PDCD1 and neoplasm: However, it has been recently reported that in the process of inhibiting the PD-1/PD-L1 axis, the expression of other immune checkpoints, such as TIM-3, is increased, which may be related to adaptive resistance.81 Combined checkpoint inhibitors (CPIs) have been successfully used to improve tumour immune response and survival, and an increasing number of checkpoint inhibitors are targeting many costimulatory and cosuppressive interactions.