The application of fluoropyrimidine-based chemotherapy in colorectal cancer treatment is known to pose significant toxicity risks, which can be mitigated by tailoring treatment according to DPYD gene variants. This study evaluates the impact of DPYD genotype-guided dosing on treatment-related toxicities and patient outcomes.

A retrospective analysis was conducted on CRC patients treated with fluoropyrimidines in adjuvant setting at The Wellbeing Services County of Ostrobothnia. Patients were divided into two cohorts based on the implementation of routine DPYD genotyping: pregenotyping (2016-2018) (n = 80) and postgenotyping (2020-2022) (n = 69). The incidence of side effects, treatment discontinuation, hospitalization, and 90-day mortality were compared between groups.

The study revealed a reduction in 90-day mortality rates among patients who underwent DPYD genotyping before treatment. Patients with pathogenic DPYD variants received ≥50% reduced doses initially, leading to no severe toxicities (grade ≥3). Class 3 variants showed similar side effect profiles and hospitalization rates as untested patients but had a lower rate of treatment discontinuation.

Upfront DPYD genotyping appears to improve patient safety in CRC patients treated with adjuvant fluoropyrimidines, leading to personalized dosing that reduces severe toxicities and early mortality. These findings underscore the importance of integrating pharmacogenetic testing in clinical oncology to optimize treatment regimens and enhance patient care.

Pharmacogenomic (PGx) variants can significantly impact drug response, but limited data exists on their prevalence in Middle Eastern populations. This study aimed to investigate the inheritance of certain markers in candidate pharmacogenes among healthy Saudis.

DNA samples from 95 unrelated healthy Saudi participants were genotyped using the Affymetrix Axiom Precision Medicine Diversity Array. Thirty-eight variants in 15 pharmacogenes were analyzed based on their clinical relevance and lack of previous reporting in Saudi populations.

Twenty-six of the 37 tested markers were undetected in the cohort. The selected variants in six genes [DPYD (rs1801268), CACNA1S (rs772226819), EGFR (rs121434568), RYR1 (rs193922816), CYP2B6 (rs3826711), and MT-RNR1 (rs267606617, rs267606618, rs267606619)] were found to be non-existing among Saudis. In contrast, 11 variants and alleles in nine pharmacogenes were detected at varying frequencies. Notable findings included high frequencies of variants in ATIC [rs4673993, minor allele frequency (MAF) = 0.71)] and SLC19A1 (rs1051266, MAF = 0.48) affecting methotrexate efficacy. Three alleles were identified in CYP3A4, including a common (CYP3A4 rs2242480) and two rare alleles (*3 and *22). Another three markers [rs16969968 in CHRNA5, rs11881222 in IFNL3 (IL28B), and SLCO1B1*14] were found to be highly distributed among the participants (MAF = 0.35, 0.30, and 0.14, respectively). Conversely, three rare markers: CYP2A6*2, NAT2*14, and rs115545701 in CFTR, were identified at low-frequency levels (MAF = 0.021, 0.011, 0.005, respectively). Statistically significant differences in allele frequencies were observed for eight variants between Saudi and African populations, five variants compared to East Asians, and two variants compared to Europeans.

This study provides novel insights into the distribution of clinically relevant PGx variants in the Saudi population. The findings have implications for personalizing treatments for various conditions, including rheumatoid arthritis, cystic fibrosis, and hepatitis C. These data contribute to the development of population-specific PGx testing panels and treatment guidelines.

The safety of systemic fluoropyrimidines (e.g., 5-fluorouracil, capecitabine) is impacted by germline genetic variants in DPYD, which encodes the dihydropyrimidine dehydrogenase (DPD) enzyme that functions as the rate-limiting step in the catabolism of this drug class. Genetic testing to identify those with DPD deficiency can help mitigate the risk of severe and life-threatening fluoropyrimidine-induced toxicities. Globally, the integration of DPYD genetic testing into patient care has varied greatly, ranging from being required as the standard of care in some countries to limited clinical use in others. Thus, implementation strategies have evolved differently across health systems and countries. The primary objective of this tutorial is to provide practical considerations and best practice recommendations for the implementation of DPYD-guided systemic fluoropyrimidine dosing. We adapted the Exploration, Preparation, Implementation, and Sustainment (EPIS) framework to cover topics including the clinical evidence supporting DPYD genotyping to guide fluoropyrimidine therapy, regulatory guidance for DPYD genotyping, key stakeholder engagement, logistics for DPYD genotyping, development of point-of-care clinical decision support tools, and considerations for the creation of sustainable and scalable DPYD genotype-integrated workflows. This guide also describes approaches to counseling patients about DPYD testing and result disclosure, along with examples of patient and provider educational resources. Together, DPYD testing and clinical practice integration aim to promote safe prescribing of fluoropyrimidine therapy and decrease the risk of severe and life-threatening fluoropyrimidine toxicities.

Implementing pharmacogenomic-guided management in cancer patients equitably and effectively in a large population presents challenges. DPYD genotyping determines clinically significant variants of patients at increased risk of developing grade3-5 fluoropyrimidine (FP) toxicity. FP chemotherapies are prescribed for ~16,000 Australians with a 10%-40% grade3-4 toxicity incidence and 1% mortality. Variant carriers can have FP dosing adjusted to improve treatment tolerance without compromising anticancer effect. This strategy has not been formally adopted within Australia, despite widespread international standardisation.

This pilot study determined genotyping turnaround-times (TAT) for 4 DPYD variants (c.1905+1G>A, c.1679T>G, c.2846A>T and c.1236G>A/Haplotype B3) in Australian patients. Secondary objectives were identification of FP toxicities of DPYD variant carriers, and analysis of healthcare stakeholder perspectives, including enablers/barriers to implementation.

Genotyping was determined by Real-Time Polymerase Chain Reaction. Qualitative data were determined through semi-structured questionnaire.

