Tubular toxicity in sirolimus- and cyclosporine-based transplant immunosuppression strategies: an ancillary study from a randomized controlled trial.
BACKGROUND
Sirolimus has been promoted as an agent to provide immunosuppression for kidney transplant recipients that, in contrast to calcineurin inhibitors, would not be nephrotoxic. However, several reports have observed proteinuria in patients treated with sirolimus, ranging from low grade to nephrotic range. Accordingly, we compared markers of tubular and glomerular damage in an ancillary study of a randomized trial comparing sirolimus and cyclosporine.


METHODS
Single-center, open-label, randomized, prospective trial.


METHODS
Patients undergoing cadaveric or living donor kidney transplant at the University Hospital in Basel, Switzerland, between January 2001 and July 2004.


METHODS
Immunosuppression regimen consisting of cyclosporine, mycophenolate mofetil, and prednisone versus sirolimus, mycophenolate mofetil, and prednisone.


RESULTS
The primary outcome was kidney function, assessed using serum creatinine level. Secondary outcomes included patient and graft survival, number of rejections, and evidence of kidney damage, assessed using glomerular and tubular urine biomarker levels.


METHODS
Urine and serum were collected at 0, 7, 30, and 90 days. Kidney function was estimated using serum creatinine level. Urinary markers included alpha(1)-microglobulin and retinol-binding protein (tubular), transferrin and albumin (glomerular), and semiquantitative assessment of glucosuria. Protocol kidney biopsies were performed at days 90 and 180.


RESULTS
There were 63 patients randomly assigned to cyclosporine-based regimens, and 64, to sirolimus-based regimens. Kidney function was similar in both groups, whereas levels of markers associated with glomerular damage (albumin, 19.5 vs 8.96 mg/mmol creatinine; P < 0.001; transferrin, 13.1 vs 5.7 mg/mmol creatinine; P < 0.001) and those associated with tubular damage (alpha(1)-microglobulin, 11 vs 7.6 mg/mmol creatinine; P = 0.004; retinol-binding protein, 19.6 vs 9.6 mg/mmol creatinine; P = 0.002) were higher beginning at day 7 in patients randomly assigned to sirolimus therapy, with similar findings through day 90. Glucosuria incidence was higher in patients randomly assigned to sirolimus therapy beginning by day 30 (65% vs 30% on day 30; P = 0.002; 51% vs 22% on day 90; P < 0.001). On histologic examination, the overall severity of tubular lesions was significantly higher in patients randomly assigned to sirolimus therapy.


CONCLUSIONS
Small sample size, short-term follow-up likely insufficient to appreciate calcineurin-associated nephropathy.


CONCLUSIONS
Compared with a cyclosporine-based immunosuppression regimen, a sirolimus-based regimen is associated with de novo low-grade glomerular proteinuria, increased excretion of markers associated with tubular damage, and evidence of tubular damage on kidney biopsy.
Franz
Stefan
S
Clinic for Transplantation Immunology and Nephrology, University Hospital, Basel, Switzerland.
Regeniter
Axel
A
Hopfer
Helmut
H
Mihatsch
Michael
M
Dickenmann
Michael
M
D000293:Adolescent; D000328:Adult; D000368:Aged; D016572:Cyclosporine / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D007166:Immunosuppressive Agents / Q000627:therapeutic use* / Q000633:toxicity*; D016030:Kidney Transplantation; D007684:Kidney Tubules; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011507:Proteinuria / Q000139:chemically induced*; D020123:Sirolimus / Q000633:toxicity*; D055815:Young Adult
D007166:Immunosuppressive Agents; D016572:Cyclosporine; D020123:Sirolimus