Repurposed Drugs for Cancer: Evidence Hub, Drug Profiles and Clinical Trials (2026)

SmartCancer Research Hub | Updated November 3, 2026 | Evidence-led oncology research

Can existing medicines developed for infections, diabetes, cardiovascular disease or other conditions be repurposed to help treat cancer?

Drug repurposing, also called drug repositioning, is an important area of oncology research. Scientists are investigating whether established medicines can influence cancer-related mechanisms, improve responses to existing treatments, reduce recurrence or help address treatment resistance.

Some candidates have reached randomized clinical trials. Others remain at the laboratory or early clinical research stage. A drug that affects cancer cells in a laboratory does not necessarily produce meaningful clinical benefits in people.

Our central principle

Conventional cancer treatment remains the foundation of evidence-based oncology. Repurposed drugs for cancer are research candidates or, in selected circumstances, clinician-supervised off-label interventions. They should not replace established surgery, radiotherapy, chemotherapy, targeted therapy or immunotherapy.

Explore the Repurposed Cancer Drug Research Library

Use this hub to navigate drug-specific reviews, cancer research, biomarker hypotheses, clinical trials, evidence assessments and safety information.

1. Drug Profiles

Investigate individual medicines, their original indications, pharmacology and proposed anticancer mechanisms.

Explore drug directory

2. Clinical Evidence

Understand randomized trials, observational research, case reports and laboratory findings.

Explore evidence framework

3. Cancer Biomarkers

Explore relationships between drug candidates, molecular pathways, tumor metabolism and biomarkers.

Explore biomarker research

4. Clinical Trial Tracker

Follow registered studies, trial phases, recruitment status and published outcomes.

Explore clinical trials

5. Safety and Interactions

Understand drug toxicity, liver safety, interactions and the risks of combining medications.

Explore safety resources

6. Patient-Reported Cases

Examine published and compiled patient experiences while distinguishing anecdotes from clinical evidence.

Explore case research

What Are Repurposed Drugs for Cancer?

Repurposed drugs are existing medicines originally developed or approved for one medical indication that are investigated for a different purpose, such as cancer treatment.

Cancer hallmarks targeted by repurposed non-oncology drugs. Figure created with Biorender.com. Source: Nature (Signal Transduction and Targeted Therapy), 2024.

For example:

• Metformin was developed for the management of type 2 diabetes.
• Ivermectin was developed as an antiparasitic medicine.
• Mebendazole is a human antiparasitic medicine.
• Fenbendazole is a veterinary antiparasitic medicine.
• Atovaquone is an antimicrobial medicine.
• Propranolol is a beta-blocker used in cardiovascular and other conditions.
• Aspirin is an analgesic and antiplatelet medicine being investigated in selected cancer settings.

The scientific rationale is that some drugs have biological effects beyond their original intended use. These effects may influence cancer-associated pathways, including cellular metabolism, inflammation, angiogenesis, mitochondrial function and immune signaling.

However, demonstrating a mechanism is only the beginning of drug development. Researchers must establish whether the drug reaches the tumor at a tolerable concentration, affects the relevant biological target, and improves meaningful outcomes in patients.

Evidence at a Glance: What Do We Know?

Not all repurposed cancer drugs have the same level of supporting evidence. The following examples illustrate why individual clinical trials must be evaluated rather than relying on broad claims that a particular drug fights cancer.

Positive randomized-trial signal in a defined setting

Aspirin and PI3K-Altered Colorectal Cancer

The ALASCCA randomized phase III trial, published in the New England Journal of Medicine in 2025, found a lower risk of colorectal cancer recurrence with aspirin in patients whose resected tumors carried selected alterations in the PI3K signaling pathway.

The results support further clinical consideration of biomarker-selected aspirin strategies. They do not demonstrate that aspirin is an anticancer treatment for every colorectal cancer patient or for other cancer types.

Read the ALASCCA trial

Negative phase III evidence

Metformin

The MA.32 randomized clinical trial enrolled 3,649 patients with early breast cancer without diabetes. Adding metformin to standard treatment did not significantly improve invasive disease-free survival.

This is an important example of promising biological and observational findings failing to translate into a clinical benefit in a large randomized trial.

Read the MA.32 study

Mixed clinical evidence

Statins

Statins have attracted interest because of their effects on cholesterol synthesis, inflammation and cellular signaling. However, randomized oncology evidence has not demonstrated consistent overall improvements in cancer survival outcomes across studied settings.