104 patients recruited over 24 months had a mean TAT of 7.2 days, 5.2 business days (range 1-30). Grade3-4 toxicity occurred in 9/16 DPYD variant carriers, including 2 ICU admissions and 1 death. Themes from 30 questionnaire respondents suggest that clinical environment and resources were fundamental barriers, and motivation to improve patient care was the predominant enabler of change.

DPYD genotyping is feasible for improving precision-oncology for patients requiring FP chemotherapies. A TAT of 7 days is acceptable by both stakeholder respondents and national oncology clinician groups. This pilot study, although small, informs a large national project evaluating prospective DPYD genotyping and its impact on FP tolerability, patient safety and cost-effectiveness in Australia.

Pharmacogenomics enables personalization of drug therapy improving effectiveness and/or safety. Dihydropyrimidine dehydrogenase [DPYD] testing prior to fluoropyrimidine chemotherapy was commissioned by NHS England in response to an update from the Medicines and Healthcare products Regulatory Agency.

A questionnaire developed and approved by the National DPYD Working Group investigated processes of testing, receiving and responding to results. The survey was distributed to Genomics Medicine Service Alliance (GMSA) Clinical Directors and Pharmacy Senior Responsible Officers for dissemination in their geography. Data were collected June-September 2021. All hospitals delivering fluoropyrimidines across the UK were invited to participate.

131/138 (94.9%) organizations reported testing all patients receiving fluoropyrimidines. In England 76.7% of hospitals sent samples to centrally commissioned genomics laboratories. In the devolved nations, 73.9% sent samples to regional genomics laboratories. Multidisciplinary staff including oncologists, independent non-medical prescribers, clinical nurse specialists, screening pharmacists and chemotherapy nurses requested the test, checked and actioned the result. Self-reported turnaround times varied from <2 days where a regional laboratory was colocated with a chemotherapy centre to >10 days.

Through multiprofessional, national collaboration, this is the first report studying the large-scale rollout of a nationally commissioned pharmacogenetic test. Whilst DPYD testing has been successfully implemented, there is a need to standardize and improve end-to-end turnaround times. This has led to the development of a best practice pathway. Critically, GMSAs must build on this implementation to deliver its priorities, in supporting equitable access to future pharmacogenomic testing across a wider cohort of therapies.

Despite the implementation of DPYD genotype-guided dosing, approximately 1 in 3 patients receiving fluoropyrimidine-containing chemotherapy continues to experience severe toxicity. While clinical studies have demonstrated a favorable tolerance among highly selected fit older adults, real-world studies have shown an increased risk of toxicity.

To identify predictors of severe toxicity or treatment deintensification in older DPYD wild-type adults receiving fluoropyrimidine-containing chemotherapy.

Patients wild type for four tested DPYD variants, aged ≥65 years, who participated in a prospective clinical trial investigating genotype-guided individualized fluoropyrimidine dosing, were eligible for the study. The association between tumor-, treatment-, and patient-related characteristics and the occurrence of severe toxicity (grade ≥3, CTCAE v5.0) was analyzed in univariate and multivariate logistic regression analyses. The same analyses were performed for a composite endpoint of severe toxicity or treatment deintensification (including dose reduction, cycle delay, or discontinuation).

A total of 311 patients were included. Median age was 71.2 years and 58.8% were male. Grade ≥3 toxicity occurred in 23.2% of patients. In multivariate analysis, none of the characteristics studied were significantly associated with the occurrence of grade ≥3 toxicity. The composite endpoint occurred in 41.2% of patients and was associated with the use of full dose monotherapy in multivariate analysis.

Despite DPYD genotype-based dosing, grade ≥3 toxicity and treatment deintensification frequently occur in older patients treated with fluoropyrimidine chemotherapy. No patient-related variables were found to be associated with grade ≥3 toxicity, but treatment with dose-reduced monotherapy resulted in fewer treatment deintensification or severe toxicity events.

While standard doses of adjuvant fluoropyrimidine-based chemotherapies are generally safe for most patients, the risk of severe adverse drug reactions (ADRs) is increased for those with dihydropyrimidine dehydrogenase deficiency (DPYD), a genetic variation that affects drug metabolism. The objective of this study was to examine the cost effectiveness of offering DPYD pharmacogenetic-guided care, where genetic testing informs personalized dosing versus the current standard of care (SoC), which involves administering fluoropyrimidine-based therapies without prior genetic screening, for local or metastatic breast cancer patients in Qatar.

We developed a two-stage decision analysis, with an analytic tree model over a 6-month period, followed by a life-table Markov model over a lifetime horizon. We compared the current SoC with the alternate strategy of DPYD genetic screening in patients living in Qatar with local or metastatic breast cancer who were eligible for adjuvant fluoropyrimidine therapy. Clinical outcomes and utilities were obtained from published studies, while healthcare costs were estimated from Hamad Medical Corporation, Qatar. The short-term outcome included the incremental cost-effectiveness ratio (ICER), defined as cost per success (survival without grade III/IV ADRs) at 6 months. The long-term outcome was the ICER, defined as cost per quality-adjusted life year (QALY) gained, with a 3% annual discount rate. The study adopted a public healthcare perspective in Qatar. Sensitivity analyses were conducted to explore the impact of key input parameters on the robustness of the model.

In the short-term model, at its base case, DPYD genomic screening was dominant over SoC with a mean cost-saving of QAR84,585 (95% confidence interval [CI], 45,270-151,657). This cost saving reflects the overall economic benefits associated with the implementation of DPYD genomic screening. In the long-term model, compared to the current SoC, DPYD genetic screening would result in an ICER of QAR21,107 (95% CI -59,382-145,664) per QALY gained.

Based on our model, implementing DPYD genetic screening to detect DPYD mutations in breast cancer patients before therapy initiation seems to be a cost-saving and cost-effective strategy in Qatar.

