Pharmacokinetics, pharmacodynamics, safety, and tolerability of single-dose fingolimod (FTY720) in adolescents with stable renal transplants.

Oral fingolimod signals the sphingosine 1-phosphate receptor and this in turn mediates immunomodulatory activity. No data of fingolimod in any pediatric population existed before this study. We put our study results in perspective against data from adult renal transplant patients. We investigated pharmacokinetics and pharmacodynamics of single-dose fingolimod (0.07 mg/kg) and its effects on lymphocytes and heart rate in seven adolescents (14.1 ± 1.6 yr) with stable renal transplants. Blood samples for pharmacokinetics and lymphocytes were collected at screening, baseline, and up to 28 days post-dosing. Cardiac monitoring included 12-lead ECG, 24-h Holter monitoring, and echocardiography. A fingolimod dose of 0.07 mg/kg resulted in mean AUC of 731 ± 240 ng·h/mL and C(max) of 3.6 ± 0.6 ng/mL. Drug exposure was nearly identical to adults receiving the same dose. Absolute lymphocyte count decreased 85% from baseline; average nadir occurred by six h post-dose. Heart rate decreased from 74 bpm (predose mean) to 53 bpm (nadir) three h post-dose. Mean heart rates recovered by Day 14 (75 bpm). Weight-adjusted doses of fingolimod in adolescents resulted in drug exposure similar to adults. Adolescents and adults shared comparable negative chronotropic effects and decreased lymphocyte count. Recovery trajectories of these parameters back to baseline were similar between age groups.

Ethnic sensitivity study of fingolimod in white and Asian subjects.

OBJECTIVE: The authors compared the pharmacokinetics and pharmacological effects of the immunomodulator fingolimod in healthy white and Asian subjects for potential ethnic differences. METHODS: White and Asian (Japanese) healthy subjects were demographically matched for sex, age and weight. Subjects received single 1.25 mg doses of fingolimod (6 ethnic pairs), 2.5 mg (7 pairs), 5 mg (6 pairs) or 5 mg/day for 7 days (6 pairs). The pharmacokinetics of fingolimod, major metabolites, peripheral blood lymphocyte counts and heart rate were characterized over 1 month after single-dose and 2 months after multiple-dose administration. RESULTS: There were no clinically relevant differences in the fingolimod dose Cmax or dose AUC relationships between Asian subjects (slopes 0.84 and 1.05) versus white subjects (slopes 1.13 and 1.26) after single-dose administration. During multiple-dose administration, there were no clinically relevant interethnic differences in fingolimod accumulation ratios (6.6 +/- 0.4 for whites, 7.0 +/- 0.7 for Asians), area under the concentration-time curve (390 +/- 73 versus 382 +/- 106 ng x h/ml), or elimination half-life (7.4 +/- 0.8 versus 7.9 +/- 2.0 days). The acute decrease in lymphocyte counts after single- and multiple-dose fingolimod were similar in the two ethnic groups. The lymphocyte recovery rate to baseline after a 5 mg single dose and 5 mg/day multiple dose was reduced by 36 and 15% in Asian subjects compared with white subjects. The transient, acute decrease in heart rate after the first dose of fingolimod and the subsequent return to baseline was similar in the two ethnic groups. CONCLUSION: There were no marked differences between healthy white and Asian subjects in fingolimod single-dose and multiple-dose pharmacokinetics, lymphocyte trafficking and heart rate responses.

Absorption characteristics of EC-MPS--an enteric-coated formulation of mycophenolic sodium.

UNLABELLED: Enteric-coated mycophenolate sodium is an advanced formulation delivering mycophenolic acid (MPA), designed to improve MPA-related upper gastrointestinal adverse events by delaying MPA release until the small intestine. OBJECTIVE: Two studies were undertaken to identify the absolute bioavailability and dose-proportionality of enteric-coated mycophenolate sodium in stable renal transplant patients receiving cyclosporine. METHODS: Study 1: The mean MPA AUC(0-t) was shown to be greater after MPA infusion than after oral enteric-coated mycophenolate sodium (42.1 vs. 28.9 microg x h/ml). Mean absolute bioavailability was 0.71 +/- 0.21 (SD). Study 2: The AUC(0-t) and C(max) for MPA were proportional to the dose of enteric-coated mycophenolate sodium, similarly mean AUC(0-infinity) and C(max) for MPA glucuronide were proportional to dose administered. RESULTS AND CONCLUSIONS: In patients receiving cyclosporine the absolute bioavailability of MPA provided by enteric-coated mycophenolate sodium is equivalent to that provided by mycophenolate mofetil when administered in combination with cyclosporine, and exhibits dose-proportionality. Enteric-coated mycophenolate sodium was well tolerated from 180 - 2,160 mg with no serious adverse events reported.

