Researchers at Washington State University have engineered a targeted nanotherapy using a repurposed anti-parasitic drug to shrink endometriosis lesions and reduce pain sensitivity in mice.
For patients like Kristina Medvedev—who endured 14 years of severe pain before undergoing surgery in March 2024—the search for effective care has long been fraught with frustration as symptoms are frequently normalized by medical providers. Around 190 million people live with the debilitating condition globally.
Endometriosis is characterized by the growth of tissue similar to the inner lining of the uterus outside the uterine cavity, leading to severe chronic pelvic pain, painful menstrual periods, and fertility struggles.
Washington State University Repurposes Niclosamide
Nearly half of patients who undergo the gold-standard surgery experience lesion recurrence within five years. To bypass these limitations, a research team led by reproductive biologist Kanako Hayashi at Washington State University turned to niclosamide, an FDA-approved drug historically used to treat intestinal tapeworms. Endometriosis is a chronic disease,
Kanako Hayashi, a professor studying reproductive biology at Washington State University in the US, told ScienceAlert.
Current medical management relies heavily on surgical removal of lesions or hormone suppression therapies that induce side effects, including osteoporosis, depression, and infertility. Because the disease is not life-threatening, regulators like the US Food and Drug Administration only approve treatments with minimal side effects, as Hayashi explained.
To solve this delivery barrier, scientists engineered a branching molecular structure known as a dendrimer measuring less than eight nanometres long to carry the medication directly to disease-implicated cells. According to the faculty member at the Washington State University School of Molecular Biosciences, their approach focuses on utilizing a widely accessible medicine to home in on an endometriosis-related cell, subsequently transporting that therapeutic agent via a nanoparticle. Although earlier studies showed niclosamide could attenuate endometrial tissue growth, the raw compound dissolves poorly in water and is poorly absorbed by the human body.
Taking unadjusted oral doses requires high amounts that cause severe nausea, appetite loss, and stomach cramps, restricting safe use to just seven days at a time.
Targeted Delivery Yields Results in Mice
By grafting folic acid and niclosamide onto the water-soluble dendrimer carrier, researchers ensured the therapeutic payload accumulated specifically within lesions with minimal off-target toxicity. The experimental nanotherapy utilizes folic acid as a ligand to target specific immune cells called macrophages that express folate receptor beta, or FRβ.
These immune cells cluster around endometrial lesions, releasing inflammatory signals and growth factors that sustain abnormal tissue growth.
Two weeks post-treatment, analyses revealed that mice receiving the targeted drug exhibited fewer and smaller lesions compared to control groups. In animal testing, researchers induced endometriosis-like lesions by injecting donor uterine lining tissue into the abdominal cavities of mice.
Seven days later, the animals received a single treatment injection. Furthermore, behavioral assessments measuring responses to pressure applied to the abdomen and hind paws demonstrated that both tested doses eased heightened pain-related sensitivity. The experimental treatment itself was tested in mice, and the study was published in Advanced Healthcare Materials (Hayashi, Sharma et al., Advanced Healthcare Materials, 2026).
Path Forward Toward Human Clinical Trials
Regulatory bodies such as the US Food and Drug Administration require rigorous safety profiles for chronic conditions because endometriosis is not life-threatening. The study assessed small groups of mice over a brief two-week window, leaving long-term safety, repeated dosing efficacy, and human response unverified.
While the preclinical results mark a promising step toward non-surgical and non-hormonal care, experts caution that human translation remains distant.
Dr Hayashi shared that she has already been swamped with outreach from individuals suffering from the illness who are keen to participate in upcoming clinical trials, noting that they are truly prepared to do whatever it takes to better their condition. If human trials prove successful, the treatment could eventually take the form of a monthly injection administered at a clinic rather than daily oral medications. The treatment is at least five years away from public availability.
“Patients suffer from the symptoms (such as chronic pelvic pain) for multiple decades.”
Kanako Hayashi, professor studying reproductive biology at Washington State University
