Men are less likely than women to take a birth control pill with side effects, so scientists have created one without them.
When it comes to birth control for men, there is currently the option of single-use condoms or the permanent option of a vasectomy – but that may soon change.
Scientists in the United States this week have reported a non-hormonal male contraceptive pill that has proven 99 per cent effective in mice with no side effects, and is expected to now be used in human clinical trials in the second half of this year.
While the US Food and Drug Administration will first need to give permission for human clinical trials to go ahead, the scientists from the University of Minnesota hope that if all things go to plan the pill could be available for public use in five years.
A non-hormonal male birth control pill may not be far away.
They note that as women currently have many more choices for birth control, ranging from pills to patches to IUDs, partly as a result, they bear most of the burden of preventing pregnancy.
“Scientists have been trying for decades to develop an effective male oral contraceptive, but there are still no approved pills on the market,” said Md Abdullah Al Noman, who presented the findings at an American Chemical Society meeting this week.
Male condoms are only effective with perfect use, so the pill would give another option.
He said most attempts to create a male birth control pill had been made by targeting the male sex hormone, testosterone, because most female birth pills worked on the female sex hormones, oestrogen and progesterone.
“Targeting the male sex hormone leads to a lot of side effects such as weight gain and depression and increased risk of cardiovascular diseases, and since men don’t have to trade up between the pregnancy and the side effects, men are less willing to take a birth control pill with significant side effects,” he explained at the meeting.
“That’s why we are targeting a non-hormonal pathway to develop a male birth control pill.”
Men are less likely to take a birth control pill with side effects than women, so scientists worked to find a non-hormonal option.
The researchers targeted a protein called the retinoic acid receptor alpha (RAR-α).
The protein is one of a family of three nuclear receptors that bind retinoic acid, a form of vitamin A that plays important roles in cell growth, differentiation (including sperm formation) and embryonic development.
They found that knocking out the RAR-α gene in male mice made them sterile, without any obvious side effects.
Male mice were given the contraceptive drug – named YCT529 – every day while together with female mice and the scientists observed how many pregnancies occurred.
There was a 99 per cent efficacy after the mice were on the drug for four weeks.
“That’s similar to the efficacy that you see in the female birth control pill,” Professor Gunda Georg said.
“Of course you have to be careful with this analysis; these are mice and they’re not humans but nevertheless the effect was very very promising.”
It took two to four weeks for the male mice to become completely fertile again after taking the drug.