Bioanalytical method development and validation using incurred samples--simultaneous quantitation of ramipril and ramiprilat in human EDTA plasma by LC-MS/MS

Sample pooling and incurred samples improve analytical throughput and quality control of lipophilic phycotoxins screening in bivalve mollusks

Lipophilic marine biotoxins (LMBs) are one of the main risks associated with the consumption of mussels and oysters. Sanitary and analytical control programs are developed to detect the occurrence of these toxins in seafood before they reach toxic levels. To ensure quick results, methods must be easy and fast to perform. In this work, we demonstrated that incurred samples were a viable alternative to validation and internal quality control studies for the analysis of LMBs in bivalve mollusks. These samples were used to optimize, validate, and monitor a simple and fast ultrasound-assisted extraction (UAE) procedure. An internal quality control material containing okadaic acid (227 ± 46 µg kg-1) was produced and characterized. This material had its homogeneity and stability verified and was included as a quality control in all batches of analytical routine. Besides, a sample pooling protocol for extracts analysis was developed, based on tests for COVID-19. Up to 10 samples could be analyzed simultaneously, reducing the instrumental time of analysis by up to 80%. The UAE and sample pooling approaches were then applied to more than 450 samples, of which at least 100 were positive for the okadaic acid group of toxins.

Metabolite profiling of arginase inhibitor activity guided fraction of Ficus religiosa leaves by LC-HRMS

Cardiovascular disease is one of the major causes of deaths worldwide. Increased arginase activity is associated with cardiovascular disease. The literature shows that plants are a good source of arginase inhibitors. Hence in the present work arginase inhibitor activity is studied from Ficus religiosa leaves. A fine powder of F. religiosa leaves was serially extracted in various solvents, viz. hexane, chloroform, ethyl acetate and methanol. Out of those four solvent extracts, the one showing highest arginase inhibitor activity was loaded onto the column for further fractionation. Among the collected fractions, the one showing the highest activity was subjected to identification of metabolites by using LC-HRMS. Total compounds including acipimox, edoxudine, levulinic acid, hydroxyhydroquinone, ramiprilglucuronide, berberine, antimycin A, swietenine and some short peptides were identified from the fraction showing the highest arginase inhibitory activity. Identification of these metabolites from F. religiosa and their biological importance may help to promote its use as medicinal plant. Further purification and characterization of therapeutically novel molecules will be the subject of future work.

Challenges and recommendations in developing LC–MS/MS bioanalytical assays of labile glucuronides and parent compounds in the presence of glucuronide metabolites

Glucuronides, especially acyl glucuronides, were often found to be unstable in vitro and in vivo. Acyl glucuronide metabolites can convert back to the parent drugs at physiological pH through hydrolysis. Glucuronides can also undergo in-source fragmentation during MS ionization to form the same ions as those of the parent compounds, which could cause interference to the analysis of the parent compounds. All of these may cause significant challenges in developing LC–MS/MS bioanalytical assays of labile glucuronides or parent compounds in the presence of glucuronide metabolites. In this manuscript, we will discuss these challenges and summarize recommended strategies and practices for fast and efficient method development. Critical considerations in assay development will also be discussed.

The importance of evaluating the chemical structures and strategies to avoid pitfalls in quantitative bioanalysis

Quantitative bioanalytical data are crucial in pharmaceutical research and development, allowing project teams to make informed scientific decisions on the progression of candidate molecules to medicines. Many challenges are often encountered during the bioanalysis of drugs in biological matrices which require resolution in a timely manner. In this publication, guidance is provided to bioanalytical scientists on how to identify potential problems before they become an obstacle for the drug development and to share our experiences dealing some of most common problems encountered in the bioanalytical laboratory. Relevant topics in bioanalysis such as stabilization approaches for glucuronides (Acyl and N-); prodrugs (phosphate and esters), amides, amines, N-oxides; bioanalysis of light sensitive molecules, halogenated drugs and lactones are discussed in this publication.

Self-initiated and concentration-dependent degradation of tetracaine in neat standard solutions: A trouble-shooting story

This paper presents the trouble-shooting for a very unusual stability case. Tetracaine was found unstable in neat solutions only at high concentrations, but not at low concentrations. Moreover, its stable-isotope labeled internal standard did not show similar behavior. A series of trouble-shooting experiments were conducted to uncover the root cause. Some generally applicable precautions/insights can be drawn from this investigation to avoid potential stability issues during bioanalytical method development and validation.

