A new fluorescence probe for sofosbuvir analysis in dosage form and spiked human plasma

A simple, rapid, and low-cost technique was developed to allow reliable analysis of the anti-hepatitis C drug sofosbuvir in bulk, tablet form, and spiked human plasma. This method depends on the ability of sofosbuvir to quench the fluorescence of the newly synthesized 2-amino-3-cyano-4,6-dimethylpyridine (reagent 3). Elemental analysis and spectral data were used to validate the structure of the synthesized reagent. The newly synthesized reagent exhibited a satisfactory level of fluorescence emission at 365 nm after excitation at 247 nm. All experimental variables that might affect the quenching process were analyzed and optimized. Linearity, range, accuracy, precision, limit of detection (LOD), and limit of quantitation (LOQ) were all validated in accordance with the International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use (ICH) guidelines. The concentration range was shown to be linear between 0.1 and 1.5 μg/mL. The technique was effectively utilized for sofosbuvir analysis in both its tablet dosage form and spiked human plasma, with mean percentage recoveries of 100.13 ± 0.35 and 94.26 ± 1.69, respectively.

Fitness-Dependent, Mild Mutagenic Activity of Sofosbuvir for Hepatitis C Virus

The concept of a mild mutagen was coined to describe a minor mutagenic activity exhibited by some nucleoside analogues that potentiated their efficacy as antiretroviral agents. In the present study, we report the mild mutagen activity of sofosbuvir (SOF) for hepatitis C virus (HCV). Serial passages of HCV in human hepatoma cells, in the presence of SOF at a concentration well below its cytotoxic concentration 50 (CC50) led to pre-extinction populations whose mutant spectra exhibited a significant increase of C→U transitions, relative to populations passaged in the absence of SOF. This was reflected in an increase in several diversity indices that were used to characterize viral quasispecies. The mild mutagenic activity of SOF was largely absent when it was tested with isogenic HCV populations that displayed high replicative fitness. Thus, SOF can act as a mild mutagen for HCV, depending on HCV fitness. Possible mechanisms by which the SOF mutagenic activity may contribute to its antiviral efficacy are discussed.

Mini Review on Forced Degradation Studies on Anti-Epileptic Drugs and Beyond

In this review on the forced degradation studies on anti-epileptic drugs and the development of validated stability-indicating assay methods for drug substances and products at a condition more severe than accelerated condition (i.e. 40 ± 2°C, 75 ± 5% relative humidity), the drug substance and drug product undergo degradation is known as forced or stress degradation. To know about the impurities developed during the storage of drug products in various environmental conditions. The limit of degradation allowable is 5-20%. More than 20% of degradation is abnormal and must be investigated. Any regulatory guidelines do not mention the pH conditions for acid or base hydrolysis, the temperature for thermal degradation or the concentration of the oxidation agent. Only International Conference on Harmonization (ICH) guidelines Q1B photostability stability and states that light sources must be a combination of UV and visible light. The shortcomings of mentioned techniques with appreciation to regulatory necessities are highlighted. A systematic method for the forced degradation studies on anti-epileptic drugs such as "Topiramate, Vigabatrin, Lacosamide, Tiagabine, Levetiracetam and Zonisamide" is discussed. This review helps researchers to get an idea about stability-indicating methods of development and validation for newer antiepileptic drugs and the characteristics of drug products that degrade under specific degradation conditions.

Application of different spectrophotometric methods for quantitative analysis of direct acting antiviral drugs simeprevir and sofosbuvir

Simeprevir and sofosbuvir are direct-acting antiviral drugs approved for the treatment of chronic HCV infection. Reports demonstrate the similarities between HCV and SARS-CoV-2 in terms of structure and replication mechanism. Therefore, it is suggested that a combination of simeprevir and sofosbuvir may be considered for COVID-19 patients. To date, no spectrophotometric methods have been published for quantitative analysis of simeprevir and sofosbuvir in combination. In this work, two simple spectrophotometric methods allowed quantitative analysis of the studied drugs in the mixed form. The zero-order direct method allowed quantitative analysis of simeprevir at 333 nm, with sofosbuvir showing zero absorbance values. The dual wavelength method allowed quantitative analysis of sofosbuvir by measuring the difference in absorbance values at 259.40 and 276 nm, where the difference in absorbance values of simeprevir was zero. With the applied methods, the investigated drugs in the mixtures and tablets prepared in the laboratory were successfully analyzed quantitatively with acceptable results.