In 2015, the United States Food and Drug Administration (FDA) approved uridine triacetate to treat overdose and severe toxicity of the fluoropyrimidine chemotherapy agents 5-fluorouracil (5-FU) and its oral prodrug capecitabine. Uridine triacetate is as an oral prodrug of uridine that competes with cytotoxic fluoropyrimidine metabolites for incorporation into nucleotides. Two million people worldwide start fluoropyrimidine chemotherapy each year, with 20-30% developing severe or life-threatening adverse effects, often attributable to a genetic predisposition such as dihydropyrimidine dehydrogenase deficiency. Whilst genetic prescreening is recommended prior to starting fluoropyrimidine agents, this only prevents 20-30% of early-onset life-threatening toxicity and so does not obviate the need for an antidote. Initial in-human studies established that uridine triacetate more than doubles the maximum tolerated weekly 5-FU bolus dose. A lack of clinical equipoise meant a placebo-controlled phase III trial was not ethical and so the phase III trials used historical controls. These found that uridine triacetate improved survival in those with fluoropyrimidine overdose and severe toxicity from 16% to 94%, with 34% able to resume chemotherapy within 30 days. Five case reports of delayed fluoropyrimidine toxicity demonstrate improvement following uridine triacetate treatment 120-504 h after last fluoropyrimidine administration, suggesting efficacy beyond the FDA licencing indications. Mechanistically uridine triacetate would be expected to be effective for overdose and severe toxicity of tegafur (a 5-FU prodrug), but there are no published case reports describing this. Uridine triacetate is available internationally through an expanded access scheme and has been available in the UK since 2019 on a named patient basis.

Pharmacogenetic (PGx) screening is intended to optimize drug efficacy and reduce adverse drug reactions. Current screening options include genotyping assays for preselected PGx variants and broader next-generation sequencing panels (NGS). Few studies have directly compared preemptive PGx screening methods.

The two PGx methods were compared in a cross-sectional study of adult Military Health System (MHS) clinic beneficiaries. Participants had initial targeted CYP2C19/CYP2D6 genotyping at a Military Health System Laboratory. Genotyping was followed by multi-gene NGS testing. Current prescriptions were recorded and potential drug-drug interactions screened to evaluate prescribing risk.

All participants (100%) had at least one clinically actionable NGS panel result compared to 81% with targeted CYP2C19/CYP2D6 genotyping. Participants (n = 162) had an average of 6.6 (range 0-22) prescriptions and 2.7 (range 0-24) drug-drug interactions. Among those with at least one clinically actionable NGS result, 42% were currently taking medication with actionable CPIC guidelines (Level A/B), compared with 24% with CYP2C19/CYP2D6 genotyping. Sixteen participants (10%) had uncertain NGS panel results, with none for CYP2C19/CYP2D6 genotyping.

Preemptive multi-gene NGS detected more clinically actionable PGx results than targeted CYP2C19/CYP2D6 genotyping. Effective PGx screening in the MHS may decrease preventable adverse effects and improve military readiness.

In 20-30% of the patients, fluoropyrimidines (5-FU) based chemotherapy leads to severe toxicity, which is associated with dihydropyridine dehydrogenase (DPD) deficiency. Therefore, DPYD genotyping became standard practice before treatment with fluoropyrimidines. Nevertheless, only 17% of the patients with severe toxicity have a DPYD variant. Therefore, an urgent need persists to investigate other strategies contributing to prediction and prevention of toxicity. Endogenous DPD substrates are considered as potential biomarkers to predict toxicity, yet contradictional data exist on demonstrating uracil as a reliable biomarker. Thymine as biomarker for toxicity has been investigated less. The aim of this study was to determine the association between the concentrations of uracil, thymine dihydrouracil (DHU) and dihydrothymine (DHT), with the systemic drug exposure of 5-FU and DPD enzyme activity in patients treated with 5-FU.

We included 36 patients with gastrointestinal malignancy who received 5-FU infusion. DPYD genotyping was conducted before start of treatment. Blood samples for determining 5-FU, uracil and thymine concentrations during infusion and DPD enzyme activity were taken.

We found a significant correlation between the 5-FU systematic exposure and baseline thymine concentrations (R2 = 0.1468; p = 0.0402). DPD enzyme activity was significantly correlated with baseline thymine concentrations but no correlation was found between DPD enzyme activity and 5-FU systemic drug exposure.

5-FU dose individualization based on thymine concentrations could be a promising addition to DPYD genotyping to predict 5-FU-induced toxicity. Larger prospective trials are needed to examine thymine as predictor for toxicity in daily practice.

Trial NL7539 at 'Overview of Medical Research in the Netherlands' (ID NL-OMON21471). Date of registration 19-02-2019.

The CAPEOX (combination of oxaliplatin and capecitabine) chemotherapy protocol is widely used for colorectal cancer treatment, but it can lead to chemotherapy-induced adverse effects (CRAEs).

To uncover the mechanisms and potential biomarkers for CRAE susceptibility, we performed whole-genome sequencing on normal colorectal tissue (CRT) before adjuvant chemotherapy. This is followed by in vivo and in vitro verifications for selected gene and CRAE pair.

Our analysis revealed specific germline mutations linked to Grade 2 (or higher) chemotherapy-induced thrombocytopenia (CIT) and nausea/vomiting (CINV). Notably, both CRAEs were associated with mutations in the DLG5 gene. We found that DLG5 mutations related to CIT were associated with increased gene expression, while those associated with CINV were linked to suppressed gene expression, as indicated by the Genotype-Tissue Expression (GTEX) database. In megakaryocytes, overexpression of human DLG5 suppressed the hippo signalling pathway and induced YAP expression. In zebrafish, overexpression of human DLG5 not only reduced platelet production but also inhibited thrombus formation. Subsequent qPCR analysis revealed that DLG5 overexpression affected genes involved in cytoskeleton formation and alpha-granule formation, which could impact the normal generation of proplatelets.

