Understanding COVID-19: From Origin to Potential Therapeutics.

Currently, a global pandemic era of public health concerns is going on with the Coronavirus Disease 2019 (COVID-19), which is caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). The first case of COVID-19 was reported from Wuhan's Huanan seafood market in China late December 2019. Bats, pangolins, and snakes have been nominated as salient carriers of the virus. Thanks to its high pathogenicity, it can cause severe respiratory infections. Fever, dry cough, sore throat, pneumonia, septic shock, and ground-glass opacities are the foremost clinical manifestations of COVID-19. Immunocompromised patients are at high risk for COVID-19 infection and may lead to death. Scientist and government agencies around the globe are putting forward their best efforts and resources for the effective treatment of human coronavirus infections; however, neither vaccines nor antiviral drugs are available for the treatment of human coronaviruses (HCoV) infections such as SARS (severe acute respiratory syndrome), MERS (Middle Eastern respiratory syndrome), and COVID-19. Since the outbreak, a plethora of research and review articles have been published. Moreover, the mass media has bombarded the public with conflicting opinions about the pandemic. There is a dire need for accurate and reliable information concerning this pandemic. In this review, we have compiled the up to date information about the origins, evolution, epidemiology, and pathogenesis of this disease. Moreover, very few reports have addressed the clinical features and current status of treatment for COVID-19; we have adequately addressed these topics in detail in this review. Finally, a detailed account of clinical trials of vaccines and other therapeutics currently in progress has been delineated.

Cyclic Peptide-Gadolinium Nanoparticles for Enhanced Intracellular Delivery.

A cyclic peptide containing one cysteine and five alternating tryptophan and arginine amino acids [(WR)5C] was synthesized using Fmoc/tBu solid-phase methodology. The ability of the synthesized cyclic peptide to produce gadolinium nanoparticles through an in situ one-pot mixing of an aqueous solution of GdCl3 with [(WR)5C] peptide solution was evaluated. Transmission electron microscopy showed the formed peptide-Gd nanoparticles in star-shape morphology with a size of ~250 nm. Flow cytometry investigation showed that the cellular uptake of a cell-impermeable fluorescence-labeled phosphopeptide (F'-GpYEEI, where F' = fluorescein) was approximately six times higher in the presence of [(WR)5C]-Gd nanoparticles than those of F'-GpYEEI alone in human leukemia adenocarcinoma (CCRF-CEM) cells after 2 h incubation. The antiproliferative activities of cisplatin and carboplatin (5 µM) were increased in the presence of [(WR)5C]-GdNPs (50 µM) by 41% and 18%, respectively, after 72-h incubation in CCRF-CEM cells. The intracellular release of epirubicin, an anticancer drug, from the complex showed that 15% and 60% of the drug was released intracellularly within 12 and 48 h, respectively. This report provides insight about using a non-toxic MRI agent, gadolinium nanoparticles, for the delivery of various types of molecular cargos.

Synthesis and Antiproliferative Activities of Conjugates of Paclitaxel and Camptothecin with a Cyclic Cell-Penetrating Peptide.

Cell-penetrating peptide [WR]5 has been previously shown to be an efficient molecular transporter for various hydrophilic and hydrophobic molecules. The peptide was synthesized using Fmoc/tBu solid-phase chemistry, and one arginine was replaced with one lysine to enable the conjugation with the anticancer drugs. Paclitaxel (PTX) was functionalized with an esterification reaction at the C2' hydroxyl group of PTX with glutaric anhydride and conjugated with the cyclic peptide [W(WR)4K(ßAla)] in DMF to obtain the peptide-drug conjugate PTX1. Furthermore, camptothecin (CPT) was modified at the C(20)-hydroxyl group through the reaction with triphosgene. Then, it was conjugated with two functionalized cyclic peptides through a formyl linker affording two different conjugates, namely CPT1 and CPT2. All the conjugates showed better water solubility as compared to the parent drug. The cytotoxicity assay of the drugs and their conjugates with the peptides were evaluated in the human breast cancer MCF-7 cell line. PTX inhibited cell proliferation by 39% while the PTX-peptide conjugate inhibited the proliferation by ~18% after 72 h incubation. On the other hand, CPT, CPT1, and CPT2 reduced the cell proliferation by 68%, 39%, and 62%, respectively, in the MCF-7 cell lines at 5 µM concentration after 72 h incubation.

