Cyclosporine and low-dose ketoconazole in renal transplant recipients: a single-center experience

Pharmacokinetic Boosting of Calcineurin Inhibitors in Transplantation: Pros, Cons, and Perspectives

ABSTRACT

The concept of pharmacokinetic (PK) boosting of calcineurin inhibitors (CNI) emerged after the FDA approval of cyclosporine-A. Several studies followed, and the proof of concept was well established by the late 1990s. This also continued for the next blockbuster immunosuppressant, tacrolimus. The driver for such research was an endeavor to save costs, as both drugs were expensive due to patent protection. Two CYP inhibitors, ketoconazole and diltiazem, have been extensively studied in this context and continue to be prescribed off-label along with the CNI. It has been observed that using ketoconazole reduces the dose requirement of tacrolimus by about 50% and 30% with diltiazem, which is in conformity with their pharmacological actions. Off-label co-prescription of these drugs with CNI is often encountered in low and middle-income countries. The foremost reason cited is economic. This article collates the evidence from the clinical studies that evaluate the PK-boosting effects of CNI and also reviews the gaps in the current evidence base. The current knowledge prevents the transplant community from making meaningful inferences about the risks and benefits of such strategies. Although the PK-boosting strategy can lead to serious adverse events, emerging evidence suggests that it may be advantageous for individuals with high CNI dose requirements. Hence, PK boosting may be an unmet need in the therapeutics of CNI. Nevertheless, there are several unanswered questions surrounding such use, and therefore, this merits testing in well-designed clinical studies. Moreover, drugs with better safer profiles and a history of successful PK boosting may be considered for evaluation with CNI.

CYP51 as drug targets for fungi and protozoan parasites: past, present and future

The efficiency of treatment of human infections with the unicellular eukaryotic pathogens such as fungi and protozoa remains deeply unsatisfactory. For example, the mortality rates from nosocomial fungemia in critically ill, immunosuppressed or post-cancer patients often exceed 50%. A set of six systemic clinical azoles [sterol 14α-demethylase (CYP51) inhibitors] represents the first-line antifungal treatment. All these drugs were discovered empirically, by monitoring their effects on fungal cell growth, though it had been proven that they kill fungal cells by blocking the biosynthesis of ergosterol in fungi at the stage of 14α-demethylation of the sterol nucleus. This review briefs the history of antifungal azoles, outlines the situation with the current clinical azole-based drugs, describes the attempts of their repurposing for treatment of human infections with the protozoan parasites that, similar to fungi, also produce endogenous sterols, and discusses the most recently acquired knowledge on the CYP51 structure/function and inhibition. It is our belief that this information should be helpful in shifting from the traditional phenotypic screening to the actual target-driven drug discovery paradigm, which will rationalize and substantially accelerate the development of new, more efficient and pathogen-oriented CYP51 inhibitors.

Combining cytochrome P-450 3A4 modulators and cyclosporine or everolimus in transplantation is successful

AIM: To describe the long term follow-up of kidney allograft recipients receiving ketoconazole with calcineurin inhibitors (CNI) alone or combined with everolimus.

METHODS: This is an open-label, prospective observational clinical trial in low immunologic risk patients who, after signing an Institutional Review Board approved consent form, were included in one of two groups. The first one (n = 59) received everolimus (target blood level, 3-8 ng/mL) and the other (n = 114) azathioprine 2 mg/kg per day or mycophenolate mofetyl (MMF) 2 g/d. Both groups also received tapering steroids, the cytochrome P-450 3A4 (CYP3A4) modulator, ketoconazole 50-100 mg/d, and cyclosporine with C0 targets in the everolimus group of 200-250 ng/mL in 1 mo, 100-125 ng/mL in 2 mo, and 50-65 ng/mL thereafter, and in the azathioprine or MMF group of 250-300 ng/mL in 1 mo, 200-250 ng/mL in 2 mo, 180-200 ng/mL until 3-6 mo, and 100-125 ng/mL thereafter. Clinical visits were performed monthly the first year and quarterly thereafter by treating physicians and all data was extracted by the investigators.

RESULTS: The clinical characteristics of these two cohorts were similar. During the follow up (66 + 31 mo), both groups showed comparable clinical courses, but the biopsy proven acute rejection rate during the full follow-up period seemed to be lower in the everolimus group (20% vs 36%; P = 0.04). The everolimus group did not show a higher surgical complication rate than the other group. By the end of the follow-up period, the everolimus group tended to show a higher glomerular filtration rate. Nevertheless, we found no evidence of a consistent negative slope of the temporal allograft function estimated by the modification of the diet in renal disease formula in any of both groups. At 6 years of follow-up, the uncensored and death-censored graft survivals were 91% and 93%, and 91% and 83% in the everolimus plus cyclosporine, and cyclosporine alone groups, respectively. The addition of ketoconazole saved 80% of cyclosporine and 56% of everolimus doses.

