Ivermectin

Ivermectin and Cancer: Exploring the Evidence

Key takeaways:

• There is one active study in humans looking at ivermectin in people with breast cancer, but the results are yet to be published. No other studies have been published on ivermectin and cancer in humans. 
• The current laboratory data on ivermectin and cancer can be grouped into two categories: studies using ivermectin alone against cancer cells, and studies using ivermectin as an adjunct (helper) treatment to existing cancer therapies, like chemotherapy, immunotherapy, and radiation
• To copy any of the conditions that produced these laboratory results, ivermectin would have to be given at extremely high doses—higher than the human body can tolerate. In studies testing high doses of ivermectin, people experienced severe neurological side effects.
• Much more research is needed before we know whether ivermectin is effective as a cancer treatment in humans.
• Given the positive results in preclinicaltesting a drug, a procedure, or another medical treatment in isolated cells or in animals; preclinical evidence is considered only an initial indication of possible effects in people experiments and anecdotal stories, it has become a popular drug in social forums as an off-label cancer treatment. 

What is ivermectin?

Ivermectin is an antiparasitic medication. It is produced by bacteria in the Streptomyces genus, the source of several other critical medications, including antibiotics. The biologists who discovered and isolated ivermectin in the early 1970s, Satoshi Omura and William Campbell, received a Nobel prize in 2015 for their work.¹Laing R, Gillan V et al. Ivermectin – Old Drug, New Tricks? Trends in Parasitology. 33 (6): 463–472.

Ivermectin has been hitting headlines in the US since 2020, when a team of researchers published study results showing that ivermectin was highly effective at treating COVID-19.²Elazzar A, Eltaweel A et al. WITHDRAWN: Efficacy and safety of ivermectin for treatment and prophylaxis of COVID-19 pandemic. PREPRINT (Version 3) available at Research Square. 28 Dec 2020. However, the authors of the article had fabricated much of their data, even inventing patients to get the results they wanted. The article was discredited, and further studies have found that ivermectin is ineffective at treating COVID-19.³Lawrence JM, Meyerowitz-Katz G et al. The lesson of ivermectin: meta-analyses based on summary data alone are inherently unreliable. Nature Medicine. 27: 1853–1854.

More recently, online influencers have picked up on preclinical studies (tests done on cultured cells, or in laboratory animals) that have found ivermectin can kill or limit cancer cells to suggest it may be used to fight cancer. While ivermectin is gaining attention in oncology, it has not yet been studied enough to know whether it could fight cancer in humans, and there is reason to be cautious about applying  these laboratory tests to human medicine.

A wonder drug?

Ivermectin was first used to treat parasitic worms in cows and other livestock in the 1980s. Soon after, a scientist at the Merck corporation, Mohamed Aziz, began studying ivermectin for parasitic infections that affect people. These experiments found that ivermectin was extremely effective in treating onchocerciasis, or river blindness, a parasitic worm infection that is one of the world’s most common causes of blindness. Ivermectin is also effective against strongyloidiasis, a life-threatening parasitic infection, and lymphatic filariasis, another parasitic infection causing painful and disabling limb swelling. 

Ivermectin is stable at room temperature and inexpensive. Its widespread use in public health campaigns (about 25 million people receive ivermectin each year) has helped eliminate river blindness in several countries and is estimated to have prevented over 600,000 people from becoming blind.⁴Sturchio JL. The case of ivermectin: lessons and implications for improving access to care and treatment in developing countries. Community Eye Health. 2001;14(38):22-3. Ivermectin is a wonder drug—but not for COVID-19, nor, as far as we yet know, for cancer.

What the evidence says about ivermectin and cancer

The current data on ivermectin and cancer can be grouped into two categories: studies using ivermectin alone against cancer cells, and studies using ivermectin as an adjunct (helper) treatment to existing cancer therapies, like chemotherapy and radiation.

