Feasibility of C2 Monitoring in Korean Renal Transplantation

Feasibility of C2 Monitoring in Korean Renal Transplantation J.B. Park, Y.S. Han, S.J. Kim, G.S. Choi, C.H.D. Kwon, S.K. Lee, D.J. Kim, and J.W. Joh ABSTRACT Background. In spite of efforts for simplified and optimal monitoring, variability of cyclosporine (CsA) absorption has shown limited clinical impact. We performed the present study to evaluate the feasibility of C2 monitoring and the optimal target C2 level in Korean recipients. Patients and Methods. Sixty recipients who underwent first living donor kidney transplantations between December 2003 and May 2005 and who were treated with a regimen of CsA, mycophenolate mofetil, and steroid were enrolled in this study. CsA dose was adjusted according to conventional trough levels. Blood samples were collected just before (C0) and at 1, 2, 3, 4, 6, 8, and 12 hours (C1, C2, C3, C4, C6, C8 and C12) after dosing on days 2, 3, and 7 posttransplantation. On days 14 and 28, we determined C0, C1, C2, C3, and C4. We compared CsA levels between a no rejection versus a rejection group. Results. In 8 recipients there were 1 or more acute rejection episodes (13.3%). C2 levels correlated closely with AUC0-4 on each day (r ⫽ .892–.944, P ⬍ .01), but C2 levels were not significantly different between the no rejection and the rejection group (P ⬎ .05). Mean C2 level on days 3 to 28 was significantly different between the 2 groups. (P ⫽ .045). One recipient (5.3%) with a mean C2 level greater than 1000 ng/mL underwent acute rejection. Conclusions. CsA concentration monitored as mean C2 levels early posttransplantation rather than a single point concentration on a single day was a predictor of acute rejection in kidney transplantation. Within the first month posttransplantation, the target C2 level is recommended to be over 1000 ng/mL for Korean recipients.

A

LTHOUGH CYCLOSPORINE (CsA) has been the mainstay of immunosuppression in kidney transplantation, the inconsistent and unpredictable absorption of CsA has limited the drug’s clinical efficacy. Therapeutic drug monitoring (TDM) is required because of the drug’s narrow therapeutic index and serious side effects due to inter- and intraindividual variability of drug exposure. The conventional CsA trough level (C0) has been routinely used to adjust the exposure level. However, despite individualized adjustments (even with the newer microemulsion formulation of CsA to enhance bioavailability), trough levels do not reflect drug exposure, as estimated by the area under the time-concentration curve (AUC), which is well correlated with drug exposure.1 They fail to correlate with individual episodes of acute rejection and nephrotoxicity. Pharmacokinetic studies have shown that the AUC over the entire 12-hour dosing interval (AUC0-12) is the most accurate measurement of overall drug exposure and is closely correlated with efficacy.2 The greatest inter- and

intrapatient variability in CsA absorption occurs during the first 4 hours, with an average time to the maximum concentration of about 2 hours.3–5 The CsA concentration during the first 4 hours closely correlates with the pharmacodynamic effects of calcineurin inhibition and the suppression of IL-2 production.4,5 Adjustment of the regimen according to the AUC requires multiple point samplings, which is impractical in routine patient care. This situation provided the impetus to further studies focusing on limited sampling strategies, eg, an abbreviated AUC0-4 by sparse sampling or a single sampling.6 Recent studies have shown that the CsA 2 hours From the Department of Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea. Address reprint requests to Sung-Joo Kim, MD, PhD, Department of Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, 50 Ilwon-Dong Kangnam-Gu, Seoul 135-710, Republic of Korea.

© 2007 by Elsevier Inc. All rights reserved. 360 Park Avenue South, New York, NY 10010-1710

0041-1345/07/$–see front matter doi:10.1016/j.transproceed.2007.07.086

Transplantation Proceedings, 39, 3105–3108 (2007)

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post-dose (C2) level closely correlated with the AUC generated by multiple point sampling. It was effective to differentiate between patients with appropriate and inappropriate drug exposure.7 Furthermore, these studies have shown that the single day C2 level within the first week after transplantation (on the 3rd or the 7th day posttransplantation) correlated with the incidence of acute rejection in the early posttransplantation period.6,8 In 2002, the Consensus on Neoral C2: Expert Review in Transplantation (CONCERT) study concluded that the C2 level is the best single time point predictor of AUC0-4 and that an adequate C2 level early after transplantation was associated with reduced risk of acute rejection in renal transplantation. The study recommended a target C2 level of 1500 to 2000 ng/mL in the first month posttransplantation.9 However, the CONCERT recommendation of the target C2 level was based on studies performed in North America. This recommendation needs appropriate evaluation for various clinical parameters, such as the different races of patients. The purpose of this study was to evaluate the feasibility and appropriate target C2 level after kidney transplantation in Korean recipients.