Read the randomized-trial systematic review

Early-stage research

Mebendazole

Mebendazole has demonstrated anticancer activity in laboratory and animal models. Human research has included early clinical studies, but clinical benefit remains unestablished. One early gastrointestinal cancer trial was terminated for lack of effect.

Review the terminated RepoMeb study

Investigational

Ivermectin

Ivermectin is being investigated for effects on cancer-related signaling, cellular metabolism and immune pathways. A phase I/II study is evaluating ivermectin with immune checkpoint inhibitors in metastatic triple-negative breast cancer.

This remains experimental research, not proof of treatment efficacy.

Review the clinical trial

Preclinical evidence

Fenbendazole

Fenbendazole has attracted attention because of proposed effects on microtubules and cellular glucose metabolism. Most anticancer evidence remains preclinical. It is not approved for human use, and liver injury has been reported.

Read the NIH LiverTox assessment

Repurposed Cancer Drug Directory

The SmartCancer drug directory is organized according to the original pharmacological class of each candidate. Each profile should distinguish laboratory findings from human clinical evidence.

1. Antiparasitic and Anthelmintic Drugs

• Fenbendazole: Veterinary benzimidazole; experimental anticancer mechanisms involving microtubules and cellular metabolism.
• Mebendazole: Human anthelmintic; investigated for tubulin disruption, angiogenesis and brain tumor research.
• Ivermectin: Antiparasitic medicine; experimental research involving signaling pathways and immune modulation.
• Albendazole: Human anthelmintic; investigated for microtubule-related and other anticancer effects.
• Niclosamide: Anthelmintic medicine; investigated for Wnt, STAT3 and other signaling pathways.
• Pyrvinium pamoate: Antiparasitic compound with experimental activity involving Wnt signaling and cellular metabolism.
• Artesunate: Antimalarial derivative being investigated for oxidative stress-related anticancer mechanisms.

2. Metabolic and Mitochondrial Modulators

• Metformin: AMPK and insulin-related metabolic effects.
• Atovaquone: Mitochondrial complex III inhibition and tumor oxygenation research.
• Disulfiram: Investigated with copper in cancer-related pathways and protein degradation.
• Doxycycline: Investigated for mitochondrial protein synthesis and cancer stem-cell-related hypotheses.
• Berberine: Experimental metabolic and signaling research; evidence and regulatory status differ from approved medicines.

3. Cardiovascular and Anti-Inflammatory Drugs

• Aspirin: Platelet inhibition and selected PI3K-pathway-altered colorectal cancer research.
• Statins: HMG-CoA reductase inhibition, mevalonate pathway and tumor signaling research.
• Propranolol: Beta-adrenergic signaling, stress response and angiogenesis hypotheses.
• COX-2 inhibitors: Inflammatory signaling and prostaglandin-related research.
• Cimetidine: Histamine receptor effects and historical colorectal cancer research.

4. Other Drug Candidates

• Itraconazole: Hedgehog signaling and angiogenesis-related research.
• Fluvoxamine and other antidepressants: Experimental research into cellular signaling and drug repurposing.
• Naltrexone: Low-dose naltrexone research in immunological and cancer-related settings.
• Melatonin: Circadian regulation, oxidative stress and supportive oncology research.

The inclusion of a drug in this directory indicates research interest, not established effectiveness, an endorsement or a recommendation to use it.

Cancer Biomarkers and Precision Drug Repurposing

A central question in precision oncology is whether a drug's biological mechanism is relevant to a specific tumor phenotype.

Rather than asking which repurposed drug is best for cancer generally, researchers should ask whether a particular molecular alteration, metabolic characteristic or tumor microenvironment feature could make a drug biologically relevant.

This is the difference between generic repurposing and precision drug repurposing.

Research Areas

• PI3K / PIK3CA / PTEN: Aspirin research in selected colorectal cancer populations.
• AMPK / mTOR: Metabolic signaling research involving metformin.
• Wnt / beta-catenin: Experimental research involving ivermectin and niclosamide.
• Microtubule dynamics: Benzimidazole-related research involving mebendazole and fenbendazole.
• Mitochondrial complex III: Atovaquone and tumor oxygenation hypotheses.
• STAT3 signaling: Experimental niclosamide-related research.
• Beta-adrenergic signaling: Propranolol and the tumor stress-response environment.

