BOSTON (Dow Jones) -- A late-stage clinical trial of oncology drug Rituxan failed to show it was effective in treating a certain type of multiple sclerosis, according to Genentech Inc. and Biogen Idec Inc.

Late Monday, Genentech (DNA) and Biogen (BIIB) said that in a Phase II/III trial, Rituxan didn't show the antibody-based medication could effectively slow the progression of primary-progressive multiple sclerosis, or PPMS.

The companies added that currently there are no effective treatments for PPMS, a particularly hard to treat form of the disease.

Rituxan is already approved for the treatment of non-Hodgkin's lymphoma and rheumatoid arthritis.

Biogen Iden markets Avonex, one of the world's best-selling medications for treating multiple sclerosis. The company also co-markets with Elan Corp. (ELN) Tysabri as a multiple sclerosis therapy.

Genentech, a publicly traded division of Swiss conglomerate Roche, is a leading developer of oncology medications.

Biogen Iden markets Avonex, one of the world's best-selling medications for treating multiple sclerosis. The company also co-markets with Elan Corp. (ELN) Tysabri as a multiple sclerosis therapy.

Labels: Rituxan, Tysabri