A simple, effective approach for rapid development of high-throughput and reliable LC-MS/MS bioanalytical assays

BACKGROUND

Rapidly developing LC-MS/MS assays with high-throughput and quality are challenging yet desired. Methodology & results: A simple method development approach was reported and demonstrated with the quantitative bioanalysis of BMS-984478, a hepatitis C virus nonstructural protein 5A inhibitor. An accurate, precise and robust LC-MS/MS method for the quantitation of BMS-984478 in rat and monkey plasma was developed and validated. Incurred sample reanalysis evaluation passed with 100% of samples meeting the acceptance criteria. The validated assay was successfully applied in toxicology studies without any failed runs.

CONCLUSION

The approach was successfully applied to the bioanalysis of BMS-984478 in toxicology and clinical studies. This approach was shown to be effective and reliable in speeding the development of high-throughput and reliable LC-MS/MS assays.

Quantification of dabigatran and indirect quantification of dabigatran acylglucuronides in human plasma by LC–MS/MS

Background: An assay for the quantification of dabigatran and its active metabolites, dabigatran acylglucuronides, has not previously been described in detail. Results: For the quantification of total dabigatran concentration (free dabigatran and acylglucuronides), samples were subjected to alkaline hydrolysis. For the quantification of free dabigatran, samples were acidified with ammonium formate. Following acetonitrile protein precipitation, the samples were analyzed by LC–MS/MS using gradient elution to ensure separation of dabigatran from dabigatran acylglucuronides. Mean recoveries ≥98% were achieved. The assay was validated over the range 2.5–1000 ng/ml dabigatran, imprecision was <9% CV (<15% at LLOQ) and accuracy was 101–114%. Conclusion: An assay for dabigatran with indirect quantification of dabigatran acylglucuronides in plasma was developed, validated and applied.

Simultaneous Determination and Pharmacokinetic Study of Losartan, Losartan Carboxylic Acid, Ramipril, Ramiprilat, and Hydrochlorothiazide in Rat Plasma by a Liquid Chromatography/Tandem Mass Spectrometry Method

The monitoring of the plasmatic concentrations of cardiovascular drugs is crucial for understanding their pharmacokinetics and pharmacodynamics. A simple, sensitive, specific, and high-throughput liquid chromatography/tandem mass spectrometry (LC–MS/MS) method was developed and validated for the simultaneous estimation and pharmacokinetic study of losartan (LOS), losartan carboxylic acid (LCA), ramipril (RAM), ramiprilate (RPT), and hydrochlorothiazide (HCZ) in rat plasma using irbesartan (IBS) and metolazone (MET) as internal standards (ISs). After solid phase extraction (SPE), analytes and ISs were separated on an Agilent Poroshell 120, EC-C18 (50 mm × 4.6 mm, i.d., 2.7 μm) column with a mobile phase consisting of methanol/water (85:15, v/v) containing 5 mmol/L ammonium formate and 0.1% formic acid at a flow rate of 0.4 mL/min. The precursor → product ion transitions for the analytes and ISs were monitored on a triple quadrupole mass spectrometer, operating in the multiple reaction monitoring (MRM) mode and switching the electrospray ionization (ESI) mode during chromatography from positive (to detect LOS, LCA, RAM, RPT, and IBS) to negative (to detect HCZ and MET). The method was validated as per the FDA guidelines and it exhibited sufficient specificity, accuracy, and precision. The method was found to be linear in the range of 3–3000 ng/mL for LOS and LCA, 0.1–200 ng/mL for RAM and RPT, and 1–1500 ng/mL for HCZ. The described method was successfully applied to the preclinical pharmacokinetic study of analytes after oral administration of a mixture of LOS (10 mg/kg), RAM (1 mg/kg), and HCZ (2.5 mg/kg) in rats.

