A new male contraceptive pill tested on British men in a world first is safe for use, a study has suggested.
Oral female contraceptive tablets have been available for 60 years but there has never been an authorised male version.
Female tablets work by altering hormone levels to reduce the risk of conception but this approach has proven difficult in men because of severe side effects such as infertility and mood swings. These side effects are common in female versions.
A third of men say they would take a contraceptive pill if one was available to them.
YourChoice Therapeutics has developed the first non-hormonal contraceptive for men. It works by blocking the production of a protein, which is needed to produce sperm, and does not meddle with hormones.
The drug stops production of retinoic acid receptor alpha (RAR-alpha) in the body and this prevents it binding to vitamin A compounds and subsequently prevents sperm production.
Animal studies showed this mechanism to be 99 per cent effective and also found that sperm levels returned to normal after the medication was stopped, showing the contraceptive to be temporary and reversible.
Human trials began in 2023 when 16 healthy men who had already had a vasectomy were recruited to test the safety of the drug in people.
Data, published this week, show it to be safe and well-tolerated with no clinically relevant side effects in a significant step forward for the prospects of the drug, known as YCT-529.
The trial of 16 British men gave participants either the tablet or a placebo and conducted analysis on the participants to measure their blood, urine, mood and overall health.
Four different dosages were tested and all were found to be well-tolerated. The highest dose was the same as what was shown to be effective as a contraceptive in animal trials.
‘Positive results’
There was no reduction in testosterone levels, sex drive or any other hormonal imbalance, the scientists found.
“The positive results from this first clinical trial laid the groundwork for a second trial, where men receive YCT-529 for 28 days and 90 days, to study safety and changes in sperm parameters,” the study authors wrote in their peer-reviewed study in the journal Communications Medicine.
Further trials will now gather more data on the long-term safety profile of the drugs and if this is found to be acceptable, the next stage of clinical trials will begin to determine its precise effectiveness in humans.
The data are needed before regulators can make a decision on whether a drug is safe and effective enough to be approved for human use.
The study authors add that the safety bar for contraceptives is much higher and harder to reach than it is for drugs designed to cure or treat a disease because it is preventative and used by healthy people daily for a long period of time.
‘More attractive to men’
Akash Bakshi, a co-founder and the chief executive of YourChoice, has previously suggested that the medicine, if approved, could be sent out alongside at-home testing kits for men to check their sperm levels are too low to cause pregnancy.
He said: “YCT-529 blocks a protein – not hormones – to prevent sperm production. We believe this will be more attractive to men, most of whom view pregnancy prevention as a shared responsibility even despite today’s limited contraceptive options, which are permanent or only moderately effective.
“The dearth of options reinforces the centuries-old view that pregnancy prevention is ‘a woman’s responsibility’. It’s not, and we’re committed to advancing the first hormone-free birth control pill for men that’s effective, convenient and temporary.”
While non-hormonal male contraceptives are in trials and at the early stage of development and testing, other hormone-powered alternatives are also in the works.
A gel containing Nestorone (segesterone acetate) and testosterone lowers sperm counts in around eight weeks and is in testing on more than 200 men in the US.
The gel is rubbed into the shoulders or shoulder blades because it is easy to reach for the user and it is also unlikely a child or woman would come into direct contact with the gel in this location.
The hormones soak into the skin and are absorbed by the bloodstream. But accidental exposure to the gel could cause premature puberty in children and acne or excessive hair growth in women.