The quest for male contraception is ongoing and may have gotten a little boost, as researchers at University of Virginia managed to isolate and produce a targeted enzyme
involved in sperm motility. With the lab version of this enzyme ready, the team hopes to find drug targets that will stop the sperm from swimming to the egg, thereby preventing pregnancy.
While the drug has yet to be discovered, the team says getting to this point has is a huge milestone in itself. "The milestone reached is the production and isolation of a full-length, active kinase enzyme in sufficient quantities to conduct drug screens," said John Herr, professor at the University of Virginia School of Medicine, and senior study author. "Isolation of an active, full-length form of this enzyme allows us to test drugs that bind to the entire surface of the enzyme so that we can identify inhibitors that may exert a selective action on sperm."
The enzyme is known as testis-specific serine/threonine kinase 2 (TSSK2), which, as the name implies, is only found in the testes. In the late stages of spermatogenesis, TSSK2 is required for mature and functional sperm development. Without this enzyme, sperm will lack their normal motility functions, a key feature the team plans to exploit with drug candidates.
"The challenge in developing a new contraceptive is that a male 'pill' will be taken by perfectly healthy men," said Herr. "Because of this fact, a male contraceptive drug should be very precise in its mechanism of action, without any off-target side effects on molecules with similar properties located in other organs.” As such the TSSK2 enzyme is a perfectly specific in both location and function.
With this milestone achieved, the team has many more years of research ahead of them before a drug candidate makes it to clinical trials. But the discovery of the full-length enzyme will allow the team to move forward. In the next phase, the team will screen for drugs that bind to specific ‘pockets’ on the enzyme surface, which will act as a molecular jam to turn off the kinase activity. This drug will need to be highly specific so as to not inhibit the activity of kinases elsewhere in the body.
"Because a male contraceptive treats an otherwise healthy person, it's going to have to be very safe and efficacious, without side effects. Thus contraceptive research has a much higher bar [than in other forms of drug development], and it's going to take a determined march to reach the goal of a new, reversible contraceptive option for men," Herr said. "We're on the path toward the male contraceptive drug, and this is a noteworthy benchmark along that path."
Indeed the discovery moves the research much closer to identifying a male contraceptive drug. If successful, the drug will be the first to offer a non-hormonal, reversible, and condom-free way for males to effectively prevent pregnancy.
So far, another promising form of reversible, condom-free male contraception is the Vasalgel
. This alternative is a soft gel injected into the vas deferens to physically block sperm from passing through. The gel has passed animal studies and is slated for use in human clinical trials later this year. If all goes well, the Vasalgel could make it to the market in 2018.
Additional source: Science Daily