Comparison of Neoral and Sandimmun for induction and maintenance immunosuppression after kidney transplantation

We compared the mean trough level/dose (L/D) ratio, mean coefficient of variation (CV) of individual patients, and graft, patient, and rejection-free survival rates of 40 renal transplant recipients receiving Neoral (CyE) with 103 consecutive renal transplant recipients receiving Sandimmun (CyA). The mean L/D ratio on the 3rd post-transplant day (16.2 vs 11.8, P < 0.04), in the 1st week (24.6 vs 16.1; P < 0.03), and 1st month (39.1 vs 28.7; P < 0.05) were higher in the CyE group. In both groups the L/D ratio improved in proportion to the duration of time post-transplant and reached a maximum in the 3rd post-transplant month. In the early post-transplant period in particular, the number of patients achieving target levels was significantly higher, and the mean dose needed to achieve target levels lower, in the CyE group. The variation in trough levels, demonstrated by the CV, was lower in the CyE group (0.41 ± 0.14) than in the CyA group (0.62 ± 0.21; P < 0.005). Actuarial 1-year patient and graft survival rates in the CyE group were 100 % and 96 %, respectively; these were similar to the 100 % and 95 % in the CyA group. The 1-year rejection-free survival rate in the CyE group was 61 % compared to 43 % in the CyA group (P < 0.02). We conclude that it is possible to obtain higher blood trough levels at lower doses by administering CyE, particularly in the early post-transplant period. The lower variability of trough levels and the higher L/D ratio in the CyE group, which are related to improved bioavailability of CyE, may explain the lower rejection rate among these patients. In this study, the microemulsion formulation of cyclosporin (CyE) was found to be more beneficial and cost-effective as induction and maintenance immunosuppression than the conventional formulation (CyA). Received: 28 January 1997 Received after revision: 13 May 1997 Accepted: 15 May 1997     

Comparison of Neoral and Sandimmun cyclosporin A pharmacokinetic profiles in young renal transplant recipients

A major factor influencing whole blood cyclosporin A levels in young children with renal transplants is the variable absorption of Sandimmun (SIM). Neoral (NEO) is a new microemulsion of cyclosporin A (CYA) that has been reported to have better absorption characteristics. We compared the pharmacokinetics of SIM and NEO in nine renal transplant recipients aged less than 11 years (range 4.8 – 10.9 years) and observed clinical parameters during 6 months of NEO therapy. Median CYA dosage was 149 mg/m² per day (range 98 – 226). We observed an increase in the maximum CYA concentration (C_max) of 114%, an increase in area under the curve (AUC) of 71% and the time to reach C_max was reduced from 1.75 h to 1.25 h with NEO, while 12-h trough levels (C12 h) did not change significantly. AUC correlated with C12 h for SIM (r ² = 0.833) and NEO (r ² = 0.699) and also C1.5 h for NEO (r ² = 0.775). During 24 weeks’ follow-up, the coefficient of variation of CYA levels was lower for NEO (13%) than for SIM (20%). Although CYA dosages at the start and the end of 6 months on NEO were similar, only one patient was maintained on a constant dose. Four patients had acute reversible rises in plasma creatinine which responded to a 11% reduction in NEO dose; their increase in AUC was greater than those patients not showing a rise in plasma creatinine. Overall, median plasma creatinine was unchanged at the end of the study. NEO was well tolerated by the patients; temporary nausea and headache were experienced by three patients and one of them stopped NEO after 20 days. Other biochemical parameters were not significantly different on NEO. Received May 28, 1996; received in revised form and accepted October 24, 1996     

Influence of bile on cyclosporin absorption from microemulsion formulation in primary liver transplant recipients

We analysed the absorption, after oral application, of a new galenic form of cyclosporin A (CyA-NOF) in liver-grafted patients (n=12) during the 1st week (days 2–4) after transplantation. Pharmacokinetic profiling was performed with an open or clamped T tube in situ or with the T tube absent. The pharmacokinetic parameters of CyA-NOF were influenced by T tube clamping and bile diversion. The highest AUC, C_max and earliest T_max values were found in patients without a T tube in situ, indicating that absorption of CyA-NOF in patients during the early course after liver transplantation is not bile-independent. CyA-NOF, at a dose of 7.5 mg/kg, was enterally absorbed with appropriate AUC and C_max levels. Patients receiving a starting dose of 7.5 mg/kg were successfully maintained on CyA-NOF during the subsequent clinical course.     

