Clinical Pharmacogenetics Implementation Consortium (CPIC) Guideline for CYP2C9 and HLA-B Genotypes and Phenytoin Dosing: 2020 Update

Cytochrome P450 phenotyping using the Geneva cocktail improves metabolic capacity prediction in a hospitalized patient population

AIMS

Liver cytochromes (CYPs) play an important role in drug metabolism but display a large interindividual variability resulting both from genetic and environmental factors. Most drug dose adjustment guidelines are based on genetics performed in healthy volunteers. However, hospitalized patients are not only more likely to be the target of new prescriptions and drug treatment modifications than healthy volunteers, but will also be more subject to polypharmacy, drug-drug interactions, or to suffer from disease or inflammation affecting CYP activities.

METHODS

We compared predicted phenotype based on genetic data and measured phenotype using the Geneva cocktail to determine the extent of drug metabolizing enzyme variability in a large population of hospitalized patients (>500) and healthy young volunteers (>300). We aimed to assess the correlation between predicted and measured phenotype in the two populations.

RESULTS

We found that, even in cases where the genetically predicted metabolizer group correlates well with measured CYP activity at group level, this prediction lacks accuracy for the determination of individual metabolizer capacities. Drugs can have a profound impact on CYP activity, but even after combining genetic and drug treatment information, the activity of a significant proportion of extreme metabolizers could not be explained.

CONCLUSIONS

Our results support the use of measured metabolic ratios in addition to genotyping for accurate determination of individual metabolic capacities to guide personalized drug prescription.

Pre-emptive pharmacogenetic testing in the acute hospital setting: a cross-sectional study

BACKGROUND

Pharmacogenetic-guided prescribing can be used to improve the safety and effectiveness of medicines. There are several approaches by which this intervention might be implemented in clinical practice, which will vary depending on the health system and clinical context.

AIM

To understand the clinical utility of panel-based pharmacogenetic testing in patients admitted acutely to hospital and to establish variables that predict if an individual might benefit from the intervention.

DESIGN

A cross-sectional study recruiting patients admitted acutely to hospital.

METHODS

Participants underwent panel-based pharmacogenetic testing, and their genetic results were analysed in their context of the medicines they had been exposed to as an inpatient. The primary outcome was the proportion of patients with clinically actionable gene-drug interactions. Individual variables that predict the clinical utility of pharmacogenetic testing were established via logistic regression.

RESULTS

Genetic and prescribing data were available for 482 inpatients (55% male; median age 61.2 years; range: 18-96), 97.9% of whom carried a pharmacogenetic result of interest. During their admission, 79.5% of patients were exposed to a medicine for which there is pharmacogenetic prescribing guidance available. Just under one in seven individuals (13.7%) had a clinically actionable gene-drug interaction. Increasing age (>50 years) was positively correlated with the likelihood (2.7-fold increased risk) of having a clinically actionable interaction.

CONCLUSIONS

These findings demonstrate the potential scale, and potential clinical utility, of pharmacogenetic testing as an intervention, highlighting the need to develop infrastructure to support healthcare professionals make use of this emerging tool.

The association between the number of HLA risk alleles and drug allergy and its implications for HLA screening - a case-control study

Patients carrying specific HLA risk alleles are at higher risk for developing drug hypersensitivity reactions, yet pre-therapeutic screening is uncommon. We examined whether patients with a history of drug allergies have more HLA risk alleles to assess whether these patients are potential candidates for pre-therapeutic HLA screening. We performed a case-control study with patients who had a self-reported history of drug allergy (N = 94) and patients without such a history (N = 185). HLA regions were sequenced by use of Alloseq Tx for HLA-A -B, -C, -DP, -DQ and -DR genotypes. A logistic regression was performed to investigate whether the number of HLA risk alleles differed between cases and controls. Sequencing data of 279 patients were available for this analysis. There was no statistically significant difference in the mean number of unique HLA risk alleles between the cases and controls (5.31 vs 5.31, p = 0.9397). Therefore, patients with a self-reported history of drug allergy do not form a suitable group for pre-therapeutic screening for HLA risk alleles to prevent future drug allergies.

Value of Pharmacogenetic Testing Assessed with Real-World Drug Utilization and Genotype Data

Implementation of pharmacogenetic testing in clinical care has been slow and with few exceptions is hindered by the lack of real-world evidence on how to best target testing. In this retrospective register-based study, we analyzed a nationwide cohort of 1,425,000 patients discharged from internal medicine or surgical wards and a cohort of 2,178 university hospital patients for purchases and prescriptions of pharmacogenetically actionable drugs. Pharmacogenetic variants were obtained from whole genome genotype data for a subset (n = 930) of the university hospital patients. We investigated factors associated with receiving pharmacogenetically actionable drugs and developed a literature-based cost-benefit model for pre-emptive pharmacogenetic panel testing. In a 2-year follow-up, 60.4% of the patients in the nationwide cohort purchased at least one pharmacogenetically actionable drug, most commonly ibuprofen (25.0%) and codeine (19.4%). Of the genotyped subset, 98.8% carried at least one actionable pharmacogenetic genotype and 23.3% had at least one actionable gene-drug pair. Patients suffering from musculoskeletal or cardiovascular diseases were more prone to receive pharmacogenetically actionable drugs during inpatient episode. The cost-benefit model included frequently dispensed drugs in the university hospital cohort, comprising ondansetron (19.4%), simvastatin (7.4%), clopidogrel (5.0%), warfarin (5.1%), (es)citalopram (5.3%), and azathioprine (0.5%). For untargeted pre-emptive pharmacogenetic testing of all university hospital patients, the model indicated saving €17.49 in direct healthcare system costs per patient in 2 years without accounting for the cost of the test itself. Therefore, it might be reasonable to target pre-emptive pharmacogenetic testing to patient groups most likely to receive pharmacogenetically actionable drugs.

Pharmacogenetics: Opportunities for the All of Us Research Program and Other Large Data Sets to Advance the Field

Pharmacogenetic variation is common and an established driver of response for many drugs. There has been tremendous progress in pharmacogenetics knowledge over the last 30 years and in clinical implementation of that knowledge over the last 15 years. But there have also been many examples where translation has stalled because of the lack of available data sets for discovery or validation research. The recent availability of data from very large cohorts with linked genetic, electronic health record, and other data promises new opportunities to advance pharmacogenetics research. This review presents the stages from pharmacogenetics discovery to widespread clinical adoption using prominent gene-drug pairs that have been implemented into clinical practice as examples. We discuss the opportunities that the All of Us Research Program and other large biorepositories with genomic and linked electronic health record data present in advancing and accelerating the translation of pharmacogenetics into clinical practice.

The relationship between CYP2C9 gene polymorphisms and azilsartan metabolism in vitro

BACKGROUND

The gene polymorphisms of the CYP2C9, as well as the substrate specificity of the enzyme, result in different clearances for different substrates by CYP2C9 variants.

RESEARCH DESIGNAND METHODS

The CYP2C9 wild type and 38 CYP2C9 variants, expressed in insectmicrosomes, were incubated with azilsartan. The resulting metabolite,O-desethyl azilsartan, was determined by HPLC-MS/MS. The enzyme kineticparameters of the 38 variants were calculated and compared with the wild type.Subsequently, we selected CYP2C9*1, *2, and  *3 as target proteins for molecular docking with azilsartan to elucidate the mechanisms underlying changes in enzyme function.

RESULTS

Compared with CYP2C9*1, three variants (CYP2C9*29, *39, and *49) exhibited markedlyincreased CLint values (from 170%-275%, *p < 0.05), whereas 28 variants exhibited significantly decreased CLint values (from 3-63%,*p < 0.05). The molecular docking results showed that the binding energy of CYP2C9*2 and *3 was lower than that of the wild type.

CONCLUSION

Thisassessment revealed the effect of CYP2C9 gene polymorphisms on azilsartan metabolism, establishing a theoretical basis for further in-vivo studies and clinical applications. This study will help expand the database of CYP2C9 gene-drug pairs and identify appropriate treatment strategies for azilsartan, contributing to the field of precision medicine.

