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As a continuation of our earlier work against SARS-CoV-2, seven FDA-approved drugs were designated as the best SARS-CoV-2 nsp16-nsp10 2′-o-methyltransferase (2′OMTase) inhibitors through 3009 compounds. The in silico inhibitory potential of the examined compounds against SARS-CoV-2 nsp16-nsp10 2′-o-methyltransferase (PDB ID: (6W4H) was conducted through a multi-step screening approach. At the beginning, molecular fingerprints experiment with SAM (S-Adenosylmethionine), the co-crystallized ligand of the targeted enzyme, unveiled the resemblance of 147 drugs. Then, a structural similarity experiment recommended 26 compounds. Therefore, the 26 compounds were docked against 2′OMTase to reveal the potential inhibitory effect of seven promising compounds (Protirelin, (1187), Calcium folinate (1913), Raltegravir (1995), Regadenoson (2176), Ertapenem (2396), Methylergometrine (2532), and Thiamine pyrophosphate hydrochloride (2612)). Out of the docked ligands, Ertapenem (2396) showed an ideal binding mode like that of the co-crystallized ligand (SAM). It occupied all sub-pockets of the active site and bound the crucial amino acids. Accordingly, some MD simulation experiments (RMSD, RMSF, Rg, SASA, and H-bonding) have been conducted for the 2′OMTase—Ertapenem complex over 100 ns. The performed MD experiments verified the correct binding mode of Ertapenem against 2′OMTase exhibiting low energy and optimal dynamics. Finally, MM-PBSA studies indicated that Ertapenem bonded advantageously to the targeted protein with a free energy value of −43 KJ/mol. Furthermore, the binding free energy analysis revealed the essential amino acids of 2′OMTase that served positively to the binding. The achieved results bring hope to find a treatment for COVID-19 via in vitro and in vivo studies for the pointed compounds.

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Continuing our antecedent work against COVID-19, a set of 5956 compounds of traditional Chinese medicine have been virtually screened for their potential against SARS-CoV-2 helicase (PDB ID: 5RMM). Initially, a fingerprint study with VXG, the ligand of the target enzyme, disclosed the similarity of 187 compounds. Then, a molecular similarity study declared the most similar 40 compounds. Subsequently, molecular docking studies were carried out to examine the binding modes and energies. Then, the most appropriate 26 compounds were subjected to in silico ADMET and toxicity studies to select the most convenient inhibitors to be: (1R,2S)-ephedrine (57), (1R,2S)-norephedrine (59), 2-(4-(pyrrolidin-1-yl)phenyl)acetic acid (84), 1-phenylpropane-1,2-dione (195), 2-methoxycinnamic acid (246), 2-methoxybenzoic acid (364), (R)-2-((R)-5-oxopyrrolidin-3-yl)-2-phenylacetic acid (405), (Z)-6-(3-hydroxy-4-methoxystyryl)-4-methoxy-2H-pyran-2-one (533), 8-chloro-2-(2-phenylethyl)-5,6,7-trihydroxy-5,6,7,8-tetrahydrochromone (637), 3-((1R,2S)-2-(dimethylamino)-1-hydroxypropyl)phenol (818), (R)-2-ethyl-4-(1-hydroxy-2-(methylamino)ethyl)phenol (5159), and (R)-2-((1S,2S,5S)-2-benzyl-5-hydroxy-4-methylcyclohex-3-en-1-yl)propane-1,2-diol (5168). Among the selected 12 compounds, the metabolites, compound 533 showed the best docking scores. Interestingly, the MD simulation studies for compound 533, the one with the highest docking score, over 100 ns showed its correct binding to SARS-CoV-2 helicase with low energy and optimum dynamics. Finally, MM-PBSA studies showed that 533 bonded favorably to SARS-CoV-2 helicase with a free energy value of −83 kJ/mol. Further, the free energy decomposition study determined the essential amino acid residues that contributed favorably to the binding process. The obtained results give a huge hope to find a cure for COVID-19 through further in vitro and in vivo studies for the selected compounds.

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Dabigatran etexilate mesylate (DABE), a prodrug, quickly changes into dabigatran (DAB) after its oral administration. Accordingly, detecting DABE in plasma is practically unmanageable. An ultraperformance liquid chromatography–tandem mass spectrometry (UPLC–MS/MS) technique was developed and validated to compute free DAB in participants. For the first time, the central composite design, a type of response surface methodology, was applied for optimizing variables affecting the cleavage of glucuronide bond. In addition, the pharmacokinetic parameters of generic medication (okanadab) were determined, and the obtained outcomes were compared with those of the branded drug (pradaxa). The sample preparation was done using methanol as a protein precipitant and the separation was achieved using an ACQUITY UPLC BEH C18 column (2.1 × 50 mm, 1.7 μm). The elution was isocratically conducted using 10 mM ammonium formate:methanol (72:28, v/v) as a mobile phase and the flow rate was 0.25 mL/min. Multiple reaction monitoring and positive electrospray ionization were used. The determination was performed within 1 min, and the calibration growth curve was established over a range of 1.19–475 ng/mL using DAB‐d3 as a tagged internal standard. Bioequivalence research was validated following the US Food and Drug Administration (US FDA) guidelines for bioanalytical procedures and acceptable outcomes were achieved. The outcomes for okanadab and pradaxa did not differ significantly.

This research developed and validated a highly sensitive and selective UPLC–MS/MS approach using a triple quadrupole mass spectrometer for quantifying favipiravir. Moreover, we introduced a study evaluating bioequivalence using two drugs, Favibrivix and Avigan, containing favipiravir. Lean Six Sigma verified the capacity and performance of the process. Protein precipitation extraction was utilized to extract favipiravir from the collected human matrices. We used an Acquity UPLCr BEH HILIC column and valproic acid as an internal standard. Furthermore, we conducted the procedure using an isocratic elution comprising acetonitrile and 0.005% ammonia in water (75:25, v/v), a flow rate of 0.25 ml/min, a temperature controlled at 10°C and an injection volume of 1.0 μl. Our UPLC–MS/MS process has a broad range (50–10,000 ng/ml) with a determination coefficient of 0.9980. We validated the method in line with the US Food and Drug Administration. The findings revealed that the test, Favibrivix 200 mg/tablet, and the reference, Avigan® 200 mg/tablet, were statistically bioequivalent in healthy Egyptian participants.