Researchers Kick Off Lengthy Schistosoma Vaccine Trials

Schistosomiasis, a chronic infection that affects more than 200 million people, is prominent in both Latin America and sub-Saharan Africa.

David Diemert, MD

Longtime researchers of Brazilian disease are beginning an analysis of a possible vaccine for the area’s strain of schistosomiasis.

David Diemert, MD, Associate Professor of Microbiology, Immunology, and Tropical Medicine at the George Washington University School of Medicine and Health Sciences (GWU), and Jeffrey Bethony, PhD, a professor of the same fields at GWU, will lead the phase 1b safety and immunogenicity trials for a schistosoma vaccine after receiving funding from the National Institutes of Health.

The beginning of clinical trials was announced more than a decade since the 2 researchers first begun their research in Brazil. It will feature the first safety and immunogenicity trial for a vaccine administered to a population exposed to the particular schistosomiasis parasite, Diemert told MD Magazine.

Schistosomiasis, a chronic infection that affects more than 200 million people, is prominent in both Latin America and sub-Saharan Africa. The researchers’ vaccine would target the intestinal and liver conditions caused by Schistosoma mansoni, the cause of infections and deaths from the disease in the Americas.

Though current therapies are capable of stopping the strain, there’s still a need for prophylaxis measures, Bethony told MD Magazine.

“It’s prominent in the northeastern region of Brazil, and pretty much in different parts of the Caribbean, but in Brazil is where you can find a lot of transmissions,” Bethony said. “It’s been our experience, and with Brazilian collaborators, that it’s still a public health problem there.”

Researchers will analyze the safety and immunogenicity of candidate antigen Sm-TSP-2 (Alhydrogel) in as many as 60 adult healthy males and non-pregnant females, using a double-blind, randomized and controlled study structure.

The vaccine was previously tested for safety and immunogenicity in a phase 1 pilot study involving patient population at the Baylor College of Medicine Vaccine Treatment and Evaluation Unit. The patients administered the vaccine were not from areas where the disease is considered endemoic.

If elements of the vaccine, notably its proteins, show a strong immune response in patients of the forthcoming phase 1b trial, the researchers intend to test it in pediatric subjects — as the hope is it would eventually become a vaccine administered to people at a young age. But pediatric tests for efficacy, safety, and immunogenicity would require another series of phase 1 and 2 trials, Diemert said.

“But adults still do get infections,” Diemert said. “Eventually, we’ll be proposing a proof-of-efficacy trial in an adult population to see the impact of vaccinating people, to see if they’re infected compared to a control population. A trial involving children would be done in parallel to that.”

Jeffrey Bethony, PhD

Because of the novel nature of the trials and because Sm-TSP-2 is a recombinant vaccine that requires more time for production than a whole parasite vaccine, researchers are anticipating a long time before any vaccine is available in the market — even if it hits all its clinical marks.

“If nothing comes up, we’re at looking at 10 to 15 years before it’s licensed,” Bethony said. “If everything shown to be safe and immunogenic in this trial, the efficacy trial would be where we’d show it’s effective and preventive, too.”

That said, it’s already been long time coming for a team of researchers from GWU, Baylor, Texas Children’s Hospital Center for Vaccine Development, and the René Rachou Institute.

“It’s really a collaborative effort,” Diemert said. “We have had colleagues in Brazil for many years now who have played an important role in getting the study done."

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