March 23 (UPI) -- A non-hormonal male contraceptive prevents pregnancy in mice, without obvious side effects, a study presented Wednesday during the American Chemical Society spring meeting in San Diego found.
When given orally to male mice for four weeks, the drug, called YCT529, dramatically reduced sperm counts and was 99% effective in preventing pregnancy, the data showed.
The mice used in the experiments could father pups again four to six weeks after they stopped receiving the drug, the researchers said.
"Scientists have been trying for decades to develop an effective male oral contraceptive, but there are still no approved pills on the market," Md Abdullah Al Noman, a co-author of the study, said in a press release.
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"We wanted to develop a non-hormonal male contraceptive to avoid these side effects," said Noman, a graduate student at the University of Minnesota in Minneapolis.
Men have only two effective options for birth control: male condoms and vasectomy, according to the Male Contraceptive Initiative.
However, condoms are single-use only and prone to failure while vasectomy -- a surgical procedure -- is considered permanent, the organization says.
Although vasectomies can be reversed, the reversal procedure is expensive and not always successful, it says.
As part of research efforts to develop an oral contraceptive for men that is similar to the birth control pill for women, drugs currently being evaluated are designed to target the male sex hormone testosterone.
These pills can cause side effects such as weight gain, depression and increased low-density lipoprotein, or LDL, cholesterol levels, according to Norman and his colleagues.
To develop their non-hormonal male contraceptive, the University of Minnesota researchers led by Gunda Georg targeted a protein called the retinoic acid receptor alpha.
This protein binds to a form of vitamin A that plays important roles in cell growth, including sperm formation, and embryonic development, the researchers said.
Knocking out the protein in male mice, which YCT529 effectively does, makes them sterile, according to the researchers, who plan to begin testing the drug in human clinical trials later this year.
"Because it can be difficult to predict if a compound that looks good in animal studies will also pan out in human trials, we're currently exploring other compounds, as well," Georg, a professor of medicinal chemistry at the University of Minnesota, said in a press release.
