October 21, 2015
Three scientists were jointly awarded the Nobel Prize in Physiology or Medicine 2015 earlier this month for their pioneering work to develop novel therapies for treating some of the world’s most devastating parasitic diseases. The prize recognises the work of William C. Campbell, Satoshi Ōmura and Youyou Tu, whose research provided new treatments for parasitic roundworm and malaria infections.
Parasitic roundworms are some of the most common parasites of humans and animals. While some infect the gastrointestinal tract, others transmitted by biting insects cause diseases such as onchocerciasis, also known as river blindness, and lymphatic filariasis, which can lead to swelling of the limbs and thickening of the skin, causing elephantiasis. Together with malaria, caused by unicellular parasites that infect red blood cells, these diseases threaten over half of the world’s population. The people most at risk of these diseases are among the most vulnerable, and these parasites infect hundreds of millions of people every year in sub-Saharan Africa, South and Central America and South and South-East Asia.
William C. Campbell, Research Fellow Emeritus at Drew University, USA, and Satoshi Ōmura, Professor Emeritus at Kitasato University, Japan, share half the prize for their discovery of avermectin, a class of compounds with potent anti-parasite properties. In the early 1970s, at the Kitasato University in Japan, Ōmura was searching for useful biopharmaceutical compounds from soil-dwelling microorganisms. In 1973, he isolated a promising bacteria, Streptomyces avermectinius (avermitilis), from soil collected near a golf course in Ito. Further testing of bacterial cultures by Campbell at the Merck Institute for Therapeutic Research yielded the avermectins and the more powerful, semi-synthetic derivative ivermectin. In 1987, once the effectiveness of ivermectin against onchocerciasis had been demonstrated, Merck committed to donating the drug for as long as it was needed to those who needed it. This mandate was expanded to include lymphatic filariasis in 1998 and to date, over 2 billion ivermectin treatments have been donated.
The other half of the Nobel Prize was awarded to Youyou Tu, a Chinese scientist from the China Academy of Traditional Chinese Medicine, who used her expertise in Chinese and Western medicines to re-discover artemisinin as a treatment for malaria. In the late 1960s and early 1970s, faced with resurgent malaria in Southern China and devastating losses of North Vietnamese fighters to the disease, Mao Zedong set up a secret drug discovery project known only as Project 523. Recruited to this secret endeavour, Tu turned to traditional Chinese remedies for a solution, discovering the potential of sweet wormwood (Artemisia annua) to treat malaria in the 4th century Chinese text The Handbook of Prescriptions for Emergencies. Through careful experimentation, Tu and her team extracted and identified artemisinin, the active ingredient responsible for killing malaria parasites.
“The global impact of their discoveries and the resulting benefit to mankind are immeasurable” said Hans Fossberg, a member of the Nobel Assembly, when announcing the award. In recognising the work of Campbell, Ōmura and Tu, this award highlights the importance of drug development for neglected tropical diseases. Ivermectin has been successfully used to eliminate onchocerciasis in most Latin American countries where the disease was endemic, including most recently Mexico, while the use of artemisinin has significantly reduced mortality rates associated with malaria infection. As we move towards the 2020 deadline of the London Declaration on Neglected Tropical Diseases, prioritising research and development is key to saving and improving the lives of millions of people more, and ultimately to eliminate disease like onchocerciasis.