New York, United States

Researchers on Sunday (June 2) presented the promising phase 2 trial results from an ongoing study of a new male hormonal contraceptive gel at ENDO 2024, the Endocrine Society’s annual conference in Boston.

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The male contraceptive gel combining two hormones, segesterone acetate (named Nestorone) and testosterone, suppresses sperm production faster than similar experimental hormone-based methods for male birth control, the ongoing multicenter phase 2b clinical trial found. 

The study, funded by NIH’s Eunice Kennedy Shriver National Institute of Child Health and Human Development, involved 222 men, aged 18 to 50, who applied 5 ml of the gel (about a teaspoon) to each of their shoulder blades once per day.

“The development of a safe, highly effective and reliably reversible contraceptive method for men is an unmet need,” said senior researcher Diana Blithe, chief of the Contraceptive Development Program at the National Institutes of Health (NIH).

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“While studies have shown that some hormonal agents may be effective for male contraception, the slow onset of spermatogenic suppression is a limitation,” Blithe added. 

Initial findings of the trial on the new birth control gel have shown that the contraceptive worked faster than expected, according to Blithe.

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Early in the study, the researchers measured for suppression of sperm production by obtaining sperm count tests at 4-week intervals, which is a good predictor of fertility. If the sperm counts remain low, the chances of pregnancy are considered slim.

The second part of the two-part trial is still underway. 

Key findings of the trial

After 12 weeks of applying the gel every day, 86% of trial participants achieved effective sperm suppression, implying they had only up to 1 million sperms per ml of semen, the amount deemed effective for contraception by researchers. 

In comparison, normal sperm counts without contraception can range from 15 million to 200 million per millilitre.

Among the participants, the timing for effective contraception was eight weeks on average. 

Whereas prior studies of male hormonal contraceptives given by injections showed a median time between 9 and 15 weeks for sperm output to become suppressed, Blithe stated. 

According to her, the faster-than-expected timing to suppress sperm count is an encouraging sign, especially since past attempts have taken longer to reach these sperm levels.

Prior efforts using testosterone alone had a higher median time and required higher doses of the hormone, which can cause side effects. Because the gel includes both testosterone and Nestorone, so it acts more quickly and requires less testosterone, she said. 

In the daily segesterone-testosterone gel regimen, blood levels of testosterone are kept in the physiologic range to maintain normal sexual function and other androgen-dependent activities.

The sperm suppression stage of the international phase 2b trial of segesterone-testosterone gel is complete. The study continues to test the contraceptive’s effectiveness, safety, acceptability and reversibility of contraception after treatment stops.

Even after decades of early-stage attempts and failures, there are no federally approved male birth control drugs. In fact, only a handful have advanced into human trials.

Researchers blame the lack of enough funding or financial investment to complete expensive advanced human trials for the dearth of male hormonal contraceptives.

(With inputs from agencies)