Genentech ( DNA) and Biogen Idec ( BIIB) said Wednesday that a phase III study of Rituxan failed to meet the primary endpoint as a treatment for patients with a form of lupus.

A previous phase III study of Rituxan in lupus patients failed last year. Rituxan, with 2008 U.S. sales of $2.6 billion, is used primarily to treat blood-related cancers like non-Hodgkin's lymphoma.

In this most recent study, Genentech said treatment with Rituxan did nothing to improve kidney function in patients with lupus nephritis, which is characterized by inflammation of the kidney caused by systemic lupus erythematosus (SLE or lupus), an autoimmune disease.

There are no approved drugs to treat SLE, or lupus, although steroids are commonly used to treat symptoms. Recently, a drug from La Jolla Pharmaceuticals ( LJPC) and BioMarin Pharmaceuticals ( BMRN) was a failure in a phase III study of lupus patients.

Lupus is a chronic disease in which the body's immune system attacks connective tissue, resulting in inflammation and tissue damage, often to the heart, joints, lungs and kidneys. Women are more often diagnosed with lupus than men, and the disease goes through periods where it flares up then goes into remission.

At the time of publication, Feuerstein's Biotech Select model portfolio was long Genentech.

Adam Feuerstein writes regularly for TheStreet.com. In keeping with TSC's editorial policy, he doesn't own or short individual stocks, although he owns stock in TheStreet.com. He also doesn't invest in hedge funds or other private investment partnerships. Feuerstein appreciates your feedback; click here to send him an email.

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