Vasalgel - Male contraceptive jab prevents pregnancy in monkeys for more than a year

New Delhi: An injectable male contraceptive believed to be more effective than pill has been successful in monkey trials.

Scientists said the contraceptive blocks sperm flow with a gel, preventing pregnancy in monkeys for up to two years and bringing the prospect of an alternative form of birth control for humans closer.

The researchers from California National Primate Research Center in the US, said the contraceptive called Vasalgel provided effective birth control in rhesus monkey groups for more than one year.

They said with proof of efficacy in monkeys and rabbits, preparations are being made for the first clinical trial in humans as early as next year.

Male contraceptive options have not changed in over a century, and are currently limited to condoms and withdrawal (with high pregnancy rates in typical use), or vasectomy (meant to be permanent), they said.

The trial used Vasalgel in groups of rhesus macaques - confirming previous preclinical findings in rabbits on the efficacy of the new device and offering a new tool to colony managers.

"Vasalgel is a high molecular weight polymer that consists of styrene-alt-maleic acid (SMA) dissolved in dimethyl sulfoxide and could be the first long-acting, non-hormonal, potentially reversible male contraceptive to reach market," the company behind the gel said.

The polymer forms a hydrogel after injection into the vas deferens, creating a blockage to the passage of sperm.

It is thought that fluids are able to pass slowly through the gel, reducing back-pressure on the epididymis (the sperm storage area) that has been noted after vasectomy.

The contraceptive effect of Vasalgel has been "reversed" in a rabbit model by flushing the material out with a simple sodium bicarbonate solution, researchers said.

The purpose of the current study was to put Vasalgel to the ultimate test - preventing pregnancy, not just eliminating sperm - in larger animals more anatomically similar to humans, before human use. However, the contraceptive had benefits to the monkeys as well, they said.

For the study, sixteen adult male rhesus monkeys were administered intravas injections of Vasalgel. After a one-week recovery, each male was returned to outdoor group housing, which included three to nine intact, breeding females with a successful reproductive history.

The monkeys lived in social groups in a setting that is closer to a free-living environment than traditional research housing, following and exceeding European guidelines for space per monkey.

All males were monitored for at least one breeding season; 7 of the 16 were almost continually housed with females for two years.

The researchers reported that there were no conceptions after Vasalgel injections.

Complications were minor and included one incident of incorrect placement of Vasalgel into the vas deferens and the development of a sperm granuloma in one animal.

"While vasectomy is a quick and relatively simple procedure in humans, in monkeys there can be additional complications, as it is inherently more complex," said Angela Colagross-Schouten, lead veterinarian on the project.

With various ongoing research studies, researchers are hopeful that a safe, effective and reversible method of male contraceptiion will become a reality in the near future.

The latest findings have been published in the journal Basic and Clinical Andrology.

(With PTI inputs)