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Development of small molecule PD-1/PD-L1 inhibitors as a novel immunotherapy strategy exhibits great promise. Herein, a novel series of quinazoline derivatives were designed, synthesized and their inhibitory activity against the PD-1/PD-L1 interaction was evaluated through a homogenous time-resolved fluorescence (HTRF) assay. Among them, the compound 39 exhibited the most potent inhibitory activity with an IC50 value of 1.57 nM. Furthermore, the cellular level assays revealed that 39 could inhibit the PD-1/PD-L1 interaction and restore T-cell function, and showed low toxicity on the PBMCs. In addition, the structure-activity relationships (SARs) of the novel quinazoline derivatives were explored and the binding mode of 39 with dimeric PD-L1 was analyzed by molecular docking. This work demonstrates that incorporation of pyrimidine group between the 2 and 3-positions of the biphenyl structure is an effective strategy for designing novel and more potent small molecule PD-1/PD-L1 inhibitors, and 39 can be regarded as a promising lead compound for further investigation.

A hybrid pharmacophore approach was used to design and synthesize a series of coumarin derivatives bearing 2-methylbiphenyl moiety, which were evaluated for their in vitro anticancer activities against four cancer cell lines(MCF-7, A549, H460 and HT29) and PD-1/PD-L1 inhibitory activities. Moreover, several compounds with excellent anticancer activities were selected to evaluate the cytotoxicities against one normal cell line(HEK-293). The most promising compound 11o showed the best anticancer activities against the four tested cancer cell lines with the IC50 values of 6.45, 8.65, 6,57 and 8.13 μmol/L, respectively, and displayed weak cytotoxicity on the normal cell(HEK-293). Furthermore, screening of PD-1/PD-L1inhibitory activity revealed that compound 11o could effectively inhibit the binding of PD-1/PD-L1, and the binding interactions of compound 11o with PD-L1 protein were explored by molecular docking. All above evidences showed that compound 11o might be worthy of further study as a valuable leading compound for the treatment of cancer.

Three series of compounds were designed, synthesized and evaluated for their in vitro anticancer activity against a procaspase-3 over-expression cancer cell line (U937) and a procaspase-3 no-expression cancer cell line (MCF-7) to rule out off-target effects. Biological evaluation led to the identification of a series of benzothiazole derivatives bearing a pyridine-semicarbazone moiety, 8j and 8k, with promising anticancer activity and remarkable selectivity. Further mechanism studies revealed that compounds 8j and 8k could induce apoptosis of cancer cells by activating procaspase-3 to caspase-3, and compound 8k exhibited the strongest procaspase-3 activation activity. Structure–activity relationships (SARs) revealed that the presence of benzothiazole and an N,N,O-donor set is crucial for the anticancer activity and selectivity, and reducing the electron density of the N,N,O-donor set results in a dramatic decline in the anticancer activity and selectivity. Furthermore, toxicity evaluation (zebrafish) in vivo and metabolic stability studies (human, rat and mouse liver microsomes) were performed to provide reliable guidance for further PK/PD studies in vivo.