Clinical Therapeutic Drug Monitoring Research Articles

A simple, robust and high-throughput LC-MS/MS method for the therapeutic drug monitoring of polymyxin B1, polymyxin B2, polymyxin B3, isoleucine-polymyxin B1, polymyxin E1 and polymyxin E2 in human plasma.

To facilitate clinical therapeutic drug monitoring (TDM) of polymyxin B (PB) and polymyxin E (PE), we developed and validated a simple LC-MS/MS method for simultaneous determination of PB (including polymyxin B1 (PB1), polymyxin B2 (PB2), polymyxin B3 (PB3) and isoleucine-polymyxin B1 (ile-PB1)) and PE (including polymyxin E1 (PE1) and polymyxin E2 (PE2)) in human plasma. PB or PE was extracted from 20.0μL plasma using a 5% (v/v) formic acid acetonitrile solution and separated on a BEH-C18 column (2.1 × 100 mm, 1.7μm) with a mobile phase consisting of 0.8% formic acid aqueous solution and 0.2% formic acid acetonitrile solution. Gradient elution was performed over 5.5min at a flow rate of 0.250 mL/min. Quantitative analysis was conducted in positive ion scanning mode by electrospray ionization and multiple reaction monitoring. The method validation was conducted based on bioanalytical method validation guidance, including specificity, calibration curve, precision, accuracy, recovery, matrix effect, stability and dilution integrity and all of the results satisfied the requirements. The method was simple, robust and high-throughput and is currently being used to provide a TDM service to enhancing therapeutic efficacy and safety use of the PB and PE.

An innovative strategy for Gefitinib quantification in pharmaceutical and plasma samples using a graphene quantum dots-combined gold nanoparticles composite electrochemical sensor.

Aninnovative methodology is proposedfor quantifying Gefitinib(GFT) using an electrochemical sensor constructed from a composite of graphene quantum dots (GQDs) and gold nanoparticles (AuNPs). GQDs were synthesized from graphite, preserving graphene's large surface area and excellent electron transfer capabilities while enhancing dispersibility. The combination of GQDs with AuNPs resulted in an AuNPs@GQDs composite, which was used to construct the sensor. The synthesized nanomaterials were characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and the electrochemical performance of the sensor was evaluated via cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Under optimized conditions, the sensor displayed a linear calibration curve for GFT detection within the range 0.01 to 10.0 µM, with a limit of detection (LOD) of 0.005 µM (S/N = 3). The sensor demonstrated excellent anti-interference properties and stability in tests using pharmaceutical formulations and plasma samples. Compared to chromatographic methods, the sensor exhibited similaraccuracy and recovery. Its easy fabrication and high sensitivity make it a promising tool for pharmaceutical analysis and clinical therapeutic drug monitoring.

SERS-Driven Ceftriaxone Detection in Blood Plasma: A Protein Precipitation Approach

Accurate detection of antibiotics in biological samples is essential for clinical diagnoses and therapeutic drug monitoring. This research examines how proteins and other substances in blood plasma affect the detection of the antibiotic ceftriaxone using surface-enhanced Raman spectroscopy (SERS). We detected ceftriaxone spiked in blood plasma without sample preparation within the range of 1 mg/mL to 50 µg/mL. By employing a pretreatment approach involving methanol-based protein precipitation to eliminate interfering substances from a spiked blood plasma solution, we could detect ceftriaxone down to 20 µg/mL. The comparative analysis demonstrates that the protein precipitation step enhances the sensitivity of SERS-based detection of drugs in the matrix blood plasma. The insights derived from this study are highly beneficial and can prove advantageous in developing new antibiotic detection methods that are both sensitive and selective in complex biological matrices. These methods can have important implications for clinical treatments.

