Rapid, sensitive high-performance liquid chromatographic method for the determination of cyclosporin A and its metabolites M1, M17 and M21

Cyclosporine A Loaded Electrospun Poly(D,L-Lactic Acid)/Poly(Ethylene Glycol) Nanofibers: Drug Carriers Utilizable in Local Immunosuppression

PURPOSE

The present study aims to prepare poly(D,L-lactic acid) (PLA) nanofibers loaded by the immunosuppressant cyclosporine A (CsA, 10 wt%). Amphiphilic poly(ethylene glycol)s (PEG) additives were used to modify the hydrophobic drug release kinetics.

METHODS

Four types of CsA-loaded PLA nanofibrous carriers varying in the presence and molecular weight (MW) of PEG (6, 20 and 35 kDa) were prepared by needleless electrospinning. The samples were extracted for 144 h in phosphate buffer saline or tissue culture medium. A newly developed and validated LC-MS/MS method was utilized to quantify the amount of released CsA from the carriers. In vitro cell experiments were used to evaluate biological activity.

RESULTS

Nanofibers containing 15 wt% of PEG showed improved drug release characteristics; significantly higher release rates were achieved in initial part of experiment (24 h). The highest released doses of CsA were obtained from the nanofibers with PEG of the lowest MW (6 kDa). In vitro experiments on ConA-stimulated spleen cells revealed the biological activity of the released CsA for the whole study period of 144 h and nanofibers containing PEG with the lowest MW exhibited the highest impact (inhibition).

CONCLUSIONS

The addition of PEG of a particular MW enables to control CsA release from PLA nanofibrous carriers. The biological activity of CsA-loaded PLA nanofibers with PEG persists even after 144 h of previous extraction. Prepared materials are promising for local immunosuppression in various medical applications.

Site-dependent contributions of P-glycoprotein and CYP3A to cyclosporin A absorption, and effect of dexamethasone in small intestine of mice

We examined whether the oral bioavailability of cyclosporin A is controlled primarily by P-glycoprotein (P-gp) or CYP3A in the small intestine. In situ loop method was used to evaluate the uptake of cyclosporin A (40nmol) at the upper and lower intestine of wild-type and mdr1a/1b knockout mice treated or not treated with dexamethasone (75mg/kg/day, 7 days, i.p.). Expression of CYP3A mRNA in the control group was higher in the upper than the lower intestine, while that of the multidrug resistance-1a (mdr1a) mRNA was in the opposite order. Dexamethasone administration potently induced CYP3A and mdr1a mRNAs in the lower and upper intestine, respectively. At 45min after cyclosporin A administration into an upper intestinal loop of the control group of wild-type mice, the ratio of residual cyclosporin A to dose did not differ significantly from that of mdr1a/1b knockout mice, whereas in dexamethasone-treated wild-type mice, the residual ratio was increased significantly. The ratio of the cyclosporin A metabolite M17 to cyclosporin A in portal venous blood at an upper intestinal loop of mdr1a/1b knockout mice was much higher than that a lower intestinal loop. The M17/cyclosporin A ratio of portal venous blood at a lower intestinal loop in mdr1a/1b knockout mice was increased significantly by dexamethasone treatment. These results suggest that, under physiological conditions, the oral bioavailability of cyclosporin A is mainly controlled by CYP3A in the upper intestine, rather than liver, but when P-gp is induced by steroid, the intestinal absorption of cyclosporin A may be inhibited.

Simultaneous quantitative determination of cyclosporine A and its three main metabolites (AM1, AM4N and AM9) in human blood by liquid chromatography/mass spectrometry using a rapid sample processing method

