Design and synthesis of novel 7-aminosubstituted pyrido[2,3-b]pyrazines exhibiting anti-breast cancer activity

Discovery of New 1,4,6-Trisubstituted-1H-pyrazolo[3,4-b]pyridines with Anti-Tumor Efficacy in Mouse Model of Breast Cancer

Purine analogues are important therapeutic tools due to their affinity to enzymes or receptors that are involved in critical biological processes. In this study, new 1,4,6-trisubstituted pyrazolo[3,4-b]pyridines were designed and synthesized, and their cytotoxic potential was been studied. The new derivatives were prepared through suitable arylhydrazines, and upon successive conversion first to aminopyrazoles, they were converted then to 1,6-disubstituted pyrazolo[3,4-b]pyridine-4-ones; this served as the starting point for the synthesis of the target compounds. The cytotoxic activity of the derivatives was evaluated against several human and murine cancer cell lines. Substantial structure activity relationships (SARs) could be extracted, mainly concerning the 4-alkylaminoethyl ethers, which showed potent in vitro antiproliferative activity in the low μM level (0.75–4.15 μΜ) without affecting the proliferation of normal cells. The most potent analogues underwent in vivo evaluation and were found to inhibit tumor growth in vivo in an orthotopic breast cancer mouse model. The novel compounds exhibited no systemic toxicity; they affected only the implanted tumors and did not interfere with the immune system of the animals. Our results revealed a very potent novel compound which could be an ideal lead for the discovery of promising anti-tumor agents, and could also be further explored for combination treatments with immunotherapeutic drugs.

Scaffold Repurposing Reveals New Nanomolar Phosphodiesterase Type 5 (PDE5) Inhibitors Based on Pyridopyrazinone Scaffold: Investigation of In Vitro and In Silico Properties

Inhibition of PDE5 results in elevation of cGMP leading to vascular relaxation and reduction in the systemic blood pressure. Therefore, PDE5 inhibitors are used as antihypertensive and antianginal agents in addition to their major use as male erectile dysfunction treatments. Previously, we developed a novel series of 34 pyridopyrazinone derivatives as anticancer agents (series A–H). Herein, a multi-step in silico approach was preliminary conducted to evaluate the predicted PDE5 inhibitory activity, followed by an in vitro biological evaluation over the enzymatic level and a detailed SAR study. The designed 2D-QSAR model which was carried out to predict the IC₅₀ of the tested compounds revealed series B, D, E and G with nanomolar range of IC₅₀ values (6.00–81.56 nM). A further docking simulation model was performed to investigate the binding modes within the active site of PDE5. Interestingly, most of the tested compounds showed almost the same binding modes of that of reported PDE5 inhibitors. To validate the in silico results, an in vitro enzymatic assay over PDE5 enzyme was performed for a number of the promising candidates with different substitutions. Both series E and G exhibited a potent inhibitory activity (IC₅₀ = 18.13–41.41 nM). Compound 11b (series G, oxadiazole-based derivatives with terminal 4-NO₂ substituted phenyl ring and rigid linker) was the most potent analogue with IC₅₀ value of 18.13 nM. Structure–activity relationship (SAR) data attained for various substitutions were rationalized. Furthermore, a molecular dynamic simulation gave insights into the inhibitory activity of the most active compound (11b). Accordingly, this report presents a successful scaffold repurposing approach that reveals compound 11b as a highly potent nanomolar PDE5 inhibitor worthy of further investigation.

Thioethers: An Overview

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Spreading rapidly in recent years, cancer has become one of the causes of the highest mor-tality rates after cardiovascular diseases. The reason for cancer development is still not clearly under-stood despite enormous research activities in this area. Scientists are now working on the biology of cancer, especially on the root cause of cancer development. The aim is to treat the cancer disease and thus cure the patients. The continuing efforts for the development of novel molecules as potential anti-cancer agents are essential for this purpose. The main aim of this review was to present a survey on the medicinal chemistry of thioethers and provide practical data on their cytotoxicities against various cancer cell lines. The research articles published between 2001-2020 were consulted to pre-pare this review article; however, patent literature has not been included. The thioether-containing heterocyclic compounds may emerge as a new class of potent and effective anti-cancer agents in the future.

Design and Synthesis of New Substituted Pyrazolopyridines with Potent Antiproliferative Activity

Background:

Purine isosteres are often endowed with interesting pharmacological properties, due to their involvement in cellular processes replacing the natural purines. Among these compounds, pyrazolopyridines are under active investigation for potential anticancer properties.

