Breakthrough Cancer Drug Shows Promise for Both Cats and Humans

Jakiro or “Jak,” a 9-year-old black domestic shorthair owned by Tina Thomas sleeps in the sun. Jak was part of a clinical trial testing a new cancer drug for cats with squamous cell carcinoma. He survived more than eight months after taking part in the clinical trial. Photo Credit: Tina Thomas

First clinical trial in cats demonstrates disease control in one-third of patients with aggressive oral cancer

DAVIS, CA, September 4, 2025 — A groundbreaking clinical trial has shown that a new cancer drug originally designed for humans can effectively treat one of the most aggressive cancers in cats, offering hope in both veterinary and human medicine.

Scientists from the University of California, San Francisco and the University of California, Davis successfully controlled disease in 35% of cats with oral squamous cell carcinoma—a cancer so aggressive that most feline patients survive only two to three months after diagnosis. The study results, published August 28, 2025 in Cancer Cell, mark the first clinical trial of its kind and could pave the way for similar treatments in humans with head and neck cancers.

A ‘Gut Punch’ Diagnosis

Tina Thomas knows the devastation of this diagnosis firsthand. When her 9-year-old black domestic shorthair, Jakiro—or “Jak”—was given just six to eight weeks to live, she was crushed.

“It was just a gut punch,” recalls Thomas. “We wanted more time with him.”

That time came through the clinical trial. After receiving weekly treatments for a month, Jak’s symptoms improved dramatically. He went on to live more than eight additional months—long enough to spend another Christmas with his family.

“He loved being under our Christmas tree, and giving him that one more Christmas, which I don’t think he would have had otherwise, just made us feel good,” Thomas said.

Breaking New Ground

For veterinary oncology professor and study co-author Katherine Skorupski of the Department of Surgical & Radiological Sciences at the UC Davis School of Veterinary Medicine, the results represent a career-defining breakthrough in treating what has long been considered an untreatable disease.

“One of the struggles I’ve had my entire career is that cats with this cancer—there is really nothing we can do,” said Skorupski, a professor of clinical medical oncology. “We see these cats, we give the bad news, and we do our best to keep them comfortable until they are euthanized. So the fact that we would have something, anything, that might help these cats is so exciting.”

Traditional treatments like surgery, chemotherapy, and radiation typically prove ineffective against oral squamous cell carcinoma in cats. The new drug offers the first real hope for extending both life and quality of life for affected animals.

Veterinary and Human Medicine Researchers Team Up

The unusual path from human drug development to feline testing came about through a family connection. Jennifer Grandis, American Cancer Society Professor of Otolaryngology at the UCSF School School of Medicine, learned from her veterinarian sister about the challenges of treating oral cancers in cats and saw an opportunity to help both animals and advance human medicine.

“By partnering with veterinary oncologists and doing clinical trials in companion animals, we can learn an enormous amount about how these drugs work while also helping people’s pets,” Grandis explained.

The approach could prove more reliable than traditional mouse models for predicting how cancer treatments will work in humans, Johnson noted.

Targeting the Root of Cancer

The experimental drug works differently from conventional cancer treatments. It specifically targets STAT3, a protein that acts like a faulty switch, continuously telling cancer cells to grow and multiply.

“What’s exciting is that this study shows it’s possible to shut down a protein that drives cancer,” said study co-author Dr. Daniel Johnson from UCSF’s Helen Diller Family Comprehensive Cancer Center,  “That has been notoriously difficult in the past.”

The treatment not only blocked STAT3 activity but also increased levels of proteins associated with the body’s immune response to cancer—suggesting it works on multiple fronts to fight the disease.

Promising Results with Minimal Side Effects

Of the 20 cats enrolled in the trial, seven showed either partial response or stable disease. Among those that responded, cats survived an average of 161 days after treatment—a significant extension for a cancer with such a poor prognosis.

Importantly, the cats experienced minimal side effects, with only mild anemia observed in some patients. No cats were harmed by the treatment, and many clearly benefited.

Looking Ahead

Researchers are now working with a biotechnology company to advance the compound through clinical trials for both veterinary and human patients. The success in cats provides valuable data for developing treatments for humans with head and neck squamous cell carcinomas.

For Skorupski, the future likely involves combining this new drug with other therapies to create even more effective treatment protocols. The breakthrough also highlights the often-overlooked potential for cats to contribute to cancer research.

“Cats, who often don’t get much attention in cancer research, could benefit greatly,” she noted.

The research was supported by the National Institutes of Health and the Center for Companion Animal Health at UC Davis, representing a collaborative effort that could transform cancer treatment for both companion animals and their human families.