Design, Synthesis, In Vitro Anti-cancer Activity, ADMET Profile and Molecular Docking of Novel Triazolo[3,4-a]phthalazine Derivatives Targeting VEGFR-2 Enzyme.

Abstract

Extensive studies were reported in the synthesis of several phthalazine derivatives as promising anticancer agents as potent VEGFR-2 inhibitors. Vatalanib (PTK787) was the first anilinophthalazine published derivative as a potent inhibitor of VEGFR. The discovery of vatalanib as a clinical candidate led to the design and synthesis of different anilinophthalazine derivatives as potent inhibitors for VEGFR-2. The objective of present research work is the synthesis of new agents with the same essential pharmacophoric features of the reported and clinically used VEGFR-2 inhibitors (e.g vatalanib and sorafenib). The main core of our molecular design rationale comprised bioisosteric modification strategies of VEGFR-2 inhibitors at four different positions. A correlation between structure and biological activity of our designed phthalazines was established using molecular docking and VEGFR-2 kinase assay. In view of their expected anticancer activity, novel triazolo[3,4-a]phthalazine derivatives 5-6a-o and 3-substituted-bis([1,2,4]triazolo)[3,4-a:4',3'-c]phthalazines 9a-b were designed, synthesized and evaluated for their anti-proliferative activity against two human tumor cell lines HCT-116 human colon adenocarcinoma and MCF-7 breast cancer. It was found that, compound 6o the most potent derivative against both HCT116 and MCF-7 cancer cell lines. Compounds 6o, 6m, 6d and 9b showed the highest anticancer activities against HCT116 human colon adenocarcinoma with IC50 of 7±0.06, 13±0.11, 15±0.14 and 23±0.22 µM respectively while compounds 6o, 6d, 6a and 6n showed the highest anticancer activities against MCF-7 breast cancer with IC50 of 16.98±0.15, 18.2±0.17, 57.54±0.53 and 66.45±0.67 µM respectively. Sorafenib as a highly potent VEGFR-2 inhibitor was used as a reference drug with IC50 of 5.47±0.3 and 7.26±0.3 µM respectively. Nine compounds were further evaluated for their VEGFR-2 inhibitory activity. Compounds 6o, 6m, 6d and 9b emerged as the most active counterparts against VEGFR-2 with IC50 values of 0.1±0.01, 0.15±0.02, 0.28±0.03 and 0.38±0.04 µM, respectively comparable to that of sorafenib (IC50 = 0.1±0.02) µM. Furthermore, molecular docking studies were carried out for all synthesized compounds to investigate their binding pattern and predict their binding affinities towards VEGFR-2 active site. In silico ADMET studies were calculated for the tested compounds. Most of our designed compounds exhibited good ADMET profile. The obtained results showed that, the most active compounds could be useful as a template for future design, optimization, adaptation and investigation to produce more potent and selective VEGFR-2 inhibitors with higher anticancer analogs.