The US multicenter double-blind, randomized, phase III trial of thymoglobulin versus atgam in the treatment of acute graft rejection episodes following renal transplantation: rationale for study design

In this study intended to establish equivalence between two antibody therapies for acute rejection in kidney transplant recipients, it was important to develop a rigorous protocol. Assurance of the presence of acute rejection was imperative. Therefore, due to the lack of literature support for clinical assessment of renal dysfunction, histologic diagnosis of acute rejection was required for enrollment in the study. Likewise, supportive literature for a correlation between response to anti-rejection therapy and the severity of rejection lead to the decision that the study should be stratified by a measurement of rejection severity for which Banff criteria were used. Finally, quantification of the response to therapy was also measured against the available literature and a large, newly developed international database of kidney transplant rejection episodes (the Efficacy Endpoints database) where serum creatinine, expressed as a percentage of the baseline level at the time of rejection was shown to be the most effective, available clinical marker of rejection response. Therefore, the US Multicenter Phase III Trial for comparing Thymoglobulin to Atgam in the treatment of acute rejection exhibits a unique and detailed study design that could be implemented in future trials as well as in clinical practice to improve assessment of outcomes.

The clinical and economic potential of cyclosporin drug interactions

The introduction of cyclosporin significantly improved solid organ transplantation outcomes. However, the costs associated with immunosuppressive therapy increased from approximately $US1000 to $US2000 per patient per year with azathioprine (AZA) and prednisone to $US5000 to $US8000 per patient per year with the addition of cyclosporin (1997 values). Because of the financial demands placed on medical care in the current era, research has been directed towards developing drug combinations which potentiate the therapeutic effect of cyclosporin whereby reducing the amount of drug administered and consequently the costs of long term immunosuppressive therapy. To date, many drugs that interact with cyclosporin have been recognised. Included in this list are the azole antifungal drugs, ketoconazole, fluconazole and itraconazole; the calcium channel blockers, diltiazem, verapamil and nicardipine; and the macrolide antibacterials, erythromycin and related compounds. Although all of these drugs increase cyclosporin drug concentrations when used concomitantly, ketoconazole and diltiazem appear to be the best candidates on the basis of reducing financial pressures of chronic immunosuppressive therapy without sacrificing patients' well-being. Studies of various regimens involving the combined use of ketoconazole and cyclosporin have shown that cyclosporin dosages can be reduced by approximately 70 to 85% while maintaining therapeutic blood concentrations in renal, cardiac and liver transplant recipients. The calcium channel blocker, diltiazem, allows a decrease in cyclosporin dosage by approximately 30 to 50% in this same group of organ transplant patients. These reductions in cyclosporin dosage have been achieved with no reported severe adverse effects that would discourage the use of these agents concurrently in practice. The combined use of cyclosporin and ketoconazole or diltiazem could reduce medication costs by approximately $US915 to $US3000 per year per patient. If all patients treated with cyclosporin are considered, these combinations could reduce medication costs by hundreds of millions of dollars per year in the US alone. While these are promising approaches, further characterisation of these drug interactions is necessary before this practice is adopted as standard protocol worldwide. The objective of this paper is to review the clinical and economic potential of cyclosporin-sparing agents such as the azole antifungal drugs and calcium channel blockers in an attempt to decrease the costs associated with this expensive immunosuppressive agent.

The cost-effectiveness of transplantation with expanded donor kidneys

Transplantation with EDKs is a cost-effective therapy for ESRD as compared to hemodialysis across a variety of clinical and financial scenarios. In many cases the costs of pursuing transplantation with these donors will exceed hospital reimbursement for the procedure, providing a financial disincentive to pursuing a clearly cost-effective therapy.

