The discovery of Ivermectin is actually a fascinating story. Ivermectin comes from a golf course in Japan. As far as I know its never been found anywhere else in nature.
Discovery of Ivermectin
Discovery of Ivermectin
In the late 1960s and early 1970s, Satoshi Ōmura (*1935), a microbiologist and bioorganic chemist at Tokyo’s Kitasato Institute, hunted for new sources of pharmaceuticals. He knew that some existing drugs, including antibiotics, had been derived from compounds found in nature. So he developed screening methods to identify medicinally promising compounds from soil. His team collected thousands of soil samples from around Japan, cultured bacteria from them, and screened each culture for medicinal potential.
In 1971, Ōmura took a sabbatical in the laboratory of Max Tishler (1906–1989), an eminent professor of chemistry at Wesleyan University in the U.S. A year earlier, Tishler had retired from an illustrious research career at the pharmaceutical company Merck. Before returning to Japan in 1973, Ōmura arranged a pioneering agreement between the company and the research institute. Kitasato would continue to collect samples and screen them, and then send the most promising ones to Merck Research Laboratories in Rahway, New Jersey, for testing and development. The institute would receive royalties from any products that were commercialized through the partnership. At Merck Research Labs, a team led by parasitology specialist William Campbell (*1930) began testing the samples as potential treatments for parasitic worms. A veterinary scientist and zoologist by training, Campbell identified compounds that could be effectively developed as drugs for livestock and other animals. To test potential treatments, the Merck researchers first infected mice with nematodes and then fed each mouse a different culture sample supplied by Ōmura’s team. They found that one culture was extraordinarily effective at ridding mice of worm infestations.
This culture was derived from soil collected near a golf course in Kawana, about 80 miles southwest of Tokyo. Ōmura identified the bacterium in that culture as a new strain, which was ultimately christened Streptomyces avermectinius. The Merck team isolated the active component produced by the bacterium and named it “avermectin.” They found that avermectin is actually a combination of eight closely related compounds. The researchers began chemically modifying the compounds, tweaking their molecular structures slightly to see if they could make avermectin even more potent against parasites and safer for the animals being treated. By synthesizing thousands of similar compounds, Merck scientists found that, with slight chemical modification, some of the avermectin compounds displayed enhanced activity as well as safety. They dubbed the resulting pair of avermectin derivatives “ivermectin.” The mixture was 25 times more potent than existing treatments for parasitic worms. Further testing at Merck showed that ivermectin could also fight infestations by mites, ticks and botfly parasites that cause huge economic losses in the livestock industry. It was effective against parasites in horses, cattle, pigs, sheep and dogs, and was largely nontoxic to these animals. These gratifying results led Merck to commercialize ivermectin as a veterinary treatment beginning in 1981. Starting in 1987, the drug was also marketed to the public under the brand name Heartgard® (now sold by the animal-health company Merial) to prevent heartworms in dogs. These products quickly became the top-selling veterinary medicines in the world, with sales topping $1 billion annually