Successful Application Of Male Contraceptive In Monkeys
The demand for new male contraceptive methods is growing. Surveys indicate that the majority of men would be interested in using a new contraceptive, and about 20% of couples already rely on existing male methods for reproductive control. While research has uncovered a variety of new targets for male contraception, no new product has made it to market yet. Many men say they would prefer a non-hormonal option because of the potential side effects and safety risks of hormones. However, studies of hormonal approaches continue to receive the most funding as evidenced by the recent publication of serious side effects in a large study of a hormonal method.
The study chronicles the use of Vasalgel™ A new nonhormonal, long-acting option,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 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. Sperm flow quickly resumed.
Sixteen adult male rhesus monkeys received 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. All males were monitored for at least one breeding season; 7 of the 16 were almost continually housed with females for two years. The study authors reported that there were no conceptions after Vasalgel injections.Intravas injection of Vasalgel in sexually mature adult male rhesus monkeys was effective in preventing conception in a free-living, group environment. Complications were few and similar to those associated with traditional vasectomy. The males could be returned to their group quickly, providing minimal disruption to the social structure of the group while not impeding natural behaviors such as mating.
With proof of efficacy now published in monkeys and rabbits, preparations are being made for the first clinical trial in humans. Parsemus Foundation, a non-profit organization based in Berkeley, California, aims for Vasalgel to be available world-wide, with a tiered international pricing structure to ensure affordability to all men. The first study will explore effectiveness; later studies will attempt reversal (flushing the gel to restore sperm flow), which has been demonstrated in rabbits (in press) but not yet in larger animals.
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