Key elements of bioanalytical method validation for small molecules

Method validation is a process that demonstrates that a method will successfully meet or exceed the minimum standards recommended in the Food and Drug Administration (FDA) guidance for accuracy, precision, selectivity, sensitivity, reproducibility, and stability. This article discusses the validation of bioanalytical methods for small molecules with emphasis on chromatographic techniques. We present current thinking on validation requirements as described in the current FDA Guidance and subsequent 2006 Bioanalytical Methods Validation Workshop white paper.     

Method validation in the bioanalytical laboratory

Bioanalytical methods, based on a variety of physico-chemical and biological techniques such as chromatography, immunoassay and mass spectrometry, must be validated prior to and during use to engender confidence in the results generated. The fundamental criteria for assessing the reliability and overall performance of a bioanalytical method are: the evaluation of drug and analyte stability, selectivity, limits of quantification and detection, accuracy, precision, linearity and recovery. The extent to which a method is validated is dependent on its prospective use, the number of samples to be assayed and the use to which the data are put.

Specific analytical techniques may require additional validation such as antibody-binding characteristics, peak purity determination, evaluation of matrix effects or structural confirmation of the analyte. Ideally each assay should be cross-validated with a method utilizing a highly specific detector such as a mass spectrometer. Once in use, the performance of the method should be monitored using quality control standards. If a method is set up in another laboratory, the performance of the assay should be monitored with quality control standards sent from the originating laboratory.     

Advances in validation, risk and uncertainty assessment of bioanalytical methods

Bioanalytical method validation is a mandatory step to evaluate the ability of developed methods to provide accurate results for their routine application in order to trust the critical decisions that will be made with them. Even if several guidelines exist to help perform bioanalytical method validations, there is still the need to clarify the meaning and interpretation of bioanalytical method validation criteria and methodology. Yet, different interpretations can be made of the validation guidelines as well as for the definitions of the validation criteria. This will lead to diverse experimental designs implemented to try fulfilling these criteria. Finally, different decision methodologies can also be interpreted from these guidelines. Therefore, the risk that a validated bioanalytical method may be unfit for its future purpose will depend on analysts personal interpretation of these guidelines. The objective of this review is thus to discuss and highlight several essential aspects of methods validation, not only restricted to chromatographic ones but also to ligand binding assays owing to their increasing role in biopharmaceutical industries. The points that will be reviewed are the common validation criteria, which are selectivity, standard curve, trueness, precision, accuracy, limits of quantification and range, dilutional integrity and analyte stability. Definitions, methodology, experimental design and decision criteria are reviewed. Two other points closely connected to method validation are also examined: incurred sample reproducibility testing and measurement uncertainty as they are highly linked to bioanalytical results reliability. Their additional implementation is foreseen to strongly reduce the risk of having validated a bioanalytical method unfit for its purpose.     

Bioanalytical Method Validation for Macromolecules in Support of Pharmacokinetic Studies

The development and validation of ligand binding assays used in the support of pharmacokinetic studies has been the focus of various workshops and publications in recent years, all in an effort to establish a guidance document for standardization of these bioanalytical methods. This summary report of the workshop from 2003 focuses on the issues discussed in presentations and notes points of discussion and areas of consensus among the participants.     

Best practices during bioanalytical method validation for the characterization of assay reagents and the evaluation of analyte stability in assay standards, quality controls, and study samples

Characterization of the stability of analytes in biological samples collected during clinical studies together with that of critical assay reagents, including analyte stock solutions, is recognized as an important component of bioanalytical assay validation. Deficiencies in these areas often come to light during regulatory inspections. Best practices, based on current regulatory guidance, for the assessment of these issues as they pertain to ligand binding and chromatographic assays are covered in this review. Additionally, consensus recommendations reached during the recent AAPS/FDA Workshop on bioanalytical assay validation are highlighted.     

Aspects of bioanalytical method validation for the quantitative determination of trace elements

Bioanalytical methods are used to quantitatively determine the concentration of drugs, biotransformation products or other specified substances in biological matrices and are often used to provide critical data to pharmacokinetic or bioequivalence studies in support of regulatory submissions. In order to ensure that bioanalytical methods are capable of generating reliable, reproducible data that meet or exceed current regulatory guidance, they are subjected to a rigorous method validation process. At present, regulatory guidance does not necessarily account for nuances specific to trace element determinations. This paper is intended to provide the reader with guidance related to trace element bioanalytical method validation from the authors' perspective for two prevalent and powerful instrumental techniques: inductively coupled plasma-optical emission spectrometry and inductively coupled plasma-MS.     

