Efficacy and safety of sirolimus in lymphangioleiomyomatosis

BACKGROUND

Lymphangioleiomyomatosis (LAM) is a progressive, cystic lung disease in women; it is associated with inappropriate activation of mammalian target of rapamycin (mTOR) signaling, which regulates cellular growth and lymphangiogenesis. Sirolimus (also called rapamycin) inhibits mTOR and has shown promise in phase 1-2 trials involving patients with LAM.

METHODS

We conducted a two-stage trial of sirolimus involving 89 patients with LAM who had moderate lung impairment--a 12-month randomized, double-blind comparison of sirolimus with placebo, followed by a 12-month observation period. The primary end point was the difference between the groups in the rate of change (slope) in forced expiratory volume in 1 second (FEV(1)).

RESULTS

During the treatment period, the FEV(1) slope was -12±2 ml per month in the placebo group (43 patients) and 1±2 ml per month in the sirolimus group (46 patients) (P<0.001). The absolute between-group difference in the mean change in FEV(1) during the treatment period was 153 ml, or approximately 11% of the mean FEV(1) at enrollment. As compared with the placebo group, the sirolimus group had improvement from baseline to 12 months in measures of forced vital capacity, functional residual capacity, serum vascular endothelial growth factor D (VEGF-D), and quality of life and functional performance. There was no significant between-group difference in this interval in the change in 6-minute walk distance or diffusing capacity of the lung for carbon monoxide. After discontinuation of sirolimus, the decline in lung function resumed in the sirolimus group and paralleled that in the placebo group. Adverse events were more common with sirolimus, but the frequency of serious adverse events did not differ significantly between the groups.

CONCLUSIONS

In patients with LAM, sirolimus stabilized lung function, reduced serum VEGF-D levels, and was associated with a reduction in symptoms and improvement in quality of life. Therapy with sirolimus may be useful in selected patients with LAM. (Funded by the National Institutes of Health and others; MILES ClinicalTrials.gov number, NCT00414648.).

Rapamycin slows aging in mice

Rapamycin increases lifespan in mice, but whether this represents merely inhibition of lethal neoplastic diseases, or an overall slowing in multiple aspects of aging is currently unclear. We report here that many forms of age-dependent change, including alterations in heart, liver, adrenal glands, endometrium, and tendon, as well as age-dependent decline in spontaneous activity, occur more slowly in rapamycin-treated mice, suggesting strongly that rapamycin retards multiple aspects of aging in mice, in addition to any beneficial effects it may have on neoplastic disease. We also note, however, that mice treated with rapamycin starting at 9 months of age have significantly higher incidence of testicular degeneration and cataracts; harmful effects of this kind will guide further studies on timing, dosage, and tissue-specific actions of rapamycin relevant to the development of clinically useful inhibitors of TOR action.

Use of rapamycin slows progression of cardiac transplantation vasculopathy

BACKGROUND

Cardiac transplantation vasculopathy is the leading cause of late death in heart transplantation recipients. Rapamycin is an immunosuppressant drug with potent antiproliferative and antimigratory effects. We investigated whether rapamycin could prevent progression of graft vasculopathy in 46 patients (age, 54+/-10 years; 4.3+/-2.3 years after transplantation) with severe disease.

METHODS AND RESULTS

At annual cardiac catheterization, patients were randomly assigned to treatment with rapamycin (n=22) versus continued current immunosuppression (n=24). Clinical characteristics including recipient age and sex, underlying cause of congestive heart failure, donor age and sex, and ischemic time were recorded. Cardiac catheterization was graded with the use of a semiquantitative scale and repeated annually. Clinically significant adverse events were defined as death, need for angioplasty or bypass surgery, myocardial infarction, and a >25% worsening of the catheterization score. These events were monitored as primary study end points. Anti-HLA class I and II antibody production and lymphocyte growth assays were measured with each biopsy. Patients selected for rapamycin had azathioprine or mycophenolate mofetil discontinued and were given rapamycin. Outcomes were compared by means of log-rank analysis. There were no significant differences in baseline characteristics. Duration of follow-up was comparable (rapamycin, 689+/-261; control, 630+/-207 days; NS). In the rapamycin group, 3 patients reached primary end points versus 14 patients in the control group (P<0.001). There was no difference in baseline or subsequent anti-HLA class I or II antibody production.

CONCLUSIONS

In this patient cohort with cardiac vasculopathy, treatment with rapamycin slowed disease progression probably by its antiproliferative and antimigratory effects.

