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.

Incorporating G6PD genotyping to identify patients with G6PD deficiency.

Glucose-6-phosphate-dehydrogenase (G6PD) deficiency is a common X-linked enzyme disorder associated with hemolytic anemia after exposure to fava beans or certain medications. Activity testing is the gold standard for detecting G6PD deficiency; however, this test is affected by various hematologic parameters. Clinical G6PD genotyping is now included in pharmacogenetic arrays and clinical sequencing efforts and may be reconciled with activity results. Patients (n = 1391) enrolled on an institutional pharmacogenetic testing protocol underwent clinical G6PD genotyping for 164 G6PD variants. An algorithm accounting for known interferences with the activity assay is proposed. We developed clinical decision support alerts to inform prescribers when high-risk medications were prescribed, warning of gene-drug interactions and recommending therapy alteration. Of 1391 patients with genotype results, 1334 (95.9%) patients were predicted to have normal G6PD activity, 30 (2.1%) were predicted to have variable G6PD activity and 27 (2%) were predicted to have deficient G6PD activity. Of the 417 patients with a normal genotype and an activity result, 415 (99.5%) had a concordant normal G6PD phenotype. Of the 21 patients with a deficient genotype and an activity result, 18 (85.7%) had a concordant deficient activity result. Genotyping reassigned phenotype in five patients with discordant genotype and activity results: three switched from normal to deficient, and two switched from deficient to normal. G6PD activity and genotyping are two independent testing methods that can be used in conjunction to assign a more informed G6PD phenotype than either method alone.

Concordance between glucose-6-phosphate dehydrogenase (G6PD) genotype and phenotype and rasburicase use in patients with hematologic malignancies.

Phenotypic rather than genotypic tests remain the gold standard for diagnosing glucose-6-phosphate dehydrogenase (G6PD) deficiency. However, with increasing use of genomic arrays and whole exome or genome sequencing, G6PD genetic data are increasingly available. We examined the utility of G6PD genetic data in patients with hematologic malignancies and the association of G6PD genotype and phenotype with rasburicase-induced methemoglobinemia. We analyzed G6PD activity for 990 patients. Genotype data were available from the Affymetrix DMET array (n = 379), whole exome sequencing (n = 374), and/or the Illumina exome array (n = 634) for 645 patients. Medical records of 341 patients with methemoglobin measures were assessed for the administration of rasburicase. We observed 5 non-synonymous SNPs, 4 of which were known to be associated with deficient G6PD activity (WHO Class I-III). Genotyping 367 males resulted in a positive predictive value of 81.8% (47.8-96.8%), and two males with a Class I-III allele having normal activity both received a red blood cell transfusion prior to the activity assay. However, genotyping males had only 39.1% (20.5-61.2%) sensitivity. Two of the 12 heterozygous females had deficient G6PD activity. Rasburicase-induced methemoglobinemia occurred in 6 patients, 5 of whom had at least one Class I-III allele, despite 2 of these having normal G6PD activity. We conclude that although an apparent nondeficient genotype does not necessarily imply a normal phenotype, a deficient genotype result indicates a deficient phenotype in those without transfusions, and may be a useful adjuct to phenotype to prevent adverse drug reactions.

Preemptive pharmacogenetic testing: exploring the knowledge and perspectives of US payers.

PURPOSE: Preemptive pharmacogenetic testing aims to optimize medication use by having genetic information at the point of prescribing. Payers' decisions influence implementation of this technology. We investigated US payers' knowledge, awareness, and perspectives on preemptive pharmacogenetic testing. METHODS: A qualitative study was conducted using semistructured interviews. Participants were screened for eligibility through an online survey. A blended inductive and deductive approach was used to analyze the transcripts. Two authors conducted an iterative reading process to code and categorize the data. RESULTS: Medical or pharmacy directors from 14 payer organizations covering 122 million US lives were interviewed. Three concept domains and ten dimensions were developed. Key findings include clinical utility concerns and limited exposure to preemptive germ-line testing, continued preference for outcomes from randomized controlled trials, interest in guideline development, importance of demonstrating an impact on clinical decision making, concerns of downstream costs and benefit predictability, and the impact of public stakeholders such as the Food and Drug Administration and Centers for Medicare and Medicaid Services. CONCLUSION: Both barriers and potential facilitators exist to developing cohesive reimbursement policy for pharmacogenetics, and there are unique challenges for the preemptive testing model. Prospective outcome studies, more precisely defining target populations, and predictive economic models are important considerations for future research.