Optimization and validation of a SPE-HPLC-PDA-fluorescence method for the simultaneous determination of drugs used in combined cardiovascular therapy in human plasma

This paper reports the chemometrical optimization and the validation of a quantitative high performance liquid chromatography-photodiode array-fluorescence (HPLC-PDA-Fluo) method for the simultaneous analysis, in human plasma, of drugs usually combined in cardiovascular therapy. Separation of chlorthalidone (CLTD), valsartan (VAL), valsartan-M1 (VAL-M1), fluvastatin (FLUV) and the internal standard (IS) candesartan cilexetil was performed on a dC18 Atlantis column (100 mm × 3.9 mm, 3 μm) using a gradient with a run time of 15 min. The mobile phase consisted of a mixture of acetonitrile and water containing 0.01% of formic acid and 10 mM of ammonium formate at pH 4.1. UV and fluorimetric (valsartan, its metabolite and fluvastatin) detectors were used. The sample preparation consisted of protein precipitation using acetonitrile suited to a solid-phase extraction (SPE) on a Strata-X cartridge for sample clean-up. Method validation was developed following the recommendations for bioanalytical method validation of International Conference on Harmonisation (ICH) and Food and Drug Administration (FDA) organizations. The method showed good linearity (31–3000 μg/l for chlorthalidone, 20–1000 μg/l for valsartan-M1, 10–5000 μg/l for valsartan and 14–1000 μg/l for fluvastatin), precision and accuracy. Recoveries were in the range of 78–91%. This method allowed the determination of these drugs in human plasma samples obtained from patients under cardiovascular treatment.     

Elimination of autosampler carryover in a bioanalytical HPLC-MS/MS method: a case study

A case study in identifying and eliminating the source of autosampler carryover in a bioanalytical HPLC-MS/MS assay is described. Through a series of systematic experiments, the carryover was traced to the injection valve and was eliminated by switching from a partial loop to a full loop injection, which provided more effective flushing of the sample flow path. The susceptibility of the HPLC system to carryover was demonstrated to depend on the absolute sensitivity of the detection method and the mass of analyte injected at the assay lower limit of quantitation (LLOQ).     

Regulatory recommendations for clopidogrel: Focus on validation of a reliable bioanalytical method and its application to a bioequivalence study

A rapid, simple, and sensitive liquid chromatography tandem mass spectrometric (LC–MS/MS) method for the determination of clopidogrel in human plasma was developed and validated using clopidogrel-d4 as the internal standard (IS). The analyte and the IS were extracted from 500 µl aliquots of human plasma via solid phase extraction. The precursor to product ion transitions monitored for clopidogrel and IS were m/z 322.2 → 212.0 and 326.2 → 216.0, respectively. The method was fully validated for sensitivity, accuracy and precision, linearity, recovery, matrix effect, dilution integrity, and stability. The Linearity range was 20.4–10,772.6 pg/mL with mean correlation coefficient (r) ≥ 0.9977. The back conversion was also evaluated during method validation as per EMA recommendation. Results proved that clopidogrel was accurately and reliably estimated by the method without any evidence of back conversion of clopidogrel acid. The method was successfully applied to a bioequivalence study of 75?mg clopidogrel bisulfate tablet formulation in 32 healthy male volunteers under fasting conditions. The ratios of least-squares means (with 90% confidence intervals) for the pharmacokinetic parameters C_max, AUC_0–t and AUC_0–α were 107.98% (94.52–123.35%), 100.25% (91.28–110.09%), and 100.49% (91.37–110.51%), respectively.     

Development and validation of an ion chromatography method for the determination of phosphate-binding of lanthanum carbonate

Lanthanum carbonate is indicated to reduce serum phosphate in patients with end stage renal disease (ESRD). When given orally, lanthanum carbonate dissociates in the acid environment of the upper gastrointestinal tract to release lanthanum ions. The free lanthanum ions bind with dietary phosphate released from food during digestion to form highly insoluble lanthanum–phosphate complexes which prevent the absorption of phosphate, consequently reduce the serum phosphate. In order to evaluate the in vitro binding capacity of lanthanum carbonate, a simple and efficient ion chromatography (IC) method was developed and validated for determination of phosphate across the pH range encountered in the gastrointestinal tract. Chromatographic separation was achieved on a Dionex ICS-2000 IC system using a Dionex AS16, IonPac (4 mm × 250 mm) analytical column and Dionex AG16, IonPac (4 mm × 50 mm) guard column. Column temperature was maintained at 30 °C. Injection volume was 10 μL. The compounds were eluted isocratically at a flow rate of 1 mL/min and detected by suppressed conductivity. The analytical method was validated according to USP Category I requirements. The validation characteristics included accuracy, precision, quantification limit, linearity, and stability. The intra-day accuracy ranged from 89% to 103% for the solutions of pH 1.2–6.8. The intra-day precision (RSD) ranged from 0.6% to 3.7% for the solutions of pH 1.2–6.8. The analytical range was linear from 2 to 200 ppm (mg/L). The R² ranged from 0.9998 to 1.0. This method was found to be simple, robust, sensitive, specific, and accurate. It has been successfully applied for determination of phosphate binding to lanthanum carbonate over the human gastrointestinal pH range at different time-points (from 0.5 to 24 h).     