CONCLUSION: Combining CYP3A4 modulators with CNI or mammalian target of rapamycin inhibitor, in low immunological risk kidney transplant recipients is feasible, effective, safe and affordable even in the long term.

The clinical value of enzyme-multiplied immunoassay technique monitoring the plasma concentrations of cyclosporine A after renal transplantation

The feasibility and the clinical value of the enzyme-multiplied immunoassay technique (EMIT) monitoring of blood concentrations of cyclosporine A (CsA) in patients treated with CsA were investigated after kidney transplantation. The validation method was performed to the EMIT determination of CsA blood concentration, the CsA whole blood ‘trough concentrations (C₀) of patients in different time periods after renal transplantation were monitored, and combined with the clinical complications, the statistical results were analyzed and compared. EMIT was precise, accurate and stable, also with a high quality control. The mean postoperative blood concentration of CsA was as follows: <1 month, (281.4 ± 57.9)ng/mL; 2 – 3 months, (264.5 ± 41. 2)ng/mL; 4 – 5 months, (236.4 ± 38. 9)ng/mL; 6 – 12 months, (206.5 ± 32.6)ng/mL; >12 months, (185.6 ± 28.1)ng/mL. The toxic reaction rate of CsA blood concentration within the recommended therapeutic concentration was 14. 1%, significantly lower than that of the none-recommended dose group (37.2%) (P < 0.05); the transplantation rejection rate was 4.4%, significantly lower than that of the none-recommended dose group (22.5%) (P < 0.05). Using EMIT to monitor the blood concentration of CsA as the routine laboratory method is feasible, and is able to reduce the CsA toxicity and rejection significantly, leading to achieving the desired therapeutic effect.

KDIGO clinical practice guideline for the care of kidney transplant recipients

The 2009 Kidney Disease: Improving Global Outcomes (KDIGO) clinical practice guideline on the monitoring, management, and treatment of kidney transplant recipients is intended to assist the practitioner caring for adults and children after kidney transplantation. The guideline development process followed an evidence-based approach, and management recommendations are based on systematic reviews of relevant treatment trials. Critical appraisal of the quality of the evidence and the strength of recommendations followed the Grades of Recommendation Assessment, Development, and Evaluation (GRADE) approach. The guideline makes recommendations for immunosuppression, graft monitoring, as well as prevention and treatment of infection, cardiovascular disease, malignancy, and other complications that are common in kidney transplant recipients, including hematological and bone disorders. Limitations of the evidence, especially on the lack of definitive clinical outcome trials, are discussed and suggestions are provided for future research.

CYP3A5*1/*3 genotype influences the blood concentration of tacrolimus in response to metabolic inhibition by ketoconazole

OBJECTIVES

Ketoconazole retards metabolic degradation of tacrolimus through its effect on the cytochrome P-450 enzyme system and allows reduction in treatment costs. Enzyme activity is determined by a single nucleotide polymorphism (*1/*3) in the CYP3A5 gene.

METHODS

We prospectively investigated the impact of this polymorphism on tacrolimus concentration in a cohort of 79 renal transplant recipients on ketoconazole. Genotyping was carried out by using polymerase chain reaction-restriction fragment length polymorphism technique. Dose-adjusted trough level (C0) was calculated at baseline and at 3, 7, 15, 30, and 60 days.

RESULTS

The baseline C0 was significantly lower in those with at least one *1 allele [44.95+/-14.12 vs. 63.43+/-14.72 (ng/ml)/(mg/kg/day), P<0.0001]. After starting ketoconazole in all genotypes, dose-normalized C0 increased and the cost of therapy decreased. Compared with baseline, the magnitude of increase was 112% and 79% in those without and with *1 allele, respectively (P<0.001). The cost savings were 32% and 39% in mycophenolate mofetil-treated and 47% and 61% in azathioprine-treated patients who were with and without one *1 allele, respectively.

CONCLUSION

We show that the CYP3A5*1/*3 polymorphism is an important determinant of the response to inhibition of tacrolimus metabolism by ketoconazole, with a 30% greater inhibition in those lacking *1 allele. This finding will allow better dose adjustment and minimize exposure to subtherapeutic or toxic concentrations.