Quantification of tricyclic glycopeptide in human plasma by UHPLC-MS3 coupled with counter-extraction follow by protein precipitation to enhance sensitivity

An ultra-high performance liquid chromatography tandem mass spectrometry cubed (UHPLC/MS3) assay coupled with protein precipitation and counter-extraction for detection of tricyclic glycopeptide vancomycin in human plasma was established and validated in this study. After protein precipitation and counter-extraction with dichloromethane, chromatographic separation of vancomycin and norvancomycin were performed on a reversed phase column (XBridge Peptide BEH C18 column, 2.1 × 100 mm I.D, 3.5 μm). The transition (parent ions → fragment ions → further fragment ions) at m/z 725.3 → 144.1 → 100.1 was used for quantification of vancomycin. The transition (parent ions → fragment ions) at m/z 718.3 → 144.2 was used for detection of norvancomycin. The linear range of the developed analytical method for quantification of vancomycin was 0.5–100 µg/mL (r = 0.9989). The range of intra- and inter-day precisions of the assay among low, medium and high concentrations is between 1.88 % and 6.33 %. The sensitivity of the analytical method was significantly improved by using MS3 technique as monitoring mode and counter-extraction with dichloromethane followed by protein precipitation as sample processing assay. The developed UHPLC/MS3 assay was successfully applied for clinical therapeutic drug monitoring (TDM) of vancomycin in 45 human plasma samples.

MonoTip C18 pipette tip solid-phase extraction coupled with liquid chromatography-tandem mass spectrometry enables rapid and automated therapeutic drug monitoring of tyrosine kinase inhibitors

This work presents an advanced automated monolithic C18 pipette-tip solid-phase extraction (PT-SPE) method seamlessly integrated with liquid chromatography-tandem mass spectrometry (LC-MS/MS) for precise therapeutic drug monitoring of eleven tyrosine kinase inhibitors (TKIs) in biological samples. Commercially available MonoTip C18 columns facilitate superior extraction efficiency and selectivity from complex biological matrices owing to their large surface areas and enhanced mass transfer capabilities. The sample preparation process, conducted by aspirating and dispensing solutions using a pipettor, completes the overall extraction process within 3 min. The method validation demonstrated excellent linearity within the range of 0.2/0.5/0.8 to 200 ng/mL, with detection limits ranging from 0.049 to 0.206 ng/mL. The method exhibited outstanding accuracy and precision, with intraday relative recovery rates ranging from 96.3 % to 115.0 % and interday recovery rates ranging from 95.0 % to 115.7 %, with coefficient of variation values consistently below 13.8 %. The proposed method is distinguished by its exceptional efficiency, reduced solvent use, enhanced environmental sustainability, and streamlined automation—key advantages in the realm of clinical therapeutic drug monitoring of TKIs. Overall, the MonoTip C18 PT-SPE technique, coupled with LC-MS/MS, offers a formidable, eco-friendly, and effective strategy for the TDM of TKIs, marking a significant advancement in the field.

Development of Simultaneous Drug Concentration Measurement Method Using an Automated Pretreatment Liquid Chromatography/Tandem Mass Spectrometry System for Therapeutic Drug Monitoring.

Therapeutic drug monitoring (TDM) is a personalized treatment approach that involves optimizing drug dosages based on patient-specific factors, such as drug plasma concentrations, therapeutic efficacy, or adverse reactions. The plasma concentration of drugs is determined using liquid chromatography/tandem mass spectrometry (LC-MS/MS) or various immunoassays. Compared with immunoassays, LC-MS/MS requires more pretreatment time as the number of samples increases. Recently, fully automated pretreatment LC-MS/MS systems have been developed to automatically perform whole-sample pretreatment for LC-MS/MS analysis. In this study, we developed a method for simultaneous concentration determination of five analytes (clozapine, mycophenolic acid, sunitinib, N-desethylsunitinib, and voriconazole) using LC-MS/MS for clinical TDM using a fully automated LC-MS/MS pretreatment system. In the developed method, the intra- and inter-assay relative error (RE) values ranged between -14.8% and 11.3%; the intra- and inter-assay coefficient of variation (CV) values were <8.8% and <10.5%, respectively. The analytes showed good stability, with RE values ranging between -13.6% and 10.9% and CV values <8.9%. Furthermore, the plasma concentrations in clinical samples using this method and the conventional manual pretreatment method showed similar results. Therefore, the method developed in this study could be considered a useful pretreatment method for routine TDM in patients.

