Scientists are working on a contraception that will stop sperm on its way

The precision targeting of monoclonal antibodies is being used by researchers at the University of North Carolina at Chapel Hill to develop a novel type of female contraception.

Monoclonal antibodies are used to treat and prevent everything from cancer to COVID-19 because of their capacity to fight against invading bacteria. Antibodies are now being considered for a new mission: immobilizing sperm before it reaches an egg.

Carolina researchers created ultra-potent antibodies that efficiently caught and inhibited more than 99.9% of human sperm in animal testing. According to the encouraging study findings published in Science Translational Medicine, antibody-based contraceptives may provide women a non-hormonal option for preventing pregnancy.

"Many women forgo hormonal contraception because of real and perceived side effects," said Samuel Lai, professor in the UNC Eshelman School of Pharmacy's Division of Pharmacoengineering and Molecular Pharmaceutics.

Intermittent bleeding, nausea, depression, weight gain, and migraines are some of the side effects. Hormonal contraception based on estrogen can also be dangerous to some women.

"There is a significant unmet need for non-hormonal contraception for women," Lai said.

Nearly half of all pregnancies in the United States are unwanted, and Lai is one of many scientists throughout the country who are pushing for anti-sperm antibodies to be used as contraception.

"Infertility that occurs in some women who develop antibodies against their partner's sperm inspired us," said study first author Bhawana Shrestha, a doctoral student in the UNC School of Medicine's Department of Microbiology and Immunology and a graduate research assistant at the school of pharmacy.

They're investigating an antibody that targets a specific surface antigen found on human sperm and was obtained from an infertile woman. When it's mixed with sperm, it instantly clumps them together.

"We created antibodies that were more than 10 to 16 times more effective in agglutinating sperm and reducing sperm penetration through mucus than the best-known antibody using our highly multivalent IgG platform," she added.

Antibodies were studied in sheep, which have reproductive processes that are similar to human females. Both naturally occurring antibodies and newly created antibodies efficiently stopped all human sperm motility at a high dose of 333 micrograms of antibody, while the modified antibodies, but not the original antibodies, trapped 97 percent to 99 percent of sperm at a modest dose of 33.3 micrograms.

However, monoclonal antibodies are known to be expensive medications, therefore their utility as a low-cost contraception is debatable.

Researchers anticipate that by enhancing the effectiveness of the multivalent antibodies, substantially smaller doses of the antibodies may be required for effective contraception.

"We believe that these second-generation compounds would not only deliver increased efficacy, but also lower prices, making the method cost-effective," Lai added.

The molecule has been licensed for development of an antibody-based contraception by Mucommune, a firm formed out of the Lai Lab. To prepare for human clinical trials, the company will focus on safety and manufacturing. These studies might begin in 2023.

The researchers are working on putting the antibodies into an intravaginal ring that distributes antibodies gradually, or a dissolvable film that is implanted in the vagina and spreads antibodies prior to intercourse.

"We believe the antibodies created here could address the contraceptive needs of millions of women, assist to minimize the number of unintended births, and alleviate the health care expenses of unexpected pregnancies, which some estimate to be in excess of $20 billion a year," Lai said.