Lymphocyte counts in kidney allograft recipients are associated with IMPDH2 3757T>C gene polymorphism

Influence of genetic polymorphisms on pharmacokinetics and treatment response of mycophenolic acid: a scoping review

This scoping review explores the impact of genetic polymorphisms on the pharmacokinetics and treatment responses of mycophenolic acid (MPA), an immunosuppressant. The study includes 83 articles from 1226 original studies, focusing on transplantation (n = 80) and autoimmune disorders (n = 3). Genetic variants in uridine 5'-diphospho-glucuronosyltransferase (UGT1A9, UGT1A8 and UGT2B7) and transmembrane transporters (ABCC2, SLCO1B1, SLCO1B3 and ABCB1) significantly affected MPA's pharmacokinetics and susceptibility to its adverse effect. Whereas variants in several genes including UGT1A9, UGT2B7, IMPDH1 and IMPDH2 have been associated with a higher risk of transplant rejection. However, there is a lack of studies on MPA's impact on autoimmune disorders and limited research on the Asian population. The findings underscore the need for further research on MPA's impact across different populations and diseases, particularly among other Asian ethnic groups, to advance personalized medicine in MPA therapy.

Burden of neutropenia and leukopenia among adult kidney transplant recipients: A systematic literature review of observational studies

BACKGROUND

Leukopenia and neutropenia (L/N) may affect treatment decisions, potentially resulting in poor clinical and economic outcomes among kidney transplant recipients (KTRs). The burden of L/N is poorly quantified systematically. This systematic literature review aimed to summarize the incidence of, risk factors for, and clinical and economic outcomes associated with L/N post-KT.

METHODS

We systematically searched MEDLINE, Embase, and the Cochrane Library (from database inception-June 14, 2021) and conferences (past 3 years) to identify observational studies examining epidemiology, risk factors, or outcomes associated with L/N among adult KTRs.

RESULTS

Of 2081 records, 82 studies met inclusion criteria. Seventy-three studies reported the epidemiology of L/N post-KT. Pooled incidence of neutropenia, defined as absolute neutrophil counts (ANC) <1000/μl, ranged from 13% to 48% within 1-year post-transplant; ANC <500/μl ranged from 15% to 20%. Leukopenia, defined as white blood cell counts <3500/μl, was 19% to 83%. Eleven studies reported independent risk factors associated with L/N post-KT. D+/R- cytomegalovirus status, mycophenolic acid (MPA), and tacrolimus use were the most consistent risk factors across studies. Fourteen studies reported L/N-associated clinical outcomes. We noted a trend toward a positive association between neutropenia and acute rejection/opportunistic infections. Mixed findings were noted on the association between L/N and graft failure or mortality. Dosage modifications of valganciclovir, MPA, cotrimoxazole, and anti-thymoglobulin and the need for granulocyte colony-stimulating factor (G-CSF) use were common with L/N.

CONCLUSION

Findings suggest post-transplant L/N were common and associated with frequent modifications of immunosuppressive agents, requiring G-CSF use, and rejection or opportunistic infections. Findings highlight the need for interventions to reduce risk of L/N post-KT.

Meta-analysis of the associations of IMPDH and UGT1A9 polymorphisms with rejection in kidney transplant recipients taking mycophenolic acid

PURPOSE

To investigate the associations of IMPDH and UGT1A9 polymorphisms with rejection in kidney transplant recipients taking mycophenolic acid (MPA).

METHODS

PubMed, Web of Science, Embase, Cochrane Library, Wanfang Data, and the China Academic Journal Network Publishing Database were systematically searched for studies investigating the associations of IMPDH1, IMPDH2, and UGT1A9 polymorphisms with rejection in kidney transplant recipients taking MPA. Associations were evaluated by pooled odds ratios (ORs) and effect sizes (ESs) with 95% confidence intervals (CIs).