Preparation and Characterization of Indomethacin Supramolecular Systems with β-Cyclodextrin in Order to Estimate Photostability Improvement

Cyclodextrins have found wide application in contemporary chemistry, pharmacy and medicine. Because of their unique properties, cyclodextrins are constantly used in research on solubility or stability improvement, as well as other physicochemical properties of medicinal substances. Indomethacin (IND) is a photolabile molecule that also attracts the interest of researchers due to its therapeutic potential and the need to overcome its problematic photosensitivity. Supramolecular complexes of indomethacin with β-cyclodextrin (CD) are already known, and they show greater stability compared to complexes with other types of cyclodextrins. So far, however, the sensitivity to light of physical mixtures and inclusion complexes in the solid phase has not been studied, and their various stoichiometries have not yet been investigated. Due to this fact, the aim of the present study is to obtain supramolecular systems (inclusion complexes and physical mixtures) of indomethacin with three different amounts of β-cyclodextrin. Assessment of the photochemical stability of indomethacin-β-cyclodextrin systems in the solid state is performed in order to find the best correlation between IND stability and the amount of CD. Comparative analysis of physicochemical degradation for stoichiometry systems [CD:IND] = [1:1], [0.5:1] and [0.1:1] is performed by using ultraviolet spectroscopy, transmission—FTIR, reflection—ATR-FTIR infrared spectroscopy and DSC calorimetry.

Recent advances in the chromatographic determination of the most commonly used anti-hepatitis C drug sofosbuvir and its co-administered drugs in human plasma

Sofosbuvir is a direct-acting antiviral drug that inhibits hepatitis C virus (HCV) NS5B polymerase, which in turn affects the virus replication inside biological systems. The clinical importance of sofosbuvir is based not only on its effect on HCV but also on other lethal viruses such as Zika and severe acute respiratory syndrome coronavirus disease 2019 (SARS-COVID-19). Accordingly, there is a continuous shedding of light on the development and validation of accurate and fast analytical methods for the determination of sofosbuvir in different environments. This work critically reviews the recent advances in chromatographic methods for the analysis of sofosbuvir and/or its metabolites in pure samples, pharmaceutical dosage forms, and in the presence of other co-administered drugs to highlight the current status and future perspectives to enhance its determination in different matrixes.

HPLC-UV and TLC-Densitometry Methods for Simultaneous Determination of Sofosbuvir and Daclatasvir: Application to Darvoni® Tablet

Sofosbuvir and daclatasvir are co-formulated as directly acting antiviral agents used for treatment of hepatitis C virus. Two chromatographic methods were developed for their determination; the first one is an Reversed phase-high performance liquid chromatography (RP-HPLC) method, in which the separation was performed on C8 Zorbax® SB column (4.6 × 250 mm, 5 μm) using acetonitrile:water:0.05 M phosphate buffer, pH = 8 (50:45:5, v/v/v) as a mobile phase, and ultraviolet detection was performed at 280 nm. Good resolution was obtained, and linearity was confirmed in the range of 10-100 μg/mL for both drugs. The second method is Thin layer chromatography (TLC)-densitometric one, in which sofosbuvir and daclatasvir were separated on silica gel plates using ethyl acetate:hexane:methanol (9:0.5:0.5, v/v/v) as a developing system and the scanning wavelength was 280 nm. Linearity was confirmed over a concentration range of 0.4-25.4 μg/band for sofosbuvir, whereas for daclatasvir linearity scanning was in the range of 0.4-12.8 μg/band. Both antiviral agents can be quantified simultaneously in one analytical run, which is a great time- and cost-saving valor of the developed methods. This valor is even more important in the case of the combined dosage form (Darvoni® tablets) to the pharmaceutical market.

Multivariable Manipulation of Spectrophotometric Data with Genetic Algorithm Selection for Novel Quantitative Resolution of Five Antiviral Drugs in Their Pharmaceutical Products

BACKGROUND

In many real-world situations there are many components in a mixture that produce an enormous amount of information.

OBJECTIVE

The main task is to build up balanced models that convert these data into meaningful information to deal with. Hence, different chemometric models were applied for the analysis of data obtained from a mixture containing sofosbuvir, ledipasvir, velpatasvir, daclatasvir, and valacyclovir that were recently used internationally for their antiviral activity.

METHODS

Partial Least Squares, Spectral Residual Augmented Classical Least Squares, and Concentration Residual Augmented Classical Least Squares designs were applied with and without variable selection procedure [Genetic Algorithm (GA)]. The methods were used for the quantitative analysis of the drugs in laboratory prepared mixtures and real market sample through handling the UV spectral data.

RESULTS

Robust models were obtained by applying GA. The proposed methods were found to be rapid, simple, and required no preliminary separation steps.

CONCLUSION

These models can be used on a routine basis in quality control laboratories or factories giving competitor results to those obtained by the reported methods.