Efficient Intracellular Delivery of Cell-Impermeable Cargo Molecules by Peptides Containing Tryptophan and Histidine.

We have previously evaluated and reported numerous classes of linear and cyclic peptides containing hydrophobic and hydrophilic segments for intracellular delivery of multiple molecular cargos. Herein, a combination of histidine and tryptophan amino acids were designed and evaluated for their efficiency in intracellular delivery of cell-impermeable phosphopeptides and the anti-HIV drug, emtricitabine. Two new decapeptides, with linear and cyclic natures, both containing alternate tryptophan and histidine residues, were synthesized using Fmoc/tBu solid-phase chemistry. The peptides were characterized and purified by using matrix-assisted laser desorption/ionization (MALDI) spectroscopy and high-performance liquid chromatography (HPLC), respectively. These peptides did not show significant toxicity up to 100 µM in ovarian cancer (SK-OV-3) and leukemia cancer (CCRF-CEM) cells. Furthermore, the cellular uptake of a fluorescence (F')-labeled cell-impermeable phosphopeptide (F'-GpYEEI) was enhanced in the presence of linear (WH)5 and cyclic [WH]5 by 2- and 8-fold, respectively, compared to the uptake of the phosphopeptide alone. The cellular uptake was not significantly changed in the presence of endocytosis inhibitors. Furthermore, the intracellular uptake of the fluorescently-labeled anti-HIV drug, emtricitabine (F'-FTC), by linear (WH)5 and cyclic [WH]5 in SK-OV-3 cancer cell lines was found to be enhanced by 3.5- and 9-fold, respectively, compared to that of the drug alone. Fluorescent uptake experiments confirmed the localization of F'-GpYEEI-loaded cyclic [WH]5 intracellularly in the SK-OV-3 cancer cell line after 3 h of incubation. Thus, these data demonstrated that [WH]5 containing tryptophan and histidine enhanced the cellular uptake of F'-GpYEEI and emtricitabine.

Design, Synthesis, and Evaluation of Dasatinib-Amino Acid and Dasatinib-Fatty Acid Conjugates as Protein Tyrosine Kinase Inhibitors.

Derivatives of the tyrosine kinase inhibitor dasatinib were synthesized by esterification with 25 carboxylic acids, including amino acids and fatty acids, thereby extending the drug to interact with more diverse sites and to improve specificity. The dasatinib-l-arginine derivative (Das-R, 7) was found to be the most potent of the inhibitors tested, with IC50 values of 4.4, <0.25, and <0.45 nm against Csk, Src, and Abl kinases, respectively. The highest selectivity ratio obtained in our study, 91.4 Csk/Src, belonged to compound 18 (Das-C10 ) with an IC50 value of 3.2 µm for Csk compared with 35 nm for Src. Furthermore, many compounds displayed increased selectivity toward Src over Abl. Compounds 15 (Das-glutamic acid) and 13 (Das-cysteine) demonstrated the largest gains (10.2 and 10.3 Abl/Src IC50 ratios). Das-R (IC50 =2.06 µm) was significantly more potent than the parent dasatinib (IC50 =26.3 µm) against Panc-1 cells, whereas both compounds showed IC50 <51.2 pm against BV-173 and K562 cells. Molecular modeling and binding free energy simulations revealed good agreements with the experimental results and rationalized the differences in selectivity among the studied compounds. Integration of experimental and computational approaches in the design and biochemical screening of dasatinib derivatives facilitated rational engineering and diversification of the dasatinib scaffold, providing useful insight into mechanisms of kinase selectivity.

Cyclic Peptide Containing Hydrophobic and Positively Charged Residues as a Drug Delivery System for Curcumin.