RESULTS

Twelve studies were included in the analysis, including a total of 2342 kidney transplant recipients. The results showed that compared with the TC + CC variant genotypes, the TT genotype of IMPDH2 3757 T > C was significantly associated with a higher risk of rejection (ES = 1.60, 95% CI = 1.07-2.40, P = 0.021), while there was no significant association of the IMPDH2 3757 T > C polymorphism with acute rejection within 1 year in kidney transplant recipients (OR = 1.49, 95% CI = 0.79-2.80, P = 0.217; ES = 1.44, 95% CI = 0.88-2.36, P = 0.142). The GG genotypes of IMPDH1 125G > A and IMPDH1 106G > A were significantly associated with a higher risk of rejection (ES = 1.91, 95% CI = 1.11-3.28, P = 0.019) and acute rejection within 1 year (ES = 2.12, 95% CI = 1.45-3.10, P < 0.001) than the variant genotypes GA + AA. The TT genotype of UGT1A9 275 T > A showed a decreased risk of rejection compared with the variant genotypes TA + AA (ES = 0.44, 95% CI = 0.23-0.84, P = 0.013).

CONCLUSIONS

IMPDH1, IMPDH2, and UGT1A9 polymorphisms were associated with rejection in kidney transplant recipients, and the genetic backgrounds of patients should be considered when using MPA.

The Impact of Genetic Polymorphisms on the Pharmacokinetics and Pharmacodynamics of Mycophenolic Acid: Systematic Review and Meta-analysis

BACKGROUND

Mycophenolic acid (MPA) is among the most commonly prescribed medications for immunosuppression following organ transplantation. Highly variable MPA exposure and drug response are observed among individuals receiving the same dosage of the drug. Identification of candidate genes whose polymorphisms could be used to predict MPA exposure and clinical outcome is of clinical value.

OBJECTIVES

This study aimed to determine the impact of genetic polymorphisms on the pharmacokinetics and pharmacodynamics of MPA in humans by means of a systematic review and meta-analysis.

METHODS

A systematic search was conducted on PubMed, EMBASE, Web of Sciences, Scopus, and the Cochrane Library databases. A meta-analysis was conducted to determine any associations between genetic polymorphisms and pharmacokinetic or pharmacodynamic parameters of MPA. Pooled-effect estimates were calculated by means of the random-effects model.

RESULTS

A total of 37 studies involving 3844 individuals were included in the meta-analysis. Heterozygous carriers of the UGT1A9 -275T>A polymorphism were observed to have a significantly lower MPA exposure than wild-type individuals. Four single nucleotide polymorphisms (SNPs), namely UGT1A9 -2152C>T, UGT1A8 518C>G, UGT2B7 211G>T, and SLCO1B1 521T>C, were also significantly associated with altered MPA pharmacokinetics. However, none of the investigated SNPs, including SNPs in the IMPDH gene, were found to be associated with the clinical efficacy of MPA. The only SNP that was associated with adverse outcomes was SLCO1B3 344T>G.

CONCLUSIONS

The present systematic review and meta-analysis identified six SNPs that were significantly associated with pharmacokinetic variability or adverse effects of MPA. Our findings represent the basis for future research and clinical implications with regard to the role of pharmacogenetics in MPA pharmacokinetics and drug response.

Personalized Therapy for Mycophenolate: Consensus Report by the International Association of Therapeutic Drug Monitoring and Clinical Toxicology

ABSTRACT

When mycophenolic acid (MPA) was originally marketed for immunosuppressive therapy, fixed doses were recommended by the manufacturer. Awareness of the potential for a more personalized dosing has led to development of methods to estimate MPA area under the curve based on the measurement of drug concentrations in only a few samples. This approach is feasible in the clinical routine and has proven successful in terms of correlation with outcome. However, the search for superior correlates has continued, and numerous studies in search of biomarkers that could better predict the perfect dosage for the individual patient have been published. As it was considered timely for an updated and comprehensive presentation of consensus on the status for personalized treatment with MPA, this report was prepared following an initiative from members of the International Association of Therapeutic Drug Monitoring and Clinical Toxicology (IATDMCT). Topics included are the criteria for analytics, methods to estimate exposure including pharmacometrics, the potential influence of pharmacogenetics, development of biomarkers, and the practical aspects of implementation of target concentration intervention. For selected topics with sufficient evidence, such as the application of limited sampling strategies for MPA area under the curve, graded recommendations on target ranges are presented. To provide a comprehensive review, this report also includes updates on the status of potential biomarkers including those which may be promising but with a low level of evidence. In view of the fact that there are very few new immunosuppressive drugs under development for the transplant field, it is likely that MPA will continue to be prescribed on a large scale in the upcoming years. Discontinuation of therapy due to adverse effects is relatively common, increasing the risk for late rejections, which may contribute to graft loss. Therefore, the continued search for innovative methods to better personalize MPA dosage is warranted.

