Nav: Home

Successful reversal of Vasalgel male contraceptive in rabbits

April 04, 2017

Results of a study of a promising new male contraceptive called VasalgelTM were published today in Basic and Clinical Andrology. The polymer gel is injected into the vas deferens and blocks the passage of sperm. The study followed the progress of seven rabbits successfully contracepted for an average of 14 months before the gel was flushed out. Sperm flow returned in all animals after reversal, confirming unobstructed sperm transit (patency of the vas deferens) and warranting continued development of this product.

Few current male contraceptive options

When considering reproductive control, couples often rely on female contraceptive methods, including daily pills and long-acting products such as IUDs and implants. However, many women cannot tolerate the side effects of hormonally-based contraceptives and grow frustrated with the downsides of other methods.

Men who wish to control their own reproduction or lift the burden of contraception from their partners have even fewer options. No new male contraceptives have emerged in more than a century, and men must rely on the old standbys: condoms, which are important for reducing the incidence of sexually transmitted infections in new relationships but result in high pregnancy rates in typical (imperfect) use; withdrawal, which has an even higher pregnancy rate in typical use; and vasectomy, which is very effective but should be considered permanent due to the unpredictability of successful reversal. The need for a long-acting, reversible male contraceptive -- without the side effects of hormones -- has been demonstrated in international surveys and could be met by Vasalgel.

How Vasalgel works

Vasalgel functions like a reversible vasectomy, blocking or filtering out sperm. The device is implanted into the vasa deferentia (singular: vas deferens) -- the small tubes that transport sperm from the testes. It is composed of high molecular weight polymer powder dissolved in dimethyl sulfoxide (DMSO), a biocompatible solvent. The resulting Vasalgel implant remains in a soft gel-like state that allows water-soluble molecules to pass but not larger structures such as spermatozoa. This quality is thought to be a benefit for preventing back-pressure on sperm storage areas. The contraceptive effect lasts for years, and, importantly, is developed to be reversible by a second injection to dissolve the Vasalgel.

Demonstration of efficacy and reversibility in rabbits

In a previous publication in 2016, the research team reported Vasalgel provided effective contraception in rabbits. Vasalgel produced a rapid onset of azoospermia, with no live sperm in semen samples collected as early as 29-36 days post-implantation, and the effect was durable over a 12-month period. The device was safe and was well-tolerated by the rabbits with minimal effects on the structure of the vasa deferentia.

The follow-up study published today reported the results of reversing the contraceptive effect of Vasalgel in the same rabbits. Seven rabbits, successfully contracepted for 14 months following Vasalgel implant, underwent a reversal procedure. A sodium bicarbonate (baking soda) solution was injected into the vasa deferentia of each rabbit to dissolve the implants and clear the blockage. Baking soda is known for its ability to safely neutralize acids. In this case, the bicarbonate solution neutralizes and breaks down the hydrogel structure of the polymer gel. Sperm flow returned quickly, as evidenced by spermatozoa present in the semen of all animals.

Further evaluation of the sperm characteristics after reversal indicated sperm concentrations and sperm motility were similar to baseline levels, an important first step to a return of fertility. The sperm forward progression measurements were significantly lower than the baseline measurements but increased consistently during six months of follow-up semen collection.

Microscopic evaluation of the vasa deferentia indicated that most had an intact epithelial lining (inner lining tissue) and were clear of the gel. A smaller proportion of tissues contained residual gel, and an occasional secondary intraluminal inflammatory response (minor inflammation inside the vas deferens) was observed. Rabbits have unusually large and thus vulnerable acrosomes (caps) on the heads of their sperm, which were not observed following reversal. Residual material may have impacted the sperm forward progression and caused loss of acrosomes during transit through the vas.

"The results of the Vasalgel reversibility study in rabbits indicate the implant could be removed resulting in a quick return of sperm flow," said lead author Donald Waller, Ph.D. "We were pleased that the number of sperm and their motility after reversal were no different from baseline measures. More flushing during reversal may be needed to remove traces of the gel from the vas deferens, which appeared to impact other sperm characteristics."

The results of the study provide momentum for continued development of Vasalgel as a male contraceptive.
-end-
The DOI for this article is: 10.1186/s12610-017-0051-1. After Wednesday April 5 at 1 a.m. BST / Tuesday April 4 at 8 p.m. EDT the full-text version of the study will be available online at: https://bacandrology.biomedcentral.com/articles/10.1186/s12610-017-0051-1

Next steps

Vasalgel is being developed as a non-hormonal, long-acting, reversible male contraceptive by Revolution Contraceptives, LLC, a social venture subsidiary of Parsemus Foundation, a nonprofit organization based in the San Francisco Bay Area.