Due to the low water solubility and hydrophobic nature of curcumin, an efficient cellular uptake is critical for its biological activity. We have previously developed a number of homochiral L-cyclic peptides containing arginine and tryptophan as cell-penetrating peptides. Among the synthesized peptides, [WR]5 containing five arginine and five tryptophan residues was found to be the most efficient one. Here, we have compared the application of [WR]5 to improve the intracellular uptake of curcumin by using both peptide-curcumin conjugate and physical mixture (peptide + curcumin) strategies. Flow cytometry results showed that the intracellular uptake of curcumin (50 µM) was enhanced through the physical mixing with [WR]5 by 5.7 folds compared to that of curcumin alone in human leukemia (CCRFCEM) cells after 3 h. When [WR]5 was conjugated with curcumin, the intracellular uptake was enhanced by 4 fold. These data suggest that the physical mixture can work more efficiently in enhancing the cellular delivery of curcumin. Furthermore, the antiproliferative activity of curcumin was enhanced by 20% and ∼13% through the physical mixture and the conjugate, respectively, in CCRF-CEM cells after 72 h.

Cysteine and arginine-rich peptides as molecular carriers.

A number of linear and cyclic peptides containing alternative arginine and cysteine residues, namely linear (CR)3, linear (CR)4, linear (CR)5, cyclic [CR]4, and cyclic [CR]5, were synthesized. The peptides were evaluated for their ability to deliver two molecular cargos, fluorescence-labeled cell-impermeable negatively charged phosphopeptide (F'-GpYEEI) and fluorescence-labeled lamivudine (F'-3TC), intracellularly in human leukemia cancer (CCRF-CEM) cells. We investigated the role of cyclization and the number of amino acids in improving the transporting ability of the peptides. The flow cytometry studies suggested that the synthesized peptides were able to work efficiently as transporters for both cargos. Among all compounds, cyclic [CR]4 was found to be the most efficient peptide in transporting the cargo into cells. For instance, the cellular uptake of F'-3TC (5µM) and F'-GpYEEI (5µM) was enhanced by 16- and 20-fold, respectively, in the presence of cyclic [CR]4 compared to that of the parent compound alone. The mechanism of F'-GpYEEI uptake by cells was found to be energy-independent. The results showed that the number of amino acids and their cyclic nature can impact the efficiency of the peptide in transporting the molecular cargos.

Cyclic peptide-capped gold nanoparticles for enhanced siRNA delivery.

Previously, we have reported the synthesis of a homochiral l-cyclic peptide [WR]5 and its use for delivery of anti-HIV drugs and biomolecules. A physical mixture of HAuCl4 and the peptide generated peptide-capped gold nanoparticles. Here, [WR]5 and [WR]5-AuNPs were tested for their efficiency to deliver a small interfering RNA molecule (siRNA) in human cervix adenocarcinoma (HeLa) cells. Flow cytometry investigation revealed that the intracellular uptake of a fluorescence-labeled non-targeting siRNA (200 nM) was enhanced in the presence of [WR]5 and [WR]5-AuNPs by 2- and 3.8-fold when compared with that of siRNA alone after 24 h incubation. Comparative toxicity results showed that [WR]5 and [WR]5-AuNPs were less toxic in cells compared to other available carrier systems, such as Lipofectamine.

Benzimidazoles as new scaffold of sirtuin inhibitors: green synthesis, in vitro studies, molecular docking analysis and evaluation of their anti-cancer properties.

Two series of novel benzimidazole derivatives were designed, synthesized and evaluated for their SIRT1 and SIRT2 inhibitory activity. Among the newly synthesized compounds, compound 4j displayed the best inhibitory activity for SIRT1 (IC50 = 54.21 µM) as well as for SIRT2 (IC50 = 26.85 µM). Cell proliferation assay showed that compound 4j possessed good antitumor activity against three different types of cancer cells derived from colon (HCT-116), breast (MDA-MB-468) and blood-leukemia (CCRF-CEM) with cell viability of 40.0%, 53.2% and 27.2% respectively at 50 µM. Docking analysis of representative compound 4j into SIRT2 indicated that the interaction with receptor was primarily due to hydrogen bonding and π-π stacking interactions.

