Prediction of cyclosporine area under the curve using a three-point sampling strategy after Neoral administration

Eight-year follow-up in pediatric living donor kidney recipients receiving alemtuzumab induction

Recipient lymphocytes are crucial for direct and indirect pathways of allorecognition. We proposed that the administration of alemtuzumab several weeks pretransplantation could eradicate peripheral lymphatic cells and promote donor-specific acceptance. This was a single-center, retrospective review of 101 consecutive living donor kidney transplantations in pediatric patients (age 7 months-18 years), performed between September 2006 and April 2010. IS protocol included two 30 mg doses of alemtuzumab: The first was given 12-29 days prior to transplantation, and the second at the time of transplantation. Maintenance IS was based on combination of low-dose CNI and mycophenolate, with steroids tapered over the first 5 days post-transplantation. Patients were followed for 7.8±1.3 years, and protocol biopsies were taken 1 month, 1, 3, and 5 years post-transplant. The Kaplan-Meier 8-year patient and graft survival rates in the cyclosporine-treated patients were 82.0±7.3% and 71.6±7.3, and in the tacrolimus-treated patients were 97.2±5.4 and 83.8±6.0%. Biopsy-proven acute rejection developed in 35% of cyclosporine-treated patients and in 8% of tacrolimus-treated patients. Alemtuzumab pretreatment prior to LRD kidney transplantation, followed by maintenance immunosuppression with tacrolimus and MMF, is associated with reasonable long-term results in pediatric patients.

Cyclosporine use in hematopoietic stem cell transplantation: pharmacokinetic approach

Cyclosporine is one of the most vital agents in the process of successful allogeneic hematopoietic stem cell transplantation. Despite a long history and worldwide extent of cyclosporine use for prevention of graft versus host disease, currently there are lots of uncertainties about its optimal method of application to reach the best clinical outcome. A major portion of this problem stems from complicated cyclosporine pharmacokinetics. Study of cyclosporine pharmacokinetic behavior can significantly help recognition of its effectiveness and consequently, optimization of dosing, administration, monitoring and management of adverse effects. In this review, highly accredited but sparse scientific data are gathered in order to provide a better insight for preparation of practice guidelines and directing future studies for allogeneic hematopoietic cell recipients.

Alemtuzumab induction in pediatric kidney transplantation

Recipient parenchymal lymphatic cells are crucial for direct and indirect pathways of allorecognition. We proposed that alemtuzumab, being infused several weeks pretransplant could eradicate peripheral lymphatic cells and promote donor-specific tolerance. We present here a single center, retrospective review of 101 consecutive living-donor kidney transplantations to pediatric patients aged from seven month to 18 yr, performed between September 2006 and April 2010. Immunosupression protocol included two 30 mg doses of alemtuzumab: first given 12-29 d prior to transplantation and second at the time of transplantation. Maintenance immunosupression was based on combination of low dose and wide range CNI and mycophenolate. Patients were followed for 3.8 ± 1.4 yr and protocol biopsies were taken one month, one, and three yr post transplant. The Kaplan-Meier graft and patient survival was 96% and 97% for one yr, 89% and 93% for three yr. Biopsy proven acute rejection developed in 26% patients at one yr and in 35% at two yr, no rejections occurred beyond two yr. We conclude that alemtuzumab pretreatment prior to living related donor kidney transplantation allows to reach satisfactory middle-term results in pediatric patients with wide range and low CNI concentrations.

Prevalence and subtypes of BK virus in pediatric renal transplant recipients in Russia

BKV reactivation is associated with impaired graft function in kidney transplant patients. The objective of our study was to determine the prevalence of BKV infection in consecutive pediatric kidney transplant recipients at our center. Fifty-eight pediatric kidney transplant recipients were studied. The mean age at screening was 9.4 ± 2.8 yr, and samples were obtained at a median of 2.4 ± 1.4 yr after transplantation. BKV-DNA was analyzed in urine and plasma by quantitative PCR. Occurrences of BK-DNAuria and BK-DNAemia did not change in the first two yr after transplantation in children and amounted to 21-23% and 7-8%, respectively (p > 0.05). In the third year, the occurrences of BK-DNAuria and BK-DNAemia increased insignificantly to 27% and 9% in the pediatric patients. We also determined the subtypes and subgroups of BK virus isolated from Russian renal transplant recipients and found that BKV isolates were composed of subtypes Ib-2 and IV/c2. The data we obtained indicate that although only 5% of BKVAN cases occurred between years two and five post-transplantation, it seems necessary to regularly monitor pediatric patients for BKV infection through the third year after transplantation.

Validation of sparse sampling strategies to estimate cyclosporine A area under the concentration-time curve using either a specific radioimmunoassay or high-performance liquid chromatography method

INTRODUCTION

Area under the concentration-time curve (AUC) has been advocated as a better parameter to monitor cyclosporine A than trough concentrations. Up to now, more than 100 equations to estimate AUC using a limited sampling strategy have been published, but not all have been validated.

MATERIAL AND METHODS

Eight equations for AUC0-12h and two for AUC0-8h were validated. Concentrations of cyclosporine A were analyzed by high-performance liquid chromatography (HPLC) and a specific radioimmunoassay (RIA) method. Forty male renal transplant patients were included in the study. Blood samples were taken predose and at 0.5, 1, 1.5, 2, 3, 5, 8, and 12 hours after the morning dose when the patient was in steady state. The percentage prediction error (%pe) was used for an assessment of the performance of the equations. Mean %pe less than ± 15% and absolute %pe less than 30% in 95% of predictions were considered to be acceptable. Other possibilities such as %pe less than 25%, 20%, and 15% were also tested.

