Long-term evaluation of analytical methods used in sirolimus therapeutic drug monitoring

Results of therapeutic monitoring of sirolimus blood concentrations are assay and laboratory dependent. This study compared performance over time of the IMx microparticle enzyme immunoassay (MEIA), Architect chemiluminescent microparticle immunoassay (CMIA), and liquid chromatography with mass spectrometric detection (LC/MS/MS) as part of a proficiency testing scheme. Pooled samples from sirolimus-treated patients and whole-blood samples spiked with known quantities of sirolimus were assayed monthly between 2004 and 2012. When results of pooled patient samples were compared with LC/MS/MS, the MEIA assay showed an overall mean percent bias of -2.3% ± 11.2% that, although initially positive, became increasingly negative from 2007 through 2009. The CMIA, which replaced the MEIA assay, had a mean percent bias of 21.9% ± 12.3%, remaining stable from 2007 through 2012. Similarly, for spiked samples, the MEIA showed an increasingly negative bias over time vs. LC/MS/MS, whereas CMIA maintained a stable positive bias. Based on comparison of immunoassay measurements on individual patient samples, CMIA values were more than 25% higher than MEIA values. These results highlight the importance of continued proficiency testing and regular monitoring of sirolimus assay performance. Clinicians must be aware of the methodology used and adjust target levels accordingly to avoid potential effects on efficacy and toxicity.

Palmoplantar peeling secondary to sirolimus therapy

Sirolimus (rapamycin) is an immunosuppressive agent commonly used in transplant recipients. Although sirolimus has less renal toxicity than calcineurin inhibitors, its use has been limited by its side effects. The most common cutaneous pathologies associated with sirolimus are inflammatory acneiform eruptions, lymphedema and aphthous ulcers. We present a novel cutaneous manifestation of sirolimus therapy that limited its use in at least one transplant recipient. Upon commencing sirolimus therapy, four solid organ transplant recipients developed tender, nonpruritic palmoplantar peeling within the first month of therapy. The peeling clinically resembled a mild form of hand-foot syndrome, yet none of the patients had been treated with chemotherapeutics. Desquamation presented on the palms and soles with dry vesicles and minor peeling extending to the dorsal aspects of the hands and feet. Histologically, the lesions were noninflammatory; the epidermis showed subtle separation between keratinocytes, suggesting either spongiosis or a defect in intercellular adhesion. One patient opted to discontinue treatment because of the tenderness associated with the palmoplantar peeling, which resulted in complete resolution within 2 weeks.

Phase I study of vinblastine and sirolimus in pediatric patients with recurrent or refractory solid tumors

BACKGROUND

The combination of vinblastine and mammalian target of rapamycin (mTOR) inhibitor sirolimus inhibits the growth of neuroblastoma xenografts through pro-apoptotic and anti-angiogenic mechanisms. This phase I study aimed to explore the safety and toxicity of this combination in pediatric patients with advanced solid tumors.

PROCEDURE

Patients ≤21 years of age with recurrent/refractory solid tumors (including CNS) were eligible. Sirolimus was administered daily by mouth or nasogastric (NG) tube, with doses adjusted to achieve a target trough concentration of 10-15 ng/ml, with weekly intravenous vinblastine (dose escalated 4-6 mg/m(2)/dose according to 3 + 3 phase I design).

RESULTS

Fourteen patients were enrolled (median age 8.7 years; range 2.3-19) of whom 12 were evaluable for toxicity and 11 for response. One patient experienced a dose-limiting toxicity (grade 3 mucositis) at the highest vinblastine dose level. Myelosuppression was the most common toxicity. Dose-adjusted sirolimus trough concentrations were significantly lower in patients receiving drug via NG tube (1.50 ± 0.75 ng/ml/mg vs. 2.25 ± 1.07 ng/ml/mg for oral administration). Correlative biomarker analysis demonstrated a significant reduction in serum concentration of soluble vascular endothelial growth factor receptor (sVEGFR2) at 28 days compared to baseline consistent with inhibition of angiogenesis. One patient had a partial response and three had stable disease for more than 3 months.

CONCLUSIONS

The combination of mTOR inhibitor and vinblastine given over an extended continuous schedule is safe, associated with a reduction in circulating angiogenic factor (CAF) VEGFR2 and resulted in clinical responses. Future studies using the intravenously administered mTOR inhibitor temsirolimus are planned.

Topical rapamycin for angiofibromas in paediatric patients with tuberous sclerosis: follow up of a pilot study and promising future directions

One of the most visible and potentially disfiguring cutaneous manifestations of tuberous sclerosis complex is the development of multiple facial angiofibromas, present in over 80% of patients. Topical rapamycin has been shown in many reports to be a safe and effective treatment for facial angiofibromas. In February 2012 we reported the results of a pilot study of four patients undertaken at a paediatric tertiary hospital in Australia. Since then, we have continued to refine the optimal formulation and concentration of topical rapamycin and expanded our selection of patients. We present an update on our current cohort of treated patients, discuss the optimal formulation of topical rapamycin and include a literature review on all published cases to date. Although topical rapamycin is not a curative treatment, we have demonstrated that its early institution significantly reduces both the vascularity and palpability of angiofibromas and prevents their progression with age. It is well tolerated and now a cost effective option.

ABCB1 haplotype influences the sirolimus dose requirements in Chinese renal transplant recipients

Sirolimus, an immunosuppressive drug used to prevent organ rejection after renal transplantation, has a narrow therapeutic index and a large inter-individual variability of pharmacokinetics. The aim of this study was to analyse the dose-normalized trough blood concentrations (C0 /D ratio) of sirolimus in patients with different genotypes and attempt to investigate the possible associations between ABCB1/CYP3A5 genotypes and sirolimus dose requirements in Chinese renal transplant recipients. Blood samples were collected from 85 Chinese renal transplant recipients who were treated with sirolimus for at least 3 months and polymorphisms of the ABCB1 and CYP3A5 were determined by the SNaPShot multiplex assay. The blood concentrations of sirolimus were determined with HPLC. A significant allele-dependent effect was observed between the CYP3A5*3 polymorphism and the C0 /D ratio of sirolimus. The patients bearing at least one CYP3A5*1 allele had a lower sirolimus C0/D ratio compared with those with a homozygous CYP3A5*3 genotype (p < 0.05). No significant differences of sirolimus C0/D ratios were observed among various ABCB1 1236C>T, 2677G>T/A and 3435C>T genotype groups. However, haplotype analysis including ABCB1 1236C>T, 2677G>T/A and 3435C>T SNPs showed that the mean sirolimus C0/D of subjects carrying the CGC/CGC diplotype was about 30% lower compared with those carrying the CGC/TTT or TTT/TTT diplotype, whether or not they expressed the CYP3A5 (p < 0.05). These results demonstrated that the haplotype of ABCB1 might be a better index for the prediction of sirolimus blood concentration than single SNPs. Genotyping of ABCB1 and CYP3A5 might help to optimize individualized sirolimus treatments for Chinese renal transplant recipients.

Inhibition of Orai1-mediated Ca(2+) entry is a key mechanism of the antiproliferative action of sirolimus in human arterial smooth muscle

Sirolimus (rapamycin) is used in drug-eluting stent strategies and proved clearly superior in this application compared with other immunomodulators such as pimecrolimus. The molecular basis of this action of sirolimus in the vascular system is still incompletely understood. Measurements of cell proliferation in human coronary artery smooth muscle cells (hCASM) demonstrated a higher antiproliferative activity of sirolimus compared with pimecrolimus. Although sirolimus lacks inhibitory effects on calcineurin, nuclear factor of activated T-cell activation in hCASM was suppressed to a similar extent by both drugs at 10 μM. Sirolimus, but not pimecrolimus, inhibited agonist-induced and store-operated Ca(2+) entry as well as cAMP response element binding protein (CREB) phosphorylation in human arterial smooth muscle, suggesting the existence of an as-yet unrecognized inhibitory effect of sirolimus on Ca(2+) signaling and Ca(2+)-dependent gene transcription. Electrophysiological experiments revealed that only sirolimus but not pimecrolimus significantly blocked the classical stromal interaction molecule/Orai-mediated, store-operated Ca(2+) current reconstituted in human embryonic kidney cells (HEK293). A link between Orai function and proliferation was confirmed by dominant-negative knockout of Orai in hCASM. Analysis of the effects of sirolimus on cell proliferation and CREB activation in an in vitro model of arterial intervention using human aorta corroborated the ability of sirolimus to suppress stent implantation-induced CREB activation in human arteries. We suggest inhibition of store-operated Ca(2+) entry based on Orai channels and the resulting suppression of Ca(2+) transcription coupling as a key mechanism underlying the antiproliferative activity of sirolimus in human arteries. This mechanism of action is specific for sirolimus and not a general feature of drugs interacting with FK506-binding proteins.

