Older Malaria Drug Regains Effectiveness Chloroquine cured malaria quickly and safely, at only pennies per treatment. But parasites became resistant. A new study shows that if chloroquine is taken out of use, parasites lose their resistance.
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Older Malaria Drug Regains Effectiveness

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Older Malaria Drug Regains Effectiveness

Older Malaria Drug Regains Effectiveness

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One of the biggest public health problems around the world is malaria. About a million children each year die from the disease. Drugs can cure it, but the parasites that cause malaria often develop resistance. The cheapest malaria drug has lost its effectiveness because of its widespread resistance. That has spoiled attempts to eradicate malaria. But now scientists have shown for the first time that drug resistance doesn't necessarily last forever. That gives hope that a cheap and safe malaria drug can be brought back.

NPR's Richard Knox has this report.

RICHARD KNOX: Chloroquine is one of the most important drugs of the last century. It cured malaria quickly, safely, at only pennies per treatment. In the 1950s and '60s, it was the mainstay of a global campaign to eradicate malaria. Then the malaria parasite mutated; it learned how to escape from chloroquine. By the early 1990s, the drug failed to cure as many as 80 percent of patients.

Dr. Peter Kazembe is a malaria expert in the tiny, impoverished African nation of Malawi. Most children with malaria there were dying in the early 1990s, despite chloroquine treatment.

Dr. PETER KAZEMBE (Malaria Expert): And so for us it was quite clear, if you, you know, if you have a drug that is only effective in 20 percent of the cases, then the whole program is doomed to failure.

KNOX: So Malawi took a controversial step. In 1993, it banned all chloroquine use.

Dr. KAZEMBE: It was a brave decision in many ways. Some of the well-known experts in malaria control were predicting doom.

KNOX: They worried that resistance would quickly develop to the second-line malaria drugs, and then nobody would have any effective treatments.

Fast-forward eight years. Christopher Plowe at the University of Maryland and his colleagues wanted to know the impact of Malawi's brave experiment. Without constant exposure to chloroquine, would the parasite's resistance fade away?

Dr. CHRISTOPHER PLOWE (University of Maryland): We looked for the genetic mutation that causes resistance, saw that it had gone from a rate of 85 percent in 1992 - a year before this switch from chloroquine - down to zero by 2001. And we were pretty surprised by that, and it led us to wonder whether now chloroquine might actually work clinically again.

KNOX: So they tested chloroquine against its replacement, a drug called SP, in Malawian children with malaria. SP cured only 16 out of 87 children, 21 percent. But chloroquine cured 79 out of 80 children, 99 percent. In other words, chloroquine regained its potency. Nobody had ever seen that before.

Plowe says it doesn't mean that doctors can go ahead and use chloroquine the way they used to.

Dr. PLOWE: Right now I think of Malawi as a little island of chloroquine-sensitive malaria surrounded by a sea of chloroquine resistance. If we start using chloroquine again there, parasites would become resistant again very quickly, just by migrating in from the nearby areas.

KNOX: But the research, in this week's New England Journal of Medicine, does have important implications. First, it's got specialists thinking about using chloroquine in combination with SP to prevent malaria in infants and pregnant women. In Malawi, up to half of pregnant women have malaria parasites in their blood.

Harvard malaria expert Dyann Wirth says the resurrection of chloroquine is important if only for this reason.

Dr. DYANN WIRTH (Harvard University): It's a very significant public health problem, and there are relatively few alternatives. And so in that particular situation, I think this is potentially very good news.

KNOX: Experts are also wondering if they can bring chloroquine back in a bigger way. But only in countries that have given it a long break, and only in combination with newer malaria drugs. That would be more expensive, about $3 per treatment compared to 10 cents for chloroquine.

Drug treatment will be necessary even if a malaria vaccine passes current tests. Experts expect a vaccine won't be good enough to throw out drug treatment altogether. And when it comes to drug treatment, malaria experts have learned their lesson: treating malaria with one drug or even two drugs at a time is a losing game.

Richard Knox, NPR News.

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