Facile, regio- and diastereoselective synthesis of spiro-pyrrolidine and pyrrolizine derivatives and evaluation of their antiproliferative activities.

A number of novel spiro-pyrrolidines/pyrrolizines derivatives were synthesized through [3+2]-cycloaddition of azomethine ylides with 3,5-bis[(E)-arylmethylidene]tetrahydro-4(1H)-pyridinones 2a-n. Azomethine ylides were generated in situ from the reaction of 1H-indole-2,3-dione (isatin, 3) with N-methylglycine (sarcosine), phenylglycine, or proline. All compounds (50 µM) were evaluated for their antiproliferative activity against human breast carcinoma (MDA-MB-231), leukemia lymphoblastic (CCRF-CEM), and ovarian carcinoma (SK-OV-3) cells. N-α-Phenyl substituted spiro-pyrrolidine derivatives (5a-n) showed higher antiproliferative activity in MDA-MB-231 than other cancer cell lines. Among spiro-pyrrolizines 6a-n, a number of derivatives including 6a-c and 6i-m showed a comparable activity with doxorubicin in all three cell lines. Among all compounds in three classes, 6a, 6b, and 6m, were found to be the most potent derivatives showing 64%, 87%, and 74% antiproliferative activity in MDA-MB-231, SK-OV-3, and CCRF-CEM cells, respectively. Compound 6b showed an IC50 value of 3.6 mM in CCRF-CEM cells. These data suggest the potential antiproliferative activity of spiro-pyrrolidines/pyrrolizines.

Amphiphilic bicyclic peptides as cellular delivery agents.

Two bicyclic peptides composed of tryptophan and arginine residues were synthesized from monocyclic peptide building blocks and evaluated as cellular delivery agents. [W5G]-(triazole)-[KR5] and [W5E]-(ß-Ala)-[KR5] containing triazole and ß-alanine linkers improved the cellular delivery of fluorescein (F')-labeled phosphopeptide F'-GpYEEI (F'-PP) by 7.6- and 19.3-fold, respectively, in human ovarian adenocarcinoma cells. However, parent monocyclic peptide [R5 ] and monocyclic peptide [WR]4 only enhanced the cellular uptake of the phosphopeptide by only 1.3- and 3.7-fold, respectively. Confocal microscopy showed that the corresponding fluorescein-labeled bicyclic peptide F'-[KW4E]-(ß-Ala)-[KR5] was localized in the cytosol and nucleus. Studying the cellular uptake of F'-[KW4E]-(ß-Ala)-[KR5] in the presence of endocytosis inhibitors indicated that the clathrin- and caveolin-dependent endocytosis are the main pathways for cellular uptake. The bicyclic peptide was able to improve antiproliferative activity of doxorubicin by 20 %. These data suggest that this bicyclic peptide can be utilized as a new class of cell-penetrating peptides and cellular delivery tools.

Synthesis of 4-aryl-6-indolylpyridine-3-carbonitriles and evaluation of their antiproliferative activity.

A novel class of 6-indolypyridine-3-carbonitrilile derivatives were synthesized and evaluated for antiproliferative activities to establish structure-activity relationship. The synthesis was carried out through one-pot multicomponent reaction of 3-acetylindole, aromatic aldehydes, ethyl cyanoacetate, and ammonium acetate in the presence of piperidine as a catalyst, using a microwave irradiation method or a traditional thermal method. This was followed by chlorination for compounds 13a-e and subsequent nucleophilic substitution of the chlorine group by ethylenediamine at C2 position of the pyridine ring. The antiproliferative activity of these new nicotinonitriles was evaluated against human ovarian adenocarcinoma (SK-OV-3), breast adenocarcinoma (MCF-7), and cervix adenocarcinoma (HeLa) cells. Among all compounds, 2-((2-aminoethyl)amino)-4-aryl-6-indolylnicotinonitriles series (15a, 15b, 15d, and 15e) exhibited higher antiproliferative activity cells with IC50 values of 4.1-13.4 µM.

