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(Abstracted from JAMA2023;330:2191–2199)Due to availability and cultural factors, cannabis use among pregnant women has greatly increased in the last 10 years and is viewed by many individuals as safe. Much of the previous research in this area has been limited by lack of accurate assessment of exposure, relying primarily on self-report.

Pharmacogenomic testing interrogates germline sequence variants implicated in interindividual drug response variability to infer a drug response phenotype and to guide medication management for certain drugs. Specifically, discrete aspects of pharmacokinetics, such as drug metabolism, and pharmacodynamics, as well as drug sensitivity, can be predicted by genes that code for proteins involved in these pathways. Pharmacogenomics is unique and differs from inherited disease genetics because the drug response phenotype can be drug-dependent and is often unrecognized until an unexpected drug reaction occurs or a patient fails to respond to a medication. Genes and variants with sufficiently high levels of evidence and consensus may be included in a clinical pharmacogenomic test; however, result interpretation and phenotype prediction can be challenging for some genes and medications. This document provides a resource for laboratories to develop and implement clinical pharmacogenomic testing by summarizing publicly available resources and detailing best practices for pharmacogenomic nomenclature, testing, result interpretation, and reporting.

Introduction: The prevalence of 2R/2R TYMSgenotype is variable but estimated to be around 20–30% in Caucasians. The clinical relevance of TYMS 2R/2Rgenotype in predicting severe fluoropyrimidine-related adverse events (FrAE) is controversial. Here, we explored the prevalence and clinical relevance of 2R/2R TYMSgenotype. Methods: Between 2011 and 2018, 126 patients were genotyped for TYMS. FrAEs were graded according to CTCAE version 5.0. Fisher’s exact test was used for statistical analysis. Results: The prevalence of TYMS 2R/2Rgenotype was 24.6%. Among patients with TYMS genotypes (N= 71) that predict decreased TS expression, 2R/2R TYMSgenotype was the most common TYMSgenotype seen in female (57%) and African American (60%) patients. Among patients with genotypes that predict increased TS expression (N= 55), 12 patients had grade 3–4 FrAEs (22%), while among patients with genotypes that predict decreased TS expression (N= 71), 30 patients had grade 3–4 FrAEs (42%) (p= 0.0219). Compared to patients with genotypes predicting increased TS expression, 17 out of 31 patients (55%) with TYMS 2R/2Rgenotype had grade 3–4 FrAEs (p= 0.0039) and 15 out 40 patients (38%) with TYMS 2R/3RCand TYMS 3RC/3RCgenotype had grade 3–4 FrAEs (p= 0.1108). Conclusion: The prevalence of TYMS 2R/2Rgenotype was 24.6%, and it had a unique sex and ethnic distribution. Polymorphism in the promoter region of TYMSgene that predicts decreased TS expression due to 2R/2Rvariant was associated with grade 3–4 FrAEs. These data suggest that genotyping patients who are not DPD deficient for TYMS might identify patients at risk of severe FrAEs.

Pharmacogenetic testing increasingly is available from clinical and research laboratories. However, only a limited number of quality control and other reference materials currently are available for the complex rearrangements and rare variants that occur in the CYP2D6gene. To address this need, the Division of Laboratory Systems, CDC-based Genetic Testing Reference Material Coordination Program, in collaboration with members of the pharmacogenetic testing and research communities and the Coriell Cell Repositories (Camden, NJ), has characterized 179 DNA samples derived from Coriell cell lines. Testing included the recharacterization of 137 genomic DNAs that were genotyped in previous Genetic Testing Reference Material Coordination Program studies and 42 additional samples that had not been characterized previously. DNA samples were distributed to volunteer testing laboratories for genotyping using a variety of commercially available and laboratory-developed tests. These publicly available samples will support the quality-assurance and quality-control programs of clinical laboratories performing CYP2D6testing.

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A method for qualitative detection of 57 drugs and metabolites in umbilical cord tissue using liquid chromatography time-of-flight (TOF) mass spectrometry is described.

The immunosuppressant everolimus was recently approved for prophylactic use in the United States, to prevent organ rejection in adult kidney transplant recipients. The currently accepted therapeutic range for everolimus is 3–8 ngmL. Therapeutic drug monitoring (TDM) using predose EDTA whole blood samples is required to optimize dose. We describe a simple extraction method and analysis by liquid chromatography tandem mass spectrometry (LC-MSMS) to support routine TDM of everolimus. Samples were prepared by protein precipitation and filtration. The first quadrupole was set to select the ammonium adducts

Sirolimus is indicated for prophylaxis treatment to prevent solid organ rejection. Due to intrapatient and interpatient variabilities in pharmacokinetics, risk of concentration-related toxicity, risk of noncompliance, and a high likelihood of drug-drug interactions, therapeutic drug monitoring of sirolimus is essential. There are several methodologies used clinically to monitor sirolimus, ranging from immunoassay to tandem mass spectrometry, each with potential strengths and limitations. The purpose of our study was to validate the Abbott ARCHITECT i2000 sirolimus assay.