We identified a series of germline mutations associated with susceptibility to CIT and CINV. Of particular interest, we demonstrated that induced and suppressed DLG5 expression is respectively related to CIT and CINV. These findings shed light on the involvement of the hippo signalling pathway and DLG5 in the development of CRAEs, providing valuable insights into potential targets for therapeutic interventions.

Adverse drug reactions (ADRs) account for a large proportion of hospitalizations among adults and are more common in multimorbid patients, worsening clinical outcomes and burdening healthcare resources. Over the past decade, pharmacogenomics has been developed as a practical tool for optimizing treatment outcomes by mitigating the risk of ADRs. Some single-gene reactive tests are already used in clinical practice, including the DPYD test for fluoropyrimidines, which demonstrates how integrating pharmacogenomic data into routine care can improve patient safety in a cost-effective manner. The evolution from reactive single-gene testing to comprehensive pre-emptive genotyping panels holds great potential for refining drug prescribing practices. Several implementation projects have been conducted to test the feasibility of applying different genetic panels in clinical practice. Recently, the results of a large prospective randomized trial in Europe (the PREPARE study by Ubiquitous Pharmacogenomics consortium) have provided the first evidence that prospective application of a pre-emptive pharmacogenomic test panel in clinical practice, in seven European healthcare systems, is feasible and yielded a 30% reduction in the risk of developing clinically relevant toxicities. Nevertheless, some important questions remain unanswered and will hopefully be addressed by future dedicated studies. These issues include the cost-effectiveness of applying a pre-emptive genotyping panel, the role of multiple co-medications, the transferability of currently tested pharmacogenetic guidelines among patients of non-European origin and the impact of rare pharmacogenetic variants that are not detected by currently used genotyping approaches.

Fluoropyrimidines are metabolized in the liver by the enzyme dihydropyrimidine dehydrogenase (DPD), encoded by the DPYD gene. About 7% of the European population is a carrier of DPYD gene polymorphisms associated with reduced DPD enzyme activity.

To assess the prevalence of DPYD polymorphisms and their impact on fluoropyrimidine tolerability in Italian patients with gastrointestinal malignancies.

A total of 300 consecutive patients with a diagnosis of gastrointestinal malignancy and treated with a fluoropyrimidine-based regimen were included in the analysis and divided into two cohorts: (1) 149 patients who started fluoropyrimidines after DPYD testing; and (2) 151 patients treated without DPYD testing. Among the patients in cohort A, 15% tested only the DPYD2A polymorphism, 19% tested four polymorphisms (DPYD2A, HapB3, c.2846A>T, and DPYD13), and 66% tested five polymorphisms including DPYD6.

Overall, 14.8% of patients were found to be carriers of a DPYD variant, the most common being DPYD6 (12.1%). Patients in cohort A reported ≥ G3 toxicities (P = 0.00098), particularly fewer nonhematological toxicities (P = 0.0028) compared with cohort B, whereas there was no statistically significant difference between the two cohorts in hematological toxicities (P = 0.6944). Significantly fewer chemotherapy dose reductions (P = 0.00002) were observed in cohort A compared to cohort B, whereas there was no statistically significant differences in chemotherapy delay.

Although this study had a limited sample size, it provides additional information on the prevalence of DPYD polymorphisms in the Italian population and highlights the role of pharmacogenetic testing to prevent severe toxicity.

Providers can use combinatorial pharmacogenomic panels to aid psychiatric medication prescribing. Results are typically documented in static documents which list the genotype and predicted phenotype (interpretation). However, genotype-to-phenotype translations can differ between laboratories and change as scientific consensuses evolves. Here, we describe the implications of reinterpreting phenotype after combinatorial psychiatric pharmacogenomic testing in a real-world setting.

143 patients underwent testing from 2014 to 2021. Reported genotypes and phenotypes were compared to 2024 Clinical Pharmacogenetics Implementation Consortium definitions. Chi-square tests and logistic regression were used to examine the differences in phenotype frequencies before and after reinterpretation and examine the association with time since testing.

Eighty-one patients (57%) required at least one updated interpretation. CYP2C19 interpretations changed for 44/143 patients (31%), followed by CYP2D6 (29%), CYP2B6 (3%), and CYP2C9 (1%). Reinterpretation reduced the number of CYP2D6 ultrarapid and poor metabolizers (p = 0.005), which has implications for antidepressant prescribing. Likelihood of a patient having a reinterpreted phenotype was not associated with time since reporting (p = 0.71).

Reported phenotypes from combinatorial PGx testing often do not align with current standardized definitions, even from tests performed recently. Health systems should establish procedures to standardize and periodically update pharmacogenomic interpretations.

Pharmacogenetics (PGx) aims to optimize drug treatment outcomes by using a patient's genetic profile for individualized drug and dose selection. Currently, reactive and pretherapeutic single-gene PGx tests are increasingly applied in clinical practice in several countries and institutions. With over 95% of the population carrying at least one actionable PGx variant, and with drugs impacted by these genetic variants being in common use, pretherapeutic or preemptive PGx panel testing appears to be an attractive option for better-informed drug prescribing. Here, we discuss the current state of PGx panel testing and explore the potential for clinical implementation. We conclude that available evidence supports the implementation of pretherapeutic PGx panel testing for drugs covered in the PGx guidelines, yet identification of specific patient populations that benefit most and cost-effectiveness data are necessary to support large-scale implementation.

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To date, the clinical benefit and utility of implementing a DPYD/UGT1A1 pharmacogenetic-informed therapy with fluoropyrimidines and/or irinotecan have not been prospectively investigated.

