Sperm-busting male contraceptive pill in the pipeline

Scientists are in the process of developing a male contraceptive drug which stops the development process of sperm.

The team from the U.S. and Italy have conducted tests on rats which block the connections to cells which "nurture" developing sperm.

The process makes the animals infertile and the researchers say that the low doses of the molecule used meant there were no obvious side effects, and the effect was reversible.

But biomedical researchers at the Population Council in New York say more research is needed to establish if the approach is equally effective and safe in men.

During spermatogenesis, when sperm are being made in the body, the sperm establish themselves next to other cells, called Sertoli cells, which nurse and help them flourish.

When the connection between these two cell types is broken, the result can be infertility in men.

For their study the scientists used a recently developed molecule called Adjudin to dislodge the developing sperm from the Sertoli cells.

Adjudin is known to be toxic at high doses and in order to avoid the toxic effects the researchers linked it chemically to a hormone, called follicle-stimulating hormone (FSH), which is critical for sperm production. It supports the function of Sertoli cells, which in turn support many aspects of sperm cell maturation.

The researchers rendered the FSH inactive so it would merely act as a carrier and not cause any effect itself, but delivered the Adjudin to where it was needed, which allowed much lower doses to be given.

This action made the developing sperm cells drop off before they were properly mature, resulting in complete but temporary loss of fertility in the rats.

The researchers, led by Dr. Dolores Mruk, from the Center For Biomedical Research in New York, anticipate that the compound could become a male contraceptive for human use.

Experts in the field say a non-hormonal approach to male contraception using a drug which specifically targets a process in spermatogenesis is very promising.

Senior team member of the research team at Population Council Yan Cheng says the drug still needs several years of animal testing before a human trial is conceivable.

Scientists have been unable to develop a male contraceptive pill because a man naturally produces about 150 million sperm cells each day of his adult life.

The results of the trial are published in the journal Nature Medicine.