Preclinical Research · 2026
Tapeworm Drug Shows Promise for Endometriosis Pain Relief in Breakthrough Mouse Study
Scientists have engineered a molecular carrier to deliver niclosamide — an antiparasitic medication — directly to disease-specific immune cells, reducing lesions and pain sensitivity in a mouse model of endometriosis.
Every month, the pain reasserts itself. For millions of women living with endometriosis, that cyclical ordeal can persist for decades, often with little relief from existing therapies. Now, researchers studying this chronic and currently incurable condition have identified an unlikely candidate in the fight against it: niclosamide, a long-approved medication primarily used to rid the body of intestinal tapeworms. A new study published in Advanced Healthcare Materials reports that a specially engineered version of the drug — one designed to navigate directly to specific immune cells implicated in the disease — measurably reduced both the number of endometriosis-related lesions and pain-related sensitivity in a mouse model. While the findings represent an early, preclinical step, they have already generated significant interest among patients and scientists alike who are searching urgently for alternatives to hormonal therapies and surgery.
Understanding the Chronic Disease Burden of Endometriosis
Endometriosis develops when tissue resembling the uterine lining takes root and grows in locations outside the uterus. Those misplaced growths — referred to as lesions — respond to hormonal fluctuations much as the uterine lining does, resulting in inflammation, scarring, and persistent pain. The condition is estimated to affect roughly one in ten women of reproductive age worldwide, translating to approximately 190 million individuals globally. Symptoms range from severe pelvic pain and debilitating menstrual cramping to fertility complications that can profoundly alter a patient’s life course.
Current medical options are narrow in scope. Hormonal therapies can suppress symptoms by regulating the menstrual cycle, and surgery can physically remove lesions — but neither approach constitutes a cure. Both carry the risk of symptom recurrence, and long-term hormonal treatment raises its own set of tolerability concerns. It is within this gap in the treatment landscape that researchers at Washington State University, collaborating with teams from the University of Michigan and the University of Florida, have been working to develop something new.
Sources: WHO; ACOG, 2026; Advanced Healthcare Materials, 2026
“Endometriosis is a chronic disease. Patients suffer from the symptoms (such as chronic pelvic pain) for multiple decades.”— Kanako Hayashi, Professor of Reproductive Biology, Washington State University
How Immune Cell Targeting Drives the New Therapeutic Approach
The research team’s strategy centers on a type of immune cell known as a macrophage. These cells play a complex role throughout the body, including in the inflammatory environment that sustains endometriosis. Prior research, including work published in Communications Biology, has indicated that macrophages in the peritoneal cavity of women with endometriosis can behave abnormally — secreting inflammatory molecules and growth factors that enable lesions to expand and persist. Exactly whether this immune dysfunction is a driver of the disease or a consequence of it remains an open question in the field, but the connection has provided a compelling target for intervention.
What distinguished this team’s approach was identifying a specific subset of macrophages that appear in elevated numbers within endometriosis lesions in both humans and mice. These particular cells bear a surface protein known as folate receptor beta, abbreviated as FRβ. Because folic acid binds naturally to this receptor, the research team recognized that a drug carrier decorated with folic acid could potentially act as a molecular key — unlocking entry into precisely these disease-associated macrophages while bypassing other cell populations.
To investigate the FRβ-bearing macrophages as a valid target, the researchers examined data from ten previously published human cell datasets, supplementing that analysis with freshly collected samples drawn from the abdominal cavities of four patients. This combination of retrospective and prospective human data helped establish the scientific rationale before the team moved to animal testing.
Key Scientific Concepts
Macrophages: Immune cells found in elevated and dysregulated numbers within endometriosis lesions, capable of releasing inflammatory signals and growth factors that sustain abnormal tissue growths.
Folate Receptor Beta (FRβ): A surface protein found on disease-associated macrophages in endometriosis lesions, used in this study as a precise molecular delivery address for the drug carrier.
Dendrimer: A small, highly branched synthetic molecule engineered by the research team to carry niclosamide and folic acid, designed to release its drug payload once inside the targeted cells.
Why Niclosamide — and What Made It Difficult to Use Before
Niclosamide is not a new compound. It has been approved and in clinical use for decades as an anthelmintic — a drug that kills parasitic worms, including intestinal tapeworms. More recently, it has attracted scientific attention as a candidate for repurposing across a range of other diseases, including certain cancers. Earlier mouse research conducted by Hayashi’s group, published in Communications Biology, had already demonstrated that niclosamide could reduce lesion growth and suppress aberrant inflammation in peritoneal fluids in endometriosis mouse models. Those results were encouraging, but converting them into a viable human therapy posed a significant practical obstacle.
