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Eleven new proteolysis targeting chimeras (PROTACs) based on promiscuous kinase inhibitor Sunitinib were designed, synthesized, and assessed for their anticancer activity against four human cancer cell lines A498, K562, HL‐60 and MCF‐7. Two known compounds were also prepared and used as control samples. The CCK‐8 assay results showed that a new PROTAC with a 1,4‐diaminobutane linker (PROTAC 10) exhibited significant antiproliferative activity against A498 (IC50=0.11 ± 0.01 μM) and K562 (IC50=0.59 ± 0.21 μM) cell lines. Western blot analysis showed that in addition to the previously reported G1 to S phase transition 1 (GSPT1), PROTAC 10 also reduced the protein level of fms‐like tyrosine kinase 3 (FLT3) and proto‐oncogene tyrosine protein kinase Src (SRC) in A498 cells. Moreover, PROTAC 10 regulated the protein levels of GSPT1 and SRC in a dose‐ and time‐dependent manner and induced degradation of GSPT1 in a ubiquitin‐proteasome‐dependent manner in K562 cells. [ABSTRACT FROM AUTHOR]

[Display omitted] Proteolysis Targeting Chimeras (PROTACs) based on multi-target inhibitors have been reported several times recently. The advantages of PROTACs technology and the synergistic mechanism of multi-target drugs endow this class of protein degraders with special research significance. Herein, twelve new PROTACs based on Sunitinib and VHL-ligand were synthesized and evaluated for their in vitro anticancer activities. Among them, PROTACs 5 (IC 50 = 2.9 ± 1.5 μM) exhibited the most significant antiproliferative activity against HL-60 cells. Western blot results showed that PROTAC 5 reduced the protein levels of FLT-3 and c-KIT in HL-60 cells, and induced the degradation of FLT-3 via the ubiquitin–proteasome system. Moreover, PROTACs 5 and 6 reduced the protein levels of FLT-3 in K562 cells. These results suggest that PROTAC 5 has the potential for further research, especially in combination with small molecule kinase inhibitors to study multidrug resistance of tyrosine kinase inhibitors in cancer treatment. [ABSTRACT FROM AUTHOR]