Synthesis and evaluation of novel benzimidazole derivatives as sirtuin inhibitors with antitumor activities.

A total of 15 novel benzimidazole derivatives were designed, synthesized and evaluated for their SIRT1 and SIRT2 inhibitory activity. All compounds showed better inhibition on SIRT2 as compared to SIRT1. Among these, compound 5j displayed the best inhibitory activity for SIRT1 (IC50=58.43µM) as well as for SIRT2 (IC50=45.12µM). Cell cytotoxicity assays also showed that compound 5j possesses good antitumor activity against two different cancer cell lines derived from breast cancer (MCF-7 and MDA-MB-468). A simple structure-activity-relationship (SAR) study of the newly synthesized benzimidazole derivatives was also discussed.

Synthesis and evaluation of antiproliferative activity of substituted N-(9-oxo-9H-xanthen-4-yl)benzenesulfonamides.

Several novel N-(9-oxo-9H-xanthen-4-yl)benzenesulfonamides derivatives were prepared as potential antiproliferative agents. The in vitro antiproliferative activity of the synthesized compounds was investigated against a panel of tumor cell lines including breast cancer cell lines (MDA-MB-231, T-47D) and neuroblastoma cell line (SK-N-MC) using MTT colorimetric assay. Etoposide, a well-known anticancer drug, was used as a positive standard drug. Among synthesized compounds, 4-methoxy-N-(9-oxo-9H-xanthen-4-yl)benzenesulfonamide (5i) showed the highest antiproliferative activity against MDA-MB-231, T-47D, and SK-N-MC cells. Furthermore, pentafluoro derivatives 5a and 6a exhibited higher antiproliferative activity than doxorubicin against human leukemia cell line (CCRF-CEM) and breast adenocarcinoma (MDA-MB-468) cells. Structure-activity relationship studies revealed that xanthone benzenesulfonamide hybrid compounds can be used for development of new lead anticancer agents.

Self-Assembled Surfactant Cyclic Peptide Nanostructures as Stabilizing Agents.

A number of cyclic peptides including [FR]4, [FK]4, [WR]4, [CR]4, [AK]4, and [WK]n (n = 3-5) containing L-amino acids were produced using solid-phase peptide synthesis. We hypothesized that an optimal balance of hydrophobicity and charge could generate self-assembled nanostructures in aqueous solution by intramolecular and/or intermolecular interactions. Among all the designed peptides, [WR]n (n = 3-5) generated self-assembled vesicle-like nanostructures at room temperature as shown by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and/or dynamic light scattering (DLS). This class of peptides represents the first report of surfactant-like cyclic peptides that self-assemble into nanostructures. A plausible mechanistic insight into the self-assembly of [WR]5 was obtained by molecular modeling studies. Modified [WR]5 analogues, such as [WMeR]5, [WR(Me)2]5, [WMeR(Me)2]5, and [WdR]5, exhibited different morphologies to [WR]5 as shown by TEM observations. [WR]5 exhibited a significant stabilizing effect for generated silver nanoparticles and glyceraldehyde-3-phosphate dehydrogenase activity. These studies established a new class of surfactant-like cyclic peptides that self-assembled into nanostructures and could have potential applications for the stabilization of silver nanoparticles and protein biomolecules.

Copper triflate-mediated synthesis of 1,3,5-triarylpyrazoles in [bmim][PF6] ionic liquid and evaluation of their anticancer activities.

A simple, efficient, and environment friendly protocol for the synthesis of 1,3,5-triarylpyrazole and 1,3,5-triarylpyrazolines in [bimm][PF6] ionic liquid mediated by Cu(OTf)2 is described. The reaction protocol gave 1,3,5-triarylpyrazoles in good to high yields (71-84%) via a one-pot addition-cyclocondensation between chalcones and arylhydrazines, and oxidative aromatization without requirement for an additional oxidizing reagent. The catalyst can be reused up to four cycles without much loss in the catalytic activity. The pyrazoles (4a-o) and pyrazolines (3a-n) were evaluated for antiproliferative activity in SK-OV-3, HT-29, and HeLa human cancer cells lines. Among all compounds, 3b inhibited cell proliferation of HeLa cells by 80% at a concentration of 50 µM.

