In deciding whether or not to approve a new drug, FDA is primarily concerned with the drug’s effectiveness and safety. A successful drug will benefit patients without causing disproportionate harm.
In order to be considered effective by the FDA and physicians, a new drug must demonstrate the ability to improve at least one of the following: the way a patient feels, functions, or survives. If a new drug can demonstrate that it produces at least one of these three outcomes, it can be said to provide clinical benefit. FDA reviewers weigh a drug’s clinical benefits against its risks in order to determine whether or not it should be approved. The type of clinical benefit that drug developers expect an experimental drug to provide plays a major role in guiding clinical trial design and the selection of endpoints. An endpoint measures clinical benefit.
Toxicity refers to a drug’s potential to cause harm to a patient. While extremely toxic drugs are rarely approved for use, analyzing a drug’s safety is more complicated than determining whether or not it has any harmful side effects. Regulators must decide whether a drug’s benefits outweigh its potential harms. If a mild painkiller has the potential to cause liver damage, for example, that would likely be deemed an unreasonable risk. On the other hand, a third-line cancer drug with the same potential side effect might be considered reasonably safe, due to the severity of the condition being treated.