Clinicopathologic features of post-transplant lymphoproliferative disorders arising after pediatric small bowel transplant

Few studies examined the clinicopathologic features of PTLD arising in pediatric SBT patients. Particularly, the association between ATG and PTLD in this population has not been described. Retrospective review of 81 pediatric patient charts with SBT--isolated or in combination with other organs--showed a PTLD incidence of 11%, occurring more frequently in females (median age of four yr) and with clinically advanced disease. Monomorphic PTLD was the most common histological subtype. There was a significant difference in the use of ATG between patients who developed PTLD and those who did not (p < 0.01); a similar difference was seen with the use of sirolimus (p < 0.001). These results suggested a link between the combination of ATG and sirolimus and development of more clinically and histologically advanced PTLD; however, the risk of ATG by itself was not clear. EBV viral loads were higher in patients with PTLD, and median time between detection of EBV to PTLD diagnosis was three months. However, viral loads at the time of PTLD diagnosis were most often lower than at EBV detection, thereby raising questions on the correlation between decreasing viral genomes and risk of PTLD.

Empiric switch from calcineurin inhibitor to sirolimus-based immunosuppression in pediatric heart transplantation recipients

Sirolimus is used in heart transplant patients with CAV and CNI-induced nephropathy. However, little is known regarding the tolerability, rejection rate, and effect on renal function when used empirically in children. We describe our experience with the empiric use of a sirolimus-based immunosuppressive regimen in pediatric heart transplantation recipients. We reviewed records of patients in whom conversion was attempted to a CNI-free sirolimus-based regimen. Rejection episodes and measures of renal function were recorded. We attempted to convert 20 patients, of which 16 were successful. In total, six of 20 patients (30%) experienced adverse effects. Of the 16 converted, four patients converted to sirolimus due to CNI-induced disease (three nephropathy, one CAV), while 12 patients (mean age 5.5 yr, range 0.1-21 yr; 33% female; 33% with a history of congenital heart disease) were empirically switched to sirolimus at a mean of 2.3 yr after transplant. Follow-up was available for a mean of 2.5 yr after conversion (range 0.5-8.3 yr). The rate of rejection while taking CNIs was 0.18 rejection episodes per patient-year (total of five episodes), compared with 0.03 rejection episodes per patient-year (total of one episode) while on sirolimus. Renal function, in terms of GFR, significantly improved after sirolimus conversion at latest follow-up (from 86 ± 37 mL/min to 130 ± 49 mL/min, p = 0.02). Here, we demonstrate the potential benefit of empiric use of sirolimus in pediatric heart transplant patients in a CNI-free regimen. Larger and longer studies are needed to further clarify risks of rejection and adverse effect profiles.

Planned randomized conversion from tacrolimus to sirolimus-based immunosuppressive regimen in de novo kidney transplant recipients

Planned conversion from tacrolimus to sirolimus was evaluated in de novo kidney transplant recipients. In this multicenter, randomized, open-label study, 297 patients were initially treated with tacrolimus, mycophenolate sodium and prednisone. Of the 283 patients reaching 3 months, 97 were converted to sirolimus (SRL), 107 were maintained on tacrolimus (TAC) and 79 were patients receiving TAC without criteria to undergo intervention at month 3 (TACex). The primary objective was to show superior estimated glomerular filtration rate (eGFR) in the SRL group at month 24. Of the 258 patients who completed 24 months, 91 (94%) were in the SRL group, 101 (94%) in the TAC group and 66 (84%) in the TACex group. In the intention-to-treat population there were no differences in eGFR (66.2 ± 25.3 vs. 70.7 ± 25.1, p = 0.817) or in the severity of chronic sclerosing lesions scores in 24-month protocol biopsies. Higher mean urinary protein-to-creatinine ratio (0.36 ± 0.69 vs. 0.15 ± 0.53, p = 0.03) and higher incidence of treated acute rejection between months 3-24 (13.4% vs. 4.7%, p = 0.047) were observed in SRL compared to TAC group. In this population planned conversion from TAC to SRL 3 months after kidney transplantation was not associated with improved renal function at 24 months.

The efficacy and safety of cyclosporine reduction in de novo renal allograft patients receiving sirolimus and corticosteroids: results from an open-label comparative study

This study evaluated the safety and efficacy of a sirolimus, corticosteroid, and cyclosporine reduction regimen in an open-label, 12-month trial of 420 de novo renal allograft recipients at 49 European transplant centers. One month post-transplantation, 357 patients were randomized to receive standard-dose cyclosporine (sCsA, n = 179) or reduced-dose cyclosporine (rCsA, n = 178). All patients also received sirolimus and corticosteroids. The primary end points were the rate of biopsy-confirmed acute rejection (BCAR) and renal function, as measured by serum creatinine. Baseline demographic and donor characteristics were similar between groups. BCAR rates at 12 months were not significantly different: 11.2% for rCsA patients and 16.2% for sCsA patients. Mean serum creatinine (±SEM) was significantly lower (1.75 ± 0.10 vs. 1.97 ± 0.07 mg/dl, P < 0.001), and creatinine clearance (±SEM; Nankivell method) was significantly higher (57.8 ± 1.78 vs. 49.5 ± 2.46 ml/min, P < 0.001) in patients receiving rCsA versus sCsA at 1 year, respectively. Patient and graft survival exceeded 98% in both groups. No significant differences in infection or malignancy were noted between groups. The rCsA with sirolimus and corticosteroid regimen resulted in excellent 12-month patient and graft survival, a low incidence of BCAR, and improved renal function in renal allograft recipients. Sirolimus administered with rCsA and corticosteroids provided adequate immunosuppression while reducing the potential for the nephrotoxic effects of cyclosporine. These findings may help to improve long-term renal allograft outcomes.

Adventitial nab-rapamycin injection reduces porcine femoral artery luminal stenosis induced by balloon angioplasty via inhibition of medial proliferation and adventitial inflammation

BACKGROUND

Endovascular interventions on peripheral arteries are limited by high rates of restenosis. Our hypothesis was that adventitial injection of rapamycin nanoparticles would be safe and reduce luminal stenosis in a porcine femoral artery balloon angioplasty model.

METHODS AND RESULTS

Eighteen juvenile male crossbred swine were included. Single-injury (40%-60% femoral artery balloon overstretch injury; n=2) and double-injury models (endothelial denudation injury 2 weeks before a 20%-30% overstretch injury; n=2) were compared. The double-injury model produced significantly more luminal stenosis at 28 days, P=0.002, and no difference in medial fibrosis or inflammation. Four pigs were randomized to the double-injury model and adventitial injection of saline (n=2) or 500 μg of nanoparticle albumin-bound rapamycin (nab-rapamycin; n=2) with an endovascular microinfusion catheter. There was 100% procedural success and no difference in endothelial regeneration. At 28 days, nab-rapamycin led to significant reductions in luminal stenosis, 17% (interquartile range, 12%-35%) versus 10% (interquartile range, 8.3%-14%), P=0.001, medial cell proliferation, P<0.001, and fibrosis, P<0.001. There were significantly fewer adventitial leukocytes at 3 days, P<0.001, but no difference at 28 days. Pharmacokinetic analysis (single-injury model) found rapamycin concentrations 1500× higher in perivascular tissues than in blood at 1 hour. Perivascular rapamycin persisted ≥8 days and was not detectable at 28 days.

CONCLUSIONS

Adventitial nab-rapamycin injection was safe and significantly reduced luminal stenosis in a porcine femoral artery balloon angioplasty model. Observed reductions in early adventitial leukocyte infiltration and late medial cell proliferation and fibrosis suggest an immunosuppressive and antiproliferative mechanism. An intraluminal microinfusion catheter for adventitial injection represents an alternative to stent- or balloon-based local drug delivery.

Growing experience with mTOR inhibitors in pediatric solid organ transplantation

Controlled trials of mTOR inhibitors in children following solid organ transplantation are scarce, although evidence from prospective single-arm studies is growing. Everolimus with reduced CNI therapy has been shown to be efficacious and safe in de novo pediatric kidney transplant patients in prospective trials. Prospective and retrospective data in children converted from CNI therapy to mTOR inhibition following kidney, liver, or heart transplantation suggest preservation of immunosuppressive efficacy. Good renal function has been maintained when mTOR inhibitors are used de novo in children following kidney transplantation or after conversion to mTOR inhibition with CNI minimization. mTOR inhibition with reduced CNI exposure is associated with a low risk for developing infection in children. Growth and development do not appear to be impaired during low-dose mTOR inhibition, but more studies are required. No firm conclusions can be drawn as to whether mTOR inhibitors should be discontinued in children requiring surgical intervention or whether mTOR inhibition delays progression of hepatic fibrosis after pediatric liver transplantation. In conclusion, current evidence suggests that use of mTOR inhibitors in children undergoing solid organ transplantation is efficacious and safe, but a number of issues remain unresolved and further studies are required.

Impact of calcineurin-inhibitor conversion to mTOR inhibitor on renal allograft function in a prednisone-free regimen

Traditionally, chronic calcineurin inhibitor (CNI) nephrotoxicity has been considered to be one of the main nonimmune mechanisms causing chronic renal allograft dysfunction. CNI minimization and withdrawal strategies have yielded inconsistent results. Few studies address the feasibility of CNI elimination in a prednisone-free regimen. We report a prospective, randomized trial in 200 patients evaluating the impact on renal function and incidence of acute rejection after conversion from tacrolimus (Tac) to sirolimus (SRL). Patients with recent (<3 months) acute rejection episodes or with >0.5 g/day of proteinuria were excluded. All were induced with alemtuzumab, underwent rapid steroid elimination and were maintained on mycophenolate mofetil and Tac. At 12 months posttransplant, patients were randomized 2:1 to SRL (n = 123) or maintained on Tac (n = 64). Mean follow-up was 41.1 ± 15.8 months in the SRL group and 40.7 ± 14.4 months in the Tac group. Biopsy-proven acute rejection at 24 months postrandomization was similar between the groups. Patient survival, graft survival and estimated GFR were also not statistically different. Our study demonstrates that in a prednisone-free immunosuppressive regimen, conversion from Tac to SRL at 12 months posttransplantation is not associated with increased rates of acute rejection and graft loss. However, despite CNI elimination, renal allograft function is equally maintained in both groups.

