Chemically altered osteoporosis drug kills malaria parasite in mice
March 1, 2012
With malaria still responsible for millions of untimely deaths in more than 90 countries each year, the search for effective antimalarial drugs, vaccines and mosquito repellents continues to heat up. Recently, researchers at the University of Illinois (UI), led by chemistry professor Eric Oldfield, found that a chemically-altered form of a commonly prescribed osteoporosis drug can easily enter red blood cells and dispatch malaria parasites without harming the host (in this case, a mouse). That's potentially huge news for the countless thousands who continue to suffer from this recurrent, debilitating and all-too-often fatal disease.
"The lead compounds are chemically modified forms of the bisphosphonate osteoporosis drugs Actonel (Risedronate) and Zometa (Zoledronate)," Oldfield said. A typical hurdle facing many anti-malarial drugs is how to get them into the red blood cells where malaria-causing Plasmodium parasites reside. "The modified forms include a long lipid tail that helps them pass through the lipid-rich membrane of red blood cells, and also enhances the drug's ability to bind to the target enzyme, geranylgeranyl diphosphate synthase (GGPPS)," he added.
As it turns out, the promising new compound, dubbed BPH-703, impacts a biochemical pathway (termed isoprenoid biosynthesis) crucial for the parasite's sustenance and self-defense from the host's immune system. It works by effectively inhibiting GGPPS, an enzyme which is essential to the isoprenoid biosynthesis process.
The team observed the properties of nearly 1,000 different substances. "We found that compounds that were really active had a very long hydrocarbon chain," Oldfield explained. "These compounds can cross the cell membrane and work at very low concentrations." Study co-author Yonghui Zhang invented BPH-703, and pointed out that his team was the first to identify the GGPPS enzyme as a legitimate target in the battle against malaria.
In recent years, heavy hitters like Bill Gates and the World Health Organization have been ramping up efforts to eradicate malaria in all regions of the globe, but despite the millions of dollars being spent, drug-resistant strains of malaria continue to emerge.
"It's important to find new drug targets because malaria drugs last only a few years, maybe 10 years, before you start to get resistance," Oldfield said. "The parasites mutate and then you lose your malaria drug." Since many existing anti-malarial drugs frequently exhibit severe side-effects, the promise of a potentially non-toxic therapeutic comes as welcome news, indeed.
Source: University of Illinois