Lumiracoxib does not affect the ex vivo antiplatelet aggregation activity of low-dose aspirin in healthy subjects.

This randomized, double-blind, placebo-controlled study evaluated the pharmacodynamic effects of concomitant low-dose aspirin and lumiracoxib in healthy subjects. Participants received lumiracoxib 400 mg once daily (n = 14) or placebo (n = 14) for 11 days, with concomitant low-dose aspirin (75 mg once daily) from days 5 to 11. Ex vivo pharmacodynamic assessments included assays of platelet aggregation and urinary thromboxane and prostacyclin metabolite profile. Arachidonic acid-stimulated platelet aggregation was reduced from 76.3% on day 4 to 4.8% on day 11 in the placebo group and from 75.8% on day 4 to 5.1% on day 11 in the lumiracoxib group. Collagen-induced platelet aggregation was reduced from 77.5% on day 4 to 52.8% on day 11 in the placebo group and from 79.5% on day 4 to 55.9% on day 11 in the lumiracoxib group. Urinary thromboxane and prostacyclin were unaffected by lumiracoxib. In conclusion, concomitant lumiracoxib did not interfere with the cyclooxygenase-1-mediated antiplatelet effects of low-dose aspirin.

Pharmacokinetic interaction between verapamil and everolimus in healthy subjects.

AIMS: We sought to define the influence of verapamil, an inhibitor of CYP3A and P-glycoprotein, on the pharmacokinetics of everolimus, a substrate of this enzyme and transporter. METHODS: This was a two-period, single-sequence, crossover study in 16 healthy subjects. In period 1 subjects received a single 2 mg oral dose of everolimus. In period 2 they received verapamil 80 mg three times daily for a total of 6 days and a single 2 mg dose of everolimus co-administered on the second day of verapamil therapy. RESULTS: During verapamil co-administration, everolimus C(max) increased 2.3-fold (90% CI, 1.9, 2.7) from 21 +/- 8 to 47 +/- 18 ng ml(-1) and AUC increased 3.5-fold (90% CI, 3.1, 3.9) from 115 +/- 45 to 392 +/- 142 ng ml(-1) h. Everolimus half-life was only prolonged to a minor extent (32 +/- 6 vs. 37 +/- 6 h). Verapamil predose concentrations doubled from 32 +/- 16 to 74 +/- 42 ng ml(-1) after single dose administration of everolimus. CONCLUSIONS: Multiple dosing with verapamil increased blood concentrations of everolimus after a single dose by an average 3.5-fold. During verapamil treatment, dose reduction for everolimus should be made guided by blood monitoring and for verapamil by blood pressure monitoring.

Pharmacokinetic/pharmacodynamic relationships of FTY720 in kidney transplant recipients.

