A gene in malaria parasites could explain why drugs to treat the disease fail, researchers have said.
Resistance to malaria drugs can make treatment harder
Previous research found mutations in a gene called pfcrt helped malaria parasites escape the action of the antimalaria drug chloroquine.
Now Molecular Cell reports scientists have found faults in the same gene that make other antimalaria drugs fail.
Researches at the Liverpool School of Tropical Medicine worked with the US Albert Einstein College of Medicine.
They uncovered the new mutations in the pfcrt gene while they were creating strains of malaria parasite that resisted treatment to malaria drugs other than chloroquine.
Chloroquine is one of the most affordable and widely used antimalarial drugs, but resistance has become increasingly common.
Two drugs used to treat mild to moderate cases of chloroquine resistance are halofantrine and amantadine.
Dr David Fidock and colleagues found as resistance to these two drugs increased, the parasites lost their resistance to chloroquine.
When they looked closer, they found new mutations in the pfcrt gene.
One of these mutations has been found in a strain of malaria from south-east Asia.
The scientists said this suggests what they have discovered in the laboratory could have implications for malaria treatments in the real world.
Dr Colin Sutherland from the Malaria Reference Laboratory at the London School of Hygiene and Tropical Medicine said: "This work represents a step forward in our understanding of how malaria parasites escape the action of drugs used in treatment and prophylaxis [prevention].
"Although the major new findings presented concern drugs that are not now widely used for malaria treatment, they provide evidence that this particular gene, pfcrt, is involved in resistance to a number of drugs in addition to chloroquine.
"Field studies are needed to determine if these new forms of pfcrt are involved in the failure of treatment in natural malaria infections.
"Halofantrine, one of the drugs studied here, is related to the drug lumefantrine, now being widely deployed across Africa and Asia in combination with artemether.
"It may now be possible to monitor in these areas for any change towards these newly identified mutant forms, as an early warning system for the emergence of new outbreaks of resistant malaria.
"This could help prolong the useful life of our current generation of combination drugs," he said.