New cancer treatment found ‘promising’ for terminally ill dogs

Scientists hope to make plans for clinical trials on human patients in Singapore and Asia Pacific

A new therapy to treat late-stage cancer in dogs can not only extend the lives of canines but also preserve “good quality of life”, according to a new study that may also lead to improved treatments for some cancers that affect humans.

The research, published recently in the journal Stem Cell Research & Therapy, used technology that modified unspecialised stem cells in dogs to treat the cancer-stricken canines.

Scientists, including those from the National University of Singapore (NUS), modified Mesenchymal Stem Cells (MSCs) that are capable of seeking out cancerous tumours.

The modified cells, according to researchers, carry a potent ”kill-switch” – molecules called cytosine deaminase – that produces a high, localised concentration of a cancer killing drug (5-fluorouracil) in the tumour environment and subsequently induces immunity against cancer.

“To repurpose stem cells for cancer treatment, it is usual to use viruses to introduce therapeutic genes into the cells. We have however, designed a non-viral gene delivery platform that introduces a high payload of therapeutic genes into the stem cells, to effectively destroy the out-of-control growing cancer cells,” study co-author Too Heng-Phon from NUS said.

“With this therapy that has been proven safe and demonstrated promising clinical benefits in animal patients, we hope to develop effective treatment options to help human patients with cancer as well, which can improve their health without compromising their quality of life,” Dr Heng-Phon said.

The technology was first tested on canine patients in 2018, and later delivered to 65 dogs, as well as two cats, with cancer conditions like perianal adenoma, lung metastasis, and sarcoma.

Veterinary patients in the study first received the treatment via direct tumour-site injections or through blood stream, followed by the ingestion of oral pills containing a drug commonly used to treat fungal infection (5-flucytosine), over a few days.

The cycle was repeated for two more weeks after about seven days before the first course of treatment was completed.

Researchers then monitored the condition of the animals and repeated the course where necessary.

They say 56 showed signs of positive response among those that received the treatment over a duration ranging from three to eight weeks.

About 14 of these animals, scientists say, showed full recovery from the treatment.

Two animals remained cancer free at least 30 months post treatment, according to the scientists, who added that 46 of the veterinary patients overall showed good quality of life over two to 32 months, with the treatment.

There were no significant side effects observed during the study likely due to the localised presence of the therapeutic cells which remain within the tumour environment, researchers say.

“Beyond results that have shown to benefit our companion animals, it is our hope to extend the therapy to human patients in the future and improve healthcare outcomes for those who have cancer – especially when they have no treatment options left,” Ho Yoon Khei, another author of the study, said.

In further studies, scientists hope to review the therapy’s safety and efficacy for veterinary medicine and discuss plans for clinical trials on human patients in Singapore and the Asia Pacific region.