Tysabri Recall
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Another drug that was approved by the FDA through its fast-track (or accelerated) approval process has been recalled after being on the market for just three months. The drug, Tysabri (natalizumab) is manufactured by Biogen Idec and Elan Corporation. Tysabri (registered trademark) is used in treatment for multiple sclerosis (MS). The companies are suspending supply of Tysabri from commercial distribution and physicians should suspend dosing of Tysabri until further notification. In addition, the companies have suspended dosing in all clinical trials.

This decision is based on very recent reports of two serious adverse events that have occurred in patients treated with Tysabri (formerly known as Antegren) in combination with AVONEX (Interferon beta-1a) in clinical trials. These events involve one fatal, confirmed case and one suspected case of progressive multifocal leukoencephalopathy (PML), a rare and frequently fatal, demyelinating disease of the central nervous system. Both patients received more than two years of Tysabri therapy in combination with AVONEX. The companies’ actions have been taken in consultation with U.S. Food and Drug Administration (FDA). Worldwide regulatory agencies are being kept informed. As early as two weeks ago, though, the companies said that the Phase III Tysabri AFFIRM monotherapy trial achieved the two-year primary endpoint of slowing the progression of disability in patients with relapsing forms of multiple sclerosis (MS). Tysabri treatment led to a 42 percent reduction in the risk of disability progression relative to placebo. These data also demonstrated a 67 percent reduction in the rate of clinical relapses over two years, which was sustained and consistent with the previously reported one-year results.

Another two drugs that received fast track approval are Celebrex and Vioxx. Despite revelations that Vioxx's manufacturer, Merck, may have known the adverse side effects of the drug years ago, the company did not recall it. It is also generally believed that Pfizer knew the risks of Celebrex.  In a rather bizarre turn of events, an FDA panel that had strong financial ties to Merck and Pfizer voted to bring Vioxx back on the market despite its high risk and leave Celebrex on the market with a warning. These developments have put pressure on the FDA to completely review its fast-track approval processes that are designed to help drug companies introduce products faster even if that means that patient safety is compromised.

The companies, Biogen and Elan, will work with clinical investigators to evaluate Tysabri-treated patients and will consult with leading experts to better understand the possible risk of PML. The outcome of these evaluations will be used to determine possible re-initiation of dosing in clinical trials and future commercial availability.

In total, approximately 3,000 patients have been treated with Tysabri in clinical trials of MS, Crohn’s disease, and rheumatoid arthritis. To date, the companies say that they have received no reports of PML in MS patients receiving Tysabri monotherapy or in patients with Crohn’s disease or rheumatoid arthritis in Tysabri clinical trials. Biogen Idec has received no reports of PML in patients treated with AVONEX alone, a product that has been on the market since 1996.

The FDA, in a public health advisory, says that patients being treated with Tysabri should contact their physician to discuss appropriate alternative treatments. At this time, there are no specific diagnostic or therapeutic interventions recommended for patients who have been taking Tysabri, other than to discontinue its use.

Tysabri received accelerated approval in November 2004 for reducing the frequency of exacerbations in patients with remitting-relapsing MS, the most common form of this disease, after one year of treatment. Tysabri when added to Avonex reduced the risk of exacerbations by 54% compared to Avonex alone. Tysabri by itself reduced the risk by 66% compared to placebo. These results represent an important and meaningful benefit for patients with MS. At the time of approval, approximately 1,100 patients with MS had received Tysabri for one year or more. Confirmatory studies were required to be carried out to show continued benefit of the drug after two years of treatment. The two cases reported here occurred in patients in the confirmatory studies. No cases of PML were observed during the clinical trials performed prior to approval of Tysabri. 

The approval of Tysabri is based on positive results seen in patients after one year of treatment, the FDA said in its announcement in November 2004. This product received accelerated approval because it appears to provide substantial benefit for patients with a serious disease. As part of that approval, the manufacturer has committed to continuing its trials of this product for another year.

According to the Multiple Sclerosis Association of America, approximately 350,000 individuals have been diagnosed with MS in the U.S., with an estimated 10,000 new cases diagnosed each year. The most common form of MS at the time of initial diagnosis is a relapsing-remitting form, in which acute symptoms or worsening of neurologic function (referred to as "relapses," "attacks," or "exacerbations") occur intermittently. The symptoms can diminish or disappear for months or years between relapses. 

Although the cause of MS is unknown, it is widely considered to be an autoimmune disease in which the person's immune system attacks the brain and/or spinal cord. Tysabri appears to work by binding to these immune system cells, thus preventing them from traveling to the brain where they can cause damage.

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Update: June 5, 2006 - The FDA has allowed Tysabri sales with strict measures to make sure that any side effects can be caught before they become fatal.

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