RESULTS

Eight equations for AUC0-12h met the requirements using both assays, six in the HPLC set only and four in the RIA set only. The highest precision was obtained with AUC0-12h = 123.792 + 1.165*C1h + 3.021*C3h + 7.33*C8h proposed by de Mattos et al. The mean %pe was 1% ± 8% (-16 to 19) for HPLC (values given as mean ± standard deviation [range]) and -1 ± 5 (-17 to 10) for RIA. Mean absolute %pe was 7 ± 5 (0.0 to 19) for HPLC and 4 ± 4 (0.0 to 17) for RIA. For clinical use, the most suitable equation was AUC0-12h = 363.078 + 8.77*C1h + 3.07*C3h proposed by Wacke et al, which produced the second lowest %pe and used two sampling points in the period of 1 to 3 hours after dose. The mean %pe was -7 ± 10 (-25 to 25) for HPLC and 2.3 ± 6 (-10 to 17) for RIA. Mean absolute %pe was 10 ± 7 (0.4 to 25) for HPLC and 5 ± 4 (0.0 to 17) for RIA. The equation: AUC0-8h = 55.37 + 2.89*C0h + 1.08*C1h0.9*C2h + 2.23*C3h proposed by Foradori et al met the criteria with 95% of prediction with absolute %pe less than 15% in the HPLC set and 10% in the RIA set.

CONCLUSION

The validation of equations is of major importance for prediction precision, whereas the analytical method for limited sampling strategy proposals had no influence. Because of the wide interassay variability, it is also important to know which analytical method was used for AUC calculation when interpreting the results.

Cyclosporine Formulation and Kaposi’s Sarcoma after Renal Transplantation

BACKGROUND

Transplantation enhances the risk of malignancies, due to the chronic use of antirejection medication. In the case of Kaposi's sarcoma (KS) the permissive effect of immunosuppression has been extensively studied, and cyclosporine (CsA) appears to play a key role. Here we have compared the incidence of KS in transplant patients receiving Neoral or Sandimmune as a part of their immunosuppressive therapy.

METHODS

In all, 668 kidney transplant recipient followed at our Nephrology Unit from 1970 to 2003 entered this retrospective analysis; 300 were on CsA Sandimmune-based and 308 on CsA Neoral-based therapy. The primary endpoint was the occurrence of KS.

RESULTS

KS was diagnosed in 20 out of 608 patients given CsA with an incidence rate of 4.7 per 1000 patients per year. No episodes of KS was found in the preCsA era. Among patients on CsA, those treated with Neoral had fourfold higher incidence rate of KS than in the Sandimmune group (10.7 vs. 2.3 per 1000 patients per year). Kaplan-Meier analysis shows that patients on Neoral had lower cumulative KS-free probability than those on Sandimmune. Cox's analysis documented that Neoral was a positive predictor of KS development as compared to Sandimmune (hazard ratio: 2.237). Among patients on Neoral, those who developed KS had higher daily exposure to the drug assessed by pharmacokinetic studies.

CONCLUSIONS

In recipients of kidney transplant CsA Neoral increases the risk of KS as compared to the Sandimmune formulation, possibly due to enhanced drug bioavailability and ultimately patients daily CsA exposure.

Comparison of different cyclosporine immunoassays to monitor C0 and C2 blood levels from kidney transplant recipients: Not simply overestimation

BACKGROUND

Immunoassays used for the measurement of cyclosporine (CsA) usually show cross-reactivity for CsA metabolites, usually resulting in unacceptable bias.

METHODS

To assess the performance of different immunoassays, CsA concentrations were analyzed in 132 samples using ACMIA, EMIT-VIVA, CEDIA-PLUS, and HPLC. Samples were collected from kidney transplant patients monitored with the traditional blood CsA trough level (C0, n=73) and the new sampling at 2-h post CsA dosing (C2, n=59).

RESULTS

Overall, the correlations between HPLC and other methods were good (r values ranging from 0.85 to 0.97). The use of C2 concentrations to monitor CsA exposure were associated with an overall better performance of all the immunoassays as compared with C0 values. However, none of the immunoassays agreed with the guidelines proposed in the Lake Louis Consensus Conference. Of note, the CEDIA-PLUS was the only that provided a linear relationship with HPLC for both sampling times. A false positive case associated with ACMIA was also documented in blood samples from a patient withdrawn from CsA for 1 month.

CONCLUSION

These data suggest that the performance of some of the most used immunoassays is not satisfactory, eventually leading to incorrect therapeutic decision guided by erroneous CsA monitoring.

Evolution of the therapeutic drug monitoring of cyclosporine

The argument for the therapeutic monitoring of cyclosporin A (TDM-CyA), to optimize efficacy and safety, has been discussed in the last 25 years and it is still debated. Although CyA has been for more than 20 years the mainstay of immunosuppression in organ transplantation, no consensus has yet been achieved on TDM-CyA. The first proposed use of CyA was at fixed doses, but this was soon abandoned, and the predose, trough C0 blood level concept was introduced as a tool for TDM-CyA; however, no correlation could ever be shown between the various proposed trough therapeutic windows and major clinical events. On the contrary, the TDM-CyA of full area-under-the-curve (AUC) 0-12 exposure, significantly correlated with acute rejection and renal toxicity. The use of Neoral demonstrated that the region of most variability in CyA pharmacokinetics and the greatest calcineurin inhibition were confined within the AUC0-4, introducing the concept of absorption profiling. A further simplification come from the demonstration that C2, the single blood concentration measurement 2 hours after Neoral administration, was a significant accurate predictor of AUC0-4. The TDM-CyA with C2 has now been clinically validated in kidney, liver, and heart transplant recipients. In the last 25 years of TDM-CyA, some concepts have become clear: inadequate CyA exposure is a key risk factor for acute rejection and may contribute to the development of chronic rejection; C0 predose monitoring does not accurately measure CyA exposure. Thus, C2 single sampling offers today an innovative, simple, and accurate alternative for the pharmacokinetic clinical monitoring of CyA.

