Researchers have reported results from the first-ever clinical trial of a new class of targeted therapy in pet cats with head and neck squamous cell carcinoma (HNSCC) – a cancer which is notoriously deadly and difficult to treat.
The study found that 35% of the cats who received treatment had their disease controlled with minimal side effects, and the drug will likely be effective for humans with head and neck cancers as well.
Daniel Johnson of the University of California, San Francisco, Helen Diller Family Comprehensive Cancer Center, explained: “The study showed us that it’s possible to target a transcription factor that drives oncogenesis, which is something that has been notoriously difficult in the past.
“Also, it demonstrated that pets with head and neck cancers can be a good representation of human disease and that clinical trials in pets may yield more reliable results than tests in mouse models.”
A first-of-its-kind clinical trial
This drug, which was initially conceptualised to treat human head and neck cancers, is the first to target the transcription factor STAT3. STAT3 is present in a range of both solid and liquid tumours, including a majority of HNSCC cases.
The idea to test the HNSCC drug on pet cats came from a discussion first author Jennifer Grandis had with her sister, a veterinarian.
Grandis learned that oral cancers like HNSCC in pet cats are extremely difficult to treat and that most animals die within two to three months of diagnosis.
“There is remarkable clinical, histopathologic, and immunologic similarity between feline and human HNSCC,” the authors noted.
Case study: How a pet cat benefited from the trials
One cat who benefited from the trial was a 9-year-old black domestic shorthair named Jak. When he was diagnosed with HNSCC, the veterinarian gave him only six to eight weeks to live.
Jak’s owner, Tina Thomas, said: “We wanted more time with him. When I found out about this clinical trial, I knew I wanted him to be a part of it.”
Jak went for weekly treatments for one month. During that time, his symptoms, mainly a watery eye, greatly improved. He ultimately lived more than eight months after his diagnosis.
“It was meaningful to us because he was here in our lives,” says Thomas. “During that time, my son finished college, and my daughter finished her master’s programme. Jak got to spend one more Christmas with us, and he loved our Christmas tree. He was worth every bit of the effort.”
The targeted therapy exhibited limited side effects
Other than mild anaemia, none of the cats in the trial developed side effects that were attributable to the treatment.
Of the 20 cats enrolled, seven exhibited either a partial response or stable disease during the study period. Among the seven respondents, the average survival time post-treatment was 161 days.
When the investigators examined tumours and blood samples from the cats that underwent treatment, they observed that the compound was working in two ways. It not only blocked the activity of STAT3 but also increased levels of PD-1, a protein associated with an immune response to cancer.
The future of clinical trials with pets
“This study is a great example of how we can think more carefully about spending our very limited resources on studies in lab mice that are not even the best models of human cancers,” Grandis stated.
“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. None of the cats in these trials were harmed, and many of them benefited.”
The researchers suggest that conducting clinical trials in pets can provide a more accurate model of how drugs will work in humans compared to lab mice.
They are currently working with a small biotech company to advance the new compound in clinical trials for both pets and humans.
Johnson concluded: “These animals breathe the same air that we breathe and are exposed to all the things we’re exposed to. Their tumours are much more heterogeneous, which makes them a better mimic of human disease.”
