In the United States (US) and the European Union (EU), regulatory agencies—the US Food and Drug Administration (FDA) and the European Medicines Agency (EMA), respectively—are responsible for assessing the benefit-risk profile of new drugs before they enter the market. The mandate of these regulators to protect public health by ensuring that patients have access to safe and efficacious drugs requires them to carefully balance the need for robust and comprehensive evidence on efficacy and safety at the time of market approval while making promising new drugs available to patients in a timely manner. This “evidence vs. access conundrum” can also be framed in terms of the amount of uncertainty regulators are willing to accept.

Placing a greater weight on the availability of complete evidence for regulatory decision making, typically obtained from randomized controlled trials (RCTs) that measure patient-relevant endpoints such as survival, means more certainty that drugs available on the market have a positive benefit-risk profile. Conversely, granting approval on the basis of incomplete evidence shows greater willingness to accept uncertainty about a new drug's therapeutic value.