PG4KDS: a model for the clinical implementation of pre-emptive pharmacogenetics.

Pharmacogenetics is frequently cited as an area for initial focus of the clinical implementation of genomics. Through the PG4KDS protocol, St. Jude Children's Research Hospital pre-emptively genotypes patients for 230 genes using the Affymetrix Drug Metabolizing Enzymes and Transporters (DMET) Plus array supplemented with a CYP2D6 copy number assay. The PG4KDS protocol provides a rational, stepwise process for implementing gene/drug pairs, organizing data, and obtaining consent from patients and families. Through August 2013, 1,559 patients have been enrolled, and four gene tests have been released into the electronic health record (EHR) for clinical implementation: TPMT, CYP2D6, SLCO1B1, and CYP2C19. These genes are coupled to 12 high-risk drugs. Of the 1,016 patients with genotype test results available, 78% of them had at least one high-risk (i.e., actionable) genotype result placed in their EHR. Each diplotype result released to the EHR is coupled with an interpretive consult that is created in a concise, standardized format. To support-gene based prescribing at the point of care, 55 interruptive clinical decision support (CDS) alerts were developed. Patients are informed of their genotyping result and its relevance to their medication use through a letter. Key elements necessary for our successful implementation have included strong institutional support, a knowledgeable clinical laboratory, a process to manage any incidental findings, a strategy to educate clinicians and patients, a process to return results, and extensive use of informatics, especially CDS. Our approach to pre-emptive clinical pharmacogenetics has proven feasible, clinically useful, and scalable.

Sulfamethoxazole-Trimethoprim Prophylaxis in Pediatric Oncology Patients With Glucose-6-Phosphate Dehydrogenase Deficiency.

We sought to determine whether Pneumocystis jirovecii pneumonia prophylaxis with sulfamethoxazole-trimethoprim (SMX-TMP) is associated with an increased frequency of acute hemolytic anemia in patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency versus non-G6PD-deficient controls in a pediatric oncology population. There was no statistically significant difference in change in hemoglobin or transfusion requirements after starting SMX-TMP between groups. These findings suggest no increased risk of acute hemolytic anemia with SMX-TMP administered at prophylaxis doses in patients with G6PD deficiency.

Updated DPYD HapB3 haplotype structure and implications for pharmacogenomic testing.

The DPYD gene encodes dihydropyrimidine dehydrogenase, the rate-limiting enzyme for the metabolism of fluoropyrimidines 5-fluorouracil and capecitabine. Genetic variants in DPYD have been associated with altered enzyme activity, therefore accurate detection and interpretation is critical to predict metabolizer status for individualized fluoropyrimidine therapy. The most commonly observed deleterious variation is the causal variant linked to the previously described HapB3 haplotype, c.1129-5923C>G (rs75017182) in intron 10, which introduces a cryptic splice site. A benign synonymous variant in exon 11, c.1236G>A (rs56038477) is also linked to HapB3 and is commonly used for testing. Previously, these single-nucleotide polymorphisms (SNPs) have been reported to be in perfect linkage disequilibrium (LD); therefore, c.1236G>A is often utilized as a proxy for the function-altering intronic variant. Clinical genotyping of DPYD identified a patient who had c.1236G>A, but not c.1129-5923C>G, suggesting that these two SNPs may not be in perfect LD, as previously assumed. Additional individuals with c.1236G>A, but not c.1129-5923C>G, were identified in the Children's Mercy Data Warehouse and the All of Us Research Program version 7 cohort substantiating incomplete SNP linkage. Consequently, testing only c.1236G>A can generate false-positive results in some cases and lead to suboptimal dosing that may negatively impact patient therapy and prospect of survival. Our data show that DPYD genotyping should include the functional variant c.1129-5923C>G, and not the c.1236G>A proxy, to accurately predict DPD activity.

Clinical Pharmacogenetics Implementation Consortium Guideline for CYP2B6 Genotype and Methadone Therapy.