Using ivermectin to kill cancer cells

From an initial survey, ivermectin appears promising in killing cancer cells in the lab. When applying ivermectin solutions to leukemia, pancreatic cancer, and prostate cancer cells in laboratory dishes, it appears that that ivermectin activates the cells’ autophagy (self-breakdown) responses, leading to eventual cell death.⁵Xia Y, Wang D et al. Silencing of tropomodulin 1 inhibits acute myeloid leukemia cell proliferation and tumor growth by elevating karyopherin alpha 2-mediated autophagy. Pharmacology Research. 2024 Sep;207:107327; Li MY, Zhang J et al. Ivermectin induces nonprotective autophagy by downregulating PAK1 and apoptosis in lung adenocarcinoma cells. Cancer Chemotherapy and Pharmacology. 2024 Jan;93(1):41-54; Samy A, Hussein MA, Munirathinam G. Eprinomectin: a derivative of ivermectin suppresses growth and metastatic phenotypes of prostate cancer cells by targeting the β-catenin signaling pathway. Journal of Cancer Research and Clinical Oncology. 2023 Sep;149(11):9085-9104. Bladder cancer, osteosarcoma, and prostate cancer cells treated with ivermectin show more cell death and signs of DNA damage, which leads to apoptosis (cellular self-destruction) if unrepaired,⁶Fan N, Zhang  et al. Ivermectin inhibits bladder cancer cell growth and induces oxidative stress and DNA damage. Anticancer Agents in Medicinal Chemistry. 2024;24(5):348-357; Hu B, Tan H et al. Repurposing Ivermectin to augment chemotherapy’s efficacy in osteosarcoma. Human & Experimental Toxicology. 2022 Jan-Dec;41:9603271221143693; Lv S, Wu Z et al. Integrated analysis reveals FOXA1 and Ku70/Ku80 as targets of ivermectin in prostate cancer. Cell Death and Disease. 2022 Sep 1;13(9):754. as does damage to the mitochondria (the structures responsible for giving a cell energy), which is seen in osteosarcoma cells treated with ivermectin.⁷Hu B, Tan H et al. Repurposing Ivermectin to augment chemotherapy’s efficacy in osteosarcoma. Human & Experimental Toxicology. 2022 Jan-Dec;41:9603271221143693. Laboratory studies show that ivermectin can reduce the activity of several genetic pathways that contribute to tumor growth, including mTOR/STAT3,⁸Lu H, Zhou L et al. Ivermectin synergizes sorafenib in hepatocellular carcinoma via targeting multiple oncogenic pathways. Pharmacology Research & Perspectives. 2022 Jun;10(3):e00954. EGFR,⁹Huang J, Xiao J et al. Overcoming flumatinib resistance in chronic myeloid leukaemia: Insights into cellular mechanisms and ivermectin’s therapeutic potential. Journal of Cellular and Molecular Medicine. 2024 Jul;28(14):e18539; Lombardi Z, Gardini L et al. Importin subunit beta-1 mediates ERK5 nuclear translocation, and its inhibition synergizes with ERK5 kinase inhibitors in reducing cancer cell proliferation. Molecular Oncology. 2025 Jan;19(1):99-113. and PAK1, which are pathways associated with poor prognosis in some cancers.¹⁰Li MY, Zhang J et al. Ivermectin induces nonprotective autophagy by downregulating PAK1 and apoptosis in lung adenocarcinoma cells. Cancer Chemotherapy and Pharmacology. 2024 Jan;93(1):41-54; Chen L, Bi S et al. Ivermectin suppresses tumour growth and metastasis through degradation of PAK1 in oesophageal squamous cell carcinoma. Journal of Cell and Molecular Medicine. 2020 May;24(9):5387-5401.

Using ivermectin to augment cancer treatments

A second area of research is the possible use of ivermectin to enhance the effect of existing cancer treatments. Breast and pancreatic cancer cells treated in a laboratory dish (not in humans) with both ivermectin and recombinant methioninase (an enzyme that inhibits cancer cell growth in the lab by depriving cells of the amino acid methionine) showed more cell death compared to when they were treated with either substance alone.¹¹Morinaga S, Han Q et al. Recombinant methioninase (rMETase) synergistically sensitizes ivermectin-resistant MCF-7 breast cancer cells 9.9 fold to low-dose ivermectin. Anticancer Research. 2025 Feb;45(2):451-455; Morinaga S, Han Q et al. Ivermectin combined with recombinant methioninase (rMETase) synergistically eradicates MiaPaCa-2 pancreatic cancer cells. Anticancer Research. 2025 Jan;45(1):97-103.

