Presentation Speech by Professor Hans Forssberg, Member of the Nobel Assembly at Karolinska Institutet, Member of the Nobel Committee for Physiology or Medicine, 10 December 2015

Your Majesties, Your Royal Highnesses, Esteemed Nobel Laureates, Ladies and Gentlemen,

All around us – in nature, on our skin and in our bodies – a constant power struggle is under way between myriads of microscopically small creatures that are fighting for their survival. Many are important constituents in nature’s ecosystems, while others attack us humans and cause disease and death. This year’s Nobel Prize in Physiology or Medicine is awarded to scientists who have enlisted the help of nature and made use of weapons from this power struggle in order to develop drugs against parasites that have plagued humankind since ancient times.

Parasitic roundworms cause lymphatic filariasis and river blindness. These are life-long diseases that have afflicted hundreds of millions of people in the poorest parts of the world. Satoshi Ōmura of Japan and William Campbell of the United States have made discoveries that have led to a drastic decline in these diseases and that will hopefully eradicate them within ten years.

It began with Satoshi Ōmura’s search for natural substances that could be used in producing new drugs. He became an expert in culturing Streptomyces, a type of soil bacteria known to produce antibiotic substances. He travelled around and collected thousands of soil samples from all over Japan which he used for culturing bacteria. In one of Ōmura’s bacteria cultures, which was sent to William Campbell’s laboratory, a whole new strain of Streptomyces was discovered – one that would change the world.

In Campbell’s laboratory, extracts from these cultures were given to mice that had been infected with roundworms. One of the extracts was remarkably effective, killing all the worms. Campbell purified the active component, which was given the name Avermectin. With the help of chemists, it was modified to become even more effective. The new substance was called Ivermectin, and it turned out to have an extremely powerful effect on parasites in farm and domestic animals. Campbell now wanted to test whether this drug was equally effective in humans, and he helped start clinical studies on patients with river blindness. A single dose was enough to kill the larval form of the worm that infects the eyes. This was the beginning of an anti-parasite drug that has saved hundreds of millions of people from severe disabilities.

Malaria is caused by parasites that are spread by mosquitos. The disease infects the red blood cells and leads to fever, shivering and in severe cases encephalitis. Every year half a million people die of malaria: most of them children. During the 1960s and 70s, Tu Youyou took part in a major Chinese project to develop anti-malarial drugs. When Tu studied ancient literature, she found that the plant Artemisia annua, or sweet wormwood, recurred in various recipes against fever. She tested an extract from the plant on infected mice. Some of the malaria parasites died, but the effect varied. So Tu returned to the literature, and in a 1700-year-old book she found a method for obtaining the extract without heating up the plant. The resulting extract was extremely potent and killed all the parasites. The active component was identified and given the name Artemisinin. It turned out that Artemisinin attacks the malaria parasite in a unique way. The discovery of Artemisinin has led to development of a new drug that has saved the lives of millions of people, halving the mortality rate of malaria during the past 15 years.

Professors William Campbell, Satoshi Ōmura and Tu Youyou:
Your discoveries represent a paradigm shift in medicine, which has not only provided revolutionary therapies for patients suffering from devastating parasitic diseases, but also promoted well-being and prosperity for individuals and society. The global impact of your discoveries and the resulting benefit to mankind are immeasurable.

On behalf of the Nobel Assembly at Karolinska Institutet, I wish to convey to you our warmest congratulations. May I now ask you to step forward to receive the Nobel Prize from the hands of His Majesty the King.