Attenuation of cardiac allograft vasculopathy by sirolimus: Relationship to time interval after heart transplantation. J Heart Lung Transplant. 2013;32:784-791. [PMID: 23856215 DOI: 10.1016/j.healun.2013.05.015]

BACKGROUND

The aim of the study was to assess temporal changes in plaque size and components after heart transplantation (HTx), and to evaluate the differences in treatment effects on plaque progression between sirolimus and calcineurin inhibitors (CNIs).

METHODS

The study comprised 146 HTx recipients who were converted from CNIs to sirolimus as primary immunosuppressant (sirolimus group, n = 61) and those who were maintained on CNIs (CNI group, n = 85). A retrospective compositional analysis of serial virtual histology-intravascular ultrasound was performed.

RESULTS

During a median follow-up of 2.8 years, there was a significant difference in plaque volume in favor of sirolimus between groups (p = 0.004). When subjects were sub-classified according to the time interval between HTx and study inclusion, those in the early group (≤2 years after HTx) had a greater increase in plaque volume (p = 0.006), characterized by a higher progression rate of fibrous plaque volume (p = 0.01). The treatment difference between groups in plaque volume was identified in the early group in favor of sirolimus with attenuating effects on the progression of fibrous plaque component (both p = 0.03 for interaction). By contrast, there were significant differences in necrotic core and dense calcium volume (both p < 0.05 for interaction) in favor of CNIs in the late group (≥6 years after HTx).

CONCLUSIONS

Compared with continued CNI therapy, sirolimus attenuated plaque progression in recipients with early conversion, but contributed to increases in necrotic core and dense calcium volume in those with late conversion. Our study supports the hypothesis that early initiation of sirolimus offers greater benefits in the treatment of CAV.

Sirolimus stimulates vascular stem/progenitor cell migration and differentiation into smooth muscle cells via epidermal growth factor receptor/extracellular signal-regulated kinase/β-catenin signaling pathway

OBJECTIVE

Sirolimus-eluting stent therapy has achieved considerable success in overcoming coronary artery restenosis. However, there remain a large number of patients presenting with restenosis after the treatment, and the source of its persistence remains unclarified. Although recent evidence supports the contribution of vascular stem/progenitor cells in restenosis formation, their functional and molecular responses to sirolimus are largely unknown.

APPROACH AND RESULTS

Using an established technique, vascular progenitor cells were isolated from adventitial tissues of mouse vessel grafts and purified with microbeads specific for stem cell antigen-1. We provide evidence that vascular progenitor cells treated with sirolimus resulted in an induction of their migration in both transwell and wound healing models, clearly mediated by CXCR4 activation. We confirmed the sirolimus-mediated increase of migration from the adventitial into the intima side using an ex vivo decellularized vessel scaffold, where they form neointima-like lesions that expressed high levels of smooth muscle cell (SMC) markers (SM-22α and calponin). Subsequent in vitro studies confirmed that sirolimus can induce SMC but not endothelial cell differentiation of progenitor cells. Mechanistically, we showed that sirolimus-induced progenitor-SMC differentiation was mediated via epidermal growth factor receptor and extracellular signal-regulated kinase 1/2 activation that lead to β-catenin nuclear translocation. The ablation of epidermal growth factor receptor, extracellular signal-regulated kinase 1/2, or β-catenin attenuated sirolimus-induced SM-22α promoter activation and SMC differentiation.

CONCLUSIONS

These findings provide direct evidence of sirolimus-induced progenitor cell migration and differentiation into SMC via CXCR4 and epidermal growth factor receptor/extracellular signal-regulated kinase/β-catenin signal pathways, thus implicating a novel mechanism of restenosis formation after sirolimus-eluting stent treatment.

Unusual radiological presentation of sirolimus-associated pneumonitis

Sirolimus-associated pneumonitis, a rare but serious drug-induced lung injury, has become a great concern clinically, because of the increasing use of sirolimus (rapamycin) in patients who have been subjected to solid organ transplantation. We report sirolimus-associated pneumonitis in two women who underwent renal transplantation. At variance with previous reports, the radiological findings shown on chest radiographs and computed tomography scans of the chest in these two cases were consolidation lesions mainly with minimal interstitial abnormalities. Our reported cases highlight that awareness of various radiological findings of sirolimus-associated pneumonitis is pivotal for physicians to make early diagnosis of the disorder in patients who have undergone solid organ transplantation.

Rejection after conversion to a proliferation signal inhibitor in chronic heart transplantation

We sought to determine the incidence, risk factors, and consequences of acute rejection (AR) after conversion from a calcineurin inhibitor (CNI) to a proliferation signal inhibitor (PSI) in maintenance heart transplantation. Relevant clinical data were retrospectively obtained for 284 long-term heart transplant recipients from nine centers in whom CNIs were replaced with a PSI (sirolimus or everolimus) between October 2001 and March 2009. The rejection rate at one yr was 8.3%, stabilizing to 2% per year thereafter. The incidence rate after conversion (4.9 per 100 patient-years) was significantly higher than that observed on CNI therapy in the pre-conversion period (2.2 per 100 patient-years). By multivariate analysis, rejection risk was associated with a history of late AR prior to PSI conversion, early conversion (<5 yr) after transplantation and age <50 yr at the time of conversion. Use of mycophenolate mofetil was a protective factor. Post-conversion rejection did not significantly influence the evolution of left ventricular ejection fraction, renal function, or mortality during further follow-up. Conversion to a CNI-free immunosuppression based on a PSI results in an increased risk of AR. Awareness of the clinical determinants of post-conversion rejection could help to refine the current PSI conversion strategies.

Sirolimus ameliorates inflammatory responses by switching the regulatory T/T helper type 17 profile in murine colitis

Inflammatory bowel disease is characterized by dysregulated immune responses in inflamed intestine, with dominance of interleukin-17 (IL-17)--producing cells and deficiency of regulatory T (Treg) cells. The aim of this study was to investigate the effect and mechanisms of sirolimus, an inhibitor of the mammalian target of rapamycin, on immune responses in a murine model of Crohn's disease. Murine colitis was induced by intrarectal administration of 2,4,6-trinitrobenzene sulphonic acid at day 0. Mice were then treated intraperitoneally with sirolimus daily for 3 days. The gross and histological appearances of the colon and the numbers, phenotype and cytokine production of lymphocytes were compared with these characteristics in a control group. Sirolimus treatment significantly decreased all macroscopic, microscopic and histopathological parameters of colitis that were analysed. The therapeutic effects of sirolimus were associated with a down-regulation of pro-inflammatory cytokines tumour necrosis factor-α, IL-6 and IL-17A. Intriguingly, sirolimus administration resulted in a prominent up-regulation of the regulatory cytokine transforming growth factor-β. Supporting the hypothesis that sirolimus directly affects the functional activity of CD4+ CD25+ Treg cells, we observed a remarkable enhancement of FoxP3 expression in colon tissues and isolated CD4+ T cells of sirolimus-treated mice. Simultaneously, sirolimus treatment led to a significant reduction in the number of CD4+ IL-17A+ T cells in the mesenteric lymph node cells as well as IL-17A production in mesenteric lymph node cells. Therefore, sirolimus may offer a promising new therapeutic strategy for the treatment of inflammatory bowel disease.

Immunosuppressant therapeutic drug monitoring by LC-MS/MS: workflow optimization through automated processing of whole blood samples

OBJECTIVES

Although, due to its high specificity and sensitivity, LC-MS/MS is an efficient technique for the routine determination of immunosuppressants in whole blood, it involves time-consuming manual sample preparation. The aim of the present study was therefore to develop an automated sample-preparation protocol for the quantification of sirolimus, everolimus and tacrolimus by LC-MS/MS using a liquid handling platform.

METHODS

Six-level commercially available blood calibrators were used for assay development, while four quality control materials and three blood samples from patients under immunosuppressant treatment were employed for the evaluation of imprecision. Barcode reading, sample re-suspension, transfer of whole blood samples into 96-well plates, addition of internal standard solution, mixing, and protein precipitation were performed with a liquid handling platform. After plate filtration, the deproteinised supernatants were submitted for SPE on-line. The only manual steps in the entire process were de-capping of the tubes, and transfer of the well plates to the HPLC autosampler.

RESULTS

Calibration curves were linear throughout the selected ranges. The imprecision and accuracy data for all analytes were highly satisfactory. The agreement between the results obtained with manual and those obtained with automated sample preparation was optimal (n=390, r=0.96). In daily routine (100 patient samples) the typical overall total turnaround time was less than 6h.

