Development of Impurity Profiling Methods Using Modern Analytical Techniques

Quantification of oxaliplatin- and ioversol-related compounds in pharmaceutical formulations using novel HPLC-ICP-MS methods

PURPOSE

Accurate quantifying of drug-related compounds in medicines is vital for safety. Commonly used structure-dependent methods rely on analytical standards. High-performance liquid chromatography coupled with inductively coupled plasma-mass spectrometry (HPLC-ICP-MS) offers a promising solution, being structure-independent and not requiring standards. In this study, we aim to develop HPLC-ICP-MS methods for the determination of related compounds in oxaliplatin and ioversol injections.

RESULTS

The target analytes were eluted on an XSelect HSS T3 column (2.1 ×50 mm, 5 µm). Specifically, oxaliplatin injection was eluted isocracially for 3.5 min, and ioversol injection was eluted gradient with a total chromatographic run time of 12 min. The measurements to determine dihydroxy oxaliplatin-Pt(IV) and two related compounds of ioversol were performed by monitoring at m/z for 195Pt and 127I, respectively. The calibration curves were established over the range of 0.05-1 μM for Pt and 0.3-15 μM for I with the correlation coefficients greater than 0.999. The limits of quantification were 0.004 μM for dihydroxy oxaliplatin-Pt(IV), 0.022 μM for ioversol related compound A and 0.026 μM for ioversol related compound B. The accuracy (recovery between 93-105%) and precision (repeatability ≤ 6.1% RSD) were fit-for-purpose for dihydroxy oxaliplatin-Pt(IV), and the accuracy (recovery between 95-107%) and precision (repeatability ≤ 3.9% RSD) were also fit-for-purpose for both ioversol related compound A and ioversol related compound B.

CONCLUSION

The quantitation accuracy of HPLC-ICP-MS closely matched that of the standard HPLC-UV approach. HPLC-ICP-MS can be used as a complementary analytical technique for quantitative determination of drug-related compounds.

A critical assessment on stability behaviour of Vorinostat using LC-MS-QTOF with H/D exchange and NMR

Vorinostat is the first USFDA-approved HDAC inhibitor for the treatment of cutaneous t-cell lymphoma. Vorinostat was exposed to ICH-recommended hydrolytic (acid, base, and neutral), oxidative, thermal, and photolytic stress conditions to understand the degradation behaviour. A Stability indicating LC method was developed and validated for separating and identifying forced degradation products. Under different stress conditions, six degradants were identified and characterized by LC-HRMS, MS/MS, and hydrogen-deuterium exchange mass studies. Vorinostat was found to be highly susceptible to the acidic and basic environment. In contrast, the drug substance was stable in the solid state under thermal and photolytic conditions whereas, it was found moderately stable when photolytic stress was provided to dissolved state of Vorinostat in acetonitrile-water. The degradants were identified as 7-amino-N-phenylheptanamide, 8-hydrazineyl-8-oxo-N-phenyloctanamide, 8-oxo-8-(phenylamino)octanoic acid, 8-oxo-8-(2-(7-oxo-7-(phenylamino)heptyl)hydrazineyl)-N-phenyloctanamide, 8,8'-(1-hydroxyhydrazine-1,2-diyl)bis(8-oxo-N-phenyloctanamide), and N1-((8-oxo-8-(phenylamino)octanoyl)oxy)-N8-phenyloctanediamide. The mechanistic explanation for the formation of each degradant in stability conditions has also been derived. The major degradants were also isolated/synthesized and characterized through 1H NMR for preparing impurity standards. Additionally, in-silico toxicity of the degradants was predicted in comparison to the drug, to identify whether any degradant has any specific type of toxicity and requires special focus to set specification limits during formulation development. The predicted toxicity indicated that the degradants have similar safety profile as that of the drug and specification can be set as per general impurity guideline.

Automated High-Throughput Matrix Assisted Laser Desorption Ionization Mass Spectrometry Methodology for Formulation Assessment of Polyethylene-Glycol-Conjugated Cytokine Proteins