Objective:

Based on previously discovered substituted pyrazolopyridines with promising antiproliferative activity, we designed and synthesized new, suitably substituted analogues aiming to investigate their potential activity and contribute to SAR studies of this class of bioactive compounds.

Methods:

The new compounds were synthesized using suitably substituted 2-amino-4-picolines, which upon ring-closure provided substituted pyrazolo[3,4-c] pyridine-5-carbonitriles that served as key intermediates for the preparation of the target 3,5,7 trisubstituted derivatives. The antiproliferative activity of 31 new target derivatives was evaluated against three cancer cell lines (MIA PaCa-2, PC-3 and SCOV3), whereas cell-cycle perturbations of exponentially growing PC-3 cells, using three selected derivatives were also performed.

Results:

Eight compounds displayed IC50 values in the low μM range, allowing the extraction of interesting SAR’s. Two of the most potent compounds against all cell lines share a common pattern, by accumulating cells at the G0/G1 phase. From this project, a new carboxamidine-substituted hit has emerged.

Conclusion:

Among the new compounds, those possessing the 3-phenylpyrazolo[3,4-c]pyridine scaffold, proved to be worth investigating and the majority of them showed strong cytotoxic activity against all cell lines, with IC50 values ranging from 0.87-4.3 µM. A carboxamidine analogue that resulted from the synthetic procedure, proved to be highly active against the cancer cells and could be considered as a useful lead for further optimization.

Development of Promising Thiopyrimidine-Based Anti-cancer and Antimicrobial Agents: Synthesis and QSAR Analysis

Objective & Methodology:

New hybrids of thiopyrimidine-five/six heterocyclic rings were synthesized and in vitro evaluated for their antiproliferative activity against three human cancer cell lines, namely HCT116 (human colorectal carcinoma), PC-3 (human prostate adenocarcinoma) and HepG2 (human liver carcinoma) cell lines. The most potency was elicited by the target candidates against the viability of HCT116 cell lines. It was higher than that obtained by the positive control 5-Fluorouracil (IC50 range; 0.11-0.49 μM, IC50, 5-FU; 1.10 μM).

Results:

Cell cycle analysis and apoptosis activation revealed that compound 20 induced G2/M phase arrest and apoptosis in HCT116 cells. In addition, compound 20 activates the caspases-9 and -3, a process which might mediate the apoptosis of HCT116 cells.

Conclusion:

Furthermore, there is a good agreement between the observed pIC50 and the predicted pIC50 values, in addition, the low RMSD and standard error values indicate the accuracy of the model. Antimicrobial evaluation revealed that some of these compounds exhibited significant activities against the tested pathogenic bacteria and fungi, wherein compounds 7a, 14, 15a, 21a, produced the most potent and broad spectrum antibacterial and antifungal potency that was equivalent to that revealed by Vibramycin and Ketoconazole (MIC; 125 μg/mL). Moreover, compounds 15a, 21c, investigated dual potent antimicrobial and anticancer activity.

Targeting of the breast cancer microenvironment with a potent and linkable oxindole based antiangiogenic small molecule

The clinical efficacy of antiangiogenic small molecules (e.g., sunitinib) in breast carcinoma has largely failed with substantial off-target toxicity. We rationally designed and evaluated preclinically a novel sunitinib analogue, SAP, with favourable pharmacological properties and the ability to be readily conjugated to a targeting peptide or antibody for active tumour targeting.

SAP was evaluated in silico and in vitro in order to verify target engagement (e.g., VEGFR2). Pharmacokinetic and biodistribution parameters were determined in mice using LC-MS/MS. SAP efficacy was tested in two breast cancer xenograft and two syngeneic animal models and pharmacodynamic evaluation was accomplished using phosphokinase assays and immunohistochemistry. Cardiac and blood toxicity of SAP were also monitored.

SAP retained the antiangiogenic and cytotoxic properties of the parental molecule with an increased blood exposure and tumor accumulation compared to sunitinib. SAP proved efficacious in all animal models. Tumors from SAP treated animals had significantly decreased Ki-67 and CD31 markers and reduced levels of phosphorylated AKT, ERK and S6 compared to vehicle treated animals. In mice dosed with SAP there was negligible hematotoxicity, while cardiac function measurements showed a reduction in the percentage left ventricular fractional shortening compared to vehicle treated animals.

In conclusion, SAP is a novel rationally designed conjugatable small antiangiogenic molecule, efficacious in preclinical models of breast cancer.

Current research on anti-breast cancer synthetic compounds

Breast cancer (BC) is the most common cancer for females and its incidence tends to increase year by year.