Novel series of phthalazine derivatives 6-11 were designed, synthesized, and evaluated for their anticancer activity against two human tumor cell lines, HCT-116 human colon adenocarcinoma and MCF-7 breast cancer cells, targeting the VEGFR-2 enzyme. Compounds 7a,b and 8b,c showed the highest anticancer activities against both HCT116 human colon adenocarcinoma cells with IC of 6.04 ± 0.30, 13.22 ± 0.22, 18 ± 0.20, and 35 ± 0.45 μM, respectively, and MCF-7 breast cancer cells with IC of 8.8 ± 0.45, 17.9 ± 0.50, 25.2 ± 0.55, and 44.3 ± 0.49 μM, respectively, in comparison to sorafenib as reference drug with IC of 5.47 ± 0.3 and 7.26 ± 0.3 μM, respectively. Eleven compounds in this series were further evaluated for their inhibitory activity against VEGFR-2, where compounds 7a, 7b, 8c, and 8b also showed the highest VEGFR-2 inhibition with IC of 0.11 ± 0.01, 0.31 ± 0.03, 0.72 ± 0.08, and 0.91 ± 0.08 μM, respectively, in comparison to sorafenib as reference ligand with IC of 0.1 ± 0.02. Furthermore, molecular docking studies were performed for all synthesized compounds to predict their binding pattern and affinity towards the VEGFR-2 active site, in order to rationalize their anticancer activity in a qualitative way.

In the designed compounds, a new linker was inserted in the form of fragments with verified VEGFR‐2 inhibitory potential, including an α,β‐unsaturated ketonic fragment, pyrazole, and pyrimidine. Also, new distal hydrophobic moieties were attached to these linkers that are expected to increase the hydrophobic interaction with VEGFR‐2 and, consequently, the affinity. These structural optimizations have led us to identify the novel dihydropyrazole derivative 6e as a promising hit molecule. All the new derivatives were evaluated to assess their anticancer activity against three human cancer cell lines, including HepG2, HCT‐116, and MCF‐7. The results of the in vitro anticancer evaluation study revealed the moderate to excellent cytotoxicity of 6c, 6e, 6g, and 7b, with IC50 values in the low micromolar range. The inhibitory activity of VEGFR‐2 was investigated for 16 of the designed compounds. The enzyme assay results of the new compounds were compared with those of sorafenib as a reference VEGFR‐2 inhibitor. The obtained results demonstrated that our derivatives are potent VEGFR‐2 inhibitors. The most potent derivatives 6c, 6e, 6g, and 7b showed IC50 values in the range of 0.11–0.22 µM. Molecular docking and pharmacokinetic studies were also conducted to rationalize the VEGFR‐2 inhibitory activity and to evaluate the ability of the most potent derivatives to be developed as good drug candidates.

In accordance with the significant impetus of the discovery of potent vascular endothelial growth factor receptor 2 (VEGFR‐2) inhibitors, herein, we report the design, synthesis, and anticancer evaluation of 12 new N‐substituted‐4‐phenylphthalazin‐1‐amine derivatives against HepG2, HCT‐116, and MCF‐7 cells as VEGFR‐2 inhibitors. The results of the cytotoxicity investigation indicated that HCT‐116 and MCF‐7 were the most sensitive cell lines to the influence of the newly synthesized derivatives. In particular, compound 7a was found to be the most potent derivative among all the tested compounds against the three cancer cell lines, HepG2, HCT116, and MCF‐7, with IC50 = 13.67 ± 1.2, 5.48 ± 0.4, and 7.34 ± 0.6 µM, respectively, which is nearly equipotent to that of sorafenib (IC50 = 9.18 ± 0.6, 5.47 ± 0.3, and 7.26 ± 0.3 µM, respectively). All synthesized derivatives, 4a,b−8a−c, were evaluated for their inhibitory activities against VEGFR‐2. The tested compounds displayed high to low inhibitory activity, with IC50 values ranging from 0.14 ± 0.02 to 9.54 ± 0.85 µM. Among them, compound 7a was found to be the most potent derivative that inhibited VEGFR‐2 at an IC50 value of 0.14 ± 0.02 µM, which is nearly 72% of that of the sorafenib IC50 value (0.10 ± 0.02 µM). Compounds 7b, 8c, 8b, and 8a exhibited very good activity with IC50 values of 0.18 ± 0.02, 0.21 ± 0.03, 0.24 ± 0.02, and 0.35 ± 0.04 µM, respectively. Molecular modeling studies were carried out for all compounds against the VEGFR‐2 active site. The data obtained from biological testing highly correlated with that obtained from molecular modeling studies. However, these modifications led to new phthalazine derivatives with higher VEGFR‐2 inhibitory activities than vatalanib and which are nearly equipotent to sorafenib.

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.

Newly designed thiazolidine-2,4-diones 3–7a–c were synthesized, and their anticancer activities were screened against three cancer lines. They showed potent activities against HepG2 compared to the other HCT116 and MCF-7 tumor cell lines. Compounds 7c and 6c were detected as highly effective derivatives against MCF-7 (IC50 = 7.78 and 8.15 µM), HCT116 (IC50 = 5.77 and 7.11 µM) and HepG2 (IC50 = 8.82 and 8.99 µM). The highly effective derivatives 6a–c and 7a–c were tested against VERO normal cell lines. All derivatives were evaluated for their VEGFR-2 inhibitory actions and demonstrated high to low activities, with IC50 values varying from 0.08 to 0.93 µM. Moreover, derivatives 5a–c, 6a–c and 7a–c were assessed to verify their in vitro binding affinities to PPARγ and insulin-secreting activities. Finally, docking studies were performed to explore their affinities and binding modes toward both VEGFR-2 and PPARγ receptors.