Pharmacogenomic profiling of the South Korean population: Insights and implications for personalized medicine

Adverse drug reactions (ADRs) pose substantial public health issues, necessitating population-specific characterization due to variations in pharmacogenes. This study delineates the pharmacogenomic (PGx) landscape of the South Korean (SKR) population, focusing on 21 core pharmacogenes. Whole genome sequencing (WGS) was conducted on 396 individuals, including 99 healthy volunteers, 95 patients with chronic diseases, 81 with colon cancer, 81 with breast cancer, and 40 with gastric cancer, to identify genotype-specific drug dosing recommendations. Our detailed analysis, utilizing high-throughput genotyping (HTG) of CYP2D6 and comparative data from the 1,000 Genomes Project (1 KG) and the US National Marrow Donor Program (NMDP), revealed significant pharmacogenetic diversity in core pharmacogenes such as CYP2B6, CYP2C19, CYP4F2, NUDT15, and CYP2D6. Notably, intermediate metabolizer frequencies for CYP2B6 in SKR (3.28%) were comparable to Europeans (5.77%) and East Asians (5.36%) but significantly differed from other global populations (p < 0.01). For CYP2C19, 48.74% of SKR individuals were classified as intermediate metabolizers, with the *35 allele (2.02%) being unique to SKR, the allele not observed in other East Asian populations. Additionally, the high-risk *3 allele in CYP4F2 was significantly more frequent in SKR (34.72%) than in other East Asian populations (p < 0.01). NUDT15 poor metabolizers were found in 0.76% of SKR, aligning closely with other East Asians (1.59%), while TPMT poor metabolizers were predominantly observed in Europeans and Africans, with one case in SKR. We identified significant allele frequency differences in CYP2D6 variants rs1065852 and rs1135840. Among the 72 drugs analyzed, 93.43% (n = 370) of patients required dosage adjustments for at least one drug, with an average of 4.5 drugs per patient. Moreover, 31.31% (n = 124) required adjustments for more than five drugs. These findings reveal the substantial pharmacogenetic diversity of the SKR population within the global population, emphasizing the urgency of integrating population-specific PGx data into clinical practice to ensure safe and effective drug therapies. This comprehensive PGx profiling in SKR not only advances personalized medicine but also holds the potential to significantly improve healthcare outcomes on a broader scale.

Influence of CYP2C9 phenotypes on phenytoin plasma concentration in neurosurgical Brazilian patients

AIMS

To investigate the association of CYP2C9 metabolic phenotypes with phenytoin plasma concentration ([PTH]) in neurosurgical patients from the Brazilian Public Health System.

METHODS

Patients (n = 170) were treated with phenytoin (300 mg/day) perioperatively as prophylaxis for postoperative seizures. Two to 10 days after surgery, a blood sample was collected for quantification of [PTH] and genotyping of CYP2C9*2 and *3 alleles. CYP2C9 metabolic phenotypes, NM (normal), IM (intermediate), and PM (poor) metabolizer, were inferred from CYP2C9 diplotypes. Linear regression modeling was applied to identify predictors of [PTH].

RESULTS

Wide (22-fold) interindividual variation in [PTH] was observed (2.2-47.5 mg/l). [PTH] associated significantly (Kruskal-Wallis P < 0.005) with CYP2C9 phenotypes and there was a significant trend (Jonckheere-Terpstra test, P < 0.0001) for [PTH] increase in the order NM < IM < PM. [PTH] was within the target therapeutic range (10-20 mg/l) in 34.7% of patients, while 39.4% and 25.9% had [PTH] below and above the range, respectively. CYP2C9 phenotypes associated significantly (chi-square P = 0.004) with the distribution of patients in [PHT] therapeutic categories and the Cramér's V test pointed to moderate magnitude of the effect of CYP2C9 phenotypes (V = 0.211).

CONCLUSION

Diplotype-predicted CYP2C9 metabolic phenotypes are associated significantly with [PTH] in neurosurgical Brazilian patients receiving phenytoin for postsurgery seizure prophylaxis. [PHT] increased progressively in the phenotype order NM < IM < PM, and all PM patients had [PHT] above the target therapeutic range, consistent with the CPIC guideline 'strong' recommendation for phenytoin dosing adjustments in PMs.

Pharmacogenomic insights in psychiatric care: uncovering novel actionability, allele-specific CYP2D6 copy number variation, and phenoconversion in 15,000 patients

Pharmacogenomic testing has emerged as an aid in clinical decision making for psychiatric providers, but more data is needed regarding its utility in clinical practice and potential impact on patient care. In this cross-sectional study, we determined the real-world prevalence of pharmacogenomic actionability in patients receiving psychiatric care. Potential actionability was based on the prevalence of CYP2C19 and CYP2D6 phenotypes, including CYP2D6 allele-specific copy number variations (CNVs). Combined actionability additionally incorporated CYP2D6 phenoconversion and the novel CYP2C-TG haplotype in patients with available medication data. Across 15,000 patients receiving clinical pharmacogenomic testing, 65% had potentially actionable CYP2D6 and CYP2C19 phenotypes, and phenotype assignment was impacted by CYP2D6 allele-specific CNVs in 2% of all patients. Of 4114 patients with medication data, 42% had CYP2D6 phenoconversion from drug interactions and 20% carried a novel CYP2C haplotype potentially altering actionability. A total of 87% had some form of potential actionability from genetic findings and/or phenoconversion. Genetic variation detected via next-generation sequencing led to phenotype reassignment in 22% of individuals overall (2% in CYP2D6 and 20% in CYP2C19). Ultimately, pharmacogenomic testing using next-generation sequencing identified potential actionability in most patients receiving psychiatric care. Early pharmacogenomic testing may provide actionable insights to aid clinicians in drug prescribing to optimize psychiatric care.

[Pharmaceutical Indication Service in a case of palmar-plantar erythema after amoxicillin and ibuprofen treatment]

Case description

Patient (29 years old) with palmo-plantar erythema, goes to the community pharmacy (FC) requesting a cream to treat atopy.

Evaluation

The patient accessed the Pharmaceutical Indication Service (SPIF), showing that the manifestations appeared 24 hours after the start of dental treatment with amoxicillin 1g/12h and ibuprofen 600 mg/8h without any concomitant medication.

Intervention

After explaining the possible relationship of the symptoms with their medication, patient was derived to the doctor with the referral report completed by SEFAC-eXPERT.

Results

The patient went to the emergency where she was treated with intravenous corticosteroid and a prescription for cetirizine 10 mg. The dentist changed the beta-lactam to a macrolide (azithromycin) and the ibuprofen to paracetamol. From the FC, the evolution of the symptoms was monitored, which took 72 hours to disappear. Allergy tests suggested avoiding beta-lactams, cephalosporins, and arylpropionics without being conclusive. Months later, the patient suffered similar symptoms after inhaling a disinfectant spray and the allergy diagnosis was confirmed.

Conclusions

The FC identified and immediately referred using SPIF a case of hypersensitivity in a patient susceptible to RNM and the SPIF helps to record the intervention and follow-up, increasing patient safety.

[Selection of pharmacogenomic variants and methodology for their use in community pharmacy]

Regulatory agencies such as the Food and Drug Administration (FDA) and the European Medicines Agency (EMA) recognize pharmacogenetics as a key tool in their pharmacological guidelines for pharmaceutical counseling. In this context, community pharmacies play a crucial role in addressing this healthcare need, which could lead to a significant improvement in patients' quality of life by preventing ineffective or contraindicated treatments.In this work, we conducted a systematic review of the available scientific evidence regarding druggene interactions relevant to community pharmacy. We identified the main genes and polymorphisms associated with treatment response and adverse effects in primary care. Finally, we propose a model for implementing pharmacogenetic services in community pharmacies.

