Question explored with the scientific record
benefits of Ivermectin and Fenbendazole in treating certain types of cancer
The evidence for ivermectin and fenbendazole as cancer treatments is limited to lab studies and animal models, with no human trials proving they shrink tumors or extend life.
The evidence for ivermectin comes from four lab and animal studies. One 2019 study in mice with canine mammary tumors found ivermectin slowed tumor growth by blocking WNT signaling and arresting the cell cycle, with no toxicity at the dose used [1]. A 2025 rat study showed that a special nose-to-brain ivermectin nanoparticle reduced glioma tumor size by 70% compared to controls, but free ivermectin alone did not shrink tumors at all [2]. A 2026 study on triple-negative breast cancer in mice used ivermectin nanocrystals wrapped in platelet membranes to improve delivery, and saw tumors grow 1.8 times slower than with uncoated ivermectin [4]. A 2025 paper tested ivermectin combined with artesunate against cancer cells in a dish and found it killed them at certain concentrations, but this was not tested in a living animal [3].
For fenbendazole, the evidence is even thinner. The only human data is a 2021 case report of an 80-year-old woman with advanced lung cancer who took 1 gram of fenbendazole daily for 30 days. She developed severe liver injury, her tumor did not shrink, and her cancer progressed [5]. That is the sum of the human evidence. The other fenbendazole studies in the retrieval are about drug detection in milk [10], suspension stability [11], and absorption in sheep [9] — none test cancer outcomes.
The mechanism proposed for both drugs is that they interfere with microtubules and cell division, similar to some chemotherapy drugs. Ivermectin also blocks WNT signaling and P-glycoprotein, a pump that cancer cells use to expel chemotherapy [1, 6, 7, 8]. But a plausible mechanism is not proof of benefit in humans.
| Drug | Best evidence | What it showed |
|---|---|---|
| Ivermectin | 2025 rat glioma study [2] | 70% tumor reduction with nanoparticle delivery; free drug did nothing |
| Ivermectin | 2026 mouse breast cancer study [4] | 1.8x slower tumor growth with platelet-coated nanocrystals |
| Fenbendazole | 2021 human case report [5] | Severe liver injury, no tumor response, cancer progressed |
My call: neither drug has human evidence of anticancer benefit. Ivermectin shows promise in animal models but only with advanced delivery systems, not the oral pill you buy at the pharmacy. Fenbendazole has a documented case of harm and zero evidence of benefit in humans. Confidence: high that human evidence is absent; low that either drug works in people, because the animal data is early and the delivery methods tested are not what patients use.
Sources used 11
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Ivermectin inhibits canine mammary tumor growth by regulating cell cycle progression and WNT signaling
The study shows that repurposed anthelmintic ivermectin inhibits canine mammary tumor growth by causing G1 cell cycle arrest via downregulation of cyclin D1 and CDK4 and by suppressing WNT/β-catenin signaling, with efficacy observed in vitro in canine mammary tumor cell lines an…
DOI: 10.1186/s12917-019-2026-2 -
Intranasal Delivery of Ivermectin Nanosystems as an Antitumor Agent: Focusing on Glioma Suppression
This study demonstrates nose-to-brain delivery of ivermectin nanocarriers (polymeric nanocapsules and mesoporous silica particles) to suppress glioma growth in a rat model, with intranasal polymeric nanocapsules significantly reducing tumor size and improving histology at a clin…
DOI: 10.1021/acsbiomaterials.5c00642 -
Antiproliferative and Trypanocidal Activity of Ivermectin Bioconjugates
This study synthesizes ten ivermectin bioconjugates with diverse bioactive partners (cinchona alkaloids, nucleosides, metronidazole, betulinic acid, artesunate) using carbonate, urethane, or click-type linkers, and evaluates their antiproliferative activity against four human ca…
DOI: 10.1021/acsomega.5c02998 -
Biomimetic platelet-membrane camouflaged ivermectin nanocrystals for tumor homing and breast cancer management
The study develops biomimetic platelet-membrane camouflaged ivermectin nanocrystals (PMV/Ivm-NC) using a sonoprecipitation method and platelet membrane coating to achieve targeted tumor homing, immunogenic cancer cell death, and enhanced antitumor/antimetastatic effects against …
DOI: 10.1007/s13346-025-02032-2 -
Drug-Induced Liver Injury in a Patient with Nonsmall Cell Lung Cancer after the Self-Administration of Fenbendazole Based on Social Media Information
This case report describes an 80-year-old woman with advanced nonsmall cell lung cancer who developed severe drug-induced liver injury after self-administering fenbendazole based on social media information, with liver enzymes normalizing after cessation and no observed antitumo…
DOI: 10.1159/000516276 -
Critical Role of P-Glycoprotein-9 in Ivermectin Tolerance in Nematodes
This study investigates the critical role of P-Glycoprotein-9 in mediating ivermectin tolerance in nematodes, particularly using the Caenorhabditis elegans IVR10 strain, revealing that deletion of pgp-9 significantly increases ivermectin sensitivity.
DOI: 10.1101/2025.07.10.664073 -
Potential metabolic resistance mechanisms to ivermectin in Anopheles gambiae: a synergist bioassay study
This study investigates whether detoxification by cytochrome P450 enzymes (CYPs) and P-glycoprotein (P-gp) transporters mediates ivermectin resistance in Anopheles gambiae by testing ivermectin with CYP/P-gp inhibitors and inducers, finding that simultaneous CYP and P-gp inhibit…
DOI: 10.1186/s13071-021-04675-9 -
Haemonchus contortus P-glycoprotein-2: in situ localisation and characterisation of macrocyclic lactone transport
This study heterologously characterizes Haemonchus contortus P-glycoprotein-2 (Hco-PGP-2) by expressing it in LLC-PK1 cells, showing ATP-dependent efflux of fluorophores (Rhodamine 123 and Calcein-AM), differential inhibition by macrocyclic lactones (ivermectin, abamectin, and m…
DOI: 10.1016/j.ijpara.2014.09.008 -
Biotransformation of fenbendazole in sheep after administration of fenbendazole solid dispersion prepared by mechanochemical technique with arabinogalactane
Mechanochemical fenbendazole solid dispersion with arabinogalactan increases fenbendazole dissolution and absorption in sheep, substantially altering pharmacokinetics and biotransformation and boosting antihelminthic activity against gastrointestinal nematodes.
DOI: 10.31016/1998-8435-2023-17-3-386-399 -
Preparation of Milk Samples for Immunoassay and Liquid Chromatographic Screening Using Matrix Solid-Phase Dispersion
The paper describes matrix solid-phase dispersion (MSPD) methods for extracting and fractionating multiple drug classes (benzimidazoles, chloramphenicol, sulfonamides, tetracyclines, chlorsulon, chlorsulfuron, furazolidone) from milk for immunoassay and liquid chromatographic sc…
DOI: 10.1093/jaoac/77.4.848 -
Stability of fenbendazole suspensions for veterinary use
An in-depth physical-chemistry study characterizes fenbendazole suspensions for veterinary use by linking zeta potential, surface energy, and electrophoretic mobility to sedimentation behavior across pH and electrolyte conditions, showing hydrophobic interactions dominate stabil…
DOI: 10.1016/j.ejps.2008.04.008