Procedural elements involved in maintaining bioanalytical data integrity for good laboratory practices studies and regulated clinical studies

This article describes procedural elements involved in ensuring the integrity of bioanalytical data. These elements can be divided into 3 areas. First, there are those ensuring the integrity of the analyte until analysis, through correct sample collection, handling, shipment, and storage procedures. Incorrect procedures can lead to loss of analyte via instability, addition of analyte through contamination or instability of related metabolites, or changes in the matrix composition that may adversely affect the performance of the analytical method. Second, the integrity of the sample identity needs to be maintained to ensure that the final result reported relates to the individual sample that was taken. Possible sources of error include sample mixup or mislabeling, or errors in data handling. Finally, there is the overall integrity of the documentation that supports the analysis, and any prestudy validation of the method. This includes a wide range of information, from paper and electronic raw data, through standard operating procedures and analytical procedures and facility records, to study plans and final reports. These are critical to allow an auditor or regulatory body to reconstruct the study.     

Liquid chromatographic tandem mass spectrometric validated method for pharmacokinetic estimation of flecainide in human plasma

A sensitive high throughput LC/MS/MS method fully validated as per USFDA guidelines is described for pharmacokinetic estimation of flecainide in human plasma using loperamide as the internal standard. Plasma samples were monitored by cation exchange solid phase extraction achieving 78.6% extraction efficiency (mean recovery) followed by chromatographic separation on a PurospherStar RP-18e column. Detection was carried out on an API positive ESI by MRM transitions m/z 415.2/301.1 and 477.3/266.3 for flecainide and loperamide respectively. High sensitivity of 1.17ng/ml, dynamic linearity of 1.17–396.75 ng/ml and short run time within 3 minutes are other interesting aspects of this new bioanalytical method. This method was successfully applied to a pharmacokinetic study with 100mg tablet flecainide administered in Indian population for the first time. A randomized, single dose, two sequence, cross over study design was used to evaluate bioequivalence on 40 healthy male fasted volunteers and blood samples were collected up to 96 hours post dose. Noncompartmental pharmacokinetic analysis was used to evaluate AUC_0-t, AUC_0-inf, C_max, T_max, T_1/2 and λz scaled on a 90% confidence interval approach. Average bioequivalence results showed ratios of least square means and its 90% CIs for ln-transformed C_max, AUC_0-t and AUC_0-inf for flecainide were 99.99 (95.21–104.99) %, 98.27(93.89–102.86)% and 98.08(93.68–102.68)% respectively. Both the test and reference products were closely comparable in terms of rate and extent to which the drugs access the systemic circulation.     

Trace elements in e-liquids - Development and validation of an ICP-MS method for the analysis of electronic cigarette refills

Electronic cigarette use has rapidly increased in recent years. In assessing their safety, and in view of coming regulations, trace elements (TE) are among the potentially toxic compounds required to be evaluated in electronic cigarette refill fluids (“e-liquids”). An analytical method using inductively coupled plasma with mass spectrometric detection (ICP-MS) was developed and rigorously validated in order to determine concentrations of 15 TE in 54 e-liquids from a French brand. Despite a significant matrix effect from the main e-liquid constituents, and difficulties related to the current lack of reference materials, our method demonstrated satisfactory linearity, precision and robustness, and permitted the quantification of low concentrations of these 15 elements: lower limits of quantification (LLQ) obtained were ≤4 ppb for all elements except for Ni, Cu and Zn (16 ppb, 20 ppb and 200 ppb, respectively). All TE concentrations in all tested samples were <510 ppb, mostly near or below the LLQs. This method is transposable and is timely for laboratories seeking to meet a prospective demand in light of current or future regulations.     

Recommendations for the Bioanalytical Method Validation of Ligand-Binding Assays to Support Pharmacokinetic Assessments of Macromolecules