Predictors of success in conversion from calcineurin inhibitor to sirolimus in chronic allograft dysfunction

Chronic allograft dysfunction (CAD) is a major cause of graft loss in long-term kidney transplant recipients. To identify predictors of successful conversion from calcineurin inhibitor (CNI) to sirolimus (SRL) we investigated 59 renal transplant patients with CAD without histological signs of acute rejection. They received 12-15 mg SRL once, then 4-5 mg/day, target trough level 8-12 ng/mL. CNI dose was reduced by 50% simultaneously, and withdrawn at 1-2 months. Concomitant immunosuppression remained unchanged. After 1 year patient survival was 100% and graft survival 92%. In responders (54%) creatinine improved (2.75 +/- 0.75 to 2.22 +/- 0.64 mg/dL; p < 0.01). In nonresponders (46%) creatinine deteriorated (3.15 +/- 1.02 to 4.44 +/- 1.60 mg/dL; p < 0.01). Baseline renal function did not differ, however, baseline proteinuria (519 +/- 516 vs. 1532 +/- 867 mg/day, p < 0.01), histological grade of chronic allograft nephropathy (CAN) (1.2 +/- 0.5 vs. 1.9 +/- 0.6; p < 0.01), grade of vascular fibrous intimal thickening (1.2 +/- 0.7 vs. 1.7 +/- 0.7; p = 0.048) and number of acute rejections before conversion (0.73 +/- 0.69 vs. 1.27 +/- 0.96; p < 0.05) differed significantly between responders and nonresponders. In a multivariate analysis low proteinuria was the only independent variable. Proteinuria below 800 mg/day has a positive predictive value of 90%. Proteinuria at conversion below 800 mg/day is the only independent predictor for positive outcome in conversion from CNI to SRL in CAD.

Specific binding to intracellular proteins determines arterial transport properties for rapamycin and paclitaxel

Endovascular drug-eluting stents have changed the practice of medicine, and yet it is unclear how they so dramatically reduce restenosis and how to distinguish between the different formulations available. Biological drug potency is not the sole determinant of biological effect. Physicochemical drug properties also play important roles. Historically, two classes of therapeutic compounds emerged: hydrophobic drugs, which are retained within tissue and have dramatic effects, and hydrophilic drugs, which are rapidly cleared and ineffective. Researchers are now questioning whether individual properties of different drugs beyond lipid avidity can further distinguish arterial transport and distribution. In bovine internal carotid segments, tissue-loading profiles for hydrophobic paclitaxel and rapamycin are indistinguishable, reaching load steady state after 2 days. Hydrophilic dextran reaches equilibrium in several hours at levels no higher than surrounding solution concentrations. Both paclitaxel and rapamycin bind to the artery at 30-40 times bulk concentration. Competitive binding assays confirm binding to specific tissue elements. Most importantly, transmural drug distribution profiles are markedly different for the two compounds, reflecting, perhaps, different modes of binding. Rapamycin, which binds specifically to FKBP12 binding protein, distributes evenly through the artery, whereas paclitaxel, which binds specifically to microtubules, remains primarily in the subintimal space. The data demonstrate that binding of rapamycin and paclitaxel to specific intracellular proteins plays an essential role in determining arterial transport and distribution and in distinguishing one compound from another. These results offer further insight into the mechanism of local drug delivery and the specific use of existing drug-eluting stent formulations.

Therapeutic drug monitoring of sirolimus: correlations with efficacy and toxicity

We sought to examine the potential benefits of therapeutic drug monitoring of sirolimus, a potent immunosuppressive agent that displays a pleiotropic array of side effects.

METHODS

A high-performance liquid chromatography (LC) procedure combined with ultraviolet detection (UV) was used to measure serial concentrations of parent compound sirolimus in 150 renal transplant recipients over a period of 4 yr. Drug concentrations in whole blood at trough time, as well as within pharmacokinetic profiles, were correlated with clinical events using contingency tables, logistic regression analysis, and receiver operating characteristic (ROC) curves.

RESULTS

The LC/UV method showed an excellent correlation with detection of LC-resolved components by tandem mass spectrometry, demonstrating that the LC/UV method selectively detected parent compound. Sirolimus displayed the characteristics of a critical-dose drug: Its concentration could not be predicted by a standard body or demographic measure, or by dose, and it showed high degrees of intra- and inter-individual variability. However, there was a good correlation between trough and area-under-the-curve measurements. There was a significant association between trough values expressed as either observed ( < 5 ng/mL) or dose-corrected parameter ( < 1.7 ng/mL per mg administered drug) and the occurrence and severity of acute rejection episodes - despite the low overall incidence of 23 episodes among the cohort of 150 patients. Similarly, ROC functions showed a correlation of the occurrence of hypertriglyceridemia, thrombocytopenia, and leukopenia, but not hypercholesterolemia, with trough concentrations above 15 ng/mL.

CONCLUSION

Due to its behavior as a critical-dose drug, therapeutic monitoring to measure sirolimus concentrations by a LC/UV method may provide clinicians with a tool to optimize outcomes.

Elevated portal vein drug levels of sirolimus and tacrolimus in islet transplant recipients: local immunosuppression or islet toxicity?

The recent success of islet transplantation using the Edmonton protocol involved the use of sirolimus, tacrolimus, and daclizumab for immunosuppression. Islets were infused into the portal circulation after transhepatic access. This protocol provided a unique opportunity to measure sirolimus and tacrolimus levels from the portal vein and compare them to systemic venous levels. A total of 11 portal venous samples with a corresponding peripheral venous sample were obtained from patients undergoing a first or second islet infusion and medication levels were obtained on both types of specimens. The portal-to-systemic drug level ratio ranged from 0.95 to 2.71 for sirolimus and 1.0 to 3.12 for tacrolimus. Given the potential toxicity of these agents to islets, the findings in this study may have implications for designing the next generation of immunosuppressive protocols for islet transplantation.

