End-to-end anastomosis as a superior repair type to prevent recurrence of arteriovenous fistula aneurysms and improve patency outcomes.

BACKGROUND: Arteriovenous fistulae (AVF) complicated by aneurysms are repaired through several mechanisms. Little is known about risk factors for aneurysm recurrence or the efficacy of subsequent repair of recurring aneurysms. METHODS: About 291 patients underwent AVF aneurysm repair between 2009 and 2019 at a large urban medical center. Patients who underwent staged repair, had a primary graft with pseudoaneurysm, were status-post kidney transplant, or using other dialysis access at the time of repair were excluded. One hundred sixty-two patients were included in the study, of which 52 developed a secondary aneurysm. Chi-square and t-test analyses were used to compare demographics. Multivariate logistic regression was used to examine independent risk factors for aneurysm recurrence. Of the 52 patients with recurrent aneurysms, 41 were repaired again. Patency was examined for each group 1 year postoperatively. RESULTS: Patients without secondary aneurysms were more likely to have a Charlson Comorbidity Index score ⩾5 (p = 0.045). Males were 2.8 times more likely to develop a secondary aneurysm compared to females (p = 0.023). Patients who underwent elective compared to emergent or urgent surgery for primary aneurysms were significantly less likely to recur (OR = 0.222; p = 0.016). Primary aneurysms repaired by end-to-end anastomosis, compared to aneurysmorrhaphy or graft, were significantly less likely to recur (OR = 0.239; p = 0.041). Among patients with secondary aneurysms, those repaired via end-to-end anastomosis had a significantly higher primary patency rate 1 year postoperatively (p = 0.024). Secondary aneurysm repairs exhibited 1-year primary and secondary patency rates of 51.2% and 82.9%, respectively. CONCLUSIONS: End-to-end anastomosis reduces risk of recurrence and demonstrates superior patency rates when repairing recurrent aneurysms. It remains unclear why some patients are prone to aneurysm recurrence, however continued attempts to repair existing vascular access are proven to be successful.

Graft repair of arteriovenous fistula aneurysms is associated with decreased long-term patency.

INTRODUCTION: Arteriovenous fistula (AVF) aneurysms are a chronic complication which can be disfiguring, painful, and can rupture. Here, we compare the outcomes between three different methods of AVF aneurysm repair. METHODS: One-way ANOVA, Chi-square, and Fisher Exact analyses were used to compare demographics. Multivariate logistic regression compared outcomes. Kaplan-Meier estimate illustrated long-term fistula patency. RESULTS: There were no differences between demographics in the aneurysmorrhaphy, end-to-end anastomosis, and synthetic graft groups. The odds of patients who received graft repair losing primary patency within one year compared to the aneurysmorrhaphy group was 3.5 (p = 0.025). Graft repair patients were 6.7 times more likely to develop an infection compared to aneurysmorrhaphy (p = 0.014). Synthetic grafts also exhibited accelerated rates of complete access loss compared to autogenous methods (p = 0.034). CONCLUSIONS: Graft repair of AVF aneurysms results in higher rates of infection and decreased primary and ultimate patency compared to autogenous repair techniques. Therefore, synthetic grafts should be avoided whenever possible.

Economic evaluation of suture versus clip anastomosis in arteriovenous fistula creation.