Individual lab experiments on drug-resistant cancer cells have found that ivermectin may “resensitize” these cells to certain types of chemotherapy: for example, doxorubicin-resistant breast cancer cells show greater cell death when treated with ivermectin and doxorubicin,¹²Fang T, Xie X et al. Patient-derived organoids on a microarray for drug resistance study in breast cancer. Analytical Chemistry. 2024 Nov 19;96(46):18384-18391. as do paclitaxel-resistant lung cancer cells treated with both ivermectin and paclitaxel,¹³Hayashi A, Kamio K et al. Ivermectin enhances paclitaxel efficacy by overcoming resistance through modulation of ABCB1 in non-small cell lung cancer. Anticancer Research. 2024 Dec;44(12):5271-5282. and flumatinib-resistant myeloid leukemia cells treated with ivermectin and flumatinib.¹⁴Huang J, Xiao J et al. Overcoming flumatinib resistance in chronic myeloid leukaemia: Insights into cellular mechanisms and ivermectin’s therapeutic potential. Journal of Cellular and Molecular Medicine. 2024 Jul;28(14):e18539. Ivermectin in combination with other drugs has also shown positive results on non-drug-resistant cancer cells: for example, multiple myeloma cells exposed to ivermectin and bortezomib showed more cell death than cells treated with bortezomib alone in one experiment;¹⁵Luo H, Feng Y et al. Combinations of ivermectin with proteasome inhibitors induce synergistic lethality in multiple myeloma. Cancer Letters. 2023 Jul 1;565:216218. experiments testing ivermectin plus doxorubicin on osteosarcoma cells and ivermectin plus sorafenib on hepatocellular cancer cells found similar results.¹⁶Hu B, Tan H et al. Repurposing Ivermectin to augment chemotherapy’s efficacy in osteosarcoma. Human & Experimental Toxicology. 2022 Jan-Dec;41:9603271221143693; Lu H, Zhou L et al. Ivermectin synergizes sorafenib in hepatocellular carcinoma via targeting multiple oncogenic pathways. Pharmacology Research & Perspectives. 2022 Jun;10(3):e00954.

Researchers combining ivermectin with immunotherapy (anti-PD1 antibodies) in mice found that the combination was more effective than either drug alone against breast tumors, with evidence that ivermectin helped immune cells to enter the tumors.¹⁷Draganov D, Han Z et al. Ivermectin converts cold tumors hot and synergizes with immune checkpoint blockade for treatment of breast cancer. NPJ Breast Cancer. 2021 Mar 2;7(1):22. Researchers suggest that ivermectin may help make cancer cells more sensitive to treatment by blocking proteins that help cells survive under stress.¹⁸Heiserman JP, Minhas Z et al. Targeting Heat Shock Protein 27 and fatty acid oxidation augments cisplatin treatment in cisplatin-resistant ovarian cancer cell lines. International Journal of Molecular Sciences. 2023 Aug 10;24(16):12638. It also appears to trigger the cells’ natural self-destruction processes in response to DNA and mitochondrial damage.¹⁹Luo H, Feng Y et al. Combinations of ivermectin with proteasome inhibitors induce synergistic lethality in multiple myeloma. Cancer Letters. 2023 Jul 1;565:216218. 

