According to results of a phase III trial published in the New England Journal of Medicine, mycophenolate mofetil was superior to azathioprine in maintaining a renal response to treatment and in preventing relapse in patients with lupus nephritis who had a response to induction therapy.

Researchers performed a randomised, double-blind, double-dummy, trial in which a total of 227 patients were randomised to receive maintenance treatment with either oral mycophenolate mofetil 2 g per day (n=116) or oral azathioprine 2 mg/kg body weight per day (n=111) plus placebo in each group, in patients who met response criteria during a 6-month induction trial. Additionally, up to 10mg prednisone per day or its equivalent was permitted. The primary efficacy end point was the time to treatment failure, which was defined as death, end-stage renal disease, doubling of the serum creatinine level, renal flare, or rescue therapy for lupus nephritis. Secondary assessments included the time to the individual components of treatment failure and adverse events. The following results were reported:

• Mycophenolate mofetil was superior to azathioprine with respect to the primary end point, time to treatment failure (hazard ratio, 0.44; 95% confidence interval, 0.25 to 0.77; P=0.003), and with respect to time to renal flare and time to rescue therapy (hazard ratio, <1.00; P<0.05).

• Observed rates of treatment failure were 16.4% in the mycophenolate mofetil group and 32.4% in the azathioprine group.

• Mycophenolate mofetil was also superior to azathioprine with respect to individual components of treatment failure, including the time to renal flare (hazard ratio for flare, 0.50; 0.26 to 0.93; P = 0.03). The time to rescue therapy for lupus nephritis was also longer with mycophenolate mofetil than with azathioprine (hazard ratio, 0.39; 0.18 to 0.87; P = 0.02); the rates of rescue were 7.8% (9 of 116 patients) and 17.1% (19 of 111), respectively.

• Serious adverse events occurred in 33.3% of patients in the azathioprine group and in 23.5% of those in the mycophenolate mofetil group (P=0.11), and the rate of withdrawal due to adverse events was higher with azathioprine than with mycophenolate mofetil (39.6% vs. 25.2%, P=0.02).

The researchers conclude that mycophenolate mofetil is superior to azathioprine in maintaining the renal response to treatment and in preventing relapse in patients with active lupus nephritis who have had a clinical response to induction therapy with either mycophenolate mofetil or intravenous cyclophosphamide.