Mabloc and Instituto Butantan Partner to Advance First-in-Class Antibody Therapy for Yellow Fever

WASHINGTON and SÃO PAULO, Nov. 18, 2025 /PRNewswire/ -- Mabloc, a biotechnology company developing monoclonal antibody therapies for multiple disease indications, today announced a strategic partnership with Instituto Butantan, one of the world's leading biomedical research centers, to co-develop and manufacture MBL-YFV-01 — a breakthrough monoclonal antibody therapy for Yellow Fever Virus (YFV) infection, including emergency post-exposure use.

This partnership comes amid escalating yellow fever outbreaks in Brazil, including confirmed human cases in São Paulo, Minas Gerais, and Espírito Santo. Despite the availability of a live attenuated vaccine, millions remain at risk due to low immunization, limited access, and rare but serious adverse events. A post-exposure therapeutic option remains an urgent and unmet medical need.

About the Therapy

MBL-YFV-01 is a fully human monoclonal antibody optimized and tested by Mabloc, a biotech specializing in monoclonal antibody isolation and development utilizing the proprietary BRAID™ platform, which uses 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. This was followed up with additional primate studies published in JCI Insight (2025),  where it was shown that different doses could be effective in protection from death and demonstrated how the drug could also be used 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. "With Butantan's proven capabilities in biologics manufacturing and clinical operations, this partnership allows us to respond quickly to real-world outbreaks and bring a desperately needed therapy into the hands of physicians and patients. This will be the first disease specific medicine for the treatment of yellow fever."

The therapy builds on research funded by a multi-year NIH grant (Project #5R42AI155275) and is protected under U.S. patent US20210253675A1.

Clinical and Economic Significance

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.

"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 who leads the partnership with Mabloc. "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."

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.

Terms of the Partnership

Under the agreement, Instituto Butantan will manufacture MBL-YFV-01 and lead the non-clinical and clinical studies in order to reach market authorization of the product. The trial will focus on testing the potential of the mab to treat patients with yellow fever and improve patient outcome which will support a regulatory submission to ANVISA, Brazil's national health authority.

"This collaboration reflects our mission to respond to public health emergencies with scientific innovation and real-world impact," said Cristiano Goncalves.

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.

About Instituto Butantan
Instituto Butantan is one of the world's leading biomedical research and biologics manufacturing institutions. Based in São Paulo, Brazil, Butantan supports public health through vaccine development, immunobiological production, and scientific research across immunology, biotechnology, molecular biology, and more. It is the primary supplier of immunobiologicals to Brazil's national health system (SUS). For more information, visit butantan.gov.br.

About Mabloc
Mabloc is redefining antibody discovery through BRAID™, its proprietary AI-powered platform that accelerates the path from target to treatment. By combining deep learning with advanced bioinformatics, Mabloc identifies rare, highly potent antibodies that address infectious diseases, envenomation, oncology, and neurodegenerative disease indications. Mabloc delivers life-saving antibody therapies faster, smarter, and at scale. For media inquiries or more information, visit www.mabloc.com.

Contact

Media & Partnerships: Mike Ricciardi, [email protected]

SOURCE Mabloc