Progress with cyclosporine-sparing regimens

New Antiproliferative Immunosuppressive Agents

Since the early 1980s, the combination of cyclosporine, azathioprine, and prednisone has been the mainstay tripledrug immunosuppressive regimen used in transplantation. However, advances in drug research, design, and development have allowed for the introduction of new agents that have greatly increased the number of immunosuppressive agents available for use in transplant recipients. Particularly, the newer antiproliferative immunosuppressive drugs (agents that directly inhibit the proliferation of T and B lymphocytes) have had an important impact on patient outcomes posttransplant. These agents are mycophenolate mofetil and sirolimus.

Sirolimus conversion in liver transplant recipients with renal dysfunction: a prospective, randomized, single-center trial

This pilot trial was designed to assess the safety and efficacy of SRL in liver transplant recipients with renal dysfunction. Forty patients with renal dysfunction (24-hr CrCl 40-80 mL/min) were randomized to be withdrawn from the calcineurin inhibitor (CNI) and receive sirolimus (SRL) or to continue CNI (control arm). Improvement in 24-hour CrCl was seen in the SRL arm at 3 months (75 mL/min SRL vs. 56 mL/min control, P=0.012), whereas at 12 months there was a trend toward improvement in the SRL arm (72 mL/min SRL vs. 58 mL/min control, P=0.09). Two patients, one in each arm, developed steroid-sensitive rejection. Side effects of SRL were limited and included hyperlipidemia requiring treatment (15%), pruritus (5%), and mouth sores (25%). In this trial, SRL-based immunosuppression was a safe alternative to CNI. Although early improvements were observed, withdrawing CNI and replacing it with SRL did not result in a statistically significant improvement in renal function at 12 months of follow-up.

Improvement of renal dysfunction by conversion from calcineurin inhibitors to sirolimus after heart transplantation

BACKGROUND

Chronic renal dysfunction is a common occurrence after heart transplantation in patients treated with calcineurin inhibitors (CIs). We evaluated the renal-sparing effects of converting stable heart transplant patients with renal dysfunction from a CI to sirolimus.

METHODS

Beginning in 2000, heart transplant patients with renal dysfunction were converted from a CI to sirolimus. CI was abruptly discontinued and sirolimus added at 5 mg twice a day for 2 days and then 2 mg daily. The treatment goal was a 24-hour level of 6 to 12 ng/ml. All patients were also managed with mycophenolate mofetil (MMF) at 1,000 mg twice daily.

RESULTS

Eighty from a total of 235 cardiac transplant patients were converted to sirolimus. The average time post-transplant for conversion was 4.78 years (range 3 days to 16 years). The average age at transplant was 55.43 years (range 15 to 70). At a mean of 304 days post-conversion, the mean serum creatinine (sCr) decreased from 2.04 +/- 0.57 mg/dl pre-conversion to 1.64 +/- 0.48 mg/dl (p < 0.001). In patients whose sCr was <2.5 mg/dl before conversion, the mean SCr level decreased from 1.81 +/- 0.39 to 1.62 +/- 0.5 mg/dl post-conversion (p = 0.01), with no patient developing end-stage renal disease (ESRD). Four patients with sCr > or =2.5 developed ESRD requiring dialysis despite conversion. In the remaining 15 patients with sCr > or =2.5 mg/dl, the sCr decreased from 2.85 +/- 0.29 to 1.73 +/- 0.43 mg/dl (p = 0.001).

CONCLUSIONS

Conversion to sirolimus from CI is safe and has a renal-sparing effect in the management of heart transplant patients with chronic renal dysfunction. Based on these results, sirolimus has a role as a first-line immunosuppressive agent in heart transplant patients with renal dysfunction.

The impact of cyclosporine dose reduction with or without the addition of rapamycin on functional, molecular, and histological markers of chronic allograft nephropathy

BACKGROUND

Overexposure to cyclosporine is a risk factor for chronic allograft nephropathy (CAN) and dose reduction has been advocated. The purpose of this study was to determine the impact of adding the non-nephrotoxic immunosuppressant, rapamycin, after cyclosporine dose reduction in renal-allograft recipients with CAN.

METHODS

Thirty-one patients with biopsy-confirmed CAN were prospectively randomized to receive a 40% cyclosporine dose reduction with (rapamycin, n=16) or without (control, n=15) the addition of rapamycin 2 mg/day. Renal function and side-effect parameters were assessed. Patients had renal allograft biopsies taken at recruitment and after 6 months. Glomeruli were isolated from these and underwent total mRNA extraction followed by RT-PCR-ELISA to assess transforming growth factor-beta1, collagen III, TIMP-1, TIMP-2, and matrix metalloproteinase-2 expression. Samples were also stained with Sirius red and the percentage interstitial volume fraction quantified by computerized histomorphometric analysis. Data are presented as mean (+/-SD).

RESULTS

Patient characteristics and cyclosporine trough levels after dose reduction (rapamycin 68 [+/-21] vs. control 56 [+/-19] ng/mL, P=NS) were similar in both groups. Rapamycin patients had a significant fall in Cr-51 radioisotope glomerular filtration rate (31.6 [+/-8.9] to 27.3 [+/-8.6] mL/min, P<0.01) that was not significant in controls (29.5 [+/-10.4] to 27.0 [+/-8.0] mL/min, P=NS). Transforming growth factor-beta1 expression fell over time in control but remained constant in rapamycin patients. Conversely collagen III expression increased over the 6-month follow-up in rapamycin patients but not in controls. Both had comparable increases in TIMP-1 and matrix metalloproteinase-2 but only rapamycin patients developed a significant increase in TIMP-2. Sirius red-stained interstitial volume fraction fell over the study in controls (15.3-11.2%, P=0.06) but not in rapamycin patients (16.2-16.3%, P=NS).

CONCLUSION

Rapamycin (2 mg/day) did not improve functional, molecular, or histological outcome in patients with CAN after cyclosporine dose reduction. Further studies involving larger numbers of patients are necessary to confirm these findings.

New immunosuppressive drugs: an update

An increasing number of immunosuppressive drugs became available for clinical use over the past few decades. These include substances with recently recognized immunosuppressive properties, which needed careful evaluation in various trials before they could be approved for use in different diseases. The effectiveness of other agents was already established, but knowledge about their modes of action or the mechanisms that lead to side effects was acquired much later. This understanding also contributed to the development of new drugs that display synergistic effects or lack certain adverse effects. The greater choice afforded by such research endeavours allows us to select the best therapeutic strategy for an individual patient; however, this requires a comprehensive knowledge of the available options. The present review provides an update of current knowledge of the most important substances (including calcineurin and target of rapamycin inhibitors, regulators of gene expression, and inhibitors of purine and pyrimidine synthesis) and surveys some of the novel agents that are expected to play an important role in the future.