The latest checkpoint inhibitor to be approved is AstraZeneca’s Imfinzi (durvalumab), a monoclonal antibody directed against PD-L1, which is expressed on cancer cells.
![](http://blogs.shu.edu/cancer/files/2017/06/Fig-1-PD-L1.jpg)
Figure 1. PD-1 / PD-L1 axis. http://www.cell.com/trends/molecular-medicine/references/S1471-4914(14)00183-X