The influence of recipient SLCO1B1 rs2291075 polymorphism on tacrolimus dose-corrected trough concentration in the early period after liver transplantation

GENETIC PREDICTORS OF TOXIC EFFECTS OF METHOTREXATE IN CANCER PATIENTS

Today, methotrexate (MTX) is used in combination with other medicines to treat a wide range of malignancies. Despite its proven high efficacy, MTX often causes serious side effects, which may result in the need to reduce the dose of MTX or discontinue the drug altogether. This, in turn, can provoke the development of MTX resistance and cancer progression. Predicting the risk of MTX-induced toxicity is currently difficult due to the variability of pharmacokinetics and pharmacodynamics in different patients, so the scientific literature is intensively searching for potential biomarkers. Based on the data available in the current literature, we analyzed the relationship between variants in the genes encoding the key components of MTX intracellular metabolism and the MTX-induced side effects and drug response. According to the results of our work, the most studied variants are those of the SLC19A1 gene, which encodes the reduced folate carrier protein 1, and the MTHFR gene, which encodes the enzyme methylenetetrahydrofolate reductase. Studies of the effect of methylation of the promoter regions of genes on the therapeutic effect of MTX are also very promising. In conclusion, the study of molecular genetic markers of MTX toxicity is extremely relevant and necessary because it can help to avoid the effect of multidrug resistance and improve the quality of life and survival of patients.

Are Genetic Modifiers the Answer to Different Responses to Hydroxyurea Treatment?-A Pharmacogenetic Study in Sickle Cell Anemia Angolan Children

Sickle cell anemia (SCA) is an inherited disease affecting the hemoglobin that is particularly common in sub-Saharan Africa. Although monogenic, phenotypes are markedly heterogeneous in terms of severity and life span. Hydroxyurea is still the most common treatment for these patients, and the response to treatment is highly variable and seems to be an inherited trait. Therefore, identifying the variants that might predict hydroxyurea response is important for identifying patients who will have a poorer or non-response to treatment, and the ones that are more prone to suffer from severe side effects. In the present pharmacogenetic study, we analyzed the exons of 77 genes described in the literature as potentially associated with hydroxyurea metabolism in Angolan children treated with hydroxyurea and evaluated the drug response considering fetal hemoglobin levels, other hematological and biochemical parameters, hemolysis, number of vaso-occlusive crises and hospitalizations. Thirty variants were identified in 18 of those genes as possibly associated with drug response, five of them in gene DCHS2. Other polymorphisms in this gene were also associated with hematological, biochemical and clinical parameters. Further research examining the maximum tolerated dose and fixed dose with a larger sample size is necessary to corroborate these findings.

Impact of genetic polymorphisms on tacrolimus trough blood concentration in Chinese liver transplant recipients

Purpose: The aim of this study was to analyze the effects of various genetic polymorphisms and clinical factors on tacrolimus (TAC) concentration in the convalescence period (CP) and stabilization period (SP) post-liver transplantation. Patients & methods: A total of 13 SNPs were genotyped in 97 Chinese liver transplant recipients. Associations between SNPs and TAC trough blood concentration/dose ratio (C₀/D) were analyzed using different genetic models in both CP and SP. Results: Only five SNPs were significantly associated with TAC log (C₀/D) in the CP, and none showed a significant association in the SP. We identified rs15524 (CYP3A5), rs9200 (C6), albumin and creatinine as independent predictors of TAC C₀/D in the CP. Furthermore, a final model in the CP explained a total of 30.5% TAC variation. Conclusion: Our study results suggest that in the early stages post-transplantation surgery, recipients' genetic and clinical factors exert a short-term impact on TAC metabolism that gradually decreases with time.

Genotype-guided model significantly improves accuracy of tacrolimus initial dosing after liver transplantation

BACKGROUND

The initial dose of tacrolimus after liver transplantation (LT) is critical for rapidly achieving the steady state of the drug concentration, minimizing the potential adverse reactions and warranting long-term patient prognosis. We aimed to develop and validate a genotype-guided model for determining personalized initial dose of tacrolimus.