FTY720 is a new and effective immunosuppressive agent, which produces peripheral blood lymphopenia through a lymphocyte homing effect. We investigated the relationship between the dose of FTY720 or blood concentration (pharmacokinetics, PK) and peripheral lymphopenia (pharmacodynamics, PD) in 23 kidney transplant recipients randomized to receive FTY720 (0.25-2.5 mg/day) or mofetil mycophenolate (2 mg/day) in combination with cyclosporine and steroids. FTY720 dose, blood concentrations and lymphocyte counts were determined weekly before and 4 to 12 weeks after transplantation. The effect of PD was calculated as the absolute lymphocyte count or its reductions. PK/PD modeling was used to find the best-fit model. Mean FTY720 concentrations were 0.36 +/- 0.05 (0.25 mg), 0.73 +/- 0.12 (0.5 mg), 3.26 +/- 0.51 (1 mg), and 7.15 +/- 1.41 ng/ml (2.5 mg) between 4 and 12 weeks after transplantation. FTY720 PK was linear with dose (r(2) = 0.98) and showed low inter- and intra-individual variability. FTY720 produced a dose-dependent increase in mean percent reduction of peripheral lymphocyte counts (38 vs 42 vs 56 vs 77, P < 0.01, respectively). The simple Emax model [E = (Emax * C)/(C + EC50)] was the best-fit PK/PD modeling for FTY720 dose (Emax = 87.8 +/- 5.3% and ED50 = 0.48 +/- 0.08 mg, r(2) = 0.94) or concentration (Emax = 78.3 +/- 2.9% and EC50 = 0.59 +/- 0.09 ng/ml, r(2) = 0.89) vs effect (% reduction in peripheral lymphocytes). FTY720 PK/PD is dose dependent and follows an Emax model (EC50 = 0.5 mg or 0.6 ng/ml). Using lymphopenia as an FTY720 PD surrogate marker, high % reductions (~80%) in peripheral lymphocytes are required to achieve best efficacy to prevent acute allograft rejection.

Pharmacokinetic/pharmacodynamic relationships of FTY720 in kidney transplant recipients

FTY720 is a new and effective immunosuppressive agent, which produces peripheral blood lymphopenia through a lymphocyte homing effect. We investigated the relationship between the dose of FTY720 or blood concentration (pharmacokinetics, PK) and peripheral lymphopenia (pharmacodynamics, PD) in 23 kidney transplant recipients randomized to receive FTY720 (0.25-2.5 mg/day) or mofetil mycophenolate (2 mg/day) in combination with cyclosporine and steroids. FTY720 dose, blood concentrations and lymphocyte counts were determined weekly before and 4 to 12 weeks after transplantation. The effect of PD was calculated as the absolute lymphocyte count or its reductions. PK/PD modeling was used to find the best-fit model. Mean FTY720 concentrations were 0.36 ± 0.05 (0.25 mg), 0.73 ± 0.12 (0.5 mg), 3.26 ± 0.51 (1 mg), and 7.15 ± 1.41 ng/ml (2.5 mg) between 4 and 12 weeks after transplantation. FTY720 PK was linear with dose (r² = 0.98) and showed low inter- and intra-individual variability. FTY720 produced a dose-dependent increase in mean percent reduction of peripheral lymphocyte counts (38 vs 42 vs 56 vs 77, P < 0.01, respectively). The simple Emax model [E = (Emax * C)/(C + EC50)] was the best-fit PK/PD modeling for FTY720 dose (Emax = 87.8 ± 5.3 percent and ED50 = 0.48 ± 0.08 mg, r² = 0.94) or concentration (Emax = 78.3 ± 2.9 percent and EC50 = 0.59 ± 0.09 ng/ml, r² = 0.89) vs effect ( percent reduction in peripheral lymphocytes). FTY720 PK/PD is dose dependent and follows an Emax model (EC50 = 0.5 mg or 0.6 ng/ml). Using lymphopenia as an FTY720 PD surrogate marker, high percent reductions ( about 80 percent) in peripheral lymphocytes are required to achieve best efficacy to prevent acute allograft rejection.

Mycophenolic acid metabolite profile in renal transplant patients receiving enteric-coated mycophenolate sodium or mycophenolate mofetil.

Mycophenolate mofetil (MMF), a prodrug of mycophenolic acid (MPA), is an effective immunosuppressive treatment in renal transplant recipients but is known to have gastrointestinal side effects. Enteric-coated mycophenolate sodium (EC-MPS; myfortic) is a new formulation for delivering MPA. This open-label, two-period, cross-over study was carried out to characterize the time course of MPA and its metabolites, mycophenolic acid glucuronide (MPAG) and acyl mycophenolic acid glucuronide (AcMPAG) in stable renal transplant patients (n = 40) after 28-day chronic dosing with EC-MPS (720 mg bid) or MMF (1000 mg bid). The relative abundance and exposure of all three compounds was also assessed. EC-MPS demonstrated the typical pharmacokinetic profile of an enteric-coated formulation with a delayed release of MPA compared with MMF (Tmax 2.5 versus 1.0 hours, respectively). Consistent with a similar disposition of MPA, both EC-MPS and MMF treatments resulted in the same ratio of MPAG to MPA exposure, 23:1. Furthermore, comparison of the AUC of MPAG and AcMPAG for both treatments indicated that steady state MPAG exposure was 75 to 90 times that of AcMPAG, confirming MPAG as the predominant metabolite of MPA. AcMPAG has been identified as a possible active metabolite of MPA; the present study indicates that AcMPAG may contribute around 14% of the exposure to active drug after administration of MPA. Both EC-MPS and MMF treatments were well tolerated over the 1-month period of chronic treatment. In summary, consistent with its enteric-coated design, EC-MPS delays delivery of MPA, but results in similar exposure to that provided by MMF.

