Neoral versus Sandimmun in kidney-pancreas transplantation

Cyclosporin Nanoparticulate Lipospheres for Oral Administration

Cyclosporin is a first line immunosuppressive drug used to prevent transplant rejection and to treat autoimmune diseases. It is a hydrophobic cyclic peptide built from nonmammalian amino acids with low oral bioavailability. The aim of this study was to develop an oral delivery system for cyclosporin A (CyA) and investigate the effect of composition and particle size of the CyA lipid nanoparticles (lipospheres) on the oral bioavailability of this drug. Dispersible concentrated oil formulations that upon mixing in water spontaneously form a nanodispersion were developed. The concentrated oil formulations were clear solutions composed of the drug, a solid triglyceride, a water miscible organic solvent, and a mixture of surfactants and emulsifiers. The activity of the formulated cyclosporin was determined in vitro following the effect on the proliferation of T cells. The oral bioavailability was determined on humans following the cyclosporin blood levels after oral intake of formulated cyclosporin. Cyclosporin dispersion systems resulting in particle size of 25 to 400 nm were prepared from acceptable pharmceutical components. The composition of the surfactants and emulsifiers, the lipid core component, and the amount and type of the water miscible organic solvent N-methylpyrrolidone (NMP) and alcohols had a strong effect on the particle size of the dispersions. All formulations were reproducible and stable at room temperature for at least 6 months, with full activity of cyclosporin retained. Human oral bioavaiability study indicated a correlation between the AUC and C(max) and the particle size of the dispersion. A C(max) of approximately 1300 ng/mL was found after 2 h of oral intake of four capsules, each loaded with 50 mg cyclosporin.

Vascularized pancreas allotransplantation--clinical indications and outcome

AIMS

This review examines the status of vascularized pancreas transplantation as a treatment for Type 1 diabetes mellitus (DM).

METHODS

The world literature, with a particular emphasis on data from the International Pancreas Transplant Registry (IPTR), is reviewed and interpreted particularly for clinical indications and outcome.

RESULTS

Over 9000 cases of vascularized pancreas transplant (VPT) have been registered, with insulin dependence approaching 82% at 1 year with 94% patient survival. The majority of transplants are simultaneous pancreas and kidney (SPK) transplants, with far fewer pancreas after kidney (PAK) or pancreas transplants alone (PTA). The success rates differ between the procedures but are generally improving as technical advances, improvements in immunosupression and greater experience are gained. The most obvious advantage is an improved quality of life (QoL) but there are risks associated with the procedure and with the immunosuppression. There is some evidence coming to light of a very slow beneficial effect on microvascular complications.

CONCLUSIONS

VPT is an attractive option to offer Type 1 DM patients who need or already have a renal allograft. Patients have to decide between the increased surgical risk and the risks of long-term immunosuppression and the benefits of improved QoL. In the absense of end-stage renal failure (ESRF) there is no justification for PTA, except where the diabetes itself poses a greater risk to life than the transplantation procedure.

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.

Review of immunosuppressive usage in pancreas transplantation

Throughout 1997, nearly 10,000 pancreas transplants have been performed worldwide, with 88% being simultaneous kidney transplants (SKPT). The current 1 yr patient survival rate exceeds 90% and pancreas graft survival (complete insulin independence) rate exceeds 80% for SKPT, 70% for sequential pancreas after kidney transplant (PAKT), and 65% for pancreas transplant alone (PTA). According to registry data, rejection accounts for 32% of graft failures in the first year after pancreas transplantation. However, improvements are expected to continue with the evolution of treatment protocols. Most pancreas transplant centers employ quadruple drug immunosuppression with anti-lymphocyte induction with either a monoclonal or polyclonal antibody agent. In recent years, there has been an overall decline in the use of antibody induction therapy from 90% during the period 1987-1993 to 83% of pancreas transplants performed during 1994-1997. Maintenance immunosuppression is triple therapy consisting of a calcineurin inhibitor (cyclosporine or tacrolimus), corticosteroids, and an anti-metabolite (AZA or MMF). Prior to 1995, nearly all pancreas transplant recipients were managed with Sandimmune. In the last 2 yr, tacrolimus-based therapy has been used in approximately 20% of cases and a new microemulsion formulation of cyclosporine (Neoral) has replaced Sandimmune in contemporary post-transplant immunosuppression. In addition, MMF is replacing AZA as part of the standard immunosuppressive regimen after pancreas transplantation. At present, a number of centers are conducting various trials with new drug combinations including either Neoral or tacrolimus in combination with steroids and MMF with or without antibody induction therapy. From 1994 to 1997, the 1 yr rates of immunologic graft loss have decreased to 2% after SKPT, 9% after PAKT, and 16% after PTA. The current array of new immunosuppressive agents are providing more effective control of rejection and permitting solitary pancreas transplantation to become an accepted treatment option in diabetic patients without advanced complications. The apparent potency of new drug combinations has also resulted in a resurgence of interest in steroid withdrawal. Immunosuppressive strategies will continue to evolve in order to achieve effective control of rejection while minimizing injury to the allograft and risk to the patient. In addition, new regimens must not only address the issue of specific drug toxicities but also long-term economic, metabolic, and quality of life outcomes. Pancreas transplantation will remain an important alternative in the treatment of diabetic patients until other strategies are developed that can provide equal glycemic control with less immunosuppression and overall morbidity.

