Incidence, therapy, and consequences of lymphocele after sirolimus-cyclosporine-prednisone immunosuppression in renal transplant recipients

Rapamycin successfully treats post-transplant autoimmune hepatitis

Rapamycin (Rapa), one of the newer immunosuppressants has been found to control and prevent autoimmune features in animal models. This is the first report describing the successful control of post-transplant autoimmune hepatitis (AIH) with Rapa. Post-transplant AIH is diagnosed in the presence of raised transaminases, elevated immunoglobulin G, presence of autoantibodies and histologic changes consistent with AIH on liver biopsy. It may represent a recurrence of the original AIH that led to transplantation or present as a de novo AIH after liver transplant. Post-transplant AIH has conventionally been treated with Prednisolone (Pred) and Azathioprine (AZA). In this report, tailoring of immunosuppression after diagnosis of post-transplant AIH is described with special emphasis on those treated successfully with Rapa. Fifteen of 21 patients responded to treatment with an increase in dose of Pred and addition of AZA or Mycophenolate Mofetil (MMF) to calcineurin inhibitor. Five non-responders and one other patient with post-transplant AIH were treated with addition of Rapa. All six responded to treatment but drug was withdrawn in one patient. Adverse events were minimal. Rapa may prove to be an important addition in the control of autoimmune liver disease.

Rabbit Antithymocyte Globulin: A Postoperative Risk Factor for Sirolimus-Treated Renal Transplant Patients?

AIMS

Randomized controlled studies suggest an increased incidence of perioperative wound complications among sirolimus-treated renal transplant patients. The present study analyzed the effect of rabbit antithymocyte globulin (rATG) on these postoperative complications.

METHODS

Four hundred and twelve renal transplants were performed and managed postoperatively at two University-affiliated hospitals between January 1, 2001, and December 31, 2003. The patients received corticosteroids and Sirolimus, with delayed introduction of cyclosporine when the serum creatinine had decreased below 2.5 mg/dL. Two groups of patients were discriminated: group 1 received Basiliximab 20 mg on day 0 and day 4 (n = 283); group 2 recipients with a high panel of reactive antibody (PRA > 20%) and retransplant patients received rATG for induction (n = 129) for a maximum of 2 weeks postoperatively. The incidence of rejection was 14.5% for group 1 vs. 8.5% for group 2 patients. To avoid confounding variable associated with the rejection treatment, any patient with rejection was excluded for statistical analysis, as were patients with follow- up less than 30 days. The final study group for analysis included 350 patients: 235 with Basiliximab induction (group 1) and 115 rATG induction (group 2). The mean follow-up was 21.8 +/- 11 months. Differences in the incidences of postoperative hernia, wound infections, or lymphoceles requiring any form of drainage were analyzed for statistical significance using the chi-square test.

RESULTS

The percentage of patients with wound complications was 26.0% versus 39.1% (P < .025) for group 1 versus group 2, respectively. Incisional hernias occurred in 10.6% versus 18.3% patients (P < .05), wound infections in 11.1% versus 16.5% (P = NS), and lymphoceles in 10.6% versus 15.9% (P = NS) for the two groups, respectively.

CONCLUSIONS

rATG-induced renal transplants recipients treated with sirolimus, cyclosporine, and steroids show a significantly increased incidence of postoperative incisional hernias and a trend toward a greater number of lymphocele and wound infection complications.

No-Load Sirolimus With Tacrolimus and Steroids Is Safe and Effective in Renal Transplantation

AIM

Basiliximab (BX) induction, tacrolimus (TAC), and steroids have sharply reduced acute cellular rejection at our institution. However, late graft loss has continued, for which sirolimus (SL) was introduced into the protocol.

METHODS

From July 1, 2001 to December 31, 2003, 152 live donor (LD) renal transplant recipients received TAC (level 15 to 20 ng/mL) and steroids, with BX induction. One hundred twenty-two patients (Group 1) received SL (3 mg/d African-americans; 2 mg/d for others) starting on days 2 and 3. The SL level was adjusted to 8 to 10 ng/d, usually by weeks 3 to 4 posttransplant. The TAC doses were then progressively reduced. Records were reviewed for demographics, immunosuppressive drug levels, serum cholesterol and blood pressure, and complications. Graft and patient survival rates were calculated. Comparison was made to 53 LD recipients transplanted from July 1, 1998, to June 30, 2001 (Group 2) receiving BX, steroids and TAC, without SL. Recipients of deceased donor kidneys were excluded because of variability in kidney quality, ischemic time, and patient management.