Patterns of pharmacogenetic variation in nine biogeographic groups

Frequencies of pharmacogenetic (PGx) variants are known to differ substantially across populations but much of the available PGx literature focuses on one or a few population groups, often defined in nonstandardized ways, or on a specific gene or variant. Guidelines produced by the Clinical Pharmacogenetic Implementation Consortium (CPIC) provide consistent methods of literature extraction, curation, and reporting, including comprehensive curation of allele frequency data across nine defined "biogeographic groups" from the PGx literature. We extracted data from 23 CPIC guidelines encompassing 19 genes to compare the sizes of the populations from each group and allele frequencies of altered function alleles across groups. The European group was the largest in the curated literature for 16 of the 19 genes, while the American and Oceanian groups were the smallest. Nearly 200 alleles were detected in nonreference groups that were not reported in the largest (reference) group. The genes CYP2B6 and CYP2C9 were more likely to have higher frequencies of altered function alleles in nonreference groups compared to the reference group, while the genes CYP4F2, DPYD, SLCO1B1, and UGT1A1 were less likely to have higher frequencies in nonreference groups. PGx allele frequencies and function differ substantially across nine biogeographic groups, all but two of which are underrepresented in available PGx data. Awareness of these differences and increased efforts to characterize the breadth of global PGx variation are needed to ensure that implementation of PGx-guided drug selection does not further widen existing health disparities among populations currently underrepresented in PGx data.

Challenges and prospects in bridging precision medicine and artificial intelligence in genomic psychiatric treatment

Precision medicine is transforming psychiatric treatment by tailoring personalized healthcare interventions based on clinical, genetic, environmental, and lifestyle factors to optimize medication management. This study investigates how artificial intelligence (AI) and machine learning (ML) can address key challenges in integrating pharmacogenomics (PGx) into psychiatric care. In this integration, AI analyzes vast genomic datasets to identify genetic markers linked to psychiatric conditions. AI-driven models integrating genomic, clinical, and demographic data demonstrated high accuracy in predicting treatment outcomes for major depressive disorder and bipolar disorder. This study also examines the pressing challenges and provides strategic directions for integrating AI and ML in genomic psychiatry, highlighting the importance of ethical considerations and the need for personalized treatment. Effective implementation of AI-driven clinical decision support systems within electronic health records is crucial for translating PGx into routine psychiatric care. Future research should focus on developing enhanced AI-driven predictive models, privacy-preserving data exchange, and robust informatics systems to optimize patient outcomes and advance precision medicine in psychiatry.

Investigating the Correlation between Genotypes and Hepatic Protein Expression of CYP2C9, CYP2C19, CYP2D6, and CYP3A5 Using Postmortem Tissue from a Danish Population

The cytochrome P450 (CYP) family of enzymes plays a central role in the metabolism of many drugs. CYP genes are highly polymorphic, which is known to affect protein levels, but for some low frequent CYP genotypes the correlation between genotype and CYP protein expression is less established. In this study, we determined the CYP2C9, CYP2C19, CYP2D6, and CYP3A5 genotypes of 250 Danish individuals included in a postmortem study. For 116 of the individuals, the hepatic CYP protein levels were investigated by a proteomics approach. Overall, we found the postmortem genetic and proteomic data to be in agreement with those of other studies performed on fresh hepatic tissue, showing the usability of postmortem hepatic tissue for this type of investigation. For less investigated genotypes, we could corroborate previously found results: 1) statistically significantly lower levels of hepatic CYP2C9 protein in individuals carrying the CYP2C9*3 variant compared with individuals with two wild type (wt) alleles; 2) comparable levels of CYP2C19 in CYP2C19*2/*17 and CYP2C19*1/*2 individuals; 3) reduced CYP2D6 protein levels in heterozygous individuals with the CYP2D6*3, CYP2D6*4, and CYP2D6*5 gene deletion variants; and 4) significantly lower levels of CYP3A5 protein in CYP3A5*3 homozygous individuals compared with individuals who were heterozygous for the CYP3A5*3 allele or homozygous individuals for the wt alleles. In conclusion, the use of postmortem tissue significantly increases the access to human specimens for research purposes, and postmortem proteomics can be used to investigate the link between CYP genotypes and hepatic protein expression. SIGNIFICANCE STATEMENT: In tissue samples from a large postmortem cohort (n = 250) we determined the CYP2C9, CYP2C19, CYP2D6, and CYP3A5 genotypes. Hepatic CYP protein levels were investigated in 116 individuals using a proteomics approach. For common genotypes, we found results similar to previous knowledge, pointing toward the usability of postmortem tissue. For the less investigated genotypes, we were able to corroborate genotype/protein expression correlations. It is a novel approach to use a large postmortem cohort to investigate genetic/protein expression correlations.

Dutch Pharmacogenetics Working Group (DPWG) guideline for the gene-drug interaction of CYP2C9, HLA-A and HLA-B with anti-epileptic drugs

By developing evidence-based pharmacogenetics guidelines to optimize pharmacotherapy, the Dutch Pharmacogenetics Working Group (DPWG) aims to advance the implementation of pharmacogenetics (PGx). This guideline outlines the gene-drug interaction of CYP2C9 and HLA-B with phenytoin, HLA-A and HLA-B with carbamazepine and HLA-B with oxcarbazepine and lamotrigine. A systematic review was performed and pharmacotherapeutic recommendations were developed. For CYP2C9 intermediate and poor metabolisers, the DPWG recommends lowering the daily dose of phenytoin and adjust based on effect and serum concentration after 7-10 days. For HLA-B*15:02 carriers, the risk of severe cutaneous adverse events associated with phenytoin, carbamazepine, oxcarbazepine, and lamotrigine is strongly increased. For carbamazepine, this risk is also increased in HLA-B*15:11 and HLA-A*31:01 carriers. For HLA-B*15:02, HLA-B*15:11 and HLA-A*31:01 positive patients, the DPWG recommends choosing an alternative anti-epileptic drug. If not possible, it is recommended to advise the patient to report any rash while using carbamazepine, lamotrigine, oxcarbazepine or phenytoin immediately. Carbamazepine should not be used in an HLA-B*15:02 positive patient. DPWG considers CYP2C9 genotyping before the start of phenytoin "essential" for toxicity prevention. For patients with an ancestry in which the abovementioned HLA-alleles are prevalent, the DPWG considers HLA-B*15:02 genotyping before the start of carbamazepine, phenytoin, oxcarbazepine, and lamotrigine "beneficial", as well as genotyping for HLA-B*15:11 and HLA-A*31:01 before initiating carbamazepine.

Implementation of pharmacogenomics: Where are we now?

Pharmacogenomics (PGx), examining the effect of genetic variation on interpatient variation in drug disposition and response, has been widely studied for several decades. However, as cost, as well as turnaround time associated with PGx testing, has significantly improved, the use of PGx in the clinical setting has been gaining momentum. Nevertheless, challenges have emerged in the broader clinical implementation of PGx. In this review, we will outline current models of PGx delivery and methodologies of evaluation, and discuss clinically relevant PGx tests and associated medications. Additionally, we will describe our approach for the broad implementation of pre-emptive DPYD genotyping in patients taking fluoropyrimidines in Ontario, Canada, as an example of clinically actionable PGx testing with sufficient clinical evidence of patient benefit that can become a new standard of patient care. We will highlight challenges associated with PGx testing, including a lack of diversity in PGx studies as well as general limitations that impact the broad adoption of PGx testing. Lastly, we examine the future of PGx, discussing new clinical targets, methodologies and analysis approaches.

Decoding Pharmacogenomic Test Interpretation and Application to Patient Care

Pharmacogenomics is a growing area of medicine, and pharmacists across clinical practice settings have the opportunity to individualize medication selection and dosing using genetic data. However, many practicing pharmacists may feel ill-equipped to interpret pharmacogenomic test results because of insufficient education and training. Evidence-based, updated, and freely available resources such as the Clinical Pharmacogenetics Implementation Consortium guidelines can help pharmacists interpret and apply pharmacogenomic test results to patient care. Although gaps for the application of pharmacogenomic information exist, this commentary aims to demystify the interpretation of pharmacogenomic test results and empower pharmacists to apply genetic data alongside other clinical variables to optimize medication-related outcomes for their patients. An "ABCD" framework is proposed to guide pharmacists through the steps: (1) Actionability - Are the gene(s) clinically relevant for the patient? (2) Be Mindful of Limitations - What are the caveats with pharmacogenomic test results and reports? (3) Clinical Practice Guidelines - How do you use pharmacogenomic test results to guide clinical decision-making? and (4) Document and Discuss - How do you educate the patient about their pharmacogenomic test results and document the results for future use? Key concepts are illustrated using a psychiatric patient case example.