History of C2 monitoring in heart and liver transplant patients treated with cyclosporine microemulsion

Therapeutic drug monitoring of CsA has evolved since the introduction of CsA microemulsion. The purpose of the present review is to summarize the history of CsA concentration 2 hours postdose (C2) monitoring in heart and liver transplantation. C2 has been shown to be the best single time point that correlates with the area-under-the-curve, with a correlation coefficient (r2) ranging between .83 and.93. C2 monitoring (300 to 600 ng/mL) has resulted in a significant clinical benefit in long-term heart and liver transplant patients compared to trough level (C0) monitoring. Moreover, a C2 range of 300 to 600 ng/mL resulted in a similar calcineurin inhibition compared to a C2 range of 700 to 1000 ng/mL or a C0 range of 100 to 200 ng/mL while being less injurious to renal function. In de novo liver transplant patients not receiving induction therapy, the achievement of a target C2 of 850 to 1400 ng/mL by postoperative day 3 has resulted in a low acute rejection rate. Furthermore, C2 monitoring has been associated with a lower rejection rate in hepatitis C virus (HCV)-negative patients and with an overall lesser severity of acute rejection compared to C0 monitoring. In de novo heart transplant patients who receive antithymocyte globulin induction, a lower C2 range may be sufficient to prevent rejection and renal dysfunction. Future studies should help to fine-tune the optimal C2 range in heart or liver transplant patients receiving induction therapy and different maintenance immunosuppressive combinations.

In renal transplantation blood cyclosporine levels soon after surgery act as a major determinant of rejection: Insights from the MY.S.S. Trial

BACKGROUND

Target organs express antigens recognized directly by antigen-specific T cells, and their recognition is crucial to precipitate rejection. Then, the earliest T-cell activation is inhibited by cyclosporine A (CsA), the lowest would be the risk of rejection. Here, we aimed to assess this possibility in a large cohort of de novo kidney transplant recipients participating in an ongoing clinical trial, the Mycophenolate Steroid-Sparing (MY.S.S.) Trial.

METHODS

Three-hundred-thirty-four patients entered the prospective, multicenter MY.S.S. trial. The main aim of the study was to assess the predictive value of serial evaluation of blood CsA trough concentration (C0) and 2-hour postdose drug (C2) levels alone or in combination, and to identify which is the critical posttransplant measurement to target CsA therapy in order to minimize the risk of acute rejection. A very large number of CsA trough (N= 2236) and C2 (N= 2128) measurements during the first 6 months postsurgery were available for analysis. Patients with delayed graft function were excluded.

RESULTS

CsA trough levels measured at day 2 posttransplant were the strongest predictor of acute graft rejection over 6-month follow-up. Levels within 300 to 440 ng/mL were associated with the lowest risk of rejection, while for levels lower than 300 ng/mL, the risk of acute rejection was more than doubled. Higher levels failed to provide any further protection from graft rejection. CsA trough values predicted allograft rejection with an accuracy of 74%, while C2 levels considered alone had no predictive values at all.

CONCLUSION

Findings that among serial daily measurements posttransplant those taken as early as at day 2 have by far the highest capacity to predict rejection episodes, underline the need of targeting CsA therapy very early posttransplant with the goal to modulate early enough T-cell activation at the interface between the recipient's blood and the graft where alloimmune response actually initiates.

Renal transplantation: can we reduce calcineurin inhibitor/stop steroids? Evidence based on protocol biopsy findings

How to combine antirejection drugs and which is the optimal dose of steroids and calcineurin inhibitors beyond the first year after kidney transplantation to maintain adequate immunosuppression without major side effects are far from clear. Kidney transplant patients on steroid, cyclosporine (CsA), and azathioprine were randomized to per-protocol biopsy (n = 30) or no-biopsy (n = 29) 1 to 2 yr posttransplant. Steroid or CsA were discontinued or reduced on the basis of biopsy to establish effects on drug-related complications, acute rejection, and graft function over 3 yr of follow-up. Serum creatinine, GFR (plasma clearance of iohexol), RPF (renal clearance of p-aminohippurate), CsA pharmacokinetics, and adverse events were monitored yearly. At the end, patients underwent a second biopsy. Per-protocol biopsy histology revealed no lesions (n = 5, steroid withdrawal), CsA nephropathy (n = 13, CsA discontinuation/reduction), or chronic rejection (n = 12, standard therapy). Reducing the drug regimen led to overall fewer side effects related to immunosuppression as compared with standard therapy or no-biopsy. Steroids were safely stopped with no acute rejection or graft loss. Complete CsA discontinuation was associated with acute rejection in the first four patients. Lowering CsA to low target CsA trough (30 to 70 ng/ml) never led to acute rejection or major renal function deterioration. Biopsy patients on conventional regimen had no acute rejection, one graft loss, no significant change in GFR, and significant RPF decline. No-biopsy controls: no acute rejection, one graft loss, significant decline of GFR and RPF. By serial biopsy analysis, severe lesions did not develop in patients with steroid discontinuation in contrast to patients on standard therapy over follow-up. CsA reduction did not adversely affect histology. Per-protocol biopsy more than 1 yr after kidney transplantation is a safe procedure to guide change of drug regimen and to lower the risk of major side effects.

Universal approach to pharmacokinetic monitoring of immunosuppressive agents in children

Current data indicate that pharmacokinetic (PK) monitoring of cyclosporin microemulsion (CsA) should be performed using the 2-h concentration (C2), that tacrolimus (Tac) is commonly monitored using the trough level, and mycophenolate mofetil (MMF) should be monitored using the 1-h (C1), 2-h (C2) and 6-h (C6) concentrations. The three differing time-point requirements are cumbersome, and we aimed to develop universal guidelines for all three drugs using a large number of full PK profiles in children. One-hundred and twenty two stable pediatric patients, receiving either CsA (165 PK profiles, 69 patients, 24 with concomitant MMF) or Tac (122 PK profiles, 53 patients, 18 with MMF) were analyzed retrospectively. Pearson r for the CsA C2 was 0.90 [95% confidence interval(CI): 0.86-0.92], for Tac C2 r was 0.86 (95% CI: 0.80-0.90), and for MPA C2 r was 0.77 (95% CI: 0.68-0.83), respectively. For MPA, at least three time-points are required to accurately estimate the area under the concentration-time curve (AUC), and C1, C2 and C6 serve as best markers. Excellent AUC estimations could be obtained from a limited sampling strategy from C1, C2 and C6 or C0, C1, C2 and C4 with clinically acceptable errors for all three drugs. The AUC can be estimated with great precision by using an identical approach for all three drugs. Target AUCs for a given time-point after transplantation remain to be established.

