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The impact of pharmacogenetic-informed care on medication adherence and psychological factors associated with adherence: A narrative review.

Improvement in medication adherence is often proposed as a potential advantage of pharmacogenetic-guided prescribing over a traditional one-size-fits-all approach. This paper provides a review of the published literature and presents the findings of studies that measure adherence to medication as an outcome of pharmacogenetic-informed care, or that measure the impact of pharmacogenetic-informed care on psychological factors that are associated with medication adherence. Adherence-related psychological factors are mapped to the Theoretical Domains Framework (TDF) to provide insight into how participants interact with pharmacogenetic-informed care as an intervention and to consider this in the context of medication adherence. A total of 23 studies were included, with 10 quantitative studies measuring medication adherence outcomes associated with pharmacogenetic-informed care. Five of these studies found a statistically significant improvement in adherence in the pharmacogenetic-tested group, two reported a small but non-significant trend, and three showed no difference. Additionally, 13 studies examined the impact of pharmacogenetic-informed care on psychological factors related to adherence. These factors were mapped to 10 TDF domains: knowledge (8 studies); social/professional role and identity (1); beliefs about capabilities (2); optimism (4); beliefs about consequences (10); intentions (5); goals (1); memory, attention and decision processes (7); social influences (4); and emotion (8). The findings suggest that although the evidence for pharmacogenetic-informed care improving medication adherence is mixed and limited, pharmacogenetic-informed care appears to positively influence psychological factors that may support adherence. These include improving knowledge, supporting decision-making and generally being perceived as a positive experience by patients.

adherence

Characterization of DPYD pharmacogenetic variation in Mexican patients with gastrointestinal malignancies.

PURPOSE: Fluoropyrimidines are among the most widely used chemotherapeutic agents for gastrointestinal malignancies, but interindividual variability in dihydropyrimidine dehydrogenase (DPD) activity, encoded by DPYD, can lead to severe or lethal toxicities. Most pharmacogenetic data on DPYD originates from European populations, limiting the applicability of current guidelines in admixed groups. METHODS: We evaluated DPYD pharmacogenetic variation and its association with fluoropyrimidine-related adverse events in Mexican patients with gastrointestinal cancers. Adverse events were prospectively assessed using CTCAE v5.0. Genotyping was performed with the Illumina Global Screening Array and analyzed using PLINK and R. RESULTS: A total of 208 patients were enrolled, and 192 samples passed genotyping quality control; 156 patients received fluoropyrimidines. Only three patients (1.5%) carried actionable DPYD variants (rs3918290, rs67376798 and rs75017182), yielding allele frequencies of 0.26%, approximately ten-fold lower than those reported in European cohorts. Genome-wide analyses did not reveal significant genotype-phenotype associations, though suggestive variants in SDK1, ZPBP, and FGF12 were observed. Pharmacodynamic analyses identified frequent variation in TYMS rs2847153 and MTHFR rs1801133, both previously associated with fluoropyrimidine toxicity. Overall, patients exhibited a predominantly Native Mexican ancestry (56.5%), which may explain the markedly low frequency of actionable DPYD alleles commonly found in European populations. CONCLUSIONS: These findings highlight the limited representation of admixed populations in pharmacogenetic research and underscore the need for population-specific data to inform safe and equitable fluoropyrimidine dosing.

Humans

Guidelines From the French-Speaking Society for Histocompatibility and Immunogenetics (SFHI) for Harmonisation of HLA Genotyping in Autoimmune Diseases, Drug Hypersensitivity and Pharmacogenetics.

HLA molecules play a central role in the adaptive immune response. Their high polymorphism influences individual susceptibility to various autoimmune diseases and certain drug-induced hypersensitivities. In France, HLA genotyping is classified as a medical genetics procedure and is strictly regulated. The Société Francophone d'Histocompatibilité et d'Immunogénétique (SFHI) has established national guidelines outlining clinically validated indications, required resolution levels and interpretation criteria based on robust data. These guidelines are particularly relevant for common clinical contexts, including autoimmune diseases and pharmacogenetic testing. Well-established associations include HLA-DQB1*02/DQA1*05 (DQ2) and HLA-DQB1*03:02/DQA1*05 (DQ8) with celiac disease, HLA-B*27 with spondyloarthritis, HLA-DQB1*06:02 with type 1 narcolepsy, HLA-A*29 with Birdshot chorioretinopathy and several pharmacogenetic risk alleles such as HLA-B*57:01 (abacavir), HLA-B*15:02 and HLA-A*31:01 (carbamazepine) and HLA-B*58:01 (allopurinol). In immunotherapy, the efficacy of tebentafusp has been shown to depend on HLA-A*02:01 positivity. HLA alleles must be interpreted as relative risk factors, not absolute predictors. Critical analysis of HLA-related scientific literature requires consideration of the genotyping technique, typing resolution, allele frequencies within the studied population and environmental factors. High-resolution typing is essential in pharmacogenetics and recommended in selected autoimmune disorders. Interpretation should be conducted by qualified medical biologists, integrating clinical context, allelic diversity and recent technological advances, particularly next-generation sequencing. HLA genotyping represents a valuable tool in diagnosis and risk assessment, with increasing importance in the era of personalised medicine.

