Forced Degradation Studies of Ivabradine and In Silico Toxicology Predictions for Its New Designated Impurities

First eco-toxicological evidence of ivabradine effect on the marine bacterium Vibrio fischeri: A chiral view

Ivabradine (S-ivabradine) is a contemporary antihypertensive drug designed and commercialized for cardiovascular diseases treatment over the world. In this work the enantiomer-specific stability and acute toxicity of ivabradine to the marine bacterium Vibrio fischeri as well as the potential mechanism of action were investigated for the first time. With this aim, real concentrations of ivabradine enantiomers under abiotic and biotic conditions were determined by Capillary Electrophoresis (CE) with cyclodextrins (CDs) as chiral selectors. A moderate chiral stability without enantiomeric interconversion was observed for ivabradine. The bioluminescence inhibition method revealed an enantioselective toxicity of ivabradine to marine bacterium. The order of ecotoxicity was R-ivabradine < racemic ivabradine < S-ivabradine with EC50 (t = 5 min) values about 75.98, 11.11 and 7.93 mg/L, respectively. Confocal Live/Dead stained images showed that bacterial envelops cells were seriously damaged after exposure to S-ivabradine. S-ivabradine also disturbed the esterase activity and significantly increased the ROS level compared with the control. Thus, oxidative stress originating membrane cells damage and enzymatic activity changes was shown to be the primary mechanism of S-ivabradine toxicity to marine bacterium. Our results highlight the need for more eco-toxicological evaluations of the cardiovascular drug S-ivabradine on other aquatic organisms to establish the risk on the environment.

N,N′-dialkyl-2-thiobarbituric acid based sulfonamides as potential SARS-CoV-2 main protease inhibitors

An efficient methodology was developed to generate novel N,N′-dialkyl-2-thiobarbituric acid based sulfonamides S1–S4 in good to excellent yields (84%–95%). The synthesized compounds S1–S4 were docked to screen their in silico activities against two enzymes i.e., SARS-CoV-2 main protease enzyme with unliganded active site (2019-nCoV, coronavirus disease 2019, COVID-19) PDB ID: 6Y84 and SARS-CoV-2 Mpro PDB ID: 6LU7. Furthermore, some in silico physicochemical and physicokinetic properties were evaluated using the OSIRIS Property Explorer, Molinspiration property calculator, ADMET property calculator, and GUSAR to assess these compounds as potential candidates as lead compounds for the quest of SARS-CoV-2 main protease inhibitors. Molecular docking analyses of the synthesized compounds predicted that compound S3 is more potent as SARS-CoV-2 main protease inhibitor with binding energy –11.65 kcal/mol in comparison with reference inhibitor N3 (–10.95 kcal/mol), whereas compounds S1, S2, and S4 recorded comparable binding energies –9.89, –10.84, and –10.94 kcal/mol with reference inhibitor N3, which were much better than remdesivir (–9.85 kcal/mol). In case of SARS-CoV-2 Mpro, all compounds S1–S4 with docking energy values of –7.28, –8.38, –8.31, and –7.34 kcal/mol, respectively, were found to be potent in comparison with reference inhibitor N3 (–6.31 kcal/mol) and remdesivir (–6.33 kcal/mol). Ligand efficiency values against the target SARS-CoV-2 proteins, as well as α-glucosidase and DNA-(apurinic or apyrimidinic site) lyase inhibition results of these newly synthesized compounds, were also found to be promising.

'In silico' toxicology methods in drug safety assessment

While experimental animal investigation has historically been the most conventional approach conducted to assess drug safety and is currently considered the main method for determining drug toxicity, these studies are constricted by cost, time, and ethical approvals. Over the last 20 years, there have been significant advances in computational sciences and computer data processing, while knowledge of alternative techniques and their application has developed into a valuable skill in toxicology. Thus, the application of in silico methods in drug safety assessment is constantly increasing. They are very complex and are grounded on accumulated knowledge from toxicology, bioinformatics, biochemistry, statistics, mathematics, as well as molecular biology. This review will summarize current state-of-the-art scientific data on the use of in silico methods in toxicity testing, taking into account their shortcomings, and highlighting the strategies that should deliver consistent results, while covering the applications of in silico methods in preclinical trials and drug impurities toxicity testing.

A Proline-Based Tectons and Supramolecular Synthons for Drug Design 2.0: A Case Study of ACEI

Proline is a unique, endogenous amino acid, prevalent in proteins and essential for living organisms. It is appreciated as a tecton for the rational design of new bio-active substances. Herein, we present a short overview of the subject. We analyzed 2366 proline-derived structures deposited in the Cambridge Structure Database, with emphasis on the angiotensin-converting enzyme inhibitors. The latter are the first-line antihypertensive and cardiological drugs. Their side effects prompt a search for improved pharmaceuticals. Characterization of tectons (molecular building blocks) and the resulting supramolecular synthons (patterns of intermolecular interactions) involving proline derivatives, as presented in this study, may be useful for in silico molecular docking and macromolecular modeling studies. The DFT, Hirshfeld surface and energy framework methods gave considerable insight into the nature of close inter-contacts and supramolecular topology. Substituents of proline entity are important for the formation and cooperation of synthons. Tectonic subunits contain proline moieties characterized by diverse ionization states: -N and -COOH(-COO-), -N+ and -COOH(-COO-), -NH and -COOH(-COO-), -NH+ and -COOH(-COO-), and -NH2+ and -COOH(-COO-). Furthermore, pharmacological profiles of ACE inhibitors and their impurities were determined via an in silico approach. The above data were used to develop comprehensive classification, which may be useful in further drug design studies.

