Process Optimization to Improve Immunosuppressant Drug Testing Turnaround Time

OBJECTIVES

Timely reporting of immunosuppressant (ISP) drug level results is needed for transplant patient management. This study characterized the local ISP testing process, identified bottlenecks and implemented process improvements to meet turnaround time requirements.

METHODS

Laboratory information time stamps, direct observation and discussion with staff were used to construct a value stream map of the ISP testing process to identify process bottlenecks. Improvements were implemented to attain the required turnaround time.

RESULTS

Baseline performance of the existing ISP process (seven weeks, n = 272 samples) indicated that only 28% of samples were reported by 2:00 pm Major bottlenecks were identified to be the analytical run schedule, instrument delays, difficulty identifying ISP samples at intake, and difficulty collecting specimens. Process changes resulted in a median of 76% samples reported by 2:00 pm

CONCLUSIONS

: Adjusting ISP collection and analysis processes improved the laboratory's ability to meet physician requested result reporting time of 2:00 pm.

Treatment with Tacrolimus and Sirolimus Reveals No Additional Adverse Effects on Human Islets In Vitro Compared to Each Drug Alone but They Are Reduced by Adding Glucocorticoids

Tacrolimus and sirolimus are important immunosuppressive drugs used in human islet transplantation; however, they are linked to detrimental effects on islets and reduction of long-term graft function. Few studies investigate the direct effects of these drugs combined in parallel with single drug exposure. Human islets were treated with or without tacrolimus (30 μg/L), sirolimus (30 μg/L), or a combination thereof for 24 hrs. Islet function as well as apoptosis was assessed by glucose-stimulated insulin secretion (GSIS) and Cell Death ELISA. Proinflammatory cytokines were analysed by qRT-PCR and Bio-Plex. Islets exposed to the combination of sirolimus and tacrolimus were treated with or without methylprednisolone (1000 μg/L) and the expression of the proinflammatory cytokines was investigated. We found the following: (i) No additive reduction in function and viability in islets existed when tacrolimus and sirolimus were combined compared to the single drug. (ii) Increased expression of proinflammatory cytokines mRNA and protein levels in islets took place. (iii) Methylprednisolone significantly decreased the proinflammatory response in islets induced by the drug combination. Although human islets are prone to direct toxic effect of tacrolimus and sirolimus, we found no additive effects of the drug combination. Short-term exposure of glucocorticoids could effectively reduce the proinflammatory response in human islets induced by the combination of tacrolimus and sirolimus.

A new system to evaluate the influence of immunosuppressive drugs on pancreatic islets using epigenetic analysis in a 3-dimensional culture

OBJECTIVE

The present study aimed to establish a new method to evaluate the influence of immunosuppressive drugs on pancreatic islets in short-term in vitro cultures using epigenetic analysis in a 3-dimensional culture.

METHODS

For this purpose, we selected (a) a 3-dimensional culture system utilizing thermoreversible gelation polymer, (b) pancreatic duodenal homeobox-1 (pdx-1)-Venus transgenic pigs expressing the green fluorescent protein, (c) FK506 as an immunosuppressive drug of the evaluation, and (d) the bisulfite sequencing technique to evaluate the methylation levels of pdx-1 and insulin genes. Each isolated pancreatic islet was cultured with several doses of FK506. The viability of the each islet was evaluated by analyzing the emission of Venus in real time and by propidium iodide staining. Epigenetic analysis was performed at several time points.

RESULTS

Each single pancreatic islet was stably cultured for 30 days in this system. At day 30 in culture, we observed that insulin DNA methylation levels in the group that received a high dose of FK506 dramatically increased, although there was no change in pdx-1 DNA methylation level and configuration of the islets.

CONCLUSIONS

Our system may be useful to determine immunosuppressive drugs that are specifically suitable for islet transplantation.

Different effects of FK506, rapamycin, and mycophenolate mofetil on glucose-stimulated insulin release and apoptosis in human islets

Pancreatic islet transplantation has the potential to be an effective treatment for type 1 diabetes mellitus. While recent improvements have improved 1-year outcomes, follow-up studies show a persistent loss of graft function/survival over 5 years. One possible cause of islet transplant failure is the immunosuppressant regimen required to prevent alloimmune graft rejection. Although there is evidence from separate studies, mostly in rodents and cell lines, that FK506 (tacrolimus), rapamycin (sirolimus), and mycophenolate mofetil (MMF; CellCept) can damage pancreatic beta-cells, there have been few side-by-side, multiparameter comparisons of the effects of these drugs on human islets. In the present study, we show that 24-h exposure to FK506 or MMF impairs glucose-stimulated insulin secretion in human islets. FK506 had acute and direct effects on insulin exocytosis, whereas MMF did not. FK506, but not MMF, impaired human islet graft function in diabetic NOD*scid mice. All of the immunosuppressants tested in vitro increased caspase-3 cleavage and caspase-3 activity, whereas MMF induced ER-stress to the greatest degree. Treating human islets with the GLP-1 agonist exenatide ameliorated the immunosuppressant-induced defects in glucose-stimulated insulin release. Together, our results demonstrate that immunosuppressants impair human beta-cell function and survival, and that these defects can be circumvented to a certain extent with exenatide treatment.

