Specific enzyme-multiplied immunoassay and fluorescence polarization immunoassay for cyclosporin compared with Cyclotrac [125I]radioimmunoassay

Lack of effects on lymphocyte function from chronic topical ocular cyclosporine medication: a prospective study

AIM

Topical cyclosporine has been widely used in the treatment of canine keratoconjunctivitis sicca without apparent documented clinical side effects. Thus the finding of reduced lymphocyte proliferation in animals treated with the drug at a concentration of 2% was both surprising and concerning. This study aimed to repeat the previous study and to compare the systemic effects of 2% cyclosporine in corn oil and 0.2% topical cyclosporine ointment (Optimmune, Intervet-Schering Plough, Welwyn, UK).

METHODS

Twenty dogs treated with Optimmune or with topical 2% cyclosporine in corn oil where previous treatment with Optimmune had failed were included in this study. Blood samples were taken at the time of first evaluation and at 1, 3 and 6 months of treatment to provide a biochemical and hematological health evaluation of the dogs and at each examination to measure circulating levels of cyclosporine and to obtain a lymphocyte population with which to determine a mitogen stimulation index (MSI) on treatment with phytohaemagglutinin-P (PHA) and conconavlin A (con-A). Levels of circulating cyclosporine were measured with an enzyme-multiplied immunoassay method and also the more sensitive quantification technique of mass spectroscopy (MS).

RESULTS

No blood samples contained over 15 ng/ml cyclosporine, the lower limit of detection using the radioimmunoassay or the enzyme-multiplied immunoassay technique. Positive control samples taken from dogs treated with oral cyclosporine for anal furunculosis showed measurable levels in blood, demonstrating that the technique worked. Mean MSI values at 0, 1, 3 and 6 months of treatment were 10.2, 11.4, 11.6, and 10.5 for dogs treated with 0.2% cyclosporine and 10.4, 11.9, 11.7, and 12.9 for dogs treated with 2% cyclosporine. Mitogen stimulation index values were not statistically different between the first examination and any subsequent examination time-point.

CONCLUSIONS

The findings of the study contradict those of the previous studies. No change in lymphocyte stimulation index was noted, neither were significant blood levels of cyclosporine documented after topical administration of either 0.2% or 2% cyclosporine. This study shows that topical cyclosporine is safe to use in the canine eye in line with the drug's safety record in this therapeutic regime over the past 20 years since its first use.

Absence of pharmacokinetic interference of moxifloxacin on cyclosporine and tacrolimus in kidney transplant recipients

This study investigates the potential pharmacokinetic interactions between an antimicrobial agent, moxifloxacin, and 2 immunosuppressant drugs, cyclosporine and tacrolimus, in kidney transplant recipients. Twenty-two kidney transplant patients needing antibiotic therapy for urinary tract infections are enrolled. Eleven patients are under cyclosporine treatment and the other 11 patients are under tacrolimus treatment. Because the urinary tract infections are caused by gram-negative aerobes sensitive to moxifloxacin, this antibiotic is administered by oral route at a dose of 400 mg/d for 1 week; in each patient pharmacokinetic studies are carried out before and at the seventh day of therapy. For both immunosuppressors, none of the pharmacokinetic parameters investigated show statistically significant differences between values obtained before and during treatment with moxifloxacin. In fact, the concentration-time profiles of monoclonal cyclosporine, polyclonal cyclosporine, and tacrolimus are not significantly different before and during the antimicrobial therapy. The results of the present study rule out interference of moxifloxacin with both cyclosporine and tacrolimus kinetics and indicate that the concomitant administration of the fluoroquinolone and cyclosporine or tacrolimus does not require modifications of the dosages of 2 immunosuppressant drugs.

