“The study, in Phase 2b trials, included 222 men who completed at least three weeks of daily treatment with a gel made from the progestin medication segesterone acetate and testosterone. The compound was developed by the Population Council, a nonprofit organization that focuses on reproductive health, in collaboration with the National Institutes of Health.

In the trial, researchers conducted sperm count tests every four weeks to evaluate suppression of sperm. They aimed for a sperm count of 1 million or fewer per milliliter for effective contraception. Normal sperm count is between 15 million and 200 million sperm per milliliter of semen. By Week 15, 86 percent of participants achieved the low threshold, with sperm production typically suppressed by the eighth week of treatment.”

From Washington Post.