Vasagel (Vasalgel) is a high molecular weight polymer developed by the Parsemus Foundation as a non-hormonal male contraceptive with a long-term, potentially reversible effect. It is introduced into the ejaculatory ducts and blocks the passage of sperm. The results obtained in experiments on rabbits indicate the high promise of a new approach to male contraception.
Currently, men have a small number of methods of control over their reproductive function. The most popular of these is the use of condoms, which, when used correctly, provide protection against sexually transmitted infections and reduce the risk of an unwanted pregnancy by 18%. The most effective, but irreversible approach to male contraception is a vasectomy, which consists in excising the vas deferens.
Every year, more than 85 million unwanted pregnancies are registered worldwide, which indicates a serious need for new methods of contraception. The results of international surveys indicate that most men do not object to the use of new methods of male contraception, with variations due to demographic and cultural characteristics. Over the past decades, researchers have proposed several potential methods of regulating male reproductive function, but not one of them has yet appeared on the market, which is largely due to financial and regulatory difficulties. Moreover, until now, work has been carried out mainly on hormonal approaches, even despite the fact that due to the likelihood of developing hormonal side effects and safety issues, most men are inclined to non-hormonal methods.
The results obtained in rabbit experiments indicate that Vasagel, which is a polymer of styrene-alt-maleic acid, dissolved in dimethyl sulfoxide (DMSO), is quite capable of filling an empty niche in the long-term method of male contraception.
Researchers led by Professor Donald Waller of the University of Illinois at Chicago tested two Vasagel variants, one containing 100% styrene-alt-maleic acid, and the other a combination of 80% styrene-alt-maleic acid and 20% anhydride (dehydrated form) of styrene-alt-maleic acid. 29-36 days after the drug was introduced into the vas deferens of rabbits and during the subsequent observation period of 12 months, sperm was completely absent in sperm from 11 of 12 animals. Several sperm samples from one rabbit contained a small amount of sperm, after which he also developed azoospermia. Two tested variants of the drug had the same effectiveness. At the same time, the reaction from the tissue of the vas deferens was weakly expressed and corresponded to a normal reaction to a foreign body.
According to the authors, Vasagel was even better than they expected, which is most likely due to its characteristics. After introduction into the vas deferens, the vasagel material forms a hydrogel, which retains its soft gel-like consistency, providing its ability to compress and adhere tightly to the walls of the ducts. Moreover, the structure of the hydrogel allows the passage of water and many soluble molecules in it, but does not allow larger structures, such as sperm, to provide a contraceptive effect without a significant increase in hydrostatic pressure in the epididymis and ducts, within which sperm are formed and accumulate.
The diagram shows the change in sperm concentration
after implantation of Vasagel in the vas deferens 12 rabbits.
Unfortunately, it is not worth rejoicing yet: in this study, the reversibility of azoospermia after washing the vas deferens from the gel was not checked, and Wikipedia wrote about this method, among other things, and that clinical trials on volunteers in India were stopped in 2002 for suspicions of nephrotoxicity of dimethyl sulfoxide (although they started again in 2011), and the recovery procedure was tested only on primates and "she had repeated success." What is "repeated" is not said, the link is missing.
Article by Donald Waller et al. Azoospermia in rabbits following an intravas injection of Vasalgel is published in Basic and Clinical Andrology.