Development and validation of bioanalytical method for simultaneous estimation of ramipril and hydrochlorothiazide in human plasma using liquid chromatography-tandem mass spectrometry

The present study describes a novel liquid chromatographic-tandem mass spectrometric (LC-MS/MS) method for the simultaneous estimation of ramipril (RAM) and hydrochlorothiazide (HCTZ) in human plasma using liquid-liquid extraction technique. This method made use of electrospray ionization in positive mode for RAM and in negative mode for HCTZ using triple quadrupole mass spectrometry where carbamazepine was used as an internal standard (IS). Analytes were recovered by methyl tertiary butyl ether:dichloromethane (85:15) subsequently separated on an Enable C18 G column (150 mm × 4.6 mm, 5 μm) using methanol:0.1% formic acid in water (85:15) as a mobile phase, at a flow rate of 0.5 mL/min. Quantification of RAM, HCTZ and IS was performed using multi-reaction monitoring mode (MRM) where transition of m/z 417.2→234.1 (RAM) and 237.0→194.0 (IS) in positive mode and 296.1→205.0 for HCTZ in negative mode. The calibration curve was linear (r(2)>0.99) over the concentration range of 2-170 ng/mL for RAM and 8-680 ng/mL for HCTZ. The intra-day and inter-day precisions were <15% and the accuracy was all within ±15% (at LLOQ level ±20%). Additionally, the LC-MS/MS method was fully validated for all the other parameters such as selectivity, matrix effect, recovery and stability as well. In conclusion, the findings of the present study revealed the selectivity and sensitivity of this method for the simultaneous estimation of RAM and HCTZ in human plasma.

Strategies for ascertaining the interference of phase II metabolites co-eluting with parent compounds using LC-MS/MS

LC-MS/MS is currently the most selective and efficient tool for the quantitative analysis of drugs and metabolites in the pharmaceutical industry and in clinical assays. However, phase II metabolites sometimes negatively affect the selectivity and efficiency of the LC-MS/MS method, especially for the metabolites that possess similar physicochemical characteristics and generate the same precursor ions as their parent compounds due to the in-source collision-induced dissociation during the ionization process. This paper proposes some strategies for examining co-eluting metabolites existing in real samples, and further assuring whether these metabolites could affect the selectivity and accuracy of the analytical methods. Strategies using precursor-ion scans and product-ion scans were applied in this study. An example drug, namely, caffeic acid phenethyl ester, which can generate many endogenous phase II metabolites, was selected to conduct this work. These metabolites, generated during the in vivo metabolic processes, can be in-source-dissociated to the precursor ions of their parent compounds. If these metabolites are not separated from their parent compounds, the quantification of the target analytes (parent compounds) would be influenced. Some metabolites were eluted closely to caffeic acid phenethyl ester on LC columns, although long columns and relatively long elution programs were used. The strategies can be utilized in quantitative methodologies that apply LC-MS/MS to assure the performance of selectivity, thus enhancing the reliability of the experimental data.

Incurred sample reanalysis: different evaluation approaches on data obtained for spironolactone and its active metabolite canrenone

Background: The inherent reproducibility of a bioanalytical approach is usually sustained through incurred sample reanalysis (ISR). Questions relating to the number of ISRs, the right moment for performing reanalysis, the way of performing an appropriate statistical refinement of experimental data and actions to be taken in the case of failure are frequently raised. Results: Data resulting from ISR following a bioequivalence study for spironolactone formulations are discussed. Reanalysis of samples was carried out twice: immediately after the end of the study and after a period that overcame the long-term stability study achieved during method validation. The Bland–Altman approach was used to assess experimental results. ISR was successful over the short reanalysis period for both compounds. Data produced through reanalysis after the long-term period indicated a systematic positive bias for the metabolite canrenone (although results supported reproducibility). The results obtained for spironolactone were affected by a strong negative systematic bias and failed to support reproducibility. The explanation deals with the continuous conversion of spironolactone to canrenone in plasma samples. However, reproducibility of the method may be sustained by comparing original and repeated differences between concentration values in samples by means of a paired t-test, Wilcoxon sign rank-sum test and linear regression. Conclusions: Different statistical approaches for making data comparisons are discussed and may be successfully applied during reanalysis of samples from a bioequivalence study. Results of the evaluations may differ in accordance with the statistical procedure being applied, thus a definitive conclusion requires consideration of all specific experimental circumstances arising during production of the processed data.