To examine clinically relevant toxic effects, hospitalizations, and related costs while preserving treatment intensity and efficacy outcomes in patients with gastrointestinal cancer.

This nonprespecified secondary analysis stems from Pre-Emptive Pharmacogenomic Testing for Preventing Adverse Drug Reactions (PREPARE), a multicenter, controlled, open, block-randomized, crossover implementation trial conducted from March 7, 2017, to June 30, 2020, and includes data from Italy according to a sequential study design. The study population included 563 patients (intervention, 252; control [standard of care], 311) with gastrointestinal cancer (age ≥18 years) who were eligible for fluoropyrimidine and/or irinotecan treatment. Data analysis for the present study was performed from May 27 to October 10, 2024.

Participants with actionable variants (DPYD*2A, DPYD*13, .DPYD c.2846A>T, and DPYD c.1236G>A for fluoropyrimidines, and UGT1A1*28, UGT1A1*6, and UGT1A1*27 for irinotecan) received drug or dose adjustments based on Dutch Pharmacogenetics Working Group recommendations.

The primary outcome was clinically relevant toxic effects (National Cancer Institute Common Terminology Criteria for Adverse Events grade ≥4 hematologic, grade ≥3 nonhematologic, or causing hospitalization, fluoropyrimidines and/or irinotecan causally related). Secondary outcomes included hospitalization rates, toxic effect management costs, intensity of treatment, quality-adjusted life-years, and 3-year overall survival.

Overall, 1232 patients were enrolled in Italy, with 563 included in this analysis (317 [56.3%] men; median age, 68.0 [IQR, 60.0-75.0] years). In the intervention arm, carriers of any actionable genotype exhibited a 90% lower risk of clinically relevant toxic effects compared with the control arm (odds ratio, 0.1; 95% CI, 0.0-0.8; P = .04). They also presented higher toxic effect management costs per patient ($4159; 95% CI, $1510-$6810) compared with patients in the intervention arm ($26; 95% CI, 0-$312) (P = .004) and a higher rate of hospitalization (34.8% vs 11.8%; P = .12). The differences were not significant among all patients. Three-year overall survival did not differ significantly between arms, while quality-adjusted life-years significantly improved in the intervention arm. The pharmacogenetics-informed approach did not manifest a detrimental effect on treatment intensity in actionable genotype carriers.

In this secondary analysis of PREPARE, pretreatment application of DPYD- and UGT1A1-guided treatment appeared to increase safety and reduce hospitalizations and related costs in patients with gastrointestinal cancer. Clinical benefit did not appear to be affected.

ClinicalTrials.gov Identifier: NCT03093818.

PACIFIC-PGx evaluated the feasibility of implementing pharmacogenetics (PGx) screening in Australia and the impact of DPYD/UGT1A1 genotype-guided dosing on severe fluoropyrimidine (FP) and irinotecan-related toxicities and hospitalizations, compared to historical controls. This prospective single arm trial enrolled patients starting FP/irinotecan for any cancer between 7 January 2021 and 25 February 2022 from four Australian hospitals (one metropolitan, three regional). During the accrual period, 462/487 (95%) consecutive patients screened for eligibility for DPYD and 50/109 (46%) for UGT1A1 were enrolled and genotyped (feasibility analysis), with 276/462 (60%) for DPYD and 30/50 (60%) for UGT1A1 received FP/irinotecan (safety analysis). DPYD genotyping identified 96% (n = 443/462) Wild-Type, 4% (n = 19/462) Intermediate Metabolizers (50% dose reduction), and 0% Poor Metabolizers. UGT1A1 genotyping identified 52% (n = 26/50) Wild-Type, 40% (n = 20/50) heterozygous, and 8% (n = 4/50) homozygous (30% dose reduction). Key demographics for the FP/irinotecan safety cohorts included: age range 23-89/34-74 years, male 56%/73%, Caucasian 83%/73%, lower gastrointestinal cancer 50%/57%. Genotype results were reported prior to cycle-1 (96%), average 5-7 days from sample collection. PGx-dosing for DPYD variant allele carriers reduced high-grade toxicities compared to historic controls (7% vs. 39%; OR = 0.11, 95% CI 0.01-0.97, p = 0.024). High-grade toxicities among Wild-Type were similar (14% vs. 14%; OR = 0.99, 95% CI 0.64-1.54, p = 0.490). PGx-dosing reduced FP-related hospitalizations (-22%) and deaths (-3.7%) compared to controls. There were no high-grade toxicities or hospitalizations for UGT1A1*28 homozygotes. PGx screening and prescribing were feasible in routine oncology care and improved patient outcomes. Findings may inform expanded PGx programs within cancer and other disease settings.

Cancer treatment has improved over the past decades, but many cancer patients still experience adverse drug reactions (ADRs). Pharmacogenomics (PGx), known as personalized treatment, is a pillar of precision medicine that aims to optimize the efficacy and safety of medications by studying the germline variations. Germline variations in the DPYD lead to significant ADRs. The present cross-sectional study aims to evaluate the allele frequency of the DPYD gene variations in the Iranian population to provide insights into personalized treatment decisions in the Iranian population.

The allele frequency of 51 pharmacogenetic variations in the clinically relevant DPYD was assessed in a representative sample set of 1142 unrelated Iranian individuals and subpopulations of different ethnic groups who were genotyped using the Infinium Global Screening Array-24 BeadChip.

The genotyping assay revealed eight pharmacogenetic variants including DPYD rs1801265 (c.85T > C; DPYD*9A), rs2297595 (c.496A > G), rs1801158 (c.1601G > A; DPYD*4), rs1801159 (c.1627A > G; DPYD*5), rs1801160 (c.2194G > A; DPYD*6), rs17376848 (c.1896T > C), rs56038477 (c.1236G > A; HapB3), and rs75017182 (c.1129-5923C > G; HapB3) with minor allele frequency (MAF) ≥ 1%.

