Genentech and Biogen say that decision was based on incidence of PML as a side effect.

The FDA has told Genentech and Biogen Idec that it cannot support the approval of Rituxan in people with rheumatoid arthritis (RA) who have not previously received methotrexate (MTX) or those who did not adequately respond to MTX. The agency said that the rare risk of progessive multifocal leukeoencephalopathy (PML) was not acceptable in light of the number of effective RA treatments already available to patients in earlier stages of the disease.

The firms say that there have been three reports of PML out of approximately 100,000 patients treated. There are no known reliable PML therapies.

While the FDA administered a complete response letter for sBLA covering the earlier use of Rituxan in RA, it approved another sBLA submission, updating safety and efficacy data on the label related to how later-stage patients, or those who have inadequately responded to tumor necrosis factor (TNF)-antagonist therapies, can be retreated with Rituxan.

The prescribing information will now include language that subsequent courses of the standard Rituxan regimen (two doses at 1,000 mg each) can be administered every 24 weeks or based on clinical evaluation but no sooner than 16 weeks. Rituxan’s ability to improve physical function and slow joint damage for up to two years as demonstrated in clinical studies has also been added.

Rituxan was approved in 2006 for patients with moderately-to-severely active RA who have inadequately responded to one or more tumor necrosis factor (TNF)-antagonist therapies. The drug made about $2.59 billion in sales last year, a 13% increase from 2007. Biogen Idec obtains revenues on sales under the companies’ joint business arrangement and logged $1.1 billion in 2008.

The firms are also jointly developing Rituxan for chronic lymphocytic leukemia and follicular non-Hodgkin’s lymphoma maintenance.

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