CONCLUSIONS

Our findings indicate that the proposed analytical system is suitable for routine analysis, since it is straightforward and precise. Furthermore, it incurs less manual workload and less risk of error in the quantification of whole blood immunosuppressant concentrations than conventional methods.

Differential expression of p-mTOR in cutaneous basal and squamous cell carcinomas likely explains their different response to mTOR inhibitors in organ-transplant recipients

BACKGROUND

Mammalian Target of Rapamycin (mTOR) inhibitors, such as sirolimus and everolimus, have been shown to reduce cutaneous carcinogenesis in organ-transplant recipients requiring for immunosuppressive treatment to prevent from allograft rejection. Clinical observations suggest that cutaneous squamous cell carcinomas (SCC) are more sensitive than basal cell carcinomas (BCC) to the antitumoral effect of these inhibitors.

AIM

To investigate if the different response of SCC and BCC to mTOR inhibitors can be explained by differential expression of molecules involved in the mTOR signaling pathway.

MATERIALS AND METHODS

The expression of phospho-mTOR was immunohistocemically studied in specimens of cutaneous SCC and BCC. Results. All 15 SCCs expressed significant cytoplasmic phospho-mTOR immunoreactivity; by contrast, 12/13 BCC were completely negative, only one BCC exhibited weak phospho-mTOR immunoreactivity.

CONCLUSION

The considerably higher expression of phospho-mTOR in SCC compared to BCC is a likely explanation for their higher sensitivity to mTOR inhibitors.

Mucocutaneous disorders in renal transplant recipients receiving sirolimus-based immunosuppressive therapy: a prospective, case-control study

BACKGROUND

Sirolimus (SRL) has some dermatologic complications including acneiform eruptions, edema, aphthous ulceration, and onychopathy. However, controlled studies reporting the prevalence and clinical characteristics of mucocutaneous disorders are scarce.

OBJECTIVE

To investigate the prevalence and clinical spectrum of mucocutaneous disorders in renal transplant recipients (RTRs) receiving SRL and to compare the findings with those in RTRs not receiving SRL.

METHODS

Fifty RTRs (35 men, 15 women; mean age, 34.6 ± 11.6 yr) receiving SRL, 50 RTRs (36 men, 14 women; mean age, 34.4 ± 11.3 yr) not on SRL were screened for mucocutaneous disorders.

RESULTS

In RTRs receiving SRL, skin infection (78%) was the most common dermatologic disorder followed by facial hyperpigmentation (50%) and acneiform eruption (46%). Herpes simplex virus infections (14%) and seborrheic dermatitis (38%) were significantly more common in RTRs on SRL (p < 0.05); the frequencies of edema, aphthous ulceration, acne, and longitudinal nail ridging were similar in both groups (p > 0.05).

LIMITATIONS

This study had a small sample size. The investigator was not blinded to immunosuppressive treatment protocols.

CONCLUSION

Renal transplant recipients receiving SRL are more likely to develop seborrheic dermatitis and herpes simplex virus infections than those not taking SRL. Whereas, they are not more prone to edema, aphthous ulceration, acne, or longitudinal nail ridging.

Five-year clinical follow-up of a randomized comparison of a polymer-free sirolimus-eluting stent versus a polymer-based paclitaxel-eluting stent in patients with diabetes mellitus (LIPSIA Yukon trial)

OBJECTIVES

The long-term performance of polymer-free stent systems in patients with diabetes mellitus has not been investigated extensively. This study reports long-term results of the LIPSIA Yukon trial which compared the polymer-free sirolimus-eluting Yukon Choice stent with the polymer-based paclitaxel-eluting Taxus Liberté stent in this subpopulation. At 9 months, the Yukon Choice stent failed to show non-inferiority in terms of the primary end point late lumen loss, while no significant difference in clinical outcome was detected.

METHODS AND RESULTS

The LIPSIA Yukon trial randomized 240 patients with diabetes mellitus to a polymer-free sirolimus eluting stent (Yukon Choice, Translumina) versus a polymer-based paclitaxel-eluting stent (Taxus Liberté, Boston Scientific). Clinical follow-up was conducted with a standardized telephone follow-up and all events were centrally adjudicated. Follow-up was available for 98.3% of patients after a median of 5.0 years. The incidence of all-cause death (16.9% versus 14.0%, P = 0.67), respectively definite or presumed cardiovascular death (7.6% versus 8.8%, P = 0.94) were similar in the Yukon Choice and the Taxus Liberté group. There were no significant differences in the rates of myocardial infarction (9.3% versus 7.9%, P = 0.88), definite stent thrombosis (0.8% versus 0.9%, P = 1.0), target lesion revascularization (15.3% versus 15.8%, P = 1.0), target vessel revascularization (18.6% versus 23.7%, P = 0.44), non-target vessel revascularization (18.6% versus 26.3%, P = 0.21), and stroke (3.4% versus 4.4%, P = 0.96) between patients assigned to the Yukon Choice and the Taxus Liberté stent.

CONCLUSION

At 5 years of follow-up, clinical outcome was similar between the polymer-free sirolimus-eluting Yukon Choice stent and the polymer-based paclitaxel-eluting Taxus Liberté stent.

First report of a novel polymer-free dual-drug eluting stent in de novo coronary artery disease: results of the first in human BICARE trial

BACKGROUND

Persistence of stent polymer coating has been associated with incomplete endothelialization, expansive vessel remodeling, neoatherosclerosis, and delayed healing associated with inflammation that may contribute to late adverse events.

METHODS

The BICARE (Lepu Medical, Beijing, China) stent is a novel polymer-free, nanotechnology-based stent eluting sirolimus and probucol. As a first in human feasibility study, patients with a single de novo native coronary stenosis <30 mm in length and with reference vessel diameter from 2.5 to 4.0 mm underwent revascularization with the BICARE stent. The primary endpoint of target lesion failure (TLF) was assessed at 30 days. Secondary endpoints included in-stent late lumen loss and proportion of uncovered or malapposed stent struts by optical coherence tomography at 4-month angiographic surveillance.

RESULTS

Among 32 consecutive patients (age, 55.7 ± 8.7 years; men, 62.5%; diabetes, 18.8%), the average baseline reference vessel diameter and lesion length were 2.85 ± 0.48 mm and 15.0 ± 5.6 mm, respectively. At 30 days there was no occurrence of TLF. At 4 months (angiographic follow-up, N=32), angiographic in-stent late loss was 0.14 ± 0.19 mm, and the in-stent binary restenosis rate was 3.1%. Complete strut coverage was 98.2% with 0.2% malapposition among 16,751 analyzed struts. At 18 months, TLF occurred in 3 (9.4%) patients related to repeat revascularization with no adverse safety events identified.

CONCLUSIONS

The preliminary feasibility and safety of a polymer-free, dual-drug eluting stent are demonstrated by absence of early adverse safety events and favorable angiographic suppression of neointimal hyperplasia. Stent imaging suggests favorable healing with extensive stent strut coverage and very low malapposition. These findings further inform comparison with biopermanent polymer DES.

Outcomes with various drug-eluting or bare metal stents in patients with ST-segment-elevation myocardial infarction: a mixed treatment comparison analysis of trial level data from 34 068 patient-years of follow-up from randomized trials

BACKGROUND

The efficacy and safety of drug-eluting stents (DES) in patients with ST-segment-elevation myocardial infarction (STEMI) is controversial. Consequently, DES implantation has a class IIa indication in the American College of Cardiology/American Heart Association and the European Society of Cardiology STEMI guidelines.

METHODS AND RESULTS

PUBMED, EMBASE, and CENTRAL were searched for randomized clinical trials, until March 2013, comparing any of the 5 Food and Drug Administration-approved durable stent and polymer DES (sirolimus eluting stent, paclitaxel eluting stent, everolimus-eluting stent [EES], zotarolimus-eluting stent, and zotarolimus-eluting stent resolute), against each other or bare metal stents (BMS), and enrolling ≥ 50 patients with STEMI. Efficacy (target vessel revascularization) and safety (death, myocardial infarction, and stent thrombosis) outcomes at the longest reported follow-up times were evaluated. Twenty-eight randomized clinical trials with 34 068 patient-years of follow-up on subjects with STEMI fulfilled the inclusion criteria. When compared with BMS (reference rate ratio [RR] of 1), sirolimus eluting stent (RR, 0.46; 95% credibility interval [CrI], 0.36-0.56), paclitaxel eluting stent (RR, 0.69; 95% CrI, 0.53-0.87), and EES (RR, 0.42; 95% CrI, 0.26-0.62) were associated with a statistically significant reduction in rate of target vessel revascularization, with the point estimate for zotarolimus-eluting stent resolute trending in a similar direction. There was no increase in the risk of death, myocardial infarction, or stent thrombosis with any DES compared with BMS. Moreover, EES was associated with a statistically significant reduction in the rate of stent thrombosis when compared with sirolimus eluting stent (RR, 0.38; 95% CrI, 0.21-0.74), paclitaxel eluting stent (RR, 0.39; 95% CrI, 0.21-0.73), and even BMS (RR, 0.42; 95% CrI, 0.23-0.76). There was a 74% probability that EES had the lowest rate of any stent thrombosis when compared with all other stent types (no data on zotarolimus-eluting stent resolute). There was no increase in very late stent thrombosis with EES versus BMS (RR, 0.89; 95% CrI, 0.09-8.67).