Biological therapeutics are major contributors to the pharmaceutical pipeline and continue to grow in sales and scope. Additionally, the field's understanding of cancer biology has advanced such that biopharmaceuticals can harness the power of the immune system for oncology treatments. Several of these novel therapeutics are engineered versions of naturally occurring proteins designed to improve therapeutic properties including potency, target engagement and half-life extension. Cytokines, such as interferons and interleukins, are a broad class of signaling proteins which modulate the body's immune response; engineered cytokines have entered the clinic as promising new immuno-oncology therapies. While these therapies hold great promise, their additional structural complexity introduces analytical challenges, and traditional analytical platforms may be ill-suited to effectively assess product development risks. Further, the pharmaceutical industry relies on streamlining approaches for high-throughput experimentation to achieve speed and efficiency for the discovery and development of new modalities. These demands necessitate the use of state-of-the-art techniques to rapidly characterize these new modalities and guide process development and optimization. Matrix Assisted Laser Desorption Ionization Mass Spectrometry (MALDI-MS) is a rapid, sensitive and automatable technique amenable for high-throughput analysis of proteins. In this work, we have developed an automated MALDI-MS platform to prepare, acquire and analyze molecular degradation in engineered PEGylated cytokines formulation samples. This orthogonal technique integrated seamlessly with current developability risk assessment workflows, ultimately enabling selection of a final formulation strategy for clinical development.

Strategy of Choosing Templates in Molecular Imprinting to Expand the Recognition Width for Family-Selectivity

The class-selective molecular-imprinted polymers (MIPs) have shown the recognition ability to multiple targeted molecules through using one or multiple templates. However, choosing the right templates, the core problem, still lacks a systemic guide and decision-making. In this work, we propose a strategy of selecting templates through expanding the recognition width for the improvement of class-selectivity. First, three families of genotoxic impurity (GTI) were selected as model objects, and the spatial size and binding energy of each GTI-monomer complexes were obtained and compared by computational simulation. The two indexes of energy width (W_E) and size width (W_L) were introduced to compare the similarity and differences on the two recognition factors, binding strength and spatial size, among these GTIs in each family. Through shortening the width to increase similarity on binding energy and size, the dual templates in the aromatic amines (AI) family and sulfonic acid esters (SI) family were successfully selected. Correspondingly, the prepared dual-template MIPs in the two GTI families can simultaneously recognize all the GTIs comparing with that of single template MIP, respectively. Meanwhile, through comparing the adsorption capacity of the selected template and its analogues in one GTI family, the recognition efficiency of the dual-template MIPs was higher than that of the single-template MIP. This indicates that though using the selected right templates, the higher class-selectivity and the larger recognition width can be realized. Thus, this work can solve the problem of blind template selection, and provide the useful theoretical guidance for designing family-selective molecular imprinting.

Hyphenated liquid chromatography - diode array detection - charged aerosol detection - high resolution - multistage mass spectrometry with online hydrogen/deuterium exchange: One stop solution for pharmaceutical impurity profiling

Hyphenation of different analytical techniques has always been advantageous in structural characterization as it saves time, money and resources. In the pharmaceutical sector, chromatography-based impurity profiling, including identification, characterization, and quantification in drug substances or finished products, is of utmost importance to comply with quality, patient safety and regulatory requirements. These impurities are monitored using LC-UV/DAD and identified and/or characterized using HRMS and MS/MS. LC analysis usually yields the area percent purity of the targeted peak, however, this is not sufficient for pharmaceutical purposes; where the regulatory requirement is to report impurities in percent weight by weight. Unfortunately, the non-availability of impurity standards and relative response factors at an early stage of drug development, risks the product quality due to the inability of the method to differentiate percent purity, and percent weight by weight. Hence, there is a need for a distinctive way of determining the relative response factor. In the current study, a unique hyphenation has been employed by integrating LC with DAD, CAD, and HRMSⁿ with hydrogen-deuterium exchange. The LC flow, post-DAD detection has been diverted to CAD with an inverse gradient for relative response factor determination and MS Orbitrap for exact mass, and MSⁿ fragmentation. A separate infusion pump has been incorporated to infuse D₂O on a need basis, which can perform partial hydrogen deuterium exchange for determining the number of labile hydrogens in the impurity structure. This hyphenation has been validated with four model compounds and a total of nineteen chromatographic peaks. The technique provides ample information for their qualitative analysis along with percent weight-by-weight values, which fulfils the regulatory requirements and can be used as one-stop solution for impurity profiling.

