Pharmacodynamic studies of cyclosporine in marrow transplant recipients. A comparison of three assay methods

Bioavailability of Sandimmun® versus Sandimmun Neoral®: a meta-analysis of published studies

For the past 25 years, cyclosporine A (CyA) has played a pivotal role in transplant immunosuppressant therapy. From the availability of the 2 primary marketed formulations (Sandimmun® and Sandimmun Neoral®, Novartis), confusion has existed with regard to whether these two formulations are bioequivalent. Due to the underlying clinical relevance of this information, we therefore conducted a meta-analysis of all available comparative pharmacokinetic studies to assess whether the two different CyA formulations, Sandimmun® and Sandimmun Neoral®, can be considered bioequivalent. All clinical studies that compared the bioavailability of the 2 formulations in organ transplant recipients were considered for analysis. We searched computerised databases (Embase/Excerpta Medica and Medline/PubMed) from their inception to May 2010. Only studies with AUC values determined at 12 hours were considered for analysis. Relative bioavailability was calculated with 90 percent confidence intervals (CI) for Sandimmun® (test substance) versus Sandimmun Neoral® (reference substance) according to Schuirmann?s Two One-Sided Tests Procedure and the Classical Shortest CI. Homogeneity of data was tested using the Χ(2) test. Fifteen studies were considered for meta-analysis and none of these studies reported AUC values in the 80-125 percent range required for the bioequivalence of two formulations. The overall bioavailability for Sandimmun® versus the microemulsion formulation Sandimmun Neoral® was 76 percent, with upper CI limits lower than 80 percent in some cases. Mean AUC values for Sandimmun® were significantly lower than those for Sandimmun Neoral® (p<0.01). This study demonstrates that the 2 main cyclosporine formulations, Sandimmun® and Sandimmun Neoral®, cannot be considered bioequivalent.

GVHD prophylaxis using low-dose cyclosporine improves survival in leukaemic recipients of HLA-identical sibling transplants

Graft-versus-host disease (GVHD) prophylaxis of short duration (6 months) with low-dose cyclosporine A (CsA) starting at 1 mg/kg per day i.v. and four doses of methotrexate (MTX) were given to 171 consecutive leukaemic recipients of HLA-identical sibling transplants. In contrast, apart from MTX, retrospective controls received high-dose CsA, starting at 5-7.5 mg/kg per day i.v. and discontinued 1 yr post-transplant. In the low-dose CsA group, the probability of acute GVHD grades I-II (70% vs. 53%, P < 0.01), and chronic GVHD were increased (58% vs. 25%, P < 0.01), whereas the incidences of acute GVHD grades III-IV (9% vs. 5%, P = 0.62), and non-relapse mortality (20% vs. 22%, P = 0.58) were similar. Moreover, the probability of relapse was decreased (31% vs. 54%, P < 0.01), and both relapse-free (56% vs. 38%, P = 0.04) and overall survival (61% vs. 40%, P = 0.04) were markedly improved using the low-dose CsA regimen. In multivariate analyses, low-dose CsA was strongly associated with chronic GVHD [relative hazard (RH) 2.56, P < 0.01], which decreased the risk of relapse (RH 0.46, P < 0.01) and improved the probability of survival (RH 1.84, P < 0.01). In conclusion, a low-dose CsA regimen in leukaemic recipients of HLA-identical sibling transplants increases the rate of chronic GVHD, which seems to attenuate the risk of relapse, thereby improving patient survival owing to enhanced graft-versus-leukaemia effect.

