Despite the fact that they have gone through a rigorous approval process, uncertainty about newly approved drugs always exists. The uncertainty is amplified when drugs are approved on preliminary or interim evidence (i.e., accelerated approval) or on surrogate outcomes and when new serious harms emerge. The case of Tysabri-a multiple sclerosis drug that received accelerated approval because of promising preliminary evidence, was quickly withdrawn from the market several months later after the

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... ergence of an unexpected, typically fatal harm (progressive multifocal leukoencephalopathy), and was subsequently remarketed with a risk management plan-illustrates many of these uncertainties. We quantified the extent of the media coverage of Tysabri and compared Food and Drug Administration (FDA) press releases with the major media coverage in order to draw lessons on how to improve the communication of uncertainty about new drugs. TAKE-HOME MESSAGES  FDA could help the media by improving its press releases. Better press releases that routinely quantify benefits and harms with absolute numbers (e.g., with means or absolute risks) and that highlight uncertainties about a new drug would help journalists do a better job  FDA and the media should be clear that accelerated approval does not only mean "extra promise" but also "extra uncertainty." To create realistic expectations, FDA and drug company press releases and the media should explain the reasons for accelerated approval and highlight the inherent extra uncertainty.  FDA should flag new drugs for their first few years on the market. FDA should routinely use graphics or text to help ensure that the public understands that a new drug's limited track record means uncertainty about long-term benefits and harm. Despite the fact that they have gone through a rigorous approval process, there is always uncertainty about newly approved drugs: Will the benefits observed in typically short and small approval studies hold up over time? Will important side effects emerge? The uncertainty is amplified when drugs are approved based on preliminary evidence (accelerated approval) or on surrogate outcomes. Communicating uncertainty about new drugs is an important challenge facing FDA in fulfilling its mission to promote the safe and effective use of prescription drugs. To explore systematic and structured approaches to the characterization and communication of uncertainty,