A male birth control pill has been found to be safe in early-stage clinical trials without any negative side effects, researchers have said.
The new hormone-free pill, which aims to decrease sperm count reversibly, was found to be safe in a trial of 16 male volunteers.
For decades, the choice of contraception for men has been limited to condoms and vasectomy.
Weight gain, acne, mood changes and changes in libido were some of the side effects of previous attempts to create a male contraceptive pill.
However, women have several contraceptive options, including the pill, implant and intrauterine device (IUD) - many of which also come with unappealing side effects.
But because this new male pill does not use hormones, it gives hope for fewer negative side effects in comparison to prior attempts, the early-stage research published in Communications Medicine reveals.
The researchers, scientists at drug development company YourChoice Therapeutics, said: “Since nearly half of all pregnancies in the US and worldwide are unintended, there is a critical need for additional contraceptive options for men and women.”
The new drug uses a chemical known as YCT-529, which works by blocking vitamin A metabolites from binding to receptors in the testes, preventing sperm from being produced.
Professor Alan Pacey, an andrologist at the University of Manchester, who was not part of the study, told BBC Radio 4’s Today programme: "This molecule targets a compound which is related to vitamin A, retinoic acid, and we have known for a long time that this compound is important in how sperm are produced in the testis, making it the perfect target for a male contraceptive pill.
“It is able to inhibit that process without altering the sex hormones, which give men a sex drive.”
Previous animal studies have found that using the chemical can create reversible infertility without side effects.
In the recent trial, 16 male volunteers aged between 32 and 59 took the drug twice in increasing doses – 10mg, 30mg, 90mg and 180mg – while some took the placebo for comparison.
Participants were monitored for 15 days to assess side-effect and hormone levels.
The study authors concluded: “Administration of single oral doses of 10–180 mg YCT-529, fasted, and 30 mg, fed, is well tolerated by healthy male subjects.
“YCT-529 does not demonstrate an adverse cardiac safety profile, or change in haematology, coagulation or serum chemistry parameters, hormone or proinflammatory cytokine levels, sexual drive and mood, and shows good bioavailability (with no clear food effect).”
Speaking on the Today programme, Dr Pacey described the findings as an “exciting step forward” but highlighted the drug has not been tested in a real-world setting to find whether it actually leads to fewer babies.
He added: “It takes three months to produce sperm from start to finish and so if you were to start taking any pill, not just this one, you would need to have the sperm that are currently on the production line to be moved from the system. So, there will be a lag between starting to take the pill and it having its full contraceptive effects.”
However, he explained that one of the biggest challenges will be the cost of bringing the new pill to market.
