TLR8 and cancer: Furthermore, a series of pyrido[3,2-d] pyrimidine-based toll-like receptor 7/8 dual agonists have been designed and synthesized, which exhibit potent and near-equivalent agonistic activities toward TLR7 and TLR8 with great potential as single agents or in combination with PD-1/PD-L1 blockade for cancer immunotherapy [44].