Letters in Drug Design & Discovery - Volume 19, Issue 6, 2022

Saponins represent a category of diverse, natural glycoside molecules that belong to the triterpenoid or the steroid class. They vary in terms of their solubility and permeability characteristics and are classifiable based on the biopharmaceutics classification system. They have drug delivery potential as surfactants that can solubilize cholesterol in the plasma membrane of tumorigenic cells. Glioblastoma is an important malignancy that can aggressively afflict the brain of humans with a poor prognosis. Glioblastoma Stem Cells (GSCs) are an important subset of cancer cells and major determinants for drug resistance and tumour relapse. These cells are quiescent and have been known to survive current therapeutic strategies. Certain saponins have shown potential to eliminate glioblastoma cells in a variety of model systems and hence provide a sound scientific basis for their development as a “stand-alone” drug or as part of a drug combination (from the existing arsenal of drugs) developed for the treatment of glioblastoma. However, due to their reactogenicity towards the immune system and hemolytic potential, selective delivery to the tumorigenic site is essential. Hence, nano-formulations (liposome/emulsion-based delivery systems/nano-structured lipid and calix[n]arenes-based carriers) and variants that are resistant to saponin may serve as delivery tools that can be functionalized to improve the selectivity. It is necessary to develop/ validate/refine in vitro higher order models that replicate the features of the glioma microenvironment (BBB/BTB). Reproducible validation of the model as well as the drug/delivery system will help in the development of formulations that can augment cell death in this recalcitrant brain tumour.

Background: As an alternative to the anticoagulant’s strategy using direct or indirect anti-Xa drugs, considering other targets upstream in the coagulation cascade such as anti-Factor VIIa could represent an effective and safer strategy in coagulation and pathological angiogenesis. Objective: The objective of the study was to assess a high technology methodology composed of virtual screening, anticoagulant, and anti-angiogenesis assays to identify potent small-molecule FVIIa inhibitors. Methods: Chemical databanks were screened to select molecules bearing functional groups that could fit into the active site of FVIIa, which were then tested. Ligands assigned with the lowest scores were retained and then biologically assessed. Results: From the 500 molecules considered, 8 chemical structures revealed to be effective compounds in vitro and to inhibit angiogenesis in the chick chorioallantoic membrane (CAM) model. Conclusion: New potent small-molecule FVIIa inhibitors have been identified; further biochemical and chemical developments would be investigated directly from the selected scaffolds.

Background: The 1,2,3-triazole hybrids and conjugates containing natural or related compounds motif demonstrate diverse biological activities, including anticancer, antimicrobial, antitubercular, antiviral, antidiabetic, antimalarial, anti-leishmanial, and neuroprotective ones. Among a wide range of pharmacological applications, considerable attention is paid to the study of anticancer activity. In anticancer research, combining 1,2,3-triazole with other motifs, previously demonstrating antiproliferative activity into one hybrid molecule, is a common strategy for the creation of new bioactive molecules. The CuAAC (copper-catalyzed azide–alkyne cycloaddition) is a very convenient reaction for the rapid construction of drug-like 1,2,3-triazoles at room temperature in a short time. Methods: Based on the pharmacophore strategy, a virtual combinatorial library of benzo[c]chromen-6- one linked 1,2,3-triazole derivatives was designed and lead-likeness and molecular analysis were performed. Selected compounds were synthesized via CuAAC click reaction and the chemical structures of all new 1,2,3-triazole hybrids were proved by ¹H, ¹³C NMR, MS and elemental analyses. Their anticancer activity in the human cancer cell lines was evaluated using the MTT assay. Results: A virtual in silico screening of novel benzo[c]chromen-6-one linked 1,2,3-triazole was carried out in order to discover potential antitumor agents. The synthesis of promising compounds was carried out via СuAAC reaction, and their antineoplastic action was studied on human tumor cells of HL-60, HCT116, HCT116 p53-/-, Skov3, U251, MDA231 lines. Their cytotoxic effect towards pseudo-normal human cells of HaCaT line was also evaluated. 2-((1H-1,2,3-triazol-4-yl)methoxy)-6H-benzo[c]chromen- 6-one (4c) with pyridin-3-yl substituent demonstrated the highest antiproliferative action in vitro (IC50 79.5 μM) towards human leukemia cells of HL-60 line, while all tested compounds at >100 μM concentration were tolerant for non-tumor human keratinocytes of HaCaT line. Conclusion: A novel benzo[c]chromen-6-one linked 1,2,3-triazoles exhibiting promising in vitro anticancer activity and low toxicity were designed. This study suggests new scaffolds for the development of anti-cancer drugs, which could be easily further optimized via the convenient synthetic procedure.

