A new type of male contraceptive that does not rely on hormones has shown preliminary success in mice. The new drug is not only reversible; this causes very few side effects.
Human clinical trials are still a long way off, but in early rodent experiments, the right dose of drug at the right time can enter the bloodstream, penetrate the testicles and reduce sperm hyperactivity.
The compound is called CDD-2807 and American researchers led by the Baylor College of Medicine want to continue studying it.
When the team injected CDD-2807 into about a dozen mice daily for 21 days, male mice that received one of the doses did not father any litters. This is despite the fact that males and females still lived together and mated. After the drugs were stopped for about 53 days, the males began fathering offspring again.
By examining the testicles of male mice, researchers found that those given CDD-2907 had lower sperm counts, lower sperm motility, and fewer hyperactivated sperm compared to controls.
“We were pleased to see that the mice showed no signs of toxicity following treatment with CDD-2807, that the compound did not accumulate in the brain, and that the treatment did not change the size of the testes,” explains the pathologist Courtney Sutton.
“Importantly, the contraceptive effect was reversible. After a period without the CDD-2807 compound, the mice recovered motility and sperm count and were fertile again.”
Researchers discovered the sperm-slowing activity of CDD-2807 in a library of possible drugs. It is distinguished by its ability to inhibit a protein called serine/threonine kinase 33 (STK33), enriched in the testes of mammals.
In mice and in humans without STK33 gene, which encodes the STK33 protein, studies have shown that sperm abnormalities occur and lead to infertility, although there do not appear to be any other health problems associated with this variant.
“STK33 is therefore considered a viable target with minimal safety concerns for contraception in men,” says reproductive biologist Martin Matzuk, who directs the Baylor lab.
The first female birth control pill was introduced almost 60 years ago and today there are many new forms available for people with female bodies, from oral pills to implanted devices.
In contrast, the last new male contraceptive to hit the market was in the 1980s, when scientists discovered how to perform a minimally invasive vasectomy.
For decades, the public and scientists have discussed the possibility of a male form of birth control. Ideas range from warming the testicles with nanoparticles, to “stopping” sperm with a pill, to an injectable hormonal “plug” for the testicles.
But even if some of these methods give good results in mice, designing a long-acting, reversible human drug without side effects has proven difficult.
In 2016, a clinical trial of a male contraceptive was halted due to negative side effects. Yet many were quick to point out the double standard: These same side effects, such as loss of libido, mood changes, and depression, are considered acceptable when contraception is intended for women.
When the female birth control pill was first introduced in the 1960s, the high doses of hormones caused serious and risky side effects, some of which increased heart attacks or strokes in patients.
Yet it took scientists more than a decade to figure it out, even though unpleasant and sometimes fatal side effects were apparent in the very first clinical trials in the 1950s.
Today, the process behind human drug research is much more rigorous, which is obviously a big improvement, but it also means it takes longer for scientists to “level the playing field” in regarding the contraceptive burden.
Baylor College of Medicine scientists are trying to close this gap, and their contraceptive candidate appears to be very effective at disrupting sperm function in mice. The team now wants to test their “excellent chemical probe” in non-human primates.
The study was published in Science.
News Source : www.sciencealert.com
Gn Health