Cyclosporin monitoring in Australasia: 2002 update of consensus guidelines

Therapeutic drug monitoring of cyclosporin (CsA) has been established as part of the routine clinical treatment of patients following organ transplantation for more than 20 years, and based on contemporary knowledge, many consensus guidelines have been published to assist clinics and laboratories attain optimal strategies for patient care. This article addresses the newer directions in CsA monitoring, with particular reference to the Australasian situation that has evolved since the 1993 Australasian guideline. These changes have included the introduction of alternative assay methodologies, changed CsA formulation from Sandimmun to Neoral throughout Australasia, and alternatives to trough concentration (C0) monitoring, especially 2-hour concentration (C2) monitoring and associated validated dilution protocols to accurately quantitate the higher whole blood CsA concentrations. The revision was prepared following a recent survey of all Australasian CsA-monitoring laboratories where discordant practices were evident.

Comparison of trough, 2-hour, and limited AUC blood sampling for monitoring cyclosporin (Neoral) at day 7 post-renal transplantation and incidence of rejection in the first month

The use of alternative strategies to the traditional pre-dose/trough (C0) blood sampling for cyclosporine (CsA) therapeutic drug monitoring has the potential to revolutionize analytical practices which have, in many centers, been established for some 20 years. While the C0 sample has previously been recommended, current attitudes are increasingly proposing alternatives for assessing CsA exposure, including various limited sampling strategies of the AUC (lssAUC) in the early postdose period, or alternative single-point nontrough samples, such as a 2-hour postdose sample (C2). The present study has reviewed a series of consecutive renal transplant recipients over 18 months where CsA was the primary immunosuppressant. The lssAUC performed at around day 7 posttransplantation included drawing blood at 0, 2, and 4 hours postdose, giving AUC(0-4). The aim of this study was to review the occurrence of acute biopsy-proven rejection in the first month and consider which of (simultaneously measured) C0, C2 or AUC(0-4) was a better early indicator of this adverse outcome. The result was best described by comparing the data from rejectors (n = 13) and nonrejectors (n = 42) for these 3 indices of CsA exposure (i.e., C0, C2 or AUC(0-4)). There was no evidence that C0 predicted the likelihood of such adverse clinical outcomes. In contrast, rejectors tended to have lower mean C2 CsA concentrations, and the incidence of rejection was 0.0 when C2 exceeded 1200 microg/L (n = 10). While the data are limited in the higher C2 CsA concentration range, it is nevertheless consistent with more recent recommendations suggesting that the CsA at C2 should target 1700 microg/L in this first month posttransplantation. As 64% of the patients were also receiving a CsA-sparing agent (diltiazem [DTZ]), the relationships were also investigated to determine whether any affect of concomitant DTZ therapy could be demonstrated. However, in this small sample, no significant affect of DTZ was seen.

Cyclosporin assays, metabolite cross-reactivity, and pharmacokinetic monitoring

The range of cyclosporin (CsA) immunoassays has become the mainstay in many therapeutic drug monitoring laboratories for delivering CsA concentration data to support clinical care of patients after transplantation. However, these assays have been criticized because of the varying degree of CsA-metabolite interferences that introduce analytical errors. The introduction of another such CsA assay (on the AXSyM analyzer) has been considered, as the manufacturer has represented it as having a low CsA-metabolite cross-reactivity profile compared with chromatographic methods. A case is presented to question how this apparent result was obtained in view of the method using the same antibody as another CsA method from the same manufacturer (fluorescence polarizaton immunoassay on the TDx analyzer) which is well known to have poor performance in regard to CsA-metabolite cross-reactivity. The implications for this problem may be even more serious as more patients are monitored using the CsA AUC strategies, rather than the traditional trough concentration approach. Such issues reinforce the need for the clinical laboratory to be critical of methods offered commercially based on scientific/pharmacologic skills.

