Malaysia, Thailand and Brazil are set to begin multinational Phase III clinical trials next year to evaluate a promising monoclonal antibody treatment developed by India's Serum Institute of India (SII) to tackle mosquito-borne pathogens causing dengue that threatens more than 5.6 billion people globally.
The trial follows a licensing agreement between Pune-based SII and the Drugs for Neglected Diseases initiative (DNDi) last year to jointly develop and ensure affordable access to the dengue therapy, which could become the world's first targeted treatment for the disease.
Expected to commence in the first quarter of 2027, the study will enrol around 1,000 participants across Malaysia, Thailand and Brazil — countries that continue to face recurring dengue outbreaks. The trial will be conducted through the Dengue Alliance, a partnership of dengue-endemic countries working to develop effective and accessible treatments.
The monoclonal antibody candidate, previously known as VIS513, has already completed pre-clinical studies and Phase I and II clinical trials with encouraging safety and efficacy results. SII is also conducting a pivotal Phase III trial in India while supplying the investigational medicine for the multinational study.
Public health experts say the development is significant because dengue management currently relies almost entirely on supportive care such as intravenous fluids, careful monitoring and hospital-based management to prevent complications. During large outbreaks, hospitals often struggle to cope with the surge in admissions.
"Treatments will be essential to tackling dengue. We need therapeutics that can prevent progression to the severe stage of the disease to save lives and reduce economic strain, not only on patients but also on public health systems," said Dr. André Siqueira, Head of Dengue at DNDi.
Climate change, rapid urbanisation and increased global mobility have contributed to the expanding spread of the Aedes mosquito, pushing dengue into newer regions, including parts of Europe where the disease was previously uncommon.
While vaccines have become available in recent years, experts note that coverage remains limited and effectiveness can vary depending on previous dengue exposure and circulating virus serotypes. Against this backdrop, an effective treatment is increasingly viewed as a critical missing component in global dengue control efforts.
Dr. Rajeev Dhere, Senior Scientific Advisor at SII, said the institute was pursuing both preventive and therapeutic approaches against dengue.
"The Serum Institute of India is committed to going all out in controlling dengue. We are working on both preventive and therapeutic applications to protect populations in dengue-endemic areas," he said.
Children, pregnant women and older adults remain particularly vulnerable to severe disease and are among the groups that stand to benefit most from an effective treatment.
According to DNDi, more than half the world's population now lives in areas at risk of dengue infection. Public health authorities warn that the disease is no longer confined to tropical countries and is increasingly emerging in new regions, including parts of Europe.
The international trial will be conducted with financial support from the European Commission's Directorate-General for Health Emergency Preparedness and Response Authority (DG HERA) in partnership with the French Development Agency. Last year, DG HERA committed €20 million to accelerate the development of two new dengue therapeutics.
European health authorities said dengue is no longer a challenge limited to tropical nations.
"More than half of the world's population now lives in areas at risk of dengue infection, and what was once considered a disease confined to tropical regions is increasingly affecting Europe," said Florika Fink-Hooijer, Director-General of DG HERA. She described the study as an important milestone in strengthening global preparedness against vector-borne diseases.
Researchers participating in the trial said climate change is fundamentally reshaping dengue epidemiology.
Brazil, which recorded more than 6.5 million dengue cases and over 5,000 deaths during its unprecedented 2024 outbreak, offers a stark reminder of the growing threat. Viviane Boaventura, researcher at the Oswaldo Cruz Foundation (Fiocruz), said climate change is driving outbreaks of "unprecedented magnitude, extended duration and expanding geographic distribution", making the search for an effective treatment increasingly urgent.
At present, existing dengue control strategies continue to rely largely on mosquito control and vaccines, whose effectiveness varies depending on previous exposure and circulating virus strains. An effective therapeutic could therefore become a crucial third pillar in dengue control by reducing severe illness even after infection occurs.
If successful, the ongoing initiative could deliver the first approved targeted treatment for dengue — offering a much-needed medical tool as countries confront increasingly frequent and unpredictable outbreaks in a warming world.
