The phrase "molecular target-based drug discovery" usually implies an in vitro biochemical assay or battery of assays. One portion of the U.S. National Cancer Institute's drug discovery program, to the contrary, examines molecular targets for cancer therapy in a cell-based format. That approach has a number of significant limitations, but it has produced databases of significant utility on the activities and structures of tested compounds, as well as on molecular characteristics of the cell types used for testing.