Blood concentrations of everolimus are markedly increased by ketoconazole.

The authors sought to quantify the influence of the CYP3A and P-glycoprotein inhibitor ketoconazole on the pharmacokinetics of everolimus in healthy subjects. This was a 2-period, single-sequence, crossover study in 12 healthy subjects. In period 1, subjects received the reference treatment of a single 2-mg dose of everolimus. In period 2, they received the test treatment of ketoconazole 200 mg twice daily for a total of 8 days and a single dose of everolimus coadministered on the fourth day of ketoconazole therapy. The test/reference ratio and 90% confidence interval were derived for everolimus maximum concentration and area under the curve. During ketoconazole coadministration, everolimus maximum concentration increased 3.9-fold (90% confidence interval, 3.4-4.6) from 15 +/- 4 ng/mL to 59 +/- 13 ng/mL. Everolimus area under the curve increased 15.0-fold (90% confidence interval, 13.6-16.6) from 90 +/- 23 ng*h/mL to 1324 +/- 232 ng*h/mL. Everolimus half-life was prolonged by 1.9-fold from 30 +/- 4 hours to 56 +/- 5 hours. Everolimus did not appear to alter ketoconazole predose concentrations. Given the magnitude of this drug interaction, use of ketoconazole should be avoided if possible in everolimus-treated patients.

FTY720 pharmacokinetics in mild to moderate hepatic impairment.

The influence of mild and moderate hepatic impairment on FTY720 pharmacokinetics was assessed. The authors enrolled 32 subjects consisting of 8 with mild and 8 with moderate hepatic impairment based on Child-Pugh criteria and 16 demographically matched control subjects. A single 1-mg oral dose of FTY720 was administered under fasting conditions. Blood, plasma, and urine samples were obtained over a 14-day period for measurement of FTY720 and metabolite concentrations and protein binding. Total blood lymphocyte counts and heart rate were serially monitored to assess pharmacologic responses to FTY720. Peak FTY720 blood concentrations were similar across groups. Oral clearance (CL/F) was reduced 10% in mild hepatic impairment (P = .493) and 31% in moderate hepatic impairment (P = .034). There were no significant differences in blood exposure to the hexanoic or butanoic acid metabolites among groups. The effect of FTY720 on blood lymphocytes was similar across groups, with a mean decrease of 44% from the predose value. Like-wise, the effect of FTY720 on supine heart rate was similar across groups, with a mean 13% decrease from the predose rate occurring 2 to 4 hours postdose and recovering within 1 to 2 days. Although hepatic impairment elicited changes in the disposition of FTY720, the magnitude of these changes suggests that the FTY720 dose does not need to be adjusted in mild or moderate hepatic-impaired patients.

Effect of multiple-dose erythromycin on everolimus pharmacokinetics.