Genetic diversity of cytochrome P450 in patients receiving psychiatric care in Greece: a step towards clinical implementation

Aim: We herein inferred the genetic diversity of CYP450 isoenzymes to predict the percentage of patients who need dose adjustment in drugs used in psychiatry.Materials & methods: Data of 784 Greek patients receiving psychiatric care who were genotyped for CYP2D6, CYP2C19, CYP1A2, CYP3A5 and CYP2C9 isoenzymes were inferred to gene-drug pairs according to the US FDA, Clinical Pharmacogenetics Implementation Consortium and Dutch Pharmacogenetics Working Group annotations and published literature.Results: Atypical metabolism was found for 36.8% of patients in CYP2D6, 49.2% in CYP2C19, 45% in CYP1A2, 16.7% in CYP3A5 and 41.8% in CYP2C9. Dosage adjustment need was estimated for 10.2% of venlafaxine, 10.0% of paroxetine, 6.4% of sertraline, 30.8% of citalopram, 52.1% of escitalopram, 18.2% of fluvoxamine, 54.1% of tricyclic antidepressants, 16.7% of zuclopenthixol, 10.6% of haloperidol and 13.3% of risperidone treated patients.Conclusion: Clinical psychiatric pharmacogenomic implementation holds promise to improve drug effectiveness and safety.

Drug-induced hypersensitivity syndrome/drug reaction with eosinophilia and systemic symptoms. Part II diagnosis and management

Drug-induced hypersensitivity syndrome, also known as drug reaction with eosinophilia and systemic symptoms, is a severe cutaneous adverse reaction characterized by an exanthem, fever, and hematologic and visceral organ involvement. The differential diagnosis includes other cutaneous adverse reactions, infections, inflammatory and autoimmune diseases, and neoplastic disorders. Three sets of diagnostic criteria have been proposed; however, consensus is lacking. The cornerstone of management is immediate discontinuation of the suspected drug culprit. Systemic corticosteroids remain first-line therapy, but the literature on steroid-sparing agents is expanding. Longitudinal evaluation for sequelae is recommended. Adjunctive tests for risk stratification and drug culprit identification remain under investigation. Part II of this continuing medical education activity begins by exploring the differential diagnosis and diagnosis of drug-induced hypersensitivity syndrome/drug reaction with eosinophilia and systemic symptoms and concludes with an evidence-based overview of evaluation and treatment.

Severe cutaneous adverse reactions

Severe cutaneous adverse reactions (SCARs), which include Stevens-Johnson syndrome and toxic epidermal necrolysis, drug reaction with eosinophilia and systemic symptoms (also known as drug-induced hypersensitivity syndrome), acute generalized exanthematous pustulosis, and generalized bullous fixed drug eruption, are life-threatening conditions. The pathogenesis of SCARs involves T cell receptors recognizing drug antigens presented by human leukocyte antigens, triggering the activation of distinct T cell subsets. These cells interact with keratinocytes and various immune cells, orchestrating cutaneous lesions and systemic manifestations. Genetic predisposition, impaired drug metabolism, viral reactivation or infections, and heterologous immunity influence SCAR development and clinical presentation. Specific genetic associations with distinct SCAR phenotypes have been identified, leading to the implementation of genetic screening before prescription in various countries to prevent SCARs. Whilst systemic corticosteroids and conventional immunomodulators have been the primary therapeutic agents, evolving strategies, including biologics and small molecules targeting tumour necrosis factor, different cytokines, or Janus kinase signalling pathways, signify a shift towards a precision management paradigm that considers individual clinical presentations.

Intranasal delivery of phenytoin loaded layered double hydroxide nanoparticles improves therapeutic effect on epileptic seizures

Improving the efficiency of antiseizure medication entering the brain is the key to reducing its peripheral toxicity. A combination of intranasal administration and nanomedicine presents a practical approach for treating epileptic seizures via bypassing the blood-brain barrier. In this study, phenytoin (PHT) loaded layered double hydroxide nanoparticles (BSA-LDHs-PHT) were fabricated via a coprecipitation - hydrothermal method for epileptic seizure control. In this study, we expound on the preparation method and characterization of BSA-LDHs-PHT. In-vitro drug release experiment shows both rapid and continuous drug release from BSA-LDHs-PHT, which is crucial for acute seizure control and chronic epilepsy therapy. In-vivo biodistribution assays after intranasal administration indicate excellent brain targeting ability of BSA-LDHs. Compared to BSA-Cyanine5.5, BSA-LDHs-Cyanine5.5 were associated with a higher brain/peripheral ratio across all tested time points. Following intranasal delivery with small doses of BSA-LDHs-PHT, the latency of seizures in the pentylenetetrazole-induced mouse models was effectively improved. Collectively, the present study successfully designed and applied BSA-LDHs-PHT as a promising strategy for treating epileptic seizures with an enhanced therapeutic effect.

Sources of pharmacokinetic and pharmacodynamic variability and clinical pharmacology studies of antiseizure medications in the pediatric population

Multiple treatment options exist for children with epilepsy, including surgery, dietary therapies, neurostimulation, and antiseizure medications (ASMs). ASMs are the first line of therapy, and more than 30 ASMs have U.S. Food and Drug Administration (FDA) approval for the treatment of various epilepsy and seizure types in children. Given the extensive FDA approval of ASMs in children, it is crucial to consider how the physiological and developmental changes throughout childhood may impact drug disposition. Various sources of pharmacokinetic (PK) variability from different extrinsic and intrinsic factors such as patients' size, age, drug-drug interactions, and drug formulation could result in suboptimal dosing of ASMs. Barriers exist to conducting clinical pharmacological studies in neonates, infants, and children due to ethical and practical reasons, limiting available data to fully characterize these drugs' disposition and better elucidate sources of PK variability. Modeling and simulation offer ways to circumvent traditional and intensive clinical pharmacology methods to address gaps in epilepsy and seizure management in children. This review discusses various physiological and developmental changes that influence the PK and pharmacodynamic (PD) variability of ASMs in children, and several key ASMs will be discussed in detail. We will also review novel trial designs in younger pediatric populations, highlight the role of extrapolation of efficacy in epilepsy, and the use of physiologically based PK modeling as a tool to investigate sources of PK/PD variability in children. Finally, we will conclude with current challenges and future directions for optimizing the efficacy and safety of these drugs across the pediatric age spectrum.

Investigating the genetic makeup of the major histocompatibility complex (MHC) in the United Arab Emirates population through next-generation sequencing

The Human leukocyte antigen (HLA) molecules are central to immune response and have associations with the phenotypes of various diseases and induced drug toxicity. Further, the role of HLA molecules in presenting antigens significantly affects the transplantation outcome. The objective of this study was to examine the extent of the diversity of HLA alleles in the population of the United Arab Emirates (UAE) using Next-Generation Sequencing methodologies and encompassing a larger cohort of individuals. A cohort of 570 unrelated healthy citizens of the UAE volunteered to provide samples for Whole Genome Sequencing and Whole Exome Sequencing. The definition of the HLA alleles was achieved through the application of the bioinformatics tools, HLA-LA and xHLA. Subsequently, the findings from this study were compared with other local and international datasets. A broad range of HLA alleles in the UAE population, of which some were previously unreported, was identified. A comparison with other populations confirmed the current population's unique intertwined genetic heritage while highlighting similarities with populations from the Middle East region. Some disease-associated HLA alleles were detected at a frequency of > 5%, such as HLA-B*51:01, HLA-DRB1*03:01, HLA-DRB1*15:01, and HLA-DQB1*02:01. The increase in allele homozygosity, especially for HLA class I genes, was identified in samples with a higher level of genome-wide homozygosity. This highlights a possible effect of consanguinity on the HLA homozygosity. The HLA allele distribution in the UAE population showcases a unique profile, underscoring the need for tailored databases for traditional activities such as unrelated transplant matching and for newer initiatives in precision medicine based on specific populations. This research is part of a concerted effort to improve the knowledge base, particularly in the fields of transplant medicine and investigating disease associations as well as in understanding human migration patterns within the Arabian Peninsula and surrounding regions.