Methadone is a mu (µ) opioid receptor agonist used clinically in adults and children to manage opioid use disorder, neonatal abstinence syndrome, and acute and chronic pain. It is typically marketed as a racemic mixture of R- and S-enantiomers. R-methadone has 30-to 50-fold higher analgesic potency than S-methadone, and S-methadone has a greater adverse effect (prolongation) on the cardiac QTc interval. Methadone undergoes stereoselective metabolism. CYP2B6 is the primary enzyme responsible for catalyzing the metabolism of both enantiomers to the inactive metabolites, S- and R-2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (S- and R-EDDP). Genetic variation in the CYP2B6 gene has been investigated in the context of implications for methadone pharmacokinetics, dose, and clinical outcomes. Most CYP2B6 variants result in diminished or loss of CYP2B6 enzyme activity, which can lead to higher plasma methadone concentrations (affecting S- more than R-methadone). However, the data do not consistently indicate that CYP2B6-based metabolic variability has a clinically significant effect on methadone dose, efficacy, or QTc prolongation. Expert analysis of the published literature does not support a change from standard methadone prescribing based on CYP2B6 genotype (updates at www.cpicpgx.org).

Additive effects of TPMT and NUDT15 on thiopurine toxicity in children with acute lymphoblastic leukemia across multiethnic populations.

BACKGROUND: Thiopurines such as mercaptopurine (MP) are widely used to treat acute lymphoblastic leukemia (ALL). Thiopurine-S-methyltransferase (TPMT) and Nudix hydrolase 15 (NUDT15) inactivate thiopurines, and no-function variants are associated with drug-induced myelosuppression. Dose adjustment of MP is strongly recommended in patients with intermediate or complete loss of activity of TPMT and NUDT15. However, the extent of dosage reduction recommended for patients with intermediate activity in both enzymes is currently not clear. METHODS: MP dosages during maintenance were collected from 1768 patients with ALL in Singapore, Guatemala, India, and North America. Patients were genotyped for TPMT and NUDT15, and actionable variants defined by the Clinical Pharmacogenetics Implementation Consortium were used to classify patients as TPMT and NUDT15 normal metabolizers (TPMT/NUDT15 NM), TPMT or NUDT15 intermediate metabolizers (TPMT IM or NUDT15 IM), or TPMT and NUDT15 compound intermediate metabolizers (TPMT/NUDT15 IM/IM). In parallel, we evaluated MP toxicity, metabolism, and dose adjustment using a Tpmt/Nudt15 combined heterozygous mouse model (Tpmt+/-/Nudt15+/-). RESULTS: Twenty-two patients (1.2%) were TPMT/NUDT15 IM/IM in the cohort, with the majority self-reported as Hispanics (68.2%, 15/22). TPMT/NUDT15 IM/IM patients tolerated a median daily MP dose of 25.7 mg/m2 (interquartile range = 19.0-31.1 mg/m2), significantly lower than TPMT IM and NUDT15 IM dosage (P < .001). Similarly, Tpmt+/-/Nudt15+/- mice displayed excessive hematopoietic toxicity and accumulated more metabolite (DNA-TG) than wild-type or single heterozygous mice, which was effectively mitigated by a genotype-guided dose titration of MP. CONCLUSION: We recommend more substantial dose reductions to individualize MP therapy and mitigate toxicity in TPMT/NUDT15 IM/IM patients.

Expanded Clinical Pharmacogenetics Implementation Consortium Guideline for Medication Use in the Context of G6PD Genotype.

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is associated with development of acute hemolytic anemia in the setting of oxidative stress, which can be caused by medication exposure. Regulatory agencies worldwide warn against the use of certain medications in persons with G6PD deficiency, but in many cases, this information is conflicting, and the clinical evidence is sparse. This guideline provides information on using G6PD genotype as part of the diagnosis of G6PD deficiency and classifies medications that have been previously implicated as unsafe in individuals with G6PD deficiency by one or more sources. We classify these medications as high, medium, or low to no risk based on a systematic review of the published evidence of the gene-drug associations and regulatory warnings. In patients with G6PD deficiency, high-risk medications should be avoided, medium-risk medications should be used with caution, and low-to-no risk medications can be used with standard precautions, without regard to G6PD phenotype. This new document replaces the prior Clinical Pharmacogenetics Implementation Consortium guideline for rasburicase therapy in the context of G6PD genotype (updates at: www.cpicpgx.org).

Clinician adherence to pharmacogenomics prescribing recommendations in clinical decision support alerts.