Impact of methylation of acyl glucuronide metabolites on incurred sample reanalysis evaluation: ramiprilat case study

Background: Reanalysis of incurred samples showed that the bioanalytical method for the quantification of ramipril and ramiprilat was generating irreproducible results for ramiprilat. Results: An additional peak interfering with ramiprilat was observed in the incurred samples but not in the calibrant and quality control samples. A similar interference was detected for ramipril, but it was chromatographically separated. Interferences were produced during sample preparation, which involves strong cation exchanger cartridges. The interfering products corresponded to the methylation of ramipril and ramiprilat glucuronide. Conclusion: Following this discovery, a reproducible method was developed and successfully validated for ramipril and ramiprilat. Additional stability tests were performed in the presence of glucuronide and diketopiperazine metabolites of ramipril and ramiprilat to demonstrate the method specificity.

Incurred sample reanalysis (ISR): a decisive tool in bioanalytical research

The AAPS Workshop 2008 on Current Topics in GLP Bioanalysis: Assay Reproducibility for Incurred Samples was the defining moment in establishing incurred sample reanalysis (ISR) as a mandatory exercise in demonstrating assay reproducibility using incurred (study) samples. The importance of ISR can be envisaged from its role in clinical as well as non-clinical studies. Incurred samples can differ significantly in their composition when compared with the calibration standards and quality control samples that are used to validate the developed method. The present article attempts to summarize five troubleshooting cases encountered in the analyses of incurred samples for bioanalytical methods developed in our laboratory for mesalamine, hydrochlorothiazide, clopidogrel, sildenafil and rabeprazole. The issues identified were related to: sample inhomogeneity, sample processing error, impact of buffer pH during sample preparation, instability of metabolite and change in laboratory environment. The steps taken to trace and correct these incidents are discussed with adequate data. These examples will further broaden the scope and emphasize the significance of ISR. We believe this investigation will help to develop more reliable and efficient bioanalytical methods.

Beyond successful ISR: case-by-case investigations for unmatched reassay results when ISR passed

Incurred sample reanalysis (ISR) is now commonly practiced in regulated bioanalytical laboratories. With an average ISR success rate of 95% or higher and an increasing number of ISR tests being conducted, more and more situations deserve scientific evaluation or investigation for the unmatched reassay results revealed in ISR tests even though they meet the acceptance criteria. First, should an investigation be initiated when an ISR test is acceptable? How large a discrepancy or what situation would warrant an investigation? What would be the impact on a study? How would investigations regarding unmatched reassay results be conducted? What are the main root causes identified? Can normal random errors cause a large discrepancy in unfavorable combinations? How could the timeline and cost be affected? All these questions are addressed in this paper with five real case examples.

Development and validation of UPLC tandem mass spectrometry assay for separation of a phase II metabolite of ramipril using actual study samples and its application to a bioequivalence study

In this paper, we present a validated UPLC-MS/MS assay for determination of ramipril and ramiprilat from human plasma samples. The assay is capable of isolating phase II metabolites (acylglucornides) of ramipril from in vivo study samples which is otherwise not possible using conventional HPLC conditions. Both analytes were extracted from human plasma using solid-phase extraction technique. Chromatographic separation of analytes and their respective internal standards was carried out using an Acquity UPLC BEH C(18) (2.1 × 100 mm), 1.7 µm column followed by mass spectrometric detection using an Waters Quattro Premier XE. The method was validated over the range 0.35-70.0 ng/mL for ramipril and 1.0-40.0 ng/mL for ramiprilat.

Critical topics in ensuring data quality in bioanalytical LC–MS method development

The use of LC–MS for bioanalysis of pharmaceuticals is entering its third decade and may be considered to be a mature technology. In many respects this is true, considering the advances made in such areas as instrument performance, electronics, software and automation of use. However, there remain instrumental and noninstrumental areas that require significant attention to ensure data quality. Increasing regulatory focus on analytical method performance and unaddressed method issues require the bioanalyst to understand those areas that most greatly impact data quality. This review will focus on instrumental and noninstrumental areas that can influence data quality, including reference standard and internal standard quality and physicochemical properties, matrix effects, stability in matrix, sample preparation, LC and MS.