Identification, synthesis and characterization of avanafil process impurities and determination by UPLC

Avanafil is a phosphodiesterase type 5 inhibitor which is used to treat erectile dysfunction in men. The process-related impurities of avanafil were investigated, and four kinds of impurities in several laboratory batches with a content of 0.29-1.63% were detected by the newly developed gradient ultra-high performance liquid chromatography (UPLC). Based on the synthesis route and UPLC-MS research, the impurities are inferred as Imp-A, Imp-B, Imp-C and Imp-D. The structures of the impurities were inferred from LC-MS studies and confirmed by synthesis, followed by spectroscopic characterization such as NMR and mass spectrometry. Especially, the synthesis of Imp-D is firstly reported. The drug-related substances can be separated well by efficient and selective ultra-high performance liquid chromatography on a Waters ACQUITY HSS C18 (50 × 2.1 mm, particle size 1.8 μm) column at 35 °C, with the mobile phase consisting of ammonium formate (20 mM) and acetonitrile, and the detection at 239 nm with a DAD detector. The method was validated in terms of specificity, linearity, precision, accuracy and sensitivity, and satisfactory results were obtained. The results indicated this developed UPLC method for avanafil and the proposed synthesis mechanism can be used for quality control purposes as required by regulatory agencies to ensure the safety and efficacy of the product.

An Overview of Advances in the Chromatography of Drugs Impurity Profiling

A systematic literature survey published in several journals of pharmaceutical chemistry and of chromatography used to analyze impurities for most of the drugs that have been reviewed. This article covers the period from 2016 to 2020, in which almost of chromatographic techniques have been used for drug impurity analysis. These chromatography techniques are important in the analysis and description of drug impurities. Moreover, some recent developments in forced impurity profiling have been discussed, such as buffer solutions, mobile phase, columns, elution modes, and detectors are highlighted in drugs used for the study. This primarily focuses on thorough updating of different analytical methods which include hyphenated techniques for detecting and quantifying impurity and degradation levels in various pharmaceutical matrices.

Simultaneous determination of multi-class active pharmaceutical ingredients by UHPLC-HRMS

In this work, a UHPLC-HRMS method using a quadrupole-orbitrap mass spectrometer has been developed for the detection and quantification of 47 compounds. These compounds include a range of chemical structures and properties and are popularly referred to as active pharmaceutical ingredients (API). The APIs selected have historically been incorporated into a variety of products commonly marketed towards acne, hair loss, male erectile dysfunction, and skin whitening. A fast ultrasound-assisted extraction (UAE) procedure without sample cleanup was developed and a high-resolution product ion spectral library was generated for compound verification in complex matrices. Collision energies were optimized for all analytes to overcome the limitations by applying stepped collision energies, such as insufficient fragmentation and excessive fragmentation without molecular ion information. Higher HRMS2 spectra matching scores (0.6 or above) were obtained for the analytes in the tested complex matrices. Eleven representative stable isotopically labeled API analogs were used as internal standards to compensate for the influence of complex matrices, such as shampoo and creams, and as an instrument quality control. One-hundred products with complex matrices were analyzed using the validated UHPLC-HRMS method. Eight APIs (ketoconazole, hydroquinone, salicylic acid, benzocaine, progesterone, azelaic acid, lidocaine, and minoxidil) were identified in 26 out of 100 products ranging from 103 μg/g to 156,000 μg/g.

Stability Indicating Methods for Determination of Third Generation Antiepileptic Drugs and Their Related Substances

The third generation of antiepileptic drugs that have been approved by international regulatory agencies between 2007 and 2018 include rufinamide, stiripentol, eslicarbazepine acetate, lacosamide, perampanel, brivaracetam and everolimus. As part of demonstrating their safety profile, stability indicating methods are developed to monitor these drugs and their impurities. In this context, this review describe some characteristics, impurities and the stability indicating methods used for the determination of these drugs and the presence of their related substances. Through a search in official compendia and scientific articles, fifty-six analytical methodologies were identified up to October 2020. The methodologies were developed using techniques of HPLC, UPLC, HPTLC, GC and UV/Vis spectrophotometry. A majority of the methods (∼70%) employed HPLC-UV. A number of these antiepileptic drugs were found to have had a small number of studies related to their stability and for the detection of impurities. The presentation of the current level of research on third generation antiepileptic drugs highlights the need for new stability and safety studies that are necessary to develop new pharmaceutical products containing these drugs.

