Mycophenolate mofetil reduces the risk of acute rejection less in African-American than in Caucasian kidney recipients.

BACKGROUND

Multicenter clinical trials have shown that mycophenolate mofetil (MMF) reduces the risk of acute rejection, but it is unknown whether African-Americans constitute a subgroup of recipients less likely to benefit from MMF.

METHODS

This study compared the acute rejection rates within 6 months of kidney transplantation in MMF-treated transplant patients with those on azathioprine (AZA) at a single center. The study population consisted of 353 consecutive recipients of cadaver or living donor kidney transplants. African-Americans constituted 43% of the patients on AZA and 49% of the patients on MMF. Variables used in a Cox regression analysis included MMF immunosuppression, recipient race, type of transplant, delayed graft function, postoperative immune induction, average cyclosporine trough level, and HLA mismatch.

RESULTS

Significantly fewer patients on MMF experienced a biopsy-proven rejection episode than those treated with AZA (24% vs. 42%, respectively; relative risk [RR]=0.57, P=0.001). This decrease in risk was greater in Caucasian transplant recipients (MMF vs. AZA: 16% vs. 46%, RR=0.35, P < 0.001) than in African-American patients (32% vs. 36%, RR=0.88, P=0.6). Within each race stratum, the mean cyclosporine trough levels averaged over 2-week intervals were nearly identical for AZA- compared with MMF-treated patients. In the regression model, the effect of MMF on the incidence of rejection was again less in African-American than in Caucasian patients.

CONCLUSIONS

Kidney recipients treated with MMF have a significantly lower risk of acute rejection within 6 months of transplantation than those given AZA. This reduction in risk is significantly less in African-American recipients than Caucasians.