Gabapentin is an antiepileptic drug used as adjunct therapy in the treatment of seizures. Absorption is saturable, and drug clearance can be reduced if patients have impaired renal function. Therapeutic drug monitoring can be useful for optimizing the dose in patients with impaired renal function, for evaluating individual patient absorption thresholds, and for monitoring compliance. Although chromatographic techniques have historically been used to support gabapentin monitoring, an immunoassay was recently introduced by ARK Diagnostics, for use with open channel chemistry analyzers. Here, we evaluated the immunoassay on a random access instrument.

Recent genome-wide association studies have identified two host single-nucleotide polymorphisms (SNPs) near the IL28Bgene (rs12979860C/T and rs8099917T/G) that are associated with sustained virological response in patients infected with the hepatitis C virus. Herein, we describe a rapid multiplexed dual-color fluorescence resonance energy transfer (FRET) probe assay that accurately genotypes for both SNPs simultaneously. A single-nucleotide extension assay was also developed for verification of genotypes. Agreement (100%) was observed in genotype calls between the FRET and single-nucleotide extension methods for both SNPs, yielding 100% analytical sensitivity and specificity. By using the FRET assay, 443 samples of varying ethnic backgrounds were genotyped and six different compound genotypes (rs12979860/rs8099917) were detected in whites, Asians, Middle Easterners, Hispanics, and African Americans, at the following frequencies: CC/TT (39.2%, 78.9%, 40.0%, 33.9%, and 16.8%), CT/TT (20.8%, 0%, 40%, 9.3%, and 37.0%), TT/TT (2.4%, 0%, 0%, 3.4%, and 35.3%), CT/TG (24.0%, 19.7%, 20%, 39.8%, and 3.4%), TT/TG (8.0%, 1.4%, 0%, 3.4%, and 5.9%), and TT/GG (5.6%, 0%, 0%, 10.2%, and 1.7%), respectively. The multiplexed FRET assay can be used to effectively genotype for both SNPs in a single tube, with high analytical sensitivity and specificity.

Busulfan is a chemotherapeutic agent commonly used for myeloablative conditioning regimens such as in the treatment of chronic myelogenous leukemia. Busulfan dosing is complex due to wide interpatient variability in pharmacokinetics and a narrow therapeutic range. Although busulfan dose is normalized to body weight, therapeutic drug monitoring (TDM) using area under the plasma concentration curve is recommended after the first dose. A high busulfan area under the plasma concentration curve (>1500 μM·min) is associated with an increased risk for sinusoidal obstruction syndrome, and a suboptimal area under the plasma concentration curve (<900 μM·min) is associated with an increased risk for graft rejection or disease relapse. TDM of busulfan is not widely available due to the lack of commercially available and rapid methods to determine the area under the plasma concentration curve.

Gabapentin (Neurontin) and levetiracetam (Keppra) are anticonvulsants with novel structures and suggested therapeutic ranges of 2-10 mg/L and 6-20 mg/L, respectively. Gabapentin is also used extensively to manage neuropathic pain, and for this indication, wherein higher doses are prescribed, plasma concentrations of 15-30 mg/L are typical.

Umbilical cord tissue was studied as a means of detecting prenatal exposure to nicotine. This was accomplished by comparing the presence and concentration of nicotine as well as nicotine metabolites in both umbilical cord tissue and paired meconium samples with maternal smoking histories obtained by self-report. Nicotine and metabolites (cotinine, 3-hydroxycotinine, nornicotine, and anabasine) were detected and quantitated using liquid chromatography-tandem mass spectroscopy. Between June and September 2009, 19 women with a tobacco exposure history (either first- or second-hand tobacco smoke exposure during pregnancy) were consented for the study. A questionnaire was completed to document nicotine exposure during each trimester of pregnancy. All infants were delivered at term (38 weeks or greater) and paired umbilical cord tissue (10-cm segment or greater) and meconium were obtained. Nicotine and 3-hydroxycotinine were most prominent in meconium, whereas cotinine and 3-hydroxycotinine were most prominent in the umbilical cord. Concentrations of all three analytes were generally higher in meconium. Nornicotine was detected only in meconium, at very low concentrations, and anabasine was not detected in either specimen. All analyte concentrations were lowest when the mother stated she quit smoking early in pregnancy or had only second-hand exposure, and detection was poor if exposure was limited to the first or second trimesters. Although different nicotine and metabolite patterns exist in meconium versus umbilical cord tissue, this work indicates that either specimen can be used to detect third-trimester fetal nicotine exposure.