Pharmacokinetics of cyclosporine in pediatric long-term liver transplant recipients converted from Sandimmun to Neoral

Absorption of cyclosporin from the microemulsion formulation Neoral is less variable than from Sandimmun. Because of a lack of data in pediatric liver transplant recipients, the pharmacokinetic profiles with Sandimmun and Neoral were compared in a conversion study. Thirty-eight children with stable graft function were converted 2–12.3 years post-transplant at a 1:1 ratio. The trough-level (C_min) with Neoral was 123 ± 39 ng/ml versus 134 ± 29 ng/ml with Sandimmun (P = NS), the area under the time-concentration curve (AUC) was 3325 ± 1125 ng_*h/ml versus 2423 ± 846 ng_*h/ml (P < 0.001), the peak concentration (C_max) was 650 ± 280 ng/ml versus 337 ± 142 ng/ml (P < 0.001), and the median time to C_max was 2 h (range 0.5–3 h) versus 4 h (range 1–8 h; P < 0.05). The weak correlation between C_min and AUC with Sandimmun (r = 0.5; P = NS) was improved by using Neoral (r = 0.7; P < 0.001). The best predictor of AUC was the 2-h concentration (C_{2 h}) of Neoral (r = 0.9; P < 0.001). Increased absorption and a more predictable pharmacokinetic profile with Neoral permit safer therapeutic monitoring in children. The exclusive measurement of Neoral-C_{2 h} allows one to estimate drug exposure with high precision ( > 90 %). Received: 12 February 1997 Received after revision: 16 May 1997 Accepted: 5 June 1997     

Lipid abnormalities in stable liver transplant recipients – effects of cyclosporin, tacrolimus, and steroids

Dyslipidemia is common after liver transplantation, but the underlying mechanisms are largely unknown. We studied the lipid profile of 27 liver transplant recipients randomized to receive either cyclosporin (CyA, n = 14) or tacrolimus (n = 13) and compared them with 20 healthy, matched controls. Before transplantation, patients presented low total and low-density lipoprotein (LDL) cholesterol (as compared to controls) that increased shortly, i. e., 3 months, after transplantation. Eighteen months post-transplantation, total and LDL cholesterol levels decreased to pretransplant values but tended to remain higher in CyA-treated patients. However, at that time, prednisone treatment was more prevalent among CyA-treated than tacrolimus-treated patients and fully accounted for the difference in cholesterol levels. Indeed, regardless of therapy, patients not receiving prednisone exhibited lower cholesterol levels than prednisone-treated patients and controls. We conclude that prednisone therapy, rather than CyA or tacrolimus immunosuppression, seems to be the major determinant of increased cholesterol levels. Received: 19 June 1997 Received after revision: 24 October 1997 Accepted: 10 November 1997     

Two grams daily of oral acyclovir reduces the incidence of cytomegalovirus disease in CMV-seropositive liver transplant recipients

Our objective in this study was to determine the efficacy of 2 grams a day of oral acyclovir administered for 16 weeks after transplantation for the prevention of cytomegalovirus (CMV) infection and disease in CMV-seropositive liver transplant recipients. Seventy-three adult liver transplant recipients, seropositive for CMV, were randomized to receive either 2 grams a day of oral acyclovir for 16 weeks after transplantation or no prophylaxis. The incidence of CMV disease was significantly lower in the acyclovir group (5 %) than in the control group (27 %; P < 0.05). By log-rank analysis, the differences in the probability of presenting CMV disease over the first 16 weeks and over the 1st year were also significant (P < 0.05). We conclude that 2 grams a day of oral acyclovir provides effective prophylaxis against CMV disease in CMV-seropositive liver transplant recipients. Received: 14 March 1997 Received after revision: 30 May 1997 Accepted: 9 June 1997     

Long-term cyclosporin A pharmacokinetic profiles in pediatric renal transplant recipients

To study the long-term effect of cyclosporin A (CyA), 94 6-h and 29 12-h pharmacokinetic profiles were evaluated in 32 children at least 1 year after renal transplantation. Children weighing less than 25 kg needed significantly higher doses of CyA than those weighing more than 25 kg(9.8 vs 5.3 mg/kg per day; P<0.001) to achieve similar trough levels (TL). The average dose of CyA required to achieve the target TL declined gradually with time after transplantation. The average area under the curve over 6 h (AUC/6) correlated strongly with the AUC/12 (r=0.967; P<0.001). The AUC/6 of patients with biopsy-proven CyA toxicity was significantly higher than for those without toxicity (Mann-Whitney U-test P<0.05) despite similar TL. We conclude that AUC monitoring for 6 h provides valuable information not only on TL but also on the absorption and elimination characteristics of CyA as well as on the potential for CyA toxicity.     

