Structure-Activity Relationship of Indole-Tethered Pyrimidine Derivatives that Concurrently Inhibit Epidermal Growth Factor Receptor and Other Angiokinases

Design, Synthesis, Antiproliferative Screening, and In Silico Studies of Some Pyridinyl‐Pyrimidine Candidates

Using pyrimidinethione, a new series of pyridinyl‐pyrimidine candidates was prepared by reacting with diverse carbon‐centered electrophiles like hydrazonoyl chloride, N‐arylchloroacetamide, ethyl chloroacetate, and enaminone derivatives. Some heteroannulated compounds, such as triazolopyrimidine and thiazolopyrimidine derivatives were obtained. The mass fragmentation pathways were investigated by the electron impact mass spectrometry (EI‐MS), and the molecular ion peaks (M+.) were recorded at different intensities. The in vitro antiproliferative efficacy of the prepared compounds against MCF7 and HCT116 cancer cell lines showed the highest potency of pyrimidinethione 2, triazolopyrimidine 4, and thiazolopyrimidine 10. Also, in silico studies were performed to recognize these findings. A molecular docking simulation towards the EGFR enzyme showed the best docking score of thiazolopyrimidine 10 through H‐bonding and hydrophobic interactions in comparison to the interactions of co‐crystallized ligand and doxorubicin. With DFT calculations, compound 10 exhibited the lowest energy gap and the highest softness. Among ADME simulation, compounds 7, 8, 9, and 11 exhibited desirable lead‐likeness. It is hoped that this work may affect advancing new effective antiproliferative agents.

Some Thiazolopyrimidine Derivatives: Synthesis, DFT, Cytotoxicity, and Pharmacokinetics Modeling Study

A pyrimidinethione candidate carrying pyrazole and thiophene scaffolds was produced by a Biginelli cyclocondensation reaction of a pyrazolecarbaldehyde with pentan-2,4-dione and thiourea. To create some heteroannulated thiazolopyrimidines, the pyrimidinethione was subjected to cyclocondensation reactions with ethyl chloroacetate, 1,2-dibromoethane, chloroacetonitrile, and oxalyl chloride. A DFT simulation was performed for a frontier-orbital analysis to determine the molecular geometry. Among the products, 6-acetyl-7-methyl-5-[1-phen­yl-3-(2-thienyl)-1H-pyrazol-4-yl]-5H-[1,3]thiazolo[3,2-a]pyrimidine-2,3-dione displayed the highest softness and the lowest energy gap in the DFT calculations. Moreover, it had the highest electrophilicity index, suggesting possible biological impacts. The compounds obtained were evaluated against cell lines of breast adenocarcinoma (MCF7) and hepatocellular carcinoma (HepG2) as antiproliferative agents. A simulation of the molecular docking of our compounds with the epidermal growth factor receptor demonstrated the rationality of our design and identified the binding mode. A model pharmacokinetics analysis showed that the products have the expected and desirable drug-like and bioavailability properties.

Drug-like properties of tyrosine kinase inhibitors in ophthalmology: Formulation and topical availability

Tyrosine kinase inhibitors (TKIs) can inhibit edema and neovascularization, such as in age-related macular degeneration and diabetic retinopathy. However, their topical administration in ophthalmology is limited by their toxicity and poor aqueous solubility. There are multiple types of TKIs, and each TKI has an affinity to more than one type of receptor. Studies have shown that ocular toxicity can be addressed by selecting TKIs that have a high affinity for specific vascular endothelial growth factor receptors (VEGFRs) but a low affinity for epidermal growth factor receptors (EGFRs). Drugs permeate from the aqueous tear fluid into the eye via passive diffusion. Thus, a sustained high concentration of the dissolved drug in the aqueous tear fluid is essential for a successful delivery to posterior tissues such as the retina. Unfortunately, the aqueous solubility of the TKIs that have the most favorable VEGFR/EGFR affinity ratio, that is, axitinib and cabozantinib, is well below 1 µg/mL, making their topical delivery very challenging. This is a review of the drug-like properties of TKIs that are currently being evaluated or have been evaluated as ophthalmic drugs. These properties include their solubilization, cyclodextrin complexation, and ability to permeate from the aqueous tear fluid to the posterior eye segment.

