In this effort, Associate Professor Kanami Mori-Yasumoto and her research team have made a significant breakthrough in the fight against leishmaniasis. Yet this neglected tropical disease continues to affect more than 12 million people worldwide. The research was published in the peer-reviewed journal Marine Biotechnology, online September 5, 2025. They show for the first time that onnamide A, a natural compound isolated from marine sponges found in Manza, Okinawa, Japan, has the potential therapy by targeting the parasite L. major through a novel mechanism.
Leishmaniasis is endemic in over 90 countries and threatens about 350 million people worldwide. Infected sandflies spread the disease through their bites. It can present in a wide variety of ways, from cutaneous lesions to life threatening visceral disease. As the term neglected tropical diseases implies, despite its impressive toll on human health, leishmaniasis is poorly studied and funded.
The Potential of Onnamide A
The finding of onnamide A is a key piece in the continued evolution of the treatment landscape for leishmaniasis. Unlike the standard treatment amphotericin B—which primarily targets ergosterol, a cholesterol-like compound, in the parasite’s cell membrane—onnamide A does not act directly on the cell membrane. Firstly, it combats L. major through an entirely different pathway. This interesting new mechanism may be particularly advantageous at combating drug resistance that frequently plagues currently available therapeutic avenues.
In addition, they discovered onnamide A acted in a very unique way. They think such a strategy might increase its effectiveness and provide a nice adjunct to existing treatment regimens. Resistance to these older medications has become a challenge, particularly with regard to tropical diseases such as leishmaniasis. This highlights the importance of alternative compounds, like onnamide A, to addressing this rising global health challenge.
…surprisingly, the researchers didn’t stop there with their big discoveries—in addition to onnamide A, they isolated onnamide G. This new compound deepens our understanding of the structural diversity and potential mechanism(s) of action for these marine-derived compounds. Aside from its potential therapeutic impact, this discovery highlights the need to explore natural products as sources of pharmaceutical innovation.
Implications for Global Health
The team’s findings mark a significant milestone in Japan’s contribution to the research of neglected tropical diseases. Onnamides have evolved as potent lead compounds. If they did, they’d free up millions of treatment regimens for those currently suffering from leishmaniasis. Spurred by ongoing research through the AMED Drug Discovery Booster program, optimism abounds. Our scientists are confident that they can validate these natural compounds for widespread clinical use in the near future.
The global implications of this research are huge. With an estimated 350 million people at risk of leishmaniasis infection, especially among the most vulnerable populations, better treatments are urgently needed. Our novel therapies are all aimed at reducing suffering. Beyond that, they are uniquely placed to help prevent and control disease from taking hold in endemic areas. Importantly, the research community is already focusing on solutions like onnamides. They are intended to strengthen our public health response, helping to improve outcomes for those at risk.
Next Steps in Research
The finding of the onnamides is an exhilarating initial step. We need to do more studies to really understand what their potential could be as treatment options for leishmaniasis. The research team is currently engaged in further in-depth studies. They’re particularly interested in studying how effective and safe these compounds are in real life clinical settings. This stage will be critical for determining whether onnamides can transition from laboratory findings to practical applications for patient care.
Continued research and development efforts demonstrate the growing recognition of neglected tropical diseases. These initiatives are aimed at supporting the invention of new approaches to treat and ultimately defeat these diseases. Researchers are enthusiastic about the possibility marine natural products hold. They’re convinced these resources can produce new therapeutic candidates that will deepen and accelerate today’s global health efforts.