Synthesis and biological evaluation as antiangiogenic agents of ureas derived from 3′-aminocombretastatin A-4

Recent advances and future directions on small molecule VEGFR inhibitors in oncological conditions

"A journey of mixed emotions" is a quote that best describes the progress chart of vascular endothelial growth factor receptor (VEGFR) inhibitors as cancer therapeutics in the last decade. Exhilarated with the Food and Drug Administration (FDA) approvals of numerous VEGFR inhibitors coupled with the annoyance of encountering the complications associated with their use, drug discovery enthusiasts are on their toes with an unswerving determination to enhance the rate of translation of VEGFR inhibitors from preclinical to clinical stage. The recently crafted armory of VEGFR inhibitors is a testament to their growing dominance over other antiangiogenic therapies for cancer treatment. This review perspicuously underscores the earnest attempts of the researchers to extract the antiproliferative potential of VEGFR inhibitors through the design of mechanistically diverse structural assemblages. Moreover, this review encompasses sections on structural/molecular properties and physiological functions of VEGFR, FDA-approved VEGFR inhibitors, and hurdles restricting the activity range/clinical applicability of VEGFR targeting antitumor agents. In addition, tactics to overcome the limitations of VEGFR inhibitors are discussed. A clear-cut viewpoint transmitted through this compilation can provide practical directions to push the cart of VEGFR inhibitors to advanced-stage clinical investigations in diverse malignancies.

Tetrazole derivatives as potent immunomodulatory agents in tumor microenvironment

Twenty-seven compounds bearing a tetrazole ring as a central unit have been designed, synthetized and biologically evaluated. Studies have been performed in order to compare the effect of tetrazole derivatives bearing amine electron-donor or nitro electron-acceptor groups. The antiproliferative activity has been determined in monoculture studies on tumor cell lines HT-29, A-549, MCF-7 and on non-tumor cell line HEK-293 as well as in co-culture studies (HT-29/THP-1). All the compounds have been studied as PD-L1 (Programmed Death Ligand 1), VEGFR-2 (Vascular Endothelial Growth Factor 2), CD-47 (Cluster of Differentiation 47) and c-Myc inhibitors. The effect on TNF-α secretion has also been determined. Bromoderivatives 23, 24 and chloroderivatives 26, 27 have demonstrated an apoptotic effect on HT-29 cancer cells. Compounds bearing an amine group have shown very promising effects as TME immunomodulatory agents.

Proapoptotic effects of halogenated bis-phenylthiourea derivatives in cancer cells

New halogenated thiourea derivatives were synthesized via the reaction of substituted phenylisothiocyanates with aromatic amines. Their cytotoxic activity was examined in in vitro studies against solid tumors (SW480, SW620, PC3), a hematological malignance (K-562), and normal keratinocytes (HaCaT). Most of the compounds were more effective against SW480 (1a, 3a, 3b, 5j), K-562 (2b, 3a, 4a), or PC3 (5d) cells than cisplatin, with favorable selectivity. Their anticancer mechanisms were studied by Annexin V-fluorescein-5-isothiocyanate apoptosis, caspase-3/caspase-7 assessment, cell cycle analysis, interleukin-6 (IL-6) release inhibition, and reactive oxygen species (ROS) generation assay. Thioureas 1a, 2b, 3a, and 4a were the most potent activators of early apoptosis in K-562 cells, and substances 1a, 3b, 5j triggered late-apoptosis or necrosis in SW480 cells. This proapoptotic effect was proved by the significant increase of caspase-3/caspase-7 activation. Cell cycle analysis revealed that derivatives 1a, 3a, 5j increased the number of SW480 and K-562 cells in the sub-G1 and/or G0/G1 phases, and one evoked cycle arrest at the G2 phase. The most potent thioureas inhibited IL-6 cytokine secretion from PC3 cells and both colon cancer cell lines. Apoptosis-inducing compounds also increased ROS production in all tumor cell cultures, which may enhance their anticancer properties.

Unveiling the Potential of BenzylethyleneAryl-Urea Scaffolds for the Design of New Onco Immunomodulating Agents

This work focuses on the development of thirteen benzylethylenearyl ureas and one carbamate. After the synthesis and purification of the compounds, we studied their antiproliferative action on cell lines, such as HEK-293, and cancer ones, such as HT-29, MCF-7 or A-549, on the immune Jurkat T-cells and endothelial cells HMEC-1. Compounds C.1, C.3, C.12 and C.14 were selected for further biological studies to establish their potential as immunomodulating agents. Some of the derivatives exhibited significant inhibitory effects on both targets: PD-L1 and VEGFR-2 in the HT-29 cell line, showing that urea C.12 is active against both targets. Some compounds could inhibit more than 50% of cancer cell proliferation compared to non-treated ones when assessed in co-cultures using HT-29 and THP-1 cells. In addition, they significantly reduced CD11b expression, which is a promising target for immune modulation in anticancer immunotherapies.