Background: Phenylurenyl chalcone structures have the potential to act as a scaffold in anticancer drug discovery. Methods: N-Phenethyl-N'-{4-[(2E)-3-phenylprop-2-enoyl]phenyl}urea, 4/3-[(2E)-3-substitutedphenylprop-2- enoyl]phenyl}-N-phenylurea,4/3-[(2E)-3-substitutedphenyl. prop-2-enoyl]phenyl}-N-methylphenyl urea and {4/3-[(2E)-3-substitutedphenylprop-2-enoyl]phenyl}-Nethylphenyl urea derivatives(1-35) were prepared and evaluated for their anticancer and antimicrobial activity against A-549 Hep-3B, HT-29, CF-7, PC-3, K-562 NIH-3T3 and Huh-7 cell lines and against Staphylococcus aureus (ATCC 6538), Pseudomonas aeruginosa (ATCC 9027), Escherichia coli (ATCC 8739) and Candida albicans (ATCC 10231), respectively. Results: While compounds 2, 26, 29, and 34 showed moderate cytotoxic activity on cell line Huh 7, compounds 14 (IC50: 6.42 μM), 16 (IC50: 5.64 μM), 19 (IC50: 6.95 μM) and 34 (IC50: 6.87 μM) showed good cytotoxic activity on Huh-7 cell line close to Sorafenib (IC50: 4.29 μM) (as reference). MIC values of compounds 4 and 22 against E. coli were 25 μg/ml, compounds 3, 14 and 29 against P. aeruginosa 25 μg/ml, and compounds 11 and 33 against S. aureus 25 μg/ml. On the other hand, the minimum inhibitory concentration of all tested compounds against C. albicans was 25 μg/ml. Conclusion: N-Phenethyl-N'-{4-[(2E)-3-phenylprop-2-enoyl]phenyl}urea may be a new candidate to be developed as an anticancer compound.

Aim: The study aims to enhance the permeability of pyridostigmine bromide by developing a self-double emulsifying drug delivery system (SDEDDS) and enteric-coated spheroids. Background: Pyridostigmine bromide is a reversible anticholinesterase used to treat Myasthenia Gravis, reverse neuromuscular blockade, and prevent nerve gas (i.e., soman) poisoning. It is readily soluble in water, but its poor and irregular intestinal absorption is responsible for its poor oral bioavailability (7.6±2.4%). Many approaches have been made to increase the bioavailability of this drug, but no significant improvement has been achieved to date. Presently pyridostigmine tablets are given orally, and a treatment schedule of multiple doses every day (3–6 times per day) is recommended for adult patients, while sustained-release pyridostigmine (Timespan®) tablets can be taken once or twice daily. An increase in permeability of pyridostigmine bromide may also result in reduced dosage frequency. Objective: In the present work, it is proposed to develop a self-double emulsifying drug delivery system (SDEDDS) of pyridostigmine bromide which will increase its intestinal permeability and hence its oral bioavailability. Methods: For the preparation of PB-SDEDDS, the primary water in oil emulsion was mixed with the optimized concentration of Tween 80 using a magnetic stirrer. PB-SDEDDS were converted into spheroids and were then characterized. Results: The pseudo ternary phase diagram was constructed, showing a double emulsion region. The viscosity of PB-SDEDDS at the different shear rates was found to be 125 mPas. The optimized PBSDEDDS formulation formed a bright white emulsion within 2 minutes, having droplet size around 20-25 μm. In vitro uptake studies of PB-SDEDDS on Caco2 cells demonstrated the increase in Papp value from (4.38±0.27) ×10-4 cm/s to (9.488±0.182) ×10-4 cm/s (2.166 folds) that was attributed to the PB-SDEDDS formulation. In vitro cytotoxicity studies on Caco2 cells revealed that the blank SDEDDS showed almost no toxicity after incubation for 2 hours at various dilutions tested. Among all formulations, F3 was optimized for the concentration of adsorbent and binder at a concentration of 10% each. SEM showed that the spheroids were spherical, and 73.92% of spheroids were in between 0.595-0.841 mm of size. The optimized formulation had 70.29% spheroids retained on sieve no. 30. The angle of repose showed good flow properties with 25.20 and stability with friability of 0.52 %. The disintegration time of the developed formulation was 3.30 minutes, and drug content was found to be 97.83%. The release studies showed that PB-SDEDDS improved the release significantly compared to the market formulation. Conclusion: The solid PB-SDEDDS resulted in favorable physical properties and did not affect its drug content and in vitro drug release profile. The self-double emulsifying drug delivery system of pyridostigmine bromide can be explored as a suitable alternative to its solid oral dosage form.

