Jennifer M. Skierka

Preemptive genotyping for personalized medicine: design of the right drug, right dose, right time-using genomic data to individualize treatment protocol.

OBJECTIVE To report the design and implementation of the Right Drug, Right Dose, Right Time-Using Genomic Data to Individualize Treatment protocol that was developed to test the concept that prescribers can deliver genome-guided therapy at the point of care by using preemptive pharmacogenomics (PGx) data and clinical decision support (CDS) integrated into the electronic medical record (EMR). PATIENTS AND METHODS We used a multivariate prediction model to identify patients with a high risk of initiating statin therapy within 3 years. The model was used to target a study cohort most likely to benefit from preemptive PGx testing among the Mayo Clinic Biobank participants, with a recruitment goal of 1000 patients. We used a Cox proportional hazards model with variables selected through the Lasso shrinkage method. An operational CDS model was adapted to implement PGx rules within the EMR. RESULTS The prediction model included age, sex, race, and 6 chronic diseases categorized by the Clinical Classifications Software for International Classification of Diseases, Ninth Revision codes (dyslipidemia, diabetes, peripheral atherosclerosis, disease of the blood-forming organs, coronary atherosclerosis and other heart diseases, and hypertension). Of the 2000 Biobank participants invited, 1013 (51%) provided blood samples, 256 (13%) declined participation, 555 (28%) did not respond, and 176 (9%) consented but did not provide a blood sample within the recruitment window (October 4, 2012, through March 20, 2013). Preemptive PGx testing included CYP2D6 genotyping and targeted sequencing of 84 PGx genes. Synchronous real-time CDS was integrated into the EMR and flagged potential patient-specific drug-gene interactions and provided therapeutic guidance. CONCLUSION This translational project provides an opportunity to begin to evaluate the impact of preemptive sequencing and EMR-driven genome-guided therapy. These interventions will improve understanding and implementation of genomic data in clinical practice.

Preemptive Pharmacogenomic Testing for Precision Medicine: A Comprehensive Analysis of Five Actionable Pharmacogenomic Genes Using Next-Generation DNA Sequencing and a Customized CYP2D6 Genotyping Cascade

Significant barriers, such as lack of professional guidelines, specialized training for interpretation of pharmacogenomics (PGx) data, and insufficient evidence to support clinical utility, prevent preemptive PGx testing from being widely clinically implemented. The current study, as a pilot project for the Right Drug, Right Dose, Right Time-Using Genomic Data to Individualize Treatment Protocol, was designed to evaluate the impact of preemptive PGx and to optimize the workflow in the clinic setting. We used an 84-gene next-generation sequencing panel that included SLCO1B1, CYP2C19, CYP2C9, and VKORC1 together with a custom-designed CYP2D6 testing cascade to genotype the 1013 subjects in laboratories approved by the Clinical Laboratory Improvement Act. Actionable PGx variants were placed in patients electronic medical records where integrated clinical decision support rules alert providers when a relevant medication is ordered. The fraction of this cohort carrying actionable PGx variant(s) in individual genes ranged from 30% (SLCO1B1) to 79% (CYP2D6). When considering all five genes together, 99% of the subjects carried an actionable PGx variant(s) in at least one gene. Our study provides evidence in favor of preemptive PGx testing by identifying the risk of a variant being present in the population we studied.

CYP2D6*11 and challenges in clinical genotyping of the highly polymorphic CYP2D6 gene

CYP2D6 is genotyped clinically for prediction of response to tamoxifen, psychotropic drugs and other medications. Phenotype prediction is dependent upon accurate genotyping. The CYP Allele Nomenclature Committee maintains the allelic nomenclature for CYP2D6; however, in some cases, the list of polymorphisms associated with a given allele is incomplete. Clinical laboratories and in vitro diagnostic manufacturers rely upon this nomenclature, in addition to the literature, to infer allelic function and haplotypes and when they design CYP2D6-testing platforms. This article provides more complete sequencing data for the CYP2D6*11 allele and describes the difficulties encountered in genotyping CYP2D6 when incomplete data are available. The CYP Allele Nomenclature Committee should provide clear information about the completeness of the original data used to define each allele.

Analysis of compound heterozygous CYP2C19 genotypes to determine cis and trans configurations

BACKGROUND Through allele specific PCR we studied 220 CYP2C19 compound heterozygous samples, of unknown ethnicity, to determine the haplotype for each of the variations within a sample. MATERIALS & METHODS The genotypes assessed were: 180 *2 and *17 samples (100% in trans); 20 *2 and *11 samples (100% in cis); ten *4 and *17 samples (50% of the samples were *1/*4B and 50% *4A/*17); six *2, *11 and *17 samples (100% showed *2 and *11 in cis, and *17 in trans); two *2, *4 and *17 samples (100% *4B with *2 in trans); one sample with *17 and *34 (these were in trans); and one sample that contained *2, *17, c.463G>T (p.E155X; *17 and c.463G>T were in cis, with *2 in trans). RESULTS & CONCLUSION In our study, we observed a different frequency for the *4B allele (when a sample contains both *4 and *17); and identified *17 occurring in cis with a novel nonsense allele. Accurately assessing a patients genotype, including assignment of a haplotype, can be important when making a phenotype prediction.

UDP-Glucuronosyltransferase 1A1 and the Glucuronidation in Oncology Applications and Hyperbilirubinemia

Publisher Summary Glucuronidation is an important phase II reaction catalyzed by the UDP-glucuronosyltransferases (UGTs), UGTs are enzymes involved in a number of metabolic processes, including phase II drug metabolism conjugation of endogenous compounds with glucuronic acid, such as bilirubin and estradiol with glucuronic acid, to form water-soluble conjugates for excretion; and detoxification of potential carcinogens. Clinicians need to be aware of the options available to them for irinotecan and hyperbilirubinemia genetic testing. When complying with the minimum FDA requirements for irinotecan dose adjustments by only testing to determine if the *28 allele is present, patients of African or Asian ancestry could potentially be put at increased risk for neutropenia with this drug. Many factors go into determining hyperbilirubinemia; having a comprehensive genetic test available to aid a physician in treatment options (UGT1A1 genetic based or not) provides the patient with the best clinical outcome. The UGT1A1 gene is a complex gene, not only in its design, with alternative splicing on the 5’ and 3’ end of the gene, but also because of the impact it has on genetic diseases and drug metabolism. In addition, the variations that have been reported (known star alleles) all have different frequencies depending on ethnicity. As a result, an allele (for example, *6) may have vast clinical significance in one ethnicity but is rarely observed in other populations. Only by continuing to investigate and research the gene in various populations can we further our understanding on the clinical significance and impact of UGT1A1.