'Reversible vasectomy' one step closer for humans after successful monkey test

A form of male contraception involving a ‘reversible vasectomy’ has been successfully tested in monkeys, taking it a step closer to being available to humans.

The procedure involves a gel named valsalgel being injected into the tube that carries sperm out of the testicles – known as the vas deferens.

The gel forms an impenetrable barrier and halts the sperm in its tracks.

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A study in rabbits last year showed that the gel barrier can then be removed by flushing the duct through with a baking soda solution, thus forming a reversible alternative to a full vasectomy which involves cutting and sealing off the vas deferens.

The new trial involved 16 rhesus monkeys, none of which conceived during the trial period.

Lead scientist Dr Catherine VandeVoort, from California National Primate Research Centre, said, “Our research shows that Vasalgel placement into the vas deferens produces reliable contraception in mature male rhesus monkeys as shown by the lack of pregnancies in reproductively viable females with which the males were housed.

“Importantly, we show that the method of Vasalgel placement is safe and produced fewer complications than usually occur with a vasectomy.”

She added, “Vasalgel shows real promise as an alternative to vasectomy because research in rabbits has previously shown the product to be reversible.

“Although it is possible to reverse a vasectomy, it is a technically challenging procedure and patients often have very low rates of fertility following reversal.”

The only side-effect cited was that one of the treated monkeys showed signs of sperm granuloma, a hard build-up of sperm in the vas deferens.

The same non-serious complication affects around 60% of men undergoing a vasectomy, said the researchers.

The findings, reported in the journal Basic and Clinical Andrology, will pave the way for clinical trials, which are expected to begin next year.

Professor Adam Balen, chairman of the British Fertility Society, said: “If free of side effects then this novel approach has the potential for great promise as a male contraceptive. It is essential to know that the reversibility remains, irrespective of the duration of use.”