Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKI) have been used as the first‐line treatment of non‐small cell lung cancers (NSCLC) harboring EGFR‐activating mutations, but acquired resistance is ubiquitous and needs to be solved urgently. Here, we introduce an effective approach for overcoming resistance to the EGFR‐TKI, AZD9291, in NSCLC cells using SHR‐A1403, a novel c‐mesenchymal‐epithelial transition factor (c‐Met)‐targeting antibody‐drug conjugate (ADC) consisting of an anti‐c‐Met monoclonal antibody (c‐Met mAb) conjugated to a microtubule inhibitor. Resistant cells were established by exposing HCC827 to increasing concentrations of EGFR‐TKI. c‐Met was found to be overexpressed in most resistant cells. AZD9291 resistance was partially restored by combination of AZD9291 and crizotinib only in resistant cells overexpressing phospho‐c‐Met, which synergistically inhibited c‐Met‐mediated phosphorylation of the downstream targets ERK1/2 and AKT. In resistant cells overexpressing c‐Met, neither crizotinib nor c‐Met mAb was able to overcome AZD9291 resistance. In contrast, SHR‐A1403 strongly inhibited proliferation of AZD9291‐resistant HCC827 overexpressing c‐Met, regardless of the levels of c‐Met phosphorylation. SHR‐A1403 bound to resistant cells overexpressing c‐Met was internalized into cells and released associated microtubule inhibitor, resulting in cell‐killing activity that was dependent on c‐Met expression levels only, irrespective of the involvement of c‐Met or EGFR signaling in AZD9291 resistance. Consistent with its activity in vitro, SHR‐A1403 significantly inhibited the growth of AZD9291‐resistant HCC827 tumors and caused tumor regression in vivo. Thus, our findings show that SHR‐A1403 efficiently overcomes AZD9291 resistance in cells overexpressing c‐Met, and further indicate that c‐Met expression level is a biomarker predictive of SHR‐A1403 efficacy.

PD-1/PD-L1 checkpoint blockade has demonstrated great success in cancer immunotherapy. Small-molecule PD-L1 inhibitors also attract significant research interests but remain challenging in the efficacy and safety. Carbohydrate moiety and carbohydrate-binding proteins (lectins) play important roles in immune modulation including antigen recognition and presenting. Herein, we reported a novel strategy to strengthen the immunotherapeutic effect of small-molecule PD-L1 inhibitors by introducing sugar motifs, which may utilize the carbohydrate-mediated immune enhancement for cancer treatment. The data revealed that glycoside compounds containing mannose or N-acetylglucosamine exhibited the best results in IFN-γ secretion. Moreover, compared to the nonglycosylated compounds, glycosides C3 and C15 demonstrated significant lower cytotoxicity and effective in vivo antitumor potency in the CT26 and melanoma B16-F10 tumor models with good tolerance. Notably, tumor-infiltrating lymphocyte (TIL) analysis validated increased CD3+, CD4+, CD8+, and granzyme B+ T cells after glycoside treatments. This work presents a new concept to improve the immunotherapy.