By Carlos Villatoro
The successful application of an alternative male contraceptive in rhesus macaque monkeys at the California National Primate Research Center is paving the way for human clinical trials.
For over a century, men who did not want to father a child had only one permament option for contraception. But according to the results of a study conducted at the California National Primate Research Center (CNPRC), there could be an alternative to a vasectomy that is as efficient and has the potential to be easily and successfully reversible.
The procedure involves the use of Vasalgel – a polymer-based hydrogrel that is injected into the vas deferens, which is the tube the sperm swim through on their journey to impregnation. The gel sits in the tube and essentially blocks the vas deferens, acting as a mechanical barrier to the passage of sperm. The study conducted by Professor Catherine Vandevoort and veterinarians Angela Colaglross-Schouten and Marie-Josée Lemoy resulted in the successful application of Vasalgel among a group of male monkeys, preventing them from having offspring throughout mating season.
Human clinical trials for a similar product, named RIUSG (Reversible Inhibition of Sperm Under Guidance) that lines the vas deferens but does not obstruct it, are being performed in male population in India, Lemoy said. The surgical procedure to expose the vas deferens is the same as a standard vasectomy, but instead of ligating and sectioning the vas deferens, Vasalgel is injected into the vas deferens. The advantage of this technique is that unlike a conventional vasectomy, it is potentially reversible.
Treated Monkeys Mated But No Pregnancies
The study at the UC Davis CNPRC involved 16 monkeys, each sexually mature, and lasted about a year. They were injected with Vasalgel and paired with female monkeys for several months, in some cases over a year. Although the monkeys mated the polymer successfully prevented pregancies.
The researchers did not attempt to reverse the procedure in the monkeys. Based on studies in rabbits, the injected polymer can be dissolved by using a solution of sodium bicarbonate, Lemoy said.
“The goal of our study was to find out if the procedure is safe, feasible and to find out if it prevents pregnancy,” Lemoy said. “After that they have to prove that it’s reversible.”
The results of the study were published in a white paper on Feb. 7. With proof of efficacy now published in monkeys and rabbits, preparations are being made for the first clinical trial in humans later this year. The Parsemus Foundation, a non-profit organization that developed Vasalgel, aims for contraception to be available world-wide, with a tiered international pricing structure to assure affordability to all men.
The first subsequent study to the CNPRC study will explore effectiveness; later studies will attempt reversal (flushing the gel to restore sperm flow), which has been demonstrated in rabbits but not yet in larger animals.