Exploring BenzylethoxyAryl Urea Scaffolds for Multitarget Immunomodulation Therapies

Thirteen benzylethoxyaryl ureas have been synthesized and biologically evaluated as multitarget inhibitors of VEGFR-2 and PD-L1 proteins to overcome resistance phenomena offered by cancer. The antiproliferative activity of these molecules on several tumor cell lines (HT-29 and A549), on the endothelial cell line HMEC-1, on immune cells (Jurkat T) and on the non-tumor cell line HEK-293 has been determined. Selective indexes (SI) have been also determined and compounds bearing p-substituted phenyl urea unit together with a diaryl carbamate exhibited high SI values. Further studies on these selected compounds to determine their potential as small molecule immune potentiators (SMIPs) and as antitumor agents have been performed. From these studies, we have concluded that the designed ureas have good tumor antiangiogenic properties, exhibit good inhibition of CD11b expression, and regulate pathways involved in CD8 T-cell activity. These properties suggest that these compounds could be potentially useful in the development of new cancer immune treatments.

Quinazolin-4(3H)-one based agents bearing thiadiazole-urea: Synthesis and evaluation of anti-proliferative and antiangiogenic activity

A series of quinazolin-4(3H)-one based agents containing thiadiazole-urea were designed, synthesized, and biologically evaluated. The proliferation rate of PC3 cells was moderately reduced by compound 9f (IC₅₀ = 17.7 μM)which was comparable with sorafenib (IC₅₀ = 17.3 μM). There was also a significant reduction in the number of HUVEC cells, when they were exposed to compound 9y (IC₅₀ = 6.1 μM). To test the potential of compounds in inducing apoptosis, Annexin V-FITC/propidium iodide double staining assay was used. After the treatment of HUVEC cells with 9f, they underwent apoptotic effects. A substantial effort was dedicated to gathering comprehensive data across CAM assay. These data showed that 9f moderately inhibits the growth of corresponding blood vessels. Finally, the outcomes of Western blotting proposed a mechanism of action, by which the phosphorylation of VEGFR-2 is inhibited by compounds 9f and 9y.

Synthesis and biological evaluation of novel pyrazolo[3,4-b]pyridines as cis-restricted combretastatin A-4 analogues

Twenty-six novel pyrazolo[3,4-b]pyridine-bridged analogues of combretastatin A-4 possessing 3,4,5-trimethoxylphenyl groups, were synthesized and evaluated for their antiproliferative and tubulin polymerization inhibitory activities. Preliminary biological evaluation demonstrated that some of the target compounds displayed significant antiproliferative effectagainst four different cell lines including MCF-7, MDA-MB-231, HeLa and Kyse150. The most active analogue 6n was found to induce HeLa cells arrest in the G2/M phase in a dose-dependent manner. Molecular modeling studies indicated that derivative 6n most likely occupies the colchicine site of tubulin. The initial results suggest that the 3,4,5-trimethoxyphenyl substituted pyrazolo[3,4-b]pyridine could serve as a promising scaffold for development of potent tubulin inhibitors as anticancer agents.

Synthesis of Combretastatin A-4 and 3'-Aminocombretastatin A-4 derivatives with Aminoacid Containing Pendants and Study of Their Interaction with Tubulin and as Downregulators of the VEGF, hTERT and c-Myc Gene Expression

Natural product combretastatin A-4 (CA-4) and its nitrogenated analogue 3′-aminocombretastatin A-4 (AmCA-4) have shown promising antitumor activities. In this study, a range of CA-4 and AmCA-4 derivatives containing amino acid pendants have been synthesized in order to compare their biological actions with those of their parent compounds. Thus, inhibition of cell proliferation on tumor cell lines HT-29, MCF-7 and A-549, as well as on the nontumor cell line HEK-273; in vitro tubulin polymerization; mitotic cell arrest; action on the microtubule cell network and inhibition of VEGF, hTERT, and c-Myc genes have been evaluated. Some AmCA-4 derivatives bearing L-amino acids exhibited inhibition of cell proliferation at low nanomolar levels exceeding the values shown by AmCA-4. Furthermore, while CA-4 and AmCA-4 derivatives do not show significant effects on the in vitro tubulin polymerization and cell cycle arrest, some selected CA-4 and AmCA-4 derivatives are able to cause total depolymerization of the microtubule network on A-549 cells. The best results were obtained in the inhibition of gene expression, particularly on the VEGF gene, in which some AmCA-4 derivatives greatly exceeded the inhibition values achieved by the parent compound.