Simultaneous determination of three tyrosine kinase inhibitors and three triazoles in human plasma by LC-MS/MS: applications to therapeutic drug monitoring and drug-drug interaction studies

Tyrosine kinase inhibitors (TKIs) and triazole antifungals are the first-line drugs for treating chronic myeloid leukemia (CML) and fungal infections, respectively, but both suffer from large exposure differences and narrow therapeutic windows. Moreover, these two types of drugs are commonly used together in CML patients with fungal infections. Multiple studies and guidelines have suggested the importance of therapeutic drug monitoring (TDM) of TKIs and triazoles. Currently, methods for the simultaneous determination of both types of drugs are limited. We developed a simple, rapid, and reliable liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for simultaneous quantification of three commonly used TKIs (imatinib, dasatinib, and nilotinib) and three commonly used triazoles (voriconazole, itraconazole, and posaconazole) in human plasma. The analytes were eluted on a Welch XB-C18 analytical column (50 × 2.1 mm, 5 µm) at 0.7 mL/min, using a gradient elution of 10 mM ammonium formate (A) and methanol–acetonitrile-isopropanol (80:10:10, v/v/v) containing 0.2 % formic acid (B) with a total analysis time of 3.5 min. The calibration curves were linear over the range from 20 to 4000 ng/mL for imatinib and nilotinib, from 2 to 400 ng/mL for dasatinib, and from 50 to 10,000 ng/mL for voriconazole, itraconazole, and posaconazole. Selectivity, accuracy, precision, recovery, matrix effect, and stability all met the validation requirements. The method was successfully used for TDM in CML patients who co-treated with both TKIs and triazoles. Drug-drug interaction analysis between TKIs and triazoles showed that a significant positive correlation was observed between imatinib and voriconazole, as well as dasatinib and voriconazole. Therefore, this method can be well applied in clinical TDM for patients receiving TKIs, triazoles, or both simultaneously.

Outcome of intravenous and inhaled polymyxin B treatment in patients with multidrug-resistant gram-negative bacterial pneumonia

PurposeThe incidence of pneumonia caused by multidrug-resistant gram-negative bacteria (MDR GNB) is increasing, which imposes significant burden on public health. Inhalation combined with intravenous polymyxins has emerged as a viable treatment option. However, pharmacokinetic studies focusing on intravenous and inhaled polymyxin B (PMB) are limited. MethodsThis study included seven patients with MDR GNB-induced pneumonia who were treated with intravenous plus inhaled PMB from March 1 to November 30, 2022, in the intensive care unit of the First Affiliated Hospital of Zhejiang University School of Medicine. Clinical outcomes and therapeutic drug monitoring data of PMB in both plasma and epithelial lining fluid (ELF) were retrospectively reviewed. ResultsMedian PMB concentrations in the ELF were 7.83 (0.72–66.5), 116.72 (17.37–571.26), 41.1 (3.69–133.78) and 33.82 (0.83–126.68) mg/L at 0, 2, 6 and 12 h, respectively, and were much higher than those detected in the serum. ELF concentrations of PMB at 0, 2, 6 and 12 h were higher than the minimum inhibitory concentrations of pathogens isolated from the patients. Steady-state concentrations of PMB in the plasma were >2 mg/L in most patients. Of the patients, 57.14% were cured and 71.43% showed a favourable microbiological response. The incidence of side effects with PMB was low. ConclusionsInhaled plus intravenous PMB can achieve high ELF concentrations and favourable clinical outcomes without an increased adverse effect profile. This treatment approach appears promising for the treatment of patients with pneumonia caused by MDR-GNB.

Prolonged treatment of dermatophytosis caused by Trichophyton indotinea with terbinafine or itraconazole impacts better outcomes irrespective of mutation in the squalene epoxidase gene.