Ezetimibe: A Review of Analytical Methods for the Drug Substance, Pharmaceutical Formulations and Biological Matrices

Ezetimibe (EZM) is a selective inhibitor of the sterol transporter Niemann-Pick C1-Like 1 in the small intestine used as an adjunctive therapy to lower cholesterol levels in cases of hyperlipidemia. The goal of this work was to summarize the main physical-chemical, pharmacological and pharmacokinetic characteristics of EZM, as well as to describe the main analytical methodologies for the quantification of the drug. Methods described in the United States Pharmacopeia for EZM raw material and tablets were also presented. The drug has a large number of process-related impurities and degradation products and needs strict quality control of its impurities. Specific chiral methods for the evaluation of its chiral impurities are also a need for EZM. The main advantages and disadvantages of the compiled analytical methods were presented, as well as the limits of detection and quantitation. The fastest and most efficient methods were highlighted. Most methods for analyzing EZM used C₈ or C₁₈ stationary phases in gradient mode with binary mobile phases containing acetonitrile and an acidic buffer solution with ultraviolet detection. For analysis of EZM in biological matrices, liquid chromatography-tandem mass spectrometry is generally employed using electron spray ionization in negative ionization mode using multiple reaction monitoring. Different methods in the literature evaluate a large number of impurities for EZM, however new stability-indicating high-performance liquid chromatography methods for the drug are still needed.

Separation and characterization of impurity P in azithromycin product

Azithromycin is a macrolide antibiotic which is used to treat a wide variety of bacterial infections. Impurity P is one of the impurities in azithromycin product, which is registered in Pharmacopoeias of Europe and USA. However, to date, the structure of this impurity has still not been elucidated. In this work, we separated impurity P from azithromycin product using preparative chromatography and successfully identified its chemical structure using multiple analytical techniques. First, high-resolution ion trap-time-of-flight mass spectrometry (IT-TOF MS) was used to determine the accurate molecular mass ([M+H]⁺m/z 777.5121) and the chemical formula (C₃₉H₇₂N₂O₁₃) of the impurity. Second, Fourier transforming infrared spectroscopy (FT-IR), ultraviolet-visible absorption spectroscopy (UV-vis) and tandem mass spectrometry (MS/MS) analyses were performed to probe into the key functional groups of the impurity to aid the NMR analysis. Finally, the structure of the impurity was successfully resolved using multidimensional NMR. In addition, a mechanism for the formation of this impurity was proposed.

Capillary electrophoretic methods for quality control analyses of pharmaceuticals: A review

Capillary electrophoresis represents a promising technique in the field of pharmaceutical analysis. The presented review provides a summary of capillary electrophoretic methods suitable for routine quality control analyses of small molecule drugs published since 2015. In total, more than 80 discussed methods are sorted into three main sections according to the applied electroseparation modes (capillary zone electrophoresis, electrokinetic chromatography, and micellar, microemulsion, and liposome-electrokinetic chromatography) and further subsections according to the applied detection techniques (UV, capacitively coupled contactless conductivity detection, and mass spectrometry). Key parameters of the procedures are summarized in four concise tables. The presented applications cover analyses of active pharmaceutical ingredients and their related substances such as degradation products or enantiomeric impurities. The contribution of reported results to the current knowledge of separation science and general aspects of the practical applications of capillary electrophoretic methods are also discussed.

Analytical methodologies for determination of methotrexate and its metabolites in pharmaceutical, biological and environmental samples

Methotrexate (MTX) is a folate antagonist drug used for several diseases, such as cancers, various malignancies, rheumatoid arthritis (RA) and inflammatory bowel disease. Due to its structural features, including the presence of two carboxylic acid groups and its low native fluorescence, there are some challenges to develop analytical methods for its determination. MTX is metabolized to 7-hydroxymethotrexate (7-OH-MTX), 2,4-diamino-N10-methylpteroic acid (DAMPA), and the active MTX polyglutamates (MTXPGs) in the liver, intestine, and red blood cells (RBCs), respectively. Additionally, the drug has a narrow therapeutic range; hence, its therapeutic drug monitoring (TDM) is necessary to regulate the pharmacokinetics of the drug and to decrease the risk of toxicity. Due to environmental toxicity of MTX; its sensitive, fast and low cost determination in workplace environments is of great interest. A large number of methodologies including high performance liquid chromatography equipped with UV-visible, fluorescence, or electrochemical detection, liquid chromatography-mass spectroscopy, capillary electrophoresis, UV-visible spectrophotometry, and electrochemical methods have been developed for the quantitation of MTX and its metabolites in pharmaceutical, biological, and environmental samples. This paper will attempt to review several published methodologies and the instrumental conditions, which have been applied to measure MTX and its metabolites within the last decade.

Characterization of an Unknown Impurity in Glucosamine Sulfate Sodium Chloride by HPLC-Q-TOF MS and NMR

Background:

Glucosamine sulfate sodium chloride (glucosamine-SP) is mainly used for the treatment of osteoarthritis. During quality control of glucosamine-SP capsules, an unknown impurity was detected. Another unknown degradation product was generated together with above-mentioned impurity in heat condition.

