Malaria infects around a quarter of a million people a year and kills some 800,000 – mostly children in Africa – and resistance to a key treatment, artemisinin combination therapy, or ACT, is on the rise. Most available drugs target the parasite during the blood stage of its lifecycle, as this is when symptoms are observed. Up to now, it was not clear how those drugs affected the parasite’s other life stages – in particular, in the liver and sexual stages, when the parasite takes up residence in the human liver, and when it reproduces.
The researchers developed experimental tests, or assays, to test how the drugs behaved in these different life stages in three species of the parasite: Plasmodium falciparum — the most common human parasite in Africa, and two frequently used rodent models, P. berghei and P. yoelii. Their study in PLoS Medicine (21 February 2012) noted that several compounds which target the parasite’s blood stage were also effective in the two other stages. They also found that most of the drugs that target P. falciparum were also effective in treating another major human form, P. vivax.
The study will help design more effective combination therapies, the authors said, adding that similar assays could also be developed to speed up the testing and development of drugs for other pathogens. “Now we can screen thousands of drugs in a day,” said lead author Michael Delves, a researcher at Imperial College London, United Kingdom. “Hopefully this will accelerate our progress — if we can show a drug cures the symptoms, and that it can block transmission, that’s the sort of drug you want to push through trials as quickly as possible.” “Breaking the cycle of transmission is one of the panaceas we’re looking for — it’s up there with a vaccine,” said Scott Filler, senior adviser for malaria at The Global Fund to Fight AIDS, Tuberculosis and Malaria, in Switzerland. David Guttery, an expert in sexual stage development at the University of Nottingham, United Kingdom, said the paper “could have significant influence on future drug development”.
Originally Published 2012-03-20