The impact of (1:1) cyclosporine A conversion to its microemulsion formulation on the kidney function of patients with cardiac allografts

Due to the large variations in the absorption and bioavailability of conventional cyclosporine A (CyA), 1:1 (mg:mg) conversion to its microemulsion formulation (Neoral) has been advocated in transplant recipients. However, the renal hazards and biochemical effects of such conversions and not known in cardiac transplant recipients. In this study, 68 cardiac transplant recipients who were receiving conventional CyA, for a period of 61.3 +/- 36.0 (mean +/- standard error (SE)) months, were switched to the microemulsion formulation (Neoral). The biochemical and renal function tests were evaluated at 1, 3, 6, 9 and 12 months pre- and post-conversion of CyA. The results obtained post-conversion were compared with those of the baseline (pre-conversion). Serum creatinine and uric acid levels significantly increased post-conversion to the microemulsion formulation. One patient required discontinuation of the microemulsion in an attempt to reverse severe renal failure. In spite of a significant decrease in the microemulsion dose at 6, 9 and 12 months, there was a significant increase in the whole blood CyA trough levels at 9 and 12 months of conversion. There was no significant change in blood pressure, serum total cholesterol or potassium post-conversion. Our results suggest that after 1:1 (mg:mg) conversion of CyA to its microemulsion formulation, there will be a significant rise in serum creatinine, uric acid and whole blood trough CyA levels necessitating significant dose reduction. This effect is probably due to the markedly improved absorption and bioavailability of the latter.     

Prognostic factors of long-term allograft survival in 632 CyA-treated recipients of a primary renal transplant

A total of 632 cyclosporin (CyA)-treated primary renal allograft recipients with a functioning graft at 6 months were retrospectively evaluated for risk factors correlated with long-term allograft function. Mean follow-up after the 6th month was 68.4 ± 40.6 months. One hundred twenty-one of these patients (19 %) were lost: 29 died (23/29 with a functioning graft), 77 of the remaining 92 (83 %) lost their graft because of chronic allograft dysfunction, 9 due to recurrence of glomerulonephritis, 5 due to renal artery thrombosis, and 1 due to chronic CyA toxicity. At univariate analysis, factors correlated with a better renal (R) and pure renal (PR) allograft survival were: dialysis duration of less than 5 years, fewer than 2 rejections within the 6th post-Tx month, immediate graft function recovery, plasma creatinine below 1.5 mg/dl at the 6th month, age at Tx above 15 years, and receiving a living donor graft. Cox's regression analysis was also performed to obtain relative risks for the same parameters. Long-term dialysis patients had more frequent late recoveries (P = 0.002) and reductions in therapy (P = 0.01) in order to reduce the side effects of steroids. In young patients receiving an initial oral CyA dose of 17 mg/kg per day, steroids were stopped at the 6th month in order to achieve catch-up growth: only one such patient lost his graft. In contrast, 72 % of the young patients who lost their grafts received an initial oral CyA dosage of 13 mg/kg per day. Thus, young patients did worse not because of steroid withdrawal, but because of inadequate initial CyA dosage. These results suggest that although we cannot exclude alloantigen-independent mechanisms as factors that stimulate progression of chronic allograft dysfunction, it would appear that the initial lesions are induced by events mostly mediated by immunological mechanisms. Received: 28 January 1997 Received after revision: 4 April 1997 Accepted: 8 April 1997     

Reduced variability of Neoral pharmacokinetic studies in pediatric renal transplantation

