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Table 4 Key events surrounding withdrawal and reintroduction of Tysabri

From: Halo and spillover effect illustrations for selected beneficial medical devices and drugs

Product Year Event
Tysabri 2004 FDA approves Tysabri (natalizumab) for relapsing-remitting Multiple Sclerosis (RRMS)
2004 Biogen reports 3 cases, 1 fatality, of progressive multifocal leukoencephalopathy (PML)
2005 Tysabri withdrawn from the market
2006 Clinical trial participants tested for PML; safety data gathered and reviewed by drug sponsor and FDA
2006 FDA studies evidence, recommends Tysabri reintroduced via restricted distribution program “TOUCH”
Post-2006 Analyses of TOUCH data, clinical trial data, and continued research help clarify risk of PML; Health care providers have risk model to quantify and rank vulnerability to PML for patients
Post-2006 Physicians and patients know more about the risk of PML to Tysabri; The number of patients on Tysabri remains well short of expectations.