Reducing the cost of cyclosporin assays: modification of the EMIT 2000 method

Cyclosporin is the leading immunosuppressant agent in organ transplantation, and therapeutic drug monitoring forms an integral part of patient management in most institutions. In the authors' laboratory, the cost of cyclosporin assays represents a major fraction of total consumable expenditure. At present, an average of 4,300 patient cyclosporin assays are performed annually using the EMIT 2000 method (Behring-Syva) on the Cobas Mira analyser (Roche), at a cost of AUD$50,000 in kits alone. As a means of reducing laboratory costs, the manufacturer's recommended method was modified by decreasing all of the reagent and sample volumes in the "Analytical" section of the Cobas Mira cyclosporin programme by 33%. Assay performance was monitored over a 10-month period and compared to that of the unmodified method. Calibration curves were stable, requiring a one-point correction on average of once every 12 days, and a full calibration once ever 1.7 months. Interassay variability was not different to that previously reported for the unchanged method, with mean (SD, CV) concentrations for trilevel quality control specimens of 86.5 micrograms/L (10.2, 11.9%), 185.9 micrograms/L (11.4, 6.2%) and 408.5 micrograms/l (28.9, 7.1%). From 24 specimens assayed in an international quality assurance programme, the results of 23 were within 1.2 SD of the group mean for the EMIT method, with an average bias of 0.8%. With the current modifications, we were able to perform an average of 105 patient assays per kit compared to the previous 71, equating to an annual saving the AUD$16,600.

Target concentration strategy for cyclosporin monitoring

The target concentration concept has been proposed as a potential alternative to the established, and probably much abused, therapeutic range method of interpreting concentrations of therapeutic drugs in plasma, serum or blood when individualising drug dosages. This paper raises for debate the possibility of extending this alternative concept to immunosuppressant monitoring with cyclosporin, where there has been considerable difficulty in establishing therapeutic ranges which are widely accepted and applied. In its broader application, the target concentration strategy does present advantage to the clinician in precision, ability to calculate the dose directly from the target concentration and clearance, as well as a clearer concept of an optimal concentration (differentiating desired and adverse effects).

The EMIT Cyclosporine Assay: development of application protocols for the Boehringer Mannheim Hitachi 911 and 917 analyzers

OBJECTIVE

The purpose of this work was to develop applications for the EMIT Cyclosporine (CsA) Assay on the Hitachi 911 and 917 analyzers.

METHODS AND RESULTS

Instrument settings were optimized to arrive at the following assay characteristics on the Hitachi 917. Limit of sensitivity was 50 micrograms/L. Intra-assay coefficients of variation (CV) were 8.1% (n = 20; mean = 62 micrograms/L) and 4.2% (n = 20; mean = 315 micrograms/L), while interassay CVs were 13.0% (n = mean = 73 micrograms/L) and 5.7% (n = 43; mean = 391 micrograms/L). Recoveries of 95-104% were obtained by spiking aliquots of 3 whole blood patient pools of known CsA concentrations with CsA. Serial dilutions of 3 patient specimens demonstrated linear relationships between expected and actual CsA concentrations (r = 0.99, 0.99, 0.98; regression lines: y = 1.19x -17.1; y = 0.75x + 18.0; y = 1.01x + 3.7). Specimen carryover was not evident. Calibration stability is at least 10 days. Comparable assay characteristics were found for the Hitachi 911. Sequentially-collected trough whole blood specimens from renal (n = 3), liver (n = 3) and heart (n = 4) transplant patients prescribed CsA were collected up to 78 days post-transplant and analyzed by EMIT on the Hitachi 917 and also by fluorescence polarization immunoassay (FPIA) and high performance liquid chromatography (HPLC). The following linear regression equations were produced for the renal [EMIT = 0.801 (TDx) + 4.98, r = 0.91, Sy/x = 32, n = 37; EMIT = 0.877 (HPLC) + 56, r = 0.87, Sy/x = 38, n = 37]; liver [EMIT = 0.808 (TDx) - 27, r = 0.94, Sy/x = 42, n = 37; EMIT = 0.953 (HPLC) + 44, r = 0.89, Sy/x = 57, n = 37] and heart [EMIT = 0.820 (TDx) - 24, r = 0.94, Sy/x = 31, n = 45, EMIT = 0.956 (HPLC) + 54, r = 0.91, Sy/x = 38, n = 45] patient samples. FPIA values average 32% more than EMIT-derived CsA concentrations on the Hitachi 917, which in turn averaged 15% more than HPLC values. In addition, these levels were compared intra-individually. CsA concentrations within all patients were significantly higher (p < 0.05, paired t-test) by FPIA compared to EMIT and by FPIA compared to HPLC. Although CsA concentrations within most patients were significantly higher (p < 0.05) by EMIT compared to HPLC, levels determined in 4 transplant patients (1 renal, 1 liver, 2 heart) were not different.