In adult renal transplant recipients the Neoral area under the curve (AUC) displays less inter- and intra- individual variability than Sandimmune, and those renal transplant recipients with reduced intra-individual variability of the AUC have a lower risk for chronic rejection. As variability of Neoral pharmacokinetic (Pk) parameters has not been investigated in pediatric renal transplant recipients, we retrospectively analyzed 453 Pk profiles in 14 pediatric patients who were switched from Sandimmune to Neoral and compared the inter- and intra-individual variability of the Pk profiles on both formulations. After the switch, we observed less inter- and intra-individual variability of AUC, the 2-h concentration, and the oral clearance. As clearance with both formulations is supposedly equal, the significantly lower intra-individual variability of oral clearance is most likely an effect of less variable absorption. While the lower inter-individual variability of the Pk parameters suggests increased success in keeping cyclosporine concentrations on target, the lower intra-individual variability leads to the hypothesis that with Neoral, a lower incidence of chronic rejection might be achieved. Received: 8 February 2000 / Revised: 17 May 2000 / Accepted: 22 May 2000     

Neoral吸收期血药浓度和药物暴露量在中国成人肝移植受体中的变异性分析

目的通过分析中国成人肝移植受体中Neoral吸收期血药浓度与药物暴露量的变异性，为临床上发展新的Neoral治疗药物监测方法提供理论依据。方法通过定期测定22例中国成人肝移植受体口服Neoral前及服药后1、2、3、4h的血药浓度，采用个体及群体药代动力学的方法计算出个体内和个体间变异系数(CV）。结果Neoral血药浓度和AUC0～4的个体内和个体间变异系数均在服药头2h达到高峰，此后逐渐下降。术后10～11d个体间的浓度及AUC变异系数均最高。结论Neoral吸收期的变异性主要集中在服药后头2h。服药后1w左右是变异性最大的时期。     

Pharmacokinetics of cyclosporine in monkeys after oral and intramuscular administration: relation to efficacy in kidney allografting

In cynomolgus and rhesus monkeys, the dose-normalized exposure of cyclosporine administered orally as microemulsion preconcentrate (Neoral) was lower than that upon intramuscular administration. For oral administration, mean values ( ± SD) of C_max, 24-h area-under-the curve (AUC) and 24-h trough level, all normalized for a 1 mg/kg dose, were 20 ± 9 ng kg/mg ml, 210 ± 70 ng h kg/mg ml and 2.6 ± 0.9 ng kg/mg ml, respectively. For intramuscular administration, levels were about 5.5-fold, 9-fold and 22-fold higher. Based on pharmacokinetic data, the efficacy of oral cyclosporine treatment (without any other immunosuppressant) was evaluated in life-supporting cynomolgus monkey kidney allotransplantation. Rejection-free kidney allograft survival could be achieved using oral cyclosporine monotherapy with average 24-h trough concentrations above 100 ng/ml during maintenance treatment. Typically, daily oral doses of 100 mg/kg–150 mg/kg during the first two weeks post-transplantation, followed by daily 30 mg/kg–100 mg/kg dose levels during subsequent maintenance can result in long-term allograft survival, with 24-h average trough levels in individual animals during maintenance between 110 ng/ml and 700 ng/ml. Received: 1 October 1997 Revised: 20 April 2001 Accepted: 7 June 2001     

Delayed primary closure of the abdominal wall after cadaveric and living related donor liver graft transplantation in children: a safe and useful technique

Due to the shortage of size-matched liver donors, relatively oversized liver grafts (even after ex situ volume reduction) are frequently used for liver transplantation in children. This was recently observed when livers from large, living related donors were procured for transplantation in very small recipients. Given that abdominal hyperpressure can compromise vascular flow in the new graft, primary closure of the abdomen was delayed by temporary Silastic prosthetic closure in selected cases. The new technique was original in that the skin was closed, avoiding fluid loss and reducing the risk of infections reported with other techniques, and in that reoperation allowed for a delayed, but primary-type, closure (fascia and skin) that resulted in an esthetically correct aspect. Over a period of 7 years, 330 pediatric liver transplantations were performed, and delayed prosthetic closure was achieved successfully and safely in 47 cases. The present report outlines this clinical experience. Received: 26 May 1997 Received after revision: 14 October 1997 Accepted: 19 November 1997     

Conversion of Twice‐Daily Tacrolimus to Once‐Daily Tacrolimus Formulation in Stable Pediatric Kidney Transplant Recipients: Pharmacokinetics and Efficacy