Background: The role of retinoic acid receptor-related orphan receptors in cancer development has raised the interest to develop multi-functional agents. Objective: The main purpose of this work was in silico design and synthesis of potential anticancer candidates with antioxidant effect. Methods: The compounds were designed based on their docking studies with respect to the RORγt receptor. Using the Gewald protocol, a series of new tetrahydrobenzothiophene derivatives was synthesized. The physicochemical and spectroanalytical findings, including FTIR, ¹H-NMR, ¹³C-NMR, and mass spectroscopic techniques, verified the molecular structures of the synthesized derivatives. The anticancer and antioxidant potential of the synthesized compounds was assessed in vitro. The compounds were tested by the National Cancer Institute, USA for anticancer action towards different cell lines representing nine cancerous conditions. The antioxidant activity of compounds was assessed in vitro using the DPPH free radical scavenging method. Results: Docking analysis on RORγt receptors revealed that the test compounds have anticancer potential. Within the binding pocket of the chosen PDB ID (6q7a), RCA3 and RCA5 showed good docking scores in molecular docking studies, validating their capability of being used in rational drug design as lead compounds. Compounds showed diversified ratios of anticancer activity. RCA5 and RCA7 showed excellent antioxidant activity in reference to ascorbic acid with IC50 values of 18.71μg/mL and 20.88μg/mL. Conclusion: Cytotoxicity results very well complemented the docking scores. Compounds RCA3 and RCA5 displayed higher anticancer activity in the subpanels of leukemia, breast cancer, and lung cancer. Compounds RCA5 and RCA7 displayed potent antioxidant action comparable to ascorbic acid, while other compounds presented mild to good antioxidant behavior.

Background: Computational methods in the ‘omics’ era have proved to be a boon in the drug discovery field. Bioinformatics and cheminformatics databases and tools complement the successful discovery of promising lead compounds in the treatment of several disease conditions, including neurodegenerative diseases, such as Alzheimer’s Disease (AD). However, commercially available drugs in the market to alleviate the disease progression in AD patients are sparse. The current research aims to apply an in-silico approach involving multi-therapeutic agents against multi-therapeutic targets through docking studies to explore potential lead compounds for AD clinical trials. Method: In the proposed research, virtual screening was performed on four US FDA-approved control drugs (donepezil (DON), galantamine (GAL), rivastigmine (RIV), and tacrine (TAC)) in order to be used for mild-moderate-severe stages of AD treatment. The panel of compounds identified through virtual screening was assessed for chemical absorption, distribution, metabolism, excretion, and toxicity (ADMET) and Pharmacokinetics (PK). The compound with good ADMET and PK score was investigated further with molecular docking against the four therapeutic targets involved in AD. Ligands showing the highest binding affinity against cholinesterase inhibitors (AChE, BuChE), receptor antagonists (NMDA), and β-amyloid peptide (Aβ), were computed. Result: The compounds quinazolidinone analogue, 2b, isoquinoline-pyridine, 1, benzylmorphine and coelenteramide, were found to be the lead candidates having least side effects and better efficacy. Conclusion: The predicted lead candidates are suitable for further investigation in the drug discovery pipeline.

Background: In an endeavor to ascertain high-affinity TSPO ligands with minimal single nucleotide polymorphism (SNP), six hybrid molecules have been identified as new leads for future inflammation PET imaging. Objective: Genesis for chemical design was encouraged from structural families of well-known ligands FEBMP and PBR28/ DAA1106 that have demonstrated remarkable TSPO binding characteristics. Methods: All proposed hybrid ligands 1-6 are subjected to molecular docking and simulation studies with wild and mutant protein to study their interactions, binding, consistency of active conformations and are correlated with well-established TSPO ligands. Results: Each hybrid ligand demonstrate better docking score > -11.00 kcal/mol with TSPO with respect to gold standard PK11195, i.e., -11.00 kcal/mol for 4UC3 and -12.94 kcal/mol for 4UC1. On comparison with FEBMP and GE-180 ({-12.57, -7.24 kcal/mol} for 4UC3 and {-14.10, -11.32 kcal/mol} for 4UC1), ligand 3 demonstrates maximum docking energy (> -15.50 kcal/mol) with minimum SNP (0.26 kcal/mol). Discussion: Presence of strong hydrogen bond Arg148-3.27Å (4UC1) and Trp50-2.43Å, Asp28- 2.57Å (4UC3) apart from short-range interactions, including π–π interactions with the aromatic residues, such as (Trp39, Phe46, Trp135) and (Trp39, Trp108), attributes towards its strong binding. Conclusion: Utilizing the results of binding energy, we concluded stable complex formation of these hybrid ligands that could bind to TSPO with the least effect of SNP with similar interactions to known ligands. Overall, ligand 3 stands out as the best ligand having insignificant deviations per residue of protein that can be further explored and assessed in detail for future inflammation PET application after subsequent detailed biological evaluation.