Breakthrough in non-surgical sterilization for cats and dogs

tabby cat lying on blanket[Updated June 3, 2021]

It’s been the holy grail of animal welfare for decades now: A single injection or medication that will permanently and safely sterilize dogs and cats – especially cats. We may be about to achieve it.

No one has been more on the forefront of this quest than the Alliance for Contraception in Cats & Dogs (ACC&D). In their most recent biennial report, they raised the prospect of reaching the goal with these words about ongoing gene transfer research:

ACC&D’s 2018 Symposium highlighted one particularly promising approach to sterilize cats and dogs without surgery: gene transfer. Researchers presented on work underway, and the keynote address offered delegates a glimpse into how gene transfer breakthroughs have both improved and saved human lives.

Thanks in large part to support from the Michelson Found Animals Foundation (MFAF), which has committed $75 million to develop a permanent non-surgical sterilant for cats and dogs, there was even more reason to be optimistic at the close of 2020.

Based on positive results from a one-year study with a single-dose injection, researchers entered a second-year breeding trial in female cats. Evaluating whether a gene transfer treatment results in permanent sterility requires patience and a multi-year breeding trial; each time animals fail to become pregnant, we get one step closer to a viable product.

We spoke with longtime ACC&D president Joyce Briggs about this news, and whether a gene transfer-based product to sterilize female dogs and cats that may soon be entering the approval pipeline.

“We’re extremely excited about this MFAF-funded research,” she said. “The results are promising to the point that the research will be shifting from the grant project phase to a product or technology development phase.”

The second year trial mentioned in their biennial report has now concluded, and was extremely successful as well. “The results were just what we were hoping for,” Briggs said. “There is quite a lot more continued research that needs to happen to assure that it’s permanently effective and safe, but all indications are very positive so far.”

Gene Transfer Approach to Sterilization in Cats and Dogs

What does the gene transfer approach involve? From the perspective of the veterinary or animal welfare staff who administer it, it’s a single injection given into the cat’s thigh muscle.

From the scientific point of view, this study is part of a growing area of human as well as veterinary medical research into gene therapy, which is being studied for treatment of ovarian cancer, hemophilia, HIV, heart disease, muscular dystrophy, and more.

In this specific application, the injection transmits a gene attached to a non-disease-causing virus known as adeno-associated virus (AAV). This gene carries a blueprint to make a a hormone known as Müllerian inhibiting substance (MIS) or anti-Müllerian hormone (AMH). The muscle then produces the MIS that travels to the ovaries to prevent the cat from entering estrus (colloquially known as “heat”).

“This is intended to be a single lifetime injection,” Briggs said. “That’s what has been so elusive in this research quest, because it’s really difficult to produce lifetime effects. Most approaches need to be ‘boostered’ in some way, and in this case, the gene transfer method is essentially self-boosting.”

And to dispel any apocalyptic speculation: The transferred gene is not integrated into the cell’s DNA. It sits inside the targeted cells – in this case, feline leg muscle cells – producing a protein continuously throughout that cell’s life. This may result in lifetime sterility.

ACC&D is seeking not just a successful product, but to provide alternatives for people who have difficulty accessing care for their pets, as well as for community cats. “This can include challenged pet owners who have difficulty with transportation to surgery, or with affording surgery,” Briggs said. “We’re driven to provide sterilization as a lifesaving mechanism in places and circumstances where that’s difficult to accomplish.”

New Research Made Possible Through Collaboration

This scientific research was the product of a longtime investment of funding and collaboration between the MFAF and their grantees Drs. Patricia Donahoe and David Pepin at Massachusetts General Hospital. MFAF has so far pledged $75 million to the search for a non-surgical sterilization method for cats and dogs, and they are committed to creating an option that’s extremely affordable.

“Access and affordability are critical,” said Briggs. “I can’t share anything now about the anticipated price, but the intent is to make it very affordable. And I know Dr. Michelson has both a commitment to making this widely available and to supporting it financially through launch and a scale up period.”

She continued, “They’ve [MFAF staff and consultants] also pledged to take the technology through the regulatory approval process. That will involve studying the safety of the procedure over the years that are required by the FDA for a claim of permanent sterility. It will also let us study whether it will suppress the hormones that can cause health problems in intact female dogs and cats.”

If that sounds like it is still a number of years in the future, it is. However, the ACC&D expects to be able to release more positive information within the next year. “I wish I could say it was, it was a much, much shorter timeline to introduction,” said Briggs, “but the good thing is we have something that is so, so promising, on the horizon.”

Learn more about this and other research into non-surgical sterilization at