Objective:

The study aimed to characterize an unknown impurity in glucosamine-SP capsules.

Methods:

A new volatile HPLC method compatible with mass spectrometry detection was set up. An amino column at 35 °C with a mobile phase consisting of water and acetonitrile (20: 80, v/v) was used at a flow rate of 1.5 ml/min at 297 nm. High-performance liquid chromatography quadrupole time-offlight mass spectrometry (HPLC-Q-TOF MS) was used to identify the impurity with the electrospray ionization (ESI) source in the positive ionization mode.

Results:

The results of HPLC-Q-TOF MS analysis indicated that the protonated molecule ions [M + H]+ of the unknown impurity and the novel degradation product were both at m/z 287. Preparative LC method was put into practice with a Prep-C18 column with a mobile phase consisting of water and acetonitrile (99: 1, v/v) at a flow rate of 20.0 ml/min at 297 nm. The assignment of the 1D and 2D NMR signals was performed for the unknown impurity. In addition, the formation of impurities was also studied.

Conclusion:

An unknown impurity and a degradation product in glucosamine-SP capsules were characterized. They were assigned as (1R, 2S, 3R)-1-(5-((S, E)-3, 4-dihydroxybut-1-en-1-yl) pyrazin-2-yl) butane-1, 2, 3, 4-tetraol and (1R, 2S, 3R)-1-(5-((S, Z)-3, 4-dihydroxybut-1-en-1-yl) pyrazin-2-yl) butane- 1, 2, 3, 4-tetraol.

In vitro toxicity assessment of rivaroxaban degradation products and kinetic evaluation to decay process

Degradation kinetics of oral anticoagulant rivaroxaban (RIV) was assessed in acid and alkaline media and while exposed to UVC radiation. Among all stress conditions tested, kinetic degradation process was better described by a zero-order model. A stability indicating method was validated for the analysis of the anticoagulant RIV in tablets by high-performance liquid chromatography. Robustness was evaluated with a two-level Plackett-Burman experimental design. The effect of acute exposition of the human hepatoblastoma HepG2 cell line to RIV stressed samples (100 and 500 µM) was assessed through in vitro toxicity tests. MTT reduction, neutral red uptake, mitochondrial membrane potential, and low molecular weight DNA diffusion assays were employed for cytotoxicity evaluation (5×10⁴ cells/well). The genotoxic potential was assessed by comet assay (2×10⁴ cells/well). Acute toxicity to HepG2 cells was assessed after 24 h incubation with sample solutions, for each test. A direct relationship between the increased amount of alkaline degradation products and higher cytotoxic potential was found. Results obtained by viability assay investigations support the concerns on risks associated with acute toxicity and genotoxicity of pharmaceutical samples containing degradation products as impurities.

Composites Based on Conducting Polymers and Carbon Nanomaterials for Heavy Metal Ion Sensing (Review)

Current review signifies recent trends and challenges in the development of electrochemical sensors based on organic conducting polymers (OCPs), carbon nanotubes (CNTs) and their composites for the determination of trace heavy metal ions in water are reviewed. OCPs and CNTs have some suitable properties, such as good electrical, mechanical, chemical and structural properties as well as environmental stability, etc. However, some of these materials still have significant limitations toward selective and sensitive detection of trace heavy metal ions. To overcome the limitations of these individual materials, OCPs/CNTs composites were developed. Application of OCPs/CNTs composite and their novel properties for the adsorption and detection of heavy metal ions outlined and discussed in this review.

Characterization of impurities in sodium cromoglycate drug substance and eye drops using LC-ESI-ion trap MS and LC-ESI-QTOF MS

As requested by regulatory authorities, impurity profiling is an important issue of quality control. In this work, a simple and sensitive liquid chromatographic (LC) method compatible with mass spectrometry (MS) was developed to study related substances and degradation products in sodium cromoglycate drug substance and eye drops. The method used a Sunfire column (4.6mm×150mm, 3.5μm). Mobile phase A consisted of 10mM ammonium formate and mobile phase B was acetonitrile. Linear gradient elution with a post-run time of 8min was performed as follows: 0-30min, 3% B to 50% B; 30-35min, 50% B. The flow rate was set at 1.0mL/min. Degradation experiments were performed to check the stability indicating properties of the developed method. Based on MSⁿ spectral data and exact mass measurements, the chemical structures of 2 unknown impurities and 6 unknown degradation products were characterized, including impurity C listed in the European Pharmacopoeia as unknown structure. In addition, a plausible mechanism for the formation of the degradation products was also proposed.