We have developed a sensitive and specific liquid chromatography/mass spectrometry (LC/MS) method for the simultaneous determination of cyclosporine A (CsA) and its three main metabolites (AM1, AM4N and AM9) in human blood. Following protein precipitation, supernatant was directly injected into the LC/MS system. Chromatographic separation was accomplished on a Symmetry C8 (4.6 x 75 mm, 3.5 microm) column with a linear gradient elution prior to detection by atmospheric pressure chemical ionization (APCI) MS using selected ion monitoring (SIM) in positive mode. This method can be applied to single mass equipment. The analytical range for each analyte was set at 1-2500 ng/mL using 100 microL of blood sample. The analytical method was fully validated according to FDA guidance. Intra-day mean accuracy and precision were 95.2-113.5% and 0.9-8.9%, respectively. Inter-day mean accuracy and precision were 95.8-107.0% and 1.5-10.7%, respectively. In blood all analytes were stable during three freeze/thaw cycles, for 24 h at room temperature and for 12 months at or below -15 degrees C. Stability was also confirmed in processed samples for 24 h at 10 degrees C and for 6 months at 4 degrees C in methanol. In addition, we confirmed the method could avoid matrix effects from transplant subjects' samples. This LC/MS technique provided an excellent method for simultaneous quantitative determination of CsA and its three metabolites for evaluation of their pharmacokinetic profiles.

Monitoring Cyclosporine of Pre-dose and Post-dose Samples Using Nonextraction Homogeneous Immunoassay

A nonextraction homogeneous immunoassay (CEDIA Cyclosporine Plus Assay) has been developed for the measurement of cyclosporine in predose (trough) and post-dose (C2 to C8) whole-blood samples. The method includes a low-range assay that measures cyclosporine from 25 to 450 ng/mL in pre-dose samples and a high-range assay that detects cyclosporine from 450 to 2000 ng/mL in post-dose samples. The high-range assay allows a direct measurement of post-dose samples without a dilution step. Alternatively, post-dose samples can be correctly measured by the low-range assay following a twofold dilution. Using an NCCLS precision protocol, the assay exhibited less than 10% CV or error less than the functional sensitivity. Functional sensitivity of the low-range assay was demonstrated at 20 ng/mL cyclosporine. Cross-reactivity was measured in the presence of cyclosporine and was found to be 4.4%, 19.8%, 16.4%, 0.9%, 1.0%, and 1.6% for metabolites AM1, AM9, AM4n, AM19, AM4n9, and AM1c, respectively. When 53 samples were evaluated using an HPLC method, the three most significant cross-reactive metabolites, AM1, AM4n, and AM9, exhibited an average concentration profile of 123%, 19%, and 0.06% of the parent cyclosporine, respectively. The average total contribution to cyclosporine quantification from these metabolites was estimated at 7.2% based on the percentage cross-reactivity of each metabolite in the CEDIA assay and the concentration of each metabolite as determined by HPLC. The method comparison study revealed a linear regression correlation of CEDIA = 1.095 x HPLC + 6.6, r = 0.972, for the low-range assay, and CEDIA = 1.018 x HPLC - 36.4, r = 0.968, for the high-range assay. In conclusion, the CEDIA Cyclosporine Plus Assay is a precise and accurate method for quantification of cyclosporine in pre-dose and post-dose samples.

Evaluation of essential parameters in the chromatographic determination of cyclosporin A and metabolites using a D-optimal design

The extensive use of routine monitoring of cyclosporin A (INN, ciclosporin) whole blood levels of patients undergoing such therapy has resulted in a wide variety of chromatographic conditions for analysing this drug. The aim of this study was to evaluate the importance of essential parameters in the chromatographic determination of cyclosporin A and its main metabolites, AM1, AM9 and AM4N. A D-optimal design was used to evaluate the effect of type and amount of organic modifier, temperature, flow rate, pH and gradient steepness. The optimal chromatographic conditions were determined by multi-linear regression. In the final chromatographic method separation of the compounds was carried out on a reversed phase C(8) column maintained at 80 degrees C. The mobile phase consisted of a linear gradient with two mobile phases containing acetonitrile and water. The flow rate was set at 0.8 ml/min. UV detection was carried out at 214 nm. Validation of the analytical method showed linearity over the range 25-1000 ng/ml (r>0.997). The detection limits of cyclosporin A, AM1, AM9 and AM4N were 1.3 pmol on column. The within-day and between-day relative standard deviations were <15% for cyclosporin A at all concentrations and for the metabolites at 250 and 1000 ng/ml, and <21% for the metabolites at limit of quantification (25 ng/ml).