Adequate early cyclosporin exposure is critical to prevent renal allograft rejection: patients monitored by absorption profiling

This study used receiver operating characteristic analysis to investigate the properties of area under the concentration-time curve during the first 4h after cyclosporin-microemulsion dosing (AUC0-4) and cyclosporin (CyA) levels immediately before and at 2 and 3h after dosing (C0, C2 and C3) to predict the risk of biopsy-proven acute rejection (AR) at 6 months. Ninety-eight kidney transplant recipients treated with CyA-microemulsion-based triple therapy immunosuppression were studied on post-transplant days 3, 5, and 7, and at increasing intervals thereafter. The most sensitive and specific predictor of AR was AUC0-4. Of the single time-point measurements, the measurement properties of C2 were closest to those of AUC0-4, and superior to those of C3. The relationship between C0 and subsequent AR was weak and did not reach statistical significance. On day 3, CyA AUC0-4 > or = 4,400 ng.h/mL and C2 > or = 1,700 ng/mL were each associated with a 92% negative predictive value for rejection in the first 6months. Pharmacokinetic measurements on or after day 5, and measurements on day 3 in patients with delayed graft function, were not predictive of AR. Adequate exposure within the first 3days post transplantation may be critically important in preventing subsequent rejection.

Glucocorticoids interfere with mycophenolate mofetil bioavailability in kidney transplantation

BACKGROUND

Steroids have been shown to induce the hepatic glucuronyltransferase (GT) expression enhancing the activity of uridine diphosphate-GT, the enzyme responsible for mycophenolic acid (MPA) metabolism. The impact of steroids on MPA pharmacokinetics, however, has not been investigated to date.

METHODS

As a part of a steroid-sparing clinical trial, we studied the effect of steroids on MPA bioavailability in 26 kidney transplant recipients.

RESULTS

Despite that the MMF dose did not change significantly with time, dose-normalized MPA AUC0-12h was lower during the first month (triple therapy, high doses of steroids) than at month 6 post-surgery (triple therapy, low maintenance dose of steroids (32.94 +/- 10.98 vs. 50.87 +/- 22.37 microg/mL. h; P < 0.01). During the steroid tapering and withdrawal phase (from month 6 to 21 post-Tx), plasma MPA trough and peak concentration as well as AUC0-12h progressively increased, while plasma MPA clearance and MPAG (the major MPA metabolite) trough levels declined. Renal function was stable throughout. Since cyclosporine A (CsA) may interfere with MPA pharmacokinetics, MPA and CsA also were measured in an additional control group of 12 kidney transplant patients at month 21 post-Tx who were still on triple therapy (MMF, CsA and steroids). Despite a similar CsA exposure, the control group had a significantly lower MPA AUC0-12h and higher MPAG trough concentration than patients on dual therapy at month 21 post-Tx.

CONCLUSION

These findings indicate that steroids interfere with MPA bioavailability, and that discontinuation of the drug results in higher MPA exposure, which may compensate at least in part for the lower immunosuppressive level achieved with the remaining dual therapy with CsA and MMF.

Influence of the cyclic variation of hydration status on hemoglobin levels in hemodialysis patients

BACKGROUND

Maintenance hemodialysis (HD) patients were studied to assess the effect on hemoglobin (Hb) concentration induced by the cyclic variation in hydration status.

METHODS

Forty-nine HD patients were examined in three consecutive HD sessions in a 1-week treatment period. In a subgroup of 23 patients, Hb levels also were investigated during the long interdialytic interval.

RESULTS

Hb levels at the end of the long interdialytic interval were significantly lower by 0.5 to 0.6 g/dL (5 to 6 g/L) than those at the end of short intervals. Among all pre-HD and post-HD Hb values, levels measured at the end of short intervals were closest to the mean Hb value of the week, derived from calculation of the area under the curve (12.0 +/- 0.2 g/dL [120 +/- 2 g/L]). Intradialytic Hb increments were different in the three sessions (+1.6 +/- 0.1 g/dL [+16 +/- 1 g/L] after the long interval, +1.1 +/- 0.1 g/dL [+11 +/- 1 g/L] and +1.1 +/- 0.1 g/dL [+11 +/- 1 g/L] after short intervals [P < 0.001] and proportionate to weight loss [-3.4 +/- 0.1, -2.7 +/- 0.1, and -2.6 +/- 0.1 kg, respectively; P < 0.001]). Hb level increment and weight loss correlated directly (r = 0.527; P < 0.0001); each 1 L of ultrafiltration (UF) led to an increase in Hb level of approximately 0.4 g/dL (4 g/L). Plasma refilling accounted for an approximately 45% decrement in the intradialytic increase in Hb level 2 hours post-HD.

CONCLUSION

This study suggests that: (1) the end of the short interdialytic period is the most appropriate timing for anemia assessment, and (2) the remarkable hemodiluting effect of post-HD plasma refilling protects against excessive increments in Hb levels induced by UF.