RESULTS

Demographics were similar between groups: African Americans, 25% to 35%; mean age 36 years; mean HLA mismatch 3.7. Wound problems and infection were minimal in both groups. Mean serum creatinine and cholesterol and systolic and diastolic blood pressure measured periodically up to 1 year were similar, as was the incidence of rejection. In 25% of patients, SL was discontinued.

CONCLUSIONS

Gradual introduction of SL appears to be associated with minimal wound problems. With more aggressive reduction in TAC, better renal function, and better long-term graft survival may be attainable. We currently lower TAC levels to 5 ng/mL by 3 months.

A multicenter pilot study of early (4-day) steroid cessation in renal transplant recipients under simulect, tacrolimus and sirolimus

This study presents the first prospective multicenter study assessing sirolimus-based immunosuppression with early (4-day) corticosteroid withdrawal (CSWD) in renal transplantation. Immunosuppression included: anti-IL-2 receptor antibody and tacrolimus/sirolimus. Inclusion criteria included adult primary recipients. Exclusion criteria included: (i) African Americans, (ii) current PRA >50%, (iii) multiple organ transplants, (iv) WBC < 3000 cells/microL and (v) fasting hypercholesterolemia/hypertriglyceridemia. The primary endpoints were acute rejection and the proportion of patients off corticosteroids. Seventy-seven patients were enrolled: mean age of 49.7 +/- 12 years. Transplants included: cadaveric (26%) and living donor (74%). Patient and graft survival were 100%. Biopsy proven acute rejection occurred in 13%; presumptive rejection in 10.5%. Banff grades included: IA (seven patients), IB (one patient), IIA (one patient) and IIB (one patient). Renal function at 1 year: serum creatinine (1.18 +/- 0.06 mg/dL). Mean weight gain was minimal at 1 year: 3 +/- 2 kg/patient. Mild increases in total, LDL and HDL cholesterol were observed and new antilipid agent use occurred in 26 patients. In conclusion, early CSWD under tacrolimus/sirolimus-based immunosuppression in selected, low-risk renal transplant recipients provides: (i) excellent patient and graft survival, (ii) good renal function, (iii) reduced hyperlipidemia and antilipid agent use and (iv) low acute rejection rates.

Benefit-Risk Assessment of Sirolimus in Renal Transplantation

Sirolimus (rapamycin) is a macrocyclic lactone isolated from a strain of Streptomyces hygroscopicus that inhibits the mammalian target of rapamycin (mTOR)-mediated signal-transduction pathways, resulting in the arrest of cell cycle of various cell types, including T- and B-lymphocytes. Sirolimus has been demonstrated to prolong graft survival in various animal models of transplantation, ranging from rodents to primates for both heterotopic, as well as orthotopic organ grafting, bone marrow transplantation and islet cell grafting. In human clinical renal transplantation, sirolimus in combination with ciclosporin (cyclosporine) efficiently reduces the incidence of acute allograft rejection. Because of the synergistic effect of sirolimus on ciclosporin-induced nephrotoxicity, a prolonged combination of the two drugs inevitably leads to progressive irreversible renal allograft damage. Early elimination of calcineurin inhibitor therapy or complete avoidance of the latter by using sirolimus therapy is the optimal strategy for this drug. Prospective randomised phase II and III clinical studies have confirmed this approach, at least for recipients with a low to moderate immunological risk. For patients with a high immunological risk or recipients exposed to delayed graft function, sirolimus might not constitute the best therapeutic choice--despite its ability to enable calcineurin inhibitor sparing in the latter situation--because of its anti-proliferative effects on recovering renal tubular cells. Whether lower doses of sirolimus or a combination with a reduced dose of tacrolimus would be advantageous in these high risk situations remains to be determined. Clinically relevant adverse effects of sirolimus that require a specific therapeutic response or can potentially influence short- and long-term patient morbidity and mortality as well as graft survival include hypercholesterolaemia, hypertriglyceridaemia, infectious and non-infectious pneumonia, anaemia, lymphocele formation and impaired wound healing. These drug-related adverse effects are important determinants in the choice of a tailor-made immunosuppressive drug regimen that complies with the individual patient risk profile. Equally important in the latter decision is the lack of severe intrinsic nephrotoxicity associated with sirolimus and its advantageous effects on arterial hypertension, post-transplantation diabetes mellitus and esthetic changes induced by calcineurin inhibitors. Mild and transient thrombocytopenia, leukopenia, gastrointestinal adverse effects and mucosal ulcerations are all minor complications of sirolimus therapy that have less impact on the decision for choosing this drug as the basis for tailor-made immunosuppressive therapy. It is clear that sirolimus has gained a proper place in the present-day immunosuppressive armament used in renal transplantation and will contribute to the development of a tailor-made immunosuppressive therapy aimed at fulfilling the requirements outlined by the individual patient profile.

