Pharmacogenomics: personalizing pediatric heart transplantation

Trends in Contemporary Use of Ventricular Assist Devices in Children Awaiting Heart Transplantation and Their Outcomes by Race/Ethnicity

This retrospective study included children aged ≤18 years who had durable ventricular assist devices (VADs) as a bridge to transplantation from the United Network Organ Sharing (UNOS) database between 2011 and 2020. We evaluated 90 day waitlist mortality and 1 year posttransplant mortality after VAD implantation in children stratified by race/ethnicity: Black, White, and Others. The VAD was used in a higher proportion of Black children listed for heart transplantation (HT) (26%) versus Other (25%) versus White (22%); p < 0.01. Black children had Medicaid health insurance coverage (67%) predominantly at the time of listing for HT. There was no significant overall difference in waitlist survival among the three groups supported with VAD at the time of listing (log-rank p = 0.4). On the other hand, the 90 day waitlist mortality after the VAD implantation at listing and while listed was the lowest among Black (6%) compared with White (13%) and Other (14%) ( p < 0.01). The multivariate regression analysis showed that Other race (hazard ratio [HR], 2.29; p < 0.01), Black race (HR, 2.13; p < 0.01), use of mechanical ventilation (HR, 1.72; p = 0.01), and Medicaid insurance (HR, 1.54; p = 0.04) were independently associated with increased 1 year posttransplant mortality. In conclusion, Black children had more access to durable VAD support than White children. The 90 day waitlist mortality was significantly lower in Black children compared with White and Other after VAD implantation. However, Black and Other racial/ethnic children with VAD at transplant had higher 1 year posttransplant mortality than White children. Future studies to elucidate the reasons for these disparities are needed.

Pharmacogenetic Aspects of Drug Metabolizing Enzymes and Transporters in Pediatric Medicine: Study Progress, Clinical Practice and Future Perspectives

As the activity of certain drug metabolizing enzymes or transporter proteins can vary with age, the effect of ontogenetic and genetic variation on the activity of these enzymes is critical for the accurate prediction of treatment outcomes and toxicity in children. This makes pharmacogenetic research in pediatrics particularly important and urgently needed, but also challenging. This review summarizes pharmacogenetic studies on the effects of genetic polymorphisms on pharmacokinetic parameters and clinical outcomes in pediatric populations for certain drugs, which are commonly prescribed by clinicians across multiple therapeutic areas in a general hospital, organized from those with the most to the least pediatric evidence among each drug category. We also further discuss the research status of the gene-guided dosing regimens and clinical implementation of pediatric pharmacogenetics. More and more drug-gene interactions are demonstrated to have clinical validity for children, and pharmacogenomics in pediatrics have shown evidence-based benefits to enhance the efficacy and precision of existing drug dosing regimens in several therapeutic areas. However, the most important limitation to the implementation is the lack of high-quality, rigorous pediatric prospective clinical studies, so adequately powered interventional clinical trials that support incorporation of pharmacogenetics into the care of children are still needed.

Assessment of the Implementation of Pharmacogenomic Testing in a Pediatric Tertiary Care Setting

IMPORTANCE

Pharmacogenomic (PGx) testing provides preemptive pharmacotherapeutic guidance regarding the lack of therapeutic benefit or adverse drug reactions of PGx targeted drugs. Pharmacogenomic information is of particular value among children with complex medical conditions who receive multiple medications and are at higher risk of developing adverse drug reactions.

OBJECTIVES

To assess the implementation outcomes of a PGx testing program comprising both a point-of-care model that examined targeted drugs and a preemptive model informed by whole-genome sequencing that evaluated a broad range of drugs for potential therapy among children in a pediatric tertiary care setting.

DESIGN, SETTING, AND PARTICIPANTS

This cohort study was conducted at The Hospital for Sick Children in Toronto, Ontario, from January 2017 to September 2020. Pharmacogenomic analyses were performed among 172 children who were categorized into 2 groups: a point-of-care cohort and a preemptive cohort. The point-of-care cohort comprised 57 patients referred to the consultation clinic for planned therapy with PGx targeted drugs and/or for adverse drug reactions, including lack of therapeutic benefit, after the receipt of current or past medications. The preemptive cohort comprised 115 patients who received exploratory whole-genome sequencing-guided PGx testing for their heart conditions from the cardiac genome clinic at the Ted Rogers Centre for Heart Research.

EXPOSURES

Patients received PGx analysis of whole-genome sequencing data and/or multiplex genotyping of 6 pharmacogenes (CYP2C19, CYP2C9, CYP2D6, CYP3A5, VKORC1, and TPMT) that have established PGx clinical guidelines.