The results of the study reveal significant genetic variations among Iranian population that could significantly influence clinical decision-making. These variants, with their potential to explain the substantial variability in drug response phenotypes among different populations, shed light on a crucial aspect of pharmacogenomics. These findings not only provide valuable insights but also inspire the design and implementation of future pharmacogenomic clinical trials, motivating further research in this crucial area.

Despite common global usage, fluoropyrimidine (FP; 5-flurouracil and capecitabine)-related chemotherapy toxicity is poorly reported in the literature, with serious toxicity ranging from 10% to 40% and early toxicity (within 60 days of exposure) quoted at 14%. Data reflecting the incidence of Grades 3-5 FP-related toxicity in Australian cancer patients is scant, despite the significant impact of toxicity on patients (hospitalisations, intensive care unit (ICU) admissions and even death).

This retrospective audit evaluated Grades 3-5 toxicities in a contemporaneous cohort of 500 patients receiving FP chemotherapies within the Hunter-New England Local Health District from June 2020 to June 2022. Data were extracted from public hospital records and oncology-specific e-records to determine rates of toxicity and associated hospitalisations, intensive care admissions and deaths that occurred within 60 days of first exposure to FP chemotherapy-containing regimens.

One hundred and fifty incidents of Grades 3-4 toxicity in the first 60 days led to 87 patients presenting to hospital (87/500, 17.4%). The most common serious toxicities were diarrhoea (39.3%), nausea and vomiting (22.7%) and febrile neutropaenia (10%). Four patients were admitted to the ICU, and four patients died of toxicity. Within the first 60 days, 22.2% of patients required treatment delays, 21.4% required dose reductions, and 7.8% of patients ceased treatment because of toxicities.

Our experience reflects international reports and is likely generalisable to the Australian population. These data are a basis to understand the potential benefits of precision medicine strategies such as pharmacogenomic screening to improve patient tolerability and the cost-effectiveness of FP chemotherapy prescribing.

Pharmacogenetic testing can identify patients who may benefit from personalized drug treatment. However, clinical uptake of pharmacogenetic testing has been limited. Clinical practice guidelines recommend biomarker tests that the guideline authors deem to have demonstrated clinical utility, meaning that testing improves treatment outcomes. The objective of this narrative review is to describe the current status of pharmacogenetic testing recommendations within clinical practice guidelines in the US.

Guidelines were reviewed for pharmacogenetic testing recommendations for 21 gene-drug pairs that have well-established drug response associations and all of which are categorized as clinically actionable by the Clinical Pharmacogenetics Implementation Consortium. The degree of consistency within and between organizations in pharmacogenetic testing recommendations was assessed. Relatively few clinical practice guidelines that provide a pharmacogenetic testing recommendation were identified. Testing recommendations for HLA-B*57:01 before initiation of abacavir and G6PD before initiation of rasburicase, both of which are included in drug labeling, were mostly consistent across guidelines. Gene-drug pairs with at least one clinical practice guideline recommending testing or stating that testing could be considered included CYP2C19-clopidogrel, CYP2D6-codeine, CYP2D6-tramadol, CYP2B6-efavirenz, TPMT-thiopurines, and NUDT15-thiopurines. Testing recommendations for the same gene-drug pair were often inconsistent between organizations and sometimes inconsistent between different guidelines from the same organization.

A standardized approach to evaluating the evidence of clinical utility for pharmacogenetic testing may increase the inclusion and consistency of pharmacogenetic testing recommendations in clinical practice guidelines, which could benefit patients and society by increasing clinical use of pharmacogenetic testing.

Pre-treatment DPYD screening is mandated in the UK and EU to reduce the risk of severe and potentially fatal fluoropyrimidine-related toxicity. Four DPYD gene variants which are more prominently found in Europeans are tested.

Our systematic review in patients of non-European ancestry followed PRISMA guidelines to identify relevant articles up to April 2023. Published in silico functional predictions and in vitro functional data were also extracted. We also undertook in silico prediction for all DPYD variants identified.

In 32 studies, published between 1998 and 2022, 53 DPYD variants were evaluated in patients from 12 countries encompassing 5 ethnic groups: African American, East Asian, Latin American, Middle Eastern, and South Asian. One of the 4 common European DPYD variants, c.1905+1G>A, is also present in South Asian, East Asian and Middle Eastern patients with severe fluoropyrimidine-related toxicity. There seems to be relatively strong evidence for the c.557A>G variant, which is found in individuals of African ancestry, but is not currently included in the UK genotyping panel.

Extending UK pre-treatment DPYD screening to include variants that are present in some non-European ancestry groups will improve patient safety and reduce race and health inequalities in ethnically diverse societies.

Fluoropyrimidines (FPs) are commonly prescribed in many cancer streams. The EMA and FDA-approved drug labels for FPs recommend genotyping the DPYD*2A (rs3918290), *13 (rs55886062), *HapB3 (rs56038477), alleles, and DPYD rs67376798 before treatment starts. We implemented the DPYD genotyping in our daily clinical routine, but we still found patients showing severe adverse drug events (ADEs) to FPs. We studied among these patients the DPYD rs1801265, rs17376848, rs1801159, rs1801160, rs1801158, and rs2297595 as explanatory candidates of the interindividual differences for FP-related toxicities, examining the association with the response to FPs . We also studied the impact of DPYD testing for FP dose tailoring in our clinical practice and characterized the DPYD gene in our population. We found a total acceptance among physicians of therapeutic recommendations translated from the DPYD test, and this dose tailoring does not affect the treatment efficacy. We also found that the DPYD*4 (defined by rs1801158) allele is associated with a higher risk of ADEs (severity grade ≥ 3) in both the univariate (O.R. = 5.66; 95% C.I. = 1.35-23.67; p = 0.014) and multivariate analyses (O.R. = 5.73; 95% C.I. = 1.41-28.77; p = 0.019) among FP-treated patients based on the DPYD genotype. This makes it a candidate variant for implementation in clinical practice.