Mechanisms of Pharmacokinetic and Pharmacodynamic Drug Interactions Associated with Ritonavir-Enhanced Tipranavir

Tipranavir is a nonpeptidic protease inhibitor that has activity against human immunodeficiency virus strains resistant to multiple protease inhibitors. Tipranavir 500 mg is coadministered with ritonavir 200 mg. Tipranavir is metabolized by cytochrome P450 (CYP) 3A and, when combined with ritonavir in vitro, causes inhibition of CYP1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A in addition to induction of glucuronidase and the drug transporter P-glycoprotein. As a result, drug-drug interactions between tipranavir-ritonavir and other coadministered drugs are a concern. In addition to interactions with other antiretrovirals, tipranavir-ritonavir interactions with antifungals, antimycobacterials, oral contraceptives, statins, and antidiarrheals have been specifically evaluated. For other drugs such as antiarrhythmics, antihistamines, ergot derivatives, selective serotonin receptor agonists (or triptans), gastrointestinal motility agents, erectile dysfunction agents, and calcium channel blockers, interactions can be predicted based on studies with other ritonavir-boosted protease inhibitors and what is known about tipranavir-ritonavir CYP and P-glycoprotein utilization. The highly complex nature of drug interactions dictates that cautious prescribing should occur with narrow-therapeutic-index drugs that have not been specifically studied. Thus, the known interaction potential of tipranavir-ritonavir is reported, and in vitro and in vivo data are provided to assist clinicians in predicting interactions not yet studied. As more clinical interaction data are generated, better insight will be gained into the specific mechanisms of interactions with tipranavir-ritonavir.

Pharmacokinetic evaluation of mycophenolic acid profiles during the period immediately following an orthotopic liver transplant

BACKGROUND

Area under the curve (AUC) limited sampling strategies have been proposed to improve the efficiency of mycophenolic acid (MPA), treatment of the transplanted patient. Our objective was to develop a model in the initial phase of the transplantation that explains the variability in the pharmacokinetic behavior of MPA in the immediate posttransplant period, following treatment with mycophenolate mofetil (MMF) in adult liver transplantation.

METHODS

One hundred ten pharmacokinetic simplified sampling profiles were collected, including four samples over a 6-hour postdose interval, in over 60 patients treated with cyclosporine or tacrolimus, MMF, and steroids, combining Daclizumab in more than a third of the patients. For an enzyme-multiplied immunoassay technique method was established for MPA estimates. The correlation between the AUC and the plasma concentration points was established using a multiple linear regression with various equations for three different pharmacokinetic groups.

RESULTS

The maximum mean values of MPA AUC and predose concentration (C0h) (20.8 +/- 11.8 and 2.3 +/- 1.8, respectively) were reached on the third day. The single sample showing the greatest correlation with the MPA AUC was the one collected after 3 hours (r(2) = 0.575); 59.1% of profiles displayed a single peak with more than half showing a tmax >/= 3 hours.

CONCLUSIONS

This profile analysis during the first few weeks highlighted the problems in determining therapeutic targets. Profiles showing a double peak revealed the marked influence of the enterohepatic cycle on MPA concentrations during the initial phase.

Sirolimus: the evidence for clinical pharmacokinetic monitoring

This review seeks to apply a decision-making algorithm to establish whether clinical pharmacokinetic monitoring (CPM) of sirolimus (rapamycin) in solid organ transplantation is indicated in specific patient populations. The need for CPM of sirolimus, although a regulatory requirement in Europe, has not yet been firmly established in North America and other parts of the world. Sirolimus has demonstrated immunosuppressive efficacy in renal, pancreatic islet cell, liver and heart transplant recipients. The pharmacological response of immunosuppressive therapy with sirolimus cannot be readily evaluated; however, a relationship between trough blood sirolimus concentrations, area under the plasma concentration-time curve (AUC) and the incidence of rejection has been proposed. Furthermore, sirolimus can be measured in whole blood by several assays--high-performance liquid chromatography with detection by tandem mass spectrometry, or with ultraviolet detection, radioreceptor assay or microparticle enzyme immunoassay. Both experimental animal and clinical data suggest that adverse events and their associated severity are correlated with blood concentrations. To prevent rejection and minimise toxicity, a therapeutic range of 4-12 microg/L (measured via chromatographic assays) is recommended when sirolimus is used in conjunction with ciclosporin. If ciclosporin therapy is discontinued, a target trough range of 12-20 microg/L is recommended. Sirolimus pharmacokinetics display large inter- and intrapatient variability, which may change in specific patient populations due to disease states or concurrent immunosuppressants or other interacting drugs. Due to the long half-life of sirolimus, dosage adjustments would ideally be based on trough levels obtained more than 5-7 days after initiation of therapy or dosage change. Once the initial dose titration is complete, monitoring sirolimus trough concentrations weekly for the first month and every 2 weeks for the second month appears to be appropriate. After the first 2 months of dose titration, routine CPM of sirolimus is not necessary in all patients, but may be warranted to achieve target concentrations in certain populations of patients, but the frequency of further monitoring remains to be determined and should be individualised.