Update on HLA-B*15:02 allele associated with adverse drug reactions

HLA alleles, part of the major histocompatibility complex, are strongly associated with adverse drug reactions (ADRs). This review focuses on HLA-B*15:02 and explores its association with ADRs in various ethnic populations and with different drugs, aiming to provide insights into the safe clinical use of drugs and minimize the occurrence of ADRs. Furthermore, the review explores the potential mechanisms by which HLA-B*15:02 may be associated with ADRs, aiming to gain new insights into drug modification and identification of haptens. In addition, it analyzes the frequency of the HLA-B*15:02, genotyping methods, cost-effectiveness and treatment measures for adverse reactions, thereby providing a theoretical basis for formulating clinical treatment plans.

Comparison of pharmacokinetics and safety between CE-fosphenytoin sodium, fosphenytoin sodium, and phenytoin sodium after intravenous and intramuscular administration in healthy volunteers

Background: Captisol®-enabled-fosphenytoin sodium (CE-fosphenytoin sodium) injection is a modified formulation of fosphenytoin sodium. Objective: We aim to compare the intravenous and intramuscular bioavailability and safety between CE-fosphenytoin sodium, fosphenytoin sodium (Cerebyx®), and phenytoin sodium (intravenous injection only). Methods: In pivotal study 1, 54 subjects were divided into three sequence groups that receive intravenous injection of 250 mg of phenytoin sodium equivalent (PE), CE-fosphenytoin sodium (T), or fosphenytoin sodium (R1) and 250 mg of phenytoin sodium (R2) in period 1. After a 14-day washout period, 36 subjects were randomized to two treatment sequence groups (T-R1 or R1-T, n = 18 per group) in period 2, in which the subjects who received R2 in period 1 were removed, those who received T in period 1 used R1 (T-R1), while those who previously received R1 used T (R1-T). In pivotal study 2, a single intramuscular dose of T (400 mg PE) or R1 (400 mg PE) was administered according to the individual sequential treatment assignment in each period. There was a washout (14 days) period before receiving the next period study drug. Results: T and R1 have similar pharmacokinetic characteristics regarding total and free phenytoin, showing bioequivalence of both drugs in the intravenous and intramuscular administration. The geometric mean ratio was close to 1 (0.98-1.06). The AUC of total and free phenytoin in subjects who intravenously received T and R1 was very similar to those who received R2, although their Cmax was lower than that of the subjects who received R2. Overall, treatment with T and R1 was safe and well-tolerated, without serious adverse events (SAEs) or grade III adverse events (AEs). With intravenous (i.v.) or intramuscular (i.m.) treatment, the incidence of drug-related AEs using T was similar to that using R1. Treatment with T and R1 had clearly superior tolerability than that with R2. Conclusion: CE-fosphenytoin sodium is a promising substitute for fosphenytoin sodium. Clinical Trial Registration: http://www.chinadrugtrials.org.cn/, CTR20202154 (11 November 2020).

Impact of Pharmacogenomics in Clinical Practice

Polymorphisms of genes encoding drug metabolizing enzymes and transporters can significantly modify pharmacokinetics, and this can be associated with significant differences in drug efficacy, safety, and tolerability. Moreover, genetic variants of some components of the immune system can explain clinically relevant drug-related adverse events. However, the implementation of drug dose individualization based on pharmacogenomics remains scarce. In this narrative review, the impact of genetic variations on the disposition, safety, and tolerability of the most commonly prescribed drugs is reported. Moreover, reasons for poor implementation of pharmacogenomics in everyday clinical settings are discussed. The literature analysis showed that knowledge of how genetic variations can modify the effectiveness, safety, and tolerability of a drug can lead to the adjustment of usually recommended drug dosages, improve effectiveness, and reduce drug-related adverse events. Despite some efforts to introduce pharmacogenomics in clinical practice, presently very few centers routinely use genetic tests as a guide for drug prescription. The education of health care professionals seems critical to keep pace with the rapidly evolving field of pharmacogenomics. Moreover, multimodal algorithms that incorporate both clinical and genetic factors in drug prescribing could significantly help in this regard. Obviously, further studies which definitively establish which genetic variations play a role in conditioning drug effectiveness and safety are needed. Many problems must be solved, but the advantages for human health fully justify all the efforts.

Personalized antiseizure medication therapy in critically ill adult patients

Precision medicine has the potential to have a significant impact on both drug development and patient care. It is crucial to not only provide prompt effective antiseizure treatment for critically ill patients after seizures start but also have a proactive mindset and concentrate on epileptogenesis and the underlying cause of the seizures or seizure disorders. Critical illness presents different treatment issues compared with the ambulatory population, which makes it challenging to choose the best antiseizure medications and to administer them at the right time and at the right dose. Since there is a paucity of information available on antiseizure medication dosing in critically ill patients, therapeutic drug monitoring is a useful tool for defining each patient's personal therapeutic range and assisting clinicians in decision-making. Use of pharmacogenomic information relating to pharmacokinetics, hepatic metabolism, and seizure etiology may improve safety and efficacy by individualizing therapy. Studies evaluating the clinical implementation of pharmacogenomic information at the point-of-care and identification of biomarkers are also needed. These studies may make it possible to avoid adverse drug reactions, maximize drug efficacy, reduce drug-drug interactions, and optimize medications for each individual patient. This review will discuss the available literature and provide future insights on precision medicine use with antiseizure therapy in critically ill adult patients.

Frequencies of pharmacogenomic alleles across biogeographic groups in a large-scale biobank

Pharmacogenomics (PGx) is an integral part of precision medicine and contributes to the maximization of drug efficacy and reduction of adverse drug event risk. Accurate information on PGx allele frequencies improves the implementation of PGx. Nonetheless, curating such information from published allele data is time and resource intensive. The limited number of allelic variants in most studies leads to an underestimation of certain alleles. We applied the Pharmacogenomics Clinical Annotation Tool (PharmCAT) on an integrated 200K UK Biobank genetic dataset (N = 200,044). Based on PharmCAT results, we estimated PGx frequencies (alleles, diplotypes, phenotypes, and activity scores) for 17 pharmacogenes in five biogeographic groups: European, Central/South Asian, East Asian, Afro-Caribbean, and Sub-Saharan African. PGx frequencies were distinct for each biogeographic group. Even biogeographic groups with similar proportions of phenotypes were driven by different sets of dominant PGx alleles. PharmCAT also identified "no-function" alleles that were rare or seldom tested in certain groups by previous studies, e.g., SLCO1B1∗31 in the Afro-Caribbean (3.0%) and Sub-Saharan African (3.9%) groups. Estimated PGx frequencies are disseminated via the PharmGKB (The Pharmacogenomics Knowledgebase: www.pharmgkb.org). We demonstrate that genetic biobanks such as the UK Biobank are a robust resource for estimating PGx frequencies. Improving our understanding of PGx allele and phenotype frequencies provides guidance for future PGx studies and clinical genetic test panel design, and better serves individuals from wider biogeographic backgrounds.

Implementation of Pharmacogenetics in First-Line Care: Evaluation of Its Use by General Practitioners

Pharmacogenetics (PGx) can explain/predict drug therapy outcomes. There is, however, unclarity about the use and usefulness of PGx in primary care. In this study, we investigated PGx tests ordered by general practitioners (GPs) in 2021 at Dept. Clinical Chemistry, Erasmus MC, and analyzed the gene tests ordered, drugs/drug groups, reasons for testing and single-gene versus panel testing. Additionally, a survey was sent to 90 GPs asking about their experiences and barriers to implementing PGx. In total, 1206 patients and 6300 PGx tests were requested by GPs. CYP2C19 was requested most frequently (17%), and clopidogrel was the most commonly indicated drug (23%). Regarding drug groups, antidepressants (51%) were the main driver for requesting PGx, followed by antihypertensives (26%). Side effects (79%) and non-response (27%) were the main indicators. Panel testing was preferred over single-gene testing. The survey revealed knowledge on when and how to use PGx as one of the main barriers. In conclusion, PGx is currently used by GPs in clinical practice in the Netherlands. Side effects are the main reason for testing, which mostly involves antidepressants. Lack of knowledge is indicated as a major barrier, indicating the need for more education on PGx for GPs.

