Researchers in Sweden have identified a new antibody-based approach to block fertilisation in mice, paving the way for a non-hormonal contraceptive with fewer side effects.

Most current human contraceptives rely on hormones, which can cause mild to severe side effects, therefore an alternative strategy is to try and prevent fertilisation directly by blocking the interaction between sperm and egg.

In a new study, led by EARA member the Karolinska Institute, researchers developed a smaller fragment of the IE-3 antibody – previously known to prevent in vitro fertilisation (IVF). This fragment was just as effective at blocking sperm-egg interaction in mice, while offering greater potential than the full antibody as it would mean a lower risk of triggering any immune reactions.

“Our study shows how a small antibody fragment can block fertilisation by targeting ZP2, a key protein in the outer layer of the egg that is involved in both sperm binding and blocking polyspermy,” said Luca Jovine, senior author of the study published in the Proceedings of the National Academy of Sciences.

The team is now working on a similar antibody fragment that targets the human version of ZP2, with plans to test its effectiveness in IVF with human sperm and eggs.