Sirolimus, tacrolimus, and low-dose methotrexate for graft-versus-host disease prophylaxis in mismatched related donor or unrelated donor transplantation

We studied the feasibility and activity of adding sirolimus to tacrolimus and low-dose methotrexate as graft-versus-host disease (GVHD) prophylaxis in recipients of alternative donor transplants. Forty-one patients with hematologic malignancies were conditioned with cyclophosphamide and total body irradiation. Marrow stem cells were from an HLA-A, -B, and -DR compatible, unrelated donor (n = 26, 68%), from a 5 of 6 antigen-matched unrelated donor (n = 8, 20%), or from a 5 of 6 antigen-matched family member (n = 5, 12%). Therapeutic serum levels of sirolimus were attained in most patients. All evaluable patients engrafted. An absolute neutrophil count of 500/microL was achieved on day +18 (range, 11-32 days). Sustained platelet counts of more than 20 000/ microL were attained on day +29 (range, 14-98 days). Grades 0-I acute GVHD occurred in 75% of patients. Grades II, III, and IV acute GVHD occurred in 13%, 8%, and 5%, respectively (total grades II-IV GVHD, 26%). Median survival is 366 days (95% CI 185, not estimable) and actuarial survival at 1 year is 52%. Oral sirolimus is tolerable, adequate blood levels are achievable, and there is a low rate of acute GVHD compared with historical data in this high-risk population. This novel agent is worthy of further study in allogeneic transplantation.

Airway anastomotic dehiscence associated with use of sirolimus immediately after lung transplantation

GOAL

The goal of this study was to assess the efficacy of sirolimus in lung-transplant recipients.

METHODS

The study was designed as a single center, consecutive case study of lung-transplant recipients treated with sirolimus, tacrolimus, and prednisone. All study subjects also received an HMG-CoA reductase inhibitor, and prophylaxis for cytomegalovirus and Pneumocystis carinii.

RESULTS

A total of 15 subjects were enrolled in the study. Within 6 months, significant airway complications occurred in four subjects, three of whom died. At that point, the investigators terminated enrollment in the study. The study population was compared retrospectively with a group of 83 consecutive lung recipients treated with cyclosporine (n=64) or tacrolimus (n=19), mycophenolate mofetil, and prednisone. This confirmed an increased incidence of airway dehiscence and reduced survival in the sirolimus-treated patients. Sirolimus-treated patients had a low incidence of acute rejection. No significant differences were noted in the incidence of bacterial or fungal bronchopulmonary infections.

CONCLUSIONS

We observed an unexpectedly high incidence of postoperative airway dehiscence in lung-transplant recipients treated with sirolimus, in combination with tacrolimus, prednisone, and an HMG-CoA inhibitor. Further studies will be needed to determine the safety and efficacy of using sirolimus after complete airway healing has occurred.

A randomized long-term trial of tacrolimus and sirolimus versus tacrolimus and mycophenolate mofetil versus cyclosporine (NEORAL) and sirolimus in renal transplantation. I. Drug interactions and rejection at one year

BACKGROUND

To reduce long-term nephrotoxic calcineurin inhibitor dosage, adjunctive sirolimus or mycophenolate mofetil (MMF) was used in a 150-patient, randomized, three-armed trial in cadaveric or human leukocyte antigen non-identical living-donor first renal transplant recipients (n=50/group).

METHODS

Group A received tacrolimus and sirolimus. Target tacrolimus trough levels postoperatively were 10, 8, and 6 ng/mL at 1 month, 6 months, and 1 year, respectively. Group B received tacrolimus and MMF. Target tacrolimus trough levels were 10 and 8 ng/mL at 1 month and 1 year, with a targeted dose of MMF of 1 g twice daily. Group C received cyclosporine A (CsA) (Neoral, Novartis, Basel, Switzerland) and sirolimus with target CsA trough levels of 225 and 175 ng/mL at 1 month and 1 year. Maintenance sirolimus target trough levels were 8 ng/mL in groups A and C. Each group received daclizumab induction and methylprednisolone maintenance. This first of two companion 1-year reports details demographics, drug-dosing interactions, and rejection.

RESULTS

There were no notable differences in group demographics, but a somewhat less favorable course occurred in group C, despite higher bioavailability of sirolimus in group C versus group A (P<0.001). Acute rejection rates were lower in groups A (4%) and B (4%) combined versus group C (14%) (P=0.03). Histopathologic findings were supported by comparing perioperative with 1-year postoperative protocol biopsies.

CONCLUSIONS

This 1-year interim analysis indicates that a decreasing dosage of tacrolimus with either adjunctive sirolimus or MMF may optimize future graft survival versus a less favorable outcome using a similar algorithm with CsA and sirolimus.

