Mabloc, a biotechnology company developing monoclonal antibody therapies, has announced a strategic partnership with Instituto Butantan to co-develop and manufacture MBL-YFV-01, a breakthrough monoclonal antibody therapy for Yellow Fever Virus (YFV) infection, including emergency post-exposure use. The collaboration addresses an urgent unmet medical need as yellow fever outbreaks escalate in Brazil, with confirmed human cases in São Paulo, Minas Gerais, and Espírito Santo.
Promising Preclinical Results Demonstrate Therapeutic Potential
MBL-YFV-01 is a fully human monoclonal antibody developed using Mabloc's proprietary BRAID™ platform, which employs AI and bioinformatics to rapidly identify, optimize, and test potent antibodies. In a primate study published in Science Translational Medicine (2023), a single 50mg/kg dose of MBL-YFV-01 fully controlled viremia and prevented severe disease and death in 100% of treated primates. Additional primate studies published in JCI Insight (2025) demonstrated that different doses could be effective in protection from death and showed the drug's potential use as a prophylactic.
"The ability to intervene during the acute, life-threatening disease phase is where MBL-YFV-01 is unique, and while vaccination will protect most, there will still be many where it is not enough," said Michael Ricciardi, Ph.D., Director of Product Development at Mabloc. "This will be the first disease specific medicine for the treatment of yellow fever."
Addressing Critical Medical and Economic Burden
Despite the availability of a live attenuated vaccine, millions remain at risk due to low immunization rates, limited access, and rare but serious adverse events associated with vaccination. A 2019 study published in The Lancet Infectious Diseases found that high viral load was an independent predictor of mortality in yellow fever patients, with 100% of those with both high viral load and elevated neutrophil counts dying during hospitalization. MBL-YFV-01 lowers viral load and may offer a way to reduce deaths in severe cases.
The economic implications are substantial. In late-stage cases, liver transplantation is often the only lifesaving option, but it is costly and resource-intensive. According to a cost-modeling study published in PLOS ONE, liver transplantation can exceed $1.4 million in the first year and reach over $2 million per patient over 10 years. As yellow fever outbreaks expand, scalable alternatives like MBL-YFV-01 are critical for reducing mortality and economic burden.
Partnership Structure and Development Timeline
Under the agreement, Instituto Butantan will manufacture MBL-YFV-01 and lead the non-clinical and clinical studies to reach market authorization. The trial will focus on testing the monoclonal antibody's potential to treat patients with yellow fever and improve patient outcomes, supporting a regulatory submission to ANVISA, Brazil's national health authority.
"This partnership reinforces Butantan's strategy to invest in monoclonal antibodies — highly specific and innovative medicines — to treat and prevent infectious diseases that primarily affect developing countries and are often neglected by the global pharmaceutical industry," said Cristiano Goncalves, director of Innovation and Technology Licensing at Butantan. "The intention is to develop MBL-YFV-01 and to provide patients with this potential innovative treatment for yellow fever, which currently has no solution in the market beyond supportive care."
Scientific Foundation and Intellectual Property
The therapy builds on research funded by a multi-year NIH grant (Project #5R42AI155275) and is protected under U.S. patent US20210253675A1. The collaboration leverages Instituto Butantan's proven capabilities in biologics manufacturing and clinical operations, positioning the partnership to respond quickly to real-world outbreaks.
Together, Mabloc and Butantan aim to deliver one of the world's first post-exposure therapies for yellow fever, offering new hope to patients and public health systems facing the growing threat of viral outbreaks. The partnership represents a significant step forward in addressing a neglected tropical disease that continues to pose substantial public health challenges in endemic regions.