Niclosamide has notably poor water solubility. When taken orally, relatively little of the drug successfully enters the bloodstream, meaning that effective doses must be large — a factor that complicates safety and tolerability over long-term use. For a chronic condition like endometriosis, where treatment may be required over decades, daily oral administration of a poorly soluble compound presents genuine challenges for patients and clinicians alike. Hayashi has emphasized that sustaining any daily regimen long-term is inherently difficult, and the side-effect profile associated with high doses adds further concern.
The dendrimer carrier developed by the collaborative team was designed to address both of these shortcomings simultaneously. By bonding niclosamide chemically to the carrier — using a linkage engineered to dissolve and release the drug once inside the target cells — the researchers aimed to improve solubility, focus delivery on diseased tissue, and minimize the drug’s exposure to unaffected areas of the body. The vision articulated by the team is that such a system could potentially allow for infrequent injection rather than daily oral dosing.
“We found the disease-specific immune cell, and then we had a drug, but we couldn’t target the cell with the drug alone. So we used this nanocarrier that delivers the drug specifically to the disease site.”— Kanako Hayashi, Washington State University
The Scientific Timeline Behind This Preclinical Endometriosis Discovery
The 2026 study did not emerge in isolation. It is the product of a sustained research effort at Washington State University, building incrementally on prior work to reach this point of targeted drug delivery.
Mouse Study Results: Fewer Lesions and Reduced Pain Sensitivity
To test the nanotherapy in a controlled setting, the research team induced endometriosis-like conditions in mice by transferring uterine lining tissue from donor animals into the abdominal cavities of the test subjects — a standard preclinical model for the disease. One week after induction, the animals received a single injection. One group of mice received the carrier structure alone, without niclosamide attached, serving as a control. The remaining animals were divided into two treatment groups, each receiving the niclosamide-loaded carrier at different dose levels.
Two weeks after the injection was administered, the researchers evaluated outcomes. Mice that had received the drug-loaded carrier showed fewer lesions overall, and the growths that remained were smaller compared to controls. Among the lower-dose group — comprising eight mice — four animals showed no detectable lesions at the evaluation point. In the higher-dose group, also of eight animals, five had no measurable lesions. The team assessed pain-related sensitivity using calibrated filaments applied to both the abdomen and hind paws, measuring how forcefully the mice responded to pressure. Across both dose levels, treated animals displayed a reduction in heightened sensitivity compared to the control group.
Source: Hayashi, Sharma et al., Advanced Healthcare Materials, 2026. Assessed two weeks post single injection.
It is important to note the significant boundaries of these findings. The withdrawal responses measured in the animals indicate a biological change in pain-related sensitivity — they do not and cannot confirm what level of subjective pain relief a human patient with endometriosis would actually experience. Each treatment group comprised only eight mice, and follow-up extended only two weeks beyond the single injection. The study did not assess repeated dosing, long-term safety, or whether the benefits would persist further over time.
The Road to Human Clinical Trials Remains Long for This Research
Hayashi has been candid about where this work stands in the broader arc of drug development. The study is squarely in preclinical territory, and multiple regulatory and scientific milestones must be reached before any human testing can begin. Demonstrating safety and efficacy in animal models at greater scale, establishing long-term tolerability with repeated doses, and navigating formal approval processes for clinical trials are all steps that lie ahead. As Hayashi has put it, the therapy “is still a long way from being commercialized.”
Yet interest from the patient community has already materialized. Since the paper’s publication, individuals living with endometriosis have reached out to the research team directly, inquiring about involvement in future trials or asking to be notified when such trials open. That response reflects the broader reality that the current treatment landscape leaves a substantial portion of patients unsatisfied, and the appetite for genuinely new, non-hormonal options is considerable. Several members of the research team, including Hayashi and co-author Anjali Sharma, have disclosed pending patents and invention disclosures tied to the dendrimer technology at the center of this work.
External scientists have offered cautious but meaningful endorsement of the approach’s direction. The study has been characterized as a “beautiful first step” toward non-surgical, non-hormone-based endometriosis therapies — a category of treatment that remains largely underdeveloped despite the scale of the condition’s global burden.
A First Step Toward Lasting Relief for Endometriosis Patients
The niclosamide dendrimer study does not promise a cure, and its authors have been deliberate in setting realistic expectations — but it does represent something that has been scarce in endometriosis research for decades: a mechanistically specific, non-hormonal approach that has produced measurable results in a controlled preclinical setting. For a disease that strips quality of life from tens of millions of women across multiple decades, and for which existing options continue to fall short, even an early-stage preclinical signal of this kind carries genuine weight. The path from mouse model to medicine is long and uncertain, and the regulatory and scientific work ahead is substantial — but the direction of travel, toward targeted immune cell intervention using an existing approved compound, offers a genuinely novel framework that the field has not previously been able to fully explore, and one that patients are already watching with close attention.
