One day, a dog named Scout might save your child’s life.

It’s not a stretch. In fact, that possibility is fast becoming reality thanks to a bold new approach to fighting cancer—one that begins in the veterinary clinic and ends, potentially, in the pediatric oncology ward.

The disease in question is osteosarcoma, a vicious bone cancer that afflicts both dogs and children. In dogs, it’s the most common type of cancer. In humans, it strikes hundreds of young people each year, most often in the long bones of growing teenagers. Treatments haven’t improved in decades. Survival rates for metastatic cases are still grim.

But in the space between species, researchers are finding new hope.

Following positive results from an immune therapy in dogs with bone cancer, the same therapy has now been fast-tracked for use in children affected by this deadly cancer.

Dogs, Kids, and Cancer’s Genetic Code

At the center of this medical cross-species collaboration is a New York-based biotech company called OS Therapies. In 2025, the company launched a veterinary-focused subsidiary, OS Animal Health, after reporting promising results from clinical trials of a new drug called OST-HER2 in dogs with osteosarcoma.

The concept they’re betting on is known as comparative oncology. It’s a growing field that uses naturally occurring cancers in pets—especially dogs—as models for studying and treating similar human cancers.

“It has been my dream since founding the company that OST-HER2 could potentially change the standard of care in osteosarcoma, potentially limiting the need for amputation or surgical resection of the primary tumor,” said Paul Romness, OS Therapies’ CEO and President. “With today’s data, we believe we are taking the first steps towards this.”

The data he refers to comes from a trial in which dogs with limb osteosarcoma received the experimental immunotherapy instead of—or in addition to—traditional treatment. The results were striking. OST-HER2 slowed tumor growth, delayed or prevented amputation, and extended survival. Most importantly, it provided a strong proof-of-concept for applying the same therapy to children.

A Bacterial Trojan Horse

OST-HER2 is not a typical chemotherapy. It’s an immunotherapy—one that trains the body’s immune system to seek and destroy cancer cells expressing a protein called HER2. This receptor, when overproduced by tumor cells, turbocharges their growth. It’s well-known in breast and esophageal cancers but also appears in osteosarcoma.

To deliver its genetic payload, OST-HER2 uses a genetically modified version of Listeria monocytogenes, a bacterium more often associated with food poisoning than cancer cures. Inside the body, the modified Listeria sneaks into immune cells, triggering a potent response against HER2-expressing tumors.

The strategy appears to work. In canine trials, not only did the tumors shrink, but the cancer’s spread to the lungs—a common and deadly development in osteosarcoma—was slowed.

“The strong safety profile shown in this study also supports the use of OST-HER2 in this incredibly difficult-to-treat population that has no currently approved therapies,” Robert Petit, Ph.D., OS Therapies’ Chief Medical and Scientific Officer, said in a press release.

From Kennel to Clinic

Dogs are also victims of the disease in their own right. Around 40,000 dogs in the U.S. are diagnosed each year. Most face grim options: amputation, chemotherapy, or both. Even with treatment, survival times are often counted in months.

But the canine trial, published in Molecular Therapy, suggests OST-HER2 could offer a less invasive, more targeted approach. It’s a potentially transformative moment—for pets and people alike.

Encouraged by the data, OS Therapies fast-tracked development of OST-HER2 for pediatric use. In January 2025, the company reported positive results from a Phase 2b clinical trial in young people aged 12 to 39 who had undergone surgical removal of metastatic tumors in the lungs. The drug significantly improved 12-month event-free survival compared to historical controls.

That’s a rare ray of hope in a disease that stubbornly resists progress.

OST-HER2 has now received Fast Track, Orphan Drug, and Rare Pediatric Disease designations from the FDA. If approved, the company will also receive a valuable Priority Review Voucher—recent sales of which have fetched as much as $155 million.

“We are laser-focused on getting an Accelerated Approval for OST-HER2 in recurrent, fully resected, lung metastatic human osteosarcoma by year-end 2025,” Romness said.

A New Standard of Care?

Comparative oncology has been around for decades, but only recently has it started to gain momentum as a translational research tool. Studies in dogs are cheaper and faster than human trials, yet they provide insights that mouse models often can’t. Pets live in the same environments we do. Their immune systems react in ways more similar to ours than lab-bred animals.

As highlighted in the PBS documentary Shelter Me: The Cancer Pioneers, this approach doesn’t just blur the boundary between human and animal medicine—it redefines it.

For families facing osteosarcoma, both human and canine, OST-HER2 may offer something rare: a gentler option. A better outcome. A little more time.