Three Infertile Baboons May Mean We’re One Step Closer to Male Birth Control

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Analysis Contraception

Three Infertile Baboons May Mean We’re One Step Closer to Male Birth Control

Martha Kempner

Vasalgel, a new method of birth control currently in development, could block the vas deferens and prevent sperm from ever being ejaculated. A new study on baboons suggests the product works, but we've been promised male birth control before to no avail.

The Parsemus Foundation announced this week that it is one step closer to a birth control option for men after mating tests proved three baboons injected with Vasalgel, a polymer gel, remained infertile after six months.

A successful study of the product in rabbits was completed last year and the research team says baboons are the last stop before hopefully pulling together a clinical trial in humans. There remain numerous hurdles for the company and the product—both technical (determining fertility in a baboon is harder than it looks) and financial.

Male contraception (other than the condom) has been “just around the pharmaceutical corner” for decades, but one has yet to come to market. Scientists are looking at a number of ideas to temporarily halt fertility in men, but there have been problems with each of them.

The most frequently discussed is a hormonal contraceptive that would interrupt testosterone production and stop the testes from making sperm. Since testosterone has other functions, men would have to take some kind of limited testosterone supplement at the same time. Another idea in development blocks retinoic acid, which is important for sperm development, though research hit a snag when men who tried one such drug became sick if they drank alcohol.

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Other research has tried to disrupt sperm maturation so that they would not be functional or able to fertilize an egg, reduce the mobility of sperm so they could not reach the egg, or halt sperm production by using ultrasound to heat the testes—a procedure that would have to be done every few months.

Vasalgel is most similar to something called Risug (reversible inhibition of sperm under guidance), which has been in development in India for more than a decade. The idea is to inject a polymer gel into the vas deferens in order to block the path of the sperm, which use these tiny tubes to travel from the testes to the urethra and ultimately out of the penis during ejaculation.

This is the same basic concept behind male sterilization, also known as a vasectomy, in which doctors sever the vas deferens. The difference is that the gels are easily reversible. If a man wishes to have his fertility restored, his doctor can inject another substance into the scrotum that flushes out the vas deferens, once again clearing the path for sperm. Though the two gels are based on this same concept, the makers of Vasalgel say the formulations are different.

Last year, researchers declared that Vasalgel successfully blocked sperm in rabbits. Now they note that three male baboons who had the gel in place for more than six months remained infertile, which was determined by placing them in an enclosure with 10 to 15 female baboons and checking for any pregnancies.

The males were tested for fertility prior to the start of the study in a similar way. That time, pregnancies were considered good news. It is unclear whether the female baboons were also tested for fertility or if the sheer number of females was used as a way to guard against one or two infertile ladies in the bunch.

The research team explained that this mating method of proving or disproving fertility is being used because of issues with sperm collection. In a human trial, men would be asked to provide a semen sample to prove there were no longer any viable sperm, much like they are asked to do a few weeks after a vasectomy. In the rabbit study, the research team reported easily being able to collect semen so long as they provided a female rabbit to excite the males. But collecting semen from a baboon is apparently more complicated.

Researchers used “a device with mild electric currents [that] stimulates the nerves near the prostate gland, which creates contraction of nearby muscles—and ejaculation.”

Though this is common in animal studies, it turned out that the device or the electrical currents dislodged the gel and caused fertility to return in some of the baboons. The team is starting with a new group of four male baboons and going back to proof-by-mating.

Despite this complication, the Parsemus Foundation believes the baboon trials to be a success because three of the baboons from the original study remain infertile after more than six months. The next step for these three subjects is to remove the gel and see if their fertility returns.

The other good news for the researchers came in the form of a $50,000 grant from the David and Lucile Packard Foundation to support the baboon study. The Parsemus Foundation has funded this project through donations and crowd-sourcing, but says that it is still short of the money needed to complete this study.

Funding is widely expected to remain a primary obstacle in getting male birth control around that pharmaceutical corner.

It takes a lot of money to go from concept to contraceptive, and before they will invest in research and development companies want to know they’ll make a lot more money once the product is on the market. This is the all-important question that researchers, pharmaceutical companies, and public health experts have been grappling with for years. Are men really interested in taking responsibility for birth control?

And, in this case, will they still be interested when they learn it comes in the form of a scrotal injection?

The Parsemus Foundation says that we could know as soon as 2017, which is when it predicts (if all goes well) the gel would become available, but that seems optimistic as none of this research has yet been published in peer-reviewed journals (results of the rabbit study is expected to be officially published this year) and researchers haven’t yet moved from monkeys to men.