When they’re injected into the body, they build up in the placenta or the womb, only releasing their drug cargo where it is needed.

So far, the researchers have tested the liposomes in mice, and have already found that they deliver the drug to the placenta without it being transferred to the unborn pups. Delivering drugs in this way improved both the blood flow within the womb and the growth of the placenta. The team also have shown that neither the liposomes nor the peptides have any negative effect on the placenta. This shows that their system could be safe to use in humans.

The team are now continuing their work, packaging up different drugs into their particles to see whether it can deliver drugs efficiently to the womb and placenta. The drugs all aim to improve blood flow in the placenta. Some of this research will be done with mice, and other experiments will be done using samples of placenta donated by women.

 What difference will this project make?

Through these studies, our researchers are developing targeted drug delivery systems which can be used in pregnant women. Ultimately, their work will make sure that drugs can be safely given to women to improve the health of the placenta, and potentially help to prevent premature birth or stillbirth

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