Humans

Clinical Function Assignment of NAT2 Alleles by the Clinical Pharmacogenetics Implementation Consortium Pharmacogene Curation Expert Panel.

NAT2 encodes arylamine N-acetyltransferase 2, a key enzyme in the phase II metabolism of arylamines and arylhydrazines. NAT2 is highly polymorphic, resulting in variable distributions of rapid and poor metabolizers across global populations. Here, we detail the process undertaken by the Clinical Pharmacogenetics Implementation Consortium (CPIC) NAT2 Pharmacogene Curation Expert Panel (PCEP) to assign clinical function to NAT2 star (*) alleles using CPIC's standard terminology. Given the observed impact of NAT2 genetic variability on drug response, CPIC convened the NAT2-PCEP to standardize clinical allele function assignments. The NAT2-PCEP is comprised of multidisciplinary and international members, including researchers, clinicians, and implementers with expertise in pharmacogenomics and NAT2 molecular biology. Extensive in vitro and clinical literature was curated from PubMed and other sources to assess NAT2 genotype-to-phenotype concordance as well as the biochemical function of NAT2 star alleles. The NAT2-PCEP assigned allele clinical function using CPIC's standard terminology (increased, decreased, uncertain, and unknown function) to 59 star alleles cataloged by the Pharmacogene Variation Consortium (PharmVar). Two alleles, NAT2*1 and NAT2*4, were assigned increased function (historically known as rapid), 40 alleles were assigned decreased function (historically known as slow), 10 alleles were assigned uncertain function, and seven alleles were assigned unknown function. Rigorous evidence review and in-depth PCEP discussion were crucial in determining these function assignments. The findings reported here underscore the importance of standardized allele functional terms and diplotype-to-phenotype assignments to further the clinical implementation of NAT2 pharmacogenetic test results.

Arylamine N-Acetyltransferase

Beyond enrichment: pharmacogenetic heterogeneity in treatment-resistant depression.

OBJECTIVES: Genetic variation has been proposed as a potential contributor to antidepressant nonresponse, but its role in treatment-resistant depression (TRD) remains unclear. This study used pharmacogenetics (PGx) to characterize genetic variation in TRD and determine whether actionable PGx variation and drug-gene interaction (DGI) mismatch were associated with antidepressant nonresponse and TRD burden. METHODS: This observational study included 158 individuals with TRD recruited from outpatient clinics in Western Australia. Genotype and genotype-predicted phenotypes for CYP2B6, CYP2C19, and CYP2D6 were derived from commercial PGx testing and compared with ethnicity-matched reference populations from ClinPGx. Antidepressant-specific DGIs were classified as actionable or nonactionable according to Clinical Pharmacogenetics Implementation Consortium guidelines, and unsupervised clustering was used to identify clusters based on these actionability profiles. Analyses were performed to determine if actionable PGx variation, cluster membership, or PGx mismatch was associated with TRD burden (number of failed antidepressant trials). RESULTS: PGx variation in the TRD cohort was consistent with population expectations, with no evidence of enrichment for actionable PGx variants. Clustering identified six clusters with distinct and gene-specific patterns of PGx variation independent of demographic and clinical characteristics. However, neither PGx mismatch nor cluster membership were associated with TRD burden. CONCLUSION: These findings suggest that actionable PGx phenotypes are neither enriched in TRD nor associated with greater TRD severity. Rather, the results indicate that TRD does not represent a single, unified PGx-predicted 'poor pharmacological responder' phenotype but instead reflects a biologically heterogeneous collection of distinct PGx profiles.

antidepressants

Genetic and epigenetic determinants of cytochrome P450 activity in psychopharmacology: from pharmacogenetics to functional pharmacogenomics.

Classical pharmacogenetics has explained interindividual variability in psychotropic drug response primarily through inherited polymorphisms in cytochrome P450 enzymes. This framework successfully identified extreme metabolizer phenotypes and informed genotype-guided dosing recommendations. However, genotype-based predictions frequently correlate more strongly with pharmacokinetic parameters than with clinical outcomes. Patients sharing similar CYP genotypes often exhibit divergent therapeutic trajectories, while metabolic phenotypes may change during treatment without corresponding alterations in DNA sequence. These observations suggest the existence of a genotype-phenotype gap mediated by regulatory processes not captured by genotyping alone. Evidence from epigenetic regulation, environmental modulation of pharmacogene expression, and phenoconversion indicates that metabolic capacity is better understood as a dynamic functional state rather than a fixed inherited trait. This review examines the role of these mechanisms in psychiatric pharmacotherapy and explores the implications of shifting the predictive focus of precision medicine from static genotype to functional state.

Humans

[Pharmacokinetics of two beta blocking drugs: detection of a pharmacogenetic abnormality].

