Design, synthesis, anti-mycobacterial activity, molecular docking and ADME analysis of spiroquinoxaline-1,2,4-oxadiazoles via [3 + 2] cycloaddition reaction under ultrasound irradiation

The development of anti-tuberculosis (anti-TB) drugs has become a challenging task in medicinal chemistry. This is because Mycobacterium tuberculosis (TB), the pathogen that causes tuberculosis, has an increasing number of drug-resistant strains, and existing medication therapies are not very effective. This resistance significantly demands new anti-TB drug profiles. Here, we present the design and synthesis of a number of hybrid compounds with previously known anti-mycobacterial moieties attached to quinoxaline, quinoline, tetrazole, and 1,2,4-oxadiazole scaffolds. A convenient ultrasound methodology was employed to attain spiroquinoxaline-1,2,4-oxadiazoles via [3 + 2] cycloaddition of quinoxaline Schiff bases and aryl nitrile oxides at room temperature. This approach avoids standard heating and column chromatography while producing high yields and shorter reaction times. The target compounds 3a-p were well-characterized, and their in vitro anti-mycobacterial activity (anti-TB) was evaluated. Among the screened compounds, 3i displayed promising activity against the Mycobacterium tuberculosis cell line H37Rv, with an MIC99 value of 0.78 µg/mL. However, three compounds (3f, 3h, and 3o) exhibited potent activity with MIC99 values of 6.25 µg/mL. To further understand the binding interactions, the synthesized compounds were docked against the tuberculosis protein 5OEQ using in silico molecular docking. Moreover, the most active compounds were additionally tested for their cytotoxicity against the RAW 264.7 cell line, and the cytotoxicity of compounds 3f, 3h, 3i, and 3o was 27.3, 28.9, 26.4, and 30.2 µg/mL, respectively. These results revealed that the compounds 3f, 3h, 3i, and 3o were less harmful to humans. Furthermore, the synthesized compounds were tested for ADME qualities, and the results suggest that this series is useful for producing innovative and potent anti-tubercular medicines in the future.

Spirooxadiazoline-oxindoles derived from imatinib show antimyeloproliferative potential in K562 cells

Imatinib mesylate was the first representative BCR-ABL1 tyrosine kinase inhibitor (TKI) class for the treatment of chronic myeloid leukemia. Despite the revolution promoted by TKIs in the treatment of this pathology, a resistance mechanism occurs against all BCR-ABL1 inhibitors, necessitating a constant search for new therapeutic options. To develop new antimyeloproliferative substances, we applied a medicinal chemistry tool known as molecular hybridization to design 25 new substances. These compounds were synthesized and biologically evaluated against K562 cells, which express BCR-ABL1, a constitutively active tyrosine kinase enzyme, as well as in WSS-1 cells (healthy cells). The new compounds are conjugated hybrids that contain phenylamino-pyrimidine-pyridine (PAPP) and an isatin backbone, which are the main pharmacophoric fragments of imatinib and sunitinib, respectively. A spiro-oxindole nucleus was used as a linker because it occurs in many compounds with antimyeloproliferative activity. Compounds 2a, 2b, 3c, 4c, and 4e showed promise, as they inhibited cell viability by between 45% and 61% at a concentration of 10 µM. The CC50 of the most active substances was determined to be within 0.8-9.8 µM.

Enantioselective formal [3+2]-cycloadditions to access spirooxindoles bearing four contiguous stereocenters through synergistic catalysis

An enantioselective ring-opening formal [3+2]-cycloaddition of spirovinylcyclopropyl oxindoles with enals via synergistic catalysis of palladium(0) and a chiral organocatalyst has been developed, affording spirooxindoles bearing four contiguous stereocenters in good yields with excellent enantioselectivities. The generality and utility of the protocol were also demonstrated through scale-up experiments and synthetic transformation of the resulting cycloadduct.

Potency and Selectivity Optimization of Tryptophanol-Derived Oxazoloisoindolinones: Novel p53 Activators in Human Colorectal Cancer

To search for novel p53 activators, four series of novel (S)- and (R)-tryptophanol-derived oxazoloisoindolinones were synthesized in a straightforward manner and their antiproliferative activity was evaluated in the human colorectal cancer HCT116 cell line. Structural optimization of the hit compound SLMP53-1 led to the identification of a (R)-tryptophanol-derived isoindolinone that was found to be six-fold more active, with increased selectivity for HCT116 cells with p53 and with low toxicity in normal cells. Binding studies with MDM2 showed that the antiproliferative activity of tryptophanol-derived isoindolinones does not involve inhibition of the main negative regulator of the p53 protein. Molecular docking simulations showed that although these molecules establish hydrophobic interactions with MDM2, they do not possess the required features to bind MDM2.

A [3 + 2] cycloaddition/C-arylation of isatin N,N′-cyclic azomethine imine 1,3-dipole with arynes

A [3 + 2] annulation/C-arylation reaction of 1,3-dipole 1 with arynes has been established for the synthesis of oxindole scaffolds.

Palladium-catalysed ring-opening [3 + 2]-annulation of spirovinylcyclopropyl oxindole to diastereoselectively access spirooxindoles

A novel palladium-catalysed ring-opening [3 + 2]-annulation of spirovinylcyclopropyl oxindole with α,β-unsaturated nitroalkenes is reported. A series of spirooxindole derivatives were synthesized in high yields and good to excellent diastereoselectivities. This developed protocol offers a new and efficient pathway for the assembly of spirooxindoles.

