Jellybean continues to defy expectations. The 5-year-old Labrador retriever mix jumps up and down from her favorite spot on the couch and walks around the living room with such ease, it’s as if she hadn’t ever had metastatic cancer. Her owners, Patricia and Zach Mendonca, still can’t quite believe the miracle. “She’s got a little bit more of a tug to her step,” Patricia says.

Jellybean was diagnosed with bone cancer in her hind leg almost three years ago. Despite amputation and chemotherapy, the cancerous cells quickly spread through her blood to her lungs, as they do in 90 percent of cases in dogs. Survival time at this stage averages two months. “We didn’t have any hopes of curing her,” says Patricia. “We were pretty devastated.”

So in November 2020, the Mendoncas enrolled Jellybean in a clinical trial at Tufts University, about an hour’s drive from their home in Rhode Island in the US. Jellybean was given a trio of pills, at no cost, which the Mendoncas stuffed daily into her favorite chicken-flavored treats. By Christmas, Jellybean’s tumors had begun to shrink, and they haven’t come back since. The response surprised even the vets treating Jellybean, and raised hopes that these drugs could help not just other dogs, but humans too.

Jellybean’s bone cancer, osteosarcoma, also affects people—particularly children and teens. Fortunately, it’s relatively rare: Some 26,000 new cases are diagnosed worldwide each year. The problem is that there haven’t been any new treatments for over 35 years, says veterinary oncologist Amy LeBlanc, and those available aren’t very effective. Osteosarcoma patients have a survival rate of only around 30 percent if cancerous cells spread to other parts of the body.

Canine studies, like Jellybean’s trial, could change all this. Cancers that arise in pet dogs are molecularly and microscopically similar to cancers in people—in the case of osteosarcoma, the similarities are striking. When compared under the microscope, a canine tissue sample and a human tissue sample of a tumor are indistinguishable. But while it’s thankfully rare in humans, osteosarcoma is at least 10 times as common in dogs—meaning there are huge numbers of canine cancer patients out there to help with research and drug testing. “The families and dogs that participate are an important piece of the puzzle in moving this research forward,” says Cheryl London, the veterinary oncologist at Tufts University’s Cummings School of Veterinary Medicine who is treating Jellybean.

Importantly, dogs are not subject to the same federal regulations that limit treatment options for humans; veterinarians are much freer to use existing drugs off-label against diseases for which there aren’t currently good treatments. All told, this makes for quicker and cheaper clinical trials.

Such trials are part of the Cancer Moonshot initiative that US president Joe Biden relaunched last year and for which he has asked Congress to provide an additional $2.8 billion in the 2024 budget. “They’re designed to fill a knowledge gap that is not sufficiently filled by traditional studies in mice or by data that cannot yet be easily gathered in humans,” says LeBlanc, who directs the Comparative Oncology Program at the US National Cancer Institute. The program oversees clinical trials on dogs with cancer, which are carried out by Tufts and 21 other veterinary universities in the US and Canada.