OBJECTIVE: We sought to quantify the influence of the CYP3A inhibitor erythromycin on the pharmacokinetics of everolimus, a CYP3A substrate. METHODS: This was a two-period, single-sequence, crossover study in 16 healthy subjects. In period 1, subjects received the reference treatment of a single 2-mg dose of everolimus. In period 2, they received the test treatment of erythromycin 500 mg three times daily for a total of 9 days and a single 2-mg dose of everolimus coadministered on the fifth day of erythromycin therapy. The test/reference ratio and 90% confidence interval (CI) were derived for everolimus C (max) and AUC. RESULTS: During erythromycin coadministration, everolimus C (max) increased 2.0-fold (90% CI, 1.8-2.3) from 20+/-5 ng/ml to 40+/-10 ng/ml. Everolimus AUC increased 4.4-fold (90% CI, 3.5-5.4) from 116+/-37 ng h/ml to 524+/-225 ng h/ml. Everolimus half-life was prolonged by 39% from 32+/-6 h to 44+/-6 h. Erythromycin predose concentrations were not changed after single-dose administration of everolimus. CONCLUSION: Multiple-dose erythromycin increased single-dose everolimus blood levels by an average 4.4-fold (range, 2.0-12.6). During erythromycin treatment, a compensatory everolimus dose reduction should be made guided by everolimus therapeutic drug monitoring.

FTY 720A mediates reduction of lymphocyte counts in human renal allograft recipients by an apoptosis-independent mechanism.

The novel immunosuppressive compound FTY 720A posseses a mode of action which is different from all other immunosuppressive drugs. The most prominent feature is a reversible decrease in peripheral lymphocyte counts observed in animal experiments. We investigated in the first human trial (phase 1) whether FTY 720A induces apoptosis of peripheral blood mononuclear cells (PBMC) in stable renal allograft recipients. Monitoring of lymphocyte counts revealed a significant and dose-dependent decrease within 6 h post-FTY 720A dose: placebo 5.1%; 0.25 mg 36.4%; 0.5 mg 40.8%; 0.75 mg 39.4%; 1 mg 45.8%; 2 mg 67.2%; 3.5 mg 64.9%. PBMC apoptosis rates did not change, as determined before intake of FTY 720A and 2 h, 6 h, 24 h and 96 h post-FTY 720A dose. We detected no significant difference in apoptosis rates between patients who received placebo or FTY 720A. However, in vitro experiments showed that high concentrations of FTY 720 A induced apoptosis in human PBMC.

Renal transplantation in end-stage sickle cell nephropathy.

BACKGROUND: The role of renal transplantation as treatment for end-stage sickle cell nephropathy (SCN) has not been well established. METHODS: We performed a comparative investigation of patient and allograft outcomes among age-matched African-American kidney transplant recipients with ESRD as a result of SCN (n=82) and all other causes (Other-ESRD, n=22,565). RESULTS: The incidence of delayed graft function and predischarge acute rejection in SCN group (24% and 26%) was similar to that observed in the Other-ESRD group (29% and 27%). The mean discharge serum creatinine (SCr) was 2.7 (+/-2.5) mg/dl in the SCN recipients compared to 3.0 (+/-2.5) mg/dl in the Other-ESRD recipients (P=0.42). There was no difference in the 1-year cadaveric graft survival (SCN: 78% vs. Other-ESRD: 77%), and the multivariable adjusted 1-year risk of graft loss indicated no significant effect of SCN (relative risk [RR]=1.39, P=0.149). However, the 3-year cadaveric graft survival tended to be lower in the SCN group (48% vs. 60%, P=0.055) and their adjusted 3-year risk of graft loss was significantly greater (RR= 1.60, P=0.003). There was a trend toward improved survival in the SCN transplant recipients compared to their dialysis-treated, wait-listed counterparts (RR=0.14, P=0.056). In comparison to the Other-ESRD (RR=1.00), the adjusted mortality risk in the SCN group was higher both at 1 year (RR=2.95, P=0.001) and at 3 years (RR=2.82, P=0.0001) after renal transplantation. CONCLUSIONS: The short-term renal allograft result in recipients with end-stage SCN was similar to that obtained in other causes of ESRD, but the long-term outcome was comparatively diminished. There was a trend toward better patient survival with renal transplantation relative to dialysis in end-stage SCN.

Prognosis after primary renal transplant failure and the beneficial effects of repeat transplantation: multivariate analyses from the United States Renal Data System.

