C. T. Van Buren

Therapeutic drug monitoring of sirolimus: correlations with efficacy and toxicity

We sought to examine the potential benefits of therapeutic drug monitoring of sirolimus, a potent immunosuppressive agent that displays a pleiotropic array of side effects. 
Methods. A high‐performance liquid chromatography (LC) procedure combined with ultraviolet detection (UV) was used to measure serial concentrations of parent compound sirolimus in 150 renal transplant recipients over a period of 4 yr. Drug concentrations in whole blood at trough time, as well as within pharmacokinetic profiles, were correlated with clinical events using contingency tables, logistic regression analysis, and receiver operating characteristic (ROC) curves. 
Results. The LC/UV method showed an excellent correlation with detection of LC‐resolved components by tandem mass spectrometry, demonstrating that the LC/UV method selectively detected parent compound. Sirolimus displayed the characteristics of a critical‐dose drug: Its concentration could not be predicted by a standard body or demographic measure, or by dose, and it showed high degrees of intra‐ and inter‐individual variability. However, there was a good correlation between trough and area‐under‐the‐curve measurements. There was a significant association between trough values expressed as either observed (<5 ng/mL) or dose‐corrected parameter (<1.7 ng/mL per mg administered drug) and the occurrence and severity of acute rejection episodes – despite the low overall incidence of 23 episodes among the cohort of 150 patients. Similarly, ROC functions showed a correlation of the occurrence of hypertriglyceridemia, thrombocytopenia, and leukopenia, but not hypercholesterolemia, with trough concentrations above 15 ng/mL. 
Conclusion. Due to its behavior as a critical‐dose drug, therapeutic monitoring to measure sirolimus concentrations by a LC/UV method may provide clinicians with a tool to optimize outcomes.

Hepatobiliary and pancreatic complications of cyclosporine therapy in 466 renal transplant recipients

Two hundred twenty-eight patients from a total of 466 (49%) receiving renal allografts under cyclospo-rine/prednisone (CsA/Pred) immunosuppression experienced at least one episode of posttransplant hepato-toxicity. All patients were documented to have normal serum bilirubin, serum glutamic oxaloacetic transaminase (SGOT), serum glutamic pyruvate transaminase (SGPT), lactic acid dehydrogenase (LDH), and alkaline phosphatase (AP), as well as negative results of biliary ultrasound and upper gastrointestinal contrast examinations prior to transplantation. Hepatotoxic episodes usually were self-limited (82%), and generally occurred during the very early posttransplant period (76%). Liver function abnormalities included hyperbilirubinemia (48% of patients), elevated SGOT (47%), SGPT (73%), LDH (84%), and AP (59%). The CsA serum trough radioimmunoassay (RIA) was relatively high among hepatotoxic patients with a mean value of 225± 17 ng/ml. Pharmacokinetic parameters, including bioavailability and drug clearance, were significantly altered among this group of patients. The management strategy of CsA dose reduction was effective; however, 11 patients (2.4%) developed biliary calculous disease posttransplant while under CsA/Pred immunosuppression. Seven patients had cholelithiasis, and two patients underwent choledochoduodenostomy because of primary choledocholithiasis. The results contrast with 279 renal transplant recipients from an overlapping nonrandomized group treated with azathioprine (Aza)/Pred in whom cholelithiasis was not identified. Pancreatic abnormalities were relatively common, but clinical pancreatic disease occurred in only six patients. There were two episodes of acute pancreatitis, three patients developed pancreatic abscess, and one patient developed a pancreatic pseudocyst. The apparent proclivity of CsA-treated patients to develop biliary calculous disease, and the occurrence of serious pancreatic complications in a small percentage of patients did not affect the majority of CsA-treated patients. They may, however, represent important problems associated with the use of this immunosuppressive agent.

Complications of cyclosporine-prednisone immunosuppression in 402 renal allograft recipients exclusively followed at a single center for from one to five years.