OBJECTIVE: Techniques such as the use of nonpenetrating vascular clips for arteriovenous fistula (AVF) anastomotic creation have been developed in an effort to reduce fistula-related complications. However, the outcomes data for the use of clips have remained equivocal, and the cost evaluations to support their use have been largely theoretical. Therefore, the present study aimed to determine both the clinical and the cost outcomes of AVFs created with nonpenetrating vascular clips compared with the continuous suture technique during a 10-year period at a single institution. METHODS: All patients undergoing AVF creation in the upper extremity from 2009 through 2018 were retrospectively analyzed. The patient demographics and AVF outcomes were collected and compared stratified by the surgical technique used. A cost analysis was performed of a subgroup of patients from 2013 to 2018. RESULTS: During the 10-year study period, 916 AVFs were created (79% using the continuous suture technique and 21% using nonpenetrating vascular clips). Patient demographics and comorbid conditions did not differ between the two groups, and no differences were present in maturation, primary patency, assisted primary patency, or complication rates between the two groups at 1 year. The suture group had a shorter time to maturation (4.3 months vs 5.5 months; P < .01) and improved secondary patency compared with the clip group (77.13% vs 69.59%; P = .03) The cost analysis of the procedures revealed a significant difference in direct costs (suture, $1389.26 vs clip, $1716.51; P < .01) and contribution margin (suture, $1770.19 vs clip, $1128.36; P < .01) for the two groups. CONCLUSIONS: Both suture and clip techniques in AVF creation demonstrated equivalent rates of maturation, primary patency, assisted primary patency, and complications at 1 year with higher expense associated with the use of clips. Thus, in an effort to reduce the economic burden of healthcare in the United States, the findings from the present study support the preferential use of the standard polypropylene suture technique when creating upper extremity AVFs.

Efficacy and safety of bleselumab in kidney transplant recipients: A phase 2, randomized, open-label, noninferiority study.

This study assessed the efficacy and safety of the anti-CD40 monoclonal antibody bleselumab (ASKP1240) in de novo kidney transplant recipients over 36 months posttransplant. Transplant recipients were randomized (1:1:1) to standard of care (SoC: 0.1 mg/kg per day immediate-release tacrolimus [IR-TAC]; target minimum blood concentration [Ctrough ] 4-11 ng/mL plus 1 g mycophenolate mofetil [MMF] twice daily) or bleselumab (200 mg on days 0/7/14/28/42/56/70/90, and monthly thereafter) plus either MMF or IR-TAC (0.1 mg/kg per day; target Ctrough 4-11 ng/mL days 0-30, then 2-5 ng/mL). All received basiliximab induction (20 mg pretransplant and on days 3-5 posttransplant) and corticosteroids. One hundred thirty-eight transplant recipients received ≥1 dose of study drug (SoC [n = 48]; bleselumab + MMF [n = 46]; bleselumab + IR-TAC [n = 44]). For the primary endpoint (incidence of biopsy-proven acute rejection [BPAR] at 6 months), bleselumab + IR-TAC was noninferior to SoC (difference 2.8%; 95% confidence interval [CI] -8.1% to 13.8%), and bleselumab + MMF did not demonstrate noninferiority to SoC (difference 30.7%; 95% CI 15.2%-46.2%). BPAR incidence slightly increased through month 36 in all groups, with bleselumab + IR-TAC continuing to demonstrate noninferiority to SoC. Bleselumab had a favorable benefit-risk ratio. Most treatment-emergent adverse events were as expected for kidney transplant recipients (ClinicalTrials.gov NCT01780844).

Arteriovenous fistula patency in the 3 years following vonapanitase and placebo treatment.

OBJECTIVE: This study explored the long-term outcomes of arteriovenous fistulas treated with vonapanitase (recombinant human elastase) at the time of surgical creation. METHODS: This was a randomized, double-blind, placebo-controlled trial of 151 patients undergoing radiocephalic or brachiocephalic arteriovenous fistula creation who were randomized equally to placebo, vonapanitase 10 µg, or vonapanitase 30 µg. The results after 1 year of follow-up were previously reported. The current analysis occurred when the last patient treated was observed for 3 years. For the current analysis, the primary end point was primary patency; the secondary end points included secondary patency, use of the fistula for hemodialysis, and rate of procedures to restore or to maintain patency. RESULTS: There was no significant difference in the risk of primary patency loss with vonapanitase 10 µg or 30 µg vs placebo. When seven initial patency loss events related to cephalic arch and central vein balloon angioplasty were excluded, the risk of patency loss was reduced with vonapanitase overall (hazard ratio [HR], 0.63; P = .049) and 30 µg (HR, 0.51; P = .03). In patients with radiocephalic fistulas (n = 67), the risks of primary and secondary patency loss were reduced with 30 µg (HR, 0.37 [P = .02] and 0.24 [P = .046], respectively). The rate of procedures to restore or to maintain fistula patency was reduced with 30 µg vs placebo (0.23 vs 0.72 procedure days/patient/year; P = .03) and also reduced in patients with radiocephalic fistulas with 30 µg vs placebo (0.17 vs 0.85 procedure days/patient/year; P = .048). CONCLUSIONS: In this study, vonapanitase did not significantly improve primary patency in the primary analysis but did significantly improve primary patency in an analysis that excluded patency loss due to cephalic arch and central vein balloon angioplasty. In patients with radiocephalic fistulas, 30 µg significantly improved primary and secondary patency. Vonapanitase 30 µg decreased the rate of procedures to restore or to maintain patency in the analysis that included all patients and in the subset with radiocephalic fistulas.

