In a development that’s catching the attention of doctors and researchers alike, an anti-parasitic medication originally used to treat infections has shown unexpected promise as a cancer therapy. A patient once diagnosed with terminal cancer responded so well that scans revealed significant tumour regression — a result far beyond what was expected from standard care.
The story underscores a growing interest in drug repurposing: the idea that medications already on pharmacy shelves might be redeployed to fight cancer, potentially offering faster, cheaper access to new treatments. While the research is still early and the sample sizes small, scientists are cautiously optimistic. Here’s what we know so far.
What happened?
A patient with terminal cancer — after exhausting standard treatment options — was treated with the anti-parasitic drug in question. According to medical reports, the tumour burden shrank markedly after treatment, sparking excitement that a familiar drug might have a new role in oncology.
What makes this even more intriguing is that early laboratory and animal studies suggest the drug affects cancer in more ways than one: it appears to interfere with cancer cell metabolism, induce stress or death in tumour cells, and even activate immune responses that help the body fight the tumour. In other words, it may act both directly on the cancer and indirectly by boosting the immune system.
Why this matters
Developing a brand-new cancer drug can take years — often a decade or more — and costs billions of dollars. But repurposing an existing drug offers several advantages:
The safety profile is largely known (for its original indication).
The cost of development can be significantly lower.
Access to off-the-shelf medications may speed delivery to patients in need.
Researchers have long noted that many anti-parasitic or anti-infective drugs share biological features with cancer cells: cancer cells divide quickly, re-wire metabolism, evade immune attack and even exploit processes similar to parasitic invaders. This theoretical overlap opens the door for repositioning such drugs for oncology.
For example, one anti-parasitic agent called Mebendazole has been shown to block microtubule formation and inhibit glucose uptake in tumour cells — both key vulnerabilities in cancer. And another, Ivermectin, has been found to suppress tumour cell proliferation and activate immune-related pathways in lab studies.
What the mechanisms may be
While the full mechanisms remain under investigation, key ways the drug could be working include:
Disrupting tumour metabolism: Cancer cells often rely on abnormal metabolic pathways (e.g., high glucose uptake, altered mitochondrial function). Some anti-parasitic drugs seem to target these vulnerabilities.
Inducing cell death or arresting growth: Drugs like mebendazole interfere with the microtubule network (a structure required for cell division) and trigger apoptosis or other forms of programmed cell death.
Activating immune responses: Some studies suggest these drugs may turn “cold” tumours that evade immune detection into “hot” tumours by recruiting immune cells. For instance, ivermectin combined with immune checkpoint inhibitors converted poorly immunogenic breast tumours into T-cell-rich ones in animal tests.
Suppressing tumour micro-environment/invasion/angiogenesis: Some anti-parasitic drugs appear to reduce blood vessel formation in tumours and inhibit pathways that allow metastasis.
Key cautions & what we don’t know
At present, only a few cases or small-scale studies show tumour regression using anti-parasitic drugs. Large-scale, randomized human clinical trials are lacking.
Because these drugs were not designed originally for cancer, optimal dosing, side-effect profiles in the oncology setting, and combination with other therapies remain unclear. Some anti-parasitic drugs have known risks when used long-term or at higher doses.
Tumour types vary widely: what works for one kind of cancer may not for another. Preclinical success does not guarantee human benefit.
There is a risk of premature hype: social media sometimes latches onto off-label use of anti-parasitic drugs as “miracle cures” before rigorous evidence is available. (One review warned of this in the context of fenbendazole, for example.)
What’s next?
Researchers are calling for well-designed clinical trials to test repurposed anti-parasitic drugs in cancer patients: determining which drug, dose, tumour type, and combination therapy works best.
Scientists are exploring combination strategies: using the anti-parasitic drug alongside chemotherapy, immunotherapy or targeted therapy to enhance benefit and minimize resistance.
Drug delivery innovation may play a role: for instance, using nanoparticles or targeted carriers to deliver repurposed drug at effective concentrations while reducing side-effects.
Health-economics and accessibility are important: if a cheap, well-known drug can work in cancer therapy, it could improve affordability and equity in global cancer care.
The idea that a drug you might pick up at the pharmacy for a parasitic infection could one day help treat cancer is no longer just science-fiction. While still early, the case of a terminal cancer patient seeing dramatic tumour regression after receiving a repurposed anti-parasitic drug highlights the promise of this strategy.
However: it’s not a green light for wide-scale use yet. Much more research is needed before oncologists will routinely prescribe these drugs off-label for cancer. Patients should not self-medicate with anti-parasitic drugs hoping for a cure — that’s dangerous and unsupported by robust evidence.
What this story does show is that innovation sometimes comes from unexpected places old drugs, new ideas, fresh combinations. The next big breakthrough in cancer treatment may already be sitting on pharmacy shelves — and that makes it a very exciting time for cancer research.
Sources:
Li Y-Q, Zheng Z, et al. “Repositioning of Antiparasitic Drugs for Tumour Treatment.” PMC, 2021.
Yang Z, et al. “Ivermectin, a potential anticancer drug derived from an antiparasitic.” PMC, 2020.
Rastegar-Pouyani N., Farzin M.A., Zafari J., et al. “Repurposing the anti-parasitic agent pentamidine for cancer therapy.” Journal of Translational Medicine, 2025.
Ioakeim-Skoufa I., Tobajas-Ramos N., et al. “Drug Repurposing in Oncology: A Systematic Review of Randomised Controlled Clinical Trials.” Cancers, 2023.
“Johns Hopkins Study: Anti-Parasitic Drug Slows Pancreatic Cancer in Mice.” Johns Hopkins Medicine News Release, 2021.
“Emerging Perspectives on the Antiparasitic Mebendazole as a Repurposed Agent in Cancer.” PMC, 2022.