Sampling strategy to calculate the cyclosporin-A area under the time-concentration curve

The complete area under the time-concentration curve (AUC) is considered to be the gold standard for cyclosporin-A (CyA) monitoring. However, complete AUC is time- and cost-consuming. For this reason, we reviewed 259 4-h AUC (AUC0-4) performed in 74 renal transplanted patients in order to construct an equation to calculate AUC0-4. All samples were drawn from one adult population 13 days following transplantation, in order to allow the cyclosporin metabolism to stabilize. Regression analysis was done either with each or with a combination of two variables. Cyclosporin-A blood concentration at the second hour after the oral dose (C2) was the best predictor of AUC0-4, where AUC0-4 = 451 +(2.73 x C2), R2 = 0.87, p<0.001. The combination of C1 and C2 only, offered a better mathematical improvement to the C2 equation. This equation was further validated in 33 other CyA pharmacokinetic profiles performed in eight patients who had not participated in the equation development. In this new population, the C2 equation excellently predicted the trapezoidal AUC0-4 (R2 = 0.81). Our data shows that C2 can be safely used to estimate AUC0-4. The C2 equation simplifies CyA monitoring because of its high-predictive value and clinical feasibility.

How pharmacokinetic and pharmacodynamic drug monitoring can improve outcome in solid organ transplant recipients

Within the field of solid organ transplantation there is an unprecedented interest in therapeutic drug monitoring of immunosuppressive drugs. Ideally therapeutic drug monitoring should cost-effectively lead to improved efficacy of the drug and to a reduction in side effects. Therapeutic drug monitoring will be most effective if there is a large interpatient variability and a small intrapatient variability. Therapeutic drug monitoring in transplantation is largely based on correlations between drug concentrations and toxicity or between drug concentrations and efficacy. Pharmacodynamic monitoring of immunosuppressive drugs has not reached the stage of widespread clinical application. In part this is caused by the fact that most of the pharmacodynamic assays are time-consuming, costly and in some cases only give a result after several days of incubation. Another reason for the limited interest in pharmacodynamic monitoring is the lack of data showing improved outcome if dose adjustment is based on pharmacodynamics rather than pharmacokinetics. On the other hand, such data are also lacking for pharmacokinetic monitoring. Prospective investigations on the contribution of therapeutic drug monitoring may result in further improvement of the safety and efficacy of our immunosuppressive regimens and more refined methods for therapeutic drug monitoring. There is no contest between pharmacokinetic and pharmacodynamic monitoring. Most likely the results of both ways of monitoring will be complementary.

Population pharmacokinetic model to predict steady-state exposure to once-daily cyclosporin microemulsion in renal transplant recipients

BACKGROUND

The microemulsion formulation of cyclosporin (CsA-ME) has a less variable absorption profile than the standard formulation (CsA-S), but only limited information is available about once-daily administration of CsA-ME.

OBJECTIVE

To develop a population pharmacokinetic model for once-daily CsA-ME that enables the prediction of individual steady-state area under the concentration-time curve (AUC) on the basis of blood concentration measurements and patient covariates.

PATIENTS AND METHODS

The steady-state pharmacokinetics of once-daily cyclosporin were studied in 60 stable renal transplant recipients before and after conversion from CsA-S to CsA-ME. For each formulation, 7 blood samples were collected from 50 patients (group A) at sparse timepoints over 2 weeks, and 10 blood samples were collected from 10 patients (group B) at fixed timepoints over 24 hours. A 2-compartment population model assuming time-lagged first-order oral absorption was fitted to the data from group A, using nonlinear mixed effects modelling (NONMEM). The data from group B were used to evaluate the predictive performance of the model.

RESULTS

Mean [+/- SD; coefficient of variation (%CV)] CsA-S doses of 245mg (+/- 92) resulted in cyclosporin blood concentrations of 214 microg/L (+/- 70) after 12 hours and 108 microg/L (+/- 23) after 24 hours; the mean estimated AUC to 24 hours was 7658 microg x h/L (30%). With mean CsA-ME doses of 206mg (+/- 59), cyclosporin blood concentrations were 212 microg/L (+/- 33) and 132 microg/L (25%) after 12 and 24 hours, respectively, and the mean estimated AUC(24) was 9357 microg x h/L (23%). A strong correlation between 12-hour concentrations and AUC(24) was observed for CsA-ME (r = 0.95, p < 0.001), but not for CsA-S (r = 0.59, nonsignificant); the correlation between 24-hour trough concentrations and AUC(24) was weaker for both formulations (r = 0.64, p < 0.05 and r = 0.37, nonsignificant, respectively). On the basis of the population model derived from group A, the single best timepoint to predict AUC(24) from blood cyclosporin concentration was at 8 hours [AUC(24) (microg x h/L) = 19.6 x cyclosporin concentration at 8 hours (microg/L) + 3035], resulting in a prediction error of 8.3 +/- 6.6% when applied to the measured AUC(24) of group B. Adverse events were observed after conversion in 18 patients; these events generally resolved spontaneously or after dosage reduction, but twice-daily administration was required in some patients.

CONCLUSIONS

Switching from once-daily CsA-S to CsA-ME results in more consistent and predictable cyclosporin pharmacokinetics. Adjustment of dosage or regimen may be required in some patients.

Pharmacokinetics help optimizing mycophenolate mofetil dosing in kidney transplant patients

BACKGROUND

Mycophenolic acid (MPA), the active metabolite of mycophenolate mofetil (MMF), is now routinely used as immunosuppressant in solid organ transplantation in a fixed daily dose regimen (2 g/d) in association with cyclosporine (CsA) and steroids. However, no correlation has been shown between fixed MMF dose and clinical outcome.

METHODS

Here we examined the possibility of optimizing MMF dosing by drug pharmacokinetic monitoring in 46 stable kidney transplant recipients. MPA plasma concentration profiles were measured by a reverse-phase high-performance liquid chromatography method 6-9 months after transplantation and related with routine laboratory analysis tests. Since MPA is extensively bound to serum albumin and only the free fraction is pharmacologically active, in a subgroup of 23 patients free plasma MPA was also determined.

