Scientists at Cornell University have moved closer to a safe, reversible, long‑acting male birth control that does not use hormones.
In a six‑year mouse study, the team showed that blocking a key step in the cell division that makes sperm can pause sperm production without lasting damage.
The results appeared in the journal Proceedings of the National Academy of Sciences on April 7.
Researchers used a tiny chemical called JQ1. It was first made to study cancer and inflammation, but it also stops a stage of sperm‑making called prophase 1. Because JQ1 can affect the brain, it cannot be used as a drug, but it proved that targeting this stage can temporarily shut down sperm.
"We are one of the few groups exploring testis‑based contraception," said Paula Cohen, a genetics professor at Cornell. "Our work shows that normal sperm production returns after treatment, and the babies are healthy."
Why New Options Matter
Today, men mainly rely on condoms or vasectomies. Vasectomies are long‑term and many men feel uneasy about them, even though reversal is sometimes possible. Hormonal methods have safety worries, especially after what was seen in women.
Cohen’s team chose to block meiosis—the step that makes sex cells—rather than later steps. This way, sperm can stop completely and start again later, keeping the testes healthy.
"We avoided harming the stem cells that create sperm, because destroying them would make a man infertile forever," Cohen explained. "We also made sure no mature sperm could slip out and fertilize an egg during treatment."
How JQ1 Works
JQ1 interrupts meiosis at prophase 1, causing developing cells to die and preventing the genes needed for later sperm stages from turning on.
Male mice received JQ1 for three weeks. During this time, they produced no sperm, and the normal chromosome movements of meiosis were disrupted.
When the drug stopped, sperm production began to recover. Within six weeks, most mice had normal meiosis and healthy sperm again. The researchers bred the mice and confirmed that they could father healthy offspring who also reproduced normally.
What Could a Human Version Look Like?
If the method works in people, it might be given as an injection every three months or as a skin patch that releases the drug steadily.