CONCLUSIONS

In patients with STEMI, DES versus BMS was associated with substantial decrease in the risk of target vessel revascularization without compromising safety. EES had the added advantage of substantial reduction in the risk of stent thrombosis when compared with first-generation DES and BMS with no increase in very late stent thrombosis.

Sirolimus-FKBP12.6 impairs endothelial barrier function through protein kinase C-α activation and disruption of the p120-vascular endothelial cadherin interaction

OBJECTIVE

Sirolimus (SRL) is an immunosuppressant drug used to prevent rejection in organ transplantation and neointimal hyperplasia when delivered from drug-eluting stents. Major side effects of SRL include edema and local collection of intimal lipid deposits at drug-eluting stent sites, suggesting that SRL impairs endothelial barrier function (EBF). The aim of this study was to address the role of SRL on impaired EBF and the potential mechanisms involved.

APPROACH AND RESULTS

Cultured human aortic endothelial cells (HAECs) and intact human and mouse endothelium was examined to determine the effect of SRL, which binds FKBP12.6 to inhibit the mammalian target of rapamycin, on EBF. EBF, measured by transendothelial electrical resistance, was impaired in HAECs when treated with SRL or small interfering RNA for FKBP12.6 and reversed when pretreated with ryanodine, a stabilizer of ryanodine receptor 2 intracellular calcium release channels. Intracellular calcium increased in HAECs treated with SRL and normalized with ryanodine pretreatment. SRL-treated HAECs demonstrated increases in protein kinase C-α phosphorylation, a calcium sensitive serine/threonine kinase important in vascular endothelial (VE) cadherin barrier function through its interaction with p120-catenin (p120). Immunostaining of HAECs, human coronary and mouse aortic endothelium treated with SRL showed disruption of p120-VE cadherin interaction treated with SRL. SRL impairment of HAEC EBF was reduced with protein kinase C-α small interfering RNA. Mice treated with SRL demonstrated increased vascular permeability by Evans blue albumin extravasation in the lungs, heart, and aorta.

CONCLUSIONS

SRL-FKBP12.6 impairs EBF by activation of protein kinase C-α and downstream disruption of the p120-VE cadherin interaction in vascular endothelium. These data suggest this mechanism may be an important contributor of SRL side effects related to impaired EBF.

Sirolimus-loaded stealth colloidal systems attenuate neointimal hyperplasia after balloon injury: a comparison of phospholipid micelles and liposomes

Restenosis after angioplasty remains a serious complication in clinical cardiology. This study aims to investigate the stealth colloidal systems for local intra-arterial drug delivery. Micelles from polyethylene glycol conjugated with phosphatidylethanolamine and PEGylated liposomes loaded with sirolimus were prepared and characterized with regard to their loading efficiency, particle size distribution, zeta potential, morphology, nuclear magnetic resonance spectroscopy, drug release profile and stability. The antirestenotic effects of the sirolimus-loaded micelles (14 nm) and liposomes (90 nm) were evaluated and compared in the rat carotid injury model following local intravascular delivery. In comparison to control groups, treatment of balloon injured rats with drug loaded micelles and nanoliposomes significantly reduced vascular stenosis by 42% and 19%, respectively (P<0.05). In addition, the luminal area was significantly enlarged by 39% and 60% following treatment with sirolimus-loaded liposomes and micelles, respectively (P<0.05). Immunohistochemistry revealed that sirolimus-loaded nanocarriers suppressed cell proliferation (Ki67-positive cells) as compared to control groups without affecting the density of smooth muscle actin staining. These results suggest that both colloidal nanocarriers could serve as effective intramural drug delivery systems for the treatment of restenosis; however, phospholipid based micelles provided better antirestenotic effects than PEGylated liposomes.

Association of a change in immunosuppressive regimen with hemodynamic and inflammatory markers of cardiovascular disease after kidney transplantation

BACKGROUND

Although rejection rates and short-term graft survival have significantly improved in kidney transplantation with the introduction of calcineurin inhibitor (CNI), cardiovascular disease (CVD) and metabolic complications are being increasingly recognized as important causes of morbidity and mortality. We hypothesize that non-CNI proliferation signal inhibitor (PSI)-based immunosuppressive regimen is associated with improved arterial stiffness after kidney transplantation compared with CNI-based immunosuppressive regimens.

METHODS

This is a prospective, single-center study of renal transplant (RT) recipients comparing the metabolic, cardiovascular (pulse wave velocity and aortic augmentation index (AI) adjusted for heart rate (AI × 75)), inflammatory cytokines (interleukins (ILs) 6, 12, and 18) and graft-related outcomes at 3 and 15 months posttransplantation between RT recipients maintained on CNI- (CNI-CNI) or PSI-based (CNI-PSI) regimens including sirolimus and everolimus.

RESULTS

Fifty and 17 RT recipients maintained on CNI-CNI and CNI-PSI, respectively, were included in this study. Median time to PSI conversion from CNI was 5 months. Compared with CNI-CNI recipients, CNI-PSI recipients had significantly lower fasting blood glucose in nondiabetics (coefficient = -16.2; 95% confidence interval (CI) = -14.4 to -18.0; P < 0.01), lower IL-18 levels (coefficient = -229.16; 95% CI = -343.94 to -114.38; P < 0.01), and lower AI × 75 (coefficient = -5.14; 95% CI = -9.99 to -0.28; P = 0.04) at 15 months posttransplant in the multivariable models.

CONCLUSIONS

Our study suggests from the elimination of CNI for PSI may lower AIx75 and IL-18, both surrogate markers of CVD, but adequately powered, randomized, controlled studies are required to establish the causal relationship between immunosuppressive agents and CVD risk.

The effect of rifampin on the pharmacokinetics of sirolimus in healthy volunteers

Sirolimus, metabolized primarily by intestinal and hepatic CYP3A4, is a substrate for P-glycoprotein. CYP3A4 inducers would be expected to decrease sirolimus exposure. This open-label, nonrandomized study investigated effects of CYP3A4 induction, by rifampin, on sirolimus pharmacokinetics. Healthy volunteers received sirolimus 20 mg on day 1. After washout period, multiple 600-mg rifampin doses were administered daily for 14 days. On day 9, one 20-mg sirolimus dose was administered after an overnight fast (≥10 hours). Whole blood samples for sirolimus collected for 144 hours after each dose were analyzed by liquid chromatography/tandem mass spectrometry. Pharmacokinetic parameters, assessed using noncompartmental methods, were compared using analysis of variance. Geometric mean ratios of Cmax and AUCinf were 29% (90% CI: 26, 32%) and 18% (90% CI: 16, 21%), respectively, with rifampin co-administration versus sirolimus alone. Corresponding decreases in Cmax and AUC were 71% and 82%, respectively, which would likely cause trough concentrations to fall below the recommended therapeutic range. Mean CL/F increased approximately fivefold with rifampin versus sirolimus alone. Co-administering sirolimus and potent CYP3A inducers is not recommended. If co-administration is necessary, dose adjustment and concentration monitoring should be conducted.

Optimized formulation of solid self-microemulsifying sirolimus delivery systems

BACKGROUND

The aim of this study was to develop an optimized solid self-microemulsifying drug delivery system (SMEDDS) formulation for sirolimus to enhance its solubility, stability, and bioavailability.

METHODS

Excipients used for enhancing the solubility and stability of sirolimus were screened. A phase-separation test, visual observation for emulsifying efficiency, and droplet size analysis were performed. Ternary phase diagrams were constructed to optimize the liquid SMEDDS formulation. The selected liquid SMEDDS formulations were prepared into solid form. The dissolution profiles and pharmacokinetic profiles in rats were analyzed.

RESULTS

In the results of the oil and cosolvent screening studies, Capryol™ Propylene glycol monocapry late (PGMC) and glycofurol exhibited the highest solubility of all oils and cosolvents, respectively. In the surfactant screening test, D-α-tocopheryl polyethylene glycol 1000 succinate (vitamin E TPGS) was determined to be the most effective stabilizer of sirolimus in pH 1.2 simulated gastric fluids. The optimal formulation determined by the construction of ternary phase diagrams was the T32 (Capryol™ PGMC:glycofurol:vitamin E TPGS = 30:30:40 weight ratio) formulation with a mean droplet size of 108.2 ± 11.4 nm. The solid SMEDDS formulations were prepared with Sucroester 15 and mannitol. The droplet size of the reconstituted solid SMEDDS showed no significant difference compared with the liquid SMEDDS. In the dissolution study, the release amounts of sirolimus from the SMEDDS formulation were significantly higher than the raw sirolimus powder. In addition, the solid SMEDDS formulation was in a more stable state than liquid SMEDDS in pH 1.2 simulated gastric fluids. The results of the pharmacokinetic study indicate that the SMEDDS formulation shows significantly greater bioavailability than the raw sirolimus powder or commercial product (Rapamune® oral solution).

CONCLUSION

The results of this study suggest the potential use of a solid SMEDDS formulation for the delivery of poorly water-soluble drugs, such as sirolimus, through oral administration.