RESULTS

Despite a comparable MMF dose, a large interindividual variability in both MPA area under the curve (AUC) from 0 to 12 h (range 10.1-99.8 microg/mL. h) and in trough levels (range 0.24-7.04 microg/mL) was found. Patients with AUC >40 microg/mL. h showed a better (p<0.05) renal function than patients with lower AUC (creatinine clearance 85.7+/-23.2 versus 64.5+/-17.5 mL/min), despite no difference in CsA dose, CsA AUC and blood CsA trough level. The percentage of free plasma MPA but not total MPA correlated with the red blood cell and leukocyte count.

CONCLUSIONS

Therapeutic MMF drug monitoring might contribute to a better management of kidney transplant recipient with the goal of optimizing drug dosing and limiting the risk of MMF-related toxicity.

A limited sampling strategy for cyclosporine area under the curve monitoring in lung transplant recipients

We developed a limited sampling strategy (LSS) for predicting cyclosporine (Neoral) area under the curve from concentration-time data obtained specifically from lung transplant recipients. The optimal and most clinically convenient LSS for lung transplant recipients, based on patient wait time, number of blood samples required, percent prediction error, and assessment of predictive performance is one that requires 2 blood samples collected at 1 and 3 hours post-dose: AUC = 1.75 x C(1) + 4.91 x C(3) + 185.62.

Approaching the therapeutic window for cyclosporine in kidney transplantation: a prospective study

Neoral dosing is traditionally based on cyclosporine (CyA) trough levels (C(0)). Four-h area under the curve (AUC(0-4)) for Neoral in the early posttransplantation period was shown previously to have a better correlation to acute rejection (AR) and CyA nephrotoxicity (CyANT), compared with C(0). An AUC(0-4) range of 4400 to 5500 microg/h per L during the first week was associated with the lowest AR and CyANT. This article describes a prospective study to assess the feasibility, safety, and efficacy of dosing Neoral solely by AUC(0-4) monitoring, regardless of C(0), in the first 3 mo after kidney transplantation. Fifty-nine kidney transplant recipients received Neoral-based triple immunosuppression. AUC(0-4) was measured on days 3, 5, 7, 10, and 14 and weeks 3, 4, 6, and 8, then monthly. Target AUC(0-4) was 4400 to 5500 microg/h per L. Dose was adjusted by percentage difference from target AUC(0-4). Ninety-four percent of AUC were performed on the scheduled day or close to it. No patients had CyANT while AUC(0-4) was in target range. Four patients had reversible CyANT with AUC(0-4) > 5500. Only 1 of 33 patients (3%) who achieved and maintained AUC(0-4) > 4400 by day 3 posttransplantation had AR, whereas 10 of 22 (45%) of those with day 3 to 5 AUC(0-4) < 4400 had AR (P: = 0.0002). In logistic regression analysis, higher early AUC(0-4) was the only significant variable associated with lower serum creatinine at 3 mo. Neoral dose monitoring by AUC(0-4) is a potentially valuable tool for optimizing Neoral immunosuppression. Attainment of a target range of 4400 to 5500 microg/h per L for AUC(0-4) early after transplantation has been demonstrated to reduce significantly the risk of AR and CyANT.

Limited sampling strategies for estimating cyclosporin area under the concentration-time curve: review of current algorithms

Cyclosporin, the drug of first choice in transplantation surgery, is characterized by a low therapeutic index and variable absorption, so close monitoring of the drug is required to optimize the dosing. Predose blood cyclosporin levels are measured routinely for therapeutic monitoring, but this approach is not optimal because the area under the concentration-time curve (AUC) correlates better with clinical events. However, conventional methods of measuring AUC require many blood samples, which is not viable in a routine clinical setting. AUC monitoring can be simplified for use in a clinical setting by using a limited sampling strategy (LSS) that allows AUC to be estimated using a small number of blood samples collected at specific times. This article reviews the current literature on estimating cyclosporin AUC using LSS. Thirty-eight papers suggesting the use of specific time points were found. LSS has been developed for different transplant types, with different dosing regimens, and with different assays. Most authors suggested either two- or three-sample equations. Results from authors who validated their models suggest that equations defined on one transplant type may be applicable to other transplant types, to both adults and children, and to early or late after transplantation. Moreover, it seems that there is flexibility in the choice of equations available to clinicians. The number of samples to collect for accurate estimations is a matter of debate, but a wise choice can minimize the number. The choice of the optimal LSS and validation are discussed.

Methods for clinical monitoring of cyclosporin in transplant patients

Cyclosporin was introduced into clinical practice in the early 1980s and has since been shown to prolong survival for transplant recipients. Because cyclosporin is a narrow therapeutic index drug and there are significant consequences associated with 'subtherapeutic' and 'supratherapeutic' concentrations, cyclosporin therapy is monitored as part of routine patient follow-up. However, the optimal method for the therapeutic drug monitoring of cyclosporin has yet to be defined. Currently, the most common method involves monitoring pre-dose trough concentrations, but this method is less than ideal. Other methods of monitoring cyclosporin therapy include monitoring the area under the concentration-time curve, limited sampling strategies, monitoring of single concentrations other than troughs and pharmacodynamic monitoring. Bayesian forecasting has been used successfully in clinical practice with other drugs with narrow therapeutic indices. However, few studies are available regarding Bayesian forecasting and cyclosporin. Existing studies are preliminary in nature and involve the old Sandimmun formulation rather than the Neoral formulation. Although these methods show promise, they have not gained widespread acceptance. This is because of their impracticality and the lack of prospective studies comparing other monitoring methods with trough concentration monitoring. Further comparative studies evaluating the impact of the specific monitoring method on definite patient outcomes are warranted.