Warfarin remains a difficult drug to manage due to a narrow therapeutic range and wide interindividual variability in dose requirements. The relationship between warfarin sensitivity and CYP2C9and VKORC1variants is strong, and is the basis for several proposed dosing algorithms. Here a gene-based dosing algorithm was compared with standard of care dosing in patients receiving warfarin to prevent venous thromboembolism after joint replacement surgery. Participants (n = 229) were adults (≥18 years) undergoing elective total hip or knee arthroplasty and receiving warfarin under the direction of a dedicated anticoagulation services team. Patients were assigned to genotype-based or standard of care dosing arms in an alternating fashion. Initial dose for patients was determined by validated algorithms from Sconce 2005 and Pendleton 2008. Management was based on INR, but dose was adjusted less aggressively for patients with CYP2C9variants. The primary endpoint was reduction in the incidence of adverse events; additional endpoints included time to first therapeutic INR (1.8-2.9), time to first supratherapeutic INR, and percent of INR determinations that fell below, within, and above the therapeutic range. Endpoints did not achieve statistical significance, possibly due to the management of this study by a dedicated and experienced anticoagulation services team. Trends in the data suggest that patients with genetic variants progressed to a therapeutic INR faster than patients in whom genetic variants were not detected, and there were fewer adverse events in the genotype-based dosing arm. In addition, the results of this study confirm those of others demonstrating clear relationship of genotype for CYP2C9and VKORC1with warfarin dose requirements; as the number of variants in these genes increases, the dose requirement decreases. Of note, the gene-based algorithm utilized here significantly underpredicted the dose requirement for participants with no variants, indicating that patients with no variants should be managed with a different algorithm than patients who inherit genetic variants in CYP2C9and/or VKORC1. In conclusion, gene-based dosing did not improve warfarin management as defined by INR dose response, using the described protocols for implementation. Findings suggest alternative strategies for dosing based on the presence or absence of genetic variants is needed.

High-dose busulfan is an important component of many bone marrow transplantation-preparative regimens. High busulfan plasma levels have been shown to increase the chance of venoocclusive disease and low levels are associated with recurrence of disease or graft rejection. Currently, busulfan levels are monitored by physical methods that are expensive and time consuming, resulting in relatively low overall use of busulfan testing for dose adjustment. Novel highly selective antibodies for busulfan have been generated and a microtiter plate immunoassay capable of quantifying busulfan levels in plasma has been developed. The assay was configured using a busulfan-horseradish peroxidase (HRP) conjugate as the reporter group and busulfan monoclonal antibodies. The assay requires 30 μL of plasma with no sample preparation. The immunoassay has a standard curve based on busulfan with a range of 75-2000 ng/mL. The time to first result is 30 minutes with up to 40 patient samples in duplicate; multiple plates can be run at once. The coefficient of variation (CV) on signal is <5% for an entire plate, and the 95% confidence interval for negative samples (n = 78) is below the lowest calibrator of 75 ng/mL. Cross-reactivity with the major inactive metabolites (tetrahydrothiophene, tetramethyl sulfone, and tetrahydrothiophene-3-ol-1,1-dioxide) was <0.1%. Results generated with clinical samples (n = 35 and n = 70) correlate well to gas chromatography-mass spectrometry (R= 0.976 and 0.985, respectively) with a slope of 1.05 ± 0.05. This immunoassay method is suitable for determining levels of busulfan in human plasma. It offers the advantages of using a smaller sample size, does not require sample preparation, and is less labor intensive than other methods. The ability to make 240 determinations per hour enables effective and timely routine monitoring of busulfan levels in clinical practice.

No relevant conflicts of interest to declare.

Background:Generic imatinib mesylate (IM) is an effective therapy and is the least costly tyrosine kinase inhibitor (TKI) for patients with chronic myeloid leukemia (CML). Therapeutic drug monitoring (TDM) has the potential to improve the adherence to IM therapy as well as helps oncologists to make an informed decision. This eventually leads a delayed switching to 2ndor 3rdgeneration (2G or 3G) TKIs that dramatically increase the treatment cost. The objective of this study was to determine the short- and lifetime cost-effectiveness of TDM for generic IM administration in patients newly diagnosed with CML.

Imatinib mesylate is a first-line tyrosine kinase inhibitor used for the treatment of chronic myeloid leukemia (CML). Therapeutic drug monitoring (TDM) of imatinib is an important tool for evaluating patient adherence to therapy, particularly in the setting of therapeutic failure, and for dose optimization. It has been proposed that the therapeutic range for pre-dose (trough) plasma imatinib concentration (C₀) is 1000 - 3000 ng/mL (Biol Pharm Bull 38:645-54, 2015). TDM for imatinib is not widely available in the United States. Automated analysis of imatinib concentrations in plasma may improve accessibility of testing to support routine TDM.

This article describes a rapid high-performance liquid chromatographic (HPLC) method for the measurement of the primary metabolite of oxcarbazepine. Following a simple precipitation step, 10,11,-dihydro-10-hydroxy-5H-dibenzo(b,f)azepine-5-carboxamide is quantitated (5–60 µg/mL) by analysis on an HPLC-UV system. The instrument time is less than 5 min per injection, an improvement over most published methods. The assays limit of quantitation, linearity, imprecision, and accuracy adequately cover the therapeutic range for appropriate patient monitoring. In comparison to other published methods, this procedure would be of interest to clinical laboratories because it employs a precipitation step for sample preparation, instead of conventional yet time-consuming solid-phase extraction.