The first clinical trial testing the safety and efficacy of Nestorone (segesterone acetate), a gel formulation of male birth control, has been launched across three sites.
Nestorone, comprised of progestin and testosterone, is a reversible contraceptive for men, absorbed through the skin of the upper arms and shoulders. Its formulation is designed to reduce the production of sperm without impacting the ability to produce sperm later in life.
Regine Sitruk-Ware, co-director of the study and scientist at the population council, told us that the formulation acts on the pituitary gland and blocks the production of the hormone that triggers sperm production while hindering testosterone. “The combination of both acts in concert to stop the production of sperm, while minimizing side effects,” she explained.
When applied to the skin, the gel helps to introduce the dissolved hormones into the skin that work as a “reservoir from which the hormones are diffused through the vessels under the skin,” Sitruk-Ware told us. Through the blood vessels, the drug reaches the circulatory system and is distributed to the whole body.
According to Sitruk-Ware, the shoulders are used as the application site since the skin surface is large enough to receive the 5ml of gel.
The man’s sperm count must reach an appropriate level to prevent pregnancy, which takes approximately eight to 16 weeks of use.
The treatment is currently in a Phase IIb trial, sponsored by the National Institute of Child Health and Human Development and run by the organization’s Contraceptive Clinical Trials network – it is the first to test the product for contraceptive efficacy in a female partner. Approximately 400 couples are anticipated to enroll in the trial, with the efficacy being tested for a full year’s course of treatment.
Nestorone is not the first sperm production inhibitor drug candidate to be researched. In 2012, a team at Texas A&M University found that the compound JQ1 successfully inhibited the production of sperm and worked to reduce sperm mobility without affecting hormone levels.
More recently, a study published in American Chemical Society’s Journal of Medicinal Chemistry found an extract that interrupts the passage of sperm cells needed to fertilize an egg. This extract is another reversible contraceptive that does not affect hormone levels.