Identification of Drugs Acting as Perpetrators in Common Drug Interactions in a Cohort of Geriatric Patients from Southern Italy and Analysis of the Gene Polymorphisms That Affect Their Interacting Potential

BACKGROUND

Pharmacogenomic factors affect the susceptibility to drug-drug interactions (DDI). We identified drug interaction perpetrators among the drugs prescribed to a cohort of 290 older adults and analysed the prevalence of gene polymorphisms that can increase their interacting potential. We also pinpointed clinical decision support systems (CDSSs) that incorporate pharmacogenomic factors in DDI risk evaluation.

METHODS

Perpetrator drugs were identified using the Drug Interactions Flockhart Table, the DRUGBANK website, and the Mayo Clinic Pharmacogenomics Association Table. Allelic variants affecting their activity were identified with the PharmVar, PharmGKB, dbSNP, ensembl and 1000 genome databases.

RESULTS

Amiodarone, amlodipine, atorvastatin, digoxin, esomperazole, omeprazole, pantoprazole, simvastatin and rosuvastatin were perpetrator drugs prescribed to >5% of our patients. Few allelic variants affecting their perpetrator activity showed a prevalence >2% in the European population: CYP3A4/5*22, *1G, *3, CYP2C9*2 and *3, CYP2C19*17 and *2, CYP2D6*4, *41, *5, *10 and *9 and SLC1B1*15 and *5. Few commercial CDSS include pharmacogenomic factors in DDI-risk evaluation and none of them was designed for use in older adults.

CONCLUSIONS

We provided a list of the allelic variants influencing the activity of drug perpetrators in older adults which should be included in pharmacogenomics-oriented CDSSs to be used in geriatric medicine.

Pharmacogenomic implications of the differential distribution of CYP2C9 metabolic phenotypes among Latin American populations

The CYP2C9 gene encodes the major drug metabolism enzyme CYP2C9. This gene is highly polymorphic, and no-function (CYP2C9*3) plus decreased function (CYP2C9*2, *5, *8 and *11) star alleles (haplotypes) are commonly used to predict CYP2C9 metabolic phenotypes. This study explores the pharmacogenomic implications of the differential distribution of genotype-predicted CYP2C9 phenotypes across Latin American populations. Data from 1,404 individuals from the South American countries Brazil, Colombia and Peru, from Puerto Rico in the Caribbean and from persons with Mexican ancestry living in North America were analysed. The results showed that the distribution of CYP2C9 alleles and diplotypes, and diplotype-predicted CYP2C9 phenotypes vary significantly across the distinct country cohorts, as well as among self-identified White, Brown and Black Brazilians. Differences in average proportions of biogeographical ancestry across the study groups, especially Native American and African ancestry, are the likely explanation for these results. The differential distribution of genotype-predicted CYP2C9 phenotypes has potentially clinically-relevant pharmacogenomic implications, through its influence on the proportion of individuals at high risk for adverse response to medications that are CYP2C9 substrates, the proportion on individuals with CPIC therapeutic recommendations for dosing and choice of nonsteroidal antinflammatory drugs (NSAIDs) and the number of individuals that need to be genotyped in order to prevent adverse effects of NSAIDs. Collectively, these findings are likely to impact the perceived benefits, cost-effectiveness and clinical adoption of pharmacogenomic screening for drugs that are predominantly metabolized by CYP2C9.

Pharmacogenomics in the Management of Pulmonary Arterial Hypertension: Current Perspectives

Pulmonary arterial hypertension (PAH) is a rare disease with heterogeneous causes that can lead to right ventricular (RV) failure and death if left untreated. There are currently 10 medications representative of five unique pharmacologic classes that are approved for treatment. These have led to significant improvements in overall clinical outcome. However, substantial variability in dosing requirements and treatment response is evident, leading to suboptimal outcome for many patients. Furthermore, dosing is empiric and iterative and can lead to delays in meeting treatment goals and burdensome adverse effects. Pharmacogenomic (PGx) associations have been reported with certain PAH medications, such as treprostinil and bosentan, and can explain some of the variability in response. Relevant genes associated with treprostinil include CYP2C8, CYP2C9, CAMK2D, and PFAS. CYP2C8 and CYP2C9 are the genes encoding the major metabolizing liver enzymes for treprostinil, and reduced function variants (*2, *3) with CYP2C9 were associated with lower treatment persistence. Additionally, a higher CYP2C9 activity score was associated with a significantly less risk of treatment discontinuation. Other genes of interest that have been explored with treprostinil include CAMK2D, which is associated with right ventricular dysfunction and significantly higher dose requirements. Similarly, PFAS is associated with lower concentrations of cyclic adenosine monophosphate and significantly higher dose requirements. Genes of interest with the endothelin receptor antagonist (ERA) class include GNG2 and CYP2C9. A genetic variant in GNG2 (rs11157866) was linked to a significantly increased rate of clinical improvement with ERAs. The *2 variant with CYP2C9 (encoding for the major metabolizing enzyme for bosentan) was significantly associated with a higher risk for elevations in hepatic aminotransferases and liver injury. In summary, this article reviews the relevant pharmacogenes that have been associated to date with dosing and outcome among patients who received PAH medications.

Enzymatic activity of 38 CYP2C9 genotypes on ibuprofen

BACKGROUND AND OBJECTIVE

Ibuprofen, a common non-steroidal anti-inflammatory drug, is used clinically for pain relief and antipyretic treatment worldwide. However, regular or long-term use of ibuprofen may lead to a series of adverse reactions, including gastrointestinal bleeding, hypertension and kidney injury. Previous studies have shown that CYP2C9 gene polymorphism plays an important role in the elimination of various drugs, which leads to the variation in drug efficacy. This study aimed to evaluate the effect of 38 CYP2C9 genotypes on ibuprofen metabolism.

METHODS

Thirty-eight recombinant human CYP2C9 microsomal enzymes were obtained using a frugiperda 21 insect expression system according to a previously described method. Assessment of the catalytic function of these variants was completed via a mature incubation system: 5 pmol CYP2C9*1 and 38 CYP2C9 variants recombinant human microsomes, 5 μL cytochrome B5, ibuprofen (5-1000 μM), and Tris-HCl buffer (pH 7.4). The ibuprofen metabolite contents were determined using HPLC analysis. HPLC analysis included a UV detector, Plus-C18 column, and mobile phase [50% acetonitrile and 50% water (containing 0.05% trifluoroacetic acid)]. The kinetic parameters of the CYP2C9 genotypes were obtained by Michaelis-Menten curve fitting.

RESULTS

The intrinsic clearance (CL_int) of eight variants was not significantly different from CYP2C9*1; four CYP2C9 variants (CYP2C9*38, *44, *53 and *59) showed significantly higher CL_int (increase by 35%-230%) than that of the wild-type; the remaining twenty-six variants exhibited significantly reduced CL_int (reduced by 30%-99%) compared to that of the wild-type.

CONCLUSION

This is the first systematic evaluation of the catalytic characteristics of 38 CYP2C9 genotypes involved ibuprofen metabolism. Our results provide a corresponding supplement to studies on CYP2C9 gene polymorphisms and kinetic characteristics of different variants. We need to focus on poor metabolizers (PMs) with severely abnormal metabolic functions, because they are more susceptible to drug exposure.

Identification of adverse drug reactions that may be related to pharmacogenetics in a public hospital in the South of Brazil

BACKGROUND

Adverse drug reactions (ADRs) are of great concern in clinical practice. Pharmacogenetics can identify individuals and groups at increased risk of developing ADRs, enabling treatment adjustments to improve outcomes. The study aimed to determine the prevalence of ADRs related to drugs with pharmacogenetic evidence level 1A in a public hospital in Southern Brazil.