CONCLUSION

Development of applications for the EMIT CsA Assay on two highly automated, random access instruments, the Hitachi 911 and Hitachi 917, enhances the versatility of the immunoassay for routine therapeutic drug monitoring of this immunosuppressant in the clinical setting.

Noninterchangeability of specific radioimmunoassay and monoclonal antibody fluorescent polarization immunoassay in cyclosporine measurements

This study compares cyclosporine (CsA) concentrations in whole blood from patients receiving bone marrow (n = 10), renal (n = 48), heart (n = 50) or liver (n = 50) transplants, as measured by monoclonal antibody flurorescence polarization immunoassay (FPIA) and specific 125I-radioimmunoassay (RIA). The FPIA overestimated CsA by an average of 25%. Results were higher for all indications: FPIA/RIA ratios were 1.17 for bone marrow, 1.23 for renal and 1.27 for both heart and liver transplants, and these values were significantly different from 1.0. The percentage of overestimation was higher at low CsA concentrations (< or = 100 micrograms/L) than at high CsA concentrations (> or = 400 micrograms/L). In all indications, results by both methods correlated well (r > 0.96) but slopes and intercepts were different from 1.0 and 0.0, respectively, and these parameters varied greatly between the grafted populations. These findings obtained with the two methods could not be attributed to matrix effect because the mean FPIA/RIA ratio for spiked control samples was 1.0. The discrepancy between the FPIA and RIA could be explained by the lower specificity of the monoclonal antibody contained in the FPIA kit. These results suggest that FPIA is not as accurate as RIA and that the two methods are not interchangeable in CsA level measurement.

The use of therapeutic drug monitoring to optimise immunosuppressive therapy

Most experience of the therapeutic drug monitoring of immunosuppressive agents has been acquired in the field of solid organ transplantation; however, agents such as cyclosporin (cyclosporin A) are being increasingly utilised for the management of autoimmune diseases. Cyclosporin is the most widely studied immunosuppressant, but in spite of this many controversies still exist as to the optimum strategy for monitoring this drug. Owing to its widely variable pharmacokinetics and metabolism, and the absence of a simple method to measure therapeutic effectiveness, many factors should be considered. In most circumstances, measuring whole blood through concentrations of cyclosporin with a specific assay methodology is warranted. In addition, knowledge of other factors that may alter the pharmacokinetics (such as liver function, concomitant food or medications, gastrointestinal status, and time since transplantation) should be taken into account so that therapy can be appropriately adjusted. Other methods of monitoring have been investigated, such as AUC (area under the concentration-time curve) monitoring and immunological monitoring. However, further refinement of these techniques and greater experience with their efficacy must be accumulated before their role in the monitoring of cyclosporin can be defined. Tacrolimus, like cyclosporin, shares many of the difficulties in monitoring for efficacy and toxicity due largely to the variable pharmacokinetics; similarly to cyclosporin, whole blood through concentration monitoring should be utilised in combination with knowledge of the factors that may affect the pharmacokinetics. Muromonab CD3 (OKT3) is a monoclonal antibody used for the treatment and prophylaxis of acute allograft rejection. Several immunological monitoring techniques have been investigated for this agent. Monitoring CD3+ levels can assist clinicians in determining therapeutic efficacy, while measuring antimuromonab CD3 antibody titres can help determine if xenosensitisation has occurred, causing therapeutic ineffectiveness. The clinical monitoring of azathioprine, one of the first immunosuppressive agents used in transplantation, has historically been limited to monitoring complete blood counts for bone marrow suppression. However, newer techniques measuring intracellular DNA nucleotides appear to be promising. The new immunosuppressants on the horizon include mycophenolate mofetil and rapamycin. The clinical experience with therapeutic drug monitoring of these 2 compounds is scant in the literature; however, both agents have demonstrated efficacy in preventing or treating allograft rejection while maintaining a relatively well tolerated toxicity profile in recent clinical trials. Routine monitoring does not appear to be warranted for immunosuppressive therapy in autoimmune diseases.