Outcomes after combined liver-kidney transplant vs. kidney transplant followed by liver transplant.

INTRODUCTION: The decision for isolated kidney transplant (KT) vs. combined liver-kidney transplant (CLKT) in patients with end-stage renal disease (ESRD) with compensated cirrhosis remains controversial. We sought to determine outcomes of patients requiring listing for a liver transplant (LT) following either a cadaveric or living donor KT and compare these outcomes to similar patients receiving a CLKT. METHODS: Our dataset included the United Network for Organ Sharing (UNOS)/Standard Transplant and Analysis and Research (STAR) kidney files from 1987 to 2012 after being joined with the liver files from 2002 to 2012. Outcomes of patients who received a CLKT with an international normalized ratio (INR) ≤1 and total bilirubin ≤1 were compared to patients who received a primary KT and subsequently required listing for LT between zero and five yr or after five yr. RESULTS: For the three groups, 244 patients had a CLKT, 216 were wait-listed for LT between zero and five yr after KT (0-5 WL), and 320 were wait-listed five yr after KT (+5 WL). From the time of KT, the 0-5 WL group had significantly worse survival than the CLKT group and the +5 WL group. The +5 WL had the best survival of all groups. For the 0-5 WL group, 45% underwent LT and 40% died while waiting compared to the +5 WL group with 53% having LT and 26% died while waiting. At the time of LT, the 0-5 WL group had a higher model for end-stage liver disease (MELD) score, higher incidence of being in the ICU at the time of transplant, and higher incidence of requiring life support. From the time of LT, the CLKT trended toward better survival (p = 0.0549) than both the 0-5 WL and +5 WL groups, which had equivalent survival. CONCLUSION: The 0-5 WL group is a higher risk group with poorer survival due to a higher incidence of dying on the waitlist. Better identification of patients with a high risk for hepatic decompensation following KT and agreement for regional exception for LT in the event of decompensation may improve utilization of organs and better survival for those patients.

Human type I pancreatic elastase treatment of arteriovenous fistulas in patients with chronic kidney disease.

