Toward personalized medicine in renal transplantation

Therapeutic concentration achievement and allograft survival comparing usage of conventional tacrolimus doses and CYP3A5 genotype-guided doses in renal transplantation patients

AIMS

Although cytochromeP450(CYP)3A5 gene polymorphism affects personalized tacrolimus doses, there is no consensus as to whether CYP3A5 genotypes should be determined to adjust the doses. The aims were to compare the therapeutic ranges and clinical outcomes between the conventional and genotype-guided tacrolimus doses.

METHODS

This randomized controlled study compared 63 cases of the conventional tacrolimus dose group (0.1 mg/kg/day) with 62 cases of the genotype-guided doses group of 0.125, 0.1 and 0.08 mg/kg for CYP3A5*1/*1, *1/*3, and *3/*3 genotypes for the initial 3 days of kidney transplantation. After day 3, dose adjustment occurred in both groups to achieve therapeutic concentrations.

RESULTS

The genotype-guided group had an increased proportion of patients with tacrolimus concentrations in the therapeutic range at the steady state on day 3 (40.3 vs 23.8%, P = .048). A lower proportion of over-therapeutic concentration patients was noted in the genotype-guided group in the CYP3A5*3/*3 genotype (9.7 vs 27%, P = .013). Unexpectedly, more delayed graft functions (DGFs) were in the genotype-guided group (41.9 vs 22.2%, P = .018) especially in the CYP3A5*1/*1 participants who might have had an aggravated DGF by a longer ischaemic time and higher serum donor creatinine levels than in the control group. There were no significant differences of glomerular filtration rates or graft or patient survivals over a median 37-month follow-up period.

CONCLUSIONS

Determination of the CYP3A5 genotype improved therapeutic range achievement. CYP3A5*1/*1 patients who have high risks of DGF should be closely monitored because of an increased risk of DGF and reduced glomerular filtration rate with high tacrolimus doses.

Influence of CYP3A5 genetic differences in tacrolimus on quantitative interstitial fibrosis and long-term graft function in kidney transplant recipients

The impact of CYP3A5 polymorphisms on clinical outcomes is controversial. The present study investigated the impact of CYP3A5 genetic differences on the development of interstitial fibrosis (IF) from 0 h to 1 year post-transplantation in biopsy sections from 96 living kidney recipients under the same target trough regimen of tacrolimus. The relationships between CYP3A5 polymorphisms and long-term graft function and death-censored graft survival were also examined. A quantitative analysis of IF was performed using computer-assisted imaging on virtual slides. Percent IF (%IF) in the cortical region at 0 h was defined as the baseline, and increases in the ratio of %IF 1 year post-transplantation were calculated. The relationships between CYP3A5 genetic differences and the development of IF, the incidence of clinical events, and the long-term function and death-censored survival of grafts were assessed. The mean increase in the ratio of %IF from 0 h to 1 year was 1.38 ± 0.74-fold. Despite therapeutic drug monitoring (TDM), trough levels of tacrolimus were lower in carriers with the CYP3A5*1 allele (expressers) than in those with the CTP3A5*3/*3 genotype (non-expressers) throughout the 1-year post-transplantation period. However, CYP3A5 genetic differences were not associated with the development of IF, any clinical events, or the long-term function and survival of grafts. The clinical impact of CYP3A5 genetic differences may be small under the current immunosuppressive regimen consisting of mycophenolate mofetil, steroids, basiliximab, and lower target trough levels of tacrolimus with suitable TDM in a low immunological risk population.

Changing Paradigms in the Management of Rejection in Kidney Transplantation: Evolving From Protocol-Based Care to the Era of P4 Medicine

PURPOSE OF REVIEW

P4 medicine denotes an evolving field of medicine encompassing predictive, preventive, personalized, and participatory medicine. Using the example of kidney allograft rejection because of donor-recipient incompatibility in human leukocyte antigens, this review outlines P4 medicine's relevance to the various stages of the kidney transplant cycle.

SOURCES OF INFORMATION

A search for English articles was conducted in Medline via OvidSP (up to August 18, 2016) using a combination of subject headings (MeSH) and free text in titles, abstracts, and author keywords for the concepts kidney transplantation and P4 medicine. The electronic database search was expanded further on particular subject headings.

