In medicine, a chemical compound that shows promise as a treatment for a disease and may lead to the development of a new drug. Thousands of compounds are tested in the laboratory to find a lead (“leading”) compound that may act on specific genes or proteins involved in a disease. Once a lead compound has been found, the chemical structure is used as a starting point to make a drug that has the most benefits and the least harms. Finding a lead compound is the first step in making a new drug to treat a disease.