Determination of DPYD and UGT1A1 polymorphisms prior to 5-fluorouracil and irinotecan therapy is crucial for avoiding severe adverse drug effects. Hence, there is a pressing need for accurate and reliable genotyping methods for the most common DPYD and UGT1A1 polymorphisms. In this study, we introduce a novel polymerase chain reaction (PCR) melting curve analysis method for discriminating DPYD c.1236G > A, c.1679 T > G, c.2846A > T, IVS14 + 1G > A and UGT1A1*1, *28, *6 (G71R) genotypes.

Following protocol optimization, this technique was employed to genotype 28 patients, recruited between March 2023 and October 2023, at the First Affiliated Hospital of Xiamen University. These patients included 20 with UGT1A1 *1/*1, 8 with UGT1A1 *1/*28, 4 with UGT1A1 *28/*28, 22 with UGT1A1*6 G/G, 6 with UGT1A1*6 G/A, 4 with UGT1A1*6 A/A, 27 with DPYD(c.1236) G/G, 3 with DPYD(c.1236) G/A, 2 with DPYD(c.1236) A/A, 27 with DPYD(c.1679) T/T, 2 with DPYD(c.1679) T/G, 3 with DPYD(c.1679) G/G, 28 with DPYD(c.2846A/T) A/A, 2 with DPYD(c.2846A/T) A/T, 2 with DPYD(c.2846A/T) T/T, 28 with DPYD(c.IVS14 + 1) G/G, 2 with DPYD(c.IVS14 + 1) G/G, and 2 with DPYD(c.IVS14 + 1) G/G, as well as 3 plasmid standards. Method accuracy was assessed by comparing results with those from Sanger sequencing or Multiplex quantitative PCR(qPCR). Intra- and inter-run precision of melting temperatures (Tms) were calculated to evaluate reliability, and sensitivity was assessed through limit of detection examination.

The new method accurately identified all genotypes and exhibited higher accuracy than Multiplex qPCR. Intra- and inter-run coefficients of variation for Tms were both ≤1.97 %, with standard deviations ≤0.95 °C. The limit of detection was 0.09 ng/μL of input genomic DNA.

Our developed PCR melting curve analysis offers accurate, reliable, rapid, simple, and cost-effective detection of DPYD and UGT1A1 polymorphisms. Its application can be easily extended to clinical laboratories equipped with a fluorescent PCR platform.

Patients with dihydropyrimidine dehydrogenase (DPD) deficiency are at high risk for severe and fatal toxicity from fluoropyrimidine (FP) chemotherapy. Pre-treatment DPYD testing is standard of care in many countries, but not the United States (US). This survey assessed pre-treatment DPYD testing approaches in the US to identify best practices for broader adoption.

From August to October 2023, a 22-item QualtricsXM survey was sent to institutions and clinicians known to conduct pre-treatment DPYD testing and broadly distributed through relevant organizations and social networks. Responses were analyzed using descriptive analysis.

Responses from 24 unique US sites that have implemented pre-treatment DPYD testing or have a detailed implementation plan in place were analyzed. Only 33% of sites ordered DPYD testing for all FP-treated patients; at the remaining sites, patients were tested depending on disease characteristics or clinician preference. Almost 50% of sites depend on individual clinicians to remember to order testing without the assistance of electronic alerts or workflow reminders. DPYD testing was most often conducted by commercial laboratories that tested for at least the four or five DPYD variants considered clinically actionable. Approximately 90% of sites reported receiving results within 10 days of ordering.

Implementing DPYD testing into routine clinical practice is feasible and requires a coordinated effort among the healthcare team. These results will be used to develop best practices for the clinical adoption of DPYD testing to prevent severe and fatal toxicity in cancer patients receiving FP chemotherapy.

Fluoropyrimidine-related toxicity and mortality risk increases significantly in patients carrying certain DPYD genetic variants with standard dosing. We implemented DPYD genotyping at a multisite cancer center and evaluated its impact on dosing, toxicity, and hospitalization.

In this prospective observational study, patients receiving (reactive) or planning to receive (pretreatment) fluoropyrimidine-based chemotherapy were genotyped for five DPYD variants as standard practice per provider discretion. The primary end point was the proportion of variant carriers receiving fluoropyrimidine modifications. Secondary end points included mean relative dose intensity, fluoropyrimidine-related grade 3+ toxicities, and hospitalizations. Fisher's exact test compared toxicity and hospitalization rates between pretreatment carriers, reactive carriers, and wild-type patients. Univariable and multivariable logistic regression identified factors associated with toxicity and hospitalization risk. Kaplan-Meier methods estimated time to event of first grade 3+ toxicity and hospitalization.

Of the 757 patients who received DPYD genotyping (median age 63, 54% male, 74% White, 19% Black, 88% GI malignancy), 45 (5.9%) were heterozygous carriers. Fluoropyrimidine was modified in 93% of carriers who started treatment. In 442 patients with 3-month follow-up, 64%, 31%, and 30% of reactive carriers, pretreatment carriers, and wild-type patients had grade 3+ toxicity, respectively (P = .085); 64%, 25%, and 13% were hospitalized (P < .001). Reactive carriers had 10-fold higher odds of hospitalization compared with wild-type patients (P = .001), whereas no significant difference was noted between pretreatment carriers and wild-type patients. Time-to-event of toxicity and hospitalization were significantly different between genotype groups (P < .001), with reactive carriers having the earliest onset and highest incidence.

DPYD genotyping prompted fluoropyrimidine modifications in most carriers. Pretreatment testing reduced toxicities and hospitalizations compared with reactive testing, thus normalizing the risk to that of wild-type patients, and should be considered standard practice.