Thoughtful integration of interruptive clinical decision support (CDS) alerts within the electronic health record is essential to guide clinicians on the application of pharmacogenomic results at point of care. St. Jude Children's Research Hospital implemented a preemptive pharmacogenomic testing program in 2011 in a multidisciplinary effort involving extensive education to clinicians about pharmacogenomic implications. We conducted a retrospective analysis of clinicians' adherence to 4783 pharmacogenomically guided CDS alerts that triggered for 12 genes and 60 drugs. Clinicians adhered to the therapeutic recommendations provided in 4392 alerts (92%). In our population of pediatric patients with catastrophic illnesses, the most frequently presented gene/drug CDS alerts were TPMT/NUDT15 and thiopurines (n = 3850), CYP2D6 and ondansetron (n = 667), CYP2D6 and oxycodone (n = 99), G6PD and G6PD high-risk medications (n = 51), and CYP2C19 and proton pump inhibitors (omeprazole and pantoprazole; n = 50). The high adherence rate was facilitated by our team approach to prescribing and our collaborative CDS design and delivery.

Utilizing Multilingual Methods and Rapid Analysis for Global Qualitative Research During a Pandemic.

Historically, qualitative research has complemented quantitative biologic and epidemiologic studies to provide a more complete understanding of pandemics. The COVID-19 pandemic has generated unique and novel challenges for qualitative researchers, who have embraced creative solutions including virtual focus groups and rapid analyses to continue their work. We present our experience conducting a multilingual global qualitative study of healthcare resilience among teams of pediatric oncology professionals during the COVID-19 pandemic. We provide an in-depth description of our methodology and an analysis of factors we believe contributed to our study's success including our use of technology, engagement of a large multilingual team, global partnerships, and framework-based rapid analysis. We hope these techniques may be useful to qualitative researchers conducting studies during the current pandemic, as well as for all pediatric oncology studies including multiple languages or geographically disparate subjects.

Clinical Pharmacogenetics Implementation Consortium Guideline for CYP2D6, OPRM1, and COMT Genotypes and Select Opioid Therapy.

Opioids are mainly used to treat both acute and chronic pain. Several opioids are metabolized to some extent by CYP2D6 (codeine, tramadol, hydrocodone, oxycodone, and methadone). Polymorphisms in CYP2D6 have been studied for an association with the clinical effect and safety of these drugs. Other genes that have been studied for their association with opioid clinical effect or adverse events include OPRM1 (mu receptor) and COMT (catechol-O-methyltransferase). This guideline updates and expands the 2014 Clinical Pharmacogenetics Implementation Consortium (CPIC) guideline for CYP2D6 genotype and codeine therapy and includes a summation of the evidence describing the impact of CYP2D6, OPRM1, and COMT on opioid analgesia and adverse events. We provide therapeutic recommendations for the use of CYP2D6 genotype results for prescribing codeine and tramadol and describe the limited and/or weak data for CYP2D6 and hydrocodone, oxycodone, and methadone, and for OPRM1 and COMT for clinical use.

Standardizing CYP2D6 Genotype to Phenotype Translation: Consensus Recommendations from the Clinical Pharmacogenetics Implementation Consortium and Dutch Pharmacogenetics Working Group.

Translating CYP2D6 genotype to metabolizer phenotype is not standardized across clinical laboratories offering pharmacogenetic (PGx) testing and PGx clinical practice guidelines, such as the Clinical Pharmacogenetics Implementation Consortium (CPIC) and the Dutch Pharmacogenetics Working Group (DPWG). The genotype to phenotype translation discordance between laboratories and guidelines can cause discordant cytochrome P450 2D6 (CYP2D6) phenotype assignments and, thus lead to inconsistent therapeutic recommendations and confusion among patients and clinicians. A modified-Delphi method was used to obtain consensus for a uniform system for translating CYP2D6 genotype to phenotype among a panel of international CYP2D6 experts. Experts with diverse involvement in CYP2D6 interpretation (clinicians, researchers, genetic testing laboratorians, and PGx implementers; n = 37) participated in conference calls and surveys. After completion of 7 surveys, a consensus (> 70%) was reached with 82% of the CYP2D6 experts agreeing to the final CYP2D6 genotype to phenotype translation method. Broad adoption of the proposed CYP2D6 genotype to phenotype translation method by guideline developers, such as CPIC and DPWG, and clinical laboratories as well as researchers will result in more consistent interpretation of CYP2D6 genotype.

Factors Associated with Declining to Participate in a Pediatric Oncology Next Generation Sequencing Study.