A question of strength

On their own, all these laboratory results sound promising. However, in a 2022 paper, biochemists running a key experiment using increasing amounts of ivermectin for cervical cancer cells reported a startling finding. What was killing the cancer cells in their cultures was not ivermectin itself, but ivermectin precipitate. That is, ivermectin—a hydrophobic molecule that does not dissolve easily in water—had formed tiny particles in the solution, and these particles were killing the cancer cells, apparently by lysing (piercing) and stressing them.²⁰Qabbus MB, Hunt KS et al. Ivermectin-induced cell death of cervical cancer cells in vitro a consequence of precipitate formation in culture media. Toxicology and Applied Pharmacology. 2022 Aug 15;449:116073. The cancer cells began dying at concentrations of 3 µM (micro-molar). However, when the authors filtered particles out of the solution, the cells were unaffected. What is more, the concentration of ivermectin at which the authors began seeing cancer cell death was orders of magnitude greater than the concentration achievable in the human body. At standard doses, the plasma concentration of ivermectin in the human body is about 50 nM (nano-molar)—one hundred times smaller than the 3 µM used in the lab experiments.²¹Schmith VD, Zhou JJ, Lohmer LRL. The approved dose of ivermectin alone is not the ideal dose for the treatment of COVID-19. Clinical Pharmacology and Therapeutics. 2020 Oct;108(4):762-765; Qabbus MB, Hunt KS et al. Ivermectin-induced cell death of cervical cancer cells in vitro a consequence of precipitate formation in culture media. Toxicology and Applied Pharmacology. 2022 Aug 15;449:116073. Even at higher doses, plasma concentrations in the human body peak at 300 nM.²²Guzzo CA, Furtek CI et al. Safety, tolerability, and pharmacokinetics of escalating high doses of ivermectin in healthy adult subjects. Journal of Clinical Pharmacology. 2002 Oct;42(10):1122-33; Qabbus MB, Hunt KS et al. Ivermectin-induced cell death of cervical cancer cells in vitro a consequence of precipitate formation in culture media. Toxicology and Applied Pharmacology. 2022 Aug 15;449:116073. 

While we could not find the exact concentrations used in all of the studies of ivermectin alone on cancer cells, the ones that did report the doses, even those described as clinically relevant, used levels well above this concentration.²³Lombardi Z, Gardini L et al. Importin subunit beta-1 mediates ERK5 nuclear translocation, and its inhibition synergizes with ERK5 kinase inhibitors in reducing cancer cell proliferation. Molecular Oncology. 2025 Jan;19(1):99-113; Hu B, Tan H et al. Repurposing Ivermectin to augment chemotherapy’s efficacy in osteosarcoma. Human & Experimental Toxicology. 2022 Jan-Dec;41:9603271221143693; Lv S, Wu Z et al. Integrated analysis reveals FOXA1 and Ku70/Ku80 as targets of ivermectin in prostate cancer. Cell Death and Disease. 2022 Sep 1;13(9):754; Lu H, Zhou L et al. Ivermectin synergizes sorafenib in hepatocellular carcinoma via targeting multiple oncogenic pathways. Pharmacology Research & Perspectives. 2022 Jun;10(3):e00954; Xu N, Lu M et al. Ivermectin induces apoptosis of esophageal squamous cell carcinoma via mitochondrial pathway. BMC Cancer. 2021 Dec 7;21(1):1307; Juarez M, Schcolnik-Cabrera A et al. Antitumor effects of ivermectin at clinically feasible concentrations support its clinical development as a repositioned cancer drug. Cancer Chemotherapy and Pharmacology. 2020 Jun;85(6):1153-1163. The lowest dose used was 1 µM, which is 33 times the human plasma concentration of 30 nM at a standard dose of ivermectin. Experiments looking at ivermectin’s effect in combination with chemotherapy drugs tended to use the concentration that was 50% effective against the cells they were testing: the lowest concentration used was 1.5 µM,²⁴Heiserman JP, Minhas Z et al. Targeting Heat Shock Protein 27 and fatty acid oxidation augments cisplatin treatment in cisplatin-resistant ovarian cancer cell lines. International Journal of Molecular Sciences. 2023 Aug 10;24(16):12638. and most were in the range of 3-5 µM.²⁵Morinaga S, Han Q et al. Recombinant methioninase (rMETase) synergistically sensitizes ivermectin-resistant MCF-7 breast cancer cells 9.9 fold to low-dose ivermectin. Anticancer Research. 2025 Feb;45(2):451-455; Hayashi A, Kamio K et al. Ivermectin enhances paclitaxel efficacy by overcoming resistance through modulation of ABCB1 in non-small cell lung cancer. Anticancer Research. 2024 Dec;44(12):5271-5282; Luo H, Feng Y et al. Combinations of ivermectin with proteasome inhibitors induce synergistic lethality in multiple myeloma. Cancer Letters. 2023 Jul 1;565:216218; Nunes M, Duarte D et al. The antineoplastic effect of carboplatin is potentiated by combination with pitavastatin or metformin in a chemoresistant high-grade serous carcinoma cell line. International Journal of Molecular Sciences. 2022 Dec 21;24(1):97; Lu H, Zhou L et al. Ivermectin synergizes sorafenib in hepatocellular carcinoma via targeting multiple oncogenic pathways. Pharmacology Research & Perspectives. 2022 Jun;10(3):e00954. 

