Thymoglobulin Induction Study Group

Incomplete

Brennan DC, et al. "Rabbit antithymocyte globulin versus basiliximab in renal transplantation". New England Journal of Medicine. 2006. 355(19):1967-1977.
PubMed • Full text

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Clinical Question

How does induction with antithymocyte globulin compare to basiliximab for high-immunologic risk kidney transplant recipients?

Bottom Line

Antithymocyte globulin was associated with lower rejection rates and rejection severity at 12 months when compared to basiliximab induction in high-risk kidney transplant recipients. The incidence of delayed graft function, patient survival and graft survival were similar between groups.

Major Points

Antibody induction therapy is used in a majority of kidney transplant recipients to reduce risk of acute rejection and delayed graft function, both of which negatively influence graft survival. Antithymocyte globulin is a rabbit-derived polyclonal antibody which exerts its affect across multiple immunologic targets and depletes T-lymphocytes. Basiliximab is a chimeric, monoclonal antibody which specifically inhibits the interleukin-2 receptor, blocking downward replication of T-lymphocytes, but it does not deplete them. Given that previous studies with antithymocyte globulin have showed reduced rates of delayed graft function with 7-14 day courses of therapy, and other studies have shown similar rejection rates with shorter vs longer courses of therapy, this study aimed to evaluate if a shorter course of antithymocyte globulin would be a superior to induction with basiliximab in high- risk kidney transplant recipients.

This international, multicenter, randomized controlled trial evaluated a 5-day course of thymoglobulin vs basiliximab induction in patients deemed highest risk for acute rejection and delayed graft function. There was no difference in the primary composite endpoint of acute rejection, delayed graft function, graft loss or death. However, overall rejection rates and severe rejection rates were significantly lower in the antithymocyte globulin-treated patients when compared to basiliximab-treated patients. Individual components of the composite (delayed graft function, graft loss and death) were not different between groups. There were lower rates of rejection in black and nonblack subgroups with antithymocyte globulin, but only the comparison within nonblack patients was statistically significant. Leukopenia and infections were more common in the antithymocyte globulin-treated patients. However, rates of cancer, serious adverse events were similar between groups. Notably, the rate of CMV infection was lower in the anti-thymocyte group.

This study demonstrates improved rejection rates, but similar rates of delayed graft function, with antithymocyte globulin vs. basiliximab in high-risk patients. At least one other study demonstrated superiority of antithymocyte globulin with regards to rejection and delayed graft function, when compared to an interleukin-2 receptor antagonist in a high-risk population. Other studies, including a meta analysis that have compared antithymocyte globulin to basiliximab and have found no difference have been in low-risk or general populations. Longer term randomized controlled trials may be needed to determine if either induction agent influences longer term graft survival, however a UNOS registry data review by Cai and Terasaki of over 100,000 kidney transplant recipients showed that antithymocyte globulin had improved 5-year graft survival vs. basiliximab.

Guidelines

KDIGO Care of Kidney Transplant Recipients (2009)

• Recommendations for Induction Therapy:
  • We recommend including induction therapy with a biologic agent as part of the initial immunosuppressive regimen in KTRs. (1A)
  • We recommend that an IL2RA be the first-line induction therapy. (1B)
  • We suggest using a lymphocyte-depleting agent, rather than an IL2RA, for KTRs at high immunologic risk. (2B)

Design

• Prospective, open-label, multicenter, international, randomized controlled trial
• N=278
  • Antithymocyte globulin (n=141)
  • Basiliximab (n=137)
• Setting: 28 centers in US and Europe
• Enrollment: 2000-2002
• Mean follow-up: 1 year
• Analysis: intention-to-treat
• Primary outcome: composite of the first occurrence of biopsy-proven acute rejection, delayed graft function, graft loss or death at 12 months.

