Banting and Macleod won a Nobel Prize in 1923 for their research, which they subsequently shared with co-discoverers Charles Best and James Collip. Insulin, "the most important drug" in the company's history, did "more than any other" to make Lilly "one of the major pharmaceutical manufacturers in the world." Eli Lilly enjoyed effective monopoly on the sale of insulin in the U.S. for almost two years, until the first of the new American licensees, Frederick Stearns & Co., entered the market in June 1924.