Wound-healing complications after kidney transplantation: a prospective, randomized comparison of sirolimus and tacrolimus

BACKGROUND

Sirolimus has been associated with an increased risk of wound-healing complications in several retrospective analyses. The authors compared the rates of wound-healing complications in renal allograft recipients in a prospective, randomized trial of sirolimus-mycophenolate mofetil-prednisone versus tacrolimus-mycophenolate mofetil-prednisone.

METHODS

All patients received antithymocyte globulin induction. In the first phase of the study, patients (n = 77) were included regardless of body mass index (BMI). In the second phase (n = 46 patients), the authors excluded patients with a BMI greater than 32 kg/m2, and the target trough sirolimus level was lowered to 10 to 15 ng/mL (previously 15-20 ng/mL). Multivariate logistic regression analyses were performed to identify predictors of wound complications.

RESULTS

Fifty-nine patients received tacrolimus and 64 received sirolimus and were included in subsequent analyses. The incidence of complications was 8% (5 of 59) in the tacrolimus group and 47% (30 of 64) in the sirolimus group (P < 0.0001). Rates of perigraft fluid collections, superficial wound infections, and incisional herniae were significantly higher in the sirolimus group. Multivariate logistic regression showed only sirolimus (P = 0.0001) and BMI (P = 0.0021) to independently correlate with complications. In the first phase of the study, the wound complication rate in the sirolimus group was 55% (21 of 38 patients). After excluding obese recipients and decreasing the target sirolimus level, the wound complication rate in the sirolimus group was 35% (9 of 26 patients; P = 0.1040).

CONCLUSIONS

The use of sirolimus-based immunosuppressive regimens leads to a higher incidence of wound-healing complications and will require new approaches to patient selection and management to decrease their incidence.

Sirolimus-induced angioedema

Sirolimus (SRL) is a macrolide immunosuppressant that has gained widespread use in organ transplantation. Its full spectrum of side-effects is yet to be defined. We describe herein three cases of SRL-induced angioedema (AE) in African-American (AA) primary renal allograft recipients who received SRL in combination with mycophenolate mofetil and steroids. In two cases, AE manifested after SRL was restarted after a period of discontinuation. The third case presented upon initial exposure to the drug. None of the patients was receiving any drug that has been previously associated with AE. Complete resolution occurred only after SRL was withdrawn. AE has not recurred in any of the patients during a follow-up period of up to 21 months. We conclude that AE is a previously unrecognized adverse event associated with SRL use. Close monitoring for this side-effect, especially in AA patients, is warranted.

The Influence of Various Maintenance Immunosuppressive Drugs on Lymphocele Formation and Treatment After Kidney Transplantation

PURPOSE

We compared the incidence of lymphocele formation and treatment in kidney transplant recipients given 3 immunosuppressive drug regimens.

MATERIALS AND METHODS

Consecutive series of adult kidney only recipients, including group 1-152 who received sirolimus/mycophenolate mofetil (MMF)/prednisone (P), group 2-168 who received cyclosporine/MMF/P and group 3-193 who received cyclosporine/azathioprine/P, were analyzed for post-transplantation lymphocele formation. All available records and imaging studies were reviewed, such as ultrasound, computerized tomography, magnetic resonance imaging etc, for peritransplant fluid collections greater than 2.5 cm. Demographic characteristics and the risk factors for lymphocele were compared in these 513 recipients using univariate and multivariate analysis.