Commentary by CancerChoices Advisor, Walter Tsang MD: “Additionally, even if the concentration of the drug was high enough in the blood, the blood flow has to actually reach the sites of cancer cells and tumor for the drugs to be effective. We know that cancer cells thrive in a hypoxic (low oxygen), acidic, and ischemic micro-environment, and when a tumor is too big, there is inadequate blood flow to even get to the cancer.”

This mismatch in concentration does not mean that all the existing laboratory studies on ivermectin are baseless; rather, it reflects the danger in extrapolating from in vitro experiments to human medicine without intermediary experiments. A limited number of the studies we reviewed also tested ivermectin as a cancer therapy in mice, with some success: mice treated with ivermectin showed more shrinkage in bladder cancer tumors in one experiment²⁶Fan N, Zhang  et al. Ivermectin inhibits bladder cancer cell growth and induces oxidative stress and DNA damage. Anticancer Agents in Medicinal Chemistry. 2024;24(5):348-357. and smaller ovarian, breast, and prostate tumors in another,²⁷Juarez M, Schcolnik-Cabrera A et al. Antitumor effects of ivermectin at clinically feasible concentrations support its clinical development as a repositioned cancer drug. Cancer Chemotherapy and Pharmacology. 2020 Jun;85(6):1153-1163. as well as esophageal cancer tumor shrinkage and less metastasis in a third,²⁸Chen L, Bi S et al. Ivermectin suppresses tumour growth and metastasis through degradation of PAK1 in oesophageal squamous cell carcinoma. Journal of Cell and Molecular Medicine. 2020 May;24(9):5387-5401. suggesting that even at lower concentrations, ivermectin could have an effect. The fact that laboratory experiments have used unrealistically high concentrations of ivermectin on cancer cells also does not mean that it would have no effect in combination with chemotherapy drugs,²⁹Qabbus MB, Hunt KS et al. Ivermectin-induced cell death of cervical cancer cells in vitro a consequence of precipitate formation in culture media. Toxicology and Applied Pharmacology. 2022 Aug 15;449:116073. nor does it invalidate the data from protein assays and computer modeling suggesting that ivermectin may inhibit cancer-promoting genes.³⁰Lv S, Wu Z et al. Integrated analysis reveals FOXA1 and Ku70/Ku80 as targets of ivermectin in prostate cancer. Cell Death and Disease. 2022 Sep 1;13(9):754; Lu H, Zhou L et al. Ivermectin synergizes sorafenib in hepatocellular carcinoma via targeting multiple oncogenic pathways. Pharmacology Research & Perspectives. 2022 Jun;10(3):e00954; Zhang X, Qin T et al. Ivermectin augments the in vitro and in vivo efficacy of cisplatin in epithelial ovarian cancer by suppressing Akt/mTOR signaling. American Journal of Medical Sciences. 2020 Feb;359(2):123-129; Feng Y, Wang J et al. Ivermectin accelerates autophagic death of glioma cells by inhibiting glycolysis through blocking GLUT4 mediated JAK/STAT signaling pathway activation. Environmental Toxicology. 2022 Apr;37(4):754-764; Bhadra S, Xu YJ. TTT (Tel2-Tti1-Tti2) Complex, the Co-Chaperone of PIKKs and a Potential Target for Cancer Chemotherapy. International Journal of Molecular Sciences. 2023 May 5;24(9):8268; Siddiqui AJ, Khan MF et al. Molecular docking and dynamics simulation revealed ivermectin as potential drug against schistosoma-associated bladder cancer targeting protein signaling: computational drug repositioning approach. Medicina (Kaunas). 2021 Oct 3;57(10):1058.

