Johnson’s early success at Eli Lilly led him onto a cancer project in the late 1960’s and early 1970’s. This project was at the time of the Nixon’s War on Cancer. His goal was to develop drugs to fight cancer.
Johnson first developed a screen. A screen is a laboratory model of the tumor you are trying to destroy. If you have an accurate laboratory model, then you can test many different drugs to see if any have an effect on the model. Once shown to have an effect on the model, you can test whether the drugs have any effect in real human studies. Johnson had laboratory models for several different tumors, including lymphocytic leukemia. Lymphocytic leukemia is a cancer of the blood that usually strikes children. With his screen, he could perform 5,000 tests per year to try to find a drug that could reduce the size of tumors.
Johnson knew many of the chemists at Eli Lilly. The chemists were the ones who came up with different potential drugs. One man, Gordon Svoboda, specialized in drugs derived from plants. Svoboda gave Johnson a batch of chemicals to test that were derived from the periwinkle plant, a ubiquitous plant that grows around the world. Johnson found that one compound derived from the leaves of the periwinkle plant had activity against his model of leukemia. This compound, called vincristine, was incorporated into a combination drug that had spectacular results when given to children with acute lymphocytic leukemia, a particular type of blood cancer. Similar work had been going on independently in Canada by Charles Beer and Robert Noble.
Vincristine, like insulin, was too complex to synthesize at the time. It was instead manufactured by purifying it from the leaves of the periwinkle plant, technically known as Catharanthus roseus. Much like insulin, which relied on the constant supply of pig or beef pancreases, vincristine relied upon a constant supply of leaves of the periwinkle plant. Lots of leaves were needed, since it took about one ton of dried leaves to produce one ounce of vincristine. Irving Johonson Science 1992 p 860 Eli Lilly ended up growing periwinkle on a ranch in Texas to satisfy their supply.