New & Approved: Activa Parkinson's Control System Enbrel

OB/GYN News,  Feb 15, 2002  by Elizabeth Mechcatie

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Activa Parkinson's Control System

(Medtronic)

A deep-brain stimulator for use in both sides of the brain to help reduce symptoms of advanced Parkinson's disease in patients who still respond to levodopa but whose symptoms cannot be adequately controlled with medication. Approved in 1997 for unilateral implantation.

* Recommended Usage: A programmable, battery-operated pulse generator, placed subcutaneously under the clavicle, is connected to electrodes implanted in the subthalamic nucleus or globus pallidus. Mild electrical pulses are transmitted to these structures, which are overactive and believed to cause Parkinsonian motor dysfunction. Can be turned on and off by holding a magnet over the generator.

* Special Considerations: In the international trial that led to approval, most of the 134 patients had at least one adverse event, including 7 cases of intracranial hemorrhage (6 had subsequent neurologic deficits), 4 infections, and 5 cases of dyskinesia related to stimulation. Results "varied considerably and specific benefit for an individual cannot be predicted," the FDA said in a statement.

* Comment: The trial included 134 patients aged 30-75 years in advanced stages of Parkinson's who could not be satisfactorily controlled with levodopa because of motor complications. Their motor scores improved by a median of 49% with subthalamic nucleus stimulation and by 37% with pallidal stimulation, compared with no stimulation. During the 6-month study, the proportion of each day spent with good mobility and no involuntary movements ("on-time") rose from 27% to 74% with subthalamic stimulation and from 28% to 64% with pallidal stimulation. The improvements were highly significant (N. Engl. J. Med. 345[13]:956-63, 2001).

This therapy allowed the benefits of levodopa to be fully expressed, "with a dramatic reduction in the complications that limit its utility," particularly involuntary movements (dyskinesia and motor fluctuations), said Dr. C. Warren Olanow, one of the investigators and professor and chair of the department of neurology at Mount Sinai School of Medicine, New York. The results are "all the more dramatic," considering that they could not be attained with medical therapy, added Dr. Olanow, who has served as a consultant to Medtronic in the past. Medtronic will be conducting a 3-year study to assess long-term clinical results.

Enbrel

(etanercept, Immunex, Wyeth-Ayerst)

A tumor necrosis factor (TNF) inhibitor for reducing the signs and symptoms of active arthritis in people with psoriatic arthritis, the first treatment approved for this condition. Used alone or with methotrexate in patients who do not respond adequately to methotrexate alone. Approved for rheumatoid arthritis (RA) in 1998.

* Recommended Dosage: 25 mg subcutaneously twice a week.

* Special Considerations: In the psoriatic arthritis trials, serious infections were not more common in Enbrel-treated patients, but because of its mechanism of action, the risk of infection has been a concern. Since approval, serious infections, including some fatalities, have been reported in RA patients on Enbrel, including five tuberculosis cases reported to the FDA in 2000.

* Comment: Enbrel reduces inflammation by inactivating TNF, a cytokine that plays an important role in the inflammatory cascade that results in RA symptoms and joint damage. It is "central to the entire cytokine cascade in both psoriatic arthritis and psoriasis," which are other immune-mediated diseases, said Dr. Kenneth Gordon, director of the psoriasis treatment center at Northwestern University, Chicago.

Dr. Gordon was a principal investigator in a multicenter study of 205 patients, aged 18-70 years, with active psoriatic arthritis. Overall, 50% of those on Enbrel had at least a 20% improvement in the American College of Rheumatology response criteria (ACR 20) at 6 months vs. 13% with placebo. Those on Enbrel also were more likely to have ACR responses of at least 50% and 70%.

Enbrel has a better side-effect profile than other treatments for psonatic arthritis, such as methotrexate and even NSAIDs, said Dr. Gordon, who has served as an advisor to Immunex. The cost for 1 year of therapy is estimated at $10,000-$12,000, according to Immunex. Studies of Enbrel in psoriasis patients are underway

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