Two-Year Follow-up of Sirolimus-Eluting Stents versus Paclitaxel-Eluting Stents in Acute Myocardial Infarction

It has been shown that drug-eluting stents (DESs) significantly reduce restenosis rate when compared with bare-metal stents in a broad range of patients with coronary artery disease. However, current data are limited about the efficacy of different DESs in treatment of ST segment elevation myocardial infarction (STEMI). The aim of this study was to compare the effectiveness and safety of sirolimus-eluting stents (SESs) with paclitaxel-eluting stents (PESs) in primary percutaneous coronary intervention. We retrospectively examined 127 STEMI patients who underwent primary percutaneous coronary intervention. PES group consisted of 79 patients and SES group consisted of 48 patients. Patients were analyzed for major adverse cardiac events (MACE) and stent thrombosis (ST). The mean follow-up period was 2 years. The mean age was 53 ± 11 years in the SES group and 59 ± 11 years in the PES group (p = 0.03). Baseline and procedural characteristics were similar in the two groups except stent lengths, which was longer in the SES group. Two-year MACE rates were 8.3% in the SES group and 16.4% in the PES group (p = 0.28). Rates for ST for SES and PES groups were as follows: early ST was 2.08 versus 2.53%; late ST was 2.08 versus 2.53%; and very late ST was 2.08 versus 2.53% (p > 0.05). There were no statistically significant differences in MACE and ST rates between the SES and PES groups in the 2-year follow-up period. High ST rates detected in our study need to be clarified with future prospective and randomized clinical trials.

Dedicated Bifurcation Drug-eluting Stent BiOSS® - A Novel Device for Coronary Bifurcation Treatment

The Bifurcation Optimisation Stent System (BiOSS®) (Balton®, Poland) is a coronary, dedicated bifurcation, balloon-expandable stent made of 316 litre stainless steel tube with strut thickness of 120 micrometre (µm). It is covered with a mixture of a biodegradable polymer and an antiproliferative substance - paclitaxel (BiOSS Expert version) or sirolimus (BiOSS Lim version). The stent consists of two parts (the proximal with a larger diameter in relation to the distal one) connected with two connection struts (average 1.2 mm in length) at the step-up middle zone. The stent is crimped on a bottle-shaped semi-complaint balloon (Bottle®, Balton, Poland). Our intravascular ultrasound (IVUS) study revealed that the construction of the BiOSS stent assures an easy access to the side branch and is comparable to the classic stent lumen enlargement with less injury to the area adjacent to the most sensitive part of the bifurcation. A total number of 65 lesions in 63 consecutive patients were enrolled in the First-In-Man (FIM) registry for BiOSS Expert, where we achieved a 100 % device success rate. The long-term clinical results were satisfactory and closely related to the high-risk profile of the treated population. Our data demonstrated that simple and fast bifurcation treatment with a single dedicated bifurcation paclitaxel-eluting stent (BiOSS Expert) is feasible and highly successful. Based on the data collected in animal experiments and preliminary data in humans with BiOSS Lim, releasing sirolimus from the surface of the biodegradable coating, one may presume that this version will provide even better clinical results compared with the paclitaxel one.

Recovery of locked-in syndrome following liver transplantation with calcineurin inhibitor cessation and supportive treatment

Background:

Locked-in syndrome represents the most severe form of central pontine myelinolysis (CPM) and has been associated with a dismal outcome.

Case Report:

In this report we describe a case of severe locked-in syndrome after liver transplantation with spontaneous recovery with cessation of calcneurin inhibitor therapy and supportive treatment.

A 54-year old male received deceased-donor liver transplantation and developed decreased level of consciousness with spastic quadriplegia. A diagnosis of central pontine myelinolysis with extrapontine manifestations was confirmed by magnetic resonance imaging. His immunosuppresion was modified by switching from tacrolimus to sirolimus and addition of prednisone. The patient started to recover from symptoms fourth months after transplantation.

Conclusions:

Tacrolimus is known to have neurotoxic side effects and it may precipitate CPM in patients who have predisposing factors. Sirolimus and steroids should be considered as safe and an effective alternative for immunosuppression in the setting of CPM after liver transplantation.

Novel Intraocular Therapy in Non-infectious Uveitis of the Posterior Segment of the Eye

This article reviews the new clinically relevant data regarding the intraocular treatment of non-infectious uveitis. Triamcinolone acetonide is the most commonly used intravitreal corticosteroid for treatment of uveitis and uveitic macular oedema. The drug is available at low cost but it is associated with a high risk of raised intraocular pressure (IOP) and cataract and is not licensed for intraocular use. Dexamethasone implant (Ozurdex®) appears to have a better safety profile, and a slightly long-lasting effect than triamcinolone acetonide. Fluocinolone acetonide implant (Retisert®) implant allows the release of corticosteroids at a constant rate over a 3-year period, but it requires surgical placement and its use is associated with a very high risk of cataracts and raised intraocular pressure. Iluvien® is another fluocinolone acetonide implant that could represent a more convenient treatment option for such cases in the future as it can be inserted into the vitreous cavity through 25-gauge injector system in an outpatient setting. To circumvent the risks associated with corticosteroids use, non-corticosteroids related therapeutics including intravitreal methotrexate; anti-vascular endothelial growth factor treatments and intravitreal sirolimus have been recently developed.

Cost Utility of Sirolimus versus Tacrolimus for the Primary Prevention of Graft Rejection in Renal Transplant Recipients in Mexico

OBJECTIVE

Therapies for end-stage renal disease improve quality of life, and survival. In Mexico, clinicians often must choose between different therapies without the availability of comparative outcomes evaluation. The present study evaluates the comparative cost-utility of sirolimus (SIR) versus tacrolimus (TAC) for the primary prevention of graft rejection in renal transplant recipients in Mexico.

METHODS

We used modeling techniques to estimate the cost-effectiveness of SIR versus TAC to prevent graft rejection in patients with end-stage renal disease in the Mexican setting. The model estimates the cost of quality-adjusted life-year (QALY) per patient. We applied a 20-year horizon (1-year Markov cycles). Cost-effectiveness was expressed in terms of cost per QALY. All costs are presented in 2011 US dollars. Probabilistic sensitivity analyses were conducted.

RESULTS

The total cost for the SIR treatment arm over the 20-year duration of the model is estimated to be $136,778. This compares with $142,624 for the TAC treatment arm, resulting in an incremental cost of SIR compared with that of TAC of-$5,846. Over 20 years, SIR was estimated to have 8.18 QALYs compared with 7.33 QALYs for TAC. The resulting incremental utility of SIR compared with that of TAC is 0.84 QALY gained. SIR is estimated to be both less costly and more effective than TAC, indicating that it is the dominant strategy. Notably, results suggest that SIR has a 78% probability of being dominant over the TAC strategy and a 100% probability of having an incremental cost-effectiveness ratio at or below $10,064 (1 GDP) per QALY.

CONCLUSIONS

These analyses suggest that in the Mexican setting, the use of SIR in place of TAC for the prevention of graft rejection in this population is likely to be cost saving.

Cardiorenal benefits of early versus late cyclosporine to sirolimus conversion in a rat model

Objective:

To compare the cardiorenal effects of early versus late cyclosporine (CsA) to sirolimus (SRL) conversion, using a novel animal model that mimics these protocols used in the clinical practice, and focusing on blood pressure, heart rate (HR), biochemical data and heart and kidney lipid peroxidation.

Materials and Methods:

The study had five groups. Six male Wistar rats in each group were used during a 9-week study protocol: control, CsA (5 mg/kg/day), SRL (1 mg/kg/day); early conversion and late conversion. Cardiorenal evaluation was assessed by biochemical data, blood pressure, HR, and heart and kidney lipid peroxidation.

Results:

As expected, CsA promoted cardiorenal impairment, viewed by development of hypertension, tachycardia, increased urea, creatine kinase, and glucose levels, as well as heart and kidney oxidative stress. SRL, as expected, promoted less cardiorenal side effects, namely those related with nephrotoxicity. In agreement, both early and late conversions from CsA to SRL produced less side-effects, namely those related to the CsA-induced nephrotoxicity.

Conclusions:

In our model, both early and late CsA to SRL conversion promoted amelioration of the CsA -induced cardiorenal damage. However, early substitution seems to produce more benefits, in particular due to higher improvement of the cardiac profile.

Recovery of endocrine function after islet and pancreas transplantation

Long-standing type 1 diabetes (T1D) is associated with an absolute loss of endogenous insulin secretion (circulating C-peptide is undetectable) and a related defect in glucose counter-regulation that is often complicated by hypoglycemia unawareness, markedly increasing the risk for severe hypoglycemia. Both the transplantation of isolated islets and a whole pancreas can restore β-cell secretory capacity, improve glucose counter-regulation, and return hypoglycemia awareness, thus alleviating severe hypoglycemia. The transplantation of islets may require more than one donor pancreas, and the recovery of endocrine function for now appears more durable with a whole pancreas; however, islet transplantation outcomes are steadily improving. Because not all patients with T1D experiencing severe hypoglycemia are candidates to receive a whole pancreas, and since not all pancreata are technically suitable for whole organ transplantation, islet and pancreas transplantation are evolving as complementary approaches for the recovery of endocrine function in patients with the most problematic T1D.

