Mebendazole: A Repurposed Drug Emerging For Cancer Treatment?
1. What is mebendazole?
Mebendazole (MBZ) is a long-used oral anti-helminthic (anti-worm) drug with a generally good safety profile, low cost, and decades of clinical use.ecancer+1
It has relatively poor oral bioavailability but, with repeated dosing, blood and tissue levels can reach the low micromolar range and it can cross the blood–brain barrier.ecancer+1
2. Proposed anti-cancer mechanisms
Across the ReDO paper and the Cancers review, MBZ appears to act on multiple cancer pathways:
Microtubule inhibition / mitotic arrest
Binds to the colchicine site on β-tubulin, depolymerizes microtubules, causes G2/M arrest and apoptosis in many tumor cell lines.ecancer+1
Pro-apoptotic effects
Triggers cytochrome-c release and caspase activation (3, 7, 8, 9), Bcl-2 phosphorylation, reduced XIAP, and DNA damage signaling.PMC
Anti-angiogenic activity
Inhibits endothelial cell proliferation, migration and tube formation; interferes with VEGF/bFGF signaling and VEGFR2.PMC
Kinase and pathway inhibition
Inhibits several oncogenic kinases (e.g., BRAF, BCR-ABL, FAK, DYRK1B) and Hedgehog signaling in some models, and can radiosensitize tumors.PMC+1
Effects on cancer stem cells and microenvironment
Reduces ALDH1⁺ cancer stem–like cells, decreases mammosphere formation, and modulates immune cells (e.g., shifts macrophages toward an M1-like phenotype).PMC+1
Overall, MBZ is portrayed as a “multi-target” drug that can hit proliferation, angiogenesis, metastasis, chemoresistance pathways, and tumor-promoting immune cells simultaneously.
3. Pre-clinical evidence
In vitro and animal studies show:
Growth inhibition and apoptosis in a wide range of cancer cell lines:
non-small cell lung, colon, breast, ovarian, melanoma, glioblastoma, medulloblastoma, adrenocortical cancer, gastric and ovarian cancers, head & neck, meningioma, and others, often at sub-micromolar IC₅₀ values, with relative sparing of normal cells.ecancer+1In mouse models, oral MBZ (typically 25–100 mg/kg) reduces primary tumor growth, decreases metastatic spread, inhibits angiogenesis, and prolongs survival in glioma, medulloblastoma, melanoma, adrenocortical and other tumor models.ecancer+1
Synergy is reported with radiation and several chemotherapies (e.g., temozolomide, vincristine/carboplatin, irinotecan, anti-HER2 conjugates), suggesting a role as a chemo-/radiosensitizer.PMC+1
4. Human data and clinical trials
Case reports (both papers discuss the same two cases):ecancer+1
Metastatic adrenocortical carcinoma: patient with progressive disease despite multiple therapies received MBZ 100 mg twice daily; liver metastases regressed or stabilized for ~19 months with improved quality of life and no major side effects, before progression.
Metastatic colon cancer: 74-year-old with multi-site progression after standard chemotherapy started MBZ 100 mg twice daily; after 6 weeks, near-complete remission in lung/lymph-node metastases and partial liver response. Temporary discontinuation for reversible liver enzyme elevation; later progression when MBZ was stopped.
Clinical trials (Table 2 of the Cancers review):PMC
Ongoing/registered studies are mainly early-phase and include:
Phase I high-grade glioma: standard therapy + MBZ (dose-finding).
Pediatric medulloblastoma/high-grade glioma: MBZ monotherapy (dose-finding).
Pediatric gliomas: MBZ with vincristine/carboplatin/temozolomide or bevacizumab/irinotecan.
Phase II GI cancers and “cancer of unknown primary”: MBZ dose-escalation and PK study.
Phase II “real-world” metastatic/advanced cancers: MBZ combined with metformin, doxycycline, and atorvastatin.
Phase II stage IV colorectal cancer: MBZ with adjuvant FOLFOX + bevacizumab.
As of these publications, no completed randomized clinical trials had yet demonstrated clear survival benefit in humans.
5. Safety considerations
Long clinical experience as an anti-helminthic suggests generally low toxicity; common adverse effects are mild GI symptoms and rash.ecancer+1
At high or prolonged doses, rare serious toxicities have been reported (e.g., bone-marrow aplasia, granulomatous hepatitis), and hepatotoxicity or cytopenias remain concerns for oncology-level dosing.PMC+1
6. Overall conclusion from these papers
Mebendazole has broad, multi-target anti-cancer activity in pre-clinical models, with attractive features for repurposing: oral administration, low cost, long track record in humans, and ability to cross the BBB.PMC+1
Evidence in humans is still limited to a few case reports and ongoing early-phase trials, so MBZ is not an established cancer treatment; its use should be confined to clinical trials or carefully monitored off-label use in research settings.
The authors of both papers argue that MBZ is a promising candidate for drug repurposing in oncology, particularly for difficult, resistant, or CNS tumors, and call for more well-designed clinical trials to define efficacy, optimal dosing, combinations, and long-term safety.PMC+1
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Devin Wilson, ND is a licensed Naturopathic Doctor and Owner of Valley Integrative Health, LLC in Ashland, Oregon. With over a decade of clinical experience including 2 years of training with a John’s Hopkin’s/Yale Medical Doctor, Dr. Wilson combines naturopathic and modern medicine along with cutting-edge therapies. His enduring goal is to help people re-establish, maintain and optimize their health using a patient-centered and holistic approach.