Nobel Prize in Physiology or Medicine Awarded to Researchers Focused on Parasitic Infections

the Infectious Disease Advisor take:

The Nobel Assembly at Karolinska Institutet today decided to award the 2015 Nobel Prize in Physiology or Medicine with one half jointly to William C. Campbell, PhD, and Satoshi Ōmura, PhD, for their discoveries concerning a therapy against infections caused by roundworm parasites and the other half to Tu Youyou for her discoveries concerning a therapy against malaria.

Dr. Campbell and Dr. Ōmura discovered a new drug, avermectin, the derivatives of which have radically lowered the incidence of river blindness and lymphatic filariasis, as well as showing efficacy against an expanding number of other parasitic diseases. Tu YouYou discovered artemisinin, a drug that has significantly reduced the mortality rates for patients with malaria.

After decades of limited progress in developing durable therapies for parasitic diseases, the discoveries by this year's Laureates radically changed the situation.

Satoshi Ōmura, a Japanese microbiologist and expert in isolating natural products, focused on a group of bacteria, Streptomyces, which lives in the soil and was known to produce a plethora of agents with antibacterial activities, including Streptomycin. Dr. Ōmura isolated new strains of Streptomyces from soil samples and successfully cultured them in the laboratory. From many thousand different cultures, he selected about 50 of the most promising, with the intent that they would be further analyzed for their activity against harmful microorganisms.

William C. Campbell, an expert in parasite biology working in New Jersey, acquired Ōmura's Streptomyces cultures and explored their efficacy. Dr. Campbell showed that a component from one of the cultures was remarkably efficient against parasites in domestic and farm animals. The bioactive agent was purified and named avermectin, which was subsequently chemically modified to a more effective compound called Ivermectin. Ivermectin was later tested in humans with parasitic infections and effectively killed parasite larvae. 

Malaria was traditionally treated by chloroquine or quinine, but with declining success. By the late 1960s, efforts to eradicate malaria had failed and the disease was on the rise. At that time, Tu Youyou in China turned to traditional herbal medicine to tackle the challenge of developing novel malaria therapies. 

From a large-scale screen of herbal remedies in malaria-infected animals, an extract from the plant Artemisia annua emerged as an interesting candidate. However, the results were inconsistent, so Tu YouYou revisited the ancient literature and discovered clues that guided her in her quest to successfully extract the active component from Artemisia annua. 

Dr. Tu was the first to show that this component, later called artemisinin, was highly effective against the malaria parasite, both in infected animals and in humans. Artemisinin represents a new class of antimalarial agents that rapidly kill the malaria parasites at an early stage of their development, which explains its unprecedented potency in the treatment of severe malaria.