HIGHLIGHTS

The proposed models offer a powerful analytical alternative for laboratories that consider economic strategies in their requirements.

A Review on Analytical Strategies for the Assessment of Recently Approved Direct Acting Antiviral Drugs

Human beings are in dire need of developing an efficient treatment against fierce viruses like hepatitis C virus (HCV) and Coronavirus (COVID-19). These viruses have already caused the death of over two million people all over the world. Therefore, over the last years, many direct-acting antiviral drugs (DAADs) were developed targeting nonstructural proteins of these two viruses. Among these DAADs, several drugs were found more effective and safer than the others as sofosbuvir, ledipasvir, grazoprevir, glecaprevir, voxilaprevir, velpatasvir, elbasvir, pibrentasvir and remdesivir. The last one is indicated for COVID-19, while the rest are indicated for HCV treatment. Due to the valuable impact of these DAADs, larger number of analytical methods were required to meet the needs of the clinical studies. Therefore, this review will highlight the current approaches, published in the period between 2017 to present, dealing with the determination of these drugs in two different matrices: pharmaceuticals and biological fluids with the challenges of analyzing these drugs either alone, with other drugs, in presence of interferences (pharmaceutical excipients or endogenous plasma components) or in presence of matrix impurities, degradation products and metabolites. These approaches include spectroscopic, chromatographic, capillary electrophoretic, voltametric and nuclear magnetic resonance methods that have been reported during this period. Moreover, the analytical instrumentation and methods used in determination of these DAADs will be illustrated in tabulated forms.

A Novel Liquid Chromatographic Method for the Quantitative Determination of Degradation Products in Remdesivir Injectable Drug product

An effectual and stability signifying technique has been validated for the quantitative verification of degradation products in Remdesivir Injectable pharmaceutical products by employing high-performance liquid chromatography with ultraviolet detector. The process was optimized by using an octyldecylsilane chemically bonded column (Kromasil KR100-5 C18; USP L1 phase) with dimensions; 250 mm length × 4.5 mm inner diameter and 5-μm particle size. The method was validated as per International Conference on Harmonization and other current regulatory guidelines for analytical method validation. The anticipated process was found to be robust, accurate, specific, linear, precise, stable and rugged in the concentration ranging from quantification level to 200% of the specification level of specified and unknown degradation impurities. The technique was effectively applied to analyze degradation products in Remdesivir Injectable drug products.

Validated Reversed-Phase Liquid Chromatographic Method with Gradient Elution for Simultaneous Determination of the Antiviral Agents: Sofosbuvir, Ledipasvir, Daclatasvir, and Simeprevir in Their Dosage Forms

A simple, rapid, sensitive, and precise reversed-phase liquid chromatographic method was developed and validated for the simultaneous determination of four direct-acting antivirals, sofosbuvir (SF), ledipasvir (LD), declatasvir (DC), and simeprevir (SM), in their respective pharmaceutical formulations. Effective chromatographic separation was achieved on an Agilent Eclipse plus C8 column (250 mm × 4.6 mm, 5 µm) at 40 °C with gradient elution using a mobile phase composed of acetonitrile:phosphate buffer (pH 6.5). The quantification of SF and DC was based on peak area measurements at 260 nm, while the quantification of LD and SM was achieved at 330 nm. The linearity was acceptable from 1.0 to 20.0 μg/mL for the studied drugs, with correlation coefficients >0.999. The analytical performance of the newly proposed HPLC procedure was thoroughly validated according to ICH guidelines in terms of linearity, precision (RSD%, 0.39-1.57), accuracy (98.05-101.90%), specificity, limit of detection (LOD) (0.022-0.039 μg/mL), limit of quantification (LOQ) (0.067-0.118 μg/mL), and robustness. The validated HPLC method was successfully used to analyze the abovementioned drugs in their pure and dosage forms without interference from common excipients present in commercial formulations.

Rapid Raman Spectroscopic Analysis of Stress Induced Degradation of the Pharmaceutical Drug Tetracycline

Stress factors caused by inadequate storage can induce the unwanted degradation of active compounds in pharmaceutical formulations. Resonance Raman spectroscopy is presented as an analytical tool for rapid monitoring of small concentration changes of tetracycline and the metabolite 4˗epianhydrotetracycline. These degradation processes were experimentally induced by changes in temperature, humidity, and irradiation with visible light over a time period of up to 23 days. The excitation wavelength λ_exc = 413 nm was proven to provide short acquisition times for the simultaneous Raman spectroscopic detection of the degradation of tetracycline and production of its impurity in small sample volumes. Small concentration changes could be detected (down to 1.4% for tetracycline and 0.3% for 4-epianhydrotetracycline), which shows the potential of resonance Raman spectroscopy for analyzing the decomposition of pharmaceutical products.

