Therapeutic monitoring of immunosuppressive drugs in pediatric patients: special considerations

Vitamin K2 immunosuppressive effect on pediatric patients with atopic dermatitis

BACKGROUND

Over 20 kinds of steroids, tacrolimus ointments, and cyclosporine capsules are usually recommended for the treatment of atopic dermatitis (AD), depending on the symptoms of patients. However, several side effects sometimes occur with the extensive use of these agents for the treatment of pediatric AD patients. The purpose of this study was to explore whether vitamin K₂ could be a new immunosuppressive candidate for pediatric patients with AD.

METHODS

The immunosuppressive efficacy of vitamin K₂ was evaluated through a cell-culture procedure using mitogen-activated peripheral blood mononuclear cells (PBMCs) obtained from pediatric AD patients.

RESULTS

The mean (SD) IC₅₀ value of vitamin K₂ for the proliferation of concanavalin A-activated PBMCs was 15.37 (30.05) μmol/L, while the value for tacrolimus was 0.10 (0.28) ng/mL (0.12 (0.35) nmol/L). There was a significant correlation between the IC₅₀ values for vitamin K₂ and those for tacrolimus (P = 0.0001, r = 0.8871). However, there was no significant correlation between the IC₅₀ values of vitamin K₂ and those of cyclosporine A or methylprednisolone. A significant correlation between the IC₅₀ values of vitamin K₂ or tacrolimus and blood eosinophil counts (P = 0.0099, r = 0.7086 and P = 0.0032, r = 0.7722, respectively) was observed.

CONCLUSION

Vitamin K₂ -inhibited T-cell mitogen stimulated proliferation of PBMCs from pediatric AD patients in a dose-dependent manner. The PBMCs from pediatric AD patients were more sensitive to the immunosuppressive efficacy of vitamin K₂ than the PBMCs from healthy subjects. The individual immunosuppressive pharmacological efficacy of vitamin K₂ and of tacrolimus could be inferred from the blood eosinophil count of pediatric AD patients.

Identification of Factors Affecting Tacrolimus Trough Levels in Latin American Pediatric Liver Transplant Patients

Tacrolimus is the cornerstone in pediatric liver transplant immunosuppression. Despite close monitoring, fluctuations in tacrolimus blood levels affect safety and efficacy of immunosuppressive treatments. Identifying the factors related to the variability in tacrolimus exposure may be helpful in tailoring the dose. The aim of the present study was to characterize the clinical, pharmacological, and genetic variables associated with systemic tacrolimus exposure in pediatric liver transplant patients. De novo transplant patients with a survival of more than 1 month were considered for inclusion and were genotyped for cytochrome P450 3A5 (CYP3A5). Peritransplant clinical factors and laboratory covariates were recorded retrospectively between 1 month and 2 years after transplant, including alanine aminotransferase (ALT), aspartate aminotransferase, hematocrit, and tacrolimus predose steady-state blood concentrations collected 12 hours after tacrolimus dosing. A linear mixed effect (LME) model was used to assess the association of these factors and the log-transformed tacrolimus dose-normalized trough concentration (logC0/D) levels. Bootstrapping was used to internally validate the final model. External validation was performed in an independent group of patients who matched the original population. The developed LME model described that logC0/D increases with increases in time after transplant (β = 0.019, 95% confidence interval [CI], 0.010-0.028) and ALT values (β = 0.00030, 95% CI, 0.00002-0.00056), whereas logC0/D is significantly lower in graft CYP3A5 expressers compared with nonexpressers (β = -0.349, 95% CI, -0.631 to -0.062). In conclusion, donor CYP3A5 genotype, time after transplant, and ALT values are associated with tacrolimus disposition between 1 month and 2 years after transplant. A better understanding of tacrolimus exposure is essential to minimize the occurrence of an out-of-range therapeutic window that may lead to adverse drug reactions or acute rejection.

Survival Time to Biopsy-Proven Acute Rejection and Tacrolimus Adverse Drug Reactions in Pediatric Liver Transplantation

BACKGROUND

Despite advances in surgical procedures and the optimization of immunosuppressive therapies in pediatric liver transplantation, acute rejection (AR) and serious adverse drug reaction (ADR) to tacrolimus still contribute to morbidity and mortality. Identifying risk factors of safety and efficacy parameters may help in optimizing individual immunosuppressive therapies. This study aimed to identify peritransplant predictors of AR and factors related to the risk of ADR to tacrolimus in a large Latin American cohort of pediatric liver transplant patients.

METHODS

We performed a retrospective cohort study in a pediatric liver transplant population (n = 72). Peritransplant variables were collected retrospectively including demographic, clinical, laboratory parameters, genomic (CYP3A5 donor and recipients polymorphism), and tacrolimus trough concentrations (C0) over a 2-year follow-up period. Variability in tacrolimus C0 was calculated using percent coefficient of variation and tortuosity. ADR- and AR-free survival rates were calculated using the Kaplan-Meier method, and risk factors were identified by multivariate Cox regression models.

RESULTS

Cox-proportional hazard models identified that high tortuosity in tacrolimus C0 was associated with an 80% increased risk of AR [hazard ratio (HR), 1.80; 95% confidence interval (CI), 1.01-3.22; P < 0.05], whereas steroid in maintenance doses decreased this risk (HR, 0.56; 95% CI, 0.31-0.99; P < 0.05). Forty-six patients experienced at least one ADR including hypomagnesemia, nephrotoxicity, hypertension, malignancies, and tremor as a first event. Multivariate analysis showed that C0 values 10 days before the event (HR, 1.25; 95% CI, 1.21-1.39; P < 0.0001) and CYP3A5 expresser recipients (HR, 2.05; 95% CI, 1.03-4.06; P < 0.05) were independent predictors of ADR.

CONCLUSIONS

Tacrolimus C0 values, its variability, and CYP3A5 polymorphisms were identified as risk factors of AR and tacrolimus ADR. This knowledge may help to control and reduce their incidence in pediatric liver transplant patients. Prospective studies are important to validate these results.