Important biomarker distinction

A laboratory pathway association does not establish a clinically validated predictive biomarker. A marker becomes clinically useful for drug selection only when supported by appropriate human evidence and a clinically validated testing strategy.

Featured Precision Oncology Research

• Cancer Biomarker Map: Fenbendazole, Mebendazole, Ivermectin, Niclosamide and Atovaquone
• Repurposed and Alternative Cancer Interventions: Evidence-Ranked Analysis

Repurposed Cancer Drug Clinical Trial Tracker

ClinicalTrials.gov and other official registries are essential resources for verifying whether a repurposed medicine has progressed beyond laboratory studies.

A registered clinical trial does not mean that a treatment works. Recruitment status, trial phase, patient population, study completion and published results must all be examined.

Selected Research Studies

1. ALASCCA: Aspirin in PI3K-Altered Colorectal Cancer

Trial ID: NCT02647099

Research: Aspirin following surgery in selected colorectal cancer patients with PI3K-pathway alterations.

Status: Results published in 2025.

ClinicalTrials.gov record

2. Ivermectin and Immunotherapy in Metastatic Triple-Negative Breast Cancer

Trial ID: NCT05318469

Phase: I/II.

Research: Ivermectin combined with balstilimab or pembrolizumab.

Registry status: Recruiting in the August 2026 registry update. Check the current record for any subsequent changes.

ClinicalTrials.gov record

3. RepoMeb: Mebendazole in Gastrointestinal Cancer

Trial ID: NCT03628079

Phase: I/II.

Research: Mebendazole in advanced gastrointestinal cancer and cancer of unknown primary.

Status: Terminated for lack of effect. No results posted in the registry.

ClinicalTrials.gov record

4. Mebendazole as Adjuvant Treatment for Colon Cancer

Trial ID: NCT03925662

Phase: III, according to the registry record.

Research: Mebendazole alongside an established colorectal cancer treatment regimen.

Registry caution: The record displays recruiting, but its last posted update is April 2019. Current activity and recruitment should be confirmed directly with the investigator or study site.

ClinicalTrials.gov record

Search for Additional Studies

• Search repurposed cancer drug studies
• Search fenbendazole cancer research
• Search ivermectin cancer trials
• Search mebendazole cancer trials
• Search metformin cancer trials

Patient-Reported Cases and Real-World Observations

Patient experiences have contributed to public interest in repurposed drugs, particularly fenbendazole, ivermectin and mebendazole.

Case reports and patient-reported outcomes can generate research questions. They can sometimes identify unexpected responses or possible safety signals. However, they cannot independently establish that a drug caused a remission or prolonged survival.

Important limitations include:

• Concurrent chemotherapy, radiotherapy, surgery or immunotherapy.
• Incomplete medical records and missing baseline information.
• Selective reporting of positive outcomes.
• Missing information about cancer stage, histology and biomarkers.
• Survivorship and publication bias.
• Unverified imaging, pathology and treatment-response assessments.
• Inconsistent follow-up and definitions of remission.

For transparency, our patient-reported case compilation is presented as a research-literature mapping exercise, not a clinical outcomes study and not proof of effectiveness.

Read: Fenbendazole, Ivermectin and Mebendazole for Cancer — Patient-Reported Case Compilation (October 2026 Update)

Safety, Drug Interactions and Regulatory Considerations

An established medicine is not automatically safe when used at a different dose, for a different condition or in combination with anticancer treatment.

Important considerations include:

• Liver toxicity: Some repurposed medicines can cause elevations in liver enzymes or clinically significant liver injury.
• Drug metabolism: Medicines may influence CYP enzymes, transport proteins and the metabolism of other drugs.
• Bleeding risk: Aspirin and other agents affecting platelet function may increase bleeding risk.
• Cardiovascular effects: Blood pressure, heart rate and cardiac rhythm may be affected by some repurposed medicines.
• Immune interactions: Combining experimental agents with immunotherapy requires careful clinical evaluation.
• Dosage and formulation: A dose used for an original medical condition cannot automatically be translated into an anticancer dose.
• Product quality: Veterinary formulations and products obtained outside regulated pharmaceutical channels may have different quality and safety characteristics.

