关键词：癌症临床试验；癌症药物开发；临床前研究；多步癌变；医药
摘 要：The science underpinning cancer drug development has been changing rapidly in recent years because of a more mechanistic understanding of cancer. Today, hundreds of cancer therapeutics are in development, and many target specific molecules, genes, or pathways. To be most effective, preclinical studies indicate that many of these drug candidates need to be combined with other targeted agents, reflecting the complexity of multistep carcinogenesis. Clinical trials must receive regulatory approval from the Food and Drug Administration (FDA) for these innovative drug candidates before bringing them into clinical use. Not only are these trials expensive and lengthy, but they are extremely prone to failure because prediction of efficacy and toxicity in humans from findings in animal models has often proved unreliable, as has early testing in humans. Only a small percentage of drug candidates ultimately become useful therapies.