They bind sometimes better than the natural ligand does, but they don't create the right biological reaction.

结合的比天然配体和受体的的结合更紧密,但不能产生相同的生物效应

耶鲁公开课 - 生物医学工程探索课程节选

Much of the work that pharmaceutical companies do in terms of searching for drugs is searching for new ligands that activate receptors and create biological responses inside cells.

很多制药公司新药筛选工作的主要内容,就是寻找能够激活受体的,新型配体,并在细胞内部产生某种生物学效应

耶鲁公开课 - 生物医学工程探索课程节选