<n0:ComplexDefinition xmlns:n0="http://ncicb.nci.nih.gov/xml/owl/EVS/ComplexProperties.xsd#"><n0:def-definition>A physician, scientist, or healthcare provider that investigates the mechanisms underlying the effects of drugs and chemicals on biological or living systems. This knowledge is employed to help design and evaluate drugs for the prevention and treatment of disease.</n0:def-definition><n0:def-source>NCI</n0:def-source></n0:ComplexDefinition>