WASHINGTON (AP) — The nation's best-selling cancer drug has won federal approval as a treatment for rheumatoid arthritis patients for whom other, older drugs don't work, Genentech Inc. and Biogen Idec Inc. said Wednesday.

The Food and Drug Administration action comes more than eight years after the agency initially approved Rituxan to treat non-Hodgkin's lymphoma.

The two companies said Rituxan should be used by patients who haven't had success with a class of rheumatoid arthritis drugs called tumor necrosis factor, or TNF, blockers. Those drugs include Enbrel, Remicade and Humira.