Efficacy of sirolimus (rapamycin) administered concomitantly with a subtherapeutic dose of cyclosporin in the treatment of severe psoriasis: a randomized controlled trial

BACKGROUND

The identification of a highly potent immunosuppressive/antiproliferative agent with an acceptable toxicity profile has long been a goal for the management of severe plaque psoriasis.

OBJECTIVES

To investigate the efficacy and safety of sirolimus (Rapamune) for severe psoriasis when given alone or in association with cyclosporin.

METHODS

In a randomized, double-blind, eight parallel group, pilot study in 24 out-patient centres in seven European countries, 150 patients, 18 years and older, with severe chronic plaque psoriasis were given sirolimus 0.5, 1.5 and 3.0 mg m(-2) daily for 8 weeks, either alone or in association with a subtherapeutic dose of cyclosporin (1.25 mg kg(-1) daily). Cyclosporin 5 mg kg(-1) daily was the positive control and cyclosporin 1.25 mg kg(-1) daily the negative control. The primary efficacy variable was the mean percentage reduction in Psoriasis Area and Severity Index (PASI). Safety assessments included monitoring of adverse events, clinical laboratory parameters and sirolimus/cyclosporin blood concentrations.

RESULTS

The greatest mean percentage decreases in PASI were seen with cyclosporin 5.0 mg kg(-1) daily (70.5%) and with sirolimus 3.0 mg m(-2) daily + cyclosporin 1.25 mg kg(-1) daily (63.7%). Both groups demonstrated significantly better results than cyclosporin 1.25 mg kg(-1) daily (mean decrease 33.4%). Serum creatinine levels were significantly lower for groups with sirolimus alone and sirolimus plus reduced-dose cyclosporin when compared with cyclosporin 5.0 mg kg(-1) daily. Adverse events associated with sirolimus included thrombocytopenia (5%), hyperlipidaemia (9%), aphthous stomatitis (9%) and acne (13%), whereas adverse events associated with cyclosporin included hot flushes (12%), hyperlipidaemia (9%) and increased serum creatinine (9%).

CONCLUSIONS

The concomitant administration of sirolimus with a subtherapeutic dose of cyclosporin in severe psoriasis may permit a reduction in their respective toxicities, notably cyclosporin-induced nephrotoxicity.

Phase I/II trial of temsirolimus combined with interferon alfa for advanced renal cell carcinoma

PURPOSE

Temsirolimus, an inhibitor of the mammalian target of rapamycin, has single-agent activity against advanced renal cell carcinoma (RCC). A recommended dose and safety profile for the combination of temsirolimus and interferon alfa (IFN) were determined in patients with advanced RCC.

PATIENTS AND METHODS

Patients were enrolled onto a multicenter, ascending-dose study of temsirolimus (5, 10, 15, 20, or 25 mg) administered intravenously once a week combined with IFN (6 or 9 million units [MU]) administered subcutaneously three times per week. An expanded cohort was treated at the recommended dose to obtain additional safety and efficacy information.

RESULTS

Seventy-one patients were entered to receive one of six dose levels. The recommended dose was temsirolimus 15 mg/IFN 6 MU based on dose-limiting toxicities of stomatitis, fatigue, and nausea/vomiting, which were observed at higher doses of temsirolimus and IFN. The most frequent grade 3 or 4 toxicities occurring in any cycle included leukopenia, hypophosphatemia, asthenia, anemia, and hypertriglyceridemia for all patients and those who received the recommended dose. Among patients who received the recommended dose (n = 39), 8% achieved partial response and 36% had stable disease for at least 24 weeks. Median progression-free survival for all patients in the study was 9.1 months.

CONCLUSION

The combination of temsirolimus and IFN has an acceptable safety profile and displays antitumor activity in patients with advanced RCC. Temsirolimus 15 mg plus IFN 6 MU is the recommended dose for evaluation in a randomized phase III study.

Rapid simultaneous quantification of immunosuppressants in transplant patients by turbulent flow chromatography combined with tandem mass spectrometry

BACKGROUND

Immunosuppressant therapeutic drug monitoring (TDM) is an important requirement in the management of post-transplant patients. Our aim was to develop and evaluate a robust high-throughput method using turbulent flow chromatography (TFC) coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS) for the simultaneous quantification of cyclosporin A (CsA), tacrolimus (FK 506) and sirolimus.

METHODS

A total of 1483 EDTA-blood pre-dosage samples from 147 kidney, 67 liver, 15 kidney/pancreas, and 48 bone marrow recipients were collected. After hemolysis and protein precipitation of 50 microl blood, fast and efficient on-line matrix elimination was achieved using turbulent flow chromatography. Tandem mass spectrometric detection and quantification was performed using multiple reaction monitoring (MRM).

RESULTS

The total analysis time of the column switching method was 3 min. The method was linear from 4.5 to 1500 ng/ml for cyclosporin A, from 0.2 to 100 ng/ml for tacrolimus, and from 0.4 to 100 ng/ml for sirolimus. The accuracy was >95%. Within and between-run assay variation coefficients ranged from 2.4% to 9.3%. Excellent correlation with other standard methods (immunoassay, HPLC) was observed.