Over the past decades, the increasing incidence of recurrent dermatophytosis associated with terbinafine-resistant Trichophyton has posed a serious challenge in management of dermatophytosis. Independent reports of failure of treatment and high minimum inhibitory concentrations (MIC) of antifungals are available, but data correlating MIC and clinical outcomes is still sparse. Therefore, the present study was conducted to evaluate the outcomes of systemic treatment of dermatophytosis and its correlation with MIC of the etiological agents isolated from such patients. Retrospective analysis of 587 consecutive patients with dermatophytosis was done from March 2017 to March 2019. Demographic and clinical details of the patients were noted, along with the results of direct microscopy and fungal culture. The isolates were identified by sequencing the internal transcribed spacer region of rDNA. Antifungal susceptibility testing was performed following the CLSI M38 protocol. Mutation in the squalene epoxidase (SE) gene was detected by DNA sequencing and ARMS-PCR. Based on the culture-positivity and prescribed systemic antifungal, patients were categorised into Group I culture-positive cases treated with systemic terbinafine and Group II culture-positive cases treated with systemic itraconazole, each for a total period of 12 weeks. In the present study, 477 (81.39%) were culture-positive; however, 12 weeks follow-up was available for 294 patients (Group I-157 and Group II-137) who were included for statistical analysis. In both groups [Group I-37/63 (51.4%) and Group II-14/54 (58.3%)], a better cure rate was observed if the initiation of therapy was performed within <6 months of illness. Treatment outcome revealed that if therapy was extended for 8-12 weeks, the odds of cure rate are significantly better (p < .001) with either itraconazole (Odd Ratio-15.5) or terbinafine (Odd Ratio-4.34). Higher MICs for terbinafine were noted in 41 cases (cured-18 and uncured-23) in Group I and 39 cases (cured-16 and uncured-23) in Group II. From cured (Group I-17/18; 94.4% and Group II-14/16; 87.5%) and uncured (Group I-20/23; 86.9% and Group II-21/23; 91.3%) cases had F397L mutation in the SE gene. No significant difference in cure rate was observed in patients with Trichophyton spp. having terbinafine MIC ≥ 1or <1 μg/mL (Group I-p = .712 and Group II-p = .69). This study revealed that prolonging terbinafine or itraconazole therapy for beyond 8 weeks rather than the standard 4 weeks significantly increases the cure rate. Moreover, no correlation has been observed between antifungal susceptibility and clinical outcomes. The MIC remains the primary parameter for defining antifungal activity and predicting the potency of antifungal agents against specific fungi. However, predicting therapeutic success based solely on the MIC of a fungal strain is not always reliable, as studies have shown a poor correlation between invitro data and invivo outcomes. To address this issue, further correlation of antifungal susceptibility testing (AFST) data with clinical outcomes and therapeutic drug monitoring is needed. It also highlights that initiation of the treatment within <6 months of illness increases cure rates and reduces recurrence. Extensive research is warranted to establish a better treatment regime for dermatophytosis.

Relevance of plasma lenvatinib concentrations and endogenous urinary cytochrome P450 3A activity biomarkers in clinical practice.

Lenvatinib (LEN), a multitarget tyrosine kinase inhibitor used in various cancer treatments, is mainly metabolized by cytochrome P450 3A (CYP3A) enzymes. The importance of therapeutic drug monitoring (TDM) in patients administered LEN has been proposed. Although some biomarkers of endogenous CYP3A activity have been reported, their utility in dosage adjustments has not been well evaluated. This study investigated the correlation between plasma LEN concentrations and endogenous urinary CYP3A biomarkers in clinical practice. Concentrations of plasma LEN (N = 225) and CYP3A biomarkers (cortisol, 6β-hydroxycortisol, deoxycholic acid, and 1β-hydroxydeoxycholic acid) in urine (N = 214) from 20 patients (hepatocellular carcinoma, N = 6; thyroid cancer, N = 3; endometrial cancer, N = 8; and renal cell carcinoma, N = 3) collected for consultation for up to 1 year were evaluated using liquid chromatography-tandem mass spectrometry. Moreover, plasma trough LEN concentrations were predicted using a three-compartment model with linear elimination for outpatients administered LEN before sample collection. Moderate correlations were observed between the quantified actual concentrations and the predicted trough concentrations of LEN, whereas there was no correlation with endogenous urinary CYP3A biomarkers. The utility of endogenous urinary CYP3A biomarkers could not be determined. However, TDM for outpatients administered orally available medicines may be predicted using a nonlinear mixed effect model (NONMEM). This study investigated the utility of endogenous urinary CYP3A biomarkers for personalized medicine and NONMEM for predicting plasma trough drug concentrations. These findings will provide important information for further clinical investigation and detailed TDM.

