A contraceptive pill for men has come a step closer to development.
Taken daily like the female Pill, it switches off a man’s testosterone and the hormones that cause sperm production.
This should bring the sperm count low enough so that a man cannot get his partner pregnant.
Researchers who gave the tablet to men for a month said it did not cause the liver damage – a side effect shown in previous trials of oral hormonal contraceptives.
Past attempts to give men contraception have focused on injections or gels, but experts say men may find it easier to take a pill.
While there is a fear men may forget to take the tablets, researchers hope this can be addressed by a longer-lasting ingredient that means they can be taken daily rather than twice a day as with previous versions.
A 2011 survey found half of women would not rely on a male pill because they did not trust their partners to remember to take it.
A team led by the University of Washington has trialled the male pill on 83 men aged 18 to 50, who suffered no physical side effects beyond mild weight gain and acne.
After a month, men showed significant declines in their testosterone and gonadotropins – the hormones needed to make sperm.
Co-author Dr Arthi Thirumalai said: ‘It is quite old-fashioned to think that men would forget to take a pill and survey data shows that men want to take responsibility for contraception in couples. This study showed that the pill we have developed worked safely and efficiently at blocking men’s testosterone and gonadotropin production, while avoiding problems in the liver.
‘It is exciting to see a single oral agent achieve such notable effects. Further studies are needed to see if this translates into blocking sperm production as well.’ The female pill became available in 1961, and scientists have been trying for more than 30 years to develop a male version.
This new pill, which has to be taken with food, blocks receptors in the brain to shut off hormones required for sperm production.
The next step is to look at whether sperm count is affected in men who take the pill for at least three months. This study’s major result is to show the pill is safe, with all the men passing safety tests including on liver and kidney function.
The findings of the study, carried out with the Harbor-UCLA Medical Centre, were presented at ENDO 2018, the Endocrine Society’s annual meeting in Chicago. Dr Kevin McEleny, of the British Fertility Society, said the research was interesting, but added: ‘The study is short term and really only looks at a few potential outcomes. It doesn’t actually look at semen quality.’