The burden of birth control has long fallen on women. There are numerous more forms of birth control available to women–ranging from oral pills to internal IUDs–than men, who rely primarily upon condoms. Vasectomy is the sole long-acting method available to men. Now, however, researchers from the California National Primate Research Center at University of California, Davis, have successfully tested the effectiveness of a new contraceptive gel called Vasalgel™, in adult male rhesus monkeys living in small group housing for at least one breeding season and up to two years. Their results, published in Basic and Clinical Andrology, showed the gel to be 100% effective at preventing pregnancies in fertile—called “intact”—rhesus monkeys. The gel is a high molecular weight polymer developed in the US, formulated to work by occluding—or blocking—the vas deferens, which is a tiny muscular tube that carries sperm from the testicles to the penis.
Vasalgel was inspired by the Parsemus Foundation’s work on a polymer contraceptive called RISUG®, which is in advanced clinical trials in India; some of those men have been using RISUG® for over 15 years. However, in order to qualify for the study, men must be local, so wider clinical trial for men have not yet moved to the US or other countries.
The gel does not contain any hormones or deliver any pharmaceutical effects. First tested successfully in rabbits, Vasalgel™ is injected into the lumen, or main cavity of the vas deferens, forming a physical barrier through which the sperm cannot pass. Moreover, at least in rabbit subjects, the gel has been found to be reversible by flushing the gel out with a saline solution, successfully restoring sperm flow. Researchers are hoping this treatment might end up being an alternative to vasectomy, a surgery in which the tubes of the vas deferens from each testicle are cut, clamped or sealed, preventing sperm from reaching the penis. The sperm are then reabsorbed in the body. Vasectomies are a common procedure, but they are rarely reversible, and may bring buyer’s remorse for a percentage of men who change their minds and decide they do want children years later, after it’s possibly too late.
In comparing the Vasalgel procedure, VandeVoort says, “The rate of side effects was not significantly different than the vasectomy, and possibly even less than vasectomy.” She feels the side effects, such as swelling and irritation, had more to do with “the learning curve” of the researchers performing the surgery than the procedure itself. “The side effects we did have seemed to come earlier to the first few animals.”
Longevity is one of the key benefits of Vasalgel,™ as far as researchers can tell in animal models. “Some of the animals in the rabbit study covered two breeding seasons. We don’t know how long it will last but the fact is we’re into multiple year territory, which is a really good sign,” says Catherine VandeVoort, co-author of the study, a core scientist at the California National Primate Center, and a professor of obstetrics and gynecology at UC Davis.
VandeVoort and her team tested the gel in non-human primates, specifically rhesus monkeys, whose physiology is more similar to humans. VandeVoort says the study allowed the primate center to achieve one of their goals, as well. “We were trying to reduce the number of offspring we were producing, so having vasectomized animals was useful.”
Rhesus monkeys have a breeding season that ranges from September through May depending on whether they are kept indoors or outdoors. When kept indoors, researchers can breed animals in that time with success. “Outdoors it’s similar except most of the animals who will get pregnant fairly soon in the breeding season,” she says. Sixteen male monkeys were given the gel. Half of the monkeys were housed for at least one complete breeding season, and half for two complete breeding seasons with fertile females. There were no pregnancies.
Vandervoot says one of the reasons the gel method is getting so much attention and is so exciting for researchers is that, for men, “the options are pretty crummy.” She expounds, “If, as a woman, someone said to you that you need to take responsibility for birth control and we’re going to give you a choice of abstinence, condoms or sterilization, how would you feel?” she asks. Vandevoort goes so far as to say that men are “desperate” for options.
Brian Levine, a fertility doctor and founding partner of CCRM New York, a fertility clinic, agrees with her assessment. His male patients frequently inquire about new contraceptive methods beyond condoms. In his practice, many male patients seek contraception because their female partners can’t use traditional birth control. “Say the woman is a breast cancer survivor so she can’t have hormonal contraceptive, or she has fibroids in the uterus, so she can’t get an IUD. There are lots of reasons why female contraception might not work.” For men who don’t want a permanent vasectomy, he feels that Vasalgel™ “affords the ability to have a near permanent form of contraception that is now under the direct control of the patient.”
Of course, the true test of Vasalgel™’s success, VanderVoort emphasizes, “hinges on whether or not it’s reversible. We wanted to get a report out there that it could be effective for a relatively long term.” Now they’ll need to study the monkeys’ fertility over time, see if they can flush it out of the monkeys as easily as in the rabbits without affecting sperm flow, and then eventually move to human trials. If it is reversible, it holds great promise. “A young man in his twenties could have a long acting contraceptive, until he gets to the point where he says ‘Okay, now I want to have children,” she says.
Additionally, Levine points out that while it would be a great form of contraception for someone in a committed relationship, it’s not something you can get on the fly for a night out, or if you plan to have intercourse with more than one partner. “As with vasectomies, or women with IUDs, this doesn’t protect against sexually transmitted infections. If you’re sleeping with random partners, you do need to use a barrier like a condom,” he makes clear.
It’s also important to remember that getting Vasalgel will require a surgery not unlike a vasectomy in its side effects: an incision will need to be made in order to inject the gel in the proper part of the vas deferens, and there may be some recovery time before a man is ready to have intercourse again, as well as a semen analysis done after installation, “to make sure it’s obstructed and no sperm are leaking.” And of course, finding someone to perform the procedure may not be so easy right away. “This is a procedure that will require advanced skill,” Levine says. “The success of such a skill will require people who have formal training, which is a barrier in and of itself.” For one thing, the practitioner will need to make sure the gel is in the right place—that it doesn’t go into the wall of the vas deferens, but specifically the lumen, and that they don’t overinflate the vas deferens, which can cause injury.
All in all, however, Levine says “I’m very optimistic about it, since it’s relatively easy to do and should have a good result.”
VandeVoort emphasizes that the success of this contraceptive will depend upon getting future funding so they can test in humans first.