CONCLUSIONS

The presented turbulent flow chromatography-tandem mass spectrometric platform offers a very fast, simple and economical method with an excellent validation profile and is well suited for daily pre- and post-dosage immunosuppressant monitoring.

Rapamycin: distribution, pharmacokinetics and therapeutic range investigations: an update

Based on the findings above, a number of conclusions can be made regarding the distribution, pharmacokinetics, and therapeutic range investigations with RAPA: (a) the majority of the drug is sequestered in erythrocytes, resulting in whole blood concentrations being considerably higher than plasma concentrations; (b) the drug is metabolized by the same cytochrome P450 3A enzyme involved in the metabolism of CsA and FK506. Metabolites are primarily simple demethylations and hydroxylations with 41-O-demethyl RAPA being the major metabolite both in vivo and in vitro; (c) the drug has a relatively long half-life in both humans and animals with 24-h trough concentrations being within the analytical range of HPLC when immunosuppressive doses are administered; (d) the drug exhibits a degree of proportionality between trough concentrations and dose; (e) a strong correlation exists between area under the concentration-time curve and trough blood concentration at steady state; (f) trough concentrations of the drug appear to be related to immunosuppressive efficacy and drug-related side effects; (g) the nephro- and neurotoxic properties of CsA are not augmented by concurrent treatment with RAPA; and (h) phase IIB trial results have shown a decrease of acute rejection episodes from 40% to < 10% among patients treated with full-dose CsA plus RAPA. The studies described here should provide a basis for the establishment of therapeutic monitoring protocols for RAPA. In addition, new derivatives of RAPA, such as SDZ RAD, designed to overcome formulation problems associated with RAPA, while maintaining similar pharmacokinetics and in vivo activity, show promise as alternatives to RAPA.

Simultaneous simple and fast quantification of three major immunosuppressants by liquid chromatography--tandem mass-spectrometry

OBJECTIVES

The aim of the current study was to develop a simple, fast and universal method for quantification of any combination of the three major immunosuppressants sirolimus, tacrolimus and cyclosporin in whole blood, using a LC-tandem mass spectrometer (API-2000, SCIEX, Toronto, Canada).

METHODS

250 microL whole blood was spiked with internal standard (ritonavir), and protein precipitated with 350 microL acetonitrile. The sample was centrifuged and 30 microL aliquot was injected onto the HPLC column, where it underwent an online extraction with ammonium acetate. After that the automatic switching valve was activated, changing the mobile phase to methanol and thereby eluting the analytes into the tandem mass spectrometer. The high selectivity of a tandem mass analyzer allows determination of any combination of the three drugs within a 5 min run.

RESULTS

Between-day precision was between 2.4% and 9.7% for all analytes at the concentrations tested. Accuracy ranged between 98.8% and 103.2% (n = 20). The method was linear over the measuring ranges of all analytes. Within-run precision was below %CV = 6% for all analytes. Good correlation with other analytical methods was observed.

CONCLUSIONS

The simplicity, universality and high throughput of the method make it suitable for application in a clinical laboratory. The method has been implemented in our laboratory for a routine use.

The portal immunosuppressive storm: relevance to islet transplantation?

Outcomes in clinical islet transplantation improved substantially with the introduction of combined sirolimus and tacrolimus immunosuppression. However, multiple islet preparations are often required to achieve insulin independence, suggesting that islet engraftment may not be optimal when these agents are absorbed via the portal vein. The current study was designed to assess the differential concentrations of immunosuppressive drugs within the portal and systemic circulations of a large animal model, to assess the local concentrations of drugs to which islets are exposed early after implantation. Chronic catheters were placed in the portal vein and carotid artery of 6 mongrel dogs, and immunosuppressants were administered orally. Blood samples were drawn simultaneously from portal and systemic catheters, and drug concentrations were analyzed. Peak immunosuppressant levels as well as area under the curve were dramatically elevated in portal blood relative to systemic levels for all drugs tested. This "portal storm" of immunosuppression may be relevant to intrahepatic islet transplantation.

Current opinions on therapeutic drug monitoring of immunosuppressive drugs

The pharmacokinetics of the immunosuppressive drugs cyclosporine, tacrolimus, mycophenolate mofetil (MMF), and sirolimus are complex and unpredictable. A narrow therapeutic index unique to each patient, as well as variable absorption, distribution, and elimination, are characteristics of these drugs. Therapeutic drug monitoring plays a key role in helping clinicians maintain blood and plasma levels of immunosuppressive drugs within their respective therapeutic ranges. Variation in concentrations outside the narrow therapeutic ranges can result in adverse clinical outcomes. Therapeutic drug monitoring ensures that concentrations are not too high or too low, thereby reducing the risks of toxicity or rejection, respectively. Therapeutic monitoring of immunosuppressive drugs has been based on several choices of assay and biologic fluid (i.e., whole blood, plasma) appropriate for a particular drug. High-performance liquid chromatography (HPLC) remains the gold standard among assay methods used to monitor immunosuppressive drugs. Although HPLC is the assay of choice for cyclosporine, newer monoclonal assays are suitable as well for routine monitoring. HPLC is also widely used for therapeutic drug monitoring of mycophenolic acid, the active metabolite of MMF, and an immunoassay (used in European centers) has been developed. Therapeutic drug monitoring of tacrolimus has been improved with the recent development of assays with greater sensitivity and specificity for tacrolimus than those previously available. No commercial assays are currently available for the therapeutic monitoring of sirolimus. It is also important to identify a specific pharmacokinetic parameter for each individual drug, whether it is trough or area under the concentration-time curve, that may be most useful as a tool for optimal therapeutic drug monitoring in clinical practice. With an increased understanding of the pharmacokinetics of immunosuppressive drugs, therapeutic drug monitoring guidelines will be more clearly defined to ensure the safe and effective management of transplant recipients.

