The long, winding road to a male birth control pill may have just become more direct. Researchers have found a potential lead in a plant extract that African warriors once used to make lethal poison-tipped arrows, according to CBS Boston.
The extract is called ouabain, and it inhibits sodium and calcium ions from a membrane protein known as Na,K-ATPases. Crucially, the protein also affects fertility in male mice. It's been shown to dampen fertility in male humans, but the catch is the risk of heart damage, which is why it's never been suitable for a male birth control pill before. But by tinkering with ouabain's chemical elements, including removing a key sugar group, a team of researchers from the University of Minnesota and the University of Kansas have now designed an analog—a safe knock-off—that's much likelier to bind to protein in sperm than to anything involving heart tissue.
The new and improved ouabain was shown to successfully target sperm-cell proteins in rats, effectively hamstringing their ability to swim, so they couldn't reach and fertilize an egg. No rats were poisoned in the making of this drug; their tiny hearts exhibited no signs of toxicity. This method of contraception would be reversible, too, so once human men taking it stopped doing so their fertility would revert to its natural state. A paper describing the research was published in the Journal of Medicinal Chemistry.
The quest for male contraceptive methods comparable to those commonly used by women has seen promising results before, but nothing has ever managed to cross the finish line. Most memorably, news arrived in October 2016 that a clinical trial that appeared to be on track was called off after the men complained of side effects, according to NPR. Despite widespread rumors that they ruined the study because they couldn't withstand the same conditions women could, the research wasn't "abandoned," according to Snopes. But it was true that the trial was shut down early, and it's been some time since the field has seen a breakthrough like this one.
"There's a little bit of a different risk-benefit analysis when it comes to men using a contraceptive," NPR science correspondent Rob Stein said in November 2016. "When women use a contraceptive, they're balancing the risks of the drug against the risks of getting pregnant. And pregnancy itself carries risks. But these are healthy men — they're not going to suffer any risks if they get somebody else pregnant."
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