Compounds From Okinawan Marine Sponges Show Promise Against Leishmaniasis

A class of natural compounds known as onnamides, extracted from marine sponges collected off the coast of Okinawa, has demonstrated potent antiparasitic activity against Leishmania major, a species responsible for cutaneous leishmaniasis. The study, conducted by a multidisciplinary team based in Japan, represents an early but promising step toward developing new treatment options for the neglected tropical disease.

Leishmaniasis affects an estimated 12 million people in over 90 countries. Transmitted through sandfly bites, it is caused by protozoan parasites of the genus Leishmania. Cutaneous forms of the disease produce chronic skin ulcers, which can lead to disfigurement, social isolation, and psychological distress. The burden is greatest in low-income regions where healthcare resources are limited.

Treatment for leishmaniasis remains suboptimal. Currently available drugs, such as pentavalent antimonials and amphotericin B, are often associated with significant toxicity, lengthy treatment courses, and growing rates of drug resistance. No licensed vaccines are available, and diagnostic tools are often inadequate.

Bioactive compounds isolated from marine sponges

In this study, scientists led by Associate Professor Kanami Mori-Yasumoto from Tokyo University of Science screened extracts from marine sponges of the Theonella genus, which are known to harbor diverse secondary metabolites. From these samples, the researchers isolated 10 compounds belonging to the onnamide family.

Two compounds, onnamide A and 6,7-dihydro-onnamide A, stood out for their strong leishmanicidal activity and low cytotoxicity toward human cells. Laboratory tests showed that these compounds outperformed existing treatments in terms of potency and selectivity.

Potential new pathways for drug development

Further analysis suggested that onnamide A may operate through a mechanism distinct from amphotericin B, which targets the sterol components of the parasite's cell membrane. This finding could be particularly relevant for overcoming existing drug resistance.

The team also reported the structural identification of a previously unknown compound, onnamide G, adding to the chemical diversity within the onnamide group. The characterization of onnamide G offers new opportunities to explore structure–activity relationships in this class of molecules.

Suitability for drug development

The researchers noted that onnamides exhibit favorable properties, including strong activity at low concentrations, which may translate into shorter treatment durations and reduced dosing frequency. However, they cautioned that more work is needed to evaluate pharmacokinetics, safety in animal models, and long-term efficacy before clinical development can proceed.

The project is currently being advanced under the Drug Discovery Booster initiative supported by the Japan Agency for Medical Research and Development (AMED), which seeks to bridge early-stage discoveries and therapeutic applications.

Efforts are also underway to investigate the feasibility of sustainable compound production using symbiotic bacteria associated with marine sponges. Culturing these bacteria may provide a scalable and environmentally responsible source of onnamides for future drug development.

Reference: Jomori T, Higa N, Tyas TA, et al. Onnamides and a novel analogue, onnamide g, as potent leishmanicidal agents. Mar Biotechnol. 2025. doi:10.1007/s10126-025-10494-1

This article has been republished from the following materials. Note: material may have been edited for length and content. For further information, please contact the cited source. Our press release publishing policy can be accessed here.