PURPOSE: For the advances of pediatric oncology next generation sequencing (NGS) research to equitably benefit all children, a diverse and representative sample of participants is needed. However, little is known about demographic and clinical characteristics that differentiate families who decline enrollment in pediatric oncology NGS research. METHODS: Demographic and clinical data were retrospectively extracted for 363 pediatric oncology patients (0-21 years) approached for enrollment on Genomes for Kids (G4K), a study examining the feasibility of comprehensive clinical genomic analysis of tumors and paired normal samples. Demographic and clinical factors that significantly differentiated which families declined were subsequently compared to enrollment in Clinical Implementation of Pharmacogenetics (PG4KDS) for 348 families, a pharmacogenomics study with more explicit therapeutic benefit examining genes affecting drug responses and metabolism. RESULTS: Fifty-three (14.6%) families declined enrollment in G4K. Race/ethnicity was the only variable that significantly differentiated study refusal using multivariate logistic regression, with families of black children more likely to decline enrollment compared to families of non-Hispanic or Hispanic white children. Reasons for declining G4K were generally consistent with other pediatric genomics research, with feeling overwhelmed and insurance discrimination fears most frequently cited. Families of black children were also more likely to decline enrollment in PG4KDS. Thirteen (3.7%) of the 348 families approached for both studies declined PG4KDS. CONCLUSION: Race/ethnicity differentiated study declination across two different pediatric oncology genomics studies, suggesting enrollment disparities in the context of pediatric oncology genomics research. Genomics research participant samples that do not fully represent racial and ethnic minorities risk further exacerbating health disparities. Additional work is needed to understand the nuances of parental decision making in genomic research and facilitate enrollment of diverse patient populations.

Development of a postgraduate year 2 pharmacy residency in clinical pharmacogenetics.

PURPOSE: The structure and development of an innovative, ASHP-accredited postgraduate year 2 (PGY2) clinical pharmacogenetics residency program are described. SUMMARY: A 12-month PGY2 clinical pharmacogenetics residency was created at St. Jude Children's Research Hospital in accordance with the ASHP standards for advanced practice residencies. The purpose of this 12-month residency program is to prepare pharmacy residents to implement pharmacogenetics in clinical practice. The program helps residents develop expertise in the science of pharmacogenetics as well as an understanding of translational research, innovative pharmacy practice model development, and clinical informatics. The resident learns to optimize patient outcomes through the expert provision of evidence-based, patient-centered precision medicine as an integral part of an interprofessional team. After completing the program, residents are expected to have the clinical skills necessary to practice in the field of clinical pharmacogenetics and independently implement pharmacogenetic testing in other health-system settings. Because implementation of pharmacogenetics requires collaboration across many disciplines, residents works within an interprofessional team of physicians, nurses, informatics specialists, pharmacists, and clinical laboratory personnel to achieve program goals. Since the first resident graduated in 2012, the program has graduated 1 resident each year. Graduated residents have accepted pharmacogenetics positions at major academic medical centers and community hospitals, as well as academic and research positions with a pharmacogenetics emphasis. CONCLUSION: A PGY2 clinical pharmacogenetics residency was successfully developed at St. Jude in 2013. After completion of the program, residents are equipped with the clinical skills and necessary experience to drive precision medicine forward and lead the implementation of pharmacogenetic testing in other healthcare settings.

The impact of the UGT1A1*60 allele on bilirubin serum concentrations.

AIM: Identify the functional status of the uridine-diphosphate glucuronyl transferase 1A1 (UGT1A1) -3279T>G (*60) variant. MATERIALS & METHODS: Retrospective review of clinically obtained serum bilirubin concentrations in pediatric patients to evaluate the association of the UGT1A1 -3279T>G (*60) variant with bilirubin concentrations and assessed linkage disequilibrium of the UGT1A1 -3279T>G (*60) and A(TA)7TAA (*28) variants. RESULTS: Total bilirubin concentration did not differ between patients who had a UGT1A1*1/*1 diplotype and patients homozygous for the UGT1A1 -3279T>G (*60/*60) variant. Total bilirubin concentration was lower in patients homozygous for the UGT1A1 -3279T>G (*60/*60) variant than in patients homozygous for the UGT1A1 A(TA)7TAA (*28/*28) variant (p < 0.01). The -3279T>G (*60) and A(TA)7TAA (*28) variants were in strong incomplete linkage disequilibrium in both black and white patients. CONCLUSION: The presence of the UGT1A1 -3279T>G (*60) variant is not associated with increased bilirubin concentrations.