OBJECTIVE: This study explored the safety and efficacy of recombinant type I pancreatic elastase (PRT-201) topically applied once to the external surface of an arteriovenous fistula. METHODS: This was a randomized, double-blind, placebo-controlled trial. Adults with kidney disease undergoing creation of a radiocephalic fistula (RCF) or brachiocephalic fistula were randomized to treatment with placebo (n = 51), PRT-201 at 10 µg (n = 51), or PRT-201 at 30 µg (n = 49). The primary efficacy measure was unassisted primary patency (PP) over 1 year. Secondary efficacy measures were secondary patency (SP), unassisted maturation by ultrasound interrogation, use for hemodialysis, and hemodynamically significant lumen stenosis. RESULTS: Median PP was 224 days for placebo and >365 days for the PRT-201 groups. At 1 year, 45%, 54%, and 53% of placebo, 10-µg, and 30-µg patients retained PP. The risk of PP loss was nonsignificantly reduced for 10 µg (hazard ratio [HR], 0.69; P = .19) and 30 µg (HR, 0.67; P = .17) vs placebo. In the subset (44% of patients) with a RCF, the median PP was 125 days for placebo and >365 days for the PRT-201 groups. At 1 year, 31%, 50%, and 63% of placebo, 10-µg, and 30-µg RCFs retained PP. The risk of RCF PP loss was nonsignificantly reduced by 10 µg (HR, 0.59; P = .18) and significantly reduced by 30 µg (HR, 0.37; P = .02) vs placebo. At 1 year, 77%, 81%, and 83% of placebo, 10-µg, and 30-µg patients retained SP. The risk of SP loss was nonsignificantly reduced for 10 µg (HR, 0.79; P = .61) and 30 µg (HR, 0.76; P = .55) vs placebo. In the subset with RCFs, 65%, 82%, and 90% of placebo, 10-µg, and 30-µg patients retained SP at 1 year. The risk of RCF SP loss was nonsignificantly reduced for 10 µg (HR, 0.45; P = .19) and 30 µg (HR, 0.27; P = .08) vs placebo. At month 3, 67%, 87% (P = .03), and 92% (P < .01) of the placebo, 10-µg, and 30-µg group fistulas had unassisted maturation by ultrasound interrogation. At month 3 in the subset with an RCF, 47%, 74% (P = .17), and 93% (P < .01) of placebo, 10-µg, and 30-µg group fistulas had unassisted maturation by ultrasound interrogation. Adverse event reports were not meaningfully different between groups. CONCLUSIONS: PRT-201 appeared safe. The primary efficacy end point was not met. However, both PRT-201 doses were associated with improved unassisted maturation. The 30-µg dose was associated with increased PP in the subset with RCF.

Balloon-assisted over-the-wire technique for placement of the venous outflow component of the Hemodialysis Reliable Outflow (HeRO) device.

A modified technique for placement of the venous outflow component (VOC) of the Hemodialysis Reliable Outflow (HeRO) device (Hemosphere Inc, Minneapolis, Minn) is described. The purpose of the technique is to improve the system's trackability and facilitate device insertion in patients with central venous occlusion. Device preparation requires placement of a 6-mm × 4-cm angioplasty balloon within the leading end of the VOC. The leading 2 cm of the balloon are placed just distal to the radiopaque marker of the VOC. The balloon is inflated to profile and locked in this position within the leading end of the VOC. The VOC and balloon combination is advanced over the wire through the 20F peel-away sheath provided by the manufacturer. The described technique was used to successfully implant the HeRO device in 12 patients with central venous occlusion. This technique is recommended for placement of the VOC of the HeRO device in patients with central venous occlusions.

YSPSL (rPSGL-Ig) for improvement of early renal allograft function: a double-blind, placebo-controlled, multi-center Phase IIa study.

INTRODUCTION: Recombinant P-selectin glycoprotein ligand IgG fusion protein, rPSGL-Ig (YSPSL), a fusion protein of human P-selectin ligand and IgG1-Fc, blocks leukocyte adhesion and protects against ischemia reperfusion injury (IRI) in animal models. PATIENTS AND METHODS: This randomized 15-center, double-blind, 59-patient Ph2a study assessed YSPSL's safety in recipients of deceased-donor kidney allografts and its potential efficacy in improving early graft function. Two doses and two dosing modalities were evaluated. RESULTS: No drug-specific toxicities or increased adverse event rates were noted. Two YSPSL-treated patients died of causes determined as unrelated to study drug. YSPSL did not reduce the incidence of dialysis within the first week post-transplant (41% in treated vs. 20% in placebo patients). Renal function endpoints scored at post-operative days 1 & 2 were also not impacted by YSPSL. However, at day 5, the fraction of patients with serum creatinine above 6 mg/dL was lower in the YSPSL vs. placebo group (26% vs. 55%, p = 0.043). Large variations in the dialysis-delayed graft function (DGF) rates were observed between centers, independently of treatment assignment, indicating subjectivity of this endpoint. CONCLUSION: In this first Ph2a study in kidney transplantation, YSPSL was safe but did not impact the dialysis-DGF rate. Further studies with more objective efficacy endpoints are required to define the impact of YSPSL on early renal allograft function.