The pharmacokinetics, efficacy and safety of once‐daily tacrolimus formulation (Tac‐OD) were assessed in 34 stable pediatric kidney transplant recipients. Enrolled patients received their dose of twice‐daily tacrolimus formulation (Tac‐BID) on study Days 0 through 7. On the morning of study Day 8, the total daily doses for patients were converted to Tac‐OD on a 1:1 basis and maintained on a once‐daily morning dosing regimen. Tacrolimus pharmacokinetic profiles were obtained on study Days 7, 14 and 28 (after dose adjustment). Although the mean C₀ concentrations (4.10 ± 1.16–3.53 ± 1.10 ng/mL, p = 0.004), and AUC_0–24 (151.8 ± 41.6–129.8 ± 39.3 ng h/mL, p < 0.001) were decreased significantly after a 1:1 based conversion, there was high interindividual variability. The dose of Tac‐OD was decreased in 26.5% and increased in 44.1% of patients. The resultant tacrolimus dose and pharmacokinetic profiles on study Day 28 were comparable to those on Day 7. There were no serious adverse events. In conclusion, Tac‐BID can be safely converted to Tac‐OD in stable pediatric kidney transplant patients with the heightened therapeutic drug monitoring. Effects of drug conversion on the cardiovascular risk factors, neurological side effects and adherence should be further evaluated.

     

Once-Daily Tacrolimus Extended-Release Formulation: 1-Year Post-Conversion in Stable Pediatric Liver Transplant Recipients

The pharmacokinetics, safety and tolerability of a once-daily formulation of tacrolimus (tacrolimus extended-release formulation; XL formerly referred to as MR or MR4) were assessed in 18 stable pediatric liver transplant recipients who were converted from the twice-a-day formulation of tacrolimus (TAC) to XL. Patients received their twice-a-day dose of TAC on study days 1 through 7. Beginning on the morning of study day 8, patients were converted to XL on a 1:1 (mg:mg) basis for their total daily dose, and were maintained on a once-daily AM dosing regimen using the same therapeutic monitoring and patient care techniques employed with TAC. Based on pharmacokinetic profiles obtained on study days 7 (TAC) and 14 (XL), steady state exposure (AUC(0-24)) was equivalent between XL and TAC; the mean XL/TAC ratio for lnAUC(0-24) was 100.9% (90% CI: 90.8%, 112.1%). AUC(0-24) and C(min) were strongly correlated at steady state (correlation coefficient: XL 0.90, TAC 0.94). During the first year post-conversion, there were no cases of acute rejection, discontinuation of XL, graft loss or death. The safety profile of XL was consistent with that known for TAC. These results support the safe and convenient conversion of pediatric liver transplant recipients from twice-a-day TAC to once-daily XL.     

Comparison of the pharmacokinetics of tacrolimus and cyclosporine at equivalent molecular doses

Even though calcineurin inhibitors, namely Tacrolimus (FK) and Cyclosporine (CsA) share similar physicochemical properties and a common mechanism of action, their pharmacokinetics (pk) are different and unpredictable. Both drugs are metabolized by cytochrome P450-3A4 isoforms in the liver and in the mucosa of the upper gastrointestinal tract. FK in clinical practice is given in doses up to 50-fold lower than those of CsA due to its greater potency. It is often assumed that the diverse dosing contributes to the observed pharmacokinetic differences between the two drugs. The objective of the present study was to compare single-dose pk profiles of the two drugs, following oral and intravenous administration, on the basis of equivalent molecular dosing, thus ruling out the quantitative factor. Five healthy volunteers and 14 dialysis patients (7 hemodialysis, 7 peritoneal dialysis) were included in the study. Comparing the pharmacokinetic parameters obtained from the drugs, it appeared that cyclosporine has an greater primary volume of distribution and clearance rate compared to tacrolimus. No other statistically significant differences were observed regarding bioavailability, absorption rate, or elimination rate. The only significant correlation between the pk values of the drugs was in primary volume of distribution. We conclude that even at equivalent molecular doses the pk of each drug remains unique and unpredictable. Furthermore our data fail to reveal significant correlations between the bioavailability, clearance, absorption, and elimination rates of the two drugs.     