Clinical benefit of neoral dose monitoring with cyclosporine 2-hr post-dose levels compared with trough levels in stable heart transplant patients

BACKGROUND

Based on the excellent correlation between cyclosporine A 2-hr postdose blood levels (C2) and the area under the concentration versus time curve, we evaluated the clinical benefit of Neoral dose monitoring with C2 compared trough levels (C0) in stable heart transplant patients.

METHODS

We studied 114 stable adult patients followed at the heart transplant clinic, who were >1 year after surgery. In May 1996 (period 1, follow-up 10+/-4 months), Neoral dose monitoring was based on C2 (300-600 ng/ml); while in May 1997 (period 2, follow-up 10+/-2 months), it was based on C0 (100-200 ng/ml). Cyclosporine A levels were measured by an enzyme multiplied immunologic technique. Clinical benefit was defined by the absence of acute rejection, no mortality, no fall in left ventricular ejection fraction >10%, and no increase in serum creatinine >10% (compared with baseline).

RESULTS

During period 1, Neoral dose, cyclosporine A, C0 and C2, and serum creatinine, decreased by 26, 56, 45, and 2.3%, respectively. At the end of period 2, the same variables increased by 24, 56, 38, and 10%, respectively (P<0.0001). The incidence of acute rejection was similar (period 1: 0.87%, period 2: 0.96%). The left ventricular ejection fraction (initial/final) remained stable (period 1: 57+/-91%/58+/-13%, period 2: 59+/-11d/58+/-10%). Mortality did not differ (period 1: 7.9%, period 2: 9.6%). A clinical benefit was observed in 69.3% of the patients during period 1 vs. 43.3% of the patients during period 2 (P<0.00001).

CONCLUSIONS

In stable heart transplant patients, a greater clinical benefit was observed when Neoral dose monitoring was performed according to C2, compared with C0.

Neoral monitoring by simplified sparse sampling area under the concentration-time curve: its relationship to acute rejection and cyclosporine nephrotoxicity early after kidney transplantation

BACKGROUND

Cyclosporine (CsA) dosing is traditionally based on trough blood levels (C0) rather than area under the concentration-time curve (AUC), although AUC correlates better with posttransplantation clinical events. For Neoral, AUC based on limited sampling correlates closely with full 12-hr AUC. The purpose of our study was to correlate C0 with AUC based on CsA levels at 0, 1, 2, 3, and 4 hr after dose (PK0-4) and to compare this AUC with C0 in predicting acute rejection (AR) and acute cyclosporine nephrotoxicity (CsANT) in de novo first kidney transplant patients.

METHODS

PK0-4 was done 2-4 days after starting Neoral for 156 patients. All received CsA-based triple-drug immunosuppression without antibody induction. AUC was calculated as projected 12-hr (AUC0-12) and actual 4-hr (AUC0-4) from the PK0-4 using the parallel trapezoid rule. Neoral dosing was based on C0 not AUC. AUC was retrospectively compared with C0 as a predictor of AR and CsANT during the first 90 days.

RESULTS

C0 correlated poorly with AUC0-12 and AUC0-4 (r=0.61 and r=0.42). C0 (mean+/-SEM) levels were not significantly different in 34 patients with and 109 without AR (293+/-21 vs. 294+/-11 microg/L, P=0.95). AUC0-12 and AUC0-4 were significantly lower in patients with than without AR (AUC0-12 9090+/-598 vs. 10608+/-336 microg x h/L, P=0.01; AUC0-4 3934+/-306 vs. 4802+/-166 microg.h/L, P=0.006). In stepwise regression analysis only AUC0-12 or AUC0-4 (P=0.03/P=0.02) and delayed graft function (P=0.007) predicted AR. AUC0-12, AUC0-4, and C0 were all significantly higher in patients with CsANT than without CsANT (AUC0-12 11746+/-650 vs. 10023+/-301 microg x h/L, P=0.01; AUC0-4 5270+/-358 vs. 4474+/-150 microg x h/L, P=0.01; C0 343+/-18 vs. 287+/-10 microg/L, P=0.01), but in stepwise regression analysis C0 was not an independent predictor of CsANT. Patients with AUC0-12 in the range of 9500 to 11500 microg x h/L or AUC0-4 between 4400 and 5500 microg x h/L had the lowest incidence of AR (13% and 7%, respectively) without significantly higher risk for CsANT.

CONCLUSION

C0 correlates poorly with AUC based on PK0-4. Early AUC based on PK0-4 is more closely associated with AR and CsANT than is C0. Our data suggest that a target AUC0-12 of 9500-11500 or AUC0-4 of 4400-5500 microg x h/L may provide optimal Neoral immunosuppression.

Nature and mediators of renal lesions in kidney transplant patients given cyclosporine for more than one year

BACKGROUND

Cyclosporine (CSA) has improved patients and organ-graft survival rates, but its chronic nephrotoxicity is still an issue. Although prolonged vasoconstriction could contribute to chronic CsA tubulointerstitial changes by producing chronic ischemia, this relationship has been difficult to demonstrate thus far, and cellular origin and mediators of these structural alterations remain ill-defined.

METHODS

As a part of a clinical trial in kidney transplant recipients on triple immunosuppressive therapy (CsA, azathioprine and steroid), which includes renal biopsy as "per protocol," 22 patients enrolled between 12 and 24 months posttransplantation underwent renal hemodynamic evaluation by measuring glomerular filtration rate and renal plasma flow by the plasma clearance of unlabeled iohexol and the renal clearance of para-aminohippuric acid, respectively. In parallel, the CsA pharmacokinetic profile was also determined. A week later, a protocol biopsy of kidney graft was performed. Light microscopy examination and localization of endothelin-1, RANTES, monocyte chemoattractant protein-1 gene expression by in situ hybridization in the graft specimens were evaluated and related to the pattern of histologic lesions.