BACKGROUND: Survival of transplant recipients after primary renal allograft failure has not been well studied. METHODS: A cohort of 19,208 renal transplant recipients with primary allograft failure between 1985 and 1995 were followed from the date of allograft loss until death, repeat transplantation, or December 31, 1996. The mortality, wait-listing, and repeat transplantation rates were assessed. The mortality risks associated with repeat transplantation were estimated with a time-dependent survival model. RESULTS: In total, 34.5% (n=6,631) of patients died during follow-up. Of these deaths, 82.9% (n=5,498) occurred in patients not wait-listed for repeat transplantation, 11.9% (n=789) occurred in wait-listed patients, and 5.2% (n=344) occurred in second transplant recipients. Before repeat transplantation, the adjusted 5-year patient survival was 36%, 49%, and 65% for type I diabetes mellitus (DM), type II DM, and nondiabetic end-stage renal disease, respectively (P<0.001; DM vs. nondiabetics). The adjusted 5-year patient survival was lower in Caucasians (57%, P<0.001) compared with African-Americans (67%) and other races (64%). The 5-yr repeat transplantation rate was 29%, 15%, and 19%, whereas the median waiting time for a second transplant was 32, 90, and 81 months for Caucasians, African-Americans, and other races, respectively (P<0.0001 each). Repeat transplantation was associated with 45% and 23% reduction in 5-year mortality for type I DM and nondiabetic end-stage renal disease, respectively, when compared with their wait-listed dialysis counterparts with prior transplant failure. CONCLUSIONS: The loss of a primary renal allograft was associated with significant mortality, especially in recipients with type I DM. Repeat transplantation was associated with a substantial improvement in 5-year patient survival. Recipients with type I DM achieved the greatest proportional benefit from repeat transplantation.

Delayed graft function: risk factors and implications for renal allograft survival.

Delayed graft function (DGF) may be associated with diminished kidney allograft survival. We studied the risk factors that lead to nonimmediate function of a renal allograft and the consequences of DGF on short- and long-term renal transplant survival. Data from the U.S. Renal Data System were used to measure the relationships among cold ischemia time, delayed graft function, acute rejection, and graft survival in 37,216 primary cadaveric renal transplants (1985-1992). These relationships were investigated using the unconditional logistic and Cox multivariate regression methods. Cold ischemia time was strongly associated with DGF, with a 23% increase in the risk of DGF for every 6 hr of cold ischemia (P<0.001). Acute transplant rejection occurred more frequently in grafts with delayed function (37% vs. 20%; odds ratio=2.25, P=0.001). DGF was independently predictive of 5-year graft loss (relative risk=1.53, P<0.001). The presence of both early acute rejection and DGF portended a dismal 5-year graft survival rate of 35%. Zero-HLA mismatch conferred a 10-15% improvement in 1- and 5-year graft survival regardless of early functional status of the allograft. However, the 5-year graft survival rate in HLA-mismatched kidneys without DGF was significantly higher than that of zero-mismatched kidneys with DGF (63% vs. 51%; P<0.001). DGF independently portends a significant reduction in short- and long-term graft survival. Delayed function and early rejection episodes exerted an additive adverse effect on allograft survival. The deleterious impact of delayed function is comparatively more severe than that of poor HLA matching.

The cytokine response in renal allograft rejection.

Cytokines play an essential role in regulating and co-ordinating acute renal allograft rejection. Organ rejection represents a broad inflammatory response which likely utilizes every facet of both innate and acquired immunity. Under appropriate proinflammatory cytokine stimulation, donor renal tubule cells may function as active participants in the host inflammatory response by producing chemokines and other proinflammatory mediators. Although there is high enthusiasm in using cytokine-based therapies in the future, the overlapping and redundant features of cytokine signalling will require careful choice of individual or combination therapy.

Epithelial-derived neutrophil-activating factor-78 production in human renal tubule epithelial cells and in renal allograft rejection.