Synthesis and antiproliferative activities of quebecol and its analogs.

Simple and efficient synthesis of quebecol and a number of its analogs was accomplished in five steps. The synthesized compounds were evaluated for antiproliferative activities against human cervix adenocarcinoma (HeLa), human ovarian carcinoma (SK-OV-3), human colon carcinoma (HT-29), and human breast adenocarcinoma (MCF-7) cancer cell lines. Among all the compounds, 7c, 7d, 7f, and 8f exhibited antiproliferative activities against four tested cell lines with inhibition over 80% at 75 µM after 72 h, whereas, compound 7b and 7g were more selective towards MCF-7 cell line. The IC50 values for compounds 7c, 7d, and 7f were 85.1 µM, 78.7 µM, and 80.6 µM against MCF-7 cell line, respectively, showing slightly higher antiproliferative activtiy than the synthesized and isolated quebecol with an IC50 value of 104.2 µM against MCF-7.

4-Aryl-4H-naphthopyrans derivatives: one-pot synthesis, evaluation of Src kinase inhibitory and anti-proliferative activities.

BACKGROUND: A series of 2-amino-4-aryl-4H-benzo[h or f]chromene-3-carbonitrile derivatives were synthesized and evaluated for inhibition of Src kinase and cell proliferation in breast carcinoma (BT-20) cell lines. METHODS: The one-pot, three-component reaction of α or ß-naphthol, malonitrile and an aromatic aldehyde in the presence of diammonium hydrogen phosphate was afforded the corresponding 2-amino-4-aryl-4H-benzo[h or f]chromene-3-carbonitrile derivatives, All target compounds were evaluated for inhibition of Src kinase and cell proliferation in breast carcinoma (BT-20) cell lines. RESULTS: Among all tested compounds, unsubstituted 4-phenyl analog 4a showed Src kinas inhibitory effect with IC50 value of 28.1 µM and was the most potent compound in this series. In general, the compounds were moderately active against BT-20. 3-Nitro-phenyl 4e and 3-pyridinyl 4h derivatives inhibited the cell proliferation of BT-20 cells by 33% and 31.5%, respectively, and found to be more potent compared to doxorubicin (25% inhibition of cell growth). CONCLUSION: The data indicate that 4-aryl-4H-naphthopyrans scaffold has the potential to be optimized further for designing more potent Src kinase inhibitors and/or anticancer lead compounds.

One-pot regioselective synthesis of tetrahydroindazolones and evaluation of their antiproliferative and Src kinase inhibitory activities.

A number of 2-substituted tetrahydroindazolones were synthesized by three-component condensation reaction of 1,3-diketones, substituted hydrazines, benzaldehydes, and Yb(OTf)(3) as a catalyst in [bmim][BF(4)] ionic liquid using a simple, efficient, and economical one-pot method. The synthesized tetrahydroindazolones were evaluated for inhibition of cell proliferation of human colon carcinoma (HT-29), human ovarian adenocarcinoma (SK-OV-3), and c-Src kinase activity. 3,4-Dichlorophenyl tetrahydroindazolone derivative (15) inhibited the cell proliferation of HT-29 and SK-OV-3 cells by 62% and 58%, respectively. 2,3-Diphenylsubstituted tetrahydroindazolone derivatives, inhibited the cell proliferation of HT-29 cells by 65-72% at a concentration of 50 µM. In general, the tetrahydroindazolones showed modest inhibition of c-Src kinase where 4-tertbutylphenyl- and 3,4-dichlorophenyl- derivatives showed the inhibition of c-Src kinase with IC(50) values of 35.1 and 50.7 µM, respectively.