Boffins are developing two new methods for birth control that may eventually lead to the availability of a “male pill”.

H2-gamendazole, an organic compound that prevents sperm from reaching maturity, is going through animal testing. Sperm cells grow a tail and head in the testis, but H2-gamendazole blocks this metabolic process.

Unfinished sperm fragments are then reabsorbed into the testis without ending up in a man’s seminal fluid.

Crucially, effects are reversible once administration of a compound is stopped and there’s no effect on libido, at least according to early animal testing.

“If there's no sperm, the egg's not going to get fertilized,” Joseph Tash, a reproductive biologist at the University of Kansas Medical Center, told Wired. Tash and his colleagues have been working on the approach since 2001.

The FDA has reviewed the compound, whose suitability as a “reversible anti-spermatogenic contraceptive agent in non-human primates” is one of the principal aims of the latest phase in animal testing. Previous testing in rats has been promising, as a research brief by the University of Kansas explains.

H2-gamendazole (H2-GMZ) is now identified as most promising, with 100 per cent oral bio-availability, and 100 per cent infertility followed by 100 per cent recovery of fertility in rats, with no loss in mating behaviour. Pilot proof-of-concept studies in non-human primates showed completely reversible declines in spermatid count and semen sperm count with no adverse side effects.

If successful, the latest round of animal testing would clear the way towards pre-clinical toxicology and registration for the start of clinical trials in humans.

However, the approach, although promising, is still some years away from offering an alternative to condoms and vasectomies as a method of birth control.

Boffins at Harvard are working on a different approach towards the same end. JQ1, an organic compound originally developed to block a bromodomain in cancer cells, was also discovered during testing to obstruct a testicle-specific bromodomain called BRDT. The compound effectively turns off the creation of sperm.

Medical researchers are attempting to create a version of the molecule that works on the testicle protein only, in order to minimise side effects.

Other research into non-hormonal male contraception are summarised in a paper by John K. Amory MD, a professor of medicine at the University of Washington, here. ®