PATIENTS AND METHODS Patient Selection Between December 2003 and May 2005, 60 patients who were more than 15 years old and who received their first kidney transplant from a living donor participated in the study. Patients who had known malignancy, chronic liver or gastrointestinal disease, or any condition that would influence CsA absorption or metabolism were excluded from the study.

Immunosuppressive Protocol The patients were treated with an immunosuppressive regimen consisting of CsA, mycophenolate mofetil (MMF; Cellcept, Roche, Basel, Switzerland), and steroid. CsA (Cipol inj, Chong Kun Dang, Seoul, Korea) was initially administered at 4 mg/kg/d IV and CsA microemulsion (Cipol-N soft cap, Chong Kun Dang), the dosage of which was tripled, was administered orally on the 2nd postoperative day. MMF was given at 1500 mg/d unless side effects were noticed. The CsA exposure was adjusted according to the trough level with a target range of 250 to 300, 200 to 250, and 150 to 200 ng/mL for the 1st week, 1st month, and 3rd month after transplantation, respectively.

CsA Measurements Whole blood samples were collected just before (C0) and at 1 (C1), 2 (C2), 3 (C3), 4 (C4), 6 (C6), 8 (C8), and 12 (C12) hours after CsA dosing. Full 8-point pharmacokinetic measurements of CsA were performed on days 2, 3, and 7 after transplantation, and 5-point measurements on days 14 and 28. The AUC0-12 and the AUC over the first 4 hours of the 12-hour dose interval (AUC0-4) were estimated by using the trapezoidal rule. Samples were measured using a specific monoclonal enzyme multiplied immunoassay technique (TDxFLx Analyzer, Abbott Diagnostics, Abbott Park, Ill, United States).

PARK, HAN, KIM ET AL

Diagnosis The diagnosis of acute rejection was confirmed by percutaneous needle biopsy. Rejection classified according to the Banff 97 criteria was treated by steroid pulse therapy (SPT).

Endpoint Patients were followed for 6 months. The primary endpoint was biopsy proven by acute rejection within 6 months posttransplantation.

Statistical Analysis Continuous variables expressed as mean values ⫾ standard deviations (SD) were compared by Student t test. Nominal variables expressed as the number of cases (percentage) were analyzed by chi-square or Fisher exact test. Pearson’s correlation analysis as performed with SPSS 14.0 (SPSS Inc, Chicago, Ill, United States) was used for the analysis of correlations between C2 levels and the AUC0-4. Statistical significance was assumed at P ⬍ .05.

RESULTS Overall Outcomes

For the 60 recipients, the CsA concentrations were measured for 6 months posttransplantation. The baseline characteristics of the 60 recipients are shown in Table 1. Among the 60 recipients, there were 1 or more acute rejection episodes in 8 recipients. The mean time to rejection diagnosis was 45.4 days (range, 8 –104 days). All biopsy confirmed episodes were classified as mild to moderate in severity according to the Banff 97 classification; they all responded to SPT. There was no graft failure or loss in the study period. There was no delayed graft function or CsA-related nephrotoxicity. In 1 recipient, CsA-related hepatotoxicity with AST level above 200 IU transiently was observed, but normalized without further deterioration. Pharmacokinetics

On days 2, 3, and 7, the AUC0-4 closely correlated with the AUC0-12 (correlation coefficient: r ⫽ .510, .803, and .873, respectively, P ⬍ .001). The CsA concentrations post-dose on days 2, 3, 7, 14, and 28 were analyzed for correlation with the AUC0-4 (Table 2). On each day the C2 levels revealed the closest correlation (correlation coefficient: r ⫽ .892– .944, P ⬍ .01). Predict Value of Rejection

The C2 levels between the no rejection and the rejection groups were compared by means (Student t test; Table 3). Although the C2 levels on day 14 seemed to be different, there was no significance in either group (P ⫽ .054), whereas the mean C2 levels on days 3 to 28 were significantly different between both groups (P ⫽ .045). Target C2 Level

Among the 19 recipients with a mean C2 level above 1000 ng/mL (days 3–28), only 1 recipient (5.3%) underwent an acute rejection episode.

