“Male pill” discovered in mice experiments
A molecule originally being tested for its anti-cancer properties could be used to control male fertility tests in mice show. Male mice given the pill were rendered completely infertile during treatment as they produced fewer and less mobile sperm without any noticeable side-effects.
The researchers behind the study found the molecule while screening hundreds of compounds in the hope of finding one that blocked cancer-causing genes. However, they discovered that one of their candidates, called JQ1, appeared to target a protein specific to the testes called BRDT that instructs sperm to mature. The finding was surprising because few drugs are able to cross the protective blood-testes barrier that protects the testicles from substances floating around in the blood stream.
Male mice produced fewer sperm when given JQ1, and the ones they did produce were poor swimmers. Crucially, hormone levels were unaffected and the effects were completely reversible. Hormone imbalance is a major cause of side-effects for contraceptive medicines.
There is still no licensed contraceptive pill for men and those currently in development work by altering hormone levels such as testosterone. The strong similarity between sperm production in mice and humans suggest that a variation of JQ1 may ultimately result in a human contraception for men. The next step will be to refine the molecule so that it only acts on cells in the testes, and not on cancer cells or other tissues.