Repurposed Drugs for Cancer: What We Know So Far

Many common medicines are being studied as “repurposed drugs” for cancer. These are medications originally approved for other conditions (like parasites, diabetes, pain, or anxiety) that may also affect cancer cell metabolism, growth, or the immune system.

Very important:

Although evidence is emerging these drugs are experimental for cancer. They are not proven cures and should never replace standard treatments like surgery, chemotherapy, radiation, immunotherapy, or targeted therapy.

Below is a brief overview of some of the most talked-about repurposed drugs: mebendazole, ivermectin, CBD, low-dose naltrexone (LDN), and metformin.

Why Repurpose Drugs at All?

• These medicines are already approved for other uses, so we know a lot about their basic safety and dosing in those settings.

• Lab and early clinical studies suggest some of them may:

  • Interfere with cancer cell metabolism

  • Affect mitochondria (the cell’s energy factories)

  • Slow cancer cell growth or help the immune system see cancer more clearly BioMed Central

But most of the evidence so far is from test tubes, animals, or small early-stage human studies.

Mebendazole

What it is:
Mebendazole is an anti-parasitic drug used for worm infections.

Why it’s of interest in cancer:

• In lab studies, mebendazole can disrupt microtubules (the internal “skeleton” of the cell), which may stop cancer cells from dividing. PMC+1

• It has shown activity in experimental models of brain tumors and colorectal cancer. Nature+2ClinicalTrials+2

Current status:

• A few early clinical trials are testing it in people with aggressive cancers (for example, high-grade gliomas and advanced gastrointestinal cancers).

• We do not yet know which cancers, doses, or combinations (if any) will truly help patients live longer.

Ivermectin

What it is:
Ivermectin is another anti-parasitic drug commonly used for certain infections.

Why it’s of interest in cancer:

• In the lab, ivermectin can affect several cancer-related signaling pathways (such as Wnt/β-catenin, PI3K/Akt/mTOR, and STAT3), leading to:

  • Decreased cancer cell growth

  • Increased cancer cell death (apoptosis)

  • Possible changes in the tumor microenvironment MDPI+1

Current status:

• Most data are preclinical (cells and animals).

• A few early-stage or combination studies are being explored,including for difficult cancers like pancreatic cancer. IIAR Journals

• Safety at the higher or long-term doses used in some experimental protocols is not fully understood.

Cannabidiol (CBD)

What it is:
CBD is a non-intoxicating compound from the cannabis plant.

Why it’s of interest in cancer:

• Lab studies show CBD can:

  • Reduce cancer cell growth and spread

  • Promote cancer cell death in certain models PMC+1

• Clinical research in humans so far has focused more on symptom management—pain, nausea, anxiety, sleep—and some quality-of-life outcomes. Frontiers

What major guidelines say:

• Oncology guidelines note that cannabis and CBD can help some cancer-related symptoms, but evidence that CBD treats the cancer itself in humans is still limited. Cancer Research UK+1

• High-dose CBD (for example ≥300 mg/day) is not recommended outside clinical trials for cancer symptom control because of limited data and potential drug interactions. ASC Publications

Low-Dose Naltrexone (LDN)

What it is:
Naltrexone is a medication traditionally used at higher doses to help with alcohol or opioid dependence.
Low-dose naltrexone (LDN) usually means about 1.5–4.5 mg per day (much lower than addiction-treatment doses).

Why it’s of interest in cancer:

• LDN may modulate the immune system by briefly blocking certain opioid receptors, which can increase the body’s own endorphins and immune activity later. ScienceDirect+1

• Lab work suggests LDN may:

  • Slow cancer cell growth

  • Affect genes related to cell cycle and immune function Spandidos Publications+1

Current status:

• Evidence in cancer is mostly from preclinical studies, case reports, and small observational series.

• Larger, well-designed clinical trials are still needed before LDN can be considered a standard cancer therapy.

Metformin

What it is:
Metformin is a widely used, inexpensive medication for type 2 diabetes.

Why it’s of interest in cancer:

• Metformin affects how cells handle glucose and energy (AMPK and mTOR pathways) and may make cancer cells less able to grow, especially in high-insulin environments. Diabetes Journals+1

• Earlier observational studies suggested people with diabetes on metformin had lower rates of some cancers, but many of these studies had important biases. PMC+1

What newer research shows:

• A 2022 meta-analysis of randomized trials found no clear overall reduction in cancer-related deaths with metformin compared with no metformin, though there may be benefits in some specific cancers and mixed results in others. BioMed Central

• Ongoing studies are testing metformin as an add-on in cancers like colon and breast cancer, especially where metabolism and insulin signaling might play a role. Business Insider+1

Other Repurposed Drugs Under Study

Researchers are also looking at other everyday medicines, such as:

• Aspirin and other anti-inflammatories

• Statins (cholesterol-lowering drugs)

• Beta-blockers

• Various antifungals and antibiotics

These are being investigated because they may affect inflammation, blood supply to tumors, or cell signaling. However, like the drugs above, most are not yet proven as cancer treatments in large, definitive trials. BioMed Central

Key Take-Home Points for Patients

1. Promising and evidence based but not proven

   • Mebendazole, ivermectin, CBD, LDN, metformin, and other repurposed drugs show interesting laboratory and early clinical signals, but they are not established cures.

2. Should not replace standard treatment

   • Skipping surgery, chemotherapy, radiation, immunotherapy, or targeted therapies in favor of unproven alternatives can reduce survival and chances of remission.

3. Possible risks and interactions

   • These drugs can interact with chemotherapy, immunotherapy, blood thinners, liver or kidney function, and other medications.

   • Doses used in cancer experiments may be very different from standard doses.

4. Best used in clinical trials or under specialist supervision

   • The safest and most useful way to explore repurposed drugs is within a clinical trial or with a cancer specialist experienced in integrative/functional oncology who can monitor labs, imaging, and interactions.

5. Always discuss with your oncology team

   • Before starting any of these medications or supplements on your own, talk with your oncologist or integrative cancer doctor so your care is coordinated and safe.

     Contact Valley Integrative Health Today.

     
     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.