RESULTS

The overall incidence of lymphocele formation was 174 of 513 cases (33.9%) and the incidence of treated lymphoceles was 81 of 513 (15.7%). In groups 1 to 3 the incidence was 45.5%, 33.9% and 24.7%, respectively. These differences were significantly higher in group 1 vs groups 2 or 3 (p = 0.014) but they were not significantly different between groups 2 and 3. Similarly the incidence of treated lymphoceles was 23%, 12.5% and 12.9%, respectively. Findings were again statistically higher in group 1 vs groups 2 and 3 (p = 0.003) but not statistically significant between groups 2 and 3. A greater number of group 1 patients required surgical interventions compared with those in groups 2 and 3 (13.8% vs 4.7% and 4.8%, respectively, p = 0.019). In addition, acute rejection (p = 0.001) and body mass index greater than 32 (p = 0.02) were significant risk factors on multivariate analysis.

CONCLUSIONS

The combination of sirolimus/MMF/P, obesity with a body mass index of greater than 30 kg/m and acute rejection are independent risk factors for lymphocele formation and treatment after kidney transplantation. Patients should be counseled and consideration should be given to prophylactic measures in this higher risk renal transplant population.

LYMPHEDEMA ASSOCIATED WITH SIROLIMUS IN RENAL TRANSPLANT RECIPIENTS1

Lymphoceles are common in renal transplant recipients who receive sirolimus (SRL). However, a recent MEDLINE search revealed no reports of lymphedema related to SRL. We describe three cases of lymphedema that resolved or improved on discontinuation of SRL. No other likely causes of lymphedema were discovered. Recognizing the association may lead to early discontinuation of SRL, which may prevent permanent disfigurement. It may also prevent unnecessary investigations. The mechanisms of this phenomenon are not clear. We hypothesize that increased lymph flow along with disrupted lymphatics in the affected extremities may explain this complication of SRL. Further studies are necessary to confirm our findings.

A randomized long-term trial of tacrolimus/sirolimus versus tacrolimus/mycophenolate mofetil versus cyclosporine (NEORAL)/sirolimus in renal transplantation. Ii. Survival, function, and protocol compliance at 1 year

BACKGROUND

In an attempt to reduce chronic calcineurin inhibitor induced allograft nephropathy in first cadaver and human leukocyte antigen non-identical living-donor renal transplantation, sirolimus (Siro) or mycophenolate mofetil (MMF) was tested as adjunctive therapy, with planned dose reductions of tacrolimus (Tacro) over the first year postoperatively. Adjunctive Siro therapy with a similar dose reduction algorithm for Neoral (Neo) was included for comparison.

METHODS

The detailed dose reduction plan (Tacro and Siro, group A; Tacro and MMF, group B; Neo and Siro, group C) is described in our companion report in this issue of Transplantation. The present report documents function, patient and graft survival, protocol compliance, and adverse events.

RESULTS

As mentioned (in companion report), group demographics were similar. The present study shows no significant differences in 1-year patient and graft survival but does show a trend that points to more difficulties in group C by way of a rising slope of serum creatinine concentration (P=0.02) and decreasing creatinine clearance (P=0.04). There were more patients who discontinued the protocol plan in group C. Thus far, no posttransplant lymphomas have appeared, and infectious complications have not differed among the groups. However, a greater percentage of patients in group C were placed on antihyperlipidemia therapy, with an (unexpected) trend toward a higher incidence of posttransplant diabetes mellitus in this group. Group A required fewer, and group B the fewest, antihyperlipidemia therapeutic interventions (P<0.00001).

CONCLUSIONS

This 1-year interim analysis of a long-term, prospective, randomized renal-transplant study indicates that decreasing maintenance dosage of Tacro with adjunctive Siro or MMF appears to point to improved long-term function, with reasonably few adverse events.

Testosterone concentrations and sirolimus in male renal transplant patients

Sirolimus damages the testes in animals; however, human data are sparse. We conducted a case-control study to obtain further insight into this issue and compared testosterone, follicle-stimulating hormone (FSH), luteinizing hormone (LH), and prolactin concentrations in matched renal transplant patients who did or did not receive sirolimus. We found that testosterone values were lower (11.2 +/- 6.3 nmol/L vs. 15.5 +/- 7.7 nmol/L, p < 0.05), in 28 sirolimus-treated patients, compared to 28 non-sirolimus-treated controls. Furthermore, these patients more commonly had testosterone concentrations that were below our reference value for normal men. In contrast, FSH and LH concentrations were higher while prolactin levels were not different. These data are consistent with sirolimus-related testosterone suppression and suggest a need for further studies.