MAIN OUTCOMES AND MEASURES

The number of patients for whom PGx test results warranted deviation from standard dosing regimens.

RESULTS

A total of 172 children (mean [SD] age, 8.5 [5.6] years; 108 boys [62.8%]) were enrolled in the study. In the point-of-care cohort, a median of 2 target genes (range, 1-5 genes) were investigated per individual, with CYP2C19 being the most frequently examined; genotypes in 21 of 57 children (36.8%) were incompatible with standard treatment regimens. As expected from population allelic frequencies, among the 115 children in the whole-genome sequencing-guided preemptive cohort, 92 children (80.0%) were recommended to receive nonstandard treatment regimens for potential drug therapies based on their 6-gene pharmacogenetic profile.

CONCLUSIONS AND RELEVANCE

In this cohort study, among both the point-of-care and preemptive cohorts, the multiplex PGx testing program provided dosing recommendations that deviated from standard regimens at an overall rate that was similar to the population frequencies of relevant variants.

A pediatric perspective on genomics and prevention in the twenty-first century

We present evidence from diverse disciplines and populations to identify the current and emerging role of genomics in prevention from both medical and public health perspectives as well as key challenges and potential untoward consequences of increasing the role of genomics in these endeavors. We begin by comparing screening in healthy populations (newborn screening), with testing in symptomatic populations, which may incidentally identify secondary findings and at-risk relatives. Emerging evidence suggests that variants in genes subject to the reporting of secondary findings are more common than expected in patients who otherwise would not meet the criteria for testing and population testing for variants in these genes may more precisely identify discrete populations to target for various prevention strategies starting in childhood. Conversely, despite its theoretical promise, recent studies attempting to demonstrate benefits of next-generation sequencing for newborn screening have instead demonstrated numerous barriers and pitfalls to this approach. We also examine the special cases of pharmacogenomics and polygenic risk scores as examples of ways genomics can contribute to prevention amongst a broader population than that affected by rare Mendelian disease. We conclude with unresolved questions which will benefit from future investigations of the role of genomics in disease prevention.

Personalized treatment in heart transplantation

PURPOSE OF REVIEW

We are entering the era of personalized medicine, in which pharmacogenomics and biomarker-based assays can be used to tailor diagnostic tests and drug therapies to individual patients. This new approach to patient-specific care offers the potential to maximize the efficacy of available medical treatments while reducing the incidence of adverse side effects. Here, we present approaches to personalize the care of heart transplant recipients.

RECENT FINDINGS

Four strategies for personalized posttransplant care are described, including use of pharmacogenomic data to individualize the use of immunosuppressive drugs, immune monitoring to prevent acute rejection while reducing the long-term consequences of over immunosuppression, noninvasive surveillance for acute rejection, and targeted prophylaxis against opportunistic infections.

SUMMARY

The long-term survival of heart transplant recipients is limited by side effects of immunosuppressive drugs, including infectious complications, renal dysfunction, and malignancy. We discuss strategies to maximize the benefits of immunosuppressive and prophylactic therapies while minimizing their long-term toxicities.

The coming of age of a young subspecialty: paediatric hepatology

Paediatric hepatology dates from the 1970s and it is the youngest of the organ-specific subspecialties. As then there have been impressive achievements in the fields of anatomical, metabolic, immunological and neoplastic diseases, and the advent of modern molecular biology has resulted in a marked increase in exact diagnoses. Liver transplants provided enormous stimulus for the discipline. Due to changing morbidity patterns, the discipline faces new challenges, such as environment- and lifestyle-induced liver diseases, but different forms of chronic viral hepatitis are diminishing.

CONCLUSION

High levels of competence require good clinical research, optimal results and a high degree of centralisation.

Precision monitoring of immunotherapies in solid organ and hematopoietic stem cell transplantation

Pharmacological immunotherapies are a key component of post-transplant therapy in solid-organ and hematopoietic stem cell transplantation. In current clinical practice, immunotherapies largely follow a one-size fits all approach, leaving a large portion of transplant recipients either over- or under-immunosuppressed, and consequently at risk of infections or immune-mediated complications. Our goal here is to review recent and rapid advances in precision and genomic medicine approaches to monitoring of post-transplant immunotherapies. We will discuss recent advances in precision measurements of pharmacological immunosuppression, measurements of the plasma and gut microbiome, strategies to monitor for allograft injury and post-transplant malignancies via circulating cell-free DNA, and comprehensive measurements of the B and T cell immune cell repertoire.