RESEARCH DESIGN AND METHODS

ADR information was collected from the pharmaceutical registries from 2017 to 2019. Drugs that have pharmacogenetic evidence level 1A were selected. Public genomic databases were used to estimate the genotypes/phenotypes frequency.

RESULTS

During the period, 585 ADRs were spontaneously notified. Most were moderate (76.3%), whereas severe reactions accounted for 33.8%. Additionally, 109 ADRs caused by 41 drugs presented pharmacogenetic evidence level 1A, representing 18.6% of all notified reactions. Depending on the drug-gene pair, up to 35% of individuals from Southern Brazil could be at risk of developing ADRs.

CONCLUSIONS

Relevant amount of ADRs were related to drugs with pharmacogenetic recommendations on drug labels and/or guidelines. Genetic information could guide and improve clinical outcomes, decreasing ADR incidence and reducing treatment costs.

The pharmacogenomic landscape of an Indigenous Australian population

Background: Population genomic studies of individuals of Indigenous ancestry have been extremely limited comprising <0.5% of participants in international genetic databases and genome-wide association studies, contributing to a "genomic gap" that limits their access to personalised medicine. While Indigenous Australians face a high burden of chronic disease and associated medication exposure, corresponding genomic and drug safety datasets are sorely lacking. Methods: To address this, we conducted a pharmacogenomic study of almost 500 individuals from a founder Indigenous Tiwi population. Whole genome sequencing was performed using short-read Illumina Novaseq6000 technology. We characterised the pharmacogenomics (PGx) landscape of this population by analysing sequencing results and associated pharmacological treatment data. Results: We observed that every individual in the cohort carry at least one actionable genotype and 77% of them carry at least three clinically actionable genotypes across 19 pharmacogenes. Overall, 41% of the Tiwi cohort were predicted to exhibit impaired CYP2D6 metabolism, with this frequency being much higher than that for other global populations. Over half of the population predicted an impaired CYP2C9, CYP2C19, and CYP2B6 metabolism with implications for the processing of commonly used analgesics, statins, anticoagulants, antiretrovirals, antidepressants, and antipsychotics. Moreover, we identified 31 potentially actionable novel variants within Very Important Pharmacogenes (VIPs), five of which were common among the Tiwi. We further detected important clinical implications for the drugs involved with cancer pharmacogenomics such as thiopurines and tamoxifen, immunosuppressants like tacrolimus and certain antivirals used in the hepatitis C treatment due to potential differences in their metabolic processing. Conclusion: The pharmacogenomic profiles generated in our study demonstrate the utility of pre-emptive PGx testing and have the potential to help guide the development and application of precision therapeutic strategies tailored to Tiwi Indigenous patients. Our research provides valuable insights on pre-emptive PGx testing and the feasibility of its use in ancestrally diverse populations, emphasizing the need for increased diversity and inclusivity in PGx investigations.

Validation of a genotyping technique for a surrogate marker of HLA-B∗58:01 for allopurinol-induced Stevens-Johnson syndrome and toxic epidermal necrolysis in the Japanese population

Stevens-Johnson syndrome and toxic epidermal necrolysis (SJS/TEN) are rare but severe cutaneous adverse drug reactions. Certain human leukocyte antigen (HLA) types have been associated with SJS/TEN onset, e.g., HLA-B^∗58:01 with allopurinol-induced SJS/TEN, but HLA typing is time-consuming and expensive; thus, it is not commonly used in clinical situations. In the previous work, we demonstrated that the single-nucleotide polymorphisms (SNP) rs9263726 was in absolute linkage disequilibrium with HLA-B^∗58:01 in the Japanese population, and can be used as a surrogate marker for the HLA. Here, we developed a new genotyping method for the surrogate SNP using the single-stranded tag hybridization chromatographic printed-array strip (STH-PAS) technique and performed an analytical validation. The results of genotyping rs9263726 using STH-PAS correlated well with those obtained using the TaqMan SNP Genotyping Assay for 15 HLA-B^∗58:01-positive and 13 HLA-B^∗58:01-negative patients (analytical sensitivity and specificity were both 100%). Additionally, at least 1.11 ng of genomic DNA was sufficient to digitally and manually detect positive signals on the strip. Robustness studies showed that the annealing temperature (66 °C) was the most important condition related to reliable results. Collectively, we developed an STH-PAS method that can rapidly and easily detect rs9263726 for predicting SJS/TEN onset.

Global distribution of functionally important CYP2C9 alleles and their inferred metabolic consequences

BACKGROUND

Genetic variability in the cytochrome P450 CYP2C9 constitutes an important predictor for efficacy and safety of various commonly prescribed drugs, including coumarin anticoagulants, phenytoin and multiple non-steroidal anti-inflammatory drugs (NSAIDs). A global map of CYP2C9 variability and its inferred functional consequences has been lacking.

RESULTS

Frequencies of eight functionally relevant CYP2C9 alleles (*2, *3, *5, *6, *8, *11, *13 and *14) were analyzed. In total, 108 original articles were identified that included genotype data from a total of 81,662 unrelated individuals across 70 countries and 40 unique ethnic groups. The results revealed that CYP2C9*2 was most abundant in Europe and the Middle East, whereas CYP2C9*3 was the main reason for reduced CYP2C9 activity across South Asia. Our data show extensive variation within superpopulations with up to tenfold differences between geographically adjacent populations in Malaysia, Thailand and Vietnam. Translation of genetic CYP2C9 variability into functional consequences indicates that up to 40% of patients in Southern Europe and the Middle East might benefit from warfarin and phenytoin dose reductions, while 3% of patients in Southern Europe and Israel are recommended to reduce starting doses of NSAIDs.

CONCLUSIONS

This study provides a comprehensive map of the genetic and functional variability of CYP2C9 with high ethnogeographic resolution. The presented data can serve as a useful resource for CYP2C9 allele and phenotype frequencies and might guide the optimization of genotyping strategies, particularly for indigenous and founder populations with distinct genetic profiles.

PAnno: A pharmacogenomics annotation tool for clinical genomic testing

Introduction: Next-generation sequencing (NGS) technologies have been widely used in clinical genomic testing for drug response phenotypes. However, the inherent limitations of short reads make accurate inference of diplotypes still challenging, which may reduce the effectiveness of genotype-guided drug therapy. Methods: An automated Pharmacogenomics Annotation tool (PAnno) was implemented, which reports prescribing recommendations and phenotypes by parsing the germline variant call format (VCF) file from NGS and the population to which the individual belongs. Results: A ranking model dedicated to inferring diplotypes, developed based on the allele (haplotype) definition and population allele frequency, was introduced in PAnno. The predictive performance was validated in comparison with four similar tools using the consensus diplotype data of the Genetic Testing Reference Materials Coordination Program (GeT-RM) as ground truth. An annotation method was proposed to summarize prescribing recommendations and classify drugs into avoid use, use with caution, and routine use, following the recommendations of the Clinical Pharmacogenetics Implementation Consortium (CPIC), etc. It further predicts phenotypes of specific drugs in terms of toxicity, dosage, efficacy, and metabolism by integrating the high-confidence clinical annotations in the Pharmacogenomics Knowledgebase (PharmGKB). PAnno is available at https://github.com/PreMedKB/PAnno. Discussion: PAnno provides an end-to-end clinical pharmacogenomics decision support solution by resolving, annotating, and reporting germline variants.

Pharmacogenomics in Asians: Differences and similarities with other human populations

INTRODUCTION

Various pharmacogenomic (PGx) variants differ widely in different ethnicities. and clinical outcomes associated with these variants may also be substantially varied. Literature was searched in different databases, i.e. PubMed, ScienceDirect, Web of Science, and PharmGKB, from inception to 30 June 2022 for this review.