Population pharmacokinetics of everolimus in de novo renal transplant patients: impact of ethnicity and comedications

BACKGROUND

Everolimus is a macrolide immunosuppressant intended for acute rejection prophylaxis after kidney transplantation.

METHODS

A total of 5260 blood samples were collected in the context of two randomized, double-blind, multicenter efficacy trials in 673 patients over a 6-month period after kidney transplantation. The data were evaluated in a nonlinear mixed-effects model. The influence of demographic characteristics (age, weight, sex, and ethnicity) and of comedications on everolimus exposure was explored.

RESULTS

For a reference 44-year-old, 71-kg Caucasian kidney allograft recipient receiving everolimus as part of a cyclosporine (INN, ciclosporin)-prednisone immunosuppressive regimen, the absorption rate constant was 6.07 h(-1) (standard error [SE], 0.70 h(-1)), the apparent clearance was 8.8 L/h (SE, 0.2 L/h), and the apparent central distribution volume was 110 L (SE, 5 L). There were no clinically relevant influences of age, weight, or sex on clearance. No significant difference in clearance was detected for Asian patients, whereas black patients had an average clearance that was 20% higher than that of nonblack patients. Patients concomitantly receiving erythromycin or azithromycin had an average 19% lower clearance. One patient receiving itraconazole had a 74% reduction in clearance. After we accounted for covariates, the remaining interindividual variability in clearance was 27% and the variability for distribution volume was 36%. The combined intraindividual and assay/measurement residual error in everolimus blood concentrations was 31%.

CONCLUSIONS

Dose adjustment of everolimus on the basis of weight does not appear necessary. Black patients may need a higher dose to achieve exposure that is similar to that of nonblack patients. Concomitant administration of potent inhibitors of the cytochrome P450 isozyme CYP3A may reduce everolimus clearance and increase its blood concentrations.

CYP3A5*3 influences sirolimus oral clearance in de novo and stable renal transplant recipients

BACKGROUND

The low and highly variable oral bioavailability of the immunosuppressant sirolimus is thought to result partly from genetic polymorphism of the CYP3A5 gene.

METHODS

This study aimed to evaluate the contribution of the CYP3A5 single-nucleotide polymorphism A6986G to the interindividual variability of sirolimus pharmacokinetics in 47 renal transplant patients at steady state, 21 of whom were also followed up for the first 3 months after transplantation. The patients were administered sirolimus, mycophenolate mofetil, and corticosteroids but no calcineurin inhibitor. They were genotyped for CYP3A5*3 by use of real-time quantitative polymerase chain reaction based on the 5'-nuclease allelic discrimination assay. Full sirolimus blood concentration profiles were measured at steady state (3 months after transplantation or more) in all patients, as well as at weeks 1 and 2 and month 1 in 21 of these patients, by use of liquid chromatography-tandem mass spectrometry. The sirolimus area under the concentration-time curve (AUC) was calculated via the standard noncompartmental approach. Maximal concentration (C(max)) and trough level (C(0)) values were measured.

RESULTS

Significantly lower AUC/dose, C(max)/dose, and C(0)/dose values were found at steady state (n = 47) in individuals carrying at least 1 CYP3A5*1 allele (n = 6) than in *3/*3 patients (26.6 +/- 15.7 versus 51.1 +/- 21.1 [P = .008], 4.8 +/- 3.3 versus 7.7 +/- 3.3 [P = .02], and 1.5 +/- 0.8 versus 3.0 +/- 1.5 [P = .01], respectively), as well as during all posttransplant periods in the subgroup of 21 patients who were followed up for the first 3 months after transplantation (n = 21) (P < .05 always). Patients with the CYP3A5*1/*1 and *1/*3 genotypes required a significantly higher sirolimus daily dose to achieve the same blood concentration at steady state as *3/*3 patients. In patients followed up for the first 3 months after transplantation, C(0) levels within the target range were only achieved after 1 to 3 months of repeated dosing and dose adjustment in both genotypic groups.

CONCLUSION

These results confirm that sirolimus metabolic activity and oral clearance are significantly decreased in patients who are homozygous for the CYP3A5*3 single-nucleotide polymorphism and suggest that the determination of this polymorphism could be useful for a priori dose adjustment of sirolimus, given the long half-life of this drug.

