Tens of millions of individuals in Africa are afflicted by parasitic worms that induce lymphatic filariasis (also known as elephantiasis), a condition that results in significant swelling and deformities of the limbs and genital region. Despite extensive treatment initiatives that have effectively mitigated the risk of contracting lymphatic filariasis, hundreds of millions of individuals still remain susceptible to the infection.
A modest clinical trial in Cote d’Ivoire, spearheaded by scientists at Washington University School of Medicine in St. Louis, indicates that the anti-parasitic medication moxidectin — presently approved for treating river blindness, another tropical ailment caused by parasitic worms — is also more efficacious for lymphatic filariasis than the established standard treatment, ivermectin. Furthermore, since moxidectin has a lasting impact in the majority of treated patients, it may require fewer treatment cycles, in contrast to the annual treatment for at least five years needed for ivermectin, suggesting a potential to hasten the eradication of the infection across Africa.
This research was published on May 6 in The Lancet Infectious Diseases.
“Moxidectin proves to be significantly more effective than the treatments we currently utilize against lymphatic filariasis,” stated Philip Budge, MD, PhD, an associate professor of medicine in the Division of Infectious Diseases at WashU Medicine and the principal author of the research. “The reality is, in many parts of Africa, lymphatic filariasis and onchocerciasis, or river blindness, co-exist, and a robust treatment is essential for both.”
The trial was conducted in partnership with the Centre Suisse de Recherches Scientifique in Côte d’Ivoire. Lymphatic filariasis is prevalent in numerous African nations, with over 26 million individuals estimated to be at risk for infection in Cote d’Ivoire alone. The parasite responsible for the disease, Wuchereria bancrofti, is transmitted by mosquitoes.
River blindness, which leads to itching, rashes, skin nodules, and vision impairment (which, if untreated, can result in irreversible blindness), is endemic in many of the same regions as lymphatic filariasis. Both ailments have been prioritized for elimination by global initiatives established by the World Health Organization (WHO). For lymphatic filariasis, the distribution of anti-parasitic medications to nearly 1 billion individuals thus far represents the largest mass drug administration endeavor for any infectious illness. In addition to limb swelling, lymphatic filariasis could elevate the risks of patients contracting other diseases like malaria, tuberculosis, and HIV/AIDS.
Participants in the trial — all adults aged between 18 to 70 — had high blood levels of microfilaria, the larvae of adult worms. Those with elevated levels are considered infectious, facilitating the ongoing transmission of this disease.
The study comprised four treatment groups, each receiving a mixture of either moxidectin or ivermectin alongside one or two other medications commonly used for parasitic worm infections.
After a year, 18 out of 19 participants in the moxidectin plus another drug (albendazole) group had cleared their infections compared to 8 out of 25 in the ivermectin combined with albendazole group. At the 24-month mark, 14 out of 16 participants in the moxidectin group remained microfilaria-free.
Among participants who received either ivermectin or moxidectin along with two additional drugs, 21 out of 23 individuals in the moxidectin group were parasite-free after 24 months while 20 out of 22 participants in the ivermectin group cleared their infections during the same timeframe. This outcome suggests that one dose of moxidectin with another drug is as effective as either moxidectin or ivermectin combined with two other medications.
“When treated with moxidectin, individuals are more likely to remain free of parasites for a longer duration,” remarked Budge. “With ivermectin, patients must undergo multiple treatments. Thus, perhaps the ideal application for moxidectin in global elimination initiatives is for populations that are challenging to reach repeatedly.”
Budge clarified that many individuals overlooked by mass drug administration initiatives are hard to re-treat because they reside in isolated villages.
Medicines Development for Global Health, a non-profit pharmaceutical organization, in partnership with the UNICEF/UNDP/World Bank/WHO Special Programme for Research and Training in Tropical Diseases (TDR), has developed moxidectin for human application.
“The most favorable long-term outcome of this research would be the incorporation of moxidectin into mass drug administration programs,” Budge stated. “Such a move would shorten the years required to accomplish the elimination of lymphatic filariasis. There are hundreds of millions of individuals who could be free from this disease in the future if we can eradicate it, and moxidectin may facilitate that progress.”
Koudou GB, Bjerum CM, Ouattara FA, Gabo TK, Goss CW, Lew D, Dje N’GN, King CL, Fischer PU, Weil GJ, Budge PJ. Moxidectin combination therapies for lymphatic filariasis: an open label, observer-masked, randomised controlled trial. The Lancet Infectious Diseases. May 6, 2025. DOI: 10.1016/S1473-3099(25)00111-2
This publication is based on research funded by (or in part by) the Gates Foundation. The conclusions and findings presented are those of the authors and may not necessarily represent the positions or policies of the Gates Foundation.
About Washington University School of Medicine
WashU Medicine stands out as a global frontrunner in academic medicine, encompassing biomedical research, patient care, and educational initiatives with 2,900 faculty members. Its research funding portfolio from the National Institutes of Health (NIH) ranks second among U.S. medical schools and has increased by 56% in the past seven years. Alongside institutional contributions, WashU Medicine dedicates over $1 billion annually to innovative training and research in both basic and clinical fields. Its faculty practice consistently ranks among the top five nationally, with more than 1,900 faculty physicians practicing across 130 locations and serving as the medical staff for Barnes-Jewish and St. Louis Children’s hospitals under BJC HealthCare. WashU Medicine has a rich history in MD/PhD training and has recently allocated $100 million towards scholarships and curriculum enhancements for its medical students, alongside offering outstanding training programs in every medical subspecialty, as well as physical therapy, occupational therapy, and audiology and communication sciences.
Originally published on the WashU Medicine website
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