Development, validation and long-term evaluation of a liquid chromatography-tandem mass spectrometry method for simultaneous quantification of amiodarone, desethylamiodarone and mexiletine in human plasma and serum

Amiodarone and mexiletine are used for ventricular arrhythmias, for which a combination therapy of both anti-arrhythmic drugs (AADs) is not uncommon. Therapeutic drug monitoring (TDM) can be beneficial for clinical guidance of therapy, especially to correctly identify adverse events. Desethylamiodarone, the active metabolite of amiodarone, accumulates over time and is associated with serious adverse events. Therefore, simultaneous TDM for amiodarone, desethylamiodarone and mexiletine is advantageous in clinical practice. The presented LC-MS/MS method was validated for selectivity, matrix effect, linearity, accuracy, precision, carry-over and stability. The method was continuously evaluated during eight months of clinical use. The method was shown to be linear within the measured range of 0.1 to 10 mg/L for each component. The matrix effect was considered negligible. No interfering responses were found for amiodarone, desethylamiodarone and the isotopic-labeled internal standards. A constant and reproducible within-run contribution of 45.3 %, originating from the system, was identified for mexiletine. The systemic contribution to the peak area of the lowest quantifiable concentration of mexiletine affected the selectivity and carry-over effect measurements. Multiple measurements showed that regression adjusted concentrations were accurate and reproducible, indicating calibration correction was applicable. Sample stability was found to be within limits for all storage conditions and freeze–thaw cycles. Furthermore, long-term method evaluation with external controls resulted in stable measurements with a percentage coefficient of variance between 1.3 % and 6.3 %. The presented practical and reliable method is applicable for clinical TDM and will allow clinical practitioners to guide drug therapy of amiodarone and mexiletine.

A sensitive analytical strategy of oligonucleotide functionalized fluorescent probes for detection of nusinersen sodium in human serum

Spinal muscular atrophy (SMA) is a rare autosomal recessive neuromuscular disease. Nusinersen sodium (NS) is the world's first antisense oligonucleotide (ASO) drug for SMA precise targeted therapy. However, the limited half-life of oligonucleotides and their tendency to accumulate in hepatic and renal tissues presented significant challenges for clinical investigation and therapeutic drug monitoring. In this study, we proposed an analytical strategy based on the specific capture of oligonucleotide functionalized fluorescent probes by single stranded binding proteins (SSB) for ultra-sensitive and high-throughput detection of nusinersen sodium in human serum. The magnetic nanoparticles modified with single-strand binding protein (MNPs-SSB) selectively bonded to the red fluorescent quantum dots functionalized with oligonucleotides (RQDs-ssDNA) that were complementary to nusinersen sodium. Upon interaction with nusinersen sodium, RQDs-ssDNA formed a double-stranded complex (RQDs-ssDNA-NS), resulting in enhanced red fluorescence after magnetic separation as it was no longer captured by MNPs-SSB but remained in the supernatant. A quantitative analysis of nusinersen sodium in biological samples was successfully achieved by establishing a relationship between fluorescence intensity and its concentration. The detection signal F/F0 exhibited a linear correlation (R2 = 0.9871) over a wide range from 0.1 nM to 200 nM, with a limit of detection (LOD) of 0.03 nM, demonstrating the high specificity and rapid analysis time (only 30 min). This method provided a novel approach for sensitive, high-throughput, and specific analysis of nusinersen sodium and similar ASO drugs.

Therapeutic Drug Monitoring of 6 New-Generation Antiseizure Medications Using a Mass Spectrometry Method: Analysis of 2-Year Experience in a Large Cohort of Korean Epilepsy Patients.

New-generation antiseizure medications (ASMs) are increasingly prescribed, and therapeutic drug monitoring (TDM) has been proposed to improve clinical outcome. However, clinical TDM data on new-generation ASMs are scarce. To develop and validate a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for therapeutic drug monitoring (TDM) of 6 new-generation ASMs in serum and analyze the clinical TDM data from a large cohort of Korean patients with epilepsy. Stable isotope-labeled internal standards were added to protein precipitations of serum. One microliter of sample was separated on Agilent Poroshell EC-C18 column, and lacosamide, perampanel, gabapentin, pregabalin, vigabatrin, and rufinamide were simultaneously quantified by Agilent 6460 triple-quad mass spectrometer in multiple-reaction monitoring mode. Linearity, sensitivity, precision, accuracy, specificity, carryover, extraction recovery, and matrix effect were evaluated. TDM data of 458 samples from 363 Korean epilepsy patients were analyzed. The method was linear with limit of detection less than 0.05 μg/mL in all analytes. Intraassay and interassay imprecisions were less than 5% coefficient of variation. Accuracy was within ±15% bias. Extraction recovery ranged from 85.9% to 98.8%. A total of 88% (403 of 458) were on polypharmacy, with 29% (118 of 403) using concomitant enzyme inducers. Only 38% (175 of 458) of the concentrations were therapeutic, with 53% (244 of 458) being subtherapeutic. Drug concentration and concentration-to-dose ratio were highly variable among individuals in all 6 ASMs. A simple and rapid LC-MS/MS method for TDM of 6 ASMs was developed and successfully applied to clinical practice. This large-scale TDM data could help establish an effective monitoring strategy for these drugs.