Dyslipidemia in renal transplant recipients treated with a sirolimus and cyclosporine-based immunosuppressive regimen: incidence, risk factors, progression, and prognosis

BACKGROUND

This retrospective study compared the incidence, severity, and predisposing factors for dyslipidemia among renal transplant patients treated for up to 6 years with a cyclosporine +/- prednisone-based concentration-controlled regimen without (n=118) or with (n=280) ascending exposures to sirolimus.

METHODS

The diagnosis of dyslipidemia was established when the serum cholesterol value (CHO) was more than 240 mg/dL or serum triglycerides (TG) were more than 200 mg/dL. Generalized estimating equations and mixed-modeling procedures were used for statistical analyses.

RESULTS

Hypercholesterolemia was observed in 46% to 80% and hypertriglyceridemia in 43% to 78% of sirolimus-treated patients during the first 6 posttransplantation months. The mean peak serum lipid levels among patients in the sirolimus group (CHO=285.5 mg/dL; TG=322.4 mg/dL) were significantly higher than those in the nonsirolimus group (CHO=250.2 mg/dL and TG=267.6 mg/dL; both P<0.01). The lipid values, which were persistently elevated during the first posttransplantation year, decreased slowly thereafter but remained significantly higher than the pretransplantation levels beyond 4 years after transplantation. The two forms of hyperlipidemia tended to occur in parallel (Pearson's coefficient of correlation, r=0.5, P<0.001), showing a positive predictive value of 0.67 and a negative predictive value of 0.65. However, there was no significant difference in the incidence of cardiovascular events within 4 years after transplantation among patients treated with versus without sirolimus.

CONCLUSION

The dyslipidemia associated with sirolimus therapy, albeit persistent, does not seem to represent a major risk factor for the early emergence of cardiovascular complications.

Sirolimus and tacrolimus trough concentrations and dose requirements after kidney transplantation in relation to CYP3A5 and MDR1 polymorphisms and steroids

BACKGROUND

CYP3A5 and MDR1 polymorphisms have been shown to influence tacrolimus blood concentrations and dose requirements. The aim is to determine whether these polymorphisms also affect sirolimus trough concentrations and dose requirements after kidney transplantation.

METHODS

Eighty-five renal transplant recipients receiving sirolimus were included. Twenty-four were treated with a combined sirolimus-tacrolimus regimen. Eighty-one patients received steroids. Sirolimus and tacrolimus were adjusted to a target therapeutic window. CYP3A5 (intron 3) and MDR1 (exons 12, 21, 26) genotypes were correlated to the adjusted trough concentrations and dose requirements for both sirolimus and tacrolimus.

RESULTS

There were no significant correlation between adjusted sirolimus trough concentrations or dose requirements and genetic polymorphisms. In a multiple regression model, adjusted-prednisone dose was involved with a positive or negative effect when considering sirolimus dose requirements or adjusted concentrations, respectively. In the subgroup of patients treated by tacrolimus and sirolimus, adjusted tacrolimus doses were higher in patients carrying at least one CYP3A5 *1 allele (median 0.083 vs. 0.035 mg/kg for CYP3A5*3/*3 patients, P<0.05). Adjusted-prednisolone dose and CYP3A5 polymorphism explained up to 61% of the variability in tacrolimus dose requirements.

CONCLUSIONS

Unlike tacrolimus, sirolimus adjusted trough concentrations and dose requirements seem not affected by CYP3A5 and MDR1 polymorphisms. Adjusted-prednisone dose has a significant impact on tacrolimus and sirolimus dose requirements.

A randomized long-term trial of tacrolimus/sirolimus versus tacrolimums/mycophenolate versus cyclosporine/sirolimus in renal transplantation: three-year analysis

BACKGROUND

We report three-year (interim) effects of combining sirolimus (Siro) vs. mycophenolate mofetil (MMF) as adjunctive therapy with calcineurin inhibitors (CI) in renal transplantation in the three different CI-based regimens.

METHODS

Between May 2000 and December 2001, 150 recipients of deceased donor (DD) and living donor (LD) kidney transplants were randomized into three groups (n=50/group): Group A (Tacro/Siro), Group B (Tacro/MMF) and Group C (CsA/Siro). This report details drug dosing and monitoring, protocol discontinuance, biopsy-proven rejection, graft failure, other adverse events, and death at 36 months postoperatively.

RESULTS

Actual patient and graft survival respectively in Group A was 90% and 82%, in Group B was 92% and 88%, and in Group C was 96% and 88% (not significant). Biopsy-confirmed acute rejection incidents showed a trend in favor of Group B (10%) vs. Group A (26%) and Group C (20%) combined (P=0.07). The geometric mean */SE serum creatinine concentration and arithmetic mean +/- SE Cockroft-Gault creatinine clearance calculations, respectively, were 1.39*/1.1 and 72.8+/-4.3 for Group A, 1.36*/1.1 and 72.1+/-4.1 for Group B, and 1.60*/1.1 and 61.8+/-3.8 for Group C, a statistically favorable difference for Group B over Group C (P=0.04). There was also less de novo development of posttransplant diabetes mellitus and lipid disorders in Group B vs. A and C (P<0.04).