Renal function with cyclosporine C2 monitoring, enteric-coated mycophenolate sodium and basiliximab: a 12-month randomized trial in renal transplant recipients.

BACKGROUND: Cyclosporine exposure, as estimated by the area under the curve (AUC), predicts outcomes in renal transplantation. Cyclosporine concentration at two h post-dose (C(2)) has been shown to be the most reliable, single-point surrogate marker for AUC. The objective of this study was to measure renal function beyond month 2 post-transplant using two different C(2) maintenance targets in combination with enteric-coated mycophenolate sodium (EC-MPS), corticosteroids, and basiliximab induction. METHODS: In this open-label, multicenter trial, renal transplant recipients entered one of two randomized groups at day 61 post-transplant: group A (higher-C(2) range) or group B (lower-C(2) range). RESULTS: Patients (164) were recruited, and 141 patients were entered the randomized groups (group A, n = 66; group B, n = 75). At 12 months, the mean calculated creatinine clearance was significantly greater in group B than in group A (79.2 vs. 71.0 mL/min, p < 0.05). Biopsy-proven acute rejection occurred in 14.7% patients in group B and in 24.2% patients in group A (n.s.). During the 12-month trial, 17.7% patients discontinued EC-MPS because of adverse events. Group B (44.0%) had fewer serious adverse events when compared with group A (62.1%; p = 0.04). Overall patient and graft survival were 99.4% and 95.7% respectively. Among 99 high-risk patients (i.e., African-American race, previous transplant, PRA >35% or >4 HLA mismatches), mean creatinine clearance at 12 months was 65.6 mL/min and biopsy-proven rejection occurred in 20.2% patients. CONCLUSIONS: Low cyclosporine C(2) levels are associated with improved renal function compared with higher C(2) levels when used in conjunction with EC-MPS, steroids and basiliximab induction. EC-MPS with low cyclosporine C(2) levels, corticosteroids and basiliximab provides excellent renal function with good efficacy even in high-risk patients.

A prospective, randomized trial of tacrolimus in combination with sirolimus or mycophenolate mofetil in kidney transplantation: results at 1 year.

BACKGROUND: This is the 1-year report of a randomized, multicenter, clinical trial comparing the combination of sirolimus or mycophenolate mofetil (MMF) with tacrolimus-based immunosuppression in kidney transplantation. METHODS: Prior to transplantation, recipients were randomized to receive tacrolimus plus corticosteroids with either sirolimus (n=185) or MMF (n=176). The incidence of biopsy-confirmed acute rejection at 6 months was the primary endpoint of the study. Patient and graft survival, renal function, study drug dosing and discontinuations were evaluated at 1 year. RESULTS: At 1 year, there was no difference in patient survival (95.7% sirolimus vs. 97.2% MMF; P=0.45) or graft survival (90.8% sirolimus vs. 94.3% MMF; P=0.22). Patients without delayed graft function (DGF) receiving MMF had significantly better graft survival (99% vs. 93%; P=0.01). Patients receiving a transplant from a live donor had a trend towards better graft survival with MMF as compared to sirolimus (98% vs. 91%; P=0.07). Patients receiving sirolimus had a significantly higher incidence of study drug discontinuation (26.5% vs. 14.8% MMF; P=0.006). Patients receiving MMF had significantly better renal function as shown by median serum creatinine levels (1.3 mg/dL vs. 1.5 mg/dL; P=0.03) and a trend towards higher calculated creatinine clearance (CrCl), (58.4 ml/min vs. 54.3 ml/min; P=0.06). More patients in the sirolimus group had a serum creatinine >2.0 mg/dL, (20.4% vs. 11.0%; P=0.02). CONCLUSIONS: Tacrolimus is safe and effective in live and deceased donor kidney transplantation when given in combination with sirolimus or MMF. Patient and graft survival were excellent in both arms. Renal function is superior for patients treated with tacrolimus + MMF combination.