RESULTS

Ten out of 22 kidney transplant recipients who underwent the protocol biopsy had CsA nephrotoxicity, eight had chronic rejection, and four had no lesions at histological examination. The total daily exposure to CsA was higher in patients with CsA nephrotoxicity than in those with chronic rejection or no lesions at biopsy. Renal function was preserved in the CsA toxicity group as compared with the chronic rejection group, despite some degree of renal hypoperfusion. Tubular atrophy and striped interstitial fibrosis were found in all patients with light microscopical evidence of CsA nephrotoxicity, whereas glomerular and arteriolar lesions were less frequent. Intense staining for endothelin-1, RANTES, and monocyte chemoattractant protein-1 mRNAs selectively localized at tubular epithelial cells was found in biopsies taken from patients with CsA nephrotoxicity, but not in the chronic graft rejection group, whose tubuli had only minimal staining for RANTES mRNA on a few occasions.

CONCLUSION

Long-term CsA administration to kidney allograft recipients leads to tubulointerstitial injury independently of its vascular effect. The possible contribution to the development of interstitial fibrosis of inflammatory and growth factors released by tubular cells in which CsA accumulates is proposed.

Comparison of neoral dose monitoring with cyclosporine through levels versus 2-hr postdose levels in stable liver transplant patients

BACKGROUND

We reported that cyclosporine 2-hr postdose levels (C2) correlate better with the AUC0-4 hr than trough levels (C0) in heart transplant patients receiving Neoral.

METHODS

We compared Neoral dose adjustment with C0 (group 1: 100-200 ng/ml) vs. C2 (group 2: 700-1000 ng/ml; group 3: 300-600 ng/ml) in 35 stable adult patients >1 year after liver transplantation. The AUC0-4hr was calculated, and simultaneous blood samples were obtained to measure calcineurin inhibition. Clinical benefit was defined as the absence of rejection and no increase in serum creatinine at the 7-month follow-up.

RESULTS

C2 correlated better with the AUC0-4 hr than C0 (r=0.92 vs. r=0.40). Neoral dose increased by 17% and 39% in groups 1 and 2, and decreased by 18% in group 3 (P=0.002 vs. group 1 and P=0.0004 vs. group 2). Serum creatinine increased by 2.1% and 16% in groups 1 and 2, and decreased by 5.1% in group 3 (P=0.006 vs. group 2). A clinical benefit was observed in 37.5%, 23%, and 82% of patients in groups 1, 2, and 3 (P=0.03 vs. group 1 and P=0.01 vs. group 2). Calcineurin inhibition was similar in all groups at 2-hr (44+/-17%, 39+/-30%, and 44+/-35%), in spite of different Neoral doses (2.9+/-0.9, 4.0+/-1.8, and 2.6+/-1.3 mg/kg/day) and C2 (857+/-226, 922+/-274, and 588+/-274 ng/ml).

CONCLUSIONS

C2 correlated better with the AUC0-4 hr than C0. Neoral dose monitoring with a C2 range of 300-600 ng/ml resulted in a lower dose and greater clinical benefit compared to C0 or a higher C2 in stable liver transplant patients. The correlation between calcineurin inhibition and clinical events deserves further research.

Abbreviated kinetic profiles in area-under-the-curve monitoring of cyclosporine therapy. Technical note

BACKGROUND

The new microemulsion formulation of cyclosporine (CsA-ME) displays more consistent pharmacokinetic properties than the original formulation and may allow successful implementation of an abbreviated area-under-the-curve (AUC) strategy.

METHODS

Here we compared two limited sampling strategies in order to define the one that best predicts AUC after CsA-ME in 51 renal transplant recipients with stable renal function. Pharmacokinetics were based on analysis of blood samples collected over 12 hours after drug administration by high-performance liquid chromatography (HPLC). Predicted AUC was estimated by using a three-point (0, 1 and 3 hr) or a two-point (2 and 6 hr or 0 and 2 hr) sampling strategy.

RESULTS

A simplified strategy with three time points of blood collection at 0, 1, and 3 hours after CsA-ME allowed adequate and accurate prediction of the daily exposure to CsA. AUC prediction with two-point sampling at 2 and 6 hours was less good with a very large error in prediction (only 59% of the estimated AUC were within the accepted range). This limitation was even more evident when the 0 and 2 hour time points were examined, in which only 51% of AUC estimates were included in the accepted range of variation (-10 to 10%).

CONCLUSIONS

A limited strategy of three-point sampling taken early after dosing allows an excellent and perfectly reliable prediction of the actual AUC.

Prevention of transplant rejection: current treatment guidelines and future developments

In the past 2 decades, progressive improvements in the results of organ transplantation as a therapeutic strategy for patients with end-stage organ disease have been achieved due to greater insight into the immunobiology of graft rejection and better measures for surgical and medical management. It is now known that T cells play a central role in the specific immune response of acute allograft rejection. Strategies to prevent T cell activation or effector function are thus all potentially useful for immunosuppression. Standard immunosuppressive therapy in renal transplantation consists of baseline therapy to prevent rejection and short courses of high-dose corticosteroids or monoclonal or polyclonal antibodies as treatment of ongoing rejection episodes. Triple-drug therapy with the combination of cyclosporin, corticosteroids and azathioprine is now the most frequently used immunosuppressive drug regimen in cadaveric kidney recipients. The continuing search for more selective and specific agents has become, in the past decade, one of the priorities for transplant medicine. Some of these compounds are now entering routine clinical practice: among them are tacrolimus (which has a mechanism of action similar to that of cyclosporin), mycophenolate mofetil and mizoribine (which selectively inhibit the enzyme inosine monophosphate dehydrogenase, the rate-limiting enzyme for de novo purine synthesis during cell division), and sirolimus (rapamycin) [which acts on and inhibits kinase homologues required for cell-cycle progression in response to growth factors, like interleukin-2 (IL-2)]. Other new pharmacological strategies and innovative approaches to organ transplantation are also under development. Application of this technology will offer enormous potential not only for the investigation of mechanisms and mediators of graft rejection but also for therapeutic intervention.