CONCLUSIONS

This three-year (interim) analysis has indicated a trend towards better graft function, fewer endocrine disorders, and fewer acute rejection episodes comparing adjunctive MMF and Tacro vs. Siro and Tacro or Siro and CsA, in the dosages used.

Treatment of psoriasis with topical sirolimus: preclinical development and a randomized, double-blind trial

BACKGROUND

Systemically administered sirolimus has demonstrated efficacy in psoriasis in a multicentre European study.

OBJECTIVES

To determine the efficacy and safety of topically applied sirolimus in treating psoriasis.

METHODS

In vitro studies were followed by a pilot study designed to determine if sirolimus penetrates human skin, and by a randomized, double-blind, left-right comparative, dose-ranging study consisting of treatment with 2.2% sirolimus for 6 weeks and 8% sirolimus for an additional 6 weeks in 24 patients with stable, chronic plaque psoriasis. The primary outcome measure was clinical score. Secondary measures were ultrasound plaque thickness, plaque erythema, and computerized image analysis of immunohistochemical stains for immunocytes and proliferating cells. Pharmacokinetics and blood chemistry monitoring for safety were also performed.

RESULTS

A significant reduction in the clinical score (P = 0.03) (mean score 9.1 following sirolimus vs. 11.2 in control) was achieved with topical sirolimus. Measurements of plaque thickness and erythema did not show significant improvement with treatment. Computerized image analysis of biopsies showed a significant reduction in CD4+ cells (P = 0.0054) and proliferating cells (stained by Ki-67) in the epidermis (P = 0.0153) with sirolimus treatment compared with control.

CONCLUSIONS

Topically applied sirolimus penetrates normal skin and may have some antipsoriatic and immunosuppressive activity.

A clinical pharmacokinetic study of tacrolimus and sirolimus combination immunosuppression comparing simultaneous to separated administration

The pharmacokinetic (PK) interaction between tacrolimus (TAC) and sirolimus (SRL), similarly structured immunosuppressive compounds that share binding proteins, is unknown. The combination of SRL with cyclosporin (CsA) has been studied, and a 4-hour interval between dosing of the two drugs is recommended even though it is inconvenient for patients and may affect compliance. Twenty-five liver and kidney-pancreas transplant recipients treated with a combination of SRL and low-dose TAC completed full PK studies while being treated with 4-hour interval dosing (ID) and then with simultaneous dosing. Whole blood was sampled for immunoassay measurement of TAC and SRL levels. Blood concentration/dose ratios of SRL and TAC varied between patients by a factor of 8 and 5, respectively, but correlation between trough concentration levels (C(0)) and drug exposure area under the concentration-time curve (AUC) was excellent (TAC: r(2) = 0.82; SRL: r(2) = 0.83). Neither PK profiles of SRL nor those of TAC were altered by simultaneous administration. Dose-corrected AUC and C0 of TAC correlated with SRL (r(2) = 0.8 and 0.8, respectively). Bone marrow suppression and nephrotoxicity were not enhanced nor were any new toxicities observed when TAC and SRL were used in combination. These data confirm that simultaneous dosing of TAC and SRL after transplantation is safe and that trough level monitoring is adequate to control therapy.

Exposure-response relationships and drug interactions of sirolimus

Sirolimus (rapamycin, RAPAMUNE, RAPA) is an immunosuppressive agent used for the prophylaxis of renal allograft rejection and exhibits an immunosuppressive mechanism that is distinct from that for cyclosporine and tacrolimus. The purpose of this manuscript is to discuss the exposure-response relationships and drug interactions of sirolimus. The various factors affecting sirolimus whole blood exposure included first-pass extraction, formulation, food, demographics, liver disease, assay method, and interacting drugs. Clinically significant effects caused by food, pediatric age, hepatic impairment, and interacting drugs require recommendations for the safe and efficacious use of sirolimus in renal allograft patients. An exposure-response model based on multivariate logistic regression was developed using the interstudy data from 1832 renal allograft patients. The analysis revealed an increased probability of acute rejection for sirolimus troughs <5 ng/mL, cyclosporine troughs <150 ng/mL, human leukocyte antigen (HLA) mismatches > or =4, and females. The outcomes suggested that individualization of sirolimus doses immediately after transplantation, based on HLA mismatch and sex, would likely decrease the probability of acute rejections in renal allograft recipients who receive concomitant sirolimus, cyclosporine (full-dose), and corticosteroid therapy. Sirolimus is a substrate for both Cytochrome P450 3A (CYP3A) and P-glycoprotein (P-gp) and undergoes extensive first-pass extraction. Drugs that are known to inhibit or induce these proteins may potentially affect sirolimus whole blood exposure. In healthy volunteers, cyclosporine, diltiazem, erythromycin, ketoconazole, and verapamil significantly increased sirolimus whole blood exposure, and rifampin significantly decreased sirolimus exposure. However, sirolimus whole blood exposure was not affected by acyclovir, atorvastatin, digoxin, ethinyl estradiol/norgestrel, glyburide, nifedipine, or tacrolimus. Among the 15 drugs studied, sirolimus significantly increased the exposures of only erythromycin and S-(-)verapamil.