Chemotactic cytokines, or chemokines, are likely mediators of inflammatory cell recruitment in renal allograft rejection. A recent addition to the C-X-C super gene family branch of chemokines is epithelial-derived neutrophil-activating factor-78 (ENA-78). ENA-78 is a 78-amino acid peptide with neutrophil-activating and chemotactic properties. This chemokine is unique in that it was originally isolated and cloned from an IL-1-stimulated human pulmonary epithelial cell line, A549. In this article, we investigated whether ENA-78 could be produced by human renal epithelial cells. We found that primary cultures of human renal cortical epithelial cells with tubular cell attributes could express significantly increased steady state levels of ENA-78 mRNA when stimulated with IL-1 beta (2.0 ng/ml). In addition, these cells also secreted significantly increased ENA-78 antigen compared with controls when stimulated with IL-1 beta (2.0 ng/ml). Other proinflammatory agonists, including TNF alpha, IFN gamma, and LPS failed to stimulate ENA-78 steady state mRNA or antigenic peptide production by renal cortical epithelial cells. In addition, biopsy tissue from acutely rejecting human renal allografts had higher copy number of ENA-78 mRNA compared with nonrejecting renal allograft controls using a quantitative reverse transcriptase polymerase chain reaction method with a mutant ENA-78 transcript. In the proinflammatory milieu of the rejecting renal allograft, IL-1 beta produced by host and donor mononuclear cells may drive ENA-78 production by allograft tubule cells, thus effecting leukocyte recruitment into the tubulointerstitial compartment.

Prediction of interpatient and intrapatient variation in OG 37-325 dosing requirements by the erythromycin breath test. A prospective study in renal transplant recipients.

OG 37-325 (nva-cyclosporine, cyclosporine G) is structurally similar to cyclosporine A (CsA). We hypothesized that OG 37-325 may, therefore, be metabolized by P450 3A, an enzyme recently shown to metabolize CsA. To test this hypothesis, we employed the erythromycin breath test (ERMBT) to measure P450 3A activity on multiple occasions in twenty OG 37-325-treated renal transplant recipients. When stable dosing was achieved, there was a measured 6-fold variation in the ratio of 12-hr whole-blood parent compound trough concentration (ng/ml, HPLC) to daily OG 37-325 dose (mg/kg) ([OG 37-325]/dose). In support of our hypothesis, there was an inverse correlation between the ERMBT result and the [OG 37-325]/dose ratio (r = -0.71, P < 0.001, n = 20); that is, patients with higher P450 3A activity generally required higher OG 37-325 doses to attain target blood levels. We also found that intrapatient variation in the [OG 37-325]/dose ratio observed over the course of the study correlated with changes in the ERMBT results (r = -0.67, P = 0.002). Inter- and intrapatient differences in [OG 37-325]/dose ratio were not predicted by patient age, serum cholesterol, blood hematocrit, or traditional liver chemistries. We conclude that P450 3A is generally rate limiting in the elimination of OG 37-325 in adult renal transplant recipients. Therefore, most drug interactions observed with CsA should also be expected with OG 37-325. We also conclude that intrapatient changes in OG 37-325 dosing requirements largely result from changes in P450 3A activity. The ERMBT may therefore provide useful information concerning patient compliance and may also serve as a useful guide to OG 37-325 dosing adjustments.

Interferon-gamma regulation of human renal cortical epithelial cell-derived monocyte chemotactic peptide-1.

The chemoattractant signal(s) that results in the transmigration of monocytes/macrophage into the tubulointerstitium during acute inflammation is not known. Monocyte chemotactic peptide-1 (MCP-1), a recently described chemotactic cytokine, may function as both a potent monocyte chemotaxin and activator in renal inflammation. We have studied the proinflammatory conditions in which cultured human renal cortical epithelial cells (RCEC) of tubular origin may be stimulated to produce MCP-1. RCEC were stimulated in a dose-time dependent manner with: IL-1 beta (0.01 to 1.0 ng/ml), TNF (0.1 to 10 ng/ml), LPS (0.1 to 10 micrograms/ml) or INF-gamma (10-1000 U/ml). Conditioned media from RCEC stimulated with either IL-1 beta or INF-gamma produced a monocyte chemoattractant activity which was significantly suppressed with neutralizing antibody to MCP-1. Stimulation of RCEC with either IL-1 beta or INF-gamma resulted in a significant (4- to 5-fold) increase in steady state levels of MCP-1 mRNA. MCP-1 antigenic peptide in RCEC conditioned media was significantly increased over control (2- to 2.5-fold) after stimulation with either IL-1 beta or IFN-gamma. In contrast, production of interleukin-8 (IL-8), a neutrophil chemotactic cytokine, was not stimulated by IFN-gamma in RCEC. Thus, the chemokine signaling repertoire of renal tubule cells may be selectively controlled by IFN-gamma.