Population

Inclusion Criteria

• Recipient of deceased donor kidney
• High-risk for rejection
  • Eligibility determined by duration of cold ischemia time (CIT) and risk factors below:
    • CIT <16 hrs, or ≤30hrs and any machine perfusion – DCD donor; or standard deceased donor with age >50 yrs or serum creatinine >2.5mg/dL
    • CIT 16-24 hrs – one donor or recipient risk factor required
    • CIT>24hrs or >30 hrs and some machine perfusion – no additional risk factors required
  • Recipient risk factors: repeated transplantation; black race; one or more HLA mismatch with donor
  • Donor risk factors: cold ischemia time >24 hours; age > 50 years; donation after cardiac death (DCD) donor; acute tubular necrosis; high inotropic support required

Exclusion Criteria

• Immunosuppression prior to transplantation
• Investigational drug use within past 30 days
• Known contraindication to thymoglobulin or basiliximab
• Suspected or known infection or seropositive for hepatitis B surface antigen or core antibody, hepatitis C or HIV
• Had cancer within 2 years
• Pregnant women, nursing mothers and women of child-bearing potential who were not using condoms or oral contraceptives

Baseline Characteristics

For the antithymocyte globulin group:

• Demographics: 56% Male; Mean age 51.3 years; 60.3% white, 29.1% black
• Previous kidney transplant: 11.3%
• Peak panel-reactive antibody: 14%
• Donor mean age: 46.8 years (53.2% had donor age >50 years)
• DCD donor: 5%
• Cold ischemia time: 25.4 hours (51.8% had CIT >24 hours)
• CMV high risk (donor seropositive/recipient seronegative): 14.9%

Interventions

• Induction:
  • Thymoglobulin: 1.5mg/kg x5 daily doses (total dose = 7.5mg/kg), first dose intra-operatively
  • Basiliximab 20mg x2 doses, first dose intra-operatively, second dose on post-op day 4
• All patients received cyclosporine (target level per local institution), mycophenolate 2g/day, and steroids to be tapered to 5mg by 6 months
  • Cyclosporine was started when urine output ≥1.5L/day for 2 consecutive days; serum creatinine was ≤3.0 mg/dL for 2 consecutive days; or serum creatinine decreased to <50% pre-transplant level.
    • If cyclosporine was started later than post-operative day 4, it had to be within “therapeutic range” by post-operative day 10.

Outcomes

Comparisons are antithymocyte globulin vs. basiliximab.

Primary Outcome

Composite of acute rejection, delayed graft function, graft loss and death

50.4% vs. 56.2% (P=0.34)

Secondary Outcomes

Biopsy-proven acute rejection

15.6% vs. 25.5% (P=0.02)

Antibody-treated acute rejection

1.4% vs. 8% (P=0.005)

Delayed graft function

40.4% vs. 44.5% (P=0.54)

Graft loss

9.2% vs. 10.2% (P=0.68)

Death

4.3% vs. 4.4% (P=0.90)

Subgroup Analyses

Black patients - Biopsy-proven acute rejection

19.5% vs. 33.3% (P=0.014)

Non-black patients - Biopsy-proven acute rejection

14% vs. 22.4% (P=0.07)

U.S. patients - Biopsy-proven acute rejection

14.3% vs. 22.8% (P=0.07)

European patients - Biopsy-proven acute rejection

18% vs. 31.1% (P=0.12)

Adverse Events

Serious events (not defined)

73% vs. 72.3% (P=0.89)

Leukopenia

33.3% vs. 14.6% (P<0.001)

Thrombocytopenia

10.6% vs. 5.8% (P=0.19)

All infections

85.8% vs. 75.2% (P=0.03)

Cytomegalovirus

7.8% vs. 17.5% (P=0.02)

Cancer

3.5% vs. 0.7% (P=0.21)

Post-transplant lymphoproliferative disorder (PTLD)

2.1% vs. 0% (P=0.13)

Criticisms

• Open-label, non-blinded design of the study
• Relatively short-term (1 year) follow up

Funding

This study was supported by SangStat Medical Corporation and Genzyme.