Laparoscopic treatment of post renal transplant lymphoceles

BACKGROUND

Traditionally, a post transplant lymphocele (PTL) is drained by widely opening the wall connecting the lymphocele cavity to the intraperitoneal space via laparotomy. We hypothesize that laparoscopic techniques can be effectively used for the treatment of PTL.

METHODS

Patients requiring intervention for PTL between 1993 and 2002 were identified via a retrospective review. Results of drainage via laparotomy and laparoscopy were compared.

RESULTS

During the study period 685 renal transplants (391 cadaveric, 294 living) were performed. The incidence of lymphocele was 5% [34/685 (36 cases)]. The indications for surgical drainage were local symptoms (69%), graft dysfunction (14%), or both (17%). The mean time to surgical therapy was 4.9 months. Laparoscopic drainage was performed in 25 patients (74%) and open drainage in 9 patients (26%). Open procedures were performed in cases for: previous abdominal surgery (5), undesirable lymphocele characteristics or location (2), or with concomitant open procedures (3). There were no conversions or operative complications in either group. There was no difference in operative time for the laparoscopic group vs the open group (108 +/- 6 vs 123 +/- 18 min, p = 0.8). Hospital stay was significantly shorter for the laparoscopic group (1.7 +/- 0.8 vs 3.8 +/- 1.0, p = 0.0007), with 88% of laparoscopic patients being either overnight admissions or same day surgery. Two patients (5%) developed symptomatic recurrences requiring reoperation [1 laparoscopic (4%), 1 open (10%)].

CONCLUSIONS

Laparoscopic fenestration of a peritransplant lymphocele is a safe and effective treatment. The large majority of patients treated with laparoscopic fenestration were discharged within one day of surgery. Unless contraindications exist, laparoscopy should be considered first-line therapy for the surgical treatment of posttransplant lymphocele.

Comparison of sirolimus vs. mycophenolate mofetil on surgical complications and wound healing in adult kidney transplantation

Mycophenolate mofetil (MMF) and sirolimus impair wound healing. We compared sirolimus vs. MMF to determine the relative impact on surgical complications and wound healing in adult kidney transplant recipients. This retrospective, single center study of 235 adult kidney transplants performed between 1 January 2000 and 31 January 2002 identified 158 adult, kidney-only recipients treated with tacrolimus and prednisone, from which two groups were defined: group 1 (n = 84) received MMF, group 2 (n = 74) received sirolimus. The incidence of fluid collections, wound problems, dehiscence, and urine leak were compared. A multivariate stepwise logistical regression analysis was performed to identify risk factors. The overall incidence of complications was 21.5%, with rates significantly lower in group 1 (2.4%) vs. group 2 (43.2%, p < 0.0001). Regression analysis showed only sirolimus (p < 0.001) and hypo-albuminemia (p = 0.006) to independently correlate with complication occurrence. In subanalyses, lymphoceles correlated only with sirolimus (p = 0.003), while other wound problems also correlated with higher body mass index (p = 0.067). The use of sirolimus, tacrolimus and prednisone was associated with a greater incidence of lymphoceles, non-lymphocele perinephric fluid collections and other consequences of poor wound healing, as compared to contemporary patients treated with MMF, tacrolimus and prednisone.

Sirolimus does not increase the risk for postoperative thromboembolic events among renal transplant recipients

BACKGROUND

Deep venous thrombosis (DVT) tends to occur in greater frequency among cyclosporine (CsA)-treated renal-transplant recipients. Because administration of sirolimus may increase the whole-blood concentrations of CsA, we sought to assess the impact of the combination regimen on the incidence, predisposing factors, and consequences of postoperative DVT, transplant renal-vein or artery thrombosis, and pulmonary embolus.

METHODS

We retrospectively evaluated two cohorts of renal transplant recipients: CsA/prednisone (Pred)+/-azathioprine (n=136, group A) or sirolimus+CsA+Pred (n=354, group B) using Fisher's exact t and chi-square tests, as well as Kaplan-Meier analyses, odds ratios, and multiple logistic regression methods.

