The Population Council is enrolling 420 couples to test NES/T, which is the progestin compound segesterone acetate (Nestorone) in combination with testosterone.

Men have somewhat limited options for birth control compared to women; condoms are effective, as is vasectomy, but the latter is surgery and can be difficult to reverse. Over half of men would use a product like a birth control pill if it were similarly reversible and uncomplicated. But to-date none have been successful, including other combinations of hormones. 

"Expanding male contraceptive options could help make family planning more of a shared responsibility between women and men,” said Regine Sitruk-Ware of the Population Council, co-director of the trial. “Safe, effective, and reversible tools for men to control their own fertility gives new meaning and significance to the term ‘family planning.’"

The Population Council, founded by John D. Rockefeller III (a eugenicist who wanted "weak" people out of the gene pool - American Eugenics Society members Frederick Osborn and Frank Notestein succeeded him as the Council’s next two presidents) has a long history of funding birth control for women, not without controversy; they developed the Norplant, which resulted in a $50 million settlement for a class-action lawsuit brought by 30,000 women who suffered severe side effects from the implant device, and they were also behind the abortion pill known as RU-486.  Their fourth president even advocated sterilization drugs in water, which the history of eugenics shows would really have meant the water of poor people and minorities.

Clearly this is a far less Draconian approach than they have advocated in the past. Men will apply the gel daily for up to 12 weeks to find any unacceptable side effects. If sperm levels have not adequately declined by the 12-week mark, the men will continue to use the formulation for up to 16 weeks. If sperm levels decline enough for the gel to be considered contraception, the men will enter a 52-week trial.

Once the trials are over, researchers expect to monitor the men for an additional 24 weeks after they stop using the gel to make sure it's reversible.

Results from this trial are expected in 2022 and will help determine whether the NES/T gel should be evaluated in a Phase III contraceptive efficacy clinical trial, with the aim of obtaining approval from the U.S. Food and Drug Administration to market the product as a male contraceptive.