Reduced intrapatient variability of cyclosporine pharmacokinetics in renal transplant recipients switched from oral Sandimmune to Neoral

Sixty-six renal transplant patients maintained on Sandimmune, the traditional formulation of cyclosporine, participated in an open-label, sequential trial to compare intrapatient variability in drug exposure before and after a switch to Neoral. Three 12-hour cyclosporine pharmacokinetic profiles were obtained over approximately 6 weeks while patients were receiving Sandimmune. Patients were then switched to Neoral, with the dose adjusted as necessary to maintain target trough blood cyclosporine concentrations. At approximately 4 and 6 weeks postconversion, 2 additional pharmacokinetic profiles were obtained. Key pharmacokinetic variables analyzed were area under the concentration-time curve (AUC), maximum concentration (Cmax), and predose trough concentration (C0). Intrapatient variability in drug exposure for dose-normalized mean AUC, Cmax, and C0 was significantly reduced with Neoral, with 50 (76%), 57 (86%), and 45 (68%) patients experiencing reduced variability in AUC, Cmax, and C0, respectively (P < 0.001). Additionally, the total exposure to cyclosporine was more predictable from the trough level of cyclosporine with Neoral; the relationship between AUC and C0 was 0.81 for Neoral at both pharmacokinetic profiling time points but ranged from 0.49 to 0.69 for the 3 Sandimmune time points. The large reductions in intrapatient variability of pharmacokinetic variables for cyclosporine provided by Neoral indicate an improvement in the consistency of drug exposure, which may translate into important clinical benefits.

Immunosuppression in pancreas transplantation: progress, problems and perspective

Through 1997, over 10,000 pancreas transplants have been performed world-wide, with 88% being simultaneous kidney-pancreas transplants (SKPTs). Current 1-year patient survival exceeds 90% and pancreas graft survival (complete insulin independence) exceeds 80% for SKPT, 70% for sequential pancreas after kidney transplant (PAKT), and 65% for pancreas transplant alone (PTA). According to Registry data, rejection accounts for 32% of graft failures in the first year after pancreas transplantation. However, improving outcomes are expected to continue with the evolution of treatment protocols. Most pancreas transplant centres employ quadruple drug immunosuppression with anti-lymphocyte induction, using either a monoclonal or polyclonal antibody agent. In recent years, there has been an overall decline in the use of antibody-induction therapy from 90% during 1987-93, to 83% of pancreas transplants performed during 1994-97. Maintenance immunosuppression is triple therapy consisting of a calcineurin inhibitor (cyclosporine or tacrolimus), corticosteroids, and an anti-metabolite such as azathioprine (AZA) or mycophenolate mofetil (MMF). Prior to 1995, nearly all pancreas transplant recipients were managed with Sandimmune. Since 1986, tacrolimus-based therapy has been used in approximately 20% of cases, and a new microemulsion formulation of cyclosporine (Neoral) has replaced Sandimmune in contemporary post-transplant immunosuppression. In addition, MMF is replacing AZA as part of the standard immunosuppressive regimen following pancreas transplantation. At present, a number of centres are conducting various trials with new drug combinations including either Neoral or tacrolimus in combination with steroids and MMF, with or without antibody-induction therapy. From 1994 to 1997, the 1-year rates of immunologic graft loss have decreased to 2% after SKPT, 9% after PAKT, and 16% after PTA. The current array of new immunosuppressive agents are providing more effective control of rejection and permitting solitary pancreas transplantation to become an accepted treatment option in diabetic patients without advanced complications. The apparent potency of new drug combinations has also resulted in a resurgence of interest in steroid withdrawal. Immunosuppressive strategies will continue to evolve to achieve effective control of rejection while minimizing injury to the allograft and risk to the patient. In addition, new regimens must not only address the issue of specific drug toxicities, but also long-term economic, metabolic, and quality of life outcomes. Pancreas transplantation will remain an important alternative in the treatment of diabetic patients until other strategies are developed that can provide equal glycaemic control with less immunosuppression and overall morbidity.