EMIT cyclosporine assay: development of an application protocol for Technicon AXON System

Monitoring parent drug cyclosporine (CsA) concentrations in whole blood has been facilitated by the introduction of automated nonisotopic immunoassays [fluorescence polarization monoclonal whole blood assay (FPIA), EMIT Cyclosporine Assay]. The latter assay currently has a defined application only for Cobas Mira Chemistry Systems. The purpose of our work was to develop an application for this assay on the Technicon AXON. Instrument settings were optimized to arrive at the following assay performance characteristics. Limit of sensitivity was 50 micrograms/L. Interassay coefficients of variation (CV) were 11.2% (n = 16; mean = 81 micrograms/L) and 9.4% (n = 16; mean = 418 micrograms/L). Recoveries of 102, 112, and 117% were obtained by spiking aliquots of 10 whole blood patient pools of known CsA concentrations with 50, 100, and 200 micrograms/L CsA, respectively. Serial dilutions of two patient specimens demonstrated a linear relationship between expected and actual CsA concentrations (r = 0.996, 0.998; regression lines; y = 0.989x + 11.7; y = 0.979x + 9.5). Carryover and interference (lipemia) were not evident. Instrument calibration stability is at least 1 month. Comparison with CsA concentrations analyzed in renal transplant patients by the FPIA assay produced a linear regression equation of EMIT = 1.113x - 44.5, r = 0.968, Sy/x = 20.8, n = 32. Comparison with high-performance liquid chromatography (HPLC)-derived values in the same patient population produced a linear regression equation of EMIT = 1.114x - 16.4, r = 0.970, Sy/x = 20.2. FPIA-derived CsA concentrations averaged 14.2% more than those obtained with the EMIT method with the latter averaging 1.3% more than HPLC values.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparison of cyclosporine assays using sequential samples from selected transplant patients

The monitoring of cyclosporine (CsA) whole blood concentrations is an integral part of immunosuppressive treatment with this drug. Although such monitoring has been facilitated by the introduction of monoclonal immunoassay techniques, there is a paucity of published data comparing the assays longitudinally in selected patients. The purpose of our study was to co-evaluate two monoclonal immunoassays (Cyclosporine FPIA whole blood assay, Abbott Laboratories; Cyclo-Trac SP-whole blood RIA, Incstar Inc.) and a high-performance liquid chromatography (HPLC) technique for quantitating CsA in sequentially collected trough whole blood samples from 14 patients up to 75 days after renal (n = 6), heart (n = 3), and liver (n = 5) transplantation. HPLC CsA metabolite analyses (AM1, AM9, AM4N) were performed. Although CsA concentrations within most patients were significantly higher (p < 0.05, paired t test) when measured by both immunoassay techniques compared to HPLC, levels determined in three patients, (one liver, two renal) for the FPIA/HPLC comparison and one patient (liver) for the RIA/HPLC comparison were not significantly different (p > 0.05). CsA levels within nine patients were not significantly different (p > 0.05) when FPIA and RIA were compared, but results within three patients, (one liver, two renal) were significantly higher (p < 0.05) by RIA compared to FPIA, but results within one patient (heart) were significantly higher (p < 0.05) by FPIA. Our results demonstrate first that depending on the patient, HPLC-derived CsA results are not consistently lower than results generated by immunoassay techniques and second that CsA levels obtained by FPIA are statistically equivalent or in some patients, statistically less than RIA-derived levels.