Development of Sang-35: a cyclosporine formulation bioequivalent to Neoral

During a research program, SangStat Medical Corporation developed more than 270 oral cyclosporine formulations. On the basis of animal and clinical trials, Sang-35 was chosen for clinical development, and bioequivalence with the cyclosporine microemulsion Neoral was established. In a cross-over study involving 36 healthy male volunteers, single 500 mg cyclosporine doses of Sang-35 (AUC0-infinity: 13,900 +/- 2470 micrograms.h.L-1, mean +/- standard deviation (SD)) and of Neoral (AUC0-infinity: 14,000 +/- 2900 micrograms.h.L-1) resulted in equal areas-under-the-time-concentration curve (AUC0-infinity). Sang-35 and Neoral were also bioequivalent in healthy male subjects after high-fat meals as well as in female and African-American subjects. In stable kidney transplant patients (n = 12) receiving a mean (+/- SD) cyclosporine dose of mg/d (3.6 +/- 1.6 mg/kg/d), AUC0-12 h after Sang-35 was, as expected, significantly higher than that after Sandimmune (4550 +/- 1858 vs 3468 +/- 1402 micrograms.h.L-1, p < 0.01). Sang-35 and Neoral resulted in equivalent cyclosporine AUC0-12 h values (4120 +/- 1508 and 4377 +/- 1579 micrograms.h.L-1, respectively) in stable kidney transplant patients (dose: 293 +/- 114 mg/d or 3.7 +/- 1.5 mg/kg/d, n = 32). In an additional study, 42 stable kidney graft patients were switched from Sandimmune to Sang-35. Based on a conversion strategy targeting AUC equivalence, only one dose adjustment was required in 55% of the patients, and 95% of patients (40 of 42) needed three or fewer dose adjustments. The mean Sang-35 dose was 7% lower than the mean Sandimmune dose. During the studies, Sang-35 and Neoral exhibited similar safety and tolerability profiles. It is concluded that Sang-35 and Neoral are bioequivalent and that patients can safely and easily be switched from Neoral or, in combination with dose adjustment, from Sandimmune to Sang-35.

Use of tacrolimus eliminates acute rejection as a major complication following simultaneous kidney and pancreas transplantation

This retrospective study illustrates the efficacy of tracrolimus-based immunosuppression following simultaneous kidney and pancreas transplantation. Between March 1995 and December 1996, 24 simultaneous kidney and pancreas transplant recipients received tacrolimus-based maintenance immunosuppression. All patients received sequential therapy with an antilymphocyte agent, azathioprine, prednisone and tacrolimus. The dose of tacrolimus was adjusted to achieve a whole blood trough level of 8-15 ng/mL (IMx). The mean follow-up was 25 months with a median of 26 months (range 12-33 months). A rise in serum creatinine of > 20% over baseline was investigated with a renal biopsy, after mechanical causes for renal dysfunction had been excluded. Mean serum creatinine concentrations at 3, 6, 12, 18 and 24 months post-transplantation were 1.1, 1.2, 1.3, 1.3 and 1.3 mg/dL respectively. The blood glucose concentrations at the corresponding time period were 115, 94, 95, 93 and 95 mg/dL. Four pancreas allografts were lost (three in the immediate post-transplant period due to thrombosis, and one following iliac artery repair for aneurysm). Transient hyperglycemia requiring treatment was seen in 3 patients. There were four (17%) acute rejection episodes--one of the pancreas allograft alone and three involving the kidney. At a mean follow-up of 25 months, the patient survival and renal allograft survival were 100%, with pancreas allograft survival rate of 78.4% (Kaplan-Meier analysis). Nine (37.5%) patients had evidence of tacrolimus toxicity on renal histology. In conclusion, tacrolimus-based maintenance immunosuppression is associated with stable renal and pancreas allograft function, with freedom from acute rejection in 83% of patients.

Early operative intervention for urologic complications of kidney-pancreas transplantation

Bladder drainage of exocrine secretions during pancreas transplantation can be associated with significant complications. We present a proactive approach to these complications consisting of early cystoenteric conversion (CEC). Although 81 patients underwent pancreas transplant between March 1985 and May 1995; 26 (32%) required CEC. Complications presented as urine leaks, other complications, and refractory metabolic acidosis. There were 13 patients who presented with a urine leak: 12 with acute abdominal pain, and 1 asymptomatic. Serum amylase and creatinine rose a mean of 823 IU and 0.61 mg/dl, respectively. The interval to CEC ranged from 2 to 45 months. One patient died of fungal sepsis. Postoperative complications included duodenojejunal anastomotic bleed (n = 1), negative relaparotomy (n = 1), myocardial infarction (n = 1), graft pancreatitis (n = 1), and wound infection (n = 1). Twelve patients presented with other complications: three women with cystitis (n = 2) or hematuria (n = 1), and nine men with urethritis (n = 6), scrotal edema (n = 2), or dysuria (n = 1), The interval to conversion ranged from 1 to 108 months. There were no deaths. One patient required relaparotomy for anastomotic bleed. One patient was converted because of refractory metabolic acidosis. Admissions and inpatient days were significantly reduced. Overall mortality was 3.8%, morbidity 23.1%, and graft salvage rate 96.1%. Leak-associated mortality was 7.7%, morbidity 38.5%, and graft salvage rate 92.3%. For other complications the mortality was 0, morbidity 7.7%, and graft salvage rate 100%. CEC is a safe, effective treatment for urologic complications of pancreas transplantation. Morbidity and mortality were acceptable; admissions and hospital days were decreased. Early CEC results in superior outcomes and improved quality of life. It is preferable to nondefinitive measures for management of urologic complications of pancreatic transplantation.