The therapeutic efficacy of cyclosporine (CsA) as an immunosuppressive agent was complemented by a modest, long-term incidence of toxic complications in 402 renal allograft recipients engrafted one to five years prior to analysis. The overall patient and graft survivals at one year were 97% and 84% (actual), and at five years 92% and 67% (actuarial). The immunosuppressive therapeutic index was excellent: only 12% of allografts were lost from rejection, with 5% of patients succumbing to infection. While infections were common, tending to emanate in the urinary tract or to be viral in etiology, they were generally mild and readily controlled. Only four patients displayed malignancies; none succumbed to this cause. The most common toxic complication was hypertrichosis, which was accentuated in pediatric patients. While tremors occurred in 20% of patients, primarily during the first three months, other neuroectodermal complications of parethesias, depression, somnolence, and seizures were rare. Hepatotoxicity, which was noted in 50% of patients, particularly recipients of cadaveric grafts, generally was first seen as a transaminase elevation, at least partially reversible by dose-reduction and abating by the third year. Associated disturbances of cholelithiasis and pancreatitis were occasionally observed. Nephrotoxicity was the only persistent, long-term complication. Hypertension occurred in 72% of patients during the first month, 36% in the second year, and about 15% thereafter. Hyperuricemia, which occurred in about 30% of recipients during the first two years, was occasionally associated with symptomatic gout. The mean serum creatinine level remained elevated throughout the follow-up period at 1.8—1.9 mg/dl, suggesting persistent, but nonprogressive, drug-induced renal injury. The present analysis documents the relative safety of CsA for long-term therapy, and highlights the need for new approaches to ameliorate drug-induced nephrotoxicity.

Causes of graft loss beyond two years in the cyclosporine era

While CsA has improved renal-allograft survival rates in the first 2 years compared with Aza, Terasakis multicenter study (1) failed to show any difference in long-term graft survival in CsA-Pred versus Aza-Pred-treated recipients. The present study examines the long-term graft-survival rates at a single center using CsA immunosuppression and seeks to discern the causes of 58 graft losses among 343 patients with functioning grafts beyond 2 years posttransplantation. The 6-year primary and cadaveric actuarial graft survival at this institution is 59% with a graft half-life of 10 years, which is better than the 40% and 7.7 years, respectively, reported by Terasaki (1) for primary cadaveric recipients on Aza-Pred. It is also better than the 41%, 6-year survival and 5.5-year half-life for primary cadaveric recipients treated with CsA-Pred as reported in the multicenter study. (1) Less experience with the use of CsA may explain the latter comparison. Primary LRD grafts at this institution (2/3 haploidentical) have a 6-year actuarial survival of 77% and a half-life very closely approximating that of HLA-identical LRD grafts under Aza (23.4 years). These results demonstrate that CsA mitigates the effects of HLA incompatibility to reduce graft survival. The most common cause of graft loss beyond 2 years was chronic rejection (36.2%) followed by noncompliance (27.6%). Patient deaths resulted in 13 of the 58 graft losses; most of the deaths were related to cardiovascular diseases. Only 3 patients died from causes that could be attributed to CsA immunosuppression; 2 from sepsis and 1 from viral hepatitis. Acute rejection caused 8.6% of the graft losses on continuous CsA therapy. When immunologic risk factors were analyzed, the entire graft-loss group had a significantly higher proportion of retransplant patients than the graft-survival group (P less than 0.005), suggesting that prior transplantation imposes a higher risk for graft loss not only acutely but long term as well. However, retransplanted patients were significantly less likely to lose their grafts because of noncompliance (P less than 0.005). Male patients were found to be significantly more noncompliant.

POSSIBLE CONTRIBUTION OF PRETRANSPLANT IMMUNE RESPONDER STATUS TO RENAL ALLOGRAFT SURVIVAL DIFFERENCES OF BLACK VERSUS WHITE RECIPIENTS

Black end-stage renal disease patients may present as an immunologically higher-risk group for renal allograft transplantation than white ESRD patients. To test this hypothesis, we correlated graft survivals in 124 black and 241 white cyclosporine-prednisone-treated primary cadaveric renal allograft recipients with pre-Tx nonspecific immune responder status (strong vs. weak immune responders), donor-recipient-specific MLC responsiveness, HLA match, and blood transfusion (BT) history. One-, 2- and 3-year patient survival rates of 95%, 94%, and 94% were identical for both groups. However, the 1-, 2-, 3-year graft survival rates for white recipients of 82%, 79%, and 75% were significantly higher than the 70%, 62%, and 55% rates for black recipients (P less than 0.01 for each, respectively). Pre-Tx nonspecific immune response values for blacks were significantly (P less than 0.01) higher than for whites (38% vs. 28% for active T cell; 1.8 vs. 1.3 for TH:TS ratio; 28,581 c.p.m. vs. 14,870 c.p.m. for spontaneous blastogenesis; and a stimulation index (SI) of 34 vs. 20 for panel mixed lymphocyte culture). Additionally, the specific recipient-donor MLC (SI) for black recipients was significantly greater than the specific recipient-donor MLC for white recipients (MLC SI of 40 vs. 18, P less than 0.01). Blacks present as pre-Tx strong immune responders with a greater frequency than whites (90% vs. 66%, P less than 0.01). Moreover, black strong responders experience a poorer 1-year graft survival than white strong responders (67% vs. 80%, P less than 0.01). Even though the pre-Tx BT histories of white and black ESRD patients studied herein were comparable, the immunoregulatory effect of pre-Tx BT was different in white vs. black patients. A significant reduction in TH:TS ratio was observed when comparing 0 vs. 1-4 pre-Tx white patient BT groups, whereas significant changes in TH:TS ratios were not observed until after comparing 0 vs. greater than or equal to 5 pre-Tx black patient BT groups. HLA matching and pre-Tx BT had no impact on improving the graft survivals of these CsA-Pred-treated white or black recipients. These data, therefore, support the hypothesis that black recipients present as an immunologically higher-risk group than white recipients.

