Scientists have discovered a compound that could lead to the development of a new antimalarial drug. Most of the malaria risk zone is resistant to chloroquine, which together with quinine forms the traditional antimalarial drugs used for decades. “We’re quickly running out of therapeutic options for malaria”, explained Michael Roscoe a biochemist involved in the study, “the parasite has gained a high level of resistance to the best and least expensive malarial drugs that are available.” The newly discovered compound (T3.5) not only kills the parasite that causes malaria, but also augments the effects of quinine in strains that have become resistant.
About half the world’s population is at risk from malaria and it’s widespread in regions of Africa, Asia, and South America. The disease killed 880,000 people in 2006, with a child dying every 30 seconds. However malaria is preventable and curable; the Maldives, Tunisia and the United Arab Emirates have all succeeded in eliminating the disease.
At present the best drugs available are Artemisinin Combination Therapies (ACTs), which combine the drug artemisinin with other drugs with different targets. This reduces the chance of choosing a mutation that is resistant, and it’s a principle currently being used in the treatment of TB and HIV–AIDS. ACTs are effective but unfortunately artemisinin is expensive. T3.5 on the other hand is cheap and easy to make, kills the most deadly species of the parasite plus two others, and can enhance quinines antimalarial abilities.
Causes of malaria
Malaria is caused by the parasite Plasmodium and carried between hosts by mosquito bites. An infected mosquito bites a human and the parasite makes
its way to the liver in approximately 30 minutes. Once in the liver the parasite starts to reproduce, though some parasites lay dormant for years. The parasite then moves further into the blood stream and breaks and enters the red blood cells. Inside the cells the parasites break apart the haemoglobin and eat the amino acids. Further reproduction also occurs at this stage. Red blood cells that have been infected burst and start infecting more red blood cells. This cycle repeats itself and reduces the body’s oxygen supply.
The cycle of the parasite also marks the cycle of the symptoms of malaria, which set in 10-15 days after being bitten. Symptoms include fever, headaches, and vomiting. If malaria is left untreated it can be fatal as it interrupts the blood supply to vital organs.
Treating and prevention
The World Health Organisation (WHO) recommends the following steps to treat and prevent malaria:
- Quickly treat the disease (within 24 hours)
- Use mosquito nets which have been sprayed with long-lasting insecticide
- Spray walls and roofs (wherever mosquitoes rest) with insecticide
- Give pregnant woman periodic treatment to rid the placenta of parasites.
The cost of fighting malaria is high; costs in the worst afflicted countries can make up 40% of their overall health costs. Mosquito nets have proven to be very cost-effective, but ACTs needed to treat the disease are expensive. The parasite is also becoming resistant to the main insecticides and it will take a long time and be expensive to develop new ones. This is a particular problem in Africa.
The research behind the new compound, “Discovery of dual function acridones as a new antimalarial chemotype” Kelly et al., was published on Wednesday, 8 April, in Nature. The scientists wanted to design a compound that could overcome the resistance to quinolines. They took samples of the deadliest forms of the species from different regions, and screened hybrid molecules for those that best fought off the parasite.
T3.5 managed to fight a multi-drug resistant strain infection in mice. The compound also enhanced the effects of quinine, cheaper than ACTs, in resistant strains. The discovery makes the possibility of a new cheaper drug to fight malaria in the future hopeful. There still needs to be further animal trials and then human trials before T3.5 will be available in the form of a drug.