High-performance liquid chromatographic analysis of cyclosporin A in rat blood and liver using a commercially available internal standard

All the available HPLC assays of cyclosporin A (CyA) use internal standards that are not commercially available. Our purpose was to develop an HPLC assay for measurements of CyA in rat blood and liver using a commercially available internal standard (I.S.). After the addition of tamoxifen (I.S.), blood (0.25 ml) or the liver homogenate (1 ml) samples were extracted into a mixture of ether:methanol (95:5). The residue after evaporation of the organic layer was dissolved in 200 microl of an injection solution and washed with 1 ml of hexane before analysis. The separation was achieved using an LC-1 column (70 degrees C) with a mobile phase of methanol-acetonitrile-0.01 M KH(2)PO(4) (50:25:25, v/v) and a flow-rate of 1 ml/min. Detection was at 205 nm. Cyclosporin A and I.S. eluted at 5 and 7 min, respectively, free from endogenous peaks. Linear relationships (r>0.98) were observed between the CyA:I.S. peak area ratios and the CyA concentrations within the range of 0.2-10 microg/ml for blood and 0.1-4 microg/ml for the liver homogenates. The intra- and inter-run C.V.s and errors for both the blood and liver samples were <15%. The extraction efficiency (n=5) was close to 100% for both CyA and I.S. in both blood and liver homogenates. The lower limit of quantitation of the assay was 0.2 or 0.1 microg/ml based on 250 microl of blood or 1 ml of liver homogenate, respectively. The assay was capable of measuring blood and liver concentrations of CyA in a rat injected intravenously with a single 5-mg/kg dose of the drug.

Competitive immunoassay for cyclosporine using capillary electrophoresis with laser induced fluorescence polarization detection

Frequent monitoring of immunosuppressive drug cyclosporine A (CsA) in blood samples of tissue transplant patients is required in clinical practice because of the narrow therapeutic range between the immunosuppressive effect and the toxic effect of this drug. We describe a competitive immunoassay capillary electrophoresis (CE) with laser induced fluorescence polarization detection method, which is rapid and sensitive for the determination of CsA. The method is based on the competitive immunochemical reaction between the analyte and fluorescent hapten (CsA*) with the antibody, CE separation of the antibody bound and free fluorescent CsA*, followed by the laser induced fluorescence polarization detection (LIFP) of the fluorescent species. The method detection limit is governed by the stability of the antibody-CsA* complex rather than by the detector noise. The use of post-column sheath flow cuvette LIFP detection resulted in excellent detection limit, typically 0.9 nM (or 9.10(-19) mol for 1 nl injection) of CsA. CsA in whole blood samples from organ transplant patients were measured and results agreed well with those obtained by using a standard fluorescence polarization immunoassay. Each determination took less than 3 min. The CsA metabolites AM9 and AM19 were also determined by using this technique, and their cross-reactivities with the antibody were 13% and 2%, respectively.

The determination of metabolite M17 and its meaning for immunosuppressive cyclosporin therapy

Cyclosporin A (CyA) is intensively metabolized by the hepatic cytochrome p450 III monooxygenase A system in the human liver, the most important metabolites being M1, M17, and M21. Because CyA and its metabolites have nephrotoxic, hepatotoxic, and neurotoxic side effects, CyA dosage must be calculated to avoid the risk of organ rejection through underdosage and toxic organ damage through overdosage or accumulation of metabolites. In this study, we determined the whole-blood concentrations of cyclosporin and metabolite M17 by high-pressure liquid chromatography (HPLC) and by monoclonal specific and polyclonal nonspecific fluorescence polarization immunoassay (Abbott) in patients after immunosuppressive treatment. Patients with different resorption and metabolization rates showed high individual variations. CyA concentrations in patients with good liver function and low concentrations of CyA metabolites showed a good correlation between the HPLC and the FPIA (TDx-monoclonal assay) methods in ranges between 25 and 180 ng/mL. TDx-monoclonal was not always as precise as HPLC. In cases of metabolic disorders, we found false high CyA concentrations assayed with the immunologic method, caused by a crossreaction of the elevated metabolite concentration. We found that HPLC rendered more information about the extent of immunosuppressive activity and the metabolization rate and showed a good correlation with the concentration of metabolite M17 and total metabolites measured with the Abbott CyA polyclonal kit.