A phase I study of a 4-week course of SDZ-RAD (RAD) in quiescent cyclosporine-prednisone-treated renal transplant recipients

BACKGROUND AND METHODS This phase I, randomized, blinded, placebo-controlled study assessed the safety profile and pharmacokinetics of a 4-week course of once-daily, sequential ascending doses (0.75, 2.5, or 7.5 mg/day) of SDZ-RAD (RAD) capsules in renal transplant recipients on a stable regimen of cyclosporine (CsA; Neoral) and prednisone. RESULTS RAD displayed a similar spectrum of side effects as observed with rapamycin, namely, an increased incidence of infection associated with the augmented immunosuppression and a dose-related occurrence of thrombocytopenia, hypercholesterolemia, and hypertriglyceridemia, particularly at the 7.5-mg dose. The pharmacokinetic parameters of RAD showed dose proportionality, a good correlation between trough and area under the curve (AUC) concentrations, and a moderate accumulation of 2.5-fold. The drug was absorbed within 2 hr and displayed a 16-19-hr half-life, which is shorter than that of rapamycin. RAD reached steady state at 4 days. Preliminary kinetic-dynamic correlations indicate a correlation between thrombocytopenia (but not hyperlipidemia) and AUC, as well as maximum drug concentrations, and weight-adjusted dose. At the end of a 4-week course of simultaneous dosing, there was no evidence of a pharmacokinetic interaction between CsA and RAD. CONCLUSION This study suggests that the shorter half-life of RAD compared to rapamycin may confer the benefits of rapid attainment of steady state and dissipation of effects upon drug cessation. Controlled, multicenter trials are being planned to assess the impact of these features on clinical outcomes.

Ten years of sirolimus therapy for human renal transplantation: the University of Texas at Houston experience.

ON APRIL 13, 1993, a phase I trial was initiated to assess the safety and pharmacokinetic behavior of ascending doses of a new immunosuppressant discovered by Sehgal and applied in animal transplant models by Calne et al and Morris et al. Forty stable renal transplant patients who received either the oral liquid formulation of sirolimus (SRL) or placebo, displayed only modest adverse reactions. Drug development proceeded rapidly through a subsequent phase I/II study of de novo drug administration which confirmed the safety and documented the efficacy of a sirolimus-cyclosporine (CsA) combination to reduce the incidence of acute rejection episodes. The first multicenter phase II trial showed that reduced doses of CsA were efficacious in non–African Americans when administered in combination with sirolimus. The pivotal phase III trials performed in the United States (US) and across the world (Global) demonstrated the benefit of a sirolimus-CsAPrednisone (Pred) regimen for acute rejection prophylaxis, leading to approval by the US Food and Drug Administration (FDA). This contribution reviews not only the milestones up to FDA approval, but also our present strategies, as utilized in 1008 renal transplant recipients, to deliver the maximal benefit of sirolimus with minimal CsA exposure, thereby reducing the hazards of chronic immunosuppression.

Flow cytometry-detected IgG is not a contraindication to renal transplantation : IgM may be beneficial to outcome

