Rituxan (rituximab) has failed to meet the primary endpoint in a Phase II/III trial involving patients with systemic lupus erythematosus (SLE), Genentech and Biogen Idec have announced.

The 52-week randomised, double-blind, placebo-controlled, multi centre study compared Rituxan with placebo in 257 patients with moderate to severe SLE who were taking an immunosuppressant.

Patients received Rituxan plus prednisone or placebo plus prednisone in two infusions 15 days apart. Patients were retreated after six months with the same regimen and evaluated for efficacy every four weeks.

Results of the study failed to demonstrate that a higher proportion of patients treated with Rituxan achieved a major or partial clinical response compared with the placebo group.

The primary endpoint of the study was the proportion of patients who achieved either a Major Clinical Response (MCR) or Partial Clinical Response (PCR) using the BILAG instrument at 52 weeks.

"We are disappointed in the results of this Phase II/III study, but we understood from the outset the significant challenges in developing treatments for systemic lupus erythematosus," Hal Barron, Genentech senior vice president, development and chief medical officer, said.

"We believe the ongoing Phase III trial in lupus nephritis (Lunar) remains an important study as it evaluates the potential of Rituxan in a different patient population," he added.

The drug maker also noted that the study failed to meet any of six secondary endpoints.

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