The NCI In Vitro Anticancer Drug Discovery Screen

Since 1955, the US National Cancer Institute (NCI) has provided screening support to cancer researchers worldwide. Until 1985, the NCI screening program and the selection of compounds for further preclinical and clinical development under NCI auspices had relied predominantly on the in vivo L1210 and P388 murine leukemias and certain other transplantable tumor models (1). From 1975-1985, the in vivo P388 mouse leukemia model was used almost exclusively as the initial or primary screen. With few exceptions, agents that showed minimal or no activity in the P388 system were not selected by the NCI for further evaluation in other tumor models or alternative screens. Most of the available clinical anticancer agents are active in the P388 system; however, most were discovered prior to 1975 or by observations initially in test systems other than the NCI-operated P388 primary screen.