The discovery of circadian clock genes greatly amplified the study of diurnal variations impacting cancer therapy, transforming it into a rapidly growing field of research. Especially, use of chronomodulated treatment with 5-fluorouracil (5-FU) has gained significance. Studies indicate high interindividual variability (IIV) in diurnal variations in dihydropyrimidine dehydrogenase (DPD) activity - a key enzyme for 5-FU metabolism. However, the influence of individual DPD chronotypes on chronomodulated therapy remains unclear and warrants further investigation. To optimize precision dosing of chronomodulated 5-FU, this study aims to: (i) build physiologically-based pharmacokinetic (PBPK) models for 5-FU, uracil, and their metabolites, (ii) assess the impact of diurnal variation on DPD activity, (iii) estimate individual DPD chronotypes, and (iv) personalize chronomodulated 5-FU infusion rates based on a patient's DPD chronotype. Whole-body PBPK models were developed with PK-Sim(R) and MoBi(R). Sinusoidal functions were used to incorporate variations in enzyme activity and chronomodulated infusion rates as well as to estimate individual DPD chronotypes from DPYD mRNA expression or DPD enzymatic activity. Four whole-body PBPK models for 5-FU, uracil, and their metabolites were established utilizing data from 41 5-FU and 10 publicly available uracil studies. IIV in DPD chronotypes was assessed and personalized chronomodulated administrations were developed to achieve (i) comparable 5-FU peak plasma concentrations, (ii) comparable 5-FU exposure, and (iii) constant 5-FU plasma levels via "noise cancellation" chronomodulated infusion. The developed PBPK models capture the extent of diurnal variations in DPD activity and can help investigate individualized chronomodulated 5-FU therapy through testing alternative personalized dosing strategies.

Third-generation aromatase inhibitors (AI) are the standard treatment for patients with hormone receptor positive (HR+) breast cancer. While effective, AI can lead to severe adverse events, including AI-induced musculoskeletal syndrome (AIMSS). Genetic predictors of AIMSS have the potential to personalize AI treatment and improve outcomes. We attempted to replicate results from a previous genome-wide association study that found a lower risk of AIMSS in patients carrying PPP1R14C rs912571 and a higher risk in patients carrying CCDC148 rs79048288. AIMSS data were collected prospectively from patients with HR+ breast cancer prior to starting and after 3 and 6 months of adjuvant AI via the Patient-Reported Outcome Measurement Information System and Functional Assessment of Cancer Therapy-Endocrine Symptom. Germline genotypes for PPP1R14C rs912571 and CCDC148 rs79048288 were tested for a similar association with AIMSS as previously reported via $2 tests. Of the 143 patients with AIMSS and genetics data were included in the analysis. There was no association identified between PPP1R14C rs912571 and AIMSS risk ( P  > 0.05). Patients carrying CCDC148 rs79048288 variant alleles had lower AIMSS incidence in a secondary analysis ( P  = 0.04); however, this was in the opposite direction of the previous finding. The study did not replicate previously reported associations with AIMSS risk for genetic variants in PPP1R14C and CCDC148 and AIMSS risk. Further research is needed to discover and validate genetic predictors of AIMSS that can be used to personalize treatment in patients with HR+ breast cancer.

A DPD deficiency should be considered in case of severe toxicity even in the absence of common risk variants in DPYD.

The clinical application of Pharmacogenomics (PGx) has improved patient safety. However, comprehensive PGx testing has not been widely adopted in clinical practice, and significant opportunities exist to further optimize PGx in cancer care. This systematic review and meta-analysis aim to evaluate the safety outcomes of reported PGx-guided strategies (Analysis 1) and identify well-studied emerging pharmacogenomic variants that predict severe toxicity and symptom burden (Analysis 2) in patients with cancer. We searched MEDLINE, EMBASE, CENTRAL, clinicaltrials.gov, and International Clinical Trials Registry Platform from inception to January 2023 for clinical trials or comparative studies evaluating PGx strategies or unconfirmed pharmacogenomic variants. The primary outcomes were severe adverse events (SAE; ≥ grade 3) or symptom burden with pain and vomiting as defined by trial protocols and assessed by trial investigators. We calculated pooled overall relative risk (RR) and 95% confidence interval (95%CI) using random effects models. PROSPERO, registration number CRD42023421277. Of 6811 records screened, six studies were included for Analysis 1, 55 studies for Analysis 2. Meta-analysis 1 (five trials, 1892 participants) showed a lower absolute incidence of SAEs with PGx-guided strategies compared to usual therapy, 16.1% versus 34.0% (RR = 0.72, 95%CI 0.57-0.91, p = 0.006, I2 = 34%). Meta-analyses 2 identified nine medicine(class)-variant pairs of interest across the TYMS, ABCB1, UGT1A1, HLA-DRB1, and OPRM1 genes. Application of PGx significantly reduced rates of SAEs in patients with cancer. Emergent medicine-variant pairs herald further research into the expansion and optimization of PGx to improve systemic anti-cancer and supportive care medicine safety and efficacy.

In this report, two cases of patients with severe adverse events after an adjuvant treatment with capecitabine are described in detail. The first patient suffered from a severe ileocolitis, where ultimately intensive care treatment, total colectomy and ileum resection was necessary. The second patient experienced a toxic enteritis, which could be managed conservatively. Post-therapeutic DPYD genotyping was negative in the former and positive in the latter case. Patients can be categorised in normal, moderate and poor DPYD metabolisers to predict the risk of adverse events of capecitabine treatment. Guidelines in various European countries recommend pretherapeutic DPYD genotyping, whereas it is not recommended by the National Comprehensive Cancer Network in the USA. Irrespective of DPYD genotyping, strict therapeutic drug monitoring is highly recommended to reduce the incidence and severity of adverse events.