A promising vaginal lube contraceptive works by engineering mucus instead of killing sperm

Tapping into cervical mucus' natural capacity

The gel comprises chitosan- a biopolymer produced from fungi or crab shells. Chitosan works by creating cross-links with proteins released in cervical mucus. As a result, the mucus is thickened, preventing sperm from passing the cervix and entering the fallopian tubes, where egg fertilization occurs.

The scientists applied the gel using a syringe applicator toward the backs of the sheep vaginas. According to the researchers, these are comparable to human vaginas. After an hour, they artificially inseminated each of the eight lambs with 1 billion sperm.

It was discovered that the gel had migrated into the cervix's opening and throughout the vagina. Just two of the 1 billion swimming sperm could pass the cervix of one of the sheep in the study, proving that it created an effective barrier- 98 percent, to be exact.

By comparison, birth control pills are recognized to be between 91 and 99 percent effective.

Engineering mucus instead of killing sperm cells

Thomas Crouzier, a biopolymers researcher at KTH, said in a press release that the results demonstrate the potential of an unprecedented approach to preventing unwanted pregnancies. I.e., one that blocks sperm by engineering mucus rather than killing sperm cells as spermicides do.

Better yet, the chitosan gel didn't inflame the vaginal walls like chemical spermicides, another non-hormonal birth control method, do. This could mean the gel will be less of an annoyance.

“Vaginal gels like this can be applied in seconds,” Crouzier says. “We imagine that a product like this should be usable from seconds to a few hours before sexual intercourse. The effect could last for hours, but diminish over time as the mucus barrier is replaced naturally.”

Full sperm blockage in humans

Significantly, laboratory tests utilizing human cervical mucus and sperm revealed that the chitosan gel had a similar impact. It swiftly strengthened the mucus barrier, reducing sperm penetration after one minute of exposure and full sperm blockage after five minutes.

According to studies cited by Crouzier, about 50 percent of women believe their contraceptives must be hormone-free. Thankfully, this study provides a clear step forwards in 'topically' achieving that.

Crouzier founded a company called Cirque Biomedical and has since entered a $360 million partnership with the women’s health company, Organon, with the aim to develop and commercialize the new gel.

The full study was published here.

Abstract:

Close to half of the world's pregnancies are still unplanned, reflecting a clear unmet need in contraception. Ideally, a contraceptive would provide the high efficacy of hormonal treatments, without systemic side effects. Here, we studied topical reinforcement of the cervical mucus by chitosan mucoadhesive polymers as a form of female contraceptive. Chitosans larger than 7 kDa effectively cross-linked human ovulatory cervical mucus to prevent sperm penetration in vitro. We then demonstrated in vivo using the ewe as a model that vaginal gels containing chitosan could stop ram sperm at the entrance of the cervical canal and prevent them from reaching the uterus, whereas the same gels without chitosan did not substantially limit sperm migration. Chitosan did not affect sperm motility in vitro or in vivo, suggesting reinforcement of the mucus physical barrier as the primary mechanism of action. The chitosan formulations did not damage or irritate the ewe vaginal epithelium, in contrast to nonoxynol-9 spermicide. The demonstration that cervical mucus can be reinforced topically to create an effective barrier to sperm may therefore form the technological basis for muco-cervical barrier contraceptives with the potential to become an alternative to hormonal contraceptives.