Conclusion

There is good reason to study ivermectin further: it is widely available, inexpensive, and relatively safe at normal doses. What is more, the current evidence suggests it might have potential as an adjunct to standard cancer treatment, especially in cases where the cancer has become resistant to standard chemotherapy. In one series of three case studiesa descriptive and exploratory analysis of a person, group, or event regarding changes observed over time; because changes due to treatment are not compared to similar changes over time without treatment, a case study is considered a weak study design, people with cancer taking ivermectin as part of a multi-drug regimen may have shown improvement, though because they were taking ivermectin alongside several other anticancer drugs, it is not possible to know whether the ivermectin helped.³¹Ishiguro T, Ishiguro RH et al. Synergistic anti-tumor effect of dichloroacetate and ivermectin. Cureus. 2022 Feb 3;14(2):e21884.

However, there is also good reason for caution. Ivermectin has not yet been systematically tested as a cancer treatment in humans. To mimic any of the conditions that produced these laboratory results, ivermectin would have to be given at extremely high doses. Additionally, under some conditions, ivermectin might actually promote cancer: Onchocerca volvulus worms (the parasitic worm that causes river blindness) treated with ivermectin show more abnormal cell growth than worms treated with other antiparasitic medications,³²Duke BO, Marty AM et al. Neoplastic change in Onchocerca volvulus and its relation to ivermectin treatment. Parasitology. 2002 Nov;125(Pt 5):431-44. while Xenopus (frog) embryos treated with ivermectin show melanoma-like cell changes.³³Hutchison A, Sibanda C et al. Re-examining the evidence that ivermectin induces a melanoma-like state in Xenopus embryos. Bioessays. 2024 Jan;46(1):e2300143. Taking too high a dose of ivermectin—for example, when humans take ivermectin pills intended for animals—can cause neurological effects like delirium and even coma, as well as gastrointestinal problems.³⁴Hoang R, Temple C, Correia MS, Clemons J, Hendrickson RG. Characteristics of ivermectin toxicity in patients taking veterinary and human formulations for the prevention and treatment of COVID-19. Clinical Toxicology(Phila). 2022 Dec;60(12):1350-1355; Chandler RE. Serious neurological adverse events after ivermectin-do they occur beyond the indication of onchocerciasis? American Journal of Tropical Medicine and Hygiene. 2018 Feb;98(2):382-388. Finally, some of ivermectin’s apparent success in laboratory tests may be simply because it is receiving more attention than other widely available medications: one experiment found that carboplatin combined with ivermectin did not kill as many carboplatin-resistant ovarian cancer cells as carboplatin combined with other repurposed drugs, including pitavastatin and metformin.³⁵Nunes M, Duarte D et al. The antineoplastic effect of carboplatin is potentiated by combination with pitavastatin or metformin in a chemoresistant high-grade serous carcinoma cell line. International Journal of Molecular Sciences. 2022 Dec 21;24(1):97 The majority of new drugs that appear promising in the lab turn out not to be effective once they reach human trials.³⁶Kimmelman J, Federico C. Consider drug efficacy before first-in-human trials. Nature. 2017 Jan 30;542(7639):25-27. Much more research is needed before we know whether ivermectin is safe or effective as a cancer treatment in humans.

The numbers matter: understanding drug concentrations

When reading about experiments using ivermectin on cancer cells, check the concentration the researchers used. Concentrations will often be reported in M (Molar) format which measures how much of a substance is in a liter of solution. A micromole (µM) means one millionth, or 1×10^-6 of a mole; a nanomole (nM) is one billionth, or 1×10^-9 of a mole. For context, the highest concentration of ivermectin typically found in the human bloodstream is about 50 nM (50 x 10^-9 moles). So you can compare that to what was in the lab to see how realistic the dose is.

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