Simultaneous determination of chiral and achiral impurities of ivabradine on a cellulose tris(3-chloro-4-methylphenylcarbamate) chiral column using polar organic mode

A high performance liquid chromatographic method was developed for the simultaneous determination of the related substances (R-ivabradine, dehydro-S-ivabradine, N-demethyl-S-ivabradine, ((S)-3,4-dimethoxy-bicyclo[4.2.0]octa-1,3,5-triene-7-yl-methyl)-methyl-amine) and 1-(7,8-dimethoxy-1,3,4,5-tetrahydro-2H-3-benzazepine-2-on-3-yl)-3-chloro-propane) of the heart-rate lowering drug, ivabradine. The separation capability of seven different polysaccharide-type chiral columns (Lux Amylose-1, Lux i-Amylose-1, Lux Amylose-2, Lux Cellulose-1, Lux Cellulose-2, Lux Cellulose-3 and Lux Cellulose-4) was investigated with a mobile phase consisting of 0.1% diethylamine in methanol, 2-propanol and acetonitrile. During the screnning experiments the best results were obtained on Lux Cellulose-2 (based on cellulose tris(3-chloro-4-methylphenylcarbamate) column with methanol with an ideal case, where all the impurities eluted before the S-ivabradine peak. Chromatographic parameters (flow rate, temperature and mobile phase constituents) were optimized by a full factorial screening design. Using optimized parameters (Lux Cellulose-2 column with 0.06% (v/v) diethylamine in methanol/acetonitrile 98/2 (v/v) with 0.45 mL/min flow rate at 12 °C) baseline separations were achieved between all compounds. The optimized method was validated according to the International Council on Harmonization Q2(R1) guideline and proved to be reliable, linear, precise and accurate for determination of at least 0.05% for all impurities in S-ivabradine samples. Method application was tested on a commercial tablet formulation and proved to be suitable for routine quality control of both chiral and achiral related substances of S-ivabradine.

In silico ADME and Toxicity Prediction of Ceftazidime and Its Impurities

To improve the quality control of drugs, we predicted the absorption, distribution, metabolism, excretion, and toxicity (ADMET) of ceftazidime (CAZ) and its impurities via in silico methods. We used three types of quantitative structure-activity relationship and docking software for precise prediction: Discovery Studio 4.0, OECD QSAR Toolbox 4.1, Toxtree, and the pkCSM approach. The pharmacokinetics and toxicity of ceftazidime and impurity A (Δ-2-CAZ) are similar. The biological properties of impurity B (CAZ E-isomer) are different from CAZ. Therefore, we focused on drug stability to analyze impurity B. Impurities D and I have strong lipophilicity, good intestinal absorption, and poor excretion in the body. Impurity D is particularly neurotoxic and genotoxic. It is important to control the content of impurity D. The toxicity of impurity F is low, but the toxicity is enhanced when it becomes the C-3 side chain of CAZ and forms a quaternary amine group. We conclude that the beta-lactam ring of nucleus, the quaternary amine group at the C-3 side chain, and the acetates at the C-7 side chain of CAZ are the main toxic functional groups. Impurities B and D may be the genetic impurity in CAZ and may also have neurotoxicity. This in silico approach can predict the toxicity of other cephalosporins and impurities.

Application and Validation of Simple Isocratic HPLC-UV-DAD Method with Dual Wavelength Detection for Ivabradine Determination and Its Application in the Study of Stress Degradation

Ivabradine is a modern drug that selectively lowers the heart rate, improves cardiac energy balance, and reduces heart’s demands for oxygen and energy. Due to the chemical nature of ivabradine, which absorbs light at 207 nm and 286 nm, its detection was performed at two wavelengths. A Knauer C8 column was used to develop the RP-HPLC method for determination of ivabradine. The proposed method was linear from 5 to 100 µg/ml (r>0.999) for both wavelengths and limits of detection (LOD) and limits of quantification (LOQ) were 0.33 and 1.09 µg/ml for 207 nm and 1.19 and 3.97 µg/ml for 286 nm, respectively. After validation, the investigated method was applied to a stress degradation study. Numerous degradation products were formed from ivabradine solutions through alkaline and acid hydrolysis, oxidation, and photolysis. The largest numbers of degradation products were found in the sample exposed to 24 h radiation and alkaline hydrolysis (eight and six products, resp.). Finally, the simple method using HPLC-UV-DAD was developed and validated. Its usefulness for the monitoring of possible degradation products was demonstrated.