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Niclosamide, an FDA-approved drug for tapeworm and other intestinal helminth infections, reduced endometriosis-like lesions and inflammatory activity in mice. A 2026 experiment improved the approach by packaging niclosamide for delivery to a specific macrophage population, reducing lesions and pain behavior in mice after one dose. No cited study has shown that niclosamide treats endometriosis in people, established a human dose, or proved its safety for this use.
Endometriosis affects an estimated 190 million people worldwide, according to the World Health Organization as reported in the 2026 Nature coverage. The 2017 primary paper cited an estimate of 6%–10% of women of reproductive age and noted a conservative recurrence estimate of 50% within five years after laparoscopic surgery. Those limits help explain interest in non-surgical, non-hormonal approaches—but the niclosamide evidence remains preclinical.
What the studies found
2017: oral niclosamide reduced mouse lesions
In the 2017 mouse model, animals received niclosamide orally for three weeks at 100 or 200 mg/kg/day. Treated mice had lower implant weight and slower lesion growth, along with reduced epithelial-cell proliferation. Molecular analyses showed less activity in inflammatory NF-κB and STAT3-related signaling pathways.
A separate reproductive experiment found that treated mice became pregnant and produced normal-sized litters under the conditions tested. That result is a limited animal finding, not evidence that niclosamide is safe for pregnancy or fertility in humans. The paper specifically said that complete toxicology work would be needed before clinical trials. The mouse doses must not be converted into a self-directed human dose.
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2020: evidence for an inflammatory, macrophage-related mechanism
Follow-up work examined niclosamide against macrophage-associated inflammatory signaling in endometriosis models and in primary human endometriotic stromal cells. The human-cell experiments support biological plausibility: they show that cells taken from patients can respond to the drug in a laboratory setting. They do not show symptom relief, lesion reduction, or acceptable safety in patients.
2022: single-cell analysis identified changes in macrophage populations
A 2022 single-cell transcriptomics study reported that niclosamide changed the progression and composition of peritoneal macrophage populations in mouse endometriosis-like lesions. It also restored some communication between macrophages and B cells. These findings refine the proposed mechanism, but the authors said comparable macrophage functions still need validation in human patients.
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2026: targeted delivery produced lesion and pain improvements in mice
The newest study engineered FA-2DG-D-Niclo, a dendrimer carrying niclosamide and modified with folic acid and 2-deoxyglucose. The design aimed to concentrate the drug in FRβ-positive macrophages—an inflammatory macrophage population identified by the folate-receptor-beta marker—rather than exposing every tissue to the same formulation.
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Clear out junk files and repair common Windows errorsFree Scan →Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →Repair Windows errors before they cause bigger problemsFix Now →In mice, one intraperitoneal dose containing either 25 or 50 mg/kg of niclosamide reduced the burden of FRβ-positive macrophages, lesion number, and lesion volume. Two weeks after dosing, the animals also showed less endometriosis-associated hyperalgesia, a laboratory measure of pain sensitivity. The formulation accumulated in lesions and peritoneal cells while showing limited retention in off-target organs in that experiment. These are mouse pharmacology and safety observations, not evidence of a usable human treatment.
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How the proposed biology differs from hormonal treatment
Niclosamide is being studied here for effects on inflammatory signaling and immune-cell behavior, not for ovarian hormone suppression. The studies point to several connected processes: reduced NF-κB/STAT3-related signaling, altered macrophage populations in the peritoneal environment, and changes in macrophage–B-cell communication. The 2026 formulation adds a targeting strategy intended to reach FRβ-positive macrophages more selectively.
That distinction makes the work potentially relevant to people who cannot use, do not tolerate, or do not want hormone-based treatment. It does not establish that niclosamide will work independently of hormonal pathways in human disease, nor that targeting the same cells will produce the same results in patients.
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- HOW TO USE - Adults take one tablet daily, or as directed by a physician. This daily supplement is free of starch, sodium, soy, gluten, corn, yeast, preservatives, artificial colors or flavors.
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Systemic niclosamide versus the 2026 targeted formulation
| Feature | Systemic niclosamide studies | FA-2DG-D-Niclo study |
|---|---|---|
| Evidence stage | Mouse experiments, plus laboratory work in primary human endometriotic stromal cells | Mouse experiment reported in 2026 |
| Delivery | Oral dosing in the 2017 mouse study | Single intraperitoneal dose |
| Animal dose | 100 or 200 mg/kg/day for three weeks in mice | 25 or 50 mg/kg once in mice |
| Cellular focus | Inflammatory signaling and macrophage-associated mechanisms | FRβ-positive macrophages, using a folic-acid/2-deoxyglucose dendrimer carrier |
| Lesion result | Lower implant weight and growth in the 2017 mouse model | Fewer and smaller lesions in mice at two weeks |
| Pain result | Not stated for the 2017 study | Reduced hyperalgesia in mice at two weeks |
| Reproductive result | Pregnancy and normal-sized litters in a separate treated-mouse experiment | Not stated |
| Human evidence | No clinical efficacy or dosing evidence | No human efficacy, dosing, or safety evidence |
What is still unknown before a patient could consider it
- Whether niclosamide reduces endometriosis lesions or pain in humans.
- Which formulation, route, dose, and treatment duration would be appropriate for people.
- Whether the drug or the dendrimer carrier causes short- or long-term toxicity with repeated use.
- How the treatment affects fertility, pregnancy, menstruation, liver function, and other organs in patients.
- Whether human endometriosis contains macrophage populations that respond like those in the mouse models.
- Whether targeted delivery is practical, manufacturable, and sufficiently selective for clinical use.
Is niclosamide safe to try for endometriosis?
There is no evidence in these studies that taking commercially available niclosamide tablets treats endometriosis. The 2017 reproductive finding applies only to the tested mice, and the 2026 formulation is an experimental laboratory nanomedicine—not a marketed endometriosis therapy. Animal doses, including 100–200 mg/kg/day orally and 25–50 mg/kg intraperitoneally, must not be used to calculate a human dose.
Self-medication could expose someone to drug effects without a proven benefit and could delay evaluation of pain, heavy bleeding, infertility, or another condition. Anyone with suspected or diagnosed endometriosis should discuss established diagnostic and treatment options with a qualified clinician rather than using niclosamide outside a properly reviewed clinical study.
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Why researchers describe the result as promising but preliminary
Kanako Hayashi, a reproductive biologist and study co-author, said that replication in people could make the findings a “breakthrough” in endometriosis treatment. Elise Courtois, a molecular biologist at the Jackson Laboratory, called the work a “beautiful first step” toward non-surgical, non-hormone-based therapies. Both comments describe future potential, not a current medical indication.
The practical conclusion is therefore narrow: niclosamide has a plausible anti-inflammatory rationale and has produced lesion and pain-related benefits in mouse models, with a 2026 targeting strategy that may improve where the drug goes. Human trials must still establish whether those effects translate, what risks accompany them, and whether the approach is better than existing care.
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