FINDINGS

Available histocompatibility methods exemplify current applications of the predictive and preventive domains of P4 medicine in kidney transplant recipients' care. Pharmacogenomics are discussed as means to facilitate personalized immunosuppression regimens and promotion of active patient participation as a means to improve adherence.

LIMITATIONS

For simplicity, this review focuses on rejection. P4 medicine, however, should more broadly address health concerns in kidney transplant recipients, including competing outcomes such as infections, malignancies, and cardiovascular disease. This review highlights how biomarkers to evaluate these competing outcomes warrant validation and standardization prior to their incorporation into clinical practice.

IMPLICATIONS

Consideration of all 4 domains of the P4 medicine framework when caring for and/or studying kidney transplant recipients has the potential of increasing therapeutic efficiency, minimizing adverse effects, decreasing health care costs, and maximizing wellness. Technologies to gauge immune competency, immunosuppression requirements, and early/reversible immune-mediated injuries are required to optimize kidney transplant care.

Biomarkers and personalized therapy in chronic kidney diseases

Numerous clinical trials are currently evaluating new strategies to halt the progression of renal damage in patients with chronic kidney diseases (CKDs). Unfortunately, none of them have considered that the lack of response to new therapies may be due to the pharmacogenetics/pharmacogenomics profile of the patient. The recent impact of high-throughput technologies used in genomics, proteomics and metabolomics may open a new way for discovering biomarkers that can provide us information about the mechanisms on the progression of renal damage. However, they can also be used for diagnosis and for selecting drugs, leading to personalized tailored therapy. The uses of classifiers formed by a list of genes, proteins and metabolites have been introduced into oncology and organ transplantation. These new approaches have recently also been used in the care of human glomerulonephritis. Integrating the large omic data sets with drug and disease databases could give the prediction of drug efficacy and side effects in CKDs.

Recent advances in biomarker discovery in solid organ transplant by proteomics

The identification and clinical use of more sensitive and specific biomarkers in the field of solid organ transplantation is an urgent need in medicine. Solid organ transplantation has seen improvements in the short-term survival of transplanted organs due to recent advancements in immunosuppressive therapy. However, the currently available methods of allograft monitoring are not optimal. Recent advancements in assaying methods for biomolecules such as genes, mRNA and proteins have helped to identify surrogate biomarkers that can be used to monitor the transplanted organ. These high-throughput 'omic' methods can help researchers to significantly speed up the identification and the validation steps, which are crucial factors for biomarker discovery efforts. Still, the progress towards identifying more sensitive and specific biomarkers remains a great deal slower than expected. In this article, we have evaluated the current status of biomarker discovery using proteomics tools in different solid organ transplants in recent years. This article summarizes recent reports and current status, along with the hurdles in efficient biomarker discovery of protein biomarkers using proteomics approaches. Finally, we will touch upon personalized medicine as a future direction for better management of transplanted organs, and provide what we think could be a recipe for success in this field.

Profiling the proteome in renal transplantation

Improved monitoring of transplanted solid organs is one of the next crucial steps leading to an increase in both patient and allograft survival. This can be facilitated through one or a set of surrogate biomarker molecules that accurately and precisely indicate the health status of the transplanted organ. Recent developments in the field of high throughput "omic" methods including genomics and proteomics have facilitated robust and comprehensive analysis of genes and proteins. This development has stimulated efforts in the identification of effective and clinically applicable gene and protein biomarkers in solid organ transplantation, including kidney transplantation. Some achievements have been made through proteomics in terms of profiling proteins and identification of potential biomarkers. However, the road to a successful biomarker discovery and its clinical implementation has proved to be challenging, requiring a number of key issues to be addressed. Such issues are: the lack of widely accepted protocols, difficulty in sample processing and transportation and a lack of collaborative efforts to achieve significant sample sizes in clinical studies. In this review using our area of expertise, we describe the current strategies used for proteomic-based biomarker discovery in renal transplantation, discuss inherent issues associated with these efforts and propose better strategies for successful biomarker discovery.