The era of highly effective male birth control is just on the horizon, and it’s likely to be one with several options to choose from. Scientists reported this week that they have found another potential way to safely and temporarily knock out a man’s fertility.
Cornell University researchers detailed their discovery in a study published Tuesday in the journal PNAS. In experiments with male mice, they showed that it’s possible for a drug to momentarily block fertility by interfering with the process of meiosis, a critical aspect of producing viable sperm cells. Such treatments could eventually provide a non-hormonal yet long-lasting form of male birth control, the researchers say.
“While acknowledging the need for robust future safety assessments of any candidate drugs, these studies provide a blueprint for developing new contraceptive approaches,” they wrote in their paper.
The meiosis blocker
A healthy embryo has 46 chromosomes arranged in pairs, with each half of the pair provided by a mature sperm and egg cell. For these cells to have 23 chromosomes, they first have to undergo meiosis. In the first phase of meiosis, a precursor stem cell (sperm or egg) with two sets of 23 chromosomes divides into two cells that only contain one set. The second phase of meiosis creates two more copies of these single-set cells, resulting in four of these cells from a precursor (in females, only one of these cells will actually become a viable egg).
Women produce a limited supply of eggs, and these cells undergo the earliest stages of meiosis before women are even born, but this isn’t true for men. Their stem cells start meiosis during puberty, and new sperm are continually produced from these single-set cells throughout life. That leaves open an opportunity for male contraceptives to block this process, according to the study researchers.
They decided to test their hypothesis with a drug known as JQ1. This drug was originally developed as a cancer treatment, and it’s known to kill cells in the earliest stage of meiosis. It does so by inhibiting a protein specific to the testes called BRDT.
They dosed male mice with JQ1 for three weeks, then tracked their fertility over time. During treatment, they found that the drug completely halted the mice’s sperm production without harming stem cells pre-meiosis. This effect began to fade within six weeks after the mice stopped the drug, but it took roughly 30 weeks for the mice’s reproductive health to fully recover. Once that happened, though, the mice were still able to produce offspring.
“It shows that we recover complete meiosis, complete sperm function, and more importantly, that the offspring are completely normal,” said study author Paula Cohen, director of the Cornell Reproductive Sciences Center, in a statement from the university.
The future of male birth control
The team’s research is only intended as a proof of concept. JQ1 itself will likely never be developed as male birth control or any other kind of approved drug due to its short half-life and possible neurological side effects. But the results do point to another viable method of male contraception outside of vasectomies or condoms. And the study authors are already working on other potential treatments intended to safely block sperm meiosis.
There are several other male contraceptives that are further along in development, including treatments being tested in late-stage clinical trials. But as with female birth control, it’ll be important to have a variety of options available, especially since some men might not respond well to or want the hormonal treatments that are closest to being approved in the near future.
With any luck, plenty of these drugs or interventions will be on the market within the next decade or so.