Specific warning: Ivermectin and Fenbendazole

On June 17, 2026, the American Society of Clinical Oncology reported that ivermectin and fenbendazole should not be used to treat cancer or as adjuncts to established cancer therapies outside the safeguards of a well-designed clinical trial.

The notice highlighted the lack of established clinical benefit, potential toxicity and harmful drug interactions.

Fenbendazole is a veterinary medicine and is not approved for human use.

Read the ASCO clinical notice

Patients should disclose all prescription medicines, non-prescription drugs, supplements and experimental treatments to their oncology team. No medication should be added, stopped or substituted without appropriate clinical review.

SmartCancer Evidence Grading Framework

Every drug profile should distinguish evidence quality, clinical relevance and the exact cancer setting being studied.

SmartCancer uses the following editorial E0-E5 evidence framework. These are internal evidence labels, not official regulatory approval categories.

Level	Evidence category	Interpretation
E5	Replicated randomized trials and high-quality systematic reviews	Strong clinical evidence in a defined setting; assess guideline adoption.
E4	Well-designed randomized clinical trial	Meaningful human clinical evidence, but confirmation or external validation may be needed.
E3	Prospective clinical research and early controlled trials	Promising or informative clinical research, not necessarily proof of efficacy.
E2	Observational studies and retrospective cohorts	Clinical associations vulnerable to confounding and selection bias.
E1	Case reports and case series	Hypothesis-generating clinical observations.
E0	Cell studies, animal models and mechanistic hypotheses	Preclinical evidence only; no established human clinical benefit.

Negative randomized trials must be reported alongside positive findings. A strong negative clinical result should not be ignored simply because lower-level laboratory or observational findings appear encouraging.

The grade should be specific to the drug, cancer subtype, treatment setting, dose studied, biomarker and clinical endpoint. One drug can therefore have different evidence ratings for different cancer indications.

How SmartCancer Evaluates Repurposed Drugs

Our research model follows a consistent pathway:

1. Original indication: What condition was the drug originally developed or approved to treat?
2. Pharmacology: What are its established mechanisms, pharmacokinetics and safety characteristics?
3. Anticancer hypothesis: Which cancer-related pathways might it influence?
4. Preclinical validation: Are findings supported by reproducible cell and animal studies?
5. Clinical evidence: Have human studies demonstrated biological activity or meaningful clinical benefit?
6. Precision relevance: Are there specific cancer types, biomarkers or patient populations that may respond differently?
7. Safety and interactions: What risks emerge when the drug is combined with standard cancer treatment?
8. Clinical translation: Has evidence become strong enough to support a defined clinical indication or guideline recommendation?

Research Priorities: Where Drug Repurposing Could Go Next

1. Biomarker-Guided Drug Selection

Research should move beyond selecting drugs based on broad mechanistic claims. Biomarker-driven trials may help identify patient populations more likely to benefit.

2. Combination Therapy Research

Some investigational drugs may affect pathways involved in treatment resistance. Their potential role alongside chemotherapy, targeted therapy or immunotherapy requires controlled clinical testing.

3. Cancer Metabolism

Metabolic dependencies, mitochondrial function, glucose utilization and tumor hypoxia are important areas for investigating existing medicines in new oncology settings.

4. Cancer Stem Cells and Tumor Resistance

Researchers are investigating whether certain repurposed compounds affect treatment-resistant cell populations. Preclinical findings require careful translation into human studies.

5. AI-Assisted Drug Repurposing

AI can help screen molecular databases, identify potential drug-target relationships, analyze biological networks and generate trial hypotheses. Predictions must still be validated experimentally and clinically.

Questions Patients Should Ask Their Oncologist

• Is this drug being investigated for my specific cancer type and stage?
• Has a randomized clinical trial demonstrated improved survival or recurrence outcomes?
• Is my tumor biomarker profile relevant to the proposed mechanism?
• Could this drug interfere with chemotherapy, targeted therapy or immunotherapy?
• Are there known liver, kidney, cardiovascular or neurological risks?
• Is there an appropriately designed clinical trial available?
• What evidence would justify using this drug outside a clinical trial?

Frequently Asked Questions

What is the most promising repurposed drug for cancer?

There is no universally best repurposed cancer drug. Aspirin has important randomized-trial evidence in a specific group of patients with resected PI3K-pathway-altered colorectal cancer. This does not establish a general role for aspirin in all cancers.

Are repurposed drugs approved cancer treatments?