A Novel Small Molecule p53 Stabilizer for Brain Cell Differentiation

Brain tumor, as any type of cancer, is assumed to be sustained by a small subpopulation of stem-like cells with distinctive properties that allow them to survive conventional therapies and drive tumor recurrence. Thus, the identification of new molecules capable of controlling stemness properties may be key in developing effective therapeutic strategies for cancer by inducing stem-like cells differentiation. Spiropyrazoline oxindoles have previously been shown to induce apoptosis and cell cycle arrest, as well as upregulate p53 steady-state levels, while decreasing its main inhibitor MDM2 in the HCT116 human colorectal carcinoma cell line. In this study, we made modifications in this scaffold by including combinations of different substituents in the pyrazoline ring in order to obtain novel small molecules that could modulate p53 activity and act as differentiation inducer agents. The antiproliferative activity of the synthesized compounds was assessed using the isogenic pair of HCT116 cell lines differing in the presence or absence of the p53 gene. Among the tested spirooxindoles, spiropyrazoline oxindole 1a was selective against the cancer cell line expressing wild-type p53 and presented low cytotoxicity. This small molecule induced neural stem cell (NSC) differentiation through reduced SOX2 (marker of multipotency) and increased βIII-tubulin (marker of neural differentiation) which suggests a great potential as a non-toxic inducer of cell differentiation. More importantly, in glioma cancer cells (GL-261), compound 1a reduced stemness, by decreasing SOX2 protein levels, while also promoting chemotherapy sensitization. These results highlight the potential of p53 modulators for brain cell differentiation, with spirooxindole 1a representing a promising lead molecule for the development of new brain antitumor drugs.

Asymmetric synthesis of tetrahydroisoquinoline-fused spirooxindoles as Ras-GTP inhibitors that inhibit colon adenocarcinoma cell proliferation and invasion

We report the synthesis of a library of chiral THIQ-fused spirooxindoles. The most potent compound inhibits Ras-GTP, ultimately leading to mitochondrial apoptosis.

In vitro targeting of colon cancer cells using spiropyrazoline oxindoles

We report on the synthesis and biological evaluation of a library of twenty-three spiropyrazoline oxindoles. The antiproliferative activity of the chemical library was evaluated in HCT-116 p53^(+/+) human colon cancer cell line with eight derivatives displaying good activities (IC₅₀<15 μM). To characterize the molecular mechanisms involved in compound antitumoral activity, two spiropyrazoline oxindoles were selected for further studies. Both compounds were able to induce apoptosis and cell cycle arrest at G0/G1 phase and upregulated p53 steady-state levels, while decreasing its main inhibitor MDM2. Importantly, cytotoxic effects induced by spiropyrazolines oxindoles occurred in cancer cells without eliciting cell death in non-malignant CCD-18Co human colon fibroblasts. Additionally, we demonstrated that the combination of spiropyrazoline oxindole 2e with sub-toxic concentrations of the chemotherapeutic agent 5-fluorouracil (5-FU) exerted a synergistic inhibitory effect on HCT-116 colon cancer cell proliferation. Collectively, our results show the potential of spiropyrazoline oxindoles for development of novel anticancer agents.

HDAC inhibitors show differential epigenetic regulation and cell survival strategies on p53 mutant colon cancer cells

Besides inactivating tumour suppressor activity in cells, mutations in p53 confer significant oncogenic functions and promote metastasis and resistance to anticancer therapy. A variety of therapies involving genetic and epigenetic signalling events regulate tumorogenesis and progression in such cases. Pharmacological interventions with HDAC inhibitors have shown promise in therapy. This work explores the changes in efficacy of the four HDAC inhibitors SAHA, MS-275, valproic acid and sodium butyrate on a panel of colon cancer cell lines - HCT116 (p53 wt), HCT116 p53-/-, HT29 and SW480 (with mutations in p53). Clonogenic assays, gene profiling and epigenetic expression done on these cells point to p53 dependent differential activity of the 4 HDAC inhibitors which also elevate methylation levels in p53 mutant cell lines. In silico modelling establishes the alterations in interactions that lead to such differential activity of valproic acid, one of the inhibitors considered for the work. Molecular Dynamic simulations carried out on the valproic acid complex ensure stability of the complex. This work establishes a p53 dependent epigenetic signalling mechanism triggered by HDAC inhibition expanding the scope of HDAC inhibitors in adjuvant therapy for p53 mutant tumours.

Chemical Variations on the p53 Reactivation Theme

Among the tumor suppressor genes, p53 is one of the most studied. It is widely regarded as the "guardian of the genome", playing a major role in carcinogenesis. In fact, direct inactivation of the TP53 gene occurs in more than 50% of malignancies, and in tumors that retain wild-type p53 status, its function is usually inactivated by overexpression of negative regulators (e.g., MDM2 and MDMX). Hence, restoring p53 function in cancer cells represents a valuable anticancer approach. In this review, we will present an updated overview of the most relevant small molecules developed to restore p53 function in cancer cells through inhibition of the p53-MDMs interaction, or direct targeting of wild-type p53 or mutated p53. In addition, optimization approaches used for the development of small molecules that have entered clinical trials will be presented.