Two novel UPLC methods utilizing two different analytical columns and different detection approaches for the simultaneous analysis of velpatasvir and sofosbuvir: application to their co-formulated tablet

In the present study two different RSLC columns, Acclaim RSLC 120 C18, 5.0 µm, 4.6 × 150 mm (column A) and Acclaim RSLC 120 C18, 2.2 µm, 2.1 × 100 mm (Column B) were utilized for the analysis of velpatasvir (VPS) in presence of sofosbuvir (SFV), where due to the encountered fluorescent properties of VPS fluorescent detection at 405 nm after excitation at 340 nm (Method 1) was used for its detection where the non-fluorescent SFV did not interfere. The same columns were further utilized for the simultaneous determination of SFV and VPS either in bulk form or in their combined tablet, where UV- spectrophotometric detection at 260 nm was selected for the simultaneous analysis of both drugs (Method 2). A mobile phase consisting of NaH2PO4, pH 2.5 (with phosphoric acid) and acetonitrile in a ratio of 60:40 v/v was used for both methods. The mobile phase was pumped at a flow rate of 1.0 mL/min when using column, A and 0.5 mL/min when using column B. The methods showed good linearity over the concentration ranges of 1.0-5.0 and 2.5-10.0 ng/mL for VPS when utilizing Method 1 A and B respectively. Where the linearity concentration range was from 30.0-150.0 to 120-600.0 ng/mL for VPS and SFV respectively when applying Method 2. Both methods 1 and 2 were performed by utilizing the two analytical columns. The different chromatographic parameters as retention time, resolution, number of theoretical plates (N), capacity factor, tailing factor and selectivity were carefully optimized. The results show that comparing the performance of the two utilized columns revealed that shorter column (2.1 mm × 100 mm) with small particle packing was superior to the longer column (4.6 × 150 mm) for the analysis of the studied drugs allowing a reduction of the analysis time by 70% without any detrimental effect on performance. This prompts the decrease of the investigation costs by saving money on organic solvents and expanding the overall number of analyses per day.

Development and validation of a versatile HPLC-DAD method for simultaneous determination of the antiviral drugs daclatasvir, ledipasvir, sofosbuvir and ribavirin in presence of seven potential impurities. Application to assay of dosage forms and dissolution studies

This study describes a simple, sensitive, specific and generic HPLC-DAD method for simultaneous determination of four drugs prescribed for treatment of Hepatitis C Virus (HCV) infection. Investigated drugs include daclatasvir (DAC), ledipasvir (LED), sofosbuvir (SOF) and ribavirin (RIB). Successful separation was accomplished using Thermohypersil BDS-C8 column (4.6 × 250 mm, 5 µm) with gradient elution of the mobile phase consisted of mixed phosphate buffer pH 7.5 and methanol. Gradient elution started with 25% methanol, ramped up linearly to 80% in 15 min then kept constant till the end of the run. Flow rate was 1.5 mL/min. Peak areas were measured at 235, 260, 315, and 332 nm for RIB, SOF, DAC, and LED, respectively. Peaks of the analytes were perfectly resolved with retention times 2.0, 12.1, 14.7, and 17.2 min for RIB, SOF, DAC, and LED, respectively. The developed method was validated according to ICH guidelines with respect to system suitability, linearity, ranges, accuracy, precision, specificity, robustness, and limits of detection and quantification. The proposed method showed good linearity in the ranges 5-500, 2-300, 0.5-75, and 0.5-75 µg/mL for RIB, SOF, DAC, and LED respectively. Limits of detection were 0.10-0.66 μg/mL for the analyzed drugs. Specificity was established by separation of target drugs from 7 process-related impurities for SOF including its major metabolite (GS-331007). Applicability of the proposed method to real life situations was assessed through the analysis of four different pharmaceutical formulations and satisfactory results were obtained. Additionally, dissolution profiles of the 4 drugs were studied using the developed method.