BACKGROUND At our transplant center, primary recipients of either a haplo-identical (haplo-ID) living related (LRD) or a cadaveric (CAD) donor renal allograft are transplanted after a negative donor-specific IgG anti-human globulin (AHG) cross-match (XM). Testing included the historically highest panel-reactive antibody and the immediate (0-7 days) pretransplant sera. A positive donor specific IgM-AHG XM has not been a contraindication to transplant. Reports suggest that donor-specific flow cytometry cross-matches (FCXM) may be more clinically informative than the AHG-XM. METHODS We therefore evaluated the impact of a positive FCXM (IgG or IgM) on the rejection frequency (0-12 months after transplant) and 1-year graft survival for cyclosporine-prednisone-treated primary (haplo-ID and CAD) renal allograft recipients. All transplants were performed after a negative donor-specific IgG AHG-XM regardless of the IgM-AHG XM status. RESULTS Rejection frequencies (26% vs. 31%, P = NS) and 1-year graft survivals (92% vs. 89%, P = NS) were comparable for haplo-ID LRD FCXM-negative and IgG-FCXM-positive recipients. However, IgM-FCXM-positive LRD recipients experienced significantly fewer rejections (13% vs. 26% P<0.02) and an improved 1-year graft survival (100% vs. 92%, P<0.02) than FCXM-negative LRD recipients. Similar results were observed for primary CAD recipients. Rejection frequencies (40% vs. 44%, P = NS) and 1-year graft survivals (83% vs. 81%, P = NS) were comparable for primary CAD FCXM-negative and IgG-FCXM-positive recipients. Again, IgM-FCXM-positive primary CAD recipients experienced significantly fewer rejections (22% vs. 40%, P<0.02) and improved 1-year graft survivals (89% vs. 83%, P<0.05) than FCXM-negative recipients. CONCLUSION These data suggest that, after a negative donor-specific IgG-AHG XM, an IgG-positive FCXM is not a contraindication to transplantation. The presence of IgM may be beneficial in reducing the occurrence of rejection episodes and improving graft survivals.

Proteinuria in cyclosporine-treated renal transplant recipients

Of 704 renal transplant recipients receiving long-term cyclosporine immunosuppression, 71 patients experienced proteinuria greater than 1 g/24 hr beyond the first month posttransplant. Eight patients displayed transient proteinuria, defined as lasting less than 3 months. In most cases this condition was attributed to biopsy-proved acute rejection. The transient proteinuria cohort experienced good graft outcome--namely, 87.5% one-year and 52.5% five-year actuarial graft survivals, which was similar to that observed in patients without proteinuria. In contrast, 52.4% of the 63 patients with nontransient proteinuria experienced graft loss within a median time of 6.1 months. The one- and five-year actuarial graft survivals in patients with nontransient proteinuria were 75.3% and 37.5%, respectively. Among the 63 patients with nontransient proteinuria, histopathologic diagnosis included chronic rejection in 19, transplant glomerulopathy in 14, acute rejection in 9, glomerulonephritis (GN) in 7 including 2 cases of membranous GN, and nonspecific interstitial fibrosis in 10 cases. Despite the overall poor prognosis for graft survival among the entire cohort of patients with nontransient proteinuria, the seven with allograft GN maintained prolonged graft function. They showed an 83.3% five-year actuarial graft survival versus 31.2% in patients with other causes of proteinuria (P = 0.043). These results suggest that posttransplant proteinuria in CsA-treated renal transplant recipients arises primarily as a consequence of allograft rejection and portends a poor graft outcome.

Exacerbation of cyclosporine toxicity by concomitant administration of erythromycin.

Cyclosporine (CsA), an immunosuppressive drug widely used in clinical organ transplantation, causes a variety of side effects, including parenchymal complications of nephrotoxicity and hepatotoxicity. Erythromycin ethinylsuccinate (EES), a macrolide antibiotic frequently administered to transplant patients afflicted with pneumonias caused by Mycoplasma pneumoniae and Legionella pneumophila, markedly potentiated parenchymal drug toxicity in nine (three renal and six cardiac) CsA-treated allograft recipients. The mean and median blood urea nitrogen (BUN), creatinine, and total bilirubin increased upon initiation of EES treatment: in the renal recipients from 27, 1.7, and 0.5 mg/dl, respectively, before, to a mean and median of 81/101, 8.3/3.9, and 2.1/1.2 mg/dl during, and to 72/22, 1.9/1.7, and 0.6/0.5 mg/dl after cessation of EES treatment. The median serum radioimmunoassay (RIA)-determined CsA trough value of 147 ng/ml prior, rose to a zenith of 1125 ng/ml during, EES therapy. In the six cardiac recipients, the mean and median BUN, creatinine, and total bilirubin of 51/45, 1.5/1.3, 1.2/1.3 mg/dl, respectively, before, rose to 100/91, 3.7/3.6, and 2.3/2.1 mg/dl during, and fell to 49/44, 1.8/2.1, and 1.0/0.8 mg/dl after, cessation of EES. The mean serum CsA trough value of 185 ng/ml rose to 815 ng/ml during EES administration. Since EES and CsA are both metabolized by the hepatic cytochrome P450 mixed-function oxidase system, simultaneous use of these two drugs may decrease CsA metabolism, with consequent elevation of blood levels and induction of CsA toxicity. Therefore, blood level monitoring and careful regulation of CsA dose are necessary, in order to achieve the safe use of EES in transplant recipients.