Improved cyclosporine pharmacokinetics in maintenance renal transplant recipients converted to cyclosporine for microemulsion

BACKGROUND

Variability in cyclosporine drug exposure of > or = 20% has been shown to be a risk factor for the development of chronic renal allograft rejection. We tested the hypothesis that a cyclosporine microemulsion (CsA-ME) would result in reduced variability in stable maintenance renal transplant patients when compared with the original formulation of cyclosporine (CsA).

METHODS

The 31 maintenance renal transplant recipients were part of a multicenter, randomized, double-blind, prospective study comparing the CsA formulation with the CsA-ME formulation. Pharmacokinetics analyses were performed at two centers 1, 4, 12, and 52 weeks after patients were randomized to continue receiving CsA or to convert to CsA-ME.

RESULTS

The means of the week 1-, 4-, and 12-week areas under the concentration-time curves (AUC), and Cmax were significantly higher and the Tmax was significantly shorter in those patients converted to CsA-ME than in those remaining on CsA. There was no correlation between change in AUC after conversion and change in serum creatinine. The coefficient of variation values for dose-adjusted AUC, expressed as a percentage (%CVAUC), were lower in CsA-ME patients than CsA patients after both 12 and 52 weeks. Over the initial 12 weeks. %CVAUC values of < or = 20% were seen in a significantly greater proportion of CsA-ME patients than CsA patients.

CONCLUSIONS

Conversion of maintenance renal transplant recipients from CsA to CsA-ME resulted in improved absorption of cyclosporine. The CsA-ME formulation resulted in long-term reduction in the variability of cyclosporine exposure and more consistent pharmacokinetics.

Results of the double-blind, randomized, multicenter, phase III clinical trial of Thymoglobulin versus Atgam in the treatment of acute graft rejection episodes after renal transplantation

BACKGROUND

Thymoglobulin, a rabbit anti-human thymocyte globulin, was compared with Atgam, a horse anti-human thymocyte globulin for the treatment of acute rejection after renal transplantation.

METHODS

A multicenter, double-blind, randomized trial with enrollment stratification based on standardized histology (Banff grading) was conducted. Subjects received 7-14 days of Thymoglobulin (1.5 mg/kg/ day) or Atgam (15 mg/kg/day). The primary end point was rejection reversal (return of serum creatinine level to or below the day 0 baseline value).

RESULTS

A total of 163 patients were enrolled at 25 transplant centers in the United States. No differences in demographics or transplant characteristics were noted. Intent-to-treat analysis demonstrated that Thymoglobulin had a higher rejection reversal rate than Atgam (88% versus 76%, P=0.027, primary end point). Day 30 graft survival rates (Thymoglobulin 94% and Atgam 90%, P=0.17), day 30 serum creatinine levels as a percentage of baseline (Thymoglobulin 72% and Atgam 80%; P=0.43), and improvement in posttreatment biopsy results (Thymoglobulin 65% and Atgam 50%; P=0.15) were not statistically different. T-cell depletion was maintained more effectively with Thymoglobulin than Atgam both at the end of therapy (P=0.001) and at day 30 (P=0.016). Recurrent rejection, at 90 days after therapy, occurred less frequently with Thymoglobulin (17%) versus Atgam (36%) (P=0.011). A similar incidence of adverse events, post-therapy infections, and 1-year patient and graft survival rates were observed with both treatments.

CONCLUSIONS

Thymoglobulin was found to be superior to Atgam in reversing acute rejection and preventing recurrent rejection after therapy in renal transplant recipients.