New antiproliferative 3-substituted oxindoles inhibiting EGFR/VEGFR-2 and tubulin polymerization

New 3-substituted oxindole derivatives were designed and synthesized as antiproliferative agents. The antiproliferative activity of compounds 6a-j was evaluated against 60 NCI cell lines. Among these tested compounds, compounds 6f and 6g showed remarkable antiproliferative activity, specifically against leukemia and breast cancer cell lines. Compound 6f was the most promising antiproliferative agent against MCF-7 (human breast cancer) with an IC50 value of 14.77 µM compared to 5-fluorouracil (5FU) (IC50 = 2.02 µM). Notably, compound 6f hampered receptor tyrosine EGFR fundamentally with an IC50 value of 1.38 µM, compared to the reference sunitinib with an IC50 value of 0.08 µM. Moreover, compound 6f afforded anti-tubulin polymerization activity with an IC50 value of 7.99 µM as an outstanding observable activity compared with the reference combretastatin A4 with an IC50 value of 2.64 µM. In silico molecular-docking results of compound 6f in the ATP-binding site of EGFR agreed with the in vitro results. Besides, the investigation of the physicochemical properties of compound 6f via the egg-boiled method clarified good lipophilicity, GIT absorption, and blood-brain barrier penetration properties.

Recent Development in the Search for Epidermal Growth Factor Receptor (EGFR) Inhibitors based on the Indole Pharmacophore

The signal transduction and cell proliferation are regulated by the epidermal growth factor receptor. The proliferation of tumor cells, apoptosis, invasion, and angiogenesis is inhibited by the epidermal growth factor receptor. Thus, breast cancer, non-small cell lung cancer, cervical cancer, glioma, and bladder cancer can be treated by targeting the epidermal growth factor receptor. Although third-generation epidermal growth factor receptor inhibitors are potent drugs, patients exhibit drug resistance after treatment. Thus, the search for new drugs is being continued. Among the different potent epidermal growth factor receptor inhibitors, we have reviewed the indole-based inhibitors. We have discussed the structure-activity relationship of the compounds with the active sites of the epidermal growth factor receptor receptors, their synthesis, and molecular docking studies.

Design, Synthesis, and Biological Evaluation of Indole-2-carboxamides as Potential Multi-Target Antiproliferative Agents

A small set of indole-based derivatives, IV and Va-I, was designed and synthesized. Compounds Va-i demonstrated promising antiproliferative activity, with GI₅₀ values ranging from 26 nM to 86 nM compared to erlotinib's 33 nM. The most potent antiproliferative derivatives-Va, Ve, Vf, Vg, and Vh-were tested for EGFR inhibitory activity. Compound Va demonstrated the highest inhibitory activity against EGFR with an IC₅₀ value of 71 ± 06 nM, which is higher than the reference erlotinib (IC₅₀ = 80 ± 05 nM). Compounds Va, Ve, Vf, Vg, and Vh were further tested for BRAF^V600E inhibitory activity. The tested compounds inhibited BRAF^V600E with IC₅₀ values ranging from 77 nM to 107 nM compared to erlotinib's IC₅₀ value of 60 nM. The inhibitory activity of compounds Va, Ve, Vf, Vg, and Vh against VEGFR-2 was also determined. Finally, in silico docking experiments attempted to investigate the binding mode of compounds within the active sites of EGFR, BRAF^V600E, and VEGFR-2.

Recent development of multi-target VEGFR-2 inhibitors for the cancer therapy

Vascular epidermal growth factor receptor-2 (VEGFR-2), as an important tyrosine transmembrane protein, plays an important role in regulating endothelial cell proliferation and migration, regulating angiogenesis and other biological functions. VEGFR-2 is aberrantly expressed in many malignant tumors, and it is also related to the occurrence, development, and growth of tumors and drug resistance. Currently, there are nine VEGFR-2 targeted inhibitors approved by US.FDA for clinical use as anticancer drugs. Due to the limited clinical efficacy and potential toxicity of VEGFR inhibitors, it is necessary to develop new strategies to improve the clinical efficacy of VEGFR inhibitors. The development of multitarget therapy, especially dual-target therapy, has become a hot research field of cancer therapy, which may provide an effective strategy with higher therapeutic efficacy, pharmacokinetic advantages and low toxicity. Many groups have reported that the therapeutic effects could be improved by simultaneously inhibiting VEGFR-2 and other targets, such as EGFR, c-Met, BRAF, HDAC, etc. Therefore, VEGFR-2 inhibitors with multi-targeting capabilities have been considered to be promising and effective anticancer agents for cancer therapy. In this work, we reviewed the structure and biological functions of VEGFR-2, and summarized the drug discovery strategies, and inhibitory activities of VEGFR-2 inhibitors with multi-targeting capabilities reported in recent years. This work might provide the reference for the development of VEGFR-2 inhibitors with multi-targeting capabilities as novel anticancer agents.