FEASIBILITY OF C2 MONITORING

3107 Table 1. Baseline Characteristics of Recipients

Age (range), y Sex (male/female) Etiology DM Hypertension CGN RPGN IgA nephropathy PCKD Unknown Underlying disease DM Hypertension Donor Type (related/unrelated) Age (range), y Sex (male/female) HLA mismatch 0 1 2 3 4 5 6 Panel reactive antigen (%) ⬍30% ⬎30%

Total

No Rejection Group

Rejection Group

P

40.68 ⫾ 10.76 (15–63) 33/27

41.27 ⫾ 10.57 (15–63) 28/24

36.88 ⫾ 11.95 (20–54) 5/3

ns ns ns

9 (15.0%) 2 (3.3%) 9 (15.0%) 2 (3.3%) 6 (10.0%) 2 (3.3%) 30 (50.0%)

7 (13.5%) 2 (3.8%) 8 (15.4%) 1 (1.9%) 4 (7.7%) 2 (3.8%) 28 (53.8%)

2 (25.0%) 0 1 (12.5%) 1 (12.5%) 2 (25.0%) 0 2 (25.0%)

7 (11.7%) 39 (65.0%)

5 (9.6%) 36 (69.2%)

2 (25.0%) 3 (37.5%)

47/13 36.23 ⫾ 10.69 (16–58) 27/33

43/9 35.42 ⫾ 10.82 (16–58) 23/29

4/4 41.50 ⫾ 8.54 (28–53) 4/4

6 (10.0%) 3 (5.0%) 14 (23.3%) 24 (40.0%) 8 (13.3%) 3 (5.0%) 2 (3.3%)

6 (11.5%) 3 (5.8%) 12 (23.1%) 20 (38.5%) 8 (15.4%) 1 (1.9%) 2 (3.8%)

0 0 2 (25.0%) 4 (50.0%) 0 2 (25.0%) 0

59 1

51 1

8 0

ns

ns

ns

ns

DM, diabetes mellitus; CGN, chronic glomerulonephritis; RPGN, rapidly progressive glomerulonephritis; PCKD, polycystic kidney disease; ns, nonsignificant.

DISCUSSION

Despite the variability of CsA absorption, there have been many efforts to propose effective, predictive means to monitor CsA exposure and guide dose adjustment. The AUC over the entire 12-hour dosing interval is the most accurate estimation of CsA exposure; it is inapplicable in the routine clinical setting. Many reports have shown the C2 level to be an effective, valuable predictor of clinical outcomes in the routine clinical setting as a single point determinant.6,8 However, there are limitations of the C2 Table 2. Correlation Between AUC0-4 and CsA Concentration (Correlation Coefficient r) AUC0-4 Day 2

C0 C1 C2 C3 C4 C6 C8 C12

⫺.032 .794† .912† .756† .245 ⫺.145* ⫺.174 ⫺.32

Day 3

Day 7

.170 .741† .892† .677† .156 .074 .196 .348†

†

.365 .788† .904† .715† .429† .268* .324† .131

*Correlation is significant at the .05 level (2-tailed). † Correlation is significant at the .01 level (2-tailed).