Regulatory T cells exhibit decreased proliferation but enhanced suppression after pulsing with sirolimus

Although regulatory T cells (Tregs) suppress allo-immunity, difficulties in their large-scale production and in maintaining their suppressive function after expansion have thus far limited their clinical applicability. Here we have used our nonhuman primate model to demonstrate that significant ex vivo Treg expansion with potent suppressive capacity can be achieved and that Treg suppressive capacity can be further enhanced by their exposure to a short pulse of sirolimus. Both unpulsed and sirolimus-pulsed Tregs (SPTs) are capable of inhibiting proliferation of multiple T cell subpopulations, including CD4(+) and CD8(+) T cells, as well as antigen-experienced CD28(+) CD95(+) memory and CD28(-) CD95(+) effector subpopulations. We further show that Tregs can be combined in vitro with CTLA4-Ig (belatacept) to lead to enhanced inhibition of allo-proliferation. SPTs undergo less proliferation in a mixed lymphocyte reaction (MLR) when compared with unpulsed Tregs, suggesting that Treg-mediated suppression may be inversely related to their proliferative capacity. SPTs also display increased expression of CD25 and CTLA4, implicating signaling through these molecules in their enhanced function. Our results suggest that the creation of SPTs may provide a novel avenue to enhance Treg-based suppression of allo-immunity, in a manner amenable to large-scale ex vivo expansion and combinatorial therapy with novel, costimulation blockade-based immunosuppression strategies.

Preclinical evaluation of injectable sirolimus formulated with polymeric nanoparticle for cancer therapy

Nanoparticles are useful delivery vehicles for promising drug candidates that face obstacles for clinical applicability. Sirolimus, an inhibitor of mammalian target of rapamycin has gained attention for targeted anticancer therapy, but its clinical application has been limited by its poor solubility. This study was designed to enhance the feasibility of sirolimus for human cancer treatment. Polymeric nanoparticle (PNP)–sirolimus was developed as an injectable formulation and has been characterized by transmission electron microscopy and dynamic light scattering. Pharmacokinetic analysis revealed that PNP–sirolimus has prolonged circulation in the blood. In addition, PNP–sirolimus preserved the in vitro killing effect of free sirolimus against cancer cells, and intravenous administration displayed its potent in vivo anticancer efficacy in xenograft tumor mice. In addition, PNP–sirolimus enhanced the radiotherapeutic efficacy of sirolimus both in vitro and in vivo. Clinical application of PNP–sirolimus is a promising strategy for human cancer treatment.

Comparative Sirolimus Pharmacokinetics After Single-Dose Administration of Two Prototype 0.5-mg Tablets in Healthy Volunteers

Availability of a lower dose tablet would add to the dosing flexibility of currently available 1- and 2-mg sirolimus tablets for optimal concentrations and patient compliance. A randomized, 3-period crossover study was conducted in 30 fasting healthy volunteers (29 men, aged 31 ± 8 years, weight 79 ± 12 kg). Subjects were given 5 mg of sirolimus, either as doses of the 0.5-mg nonshellac-core prototype, 0.5-mg shellac-core prototype, or approved 1-mg tablet. Whole blood samples were collected at selected time points for 144 hours after dosing and analyzed using LC/MS/MS assay. Noncompartmental pharmacokinetic analysis was performed, followed by bioequivalence assessment. Twenty-four subjects completed all dosing periods, and no formulation-associated adverse events were reported. Ratios of maximum plasma concentration (Cmax ), area under the concentration-time curve to the last measured concentration (AUCT ), and area under the concentration-time curve from time 0 to infinity (AUC) for the nonshellac-core prototype compared with the 1-mg tablet were within the 80% to 125% range dictated by bioequivalence conventions. Similar results were observed when comparing the ratios of AUCT and AUC for the shellac-core prototype, while 90% confidence interval of the ratio of Cmax values was 105% to 129%. Within the context of clinical equivalence standards established by a phase 3 study comparing liquid to tablet formulations, it was concluded that both prototypes were clinically bioequivalent to the reference formulation.

New developments in mammalian target of rapamycin inhibitors for the treatment of sarcoma

Although sarcomas account for a small portion of solid malignancies, currently, there are few treatment options for sarcomas, particularly for advanced disease. The mammalian target of rapamycin (mTOR), a serine-threonine protein kinase in the phosphatidylinositol 3-kinase/serine/threonine protein kinase Akt signaling pathway, has an important role in the regulation of protein synthesis, cell proliferation, angiogenesis, and metabolism. Alterations of the mTOR signaling pathway are common in malignancies, including several types of sarcoma. Therefore, mTOR is a potentially important therapeutic target in these diseases. Rapamycin and its analogs (rapalogs) are effective anticancer agents in a broad range of preclinical models. Clinical trials with these agents alone and in combination with other anticancer agents, including chemotherapy and targeted therapies, have demonstrated potential clinical benefit in several types of sarcoma. The evidence from both preclinical and clinical studies supports further study of mTOR-targeting rapalogs in the treatment of various subtypes of sarcoma.

Enhanced bioavailability of sirolimus via preparation of solid dispersion nanoparticles using a supercritical antisolvent process

Background

The aim of this study was to improve the physicochemical properties and bioavailability of poorly water-soluble sirolimus via preparation of a solid dispersion of nanoparticles using a supercritical antisolvent (SAS) process.

Methods

First, excipients for enhancing the stability and solubility of sirolimus were screened. Second, using the SAS process, solid dispersions of sirolimus-polyvinylpyrrolidone (PVP) K30 nanoparticles were prepared with or without surfactants such as sodium lauryl sulfate (SLS), tocopheryl propylene glycol succinate, Sucroester 15, Gelucire 50/13, and Myrj 52. A mean particle size of approximately 250 nm was obtained for PVP K30-sirolimus nanoparticles. Solid state characterization, kinetic solubility, powder dissolution, stability, and pharmacokinetics were analyzed in rats.

Results

X-ray diffraction, differential scanning calorimetry, and high-pressure liquid chromatography indicated that sirolimus existed in an anhydrous amorphous form within a solid dispersion of nanoparticles and that no degradation occurred after SAS processing. The improved supersaturation and dissolution of sirolimus as a solid dispersion of nanoparticles appeared to be well correlated with enhanced bioavailability of oral sirolimus in rats. With oral administration of a solid dispersion of PVP K30-SLS-sirolimus nanoparticles, the peak concentration and AUC_0→12h of sirolimus were increased by approximately 18.3-fold and 15.2-fold, respectively.

Conclusion

The results of this study suggest that preparation of PVP K30-sirolimus-surfactant nanoparticles using the SAS process may be a promising approach for improving the bioavailability of sirolimus.

Long-term effectiveness and safety of sirolimus drug-eluting stents

The root cause of coronary artery disease is atherosclerosis, ie, intraluminal narrowing (stenosis) of the arteries that supply blood to tissues of the heart. The introduction of the drug-eluting stent over the past decade has revolutionized the field of interventional cardiology. It is used extensively in clinical practice for the treatment of coronary artery disease. The first drug-eluting stent to receive US Food and Drug Administration approval was the sirolimus-eluting stent. Recently, two other stent analogs of sirolimus were approved, ie, the zotarolimus-eluting stent and the everolimus-eluting stent. However, concern has arisen in recent years about the long-term safety and efficacy of drug-eluting stents, due to the occurrence of late adverse clinical events, such as stent thrombosis. This review focuses on clinical studies that have been performed with the sirolimus-eluting stent or its analogs. We discuss the pharmacology, safety, and various therapeutic options that exist when choosing stents for coronary artery disease. Our aim is to provide a thorough review of the long-term efficacy and safety of sirolimus drug-eluting stents, and also to discuss currently approved and promising investigational drug-eluting stents, in an effort to provide insight into how these stents are currently evolving and generate further investigation in this area.

Skin cancer in transplant recipients, out of the woods. Scientific retreat of the ITSCC and SCOPE

The International Transplant Skin Cancer Collaborative (ITSCC) is an organization of more than 300 members dedicated to the study and care of skin changes that develop in solid-organ transplant recipients. This group of medical and surgical dermatologists, transplant surgeons and basic science researchers was formed to better understand the basic science of transplant dermatology, and to work collaboratively to address the clinical challenges in this patient population. Transplant patients have an ∼100-fold increased risk of developing cutaneous squamous cell carcinoma than the general population and are also at an increased risk of developing basal cell carcinoma, melanoma, Merkel cell carcinoma and Kaposi's sarcoma. In October 2010, ITSCC and its European counterpart Skin Care in Organ Transplant Patients Europe (SCOPE) held a joint biennial 4-day scientific retreat in the woods near Essex, Massachusetts. In this meeting report we provide an up-to-date distillation of the novel findings presented in the 21 oral abstracts, at the tumor board and within the working groups.

Transplant-associated thrombotic microangiopathy in pediatric patients treated with sirolimus and tacrolimus

BACKGROUND

Transplant-associated thrombotic microangiopathy (TMA) syndromes are reported to occur with increased frequency in transplant patients treated with siroliumus combined with a calcineurin inhibitor. We performed a retrospective study of all pediatric transplant patients at City of Hope who were administered combined tacrolimus/sirolimus (TAC/SIR) to determine the occurrence of TMA.