Design, Synthesis, and Antiproliferative Activity of New 5-Chloro-indole-2-carboxylate and Pyrrolo[3,4-b]indol-3-one Derivatives as Potent Inhibitors of EGFRT790M/BRAFV600E Pathways

Mutant EGFR/BRAF pathways are thought to be crucial targets for the development of anticancer drugs since they are over-activated in several malignancies. We present here the development of a novel series of 5-chloro-indole-2-carboxylate 3a-e, 4a-c and pyrrolo[3,4-b]indol-3-ones 5a-c derivatives as potent inhibitors of mutant EGFR/BRAF pathways with antiproliferative activity. The cell viability assay results of 3a-e, 4a-c, and 5a-c revealed that none of the compounds tested were cytotoxic, and that the majority of those tested at 50 µM had cell viability levels greater than 87%. Compounds 3a-e, 4a-c, and 5a-c had significant antiproliferative activity with GI50 values ranging from 29 nM to 78 nM, with 3a-e outperforming 4a-c and 5a-c in their inhibitory actions against the tested cancer cell lines. Compounds 3a-e were tested for EGFR inhibition, with IC50 values ranging from 68 nM to 89 nM. The most potent derivative was found to be the m-piperidinyl derivative 3e (R = m-piperidin-1-yl), with an IC50 value of 68 nM, which was 1.2-fold more potent than erlotinib (IC50 = 80 nM). Interestingly, all the tested compounds 3a-e had higher anti-BRAFV600E activity than the reference erlotinib but were less potent than vemurafenib, with compound 3e having the most potent activity. Moreover, compounds 3b and 3e showed an 8-fold selectivity index toward EGFRT790M protein over wild-type. Additionally, molecular docking of 3a and 3b against BRAFV600E and EGFRT790M enzymes revealed high binding affinity and active site interactions compared to the co-crystalized ligands. The pharmacokinetics properties (ADME) of 3a-e revealed safety and good pharmacokinetic profile.

Design, synthesis, and biological evaluation of novel EGFR inhibitors containing 5-chloro-3-hydroxymethyl-indole-2-carboxamide scaffold with apoptotic antiproliferative activity

New EGFR inhibitor series of fifteen 5-chloro-3-hydroxymethyl-indole-2-carboxamide derivatives has been designed, synthesized, and tested for antiproliferative activity against a panel of cancer cell lines. The results showed that p-substituted phenethyl derivatives 10, 11, 13, 15 and 17-19 showed superior antiproliferative activity compared to their m-substituted counterparts 12, 14, 16 and 20. Compounds 15, 16, 19 and 20 displayed promising EGFR inhibitory activity as well as an increase in caspase 3 levels. Compounds 15 and 19 increased caspase-8 and 9 levels, as well as inducing Bax and decreasing Bcl-2 protein levels. Compound 19 demonstrated cell cycle arrest at pre-G1 and G2/M phases. The results of the docking study into the active site of EGFR revealed strong fitting of the new compounds with higher binding affinities compared to erlotinib.

Novel potent substituted 4-amino-2-thiopyrimidines as dual VEGFR-2 and BRAF kinase inhibitors

In the present study, we report the discovery of a novel class of substituted 4-amino-2-thiopyrimidines as antiangiogenic and antiproliferative agents. Structural hybridization between 4-substituted aminopyrimidines (VEGFR-2 inhibitors) and 2-thioxopyrimidines (BRAF inhibitors) was carried out to afford substituted 4-amino-2-thiopyrimidines as type II dual VEGFR-2/BRAF inhibitors. Our design strategy was tailored such that the 4-amino-2-thiopyrimidine scaffold is to be accommodated in the central gate area of the inactive DFG-out conformation of both enzymes. On one side, the hydrophobic substituent on the 4-amino group would occupy the hydrophobic back pocket and on the other side the substituent on the sulfide moiety should extend to fit in the hinge region (front pocket). Molecular docking simulations confirmed the ability of the designed compounds to accomplish the key interactions in VEGFR-2 and BRAF active sites. Most of the synthesized substituted 4-amino-2-thiopyrimidines demonstrated potent VEGFR-2 inhibitory activity at submicromolar concentrations. Compounds 8a, 8d, 9c and 9e showed IC₅₀ = 0.17, 0.12, 0.17 and 0.19 μM, respectively against VEGFR-2 in comparison to sorafenib (I) IC₅₀ = 0.10 μM and regorafenib (II) IC₅₀ = 0.005 μM. While compounds 9c, 9d and 10a showed IC₅₀ = 0.15, 0.22 and 0.11 μM, respectively against BRAF-WT. At 10 μM concentration 9c revealed promising in vitro broad-spectrum antiproliferative activity against cancer cell lines with growth inhibition percent ranging from 10 to 90%. Moreover, compounds 7b, 8d, 9a, 9b, 9c and 9d showed potent activity against MCF7 cell line (IC₅₀ = 17.18, 17.20, 19.98, 19.61, 13.02 and 16.54 μM, respectively). On the other hand, compounds 9c, 9d and 10d were found to be the most potent compounds against T-47D cell line (IC₅₀ = 2.18, 8.09 and 4.36 μM, respectively). Studying the effect of the most potent compounds on VEGFR-2 level in MCF7 cell line revealed that 9c and 9d showed inhibition percent of 84 and 80%, respectively, in comparison to sorafenib (I) (% inhibition = 90%).