New challenges and promises in solid organ transplantation pharmacogenetics: the genetic variability of proteins involved in the pharmacodynamics of immunosuppressive drugs

Interindividual variability in immunosuppressive drug responses might be partly explained by genetic variants in proteins involved in the immune response or associated with IS pharmacodynamics. On a general basis, the pharmacogenetics of drug target proteins is less known and understood than that of proteins involved in drug disposition pathways. The aim of this review is to facilitate research related to the pharmacodynamics of the main immunosuppressive drugs used in solid organ transplantation. We elaborated a quality of evidence grading system based on a literature review and identified 'highly recommended', 'recommended' or 'potential' candidates for further research. It is likely that a number of additional rare variants might further explain drug response phenotypes in transplantation, and particularly the most severe ones. The advent of next-generation sequencing will help to identify those variants.

Impact of Genetic Polymorphisms on 6-Thioguanine Nucleotide Levels and Toxicity in Pediatric Patients with IBD Treated with Azathioprine

BACKGROUND

Thiopurine-related toxicity results in discontinuation of therapy in up to 30% of patients with inflammatory bowel disease. Although thiopurine S-methyltransferase (TPMT) is implicated in toxicity, not all toxicity can be attributed to TPMT polymorphisms. We investigated the effects of polymorphisms of genes involved in thiopurine and folate metabolism pathways on 6-thioguanine nucleotide levels and toxicity.

METHODS

Retrospective clinical data and blood samples were collected from 132 pediatric patients with inflammatory bowel disease treated with azathioprine. Eighty-seven genetic polymorphisms of 30 genes were screened using the MassARRAY system, and 70 polymorphisms of 28 genes were selected for further analysis.

RESULTS

TPMT genotype (P < 0.001), concurrent use of mesalazine (P = 0.006), ABCC5 (rs2293001) (P < 0.001), ITPA (rs2236206 and rs8362) (P = 0.010 and P = 0.003), and ABCB1 (rs2032582) (P = 0.028) were all associated with the ratio of 6-thioguanine nucleotides to azathioprine dose. ADK (rs10824095) (P = 0.004, odds ratio [OR] = 6.220), SLC29A1 (rs747199) (P = 0.016, OR = 5.681), and TYMS (rs34743033) (P = 0.045, OR = 3.846) were associated with neutropenia. ABCC1 (rs2074087) (P = 0.022, OR = 3.406), IMPDH1 (rs2278294) (P = 0.027, OR = 0.276), and IMPDH2 (rs11706052) (P = 0.034, OR = 3.639) had a significant impact on lymphopenia.

CONCLUSIONS

This study describes genetic polymorphisms in genes whose products may affect pharmacokinetics and which may predict the relative likelihood of benefit or risk from thiopurine treatment. These findings may serve as a basis for personalized thiopurine therapy in pediatric patients with inflammatory bowel disease, although our data need to be validated in further studies.

Inosine monophosphate dehydrogenase polymorphisms and renal allograft outcome

BACKGROUND

Interindividual variation in inosine monophosphate dehydrogenase (IMPDH) enzyme activity and adverse effects caused by mycophenolate mofetil (MMF) inhibition may be genetically determined, and if so, transplant recipients should receive personalized dosing regimens of MMF, which would maximize efficacy and minimize toxicity. Some studies have demonstrated a relationship between the single nucleotide polymorphism and the risk of acute rejection with IMPDH I variants rs2278293 and rs2278294 and IMPDH II variant rs11706052, whereas others have failed to exhibit an effect. The aim of this work was to investigate the influence of these polymorphisms on acute rejection rates, graft survival and function, and MMF doses in a large cohort of patients.

METHODS

A random sample of 1040 recipients from the Collaborative Transplant Study DNA bank was genotyped for the variants IMPDH I rs2278293 and rs2278294 and IMPDH II rs11706052.

RESULTS

The presence of the T (rs2278293) and G alleles (rs2278294) in the IMPDH I variants and carriage of the G allele (rs11706052) in the IMPDH II variant did not increase the risk of rejection or affect graft function by 1 year after transplantation. There was no association with MMF dose tolerated at 1 year. Furthermore, these polymorphisms did not impact graft or patient survival at 5 years.

CONCLUSION

This study represents the largest cohort of patients with the longest follow-up to date and does not support previous evidence for an association between these IMPDH variants and renal allograft rejection and graft survival.