METHODS

By combining pharmacokinetic modeling, pharmacogenomic analysis and multiple statistical methods, we developed a genotype-guided model to predict individualized tacrolimus initial dose after LT in the discovery (n = 150) and validation cohorts (n = 97) respectively. This model was further validated in a prospective, randomized and single-blind clinical trial from August, 2021 to February, 2022 (n = 40, ChiCTR2100050288).

FINDINGS

Our model included donor's and recipient's genotypes, recipient's weight and total bilirubin, which achieved an area under the curve of receiver operating characteristic curve (AUC of ROC) of 0.88 and 0.79 in the discovery and validation cohorts, respectively. We found that patients who were given tacrolimus within the recommended concentration range (RCR) (4-10 ng/mL), the new-onset metabolic syndromes are lower, especially for new-onset diabetes (p = 0.043). In the clinical trial, compared to those in experience-based (EB) group, patients in the model-based (MB) group were more likely to achieving the RCR (75% vs 40%, p = 0.025) with a more variable individualized dose (0.023-0.096 mg/kg/day vs 0.045-0.057 mg/kg/day). Moreover, significantly fewer medication adjustments were required for the MB group than the EB group (2.75 ± 2.01 vs 6.05 ± 3.35, p = 0.001).

INTERPRETATION

Our genotype-based model significantly improved the initial dosing accuracy of tacrolimus and reduced the number of medication adjustments, which are critical for improving the prognosis of LT patients.

FUNDING

National Natural Science Foundation of China, Shanghai three-year action plan, National Science and Technology Major Project of China.

The Effect of Voriconazole on Tacrolimus in Kidney Transplantation Recipients: A Real-World Study

Tacrolimus is an immunosuppressant with a narrow therapeutic window. Tacrolimus exposure increased significantly during voriconazole co-therapy. The magnitude of this interaction is highly variable, but it is hard to predict quantitatively. We conducted a study on 91 kidney transplantation recipients with voriconazole co-therapy. Furthermore, 1701 tacrolimus concentration data were collected. Standard concentration adjusted by tacrolimus daily dose (C/D) and weight-adjusted standard concentration (CDW) increased to 6 times higher during voriconazole co-therapy. C/D and CDW increased with voriconazole concentration. Patients with the genotype of CYP3A5 *3/*3 and CYP2C19 *2/*2 or *2/*3 were more variable at the same voriconazole concentration level. The final prediction model could explain 54.27% of the variation in C/D and 51.11% of the variation in CDW. In conclusion, voriconazole was the main factor causing C/D and CDW variation, and the effect intensity should be quantitative by its concentration. Kidney transplant recipients with CYP3A5 genotype of *3/*3 and CYP2C19 genotype of *2/*2 and *2/*3 should be given more attention during voriconazole co-therapy. The prediction model established in this study may help to reduce the occurrence of rejection.

Rapid clearance of tacrolimus blood concentration triggered by variant pharmacogenes

WHAT IS KNOWN AND OBJECTIVE

Tacrolimus (TAC) is an immunosuppressant with large interpatient pharmacokinetic variability and a narrow therapeutic index. We report a case of acute cellular rejection (ACR) type IB with insufficient TAC blood concentrations (TAC C₀ ).

CASE SUMMARY

ACR developed on the eighth postoperative day of kidney transplantation. During this period, TAC C₀ were insufficient. This referred pharmacogenetic assessment disclosed the patient as a CYP3A5 expresser and CYP3A4*1B carrier. According to the genotype, higher doses of TAC, 15 mg twice daily, were administered and targeted TAC C₀ were achieved.

WHAT IS NEW AND CONCLUSION

Our case presents an association of TAC rapid clearance and two alleles modifying greater CYP3A enzyme activity.