一词日历：男性避孕药出来了

For years, scientists have been trying to develop a safe and effective version of the pill for men, and a new drug candidate could be the contraceptive we've been looking for.

Now, scientists in the US announced that an experimental oral drug called 11-beta-MNTDC looks to be safe and tolerable, based on results from a phase 1 clinical trial involving 40 men.

"Our results suggest that this pill, which combines two hormonal activities in one, will decrease sperm production while preserving libido," says male reproduction biologist Christina Wang from the Los Angeles Biomedical Research Institute (LA BioMed).

In the clinical trial, Wang and her team recruited 40 healthy men.

For 28 days, 30 of these participants took a low or higher daily dose of the 11-beta-MNTDC, while the remaining 10 men took a placebo.

11-beta-MNTDC is a modified form of testosterone with both progestational (in effect, sperm-blocking) and androgenic (hormone-balancing) characteristics.

"Since testosterone production is shut down in the testes, the androgen action in the rest of the body maintains 'maleness' elsewhere, supporting things like male pattern hair, deep voice, sex drive and function, and lean body mass," explained one of the team, endocrinologist Stephanie Page from the University of Washington. 

In the first clinical trial results on the drug, that balancing act looks like it might deliver a safe oral drug while hypothetically stopping sperm production – although it has to be emphasised this is only preliminary data.