Vasalgel has demonstrated efficacy in monkeys and rabbits in previously published studies. This study is the first to demonstrate reversibility. Reversal in larger animals has not been confirmed and is an active research focus.

"This study gave us the confidence to continue development of Vasalgel," said Elaine Lissner, founder and trustee of Parsemus Foundation. "We flushed out most of the gel and restored full sperm flow. Now the thousands of followers of Vasalgel's progress are counting on us to refine and repeat this reversal success in larger animals."

With contraceptive efficacy well-established in multiple species, preparations are being made for the first contraceptive efficacy clinical trials in humans. Parsemus Foundation aims for Vasalgel to be available worldwide, with a tiered international pricing structure to ensure affordability to all men.

To fund the development of Vasalgel, Parsemus Foundation is seeking socially-minded investors and foundation partners who are committed to affordable access. Social venture funding will be critical to meeting the goal of starting clinical trials in 2018. For more information on funding and partnership opportunities, please contact info@parsemusfoundation.org.

About Parsemus Foundation: Parsemus Foundation works to advance innovative and neglected medical research. Many of the studies the foundation supports involve low-cost approaches that are unlikely to be pursued by pharmaceutical companies due to limited profit potential. Successful studies to date have included breast cancer treatment advances, low-cost readily available nonsurgical dog and cat sterilization, and non-invasive treatment of benign prostatic hyperplasia using a currently marketed device. Parsemus Foundation's current main focus is bringing Vasalgel to market. More information on Parsemus Foundation and the work presented here can be found at: https://www.parsemusfoundation.org/projects/vasalgel/

Images, key facts, and statistics: see https://www.parsemusfoundation.org/media-resources/

Parsemus Foundation

Related Sperm Articles:

New test assesses sperm function
Two new publications in the journal Molecular Reproduction and Development validate the usefulness of a test that determines if sperm can capacitate, a process that allows them to fertilize an egg.
Mystery of how sperm swim revealed in mathematical formula
Researchers have developed a mathematical formula based on the rhythmic movement of a sperm's head and tail, which significantly reduces the complexities of understanding and predicting how sperm make the difficult journey towards fertilizing an egg.
Sperm changes documented years after chemotherapy
A Washington State University researcher has documented epigenetic changes in the sperm of men who underwent chemotherapy in their teens.
Out of gas and low on sperm?
Sperm are constantly replenished in the adult male body. Understanding the workings of stem cells responsible for this replenishment is expected to shed light on why male fertility diminishes with age, and possibly lead to new treatments for infertility.
Fish sperm race for reproductive success
Many organisms compete for access to and acceptance by mates.
What does the sperm whale say?
When a team of researchers began listening in on seven sperm whales in the waters off the Azores, they discovered that the whales' characteristic tapping sounds serve as a form of individual communication.
Smoking may have negative effects on sperm quality
A recent study found that that sperm of men who smoke has a greater extent of DNA damage than that of non-smokers.
How females store sperm
The science of breeding chickens has revealed part of the mystery of how certain female animals are able to store sperm long-term.
Female birds select sperm 'super swimmers'
Sperm with shorter heads and longer tails are better at fertilising eggs, study reveals.
Why fruit fly sperm are giant
The fruit fly Drosophila bifurca is only a few millimeters in size but produces almost six centimeters long sperm.

Related Sperm Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Climate Crisis
There's no greater threat to humanity than climate change. What can we do to stop the worst consequences? This hour, TED speakers explore how we can save our planet and whether we can do it in time. Guests include climate activist Greta Thunberg, chemical engineer Jennifer Wilcox, research scientist Sean Davis, food innovator Bruce Friedrich, and psychologist Per Espen Stoknes.
Now Playing: Science for the People

#527 Honey I CRISPR'd the Kids
This week we're coming to you from Awesome Con in Washington, D.C. There, host Bethany Brookshire led a panel of three amazing guests to talk about the promise and perils of CRISPR, and what happens now that CRISPR babies have (maybe?) been born. Featuring science writer Tina Saey, molecular biologist Anne Simon, and bioethicist Alan Regenberg. A Nobel Prize winner argues banning CRISPR babies won’t work Geneticists push for a 5-year global ban on gene-edited babies A CRISPR spin-off causes unintended typos in DNA News of the first gene-edited babies ignited a firestorm The researcher who created CRISPR twins defends...