Nobel Prize in Medicine for therapies against parasites

Three scientists share the price of malaria and nematode drugs

Soil bacteria and a Chinese herb were the sources of two pioneering medicines in the fight against parasites. © Nobel Assembly / Karolinska Institutet
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Against Roundworms and Malaria: The Nobel Prize in Medicine goes to the discoverers of breakthrough medicines for parasites. Half of the price goes to the Irishman William C. Campbell and the Japanese Satoshi Ōmura for the development of the agent avermectins against the river blindness caused by roundworms. The other half of the Nobel Prize in Medicine will be given to the Chinese Youyou Tu, who discovered an important antimalarial drug based on a 700-year-old prescription.

Mosquito-borne parasites have plagued humanity for centuries. Among the most well-known and notorious diseases of this kind is the unicellular malaria. Also widespread parasitic pathogens are various thread worms: If they infect the lymphatic system, usually swell the legs and it creates the unpleasant and stigmatizing elephantiasis. In the eyes, such worms can cause so-called river blindness.

Especially in tropical regions, various species of mosquitoes transmit the parasites, particularly affected many developing countries. For a long time there was little effective antidote. But in the early 1980s, the medicine received two powerful weapons against these parasites.

Omura and Campbell found the highly potent avermectin in the bacterium Streptomyces avermitilis. © Nobel Assembly / Karolinska Institutet

Soil bacteria against roundworms

The Japanese microbiologist Satoshi Ōmura searched in the 1970s for antibiotically active natural products. As potential producers he had soil bacteria from the group of streptomycetes in view. Although these are difficult to cultivate, they had previously proved to be a blessing: as early as 1952, the Nobel Prize in Medicine for the discovery and isolation of the antibiotic streptomycin obtained from it went to microbiologist Selman Waksman.

The most promising of his cultures sent Ōmura to the Irishman William C. Campbell, including bacteria of the species Streptomyces avermitilis. The parasitologist Campbell recognized in his laboratory in the United States how effectively a substance produced by these bacteria was resistant to thread worms: when mixed with the feed of laboratory mice, it reliably killed all the worms from. The isolated agent was named after the bacteria avermectin. display

This substance, and its more advanced and even more effective form, ivermectin, was the basis for a whole new class of drugs for both human and farm animals. The parasitic diseases elephantiasis and river blindness were brought to the verge of extinction by the therapies provided by Ōmura and Campbell.

Based on traditional recipes of Chinese healing Tu spotted the active ingredient Artemisinin. Nobel Assembly / Karolinska Institutet

Ancient recipe against malaria

The fight against malaria was dehydrated in the late 1960s: the drug quinine slowly but surely lost its efficacy the more resistance the parasites of the genus Plasmodium caused. The Anopheles mosquitoes, which spread the pathogens in a sting, were to be eradicated with the insect killer DDT, but this plan also failed.

In search of new antimalarial therapies, Chinese researcher Youyou Tu searched her country's traditional medicine. Many different herbs should help, but the results of the research were initially contradictory. Finally, the scientist put a recipe that was around 700 years old on the right path: from the one-year-old cough (Artemisia annua), Tu finally isolated the active ingredient artemisinin.

Tu could show that artemisinin kills the malaria parasites in both humans and animals. Since it attacks the plasmodia at an early stage of development, it is particularly effective. Also this drug became the pioneer of a whole class of new medicines.

Artemisinin and avermectin have fundamentally changed and expanded the therapeutic options for parasites. Ivermectin is used practically all over the world today: it is highly effective, has few side effects and is quick and readily available. Artemisinin is still used to fight malaria and reduces the death rate by 20 percent and in children by as much as 30 percent. In Africa alone, this means saving 100, 000 lives a year. For these reasons, the Nobel Committee calls the benefits of the discoveries of Ōmura, Campbell, and Tu humanity "immeasurable."

(Nobel Assembly at Karolinska Institutet, 05.10.2015 - AKR)