Coadministration of isavuconazole and sirolimus in allogeneic hematopoietic stem cell transplant recipients.

Invasive fungal infections (IFIs) represent a major cause of morbidity among allogeneic hematopoietic stem cell transplantation (allo-HSCT). Isavuconazole (ISA) is a broad-spectrum triazole with favorable safety profile. Herein, we evaluate the real life coadministration of ISA and sirolimus in allo-HSCT recipients in a single-center retrospective analysis, describing clinical efficacy, safety, and therapeutic drug monitoring (TDM) of both drugs. All consecutive allo-HSCT recipients who received the coadministration of ISA and sirolimus for at least 2 weeks between July 2017 and December 2022 were included in this retrospective analysis. TDM was longitudinally performed during treatment. IFIs were classified according to the revised European Organization for Research and Treatment of Cancer/Mycoses Study Group consensus criteria. A total of 51 recipients were included in the analysis. A total of 17 patients received ISA as continuous antifungal treatment for IFI diagnosed before transplant: one patient experienced a probable invasive pulmonary aspergillosis, and one patient switched from ISA to liposomal amphotericin B for a possible IFI. A total of 34 patients started ISA as antifungal therapy for IFI diagnosed after transplant. Sixteen of 34 were treated for a proven/probable breakthrough IFI during mold-active prophylaxis: 6/16 patients died for IFI after a median of 51 days of ISA. Eighteen of 34 started ISA as empirical therapy for a possible IFI: 15/18 patients were alive with resolution of infection after 6 weeks, 1 died for disease progression, and 2 had empirically changed antifungal therapy due to pneumonia progression. Clinical and radiological response rate was 68% after 90 days from IFI diagnosis. No toxicities related to drug-drug interaction have been registered in patients reaching concomitant therapeutic levels of ISA and sirolimus. The coadministration of ISA and sirolimus was safe and feasible in this cohort, confirming favorable clinical efficacy in patients with multiple-drug coadministration.

Discordance Between Inflammatory Bowel Disease Specialists and Insurance Authorization Denials-A Survey of Specific Inflammatory Bowel Disease Treatment Scenarios.

Prior authorizations are generally required by insurers for gastroenterologists to prescribe biologics and small-molecule drugs to treat inflammatory bowel disease (IBD). Authorization denials occur in a wide variety of clinical scenarios, including denials of standard and nonstandard medication dosing. We performed a national cross-sectional survey on a broad variety of specific clinical scenarios to assess experience and opinions on whether or not insurance authorization denials are in accordance with clinical expertise. Eighty-four gastroenterologists completed the survey. Denial experience was common for infliximab dose modifications, vedolizumab dose modifications, ustekinumab first-time therapy, and maintenance dosing. The bulk of disagreement with authorization denials involved scenarios of dose escalation and re-induction guided by both loss of clinical response and/or therapeutic drug monitoring, denial of re-authorizations of stable dosing, and use of non-anti-TNFs in specific patient populations including the elderly and patients with multiple comorbidities. Respondents unanimously agreed that insurance companies do not play an adequate role in helping patients obtain PA. Furthermore, most of the respondents agree that to decrease the burden of the PA process, peer-peer processes should be between other IBD-trained providers who understand these complex treatment strategies. Our cross-sectional survey highlights the degree of discordance in clinical decision-making between insurers and gastroenterologists. Further engagement between gastroenterologists and insurers is needed to foster common understanding on these discordant authorization denials in these real-world clinical IBD scenarios.