RESULTS

The 7 of 136 (5.1%) incidence of thrombotic events in group A was similar to the 20 of 354 (5.6%) incidence in group B (P=0.513; NS) and occurred no more frequently ipsilateral to the transplant. Although the occurrence of an acute-rejection episode was not associated with the DVT diagnosis, all affected patients displayed elevated serum creatinine (Scr) values, which remained slightly higher than baseline following recovery (group A 1.63+/-1.22-1.95+/-0.93 mg/dL; group B 1.70+/-1.11-2.01+/-0.88 mg/dL). Renal biopsies failed to show evidence of intrarenal coagulopathy. No patient lost a graft as a complication of DVT, nor did these events produce other lasting adverse effects. Patients in the sirolimus group showed a strong correlation between the occurrence of DVT and the previous existence of an ipsilateral or contralateral lymphocele.

CONCLUSION

Addition of sirolimus to a CsA+Pred regimen does not increase the incidence of postoperative thrombotic events among renal transplant recipients.

Higher surgical wound complication rates with sirolimus immunosuppression after kidney transplantation: a matched-pair pilot study

Sirolimus, a potent new immunosuppressant, has been anecdotally associated with surgical wound complications. We studied postoperative surgical wound complications in 15 kidney recipients receiving sirolimus, prednisone, and tacrolimus or cyclosporine (study group) compared with 15 recipients receiving tacrolimus, prednisone, and mycophenolate mofetil who were pair-matched for surgical wound complication risk factors. Surgical wound complications were defined as any complication related to the surgical transplant wound requiring reintervention. Fifty-three percent of the study group and 7% of the control group experienced more than one surgical wound complication (P=0.014), and the relaparotomy incidence was 33% and 7%, respectively. Four graft losses have occurred since the beginning of the study: one chronic rejection and two deaths with function in the study group, and one death with function in the control group. At 1 year, graft survival for study recipients compared with control recipients was 87% and 93%, respectively; patient survival was 93% in both groups. Recipients receiving sirolimus demonstrated a significantly higher surgical wound complication rate, but graft and patient survival were not affected. Peritransplant immunosuppression with sirolimus and steroids warrants careful consideration, particularly in recipients with surgical complication risk factors.

Sirolimus in liver transplantation

Since its introduction in renal transplantation in 1999, sirolimus is being used by an increasing number of liver transplant centers. Compared to the calcineurin inhibitors, sirolimus acts through a separate signal transduction pathway and has a myriad of important biologic effects including: inhibition of lymphocyte proliferation, inhibition of fibrosis and fibroblast proliferation, and antineoplastic effects. The clinical side-effect profile of this drug is also different than calcineurin inhibitors. Most important, sirolimus does not cause glucose intolerance, hypertension, or renal insufficiency. As a result, this drug offers significant potential advantages over conventional immunosuppressive agents. However, sirolimus may cause hyperlipidemia and has also been associated with hepatic artery thrombosis in liver transplant recipients. This review will summarize the published data on sirolimus in liver transplantation, focusing on the potential advantages and disadvantage of the use of this drug in liver transplant recipients. Finally, the potential benefits of antifibrosis and antineoplastic effects of sirolimus in liver transplant recipients will be discussed.

Clinical use of rapamycin in renal allograft recipients identifies its relevant toxicity profile and raises unsolved questions: a single-center experience

Rapamycin is an immunosuppressive drug with a distinct and unique mode of action and a specific side effect profile. We report here briefly on our personal clinical experience using this immunosuppressive drug in different combinations and settings. Rapamycin is without any doubt an efficient drug capable of preventing acute allograft rejection in a variety of immunosuppressive combinations. It is also a very potent drug that is not devoid of serious side effects. Infectious complications as a result of strong inhibition of the immune system are a frequent cause of hospitalization with severe morbidity and even mortality. Fungal infections and pneumonia are among the most devastating complications. As clinical experience with rapamycin grows and the therapeutic window of the drug can be further narrowed, these infectious complications will improve. Wound healing problems and lymphocoeles form another frequent surgical dilemma and are related to the antiproliferative properties of rapamycin. Last, hyperlipidemia warrants the use of statins in the majority of rapamycin-treated patients and whether this unfavorable side effect will offset the theoretically beneficial cardiovascular effects of the drug remains to be determined in controlled trials with long-term follow-up. Finally, the specific antiproliferative properties of rapamycin and the fact that it exerts no nephrotoxicity make this drug an alternative for calcineurin inhibitors and could make it an ideal candidate for treating chronic allograft dysfunction.