AREAS COVERED

Certain PGx variants were distinctly varied in Asian populations compared to the other human populations, e.g. CYP2C19*2,*3,*17; CYP2C9*2,*3; CYP2D6*4,*5,*10,*41; UGT1A1*6,*28; HLA-B*15:02, HLA-B*15:21, HLA-B*58:01, and HLA-A*31:01. However, certain other variants do not vary greatly between Asian and other ethnicities, e.g. CYP3A5*3; ABCB1, and SLCO1B1*5. As evident in this review, the risk of major adverse cardiovascular events (MACE) was much stronger in Asian patients taking clopidogrel and who inherited the CYP2C19 loss-of-function alleles, e.g. CYP2C19*2 and*3, when compared to the western/Caucasian patients. Additionally, the risk of carbamazepine-induced severe cutaneous adverse drug reactions (SCARs) for the patients inheriting HLA-B*15:02 and HLA-B*15:21 alleles varied significantly between Asian and other ethnicities. In contrast, both Caucasian and Asian patients inheriting the SLCO1B1*5 variant possessed a similar magnitude of muscle toxicity, i.e. myopathy.

EXPERT OPINION

Asian countries should take measures toward expanding PGx research, as well as initiatives for the purposes of obtaining clinical benefits from this newly evolving and economically viable treatment model.

The Implementation of Pharmacogenetics in the United Kingdom

There is considerable inter-individual variability in the effectiveness and safety of pharmaceutical interventions. This phenomenon can be attributed to a multitude of factors; however, it is widely acknowledged that common genetic variation affecting drug absorption or metabolism play a substantial contributory role. This is a concept known as pharmacogenetics. Understanding how common genetic variants influence responses to medications, and using this knowledge to inform prescribing practice, could yield significant advantages for both patients and healthcare systems. Some health services around the world have introduced pharmacogenetics into routine practice, whereas others are less advanced along the implementation pathway. This chapter introduces the field of pharmacogenetics, the existing body of evidence, and discusses barriers to implementation. The chapter will specifically focus on efforts to introduce pharmacogenetics in the NHS, highlighting key challenges related to scale, informatics, and education.

Identification and in vitro functional assessment of 10 CYP2C9 variants found in Chinese Han subjects

Cytochrome P450 2C9 (CYP2C9) participates in about 15% of clinical drug metabolism, and its polymorphism is associated with individual drug metabolism differences, which may lead to the adverse drug reactions (ADRs). In this study, 1163 Chinese Han individuals were recruited to investigate their distribution pattern of CYP2C9 gene and find out the variants that may affect their drug metabolic activities. We successfully developed a multiplex PCR amplicon sequencing method and used it for the genetic screening of CYP2C9 in a large scale. Besides the wild type CYP2C9*1, totally 26 allelic variants of CYP2C9 were detected, which included 16 previously reported alleles and 10 new non-synonymous variants that had not been listed on the PharmVar website. The characteristics of these newly detected CYP2C9 variants were then evaluated after co-expressing them with CYPOR in S. cerevisiae microsomes. Immunoblot analysis revealed that except for Pro163Ser, Glu326Lys, Gly431Arg and Ile488Phe, most of newly detected variants showed comparable protein expression levels to wild type in yeast cells. Two typical CYP2C9 probe drugs, losartan and glimepiride, were then used for the evaluation of metabolic activities of variants. As a result, 3 variants Thr301Met, Glu326Lys, and Gly431Arg almost lost their catalytic activities and most of other variants exhibited significantly elevated activities for drug metabolism. Our data not only enriches the knowledge of naturally occurring CYP2C9 variants in the Chinese Han population, but also provides the fundamental evidence for its potential clinical usage for personalized medicine in the clinic.

c4c: Paediatric pharmacovigilance: Methodological considerations in research and development of medicines for children - A c4c expert group white paper

Children frequently respond differently to therapies compared to adults. Differences also exist between paediatric age groups for pharmacokinetics and pharmacodynamics in both efficacy and safety. Paediatric pharmacovigilance requires an understanding of the unique aspects of children with regard to, for example, drug response, growth and development, clinical presentation of adverse drug reactions (ADRs), how they can be detected and population-specific factors (e.g., more frequent use of off-label/unlicensed drugs). In recognition of these challenges, a group of experts has been formed in the context of the conect4children (c4c) project to support paediatric drug development. This expert group collaborated to develop methodological considerations for paediatric drug safety and pharmacovigilance throughout the life-cycle of medicinal products which are described in this article. These considerations include practical points to consider for the development of the paediatric section of the risk management plan (RMP), safety in paediatric protocol development, safety data collection and analysis. Furthermore, they describe the specific details of post-marketing pharmacovigilance in children using, for example, spontaneous reports, electronic health care records, registries and record-linkage, as well as the use of paediatric pharmacoepidemiology studies for risk characterisation. Next the details of the assessment of benefit-risk and challenges related to medicinal product formulation in the context of a Paediatric Investigation Plan (PIP) are presented. Finally, practical issues in paediatric signal detection and evaluation are included. This paper provides practical points to consider for paediatric pharmacovigilance throughout the life-cycle of medicinal products for RMPs, protocol development, safety data collection and analysis and PIPs.

Genotyping for HLA risk alleles versus patch tests to diagnose anti-seizure medication induced cutaneous adverse drug reactions

Aim: To provide a comparison of genotyping for HLA risk alleles versus patch testing to determine which of these two tests is a better diagnostic tool for cutaneous hypersensitivity reactions caused by anti-seizure medication. Methods: A literature study was performed in PubMed to assess the sensitivity and specificity of HLA genotyping and patch tests for identifying anti-seizure medication induced cutaneous hypersensitivity reactions. Results: This study shows that HLA-B*15:02 genotyping shows high sensitivity for carbamazepine-induced SJS/TEN, especially in Han Chinese and Southeast Asian patients (66.7-100.0%) whereas the sensitivity of patch tests (0.0-62,5%), HLA-A*31:01 (0-50%) and HLA-B*15:11 (18.2-42.9%) are lower. On the contrary, for carbamazepine and phenytoin induced DRESS, patch tests (respectively 70.0-88.9% and 14.3-70.0%) show higher sensitivity than HLA tests (0-66.7% and 0-12.7%). Also for lamotrigine-induced DRESS patch tests perform better than HLA-B*15:02 (33.3-40.0 versus 0%). For anti-seizure medication induced MPE and for oxcarbazepine-induced SCARs more studies are needed. Conclusion: Use of HLA-B genotyping may aid clinicians in the diagnosis of carbamazepine, phenytoin, lamotrigine and oxcarbazepine induced SJS/TEN, particularly in Han Chinese and Southeast Asian patients. On the other hand, patch tests seem to perform better in the diagnosis of carbamazepine and phenytoin induced DRESS.

rs144012689 is a highly specific representative marker of HLA-B*15:02 in the Chinese population

Objective: To develop an accurate and rapid real-time PCR technique for HLA-B*15:02 genotyping and investigate HLA-B*15:02 allele frequency in four ethnic populations in China. Materials & methods: Based on the highly specific representative markers, a real-time PCR assay was developed for HLA-B*15:02 genotyping, and HLA-B*15:02 allele frequencies were screened in four ethnic populations of China. Sequence-based typing was used to validate the accuracy of the assay. Results: The sensitivity and specificity of the assay were 100%, and the detection limit was 0.2 ng. The frequency of HLA-B*15:02 alleles distributed in the Bouyei population was significantly higher than in the Han group (p < 0.01). Neither the Tibetan nor the Uyghur population carried the HLA-B*15:02 haplotype. Conclusion: The authors developed an accurate HLA-B*15:02 genotyping method for evaluating the risk of adverse drug reactions induced by carbamazepine in various ethnic populations in China.

Advancing Pharmacogenomics from Single-Gene to Preemptive Testing

Pharmacogenomic testing can be an effective tool to enhance medication safety and efficacy. Pharmacogenomically actionable medications are widely used, and approximately 90-95% of individuals have an actionable genotype for at least one pharmacogene. For pharmacogenomic testing to have the greatest impact on medication safety and clinical care, genetic information should be made available at the time of prescribing (preemptive testing). However, the use of preemptive pharmacogenomic testing is associated with some logistical concerns, such as consistent reimbursement, processes for reporting preemptive results over an individual's lifetime, and result portability. Lessons can be learned from institutions that have implemented preemptive pharmacogenomic testing. In this review, we discuss the rationale and best practices for implementing pharmacogenomics preemptively.