Ranolazine Quantification in Human Plasma: A QbD-Guided LC-MS Method Development and Validation

The present research outlines a comprehensive and systematic approach for the development and validation of a bioanalytical Liquid chromatography–mass spectrometry (LC-MS) method to quantify ranolazine in human plasma. The study employs principles of quality by design (QbD) to enhance method robustness, precision, and accuracy. The primary goals of this research were to create a reliable LC-MS method for the accurate quantification of ranolazine in human plasma and to validate this approach in accordance with established standards set by regulatory bodies. A secondary objective was to explore the application of QbD principles to optimize method performance. The study resulted in the successful development of an LC-MS method that exhibits exceptional specificity, sensitivity, accuracy, and precision in the quantification of ranolazine in human plasma. Specificity tests revealed no interference from endogenous plasma components. The method demonstrated good sensitivity with limit of quantitation (LoQ) of 5 ng/mL and limit of detection (LoD) of 2 ng/mL. Accuracy, as assessed through recovery studies, showed mean recoveries of 98, 99, and 101% for three different spiked concentrations. Precision, expressed as RSD, was below 5% for both intra-day and inter-day analyses. Linearity studies resulted in a calibration curve with an R² value of 0.9998. By employing QbD principles, the method demonstrated improved robustness, thus minimizing the impact of variability during sample analysis. Robustness experiments revealed minimal effects on precision and accuracy when varying critical parameters. This research not only presents a reliable LC-MS method for ranolazine quantification but also underscores the importance of incorporating QbD principles in bioanalytical method development. The validated method holds significant implications for clinical research, pharmacokinetic studies, and therapeutic drug monitoring. By enhancing the accuracy and robustness of ranolazine quantification, this method contributes to the advancement of pharmaceutical and clinical research, ultimately benefiting patient care and treatment outcomes.

Stepwise Introduction of Elexacaftor-Tezacaftor-Ivacaftor in Patients With Cystic Fibrosis and Liver Cirrhosis Child-Pugh A or B Using Clinical and Therapeutic Drug Monitoring: A Case Series

Cystic fibrosis (CF) is a monogenetic disease caused by mutations in the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR) protein and affecting multiple organs, including the lungs and liver. Almost 90% of people affected carry at least 1 Phe508del CFTR mutation. Medical treatment with the CFTR-modulating drug elexacaftor-tezacaftor-ivacaftor (ETI) has been proven to be efficacious in carriers of at least 1 Phe508del CFTR mutation. Use of ETI in patients with CF (pwCF) and liver cirrhosis is still controversial. Therefore, stepwise introduction of ETI in pwCF and liver cirrhosis Child-Pugh A or B was evaluated using clinical and therapeutic drug monitoring. Seven consecutive pwCF received ETI. Four dosing steps were defined, at each of which the patients underwent clinical examination, routine blood tests, and therapeutic drug monitoring. Exposure of elexacaftor, tezacaftor, and ivacaftor was assessed by means of determination of AUC. ETI was successfully introduced and maintained in all pwCF. In those with Child-Pugh B cirrhosis (n = 2), diminishment of the dose as recommended by the label resulted in AUC values that were lower than the mean AUC values in pwCF without hepatic impairment, as reported previously. Despite the limitations of this small case series, stepwise elevation of ETI dose did not induce clinical adverse effects or increases in serum liver test results under strict clinical follow-up and therapeutic drug monitoring, and may allow tolerable introduction of this therapy in pwCF and cirrhosis Child-Pugh A and possibly B.

Development and validation of enzyme-linked immunosorbent assays for the measurement of infliximab and anti-drug antibody levels