Day 14

Day 28

.183 .774† .895† .719† .404†

.299* .827† .944† .794† .493†

level as determined by single point sampling. Although adequate exposure during the immediate posttransplantation period is critical for successful outcomes, CsA exposure using a single day C2 level is probably insufficient to

Table 3. AUC0-4 and C2 Level Comparison in the No Rejection and Rejection Groups

Day 2 C2 AUC0-4 Day 3 C2 AUC0-4 Day 7 C2 AUC0-4 Day 14 C2 AUC0-4 Day 28 C2 AUC0-4 Mean C2 (days 3–28)

No Rejection (Mean ⫾ SD), n ⫽ 52

Rejection (Mean ⫾ SD), n ⫽ 8

P

809.09 ⫾ 383.21 2553.46 ⫾ 787.53

856.47 ⫾ 264.20 2702.38 ⫾ 797.69

.738 .621

1097.69 ⫾ 413.69 3084.43 ⫾ 915.92

912.16 ⫾ 466.62 2659.646 ⫾ 1106.69

.250 .239

891.69 ⫾ 319.43 2728.77 ⫾ 861.97

759.28 ⫾ 410.39 2192.45 ⫾ 1279.00

.298 .131

887.61 ⫾ 319.49 2602.77 ⫾ 846.33

659.30 ⫾ 178.73 2202.12 ⫾ 596.68

.054 .203

843.77 ⫾ 408.42 2622.13 ⫾ 1084.83 930.19 ⫾ 240.28

643.25 ⫾ 247.56 2285.38 ⫾ 857.34 743.50 ⫾ 236.22

.184 .406 .045

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represent the overall exposure. It is also inadequate to propose a target level. Furthermore, absorption soon after transplantation in the first 2 weeks has been known to be more variable than at later time points.10,11 In this study, despite scattered interindividual C2 levels, there was a significant difference between the 2 groups in the mean C2 level during 4 weeks, which reflects the overall exposure despite the inter- and intraindividual variability. There was only 1 acute rejection episode (5.3%) among recipients with a mean C2 level above 1000 ng/mL during this period. Einecke et al.12 proposed a C2 concentration between 500 and 600 ng/mL in European recipients with stable renal function, which was lower than the CONCERT recommendation. As a proposal for the target C2 level during the early posttransplantation period (4 weeks) in Koreans, we suggest that it be lower than in North Americans. REFERENCES 1. Cantarovich M, Besner JG, Barkun JS, et al: Two-hour cyclosporine level determination is the appropriate tool to monitor Neoral therapy. Clin Transpl 12:243, 1998 2. Lindholm A, Kahan BD: Influence of cyclosporine pharmacokinetics, trough concentrations, and AUC monitoring on outcome after kidney transplantation. Clin Pharmacol Ther 54:205, 1993 3. Johnston A, David OJ, Cooney GF: Pharmacokinetic validation of Neoral absorption profiling. Transplant Proc 32:53S, 2000

PARK, HAN, KIM ET AL 4. Halloran PF, Helms LM, Kung L, et al: The temporal profile of calcineurin inhibition by cyclosporine in vivo. Transplantation 68:1356, 1999 5. Sindhi R, LaVia MF, Paulling E, et al: Stimulated response of peripheral lymphocytes may distinguish cyclosporine effect in renal transplant recipients receiving a cyclosporine ⫹ rapamycin regimen. Transplantation 69:432, 2000 6. Canadian Neoral Renal Transplantation Study Group: Absorption profiling of cyclosporine microemulsion (Neoral) during the first 2 weeks after renal transplantation. Transplantation 72: 1024, 2001 7. International Neoral Renal Transplantation Study Group: Cyclosporine microemulsion (Neoral) absorption profiling and sparse-sample predictors during the first 3 months after renal transplantation. Am J Transplant 2:148, 2002 8. Clase CM, Mahalati K, Kiberd BA, et al: Adequate early cyclosporin exposure is critical to prevent renal allograft rejection: patients monitored by absorption profiling. Am J Transplant 2:789, 2002 9. Levy G, Thervet E, Lake J, et al: Patient management by Neoral C(2) monitoring: an international consensus statement. Transplantation 73:S12, 2002 10. Morris RG, Russ GR, Cervelli MJ, et al: Comparison of trough, 2-hour, and limited AUC blood sampling for monitoring cyclosporin (Neoral) at day 7 post-renal transplantation and incidence of rejection in the first month. Ther Drug Monit 24:479, 2002 11. Cole EH: Neoral monitoring: limitations of trough level monitoring and the potential role of limited sampling strategies. Transplant Proc 32:1556, 2000 12. Einecke G, Mai I, Fritsche L, et al: The value of C2 monitoring in stable renal allograft recipients on maintenance immunosuppression. Nephrol Dial Transplant 19:215, 2004