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April 23, 2009 12:24 PM
Posted by Kristi Heim
The malaria eradication efforts of Seattle-based PATH are moving ahead today with the first human trials of one of its vaccine candidates -- a "whole parasite" vaccine made by Sanaria.
MIKE SIEGEL/SEATTLE TIMES
PATH's Malaria Vaccine Initiative, a global nonprofit consortium supported by about $450 million in grants from the Gates Foundation, is working with drug companies such as Sanaria to advance studies on various vaccine candidates.
"Initiation of this trial expands the spectrum of malaria vaccines in clinical development today," said MVI Director Christian Loucq. Conducting early trials with volunteers allows scientists to weed out vaccines that don't work and accelerate those that do, he said.
The PfSPZ vaccine is made in Sanaria's Maryland lab from P. falciparum parasites harvested by hand from the salivary glands of infected mosquitoes.
This trial will assess the vaccine's safety and efficacy by vaccinating more than 100 volunteers and then allowing malaria-infected mosquitoes to bite them, testing whether the vaccine offers protection. Malaria kills nearly a million people a year, mostly small children in Africa.
Another malaria vaccine supported by PATH, RTS,S developed by GlaxoSmithKline (GSK), is the most advanced, beginning its final phase of clinical trials this year in Africa.
Sanaria founder and CEO Stephen L. Hoffman was part of a team of military doctors trying to develop a malaria vaccine in the 1980s at the Walter Reed Army Institute of Research. There he worked with W. Ripley Ballou, who now heads malaria vaccine research for GSK.
Ballou's RTS,S malaria vaccine has proved effective in adults and children, reducing the risk of infection by about 35 percent. But Hoffman said that level of protection is too low.
"That's not a vaccine that could ever be considered for use in the developed world," he told Scientific American in an interview last year.
In the 1990s, Hoffman exposed himself to bites of 3,000 mosquitoes -- irradiated to weaken the malaria parasites they were carrying -- to infect himself with malaria, eventually becoming immune from the disease.
That early experiment formed the basis of Sanaria's approach, which is unique in deploying a weakened form of the whole malaria parasite harvested from the saliva of irradiated mosquitoes instead of using small portions of the parasite.
While the challenges associated with a vaccine based on live parasites had been widely viewed as insurmountable, Sanaria says it has developed new technologies and manufacturing capability.
The trials will be conducted by researchers at two sites in Maryland: the US Naval Medical Research Center in Bethesda and the University of Maryland School of Medicine in Baltimore.
Scientists from Seattle Biomedical Research Institute (SBRI), meanwhile, are working on a vaccine that uses genetic engineering to render malaria parasites harmless. SBRI is preparing its first vaccine candidate to enter clinical trials at Walter Reed this year. SBRI, which as about 100 researchers dedicated exclusively to malaria, will also open its own Malaria Clinical Trials Research Center later this year at its South Lake Union lab, where volunteers are paid to get bitten.