Prevention of graft rejection and graft-versus-host reaction by a novel immunosuppressant, FTY 720, in rat small bowel transplantation

In the present study, we examined the immunosuppressive effect of a new drug, FTY 720, on small bowel transplantation (SBT) in rats. Grafts from (LEW × BN) F 1-to-LEW rats treated with FTY 720 at 0.5 mg/kg from day 0 to 14 post-SBT survived significantly longer than untreated grafts. In addition, the administration of FTY 720 combined with cyclosporin (CyA; 5 mg/kg per day) had a synergistic effect on allograft survival. The graft-versus-host reaction (GVHR) that occurred in the LEW-to-F 1 rats was markedly reduced after the administration of FTY 720. FTY 720 combined with a low dose of CyA completely abrogated GVHR without any adverse reaction. FTY 720 treatment resulted in a significant decrease in the number of lymphocytes in the peripheral blood and the spleen, but the number of peripheral neutrophils was unchanged. Thus, FTY 720 would appear to be an ideal drug to combine with CyA in order to control the immune reaction after SBT. Received: 19 February 1997 Received after revision: 23 May 1997 Accepted: 9 June 1997     

Overview of the clinical experience with Neoral in transplantation.

The microemulsion preparation of cyclosporine, Neoral, was introduced to improve the limited and sometimes unpredictable absorption of cyclosporine from the gut. Preclinical studies proved a superior bioavailability measured by the AUC and a definitively better predictability of the pharmacokinetic properties. Large-scale randomized and open-labeled studies have been carried out to prove and establish the safety, tolerability, and equal or superior efficacy of NEO if compared with SIM. There is broad evidence that NEO is safe and well tolerated in de novo and stable renal allografts. There are some arguments that NEO has favorable properties in poor absorbers, in patients in need for high dosage per kg body weight. Benefits for some populations such as children, African Americans, and diabetics have been detected. In combined kidney-pancreas transplantation a significant improvement of absorption has been proven. NEO has also been investigated in nonrenal transplants such as heart, lung, and liver transplantation. There are proven dose reduction in heart transplants; significant better absorption in lung transplants, in particular in patients with cystic fibrosis; and no further or even a diminished need for intravenously given CsA in liver transplantation. Studies are now reported for the use of NEO in differing indications of autoimmune disease. No characteristic profile of adverse events has been recognized, nor has an increase of nephrotoxicity if carefully monitoring in the first weeks after conversion was provided.     

The effect of cyclosporin on endothelin levels after orthotopic liver transplantation in rats

To assess the effects of cyclosporin (CyA) on endothelin-1 (ET-1) in rat liver allograft rejection, we evaluated ET-1 expression in samples obtained from BN(RT1ⁿ)-to-BN (group 1) rats, DA(RT1^a)-to-BN (group 2) rats, and DA-to-BN rats treated with 5 mg/kg per day of CyA (group 3). Serum and hepatic ET-1 levels, determined by a radioimmunoassay, remained unchanged in group 1. In group 2, the ET-1 levels peaked on postoperative day (POD) 5 in the liver at 344 ± 31.6 pg/g wet, and on POD 7 in the serum at 38.7 ± 13.1 pg/ml. In group 3, hepatic and renal ET-1 levels showed a progressive increase until POD 10, while serum ET-1 levels remained unchanged. In conclusion, acute rejection caused a temporary increase in the ET-1 level in both the serum and the liver in the early postoperative period what might have been caused by endothelial damage due to ongoing, acute rejection. CyA caused a time-dependent increase in the ET-1 level in both the liver and the kidney without an increase in the serum ET-1 level. The serum ET-1 level might have been affected by the clearance of ET from the liver or kidney. Received: 10 April 1996 Received after revision: 29 October 1996 Accepted: 12 November 1996     

The induction of operational tolerance is not prevented by simultaneous administration of cyclosporin A1

In this study, the effect of combining anti-CD4 monoclonal antibody (mAb) and cyclosporin (CyA) therapy at the time of transplantation was examined. A mouse cardiac allograft model was used. Anti-CD4 mAb administered perioperatively induces long-term survival. The addition of a short course of CyA given subcutaneously in a regimen of either a high-dose treatment or a standard dose treatment to the anti-CD4 mAb treatment protocol did not have a detrimental effect on graft survival. Despite having no significant effect on graft survival, the addition of CyA to the treatment protocol did result in a significant decrease in the level of IL-2 present in the hearts 7 days after transplantation. The decrease in IL-2 production was directly related to the presence of CyA in vivo. When CyA treatment was continued throughout the period during which unresponsiveness to the graft is induced by anti-CD4 mAb therapy, 50 % of the grafted hearts were rejected once the CyA was discontinued. In conclusion, the combined use of anti-CD4 mAb therapy and CyA did not have a negative effect on graft survival in this model when the two agents were used concurrently at the time of transplantation. Received: 2 October 1996 Received after revision: 31 January 1997 Accepted: 5 February 1997