Infliximab and its anti-drug antibody (ADA) serum concentrations exhibit a strong correlation with clinical response and loss of response. The use of therapeutic drug monitoring to measure the concentration of infliximab and ADA can facilitate clinical decision-making, helping patients attain optimal therapeutic effects. However, there are still limitations to the existing infliximab and its ADA detection methods. Therefore, this study aimed to develop and validate enzyme-linked immunosorbent assay (ELISA)-based methods for measuring infliximab and its ADA levels in human plasma according to the general recommendations for immunoassays. Free infliximab is bound by recombinant TNF-α and detected using HRP-labeled anti-human antibody. The ADA is captured by on-plate-coated infliximab and recognized by biotin-labeled infliximab. Two bridging ELISA assays were developed and after assay optimization and validation, these assays have been applied in ten patients with inflammatory bowel disease (IBD). In infliximab detection assay, a standard curve ranging from 0.10 μg/mL to 8.0 μg/mL with great precision and accuracy has been established. Drug tolerance of the ADA assay was that 100 ng/mL ADA could tolerate at least 5.0 μg/mL infliximab in the plasma using a commercially available monoclonal anti-infliximab antibody as the positive control. The ADA screening and confirmatory assays achieved a sensitivity of 36.74 ng/mL and 37.15 ng/mL, respectively. All other assay characteristics met the requirements. The mean concentration of infliximab in eight patients with IBD was 7.88 (1.87–21.1) μg/mL, and the ADA levels were all negative. Moreover, the concentrations of infliximab in the remaining two patients were below the LLOQ and the ADAs were positive. Thus, accurate and sensitive ELISA methods have been developed and validated for the detection of infliximab and its ADA concentrations and have been successfully applied to clinical therapeutic drug monitoring.

From "wet" matrices to "dry" blood spot sampling strategy: a versatile LC-MS/MS assay for simultaneous monitoring caffeine and its three primary metabolites in preterm infants.

To update traditional "wet" matrices to dried blood spot (DBS) sampling, based on the liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) technique, and develop a method for simultaneous analyzing caffeine and its three primary metabolites (theobromine, paraxanthine, and theophylline), supporting routine therapeutic drug monitoring (TDM) for preterm infants. DBS samples were prepared by a two-step quantitative sampling method, i.e.,volumetric sampling of a quantitative 10 μL volume of peripheral blood and an 8 mm diameter whole punch extraction by a methanol/water (80/20, v/v) mixture containing 125 mM formic acid. Four paired stable isotope labeled internal standards and a collision energy defect strategy were applied for the method optimization. The method was fully validated following international guidelines and industrial recommendations on DBS analysis. Cross validation with previously developed plasma method was also proceeded. The validated method was then implemented on the TDM for preterm infants. The two-step quantitative sampling strategy and ahigh recovery extraction method were developed and optimized. The method validation results were all within the acceptable criteria. Satisfactory parallelism, concordance, and correlation were observed between DBS and plasma concentrations of the four analytes. The method was applied to provide routine TDM services to 20 preterm infants. A versatile LC-MS/MS platform for simultaneous monitoring caffeine and its three primary metabolites was developed, fully validated, and successfully applied into the routine clinical TDM practices. Sampling method switching from "wet" matrices to "dry" DBS will facilitate and support the precision dosing of caffeine for preterm infants.

Evaluation of Vancomycin Area Under the Concentration-Time Curve Predictive Performance Using Bayesian Modeling Software With and Without Peak Concentration: An Academic Hospital Experience for Adult Patients Without Renal Impairment.

The revised U.S. consensus guidelines on vancomycin therapeutic drug monitoring (TDM) recommend obtaining trough and peak samples to estimate the area under the concentration-time curve (AUC) using the Bayesian approach; however, the benefit of such two-point measurements has not been demonstrated in a clinical setting. We evaluated Bayesian predictive performance with and without peak concentration data using clinical TDM data. We retrospectively analyzed 54 adult patients without renal impairment who had two serial peak and trough concentration measurements in a ≤1-week interval. The concentration and AUC values were estimated and predicted using Bayesian software (MwPharm++; Mediware, Prague, Czech Republic). The median prediction error (MDPE) for bias and median absolute prediction error (MDAPE) for imprecision were calculated based on the estimated AUC and measured trough concentration. AUC predictions using the trough concentration had an MDPE of -1.6% and an MDAPE of 12.4%, whereas those using both peak and trough concentrations had an MDPE of -6.2% and an MDAPE of 16.9%. Trough concentration predictions using the trough concentration had an MDPE of -8.7% and an MDAPE of 18.0%, whereas those using peak and trough concentrations had an MDPE of -13.2% and an MDAPE of 21.0%. The usefulness of the peak concentration for predicting the AUC on the next occasion by Bayesian modeling was not demonstrated; therefore, the practical value of peak sampling for AUC-guided dosing can be questioned. As this study was conducted in a specific setting and generalization is limited, results should be interpreted cautiously.