10 healthy male volunteers received orally either 100 mg tolamolol or 20 mg bufuralol. These experiments were repeated by intravenous administration of 10 and 5 mg respectively of these two drugs. Plasma levels of the parent drugs and their main metabolite were measured. In one subject, the apparent half-life of elimination was increased from 2.5 h (normal subjects) to 5 h for both drugs. This prolongation of the half-life is associated with low plasma levels of the metabolites, a peculiarity which can be explanined by a decreased rate of metabolism for these two drugs. This anomaly may explain the marked orthostatic hypotension observed only in this subject. The likelihood of a pharmacogenetic defect is discussed.

Administration, Oral

Tolbutamide pharmacogenetics and the UGDP controversy.

We analyzed the relationship between the pharmacogenetics of tolbutamide metabolism and the controversial University Group Diabetes Program (UGDP) study. Before the institution of that study, the extent of genetic control over the variation in the rate of tolbutamide metabolism was unknown, and all subjects included in the tolbutamide treatment group were given 1,500 mg/day of tolbutamide in a fixed dosage. We addressed the hypothesis that high accrued blood levels of tolbutamide in genetically predisposed slow inactivators might have contributed to the toxic effects reported by the UGDP study. This proposal is based on recent findings from population, twin, and family studies that tolbutamide metabolism is under monogenic control, with nearly one fourth of the population classified as slow inactivators.

Alleles

Patient views on receiving a pharmacogenetic passport - a mixed methods study exploring experiences and use after an opportunistic offer.

Genomic data plays an increasingly important role in clinical care, yet how it can be appropriately integrated into standard practice remains debated. One emerging approach is the opportunistic use of whole-exome sequencing (WES) data to offer pharmacogenetic (PGx) information. While initiatives providing PGx prescribing recommendations ahead of actual prescriptions are growing, little is known about how recipients of such information use it in practice or how it shapes their perceived roles and responsibilities. Using a mixed-methods design combining a quantitative survey with qualitative interviews, we explored the experiences and use of an opportunistic PGx passport, that was offered to parents who had undergone a trio-WES in pursuit of a genetic diagnosis for their child's developmental delay. We examined how they experienced and used the passport in practice and how it influenced their perceived role and responsibilities in a care setting. A total of 44 respondents were included in this study. The passport was used by only a minority of participants, partly due to the absence of a current medication need, but primarily due to limited ability to understand and apply the PGx information. The PGx passport shifted responsibilities away from the digital healthcare information systems onto the individual recipient. Without adequate support, this shift risks responsibilizing recipients rather than genuinely empowering them with access to their PGx profiles. Based on these findings, we offer recommendations for the implementation of similar opportunistic PGx offers and for policy focussing on the appropriate integration of PGx into standard healthcare practice.

Journal Article

Pharmacogenetics of alcohol metabolism and alcoholism.

The pharmacogenetic differences among individuals in their capacity to metabolize ingested alcohol are possibly responsible for the large inter-individual and inter-ethnic variations observed in the outcome of alcohol use and misuse. Based on results of adoption, twin, and family studies it is now widely accepted that the vulnerability to alcoholism is determined by genetic factors as well as by environment. There is a constant search for biological markers and specific genes which could identify individuals genetically predisposed to alcohol abuse and alcoholism. Numerous 'candidate genes' for alcoholism have been suggested including the alcohol metabolizing enzymes, alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH). Both ADH and ALDH exhibit genetic heterogeneity. An atypical form of ADH (ADH2), which contains a variant beta 2 subunit instead of the usual beta 1 subunit, differs substantially from the usual form in its kinetic properties and is found more frequently among the Japanese, Chinese and other Mongoloid populations than in Caucasoids and Negroids. A widely prevalent genetic polymorphism has been observed for ALDH; about 50% of Japanese and Chinese livers possess an inactive ALDH (ALDH2 isozyme) whereas none of the Caucasian or Negroid populations show this isozyme abnormality. These metabolic polymorphisms seem to contribute to differences in the in vivo elimination rate of ethanol and acetaldehyde, and may explain differences in alcohol-related behaviour and its disease outcome. Taken together, Orientals who possess an atypical ALDH2 gene are more sensitive to acute responses to alcohol, tend to be discouraged from drinking alcohol, and consequently are at lower risk of developing alcohol-related disorders. However, more work is needed to support these findings. Recent advances in molecular genetics have made it possible to analyze directly the human genome. This may help in a better understanding of the complex genetic and environmental factors in alcohol abuse by providing prospects for identification of gene loci which may be responsible for predisposition to, and protection from, alcoholism.

Alcohol Dehydrogenase

Alcoholism: a pharmacogenetic disorder.

Alcoholism is an extremely common psychosocial behavioral disorder for which genetic factors may play an important role. Statistical analysis of special kinds of family studies that separate inherited factors from the common family environment point strongly to genetic predisposition. This paper presents data and speculations on the genetically determined differences among population subgroups and individuals in the acute effects of ethanol ingestion, the metabolism of ethanol, the process of tolerance, physical dependence and addictability, premorbid personality features and serious complications of alcoholism in the liver and brain of the alcoholic and in the offspring of alcoholic mothers.

Abnormalities, Drug-Induced