Design, synthesis and biological evaluation of novel heptamethine cyanine dye-erlotinib conjugates as antitumor agents

Epidermal growth factor receptor tyrosine kinase (EGFR-TK) has been proved as a target for the treatment of non-small cell lung cancer (NSCLC) with specific gene mutations. However, EGFR-TK inhibitors (EGFR-TKIs) need to enter cancer cells and then competitively interact with the active site of tyrosine kinase receptors to suppress the downstream signaling pathway to inhibit tumor proliferation. In this study, in order to improve the tumor cell targeting ability of EGFR-TKI, EGFR-TKI erlotinib was conjugated with the cancer cell-targeting heptamethine cyanine dyes to form seventeen novel erlotinib-dye conjugates. The efficiency of tumor targeting properties of conjugates against cancer cell growth and EGFR-TK inhibition was evaluated in vitro. The result revealed that most erlotinib-dye conjugates exhibited stronger inhibitory effect on A549, H460, H1299 and MDA-MB-231 cell lines than the parent drug erlotinib. Meanwhile, representative compounds exhibited weak cytotoxicity on human normal mammary epithelial MCF-10A cells. Moreover, the conjugate CE17 also showed ~14-fold higher EGFR-TK inhibition activity (IC50 = 0.124 μM) than erlotinib (IC50 = 5.182 μM) in A549 cell line. Finally, molecular docking analysis verified that the erlotinib moiety of compound CE17 could form hydrogen bond with Met-769 and occupy active cavity of EGFR-TK. Therefore, we believed the integration strategy between heptamethine cyanine dyes and EGFR-TKI will contribute to enhancing the therapeutic effect of EGFR-TKI for NSCLC treatment.