Pharmacokinetics of the conventional and microemulsion formulations of cyclosporine in pancreas-kidney transplant recipients with gastroparesis

On the action of cyclosporine A, rapamycin and tacrolimus on M. avium including subspecies paratuberculosis

Background

Mycobacterium avium subspecies paratuberculosis (MAP) may be zoonotic. Recently the “immuno-modulators” methotrexate, azathioprine and 6-MP and the “anti-inflammatory” 5-ASA have been shown to inhibit MAP growth in vitro. We concluded that their most plausible mechanism of action is as antiMAP antibiotics. The “immunosuppressants” Cyclosporine A, Rapamycin and Tacrolimus (FK 506) treat a variety of “autoimmune” and “inflammatory” diseases. Rapamycin and Tacrolimus are macrolides. We hypothesized that their mode of action may simply be to inhibit MAP growth.

Methodology

The effect on radiometric MAP ¹⁴CO₂ growth kinetics of Cyclosporine A, Rapamycin and Tacrolimus on MAP cultured from humans (Dominic & UCF 4) or ruminants (ATCC 19698 & 303) and M. avium subspecies avium (ATCC 25291 & 101) are presented as “percent decrease in cumulative GI” (%-ΔcGI.)

Principal Findings

The positive control clofazimine has 99%-ΔcGI at 0.5 µg/ml (Dominic). Phthalimide, a negative control has no dose dependent inhibition on any strain. Against MAP there is dose dependent inhibition by the immunosuppressants. Cyclosporine has 97%-ΔcGI by 32 µg/ml (Dominic), Rapamycin has 74%-ΔcGI by 64 µg/ml (UCF 4) and Tacrolimus 43%-ΔcGI by 64 µg/ml (UCF 4)

Conclusions

We show heretofore-undescribed inhibition of MAP growth in vitro by “immunosuppressants;” the cyclic undecapeptide Cyclosporine A, and the macrolides Rapamycin and Tacrolimus. These data are compatible with our thesis that, unknowingly, the medical profession has been treating MAP infections since 1942 when 5-ASA and subsequently azathioprine, 6-MP and methotrexate were introduced in the therapy of some “autoimmune” and “inflammatory” diseases.

Pancreas and islet cell transplantation

Transplantation of the pancreas or islet cells constitutes surgical treatment for patients with type 1 diabetes mellitus. Pancreas transplantation is now an established procedure for the surgical treatment of diabetes mellitus. Islet cell transplantation has the potential to be the procedure of choice once it becomes more routine because of the minimal surgery involved. Included in this chapter are the pathophysiology of diabetes, rationale for transplantation, and the surgical procedure itself.

A compartmental pharmacokinetic model of cyclosporin and its predictive performance after Bayesian estimation in kidney and simultaneous pancreas-kidney transplant recipients

BACKGROUND

Therapeutic drug monitoring of cyclosporin A (CsA) is an obvious necessity because of its unpredictable absorption and narrow therapeutic window. The use of limited sampling models (LSMs) has improved the estimation of the systemic exposure [area under curve (AUC)] compared with C(0h) monitoring, but these equations are rigid and not reliable in patients with an abnormal absorption profile. We developed and validated a limited sampling (t=0, 2 and 3 h) strategy, based on a compartmental population pharmacokinetic (PK) model for CsA after kidney transplantation alone (KTA) and simultaneous pancreas-kidney transplant (SPKT) recipients, a group of patients with unpredictable absorption kinetics.

METHODS

A two-compartment model with lag time and first-order absorption was calculated using a PK software package from data of 20 KTA and SPKT recipients and validated prospectively in 20 KTA and 20 SPKT recipients. Calculated population PK parameters were individualized for each of the remaining 40 patients based on their CsA dosing and on one or a combination of measured CsA blood concentrations using the Bayesian fitting method. AUCs were calculated from individualized PK parameters. AUCs were also calculated using previously published LSMs. Relationships between AUCs calculated by the models and the 'golden standard' AUC (trapezoidal rule) were investigated by Pearson correlation test.

RESULTS AND CONCLUSIONS

A population two-compartment model is presented to reliably estimate the CsA AUC in KTA and SPKT recipients. The performance of the model to estimate the AUC is comparable to the performance of two published LSMs in KTA patients, but markedly better in SPKT patients. Combined with Bayesian fitting, the model is very flexible since sampling times are not rigid and can be varied as long as dosing and sampling times are recorded accurately. The model has already proven to be clinically useful and is currently used to further investigate CsA in an integrated pharmacokinetic/pharmacodynamic model.

