title: Tubular toxicity in sirolimus- and cyclosporine-based transplant immunosuppression strategies: an ancillary study from a randomized controlled trial.
abstract: 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.
authors.affiliation: Clinic for Transplantation Immunology and Nephrology, University Hospital, Basel, Switzerland.
authors.forename: Stefan
authors.initials: S
authors.lastname: Franz
authors.forename: Axel
authors.initials: A
authors.lastname: Regeniter
authors.forename: Helmut
authors.initials: H
authors.lastname: Hopfer
authors.forename: Michael
authors.initials: M
authors.lastname: Mihatsch
authors.forename: Michael
authors.initials: M
authors.lastname: Dickenmann
mesh_terms: 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
chemical_list: D007166:Immunosuppressive Agents; D016572:Cyclosporine; D020123:Sirolimus