[1] He is best known for his claims to have found a cure for cancer from the substance used by the Shuar ethnic group of Ecuador in their traditional practice of headhunting.
[2] However, mainstream scientific institutions have never verified his claims about the substance's supposed curative properties, and it has not been developed into any contemporary medical treatment.
The U.S. Embassy in Ecuador reportedly looked into why Ferguson, as an American citizen, was supporting sending Carlos Egas Llaguno, an Ecuadorian communist, to the United States for him to receive police training.
Even before his time as a missionary, Ferguson had had a longstanding desire to work exploring remote regions of the world for medical plants, a practice that would develop into the fields of ethnobotany and ethnomedicine.
[1] Plaza had gotten him and his wife Ruth a number of medical positions in Ecuador, which gave him government support in his attempts to find the Shuar.
[1] Eventually the Shuar elders apparently gave Tangamasha permission to teach Ferguson how to make the substance and how to use it to shrink a monkey's head.
According to him, the substance was highly successful in curing patients of tumors,[citation needed] although there are no reliable sources validating that claim.
Later tests at the University of Cuenca using the substance from Tangamasha were reportedly successful initially, but the tumors began to return when a less effective batch of the solution was used.
Ferguson subsequently returned to Ecuador, to the town of Sucúa near the traditional territory of the Shuar people to carry out further research into how his substance worked.
[4][page needed] After that, he moved back to California and began working on further testing of the substance at an organization called the World Life Research Institute, run by a scientist named Bruce Halstead.
[1][6] During this time, Ferguson was located in Guayaquil, Ecuador, where at least one patient from the United States showed up hoping to be cured of cancer.
Subsequently, he was contacted by Merck and the National Cancer Institute, but after the failure of those tests he also lost much of his Ecuadorian support after the administration of Galo Plaza left government.
In 1992, Ferguson and composer Phillip Lambro sued Sean Connery, Tom Schulman, and Creative Artists Agency for copyright infringement concerning the recently released film Medicine Man.
[9] Ferguson and Lambro eventually lost this case because Tom Schulman was able to demonstrate that the story of Medicine Man was instead based on his longstanding friendship with the conservationist Daniel Janzen.
[1] Mazinter reportedly contacted a corporation called ILEX that was trying to develop cancer drugs and discussed a deal, but the two parties were never able to reach one; the exact circumstances are still disputed.