Ynamide Click chemistry in development of triazole VEGFR2 TK modulators

Structure novelty, chemical stability and synthetic feasibility attracted us to design 1,2,3-triazole compounds as potential inhibitors of VEGFR2 tyrosine kinase. Novel triazoles T1–T7 were proposed by oxazole (AAZ from PDB: 1Y6A)/1,2,3-triazole isosteric replacement, molecular modelling and docking. In order to enable synthesis of T1–T7 we developed a methodology for preparation of ynamide 22. Compound 22 was used for all Click chemistry reactions leading to triazoles T1–T3 and T6–T7. Among the obtained products, T1, T3 and T7 specifically bind VEGFR2 TK and modulate its activity by concentration dependent manner. Moreover predicted binding poses of T1–T7 in VEGFR2 TK were similar to the one known for the oxazole inhibitor AAZ (PDB: 1Y6A). Unfortunately the VEGFR2 inhibition by triazoles e.g. T3 and T7 is lower than that determined for their oxazole bioisosters T3-ox and AAZ, resp. Different electronic properties of 1,2,3-triazole/oxazole heterocyclic rings were proposed to be the main reason for the diminished affinity of T1–T3, T6 and T7 to an oxazole AAZ inhibitor binding site in VEGFR2 TK (PDB: 1Y6A or 1Y6B). Moreover T1–T3 and T6 were screened on cytotoxic activity against two human hepatocellular carcinoma cell lines. Selective cytotoxic activity of T2 against aggressive Mahlavu cells has been discovered indicating possible affinity of T2 to Mahlavu constitutionally active PI3K/Akt pathway.