Generic cyclosporine formulations: more open questions than answers

The introduction of cyclosporine (CsA) in clinical practice has significantly improved patient and allograft survival after organ transplantation. The new microemulsion CsA formulation, Neoral, has been associated with a more reproducible absorption and a better patient outcome as compared to the old formulation Sandimmune. Recently, several generic CsA formulations have been tested as bioequivalent to Neoral. Bioequivalence tests have been performed in selected groups of young, healthy male volunteers usually in single-dose studies, and then extended to completely different population, such as transplant recipients. However, growing body of evidence shows that CsA pharmacokinetics in healthy subjects is different from that of transplant patients, treated chronically with CsA. Therefore, converting patients from Neoral to the new generic formulations could be detrimental, exposing patients to increased risk of graft function deterioration and graft loss. Thus, more research and more accurate bioequivalence tests are required to address the unanswered problems dealing with the generic CsA formulations.

Drug therapy for acute graft-versus-host disease prophylaxis

The mechanisms of many immunosuppressive drugs have been defined, allowing for a rational approach to the use of these agents in GVHD prophylaxis. In addition to standard drugs such as methotrexate, cyclosporine, tacrolimus, and glucocorticoids, new agents-mycophenolate mofetil, tresperimus, rapamycin, basiliximab, and daclizumab-are now part of the immunosuppressive armamentarium. Improved understanding of tolerance has resulted in new approaches to prevention of GVHD. Anti-CD40L, CTLA-4-Ig, tresperimus, and rapamycin are agents that are being explored in this area and have shown impressive results in animal models. Currently, the standard therapy for acute GVHD prophylaxis in matched sibling transplants remains cyclosporine and methotrexate. Lower dose methotrexate, particularly in combination with tacrolimus, has shown good results in single arm studies with low toxicity, but this has not been tested in a randomized study. For unrelated donor transplants there is less GVHD when tacrolimus, rather than cyclosporine, is combined with methotrexate; there seems little reason to use cyclosporine in this setting. GVHD is still the major barrier to more widespread use of unrelated donor transplants and improved regimens are needed. In vivo T-cell depletion using Campath-1 or ATG is being used in high-risk patients. Data on its efficacy are so far anecdotal. Due to the variation in grading of GVHD between centers, randomized studies are needed to quantify the relative merits of different regimens, and participation in such studies is encouraged.

Plasminogen activator inhibitor (PAI-1) antigen levels in primary TTP and secondary TTP post-bone marrow transplantation

Our objectives were to measure and compare plasminogen activator inhibitor levels (PAI-1) in primary adult thrombotic thrombocytopenic purpura (TTP) and in secondary TTP associated with bone marrow transplantation (BMT)-TTP. PAI-1 antigen levels were measured by an enzyme linked immunosorbent assay on platelet poor plasma samples obtained from patients at the time of diagnosis of the TTP disorder and from a group of normal volunteers. The samples were frozen at -70 degrees C. Patients with TTP secondary to bone marrow transplantation had their grade determined by percentage fragmented cells and lactate dehydrogenase levels. The primary TTP samples were contributed by investigators in the multi-institutional North American TTP Group, and the bone marrow transplant samples were obtained from an adult bone marrow transplant program. Nineteen patients with adult TTP, and 47 patients with bone marrow transplant-TTP were evaluated. Of the latter, 14 had Grade 2, 13 had Grade 3, and 20 had Grade 4 BMT-TTP. PAI-1 levels were elevated compared to control volunteers in both primary adult TTP and BMT-TTP, P < 0.001. Levels did not differ from normal in Grade 2 BMT-TTP (median = 16 ng/ml; quartiles = 9-20). PAI-1 levels were similar in primary TTP (median = 32 ng/ml; quartiles = 25-51) and Grade 3 BMT-TTP (median = 35 ng/ml; quartiles = 19-48 ng/ml), P = 0.7. However, PAI-1 levels were significantly higher in Grade 4 BMT-TTP (median = 83 ng/ml; quartiles = 60-143) than Grade 3 BMT-TTP, and primary TTP, P < 0.001. PAI-1 levels are high in primary TTP and secondary bone marrow transplant-TTP (Grades 3-4). In contrast, normal levels are seen in Grade 2 BMT-TTP, which is a self-limited disorder. Therefore, high PAI-1 levels may contribute to hypofibrinolysis in the pathogenesis of primary TTP and of moderate to severe TTP (Grades 3-4) following bone marrow transplantation.

