Etanercept for MG
Shows Promise, Risks

Doctors at the University of Illinois and Rush University Medical Center in Chicago and the University of Texas at Galveston have found that the drug etanercept (Enbrel) may offer hope to some people with myasthenia gravis (MG) who take relatively high doses of corticosteroids, such as prednisone.

In the autoimmune disease MG, the immune system mistakenly attacks the part of the muscle cell that receives signals from a nerve cell, leading to fluctuating weakness.

Etanercept, which has FDA approval for the treatment of arthritis and the skin disorder psoriasis, blocks the action of tumor necrosis factor (TNF), a substance secreted by cells of the immune system that has been implicated as a contributor to MG and other autoimmune disorders.

The doctors originally enrolled 11 people with MG, all of whom had needed at least 25 milligrams of prednisone every other day for more than six months to control symptoms. This is a potentially toxic corticosteroid level.

Eight of the 11 participants completed the study. One withdrew because of a skin rash, which disappeared when the etanercept was stopped. Two other participants withdrew when their disease worsened.

Six of the 11 patients improved with etanercept, administered by injection twice a week, based on objective measures of muscle strength and the ability to successfully taper their prednisone doses.

The study team, which included MDA grantees Erdem Tuzun and Premkumar Christadoss at the University of Texas at Galveston, published its findings in the Dec. 28 issue of Neurology. (Amgen, which markets Enbrel, contributed to funding for the trial.)

The authors conclude that further investigation of etanercept in MG should be considered. However, they caution that at least one of the patients whose MG worsened may have responded to the etanercept by increasing TNF production, a highly undesirable effect.