Ivermectin, an antiparasitic medication, has a multifaceted history. Its journey began with an unexpected discovery, leading to widespread use in global public health. The drug has since become a subject of discussion, reflecting its evolving applications and prominence.
A Serendipitous Discovery
Ivermectin’s origin began in 1970 with microbiologist Satoshi Ōmura of Kitasato University in Japan. He sought new antibiotic compounds from soil microorganisms. During this search, Ōmura isolated a strain of bacteria, Streptomyces avermitilis, from a soil sample collected in Japan.
Ōmura sent this promising bacterial strain to William C. Campbell, a parasitologist at the Merck Institute for Therapeutic Research in the United States. Campbell’s team at Merck cultivated the bacterium and discovered its fermentation products exhibited potent antiparasitic properties. These compounds were named avermectins, acknowledging their ability to clear mice of worms.
Of the avermectins identified, avermectin B1 proved most potent when administered orally. To enhance its pharmaceutical properties, Campbell’s group chemically modified avermectin B1, resulting in “ivermectin.” This derivative was found to be more effective and safer. Ivermectin was introduced into the animal health market in 1981, controlling parasites in livestock and pets.
A Nobel Prize-Winning Impact on Human Health
Ivermectin’s success in veterinary medicine paved the way for its transition to human use. William C. Campbell helped explore its potential for human applications, particularly against debilitating parasitic diseases. Following positive results in trials, ivermectin received approval for human use in 1987.
The drug’s impact has been on two neglected tropical diseases: Onchocerciasis, commonly known as River Blindness, and Lymphatic Filariasis, also called elephantiasis. River Blindness, transmitted by blackflies, causes itching, skin lesions, and permanent blindness. Lymphatic Filariasis, caused by parasitic worms, leads to painful swelling of limbs and disability. Ivermectin, by killing juvenile parasites (microfilariae), reduces disease transmission and progression.
In 1987, Merck committed to donating ivermectin (Mectizan) free of charge to control River Blindness. This Mectizan Donation Program expanded in 1998 to include Lymphatic Filariasis. This public-private partnership has reached hundreds of millions of people, delivering billions of treatments and significantly reducing the global burden of these diseases. The contributions of Satoshi Ōmura and William C. Campbell were recognized in 2015 when they were jointly awarded half of the Nobel Prize in Physiology or Medicine for their discoveries concerning a novel therapy against roundworm infections.
The Recent Chapter in Ivermectin’s Story
Ivermectin entered the global spotlight during the COVID-19 pandemic, marking a new chapter in its historical timeline. Initial laboratory studies suggested that ivermectin might possess antiviral properties, which garnered considerable public interest and discussion. This led to a surge in its off-label use by some individuals seeking to prevent or treat COVID-19.
The increased public attention also fueled widespread debate and media coverage surrounding the drug. Throughout this period, major regulatory and public health organizations worldwide issued statements regarding ivermectin’s use for COVID-19. The U.S. Food and Drug Administration (FDA) and the World Health Organization (WHO) did not authorize or recommend ivermectin for the prevention or treatment of COVID-19 outside of controlled clinical trials. These organizations stated that available clinical data did not demonstrate its effectiveness for this purpose. This stance positioned ivermectin as a subject of significant historical events during the pandemic, distinct from its established and approved uses for parasitic diseases.