A Common Canine Dewormer's Surprising Fight Against Canine Cancer

For decades, ivermectin was known as one thing: a highly effective antiparasitic drug used to deworm dogs, livestock, and humans worldwide. But in 2019, a team of researchers made a striking discovery — this humble drug appeared to stop canine cancerous mammary tumor cells from growing. Published by Diao and colleagues, the study was the first of its kind to directly test ivermectin against canine cancer cells in a laboratory setting. Their findings were remarkable. Ivermectin disrupted two of the key biological switches that cancer hijacks to grow and spread: the WNT signaling pathway, which acts like a gas pedal for tumor growth, and the cell cycle checkpoint that controls when cells are allowed to divide. Importantly, ivermectin appeared to target cancer cells preferentially leaving normal, healthy cells relatively unaffected — and when tested in live tumor models, it suppressed tumor growth without causing liver or kidney damage, a critical finding for any drug being considered for real-world use in dogs.

What made subsequent research compelling was just how many ways ivermectin appears to attack cancer at once – from sabotaging the internal scaffolding of cancer cells to cutting off cancer's fuel supply, a phenomenon known as the Warburg effect. And it appears to reactivate p53 — a built-in cellular alarm that many cancers survive by silencing. Each of these alone would be noteworthy. Together, they paint a picture of a drug hitting cancer in dogs from several directions simultaneously.

Perhaps the most tantalizing finding came from research into cancer stem cells that conventional treatment in dogs so often leaves behind. While surgery and chemotherapy can eliminate the bulk of a tumor, these resilient cancer stem cells are capable of self-renewal and are frequently drug-resistant, making them the primary driver of relapse and metastasis. Ivermectin appears to go after stem cells directly, preferentially targeting cancer stem cell populations in a way that standard chemotherapy does not — and in breast cancer models in dogs, outperforming paclitaxel, one of the most widely used chemotherapy drugs in the world, on this specific measure. If this property holds in clinical settings — and that remains to be proven — it would mean ivermectin doesn't just fight the tumor you can see; it may eliminate the very cells responsible for relapse. The dog, as it turns out, has long been one of veterinary medicine's most under-appreciated research partners.

Disclaimer

This information is for educational purposes only and is not intended to replace the advice of a qualified veterinarian.

Virex Health/Virogex Inc.