PURPOSE: With this publication a subcommittee of the AAPS Ligand Binding Assay Bioanalytical Focus Group (LBABFG) makes recommendations for the development, validation, and implementation of ligand binding assays (LBAs) that are intended to support pharmacokinetic and toxicokinetic assessments of macromolecules. METHODS: This subcommittee was comprised of 10 members representing Pharmaceutical, Biotechnology, and the contract research organization industries from the United States, Canada, and Europe. Each section of this consensus document addresses a specific analytical performance characteristic or aspect for validation of a LBA. Within each section the topics are organized by an assay's life cycle, the development phase, pre-study validation, and in-study validation. Because unique issues often accompany bioanalytical assays for macromolecules, this document should be viewed as a guide for designing and conducting the validation of ligand binding assays. RESULTS: Values of +/- 20% (25% at the lower limit of quantification [LLOQ]) are recommended as default acceptance criteria for accuracy (% relative error [RE], mean bias) and interbatch precision (%coefficient of variation [CV]). In addition, we propose as secondary criteria for method acceptance that the sum of the interbatch precision (%CV) and the absolute value of the mean bias (%RE) be less than or equal to 30%. This added criterion is recommended to help ensure that in-study runs of test samples will meet the proposed run acceptance criteria of 4-6-30. Exceptions to the proposed process and acceptance criteria are appropriate when accompanied by a sound scientific rationale. CONCLUSIONS: In this consensus document, we attempt to make recommendations that are based on bioanalytical best practices and statistical thinking for development and validation of LBAs.     

丹参滴注液清洁验证检验方法的确认研究

目的建立丹参滴注液清洁方法,对清洁残留检验方法进行验证确认。方法丹参滴注液生产结束后清洁剂为1％氢氧化钠溶液、1％枸橼酸溶液和注射用水,清洁后残留物限度≤10mg·L^-1,棉签擦拭取样,采用HPLC测定丹参素钠和原儿茶醛的残留量,色谱柱为C18柱（250mm×4．6mm,5μm）,流动相为甲醇-0．5％冰醋酸溶液（5：95）,流速1．0mL·min^-1。结果丹参素钠和原儿茶醛在下述范围内与峰面积呈良好的线性：（I）5．456～27．898mg·L^-1（r=0．9999）、（Ⅱ）0．530～2．684mg·L^-1（r=0．9999）。精密度和准确度在设定范围。结论丹参滴注液清洁方式可行,清洁效果确切,残留活性成分检测准确、灵敏,通过确认证明该检验方法可用于丹参滴注液清洁验证残留活性成分的检测。     

Development and validation of a high-performance liquid chromatographic method for bioanalytical application with rimonabant

A simple and feasible high-performance liquid chromatographic method with UV detection was developed and validated for the quantification of rimonabant in human plasma. The chromatographic separation was carried out in a Hypersil BDS, C₁₈ column (250 mm × 4.6 mm; 5 μm). The mobile phase was a mixture of 10 mM phosphate buffer and acetonitrile (30:70, v/v) at a flow rate of 1.0 ml/min. The UV detection was set at 220 nm. The extraction recovery of rimonabant in plasma at three quality control (QC) samples was ranged from 84.17% to 92.64%. The calibration curve was linear for the concentration range of 20–400 ng/ml with the correlation coefficient (r²) above 0.9921. The method was specific and sensitive with the limit of quantification of 20 ng/ml. The accuracy and precision values obtained from six different sets of QC samples analyzed in separate occasions ranged from 88.13% to 106.48% and 0.13% to 3.61%, respectively. In stability tests, rimonabant in human plasma was stable during storage and assay procedure. The method is very simple, sensitive and economical and the assay was applied to human plasma samples in a clinical (pharmacokinetic) study of rimonabant.     

氨咖黄敏片微生物限度检查方法验证试验研究

目的：建立氨咖黄敏片微生物限度检查方法。方法：以3株细菌、2株真菌对氨咖黄敏片进行了微生物限度检查方法的验证试验。结果：试验组枯草芽孢杆菌采用培养基稀释法回收率为76％以上；大肠埃希菌、金黄色葡萄球菌、黑曲霉、白色念珠菌采用常规法回收率为81％以上；控制菌检查试验组采用200mL以上增菌培养基，可检出大肠埃希菌。结论i经验证氨咖黄敏片微生物限度采用培养基稀释法检查细菌、控制菌；常规法检查霉菌、酵母菌。     

Quantitative Bioanalytical Methods Validation and Implementation: Best Practices for Chromatographic and Ligand Binding Assays

Abstract The Third AAPS/FDA Bioanalytical Workshop, entitled “Quantitative Bioanalytical Methods Validation and Implementation: Best Practices for Chromatographic and Ligand Binding Assays” was held on May 1–3, 2006 in Arlington, VA. The format of this workshop consisted of presentations on bioanalytical topics, followed by discussion sessions where these topics could be debated, with the goal of reaching consensus, or identifying subjects where addition input or clarification was required. The discussion also addressed bioanalytical validation requirements of regulatory agencies, with the purpose of clarifying expectations for regulatory submissions. The proceedings from each day were reviewed and summarized in the evening sessions among the speakers and moderators of the day. The consensus summary was presented back to the workshop on the last day and was further debated. This communication represents the distillate of the workshop proceedings and provides the summary of consensus reached and also contains the validation topics where no consensus was reached. The views expressed in this article are those of the authors and do not reflect official policy at the FDA. No official endorsement by the FDA is intended or should be inferred.