Current regulatory requirements and practical approaches for stability analysis of pharmaceutical products: A comprehensive review

Different regulatory guidelines recommend establishing stability profile of pharmaceuticals at the time of drug development. The expiry date, retesting period and storage conditions of active drugs or products are established through stability analysis. Several regulatory guidelines exist for stability testing of pharmaceuticals. Mostly, ICH stability guidelines are followed in practice. This guideline recommends to validate stability indicating method using forced degradation samples that contains all possible degradation impurities. ICH guidelines provide general recommendations for inclusion of stability indicating parameters in a stability testing protocol. However, those guidelines do not provide specific requirements and experimental methodology to be followed for stability studies. Due to this gap, often confusion arises in the scientific community in designing stability testing protocol. Therefore, significant variations are observed in reported literature in selection of stability indicating parameters. Procedural dissimilarity amongst reported stability studies is also evident. This review discusses the regulatory guidelines and procedures to follow in performing stability testing of pharmaceuticals. Scope of this review also includes recommendations on practical approaches for designing stability testing protocol to fulfill current regulatory requirements for drug substances and their formulations.

Development and validation of LC-MS/MS method for simultaneous determination of sofosbuvir and daclatasvir in human Plasma: Application to pharmacokinetic study

A simple and highly sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) bioanalytical method was developed and fully validated for the first time for the simultaneous determination of newly discovered antiviral drugs, namely sofosbuvir (SOF) and daclatasvir (DAC) in human plasma. Tadalafil (TAD) was used as internal standard (IS). SOF, DAC and TAD (IS) were extracted from plasma using liquid-liquid extraction technique with methyl tert-butyl ether. The chromatographic separation was carried out using ZorbaxSB-C₁₈ column (4.6 × 50 mm,5 μm) and 5 mm ammonium formate buffer (pH 3.5)-acetonitrile (50:50, v/v) as mobile phase in an isocratic elution mode pumped at a flow rate 0.7 mL min^-1 . The quantitation was performed on API4500 triple quadrupole tandem mass spectrometer with positive electrospray ionization interface in multiple reaction monitoring mode. Validation was applied according to US Food and Drug Administration guidelines for bio-analytical methodswith respect to linearity, precision, accuracy, selectivity, carry-over, stability and dilution integrity. Linearity was obtained over concentration ranges of 0.3-3000 and 3-3000 ng mL^-1 for SOF and DAC, respectively, by applying a weighted least-squares linear regression method (1/x² ). The proposed method could be applied successfully in bioequivalence and/or clinical studies for therapeutic drug monitoring of patients undergoing dual combination therapy as the latter combination proved more efficacious and powerful tool for the complete treatment of hepatitis C genotype 3 within 16 weeks. The suggested method has been applied successfully to pharmacokinetic studies with excellent assay ruggedness and reproducibility.

Selective and sensitive spectrofluorimetric quantification of velpatasvir in presence of sofosbuvir. Application to their co-formulated tablet

A new sensitive, rapid and simple spectrofluorimetric method was utilized for the assessment of velpatasvir (VPS) in its bulk form as well as in its combined tablet with sofosbovir (SFV). The technique relies on measuring the native fluorescence of VPS in methanol at 385 nm and 400 nm after excitation at 295 nm. The fluorescence–concentration plots were rectilinear through the range of 2.0–20.0 ng mL⁻¹ at both emission maxima with lower detection limits of 0.146 ng mL⁻¹ and 0.378 ng mL⁻¹, and lower quantification limits of 0.444 ng mL⁻¹ and 1.147 ng mL⁻¹ at 385 nm and 400 nm, respectively. The proposed method was appropriately used for the analysis of VPS in its commercial tablet formulation and the results were in good agreement with those achieved with the applied comparison method.

A new sensitive, rapid and simple spectrofluorimetric method was utilized for the assessment of velpatasvir (VPS) in its bulk form as well as in its combined tablet with sofosbovir (SFV).

Potential of RP-UHPLC-DAD-MS for the qualitative and quantitative analysis of sofosbuvir in film coated tablets and profiling degradants

Sofosbuvir is one of the new direct-acting antiviral drugs against hepatitis C virus (HCV) infection. This drug has recently been launched into the market, and generic versions of the medication are expected to be produced by local drug producers in some countries. Therefore, new methods are required to control sofosbuvir in pharmaceuticals. In the present study, a new method based on reversed phase (RP)-ultra-high performance liquid chromatography (UHPLC) coupled to diode array detection (DAD) and mass spectrometry (MS) was developed to facilitate the qualitative and quantitative analysis of sofosbuvir in film coated tablets. A wavelength of 260 nm was selected to perform a cost-effective quantification and the method showed adequate linearity, with an R2 value of 0.9998, and acceptable values of accuracy (75%-102%) and precision (residual standard deviation <5%). The detection and quantification limits were 0.07 μg/mL and 0.36 μg/mL, respectively. Furthermore, the use of high-resolution MS enabled us to ensure the specificity, check impurities and better sensitivity. Therefore, this methodology promises to be suitable not only for the routine analysis of sofosbuvir in pharmaceutical dosage forms, but also for potential degradants.