PROCEDURE

This analysis includes 41 consecutive patients between the ages of 2 and 20 (median age 9.1) who received an allogeneic hematopoietic stem cell transplant from any source and also received TAC/SIR for prevention or treatment of GVHD. Of those 41 patients, 20 received TAC/SIR as GVHD prohpylaxis and were designated the preventative group (PG), while 21 received TAC/SIR as treatment for GVHD and were designated the therapy group (TG). TMA occurrence in both groups was documented from day -1 of transplant to day 60 for the PG, and until 30 days after last dose for the TG. TMA was defined according to 2005 consensus criteria.

RESULTS

Five of twenty patients in the PG, and five of twenty one in the TG, experienced TMA, with an overall rate of 23.8% for the population. All ten patients with TMA showed elevated levels of TAC, SIR or both and nine of ten suffered from organ injury due to regimen-related toxicity or GVHD.

CONCLUSION

Physicians should exercise caution in the use of TAC/SIR in pediatric patients due to a high rate of TMA. It is not recommended for heavily pre-treated patients and peak levels of TAC/SIR must be very carefully controlled.

A phase I study of sirolimus and bevacizumab in patients with advanced malignancies

BACKGROUND

We performed a single institution, phase I study of sirolimus and bevacizumab, in order to determine the dose limiting toxicity (DLT) and recommended phase II doses.

PATIENTS AND METHODS

Eligible patients had previously treated advanced malignancies and were enrolled in three cohorts. Sirolimus 90 mg PO weekly (45 mg on days 1 and 2) was combined with bevacizumab 7.5mg/kg (cohort #1) or bevacizumab 15 mg/kg (cohort #2) IV q3weeks. Sirolimus 4 mg PO daily was combined with bevacizumab 15 mg/kg IV q3weeks (cohort #3).

RESULTS

Twenty-eight patients enrolled. The most common tumour types were colorectal (21%), head/neck (14%), and renal cell (11%). No DLTs were observed in cohorts #1 (4 patients) and #2 (12 patients), while two DLTs (grade 3 confusion and grade 3 fatigue) were observed in the first six patients in cohort #3 (12 patients). The most common grade 3 toxicities were fatigue (18%), hypertension (14%) and anorexia (11%). There were no responses, but one patient has had stable disease for 78 weeks.

CONCLUSIONS

The combination of sirolimus and bevacizumab at full doses is tolerable in the majority of patients. The availability and cost of sirolimus compared with other mTOR inhibitors make this an attractive agent to combine with bevacizumab.

New onset diabetes after transplantation (NODAT): an overview

Although renal transplantation ameliorates cardiovascular risk factors by restoring renal function, it introduces new cardiovascular risks including impaired glucose tolerance or diabetes mellitus, hypertension, and dyslipidemia that are derived, in part, from immunosuppressive medications such as calcineurin inhibitors, corticosteroids, or mammalian target of rapamycin inhibitors. New onset diabetes mellitus after transplantation (NODAT) is a serious and common complication following solid organ transplantation. NODAT has been reported to occur in 2% to 53% of all solid organ transplants. Kidney transplant recipients who develop NODAT have variably been reported to be at increased risk of fatal and nonfatal cardiovascular events and other adverse outcomes including infection, reduced patient survival, graft rejection, and accelerated graft loss compared with those who do not develop diabetes. Identification of high-risk patients and implementation of measures to reduce the development of NODAT may improve long-term patient and graft outcome. The following article presents an overview of the literature on the current diagnostic criteria for NODAT, its incidence after solid organ transplantation, suggested risk factors and potential pathogenic mechanisms. The impact of NODAT on patient and allograft outcomes and suggested guidelines for early identification and management of NODAT will also be discussed.

Strategies to prevent EBV reactivation and posttransplant lymphoproliferative disorders (PTLD) after allogeneic stem cell transplantation in high-risk patients

Epstein-Barr virus (EBV)-associated postallogeneic stem cell transplantation (SCT) lymphoproliferative disorder (PTLD) is often life threatening. The risk of EBV reactivation is highest in older patients, T cell-depleted SCT (in vivo or vitro), and in unrelated or mismatched SCT. Cumulative numbers of patients with EBV reactivation and PTLD are rising as more patients at high risk for EBV reactivation and PTLD are receiving allo-SCT. Novel but easily applicable strategies are needed to prevent EBV reactivation and PTLD to serve the needs of the increasingly enlarging population of high-risk SCT recipients across the globe.

Two drug interaction studies of sirolimus in combination with sorafenib or sunitinib in patients with advanced malignancies

PURPOSE

Sirolimus is the prototypical mTOR inhibitor. Sorafenib and sunitinib are small molecule inhibitors of multiple kinases including VEGF receptor (VEGFR) kinases. These agents have different mechanisms of action, providing a strong rationale for combination.

EXPERIMENTAL DESIGN

Patients with advanced cancer were assigned to receive either sirolimus or the VEGFR inhibitor alone for a 2-week lead-in period, followed by combination therapy. The primary end point of each trial was to determine whether a drug interaction exists between sirolimus and either sorafenib or sunitinib, as defined by a difference in C(max) for each drug alone compared with its C(max) during combination therapy.

RESULTS

The sorafenib and sunitinib trials enrolled 34 and 23 patients, respectively. There were no clinically significant differences in C(max) for any of the drugs alone compared with the C(max) during combination therapy. Toxicity profiles were similar to those expected for each drug alone. One patient with adrenal cortical cancer had a partial response to sirolimus and sunitnib.

CONCLUSIONS

Sirolimus can be safely combined with sorafenib or sunitinib. Our trial design is feasible and informative in screening for potential drug-drug interactions, using a relatively small number of patients and limited pharmacokinetic sampling.

The effects of sirolimus on target organs during mesenteric ischemia and reperfusion damage in an experimental rat model

BACKGROUND

Mesenteric ischemia and reperfusion (I/R) syndrome (MIRS) has been considered a clinicopathologic entity associated with a variety of clinically severe conditions with decreased intestinal blood flow and has been known to induce I/R damage in various organs. Sirolimus (SRL), a macrolide antibiotic isolated from a strain of Streptomyces hygroscopicus, is a potent and nonnephrotoxic immunosuppressant.

OBJECTIVE

This study was designed to investigate the potential impact of sirolimus on MIRS-induced I/R damage in renal, intestinal, pulmonary, and hepatic tissues in an experimental rat model.

METHODS

Twenty-four male Sprague-Dawley rats, aged 6 to 8 weeks and weighing 280 (±20 g), were studied. Using computer-generated random numbers, rats were assigned to 1 of the following 3 groups: group 1 (I/R group, n = 8), group 2 (I/R + sirolimus group, n = 8), and group 3 (control group, n = 8). Sirolimus, in a 1 mg/mL (60 mL) solution, was administered intraperitoneally in a dose of 1.5 mg/kg/d to the rats assigned to group 2 starting from 3 days before the surgical procedure. In surgery, a laparotomy was performed to clamp the superior mesenteric artery and, thus, induce bowel ischemia in groups 1 and 2. After 60 minutes of ischemia, the microvascular clamp on the superior mesenteric artery was removed for 3 hours of reperfusion. Soon after experimental induction of MIRS, bowel, lung, kidney, and liver specimens from each animal were harvested for both biochemical and histopathologic analysis.

RESULTS

There were statistically significant differences between groups 1 and 3 with regard to degrees of intestinal (P < 0.001), hepatic (P = 0.001), renal (P < 0.001), and pulmonary (P = 0.01) I/R damage. The lung specimens from group 2 had less inflammation and perivascular edema formation compared with specimens from group 1, but no statistical significance was observed between the groups (P < 0.33). There were statistically significant differences between groups 1 and 2 with regard to degrees of intestinal, hepatic, and renal I/R damage (P = 0.001 for all).

CONCLUSION

The findings of the present study demonstrate the attenuating effects of sirolimus on I/R damage in the intestine and remote organs, including the liver and kidney in the setting of MIRS in an experimental rat model. As a therapeutic implication, the utility of sirolimus may be of clinical value in procedures associated with a high likelihood of I/R damage, including major abdominal operations and renal transplantation. However, whether these results apply to humans is unclear. Additional experimental and clinical studies are warranted to confirm the clinical utility of sirolimus in conditions potentially associated with I/R damage.

Intestinal transplantation in children: a review of immunotherapy regimens

This review summarizes the outcomes and known adverse effects of current immunosuppression strategies in use in pediatric intestinal transplantation. Intestinal transplantation has evolved from an experimental therapy to a highly successful treatment for children with intestinal failure who have complications with total parenteral nutrition. Because of continued success with intestinal transplantation over the past decade, the focus of clinicians and researchers is shifting from short-term patient survival to optimizing long-term outcomes. Current 5-year patient and graft survival rates after intestinal transplantation are 58% and 40%, respectively, in the US; single centers have reported nearly 80% patient and 60% graft survival rates at 5 years. The immunosuppression strategy in intestinal transplantation includes a tacrolimus-based regimen, usually in conjunction with an antibody induction therapy such as rabbit-antithymocyte globulin, interleukin-2 receptor antagonists, or alemtuzumab. The use of these immunosuppressive regimens, along with improved medical and surgical care, has contributed significantly toward improved outcomes. Optimization of post-transplant immunosuppression strategies to reduce adverse effects while minimizing acute and chronic graft rejection is a strong clinical and research focus.