Plasma von Willebrand Factor Antigen (vWF:AG) and thrombomodulin (TM) levels in Adult Thrombotic Thrombocytopenic Purpura/Hemolytic Uremic Syndromes (TTP/HUS) and bone marrow transplant-associated thrombotic microangiopathy (BMT-TM)

Endothelial damage is thought to be a contributing factor in the pathogenesis of Thrombotic Thrombocytopenic Purpura/Hemolytic Uremic Syndromes (TTP/HUS). The present studies measured two markers of endothelial cell stimulation and/or activation [von Willebrand Factor (vWF:Ag) and thrombomodulin (TM)] in patients with TTP/HUS disorders and compared them to controls. The patient groups consisted of adults with TTP/HUS, with (n = 13) and without (n = 14) peak Cr levels >2.0 mg/dl. Additionally, 52 patients with Bone Marrow Transplant-associated Thrombotic Microangiopathy (BMT-TM) following allogeneic BMT were evaluated. Both vWF:Ag and TM were elevated in all patient groups compared to controls. TTP/HUS patients with peak Cr >2.0 mg/dl had higher TM levels (P < 0.001) than did those with peak Cr levels below 2 mg/dl. However, thrombomodulin/ creatinine (TM/Cr) ratios did not differ in these two groups nor did they differ from controls. BMT-TM pts had higher vWF:Ag levels and higher TM/Cr ratios than controls and TTP/ HUS, P < 0.001. The median TM/Cr ratio in BMT-TM was 91 (range = 34-229) compared to 38 (range = 29-50) in controls, P < 0.001 and 38 (range = 6 to 156) in TTP/HUS, P < 0.001. Additionally both TM (P < 0.001) and TM/Cr (P < 0.02) were higher in patients with Grades 3 and 4 BMT-TM compared to those with Grade 2 BMT-TM. These results suggest that endothelial cell activation occurs in TTP/HUS and BMT-TM. Since TM/Cr ratios were higher in BMT-TM compared to TTP/HUS, these findings suggest that the mechanism of elevated TM in BMT-TM cannot be explained solely by altered renal excretion. Taken together, these findings strongly indicate a role of endothelial cell damage in BMT-TM.

Apheresis in grade 4 bone marrow transplant associated thrombotic microangiopathy: a case series

Bone marrow transplant-associated thrombotic microangiopathy (BMT-TM) ranges in severity from a self-limited to a fatal disorder. There has been no specific therapy for this condition. We have previously described a clinical grading system for BMT-TM, based upon lactate dehydrogenase level (LDH) and percentage fragmented cells (FC) as follows: grade 0, normal or increases LDH and % FC < or = to 1.2%; grade 1, normal LDH and FC > or = to 1.3%; grade 2, increases LDH and FC = 1.3-4.8%; grade 3, increases LDH and FC = 4.9-9.6%; and grade 4, increases LDH and FC > or = to 9.7%. Patients with grade 4 BMT-TM usually have fulminant disease and generally succumb. This study summarizes results using a variety of apheresis procedures in a series of 16 patients with grade 4 BMT-TM. The apheresis procedures consisted of plasma exchange (with replacement with fresh frozen plasma or cryo-poor plasma), and protein A immunoadsorption (PAI). The PAI exchanges were not done concurrently with plasma exchange procedures. Fifteen patients had undergone an allogeneic BMT and the 16th patient had undergone an autologous peripheral blood stem cell transplant. Half showed hematologic improvement with a downstaging of their TM to grades 1-3. All non-responders died a median of 11 days following the onset of grade 4 BMT-TM. The median survival in the responders was significantly (P = 0.001) increased to 218 days with three responders surviving more than 400 days following the onset of this severe complication. These results suggest a role for apheresis in the treatment of this lethal complication. Nevertheless grade 4 BMT-TM represents a major complication of BMT; the median survival in this group of 16 patients with grade 4 BMT-TM was only 31 days.

