Data supporting claims of a “super birth control pill” leaves much to be desired
Animal advocates around the world are eager for safe, effective, affordable, non-surgical methods to prevent the births of unwanted puppies. And when 600 Million Stray Dogs Need You (600 Million) announced early this year that it had found a birth control pill that causes sterility and is completely safe and effective, it sounded like a dream come true. So is it true, or just a dream? ACC&D President Joyce Briggs attended a briefing held by 600 Million in Los Angeles on December 2, 2010, eager to find that this dog sterilization pill was indeed a reality. Unfortunately, it appears that the scientific data lags far behind the story being told by 600 Million.
ACC&D first learned of this approach, called ChemSpay and developed by a company called SenesTech, in 2004. We were intrigued by published data from studies in mice, which showed that several weeks or more of daily treatments caused sterility, and by the company’s suggestion that this technology might also work in dogs and cats. Results that SenesTech shared in 2007 from studies in a small number of dogs (supported in part by funding from ACC&D) were less promising, bringing to light some significant hurdles to demonstrating safety and efficacy. In 2008, SenesTech’s research turned back to birth control for mice and rats, which are responsible for the devastation of rice crops around the world, though the researchers planned to return to work in dogs in the future. ACC&D remained interested in this technology, while recognizing that it was still in the very early stages of development and that success in rodents would not necessarily translate to dogs and cats.
Now ChemSpay for dogs is back in the limelight, thanks to a partnership between the nonprofit organization 600 Million and SenesTech. But while 600 Million is quick to make specific promises that this technology works in dogs (and that, when work is completed, a single treatment will be effective), the scientific data shared to date do not support these statements. At the briefing, previously published results from studies in mice were described, but although over 270 dogs are said to have been included in studies, only a few examples were given of effects on dog ovaries, with little detail about dose, route of administration, number of doses used, or even number of dogs tested. ABC Los Angeles, which attended the December 2 briefing and interviewed the researchers, reported that three or four oral doses sterilized just 20 percent of the dogs in one study.
“Although we were hopeful that new data would be introduced at the briefing showing that Chemspay, given either as an injection or a pill, sterilized dogs, we were disappointed that there was no documentation of any significant achievements beyond what was shared with us in 2007,” commented ACC&D President Joyce Briggs. Even Dr. Loretta Mayer, lead researcher working on the ChemSpay project, conceded that the technology is still at an early stage for use in dogs. But communications from 600 Million suggest that the technology is ready to be submitted for regulatory approval.
In addition to a shortage of data showing the technology works, there are also key unanswered questions about safety. SenesTech asserted at the briefing that since the targeted reproductive pathways are conserved across all mammalian species, this chemical will certainly sterilize female dogs as it does mice. However, oddly, they also stated that the chemical does not have any effects in primates and is completely safe for humans (also mammals). The chemical in Chemspay is 4-vinylcyclohexene diepoxide (VCD), used widely in manufacturing products such as tires, polyesters, and epoxy resins. Other work with VCD showed that it does in fact impact fertility in monkeys,1 although subsequent work was not been able to replicate this result.2 VCD has also been shown to be a dermal carcinogen in mice and rats after multiple applications to the skin,3 which raises questions about safety in other species. Given such findings, much work will be needed to substantiate the claims being made that this compound is safe and effective for use in dogs and that it will have no impact on women handling it.
The invitation to the briefing noted that that “Cheetah, one of the first dogs in the world to be sterilized without surgery, [would] be available for visits.” Dr. Mayer shared that Cheetah was treated nearly six years ago with multiple injection treatments of ChemSpay and then surgically had her ovaries removed to examine the effects of the treatment. Yet, those results showed 67 percent depletion of primordial follicles, with no data to show sterility. Cheetah is sterile now, since her ovaries were removed after treatment.
ACC&D is committed to basing our communications and actions on sound science. Our Board of Directors and Scientific Advisory Board include experts in animal welfare, animal health, veterinary medicine (including dog and cat reproduction), international dog and cat population control, regulatory requirements for animal health products, and public health. “We believe it's critical that stakeholders in this work are provided with accurate information and a realistic picture of the most promising paths toward more humane and effective methods of controlling unwanted cat and dog populations,” writes ACC&D board chair Linda Rhodes, VMD, PhD, who specializes in the regulatory submission and review process for animal health products. “We’re concerned to see these statements being made about this technology unsupported by facts and data. Based on what has been shared publicly, there is still a long way to go to prove that this approach is as safe and effective as claimed by 600 Million and SenesTech. ACC&D will seek clarification and new information about this technology, and will share important updates.”
ACC&D hopes to see technologies advance that can provide safe and effective sterilization for dogs as well as cats. We look forward to seeing more data to demonstrate that this chemical may become a new tool for those working to humanely control pet populations everywhere, and we encourage 600 Million and SenesTech to share that data with the public as they ask for donations. While there are many unanswered questions here, what is not in doubt is the critical need for faster, easier, less expensive and less invasive methods for sterilizing cats and dogs and preventing unwanted litters.
The Alliance for Contraception in Cats & Dogs (ACC&D) is a nonprofit animal welfare organization based in the U.S. but with global scope. Our mission, pursued over the last 10 years, is to expedite the successful introduction of methods to non-surgically sterilize dogs and cats and to support the distribution and promotion of these products to humanely control cat and dog populations worldwide. ACC&D’s efforts are supported by over 120 Organizational Partners, including animal welfare, animal health, and public health organizations from around the world.
1. Amppt SE, et al. Destruction of primordidal ovarian follicles in adult cynomolgus macaques after exposure to 4-vinyl cyclohexene diepoxide: a nonhuman primate model of the menopausal transition. Fertility and Sterility 86(4): supplement 1210-16, 2006.
2. "Flagstaff firm inks deal with Australia for rodent-control test." Arizona Biosciences News/Flinn Foundation, June 18, 2008. http://www.flinn.org/news/756
3. Maronpot RR. Ovarian toxicity and carcinogenicity in eight recent National Toxicology Program studies, Environmental Health Perspectives 73:125-30, 1987.