An open-label, pilot study evaluating the safety and efficacy of converting from calcineurin inhibitors to sirolimus in established renal allograft recipients with moderate renal insufficiency.

This pilot study was designed to evaluate the safety and efficacy of converting from a calcineurin inhibitor (CI) to a sirolimus (SRL)-based regimen in established renal transplant recipients with moderate renal insufficiency. Sixty renal transplant recipients on CI-based immuno-suppression with a serum creatinine (SCr) between 159 and 265 microM (1.8 and 3.0 mg/dL) and a glomerular filtration rate (GFR) between 30 and 70 mL/min were enrolled. SRL dosing was dependent upon concomitant immunosuppressive therapy. The mean patient age was 45 yr and the mean time from transplant to study enrollment was 60.8 months (range: 7-198). The median SCr was 168 microM (1.9 mg/dL) and the median GFR was 51 mL/min. Twelve months after conversion the patient and graft survival rates were 96.7% and 95%, respectively. The incidence of biopsy-proven acute rejection was 3.3% (two cases reported, Banff grades IA and IB). The median SCr and median creatinine clearance were 168 microM (1.9 mg/dL) and 53 mL/min, respectively. Hyperlipidemia, diarrhea, peripheral edema, rash, and anemia were the most commonly reported adverse events. Patients with moderate renal insufficiency can be converted from CI to SRL-based therapy and maintain renal function over a 1-yr period.

Randomized trial of tacrolimus in combination with sirolimus or mycophenolate mofetil in kidney transplantation: results at 6 months.

BACKGROUND: This is the first report of a randomized, multicenter, clinical trial comparing the combination of sirolimus or mycophenolate mofetil (MMF) with tacrolimus-based immunosuppression in kidney transplantation. Results at 6 months of follow-up are presented. METHODS: Before transplantation, patients were randomized to receive tacrolimus plus corticosteroids with sirolimus (n=185) or MMF (n=176). The primary endpoint of the study was the incidence of biopsy-confirmed acute rejection. Patient and graft survival, renal function, and composite endpoints also were evaluated. Safety was assessed by monitoring laboratory parameters and adverse events. RESULTS: By 6 months of follow-up, the incidence of biopsy-confirmed acute rejection was similar in both treatment groups (13.0% tacrolimus+sirolimus vs. 11.4% tacrolimus+MMF; P=0.64 log-rank). Patient survival (97.3% tacrolimus+sirolimus vs. 97.7% tacrolimus+MMF) and graft survival (93.0% tacrolimus+sirolimus vs. 95.5% tacrolimus+MMF) were equivalent (P=0.53, overall survival log-rank). There was a significantly higher incidence of study drug discontinuation in patients receiving sirolimus (21.1% vs. 10.8%; P=0.008). Renal function was significantly better in the MMF-treatment group (serum creatinine 1.44+/-0.45 mg/dL vs. 1.77+/-1.42 mg/dL; P=0.018). Hyperlipidemia was significantly more prevalent in the sirolimus-treatment group. Diastolic blood pressure was significantly higher in sirolimus-treated patients. There were significantly more leukopenia and gastrointestinal adverse events in the MMF-treatment group. The incidence of posttransplant diabetes mellitus was 7.6% in the sirolimus group and 7.7% in the MMF group. CONCLUSION: Tacrolimus is equally effective in renal transplantation when combined with sirolimus or MMF. The tacrolimus-MMF combination may be superior in terms of improved renal function and improved cardiovascular risk factors including hyperlipidemia and hypertension.

A long-term comparison of tacrolimus (FK506) and cyclosporine in kidney transplantation: evidence for improved allograft survival at five years.