Some medicines have established cancer indications, and others are investigated for new indications. Regulatory approval is specific to a drug, indication and jurisdiction. Off-label prescribing of an approved human medicine is not the same as regulatory approval for cancer treatment or proof of clinical effectiveness.

Are ivermectin and fenbendazole proven cancer treatments?

No. Both have attracted interest through preclinical research and public discussion, but neither has established clinical benefit as a cancer treatment. ASCO's 2026 clinical notice advises against their use for cancer outside a well-designed clinical trial.

Is mebendazole more promising than fenbendazole?

Mebendazole has an established human antiparasitic indication and a broader history of clinical research than veterinary fenbendazole. Nevertheless, mebendazole has not been established as an effective cancer treatment. Its laboratory findings and early clinical research do not establish a survival benefit.

Does metformin prevent cancer recurrence?

The answer depends on the cancer and clinical setting. The large MA.32 randomized trial did not show improved invasive disease-free survival when metformin was added to standard treatment in patients with early breast cancer without diabetes. Observational studies should not be interpreted as proof of a preventive or therapeutic benefit.

Can repurposed drugs be combined with chemotherapy?

Some combinations are being investigated in clinical trials. Others may create unwanted interactions or additional toxicity. Patients should not combine experimental drugs with cancer treatment without the oncology team's knowledge and approval.

Can laboratory studies prove that a drug cures cancer?

No. Laboratory studies help identify biological mechanisms and generate research hypotheses. Clinical benefit must be demonstrated in properly designed human studies with meaningful outcomes such as overall survival, disease-free survival or progression-free survival.

Where can I find ongoing repurposed cancer drug trials?

ClinicalTrials.gov provides searchable information about registered research. Trial records should be checked for recruitment status, eligibility, study phase, completion dates and published results.

Core SmartCancer Research Library

Continue exploring the SmartCancer and OneDayMD research network:

• Repurposed Cancer Drugs, Integrative and Precision Oncology: 2026 Evidence Guide
• Repurposed and Off-Label Drugs in Cancer: Understanding the Evidence Hierarchy
• Repurposed and Alternative Cancer Interventions: Evidence-Ranked Analysis
• Cancer Biomarker Map: Five Repurposed Drug Candidates
• Ivermectin, Mebendazole, Atovaquone and Niclosamide: Evidence-Based Review
• Fenbendazole, Ivermectin and Mebendazole: Patient-Reported Case Compilation

Scientific References and Research Resources

1. Dhanush Y, Ganesh VS. Non-oncologic to oncologic drug: A systematic review of drug repurposing in cancer. Cancer Chemotherapy and Pharmacology. 2025. PubMed
2. Drug Repurposing in Oncology: A Systematic Review of Randomized Controlled Clinical Trials. Cancers. 2023. PubMed
3. ALASCCA: Low-Dose Aspirin for PI3K-Altered Localized Colorectal Cancer. New England Journal of Medicine. 2025. NEJM
4. MA.32: Effect of Metformin vs Placebo on Invasive Disease-Free Survival in Patients With Breast Cancer. JAMA. 2022. PubMed
5. Antiparasitic Agents in Oncology: Innovative Mechanisms, Emerging Evidence and Clinical Potential in Cancer Treatment. 2026. PubMed
6. ASCO Clinical Notice: Oncologists Urged to Take Proactive Approach When Discussing Ivermectin and Fenbendazole. June 17, 2026. ASCO
7. NIH LiverTox: Fenbendazole. Updated April 20, 2026. NIH Bookshelf

Editorial Policy and Medical Disclaimer

SmartCancer is an independent oncology research and health-information platform. Our editorial objective is to make emerging cancer research understandable while distinguishing established medical evidence from experimental hypotheses.

We do not present laboratory findings, testimonials or unverified patient experiences as proof of cancer treatment efficacy. We aim to identify relevant research, report negative findings and disclose important safety concerns.

This content is educational and is not individual medical advice, a prescription or a recommendation to begin, stop or change cancer treatment. Treatment decisions must be made with qualified healthcare professionals familiar with the patient's diagnosis, pathology, biomarkers, medical history and current medicines.

Repurposed drugs should be considered research candidates unless there is adequate clinical evidence supporting a specific medical indication.

Last updated: November 3, 2026. Clinical trial statuses and scientific evidence change over time. Individual study records and original publications should be checked before relying on research summaries.