Cyclosporine monitoring improves graft-versus-host disease prophylaxis after bone marrow transplantation

OBJECTIVE

The principal objective of this study was to determine whether a relationship exists between trough cyclosporine concentrations measured by HPLC and the development of acute graft-versus-host disease (GVHD) after allogeneic bone marrow transplantation.

DESIGN

A retrospective analysis of 59 consecutive human leukocyte antigen-matched bone marrow transplants. Patients received uniform GVHD prophylaxis with cyclosporine and methotrexate. Whole blood trough cyclosporine concentrations were measured at least twice weekly during hospitalization and weekly after discharge.

SETTING

A dedicated bone marrow transplant unit in an academic center.

MAIN OUTCOME MEASURES

The means of cyclosporine concentrations were assessed for each patient on a weekly basis during the first 50 days after transplant. These means were compared between patients developing grade 2-4 acute GVHD and patients without significant GVHD.

RESULTS

Eighteen patients developed acute GVHD at a median of 25 days after bone marrow transplant (range 10-50). There was no correlation between the development of GVHD and patient age, diagnosis, donor age, donor gender, donor-recipient gender mismatch, and time to neutrophil engraftment (> 1000 x 10(6) cells/L). Although mean weekly cyclosporine concentrations were consistently lower in patients developing acute GVHD, the difference in values compared with those of patients with GVHD was not statistically significant. Mean weekly cyclosporine concentrations at the time of neutrophil engraftment were statistically associated with the development of GVHD. Patients with GVHD had mean +/- SD concentrations of 174 +/- 69 ng/mL, significantly lower than 254 +/- 114 ng/mL in patients without GVHD. Furthermore, the rate of GVHD was 82 percent in patients with mean concentrations < 200 ng/mL at the time of neutrophil engraftment as compared with a rate of 34 percent in patients with concentrations > or = 200 ng/mL (relative risk = 2.4). Also, mean cyclosporine concentrations measured during the week of onset of GVHD were significantly lower compared with mean cyclosporine concentrations of all other patients at risk of GVHD during that week.

CONCLUSIONS

Cyclosporine concentrations are associated with the development of acute GVHD. Patients with HPLC whole blood concentrations < 200 ng/mL are at significantly higher risk of developing GVHD, particularly if these concentrations are observed during the week of neutrophil engraftment. More effective GVHD prophylaxis could be achieved by careful monitoring of cyclosporine concentrations after transplant.

Cyclosporin metabolism in transplant patients

The immunosuppressant cyclosporin, a cyclic undecapeptide, is metabolized to more than 30 metabolites. Cytochrome P450IIIA enzymes located in liver and small intestine are responsible for the biotransformation of cyclosporin and its metabolites and are the site of several drug interactions. It is still under discussion, whether the cyclosporin metabolites are involved in the immunosuppressive and/or toxic activities of cyclosporin. While isolated metabolites show not more than 10-20% of the activity of the mother compound in vitro, metabolite combinations have additive and synergistic effects. Isolated metabolites show no toxic effects in rat models while there is an association between metabolite blood concentrations and cyclosporin toxicity in several clinical studies. Possible mechanisms for the toxic effect of cyclosporin metabolites are covalent binding to macromolecules in liver and kidney, alteration of the cytochrome P450 pattern in liver and kidney, increased endothelin production in the kidney and synergistic effects of cyclosporin combinations on mesangial cells. Liver dysfunction leads to an alteration of the metabolite patterns and to increased concentrations of cyclosporin metabolites in blood. In conclusion there is evidence that cyclosporin metabolites may contribute to cyclosporin toxicity and high metabolite blood concentrations in patients should not be tolerated.