BACKGROUND: The 1-year results of the Phase III U.S. Multicenter Trial comparing tacrolimus (FK506)- and cyclosporine (CsA)-based immunosuppressive therapy in kidney transplantation revealed a significant reduction in the incidence and severity of acute rejection episodes among patients maintained on tacrolimus. The present report at 5 years of follow-up focuses on the long-term impact of tacrolimus treatment on kidney allograft outcome. METHODS: The study protocol permitted crossover of patients to the alternate treatment arm under stringent conditions. The effect of crossover on graft survival was analyzed. Cardiovascular risk factors and serious adverse events were also monitored over 5 years. RESULTS: Intent-to-treat analysis revealed equivalent patient and graft survival between treatment arms at 5 years of follow-up (79.1% vs. 81.4%; P=0.472 and 64.3% vs. 61.6%; P=0.558 among tacrolimus and CsA-treated patients, respectively). However, the rate of crossover was significantly higher among patients randomized to receive CsA-based therapy (27.5% vs. 9.3%; P<0.001). The incidence of treatment failure (43.8% vs. 56.3%; P=0.008) was significantly lower among tacrolimus-treated patients. Graft survival was significantly improved in the tacrolimus treatment arm when crossover due to rejection was counted as graft failure (63.8% vs. 53.8%; P=0.014). Tacrolimus therapy was also associated with a significantly reduced requirement for medications to control hypertension and hyperlipidemia. There was a substantial rate of reversal of tacrolimus-associated insulin dependence. CONCLUSION: Tacrolimus-based therapy resulted in significantly reduced risk of graft failure, without an increase in the incidence of adverse events associated with long-term immunosuppression.

Experiences with leflunomide in solid organ transplantation.

BACKGROUND: Leflunomide (Arava), a drug widely used for treatment of rheumatoid arthritis, has a very promising background in experimental transplantation. Its activity in experimental models of chronic rejection, its synergy with calcineurin phosphatase inhibitors, and its inhibitory effects on herpes virus replication are compelling reasons to pursue its clinical evaluation in transplantation. We report the use of this drug over the past 3 years in various clinical situations. METHODS: A retrospective review was performed in 53 liver and kidney transplant recipients receiving Arava. A single-dose pharmacokinetic (PK) study was first performed in stable, renal transplant recipients, and an initially targeted serum level of 100 microg/mL (300 microM) was calculated to require a loading dose of 1200-1400 mg over a 7-day period. We correlate the appearance of toxicity with serum levels of active drug and review the outcomes in patients whose clinical condition required dose reductions of conventional immune suppressive drugs. RESULTS: Fifty-three patients received leflunomide from 5 days to more than 430 days, and 37 patients received the drug for more than 60 days. The primary toxicity was anemia in the renal transplant patients and elevation of liver enzymes in the liver transplant patients. At comparable oral doses, serum levels were substantially lower and anemia more common in patients with serum creatinine >3 mg/dL. In liver and renal recipients with serum creatinine <3 mg/dL, the drug was well tolerated and dose-limiting side effects occurred in less than 15% when drug serum levels were less than 80 microg/ml. Patients with serum creatinine >3 mg/dL often required serum levels of active drug reduced to <60 microg/mL. In 12 of 18 renal patients treated for 200 days or more, the dose of cyclosporine or Prograf was reduced by a mean of 38.5% and stopped in one patient. The prednisone dose was reduced by a mean of 25% in these same 13 patients. Cyclosporine or FK506 was stopped completely in four liver recipients and reduced by 65% in another patient. No evidence of acute rejection developed in any of these liver or kidney transplant patients. CONCLUSION: Leflunomide seems to possess substantial immune suppressive potency in renal and liver transplant recipients and may be safely dosed for more than 300 days. The data suggest that calcineurin phosphatase inhibitors and prednisone can be safely reduced in patients with serum levels of active drug above 50 microg/mL. Because of a wide inter-patient range of active metabolite terminal half-life (>300%), monitoring of serum levels would seem to be an important part of its evaluation.