The evaluation of the safety and tolerability of two formulations of cyclosporine: neoral and sandimmune. A meta-analysis

BACKGROUND

Neoral, a microemulsion formulation of cyclosporine, was approved for use in the United States in 1995. Many studies comparing Neoral and Sandimmune have been conducted, and although most state that Neoral is the superior cyclosporine formulation, results have failed to conclusively demonstrate this claim. The aim of this meta-analysis was to compare the safety and efficacy of Neoral and Sandimmune.

METHODS

Publications comparing the use of Neoral and Sandimmune were reviewed for demographic variables, adverse events, rejection incidence, graft losses, and serum creatinine. Neoral and Sandimmune were compared in all patients and in the following subgroups: (1) age (adult or pediatric), (2) transplant type (kidney, liver, or heart), (3) indication (de novo or stable), and (4) study design (randomized prospective trials versus nonrandomized, blinded versus open-labeled studies).

RESULTS

The rate of graft loss was similar when comparing Neoral and Sandimmune in all analyses. The incidence of rejection was lower in Neoral-treated de novo renal, liver, and cardiac transplants (P<0.05). There were significantly more adverse events in Sandimmune-treated de novo liver transplants than Neoral-treated de novo liver transplants (P<0.00001). When considering only randomized prospective trials, the incidence of rejection was lower in Neoral-treated de novo and stable patients (P<0.05). However, there were more adverse events in Neoral-treated stable patients (P<0.00001). When considering only blinded studies, there were more adverse events in Neoral-treated patients (P<0.05), whereas in open-labeled studies there was no difference in adverse events comparing Neoral and Sandimmune (P=NS).

CONCLUSIONS

Considering all published trials, the data seem to indicate that Neoral therapy is preferred because of a lower rejection incidence, with a trend toward less adverse events. However, when limiting the analysis to only randomized prospective trials, and specifically assessing blinded studies, the data become less clear. Neoral use was associated with more adverse events in blinded studies, and Sandimmune use was associated with more adverse events in open-labeled studies. Careful individual consideration must be given in choosing the best possible cyclosporine formulation.

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.

Drug delivery systems for cyclosporine: achievements and complications

The review deals with the preparation, properties, and analysis of different kinds of cyclosporine delivery systems, such as solid formulations, liposomes, emulsions and microemulsions and targeted cyclosporine formulations. The review points out a key role of delivery systems in increasing the therapeutic effectiveness of cyclosporine. Comparative studies of the prior marketed formulation, Sandimmune, with a new microemulsion formulation, Neoral, are discussed including some data on clinical development of Neoral.

Randomized comparison of triple therapy and antithymocyte globulin induction treatment after simultaneous pancreas-kidney transplantation

BACKGROUND

The incidence of acute rejection is considered to be higher after simultaneous pancreas-kidney (SPK) transplantation as compared to renal transplant alone. Therefore, the majority of SPK transplant recipients commonly receive a combination of cyclosporine (CsA) or tracolimus, and azathioprine or mycophenolic mofetyl, corticosteroids and/or antilymphocyte preparations. This study was designed to compare two immunosuppressive protocols for the prevention of acute rejection in patients undergoing SPK transplantation. The primary end-point was the incidence of acute rejection during the first 12 months after transplantation

METHODS

Fifty patients with type-I insulin-dependent diabetes and chronic renal failure were randomized to receive a triple drug immunosuppressive regimen including CsA, azathioprine and corticosteroids (N = 25), or the quadruple sequential combination of rabbit antithymocyte globulin (ATG) given for 10 days, azathioprine, corticosteroids and delayed CsA (N = 25). Maintenance immunosuppression (CsA and azathioprine, without corticosteroids) was similar in both arms.

RESULTS

The average follow-up was 36 months in both groups (range 9 to 60 months). No patient was excluded from the study. Although the percentage of patients with adverse events was higher in the ATG group (80 vs. 40%, P < 0.01), none of them resulted in premature discontinuation of the drug. Patients receiving ATG experienced a lower incidence (36% vs. 76%, P < 0.01) and number (13 vs. 29, P < 0.05) of acute renal rejection episodes. However, no difference was observed in patient, pancreas and kidney survival rates between groups. No case of isolated pancreas rejection was observed.

CONCLUSIONS

The quadruple sequential combination ATG, azathioprine, corticosteroid and CsA significantly reduced the one year incidence of acute renal rejection after SPK transplantation, compared to a triple immunosuppressive regimen.

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.