Contents of US Food and Drug Administration Refuse-to-File Letters for New Drug Applications and Efficacy Supplements and Their Public Disclosure by Applicants

Before reviewing drug applications, the US Food and Drug Administration (FDA) conducts "filing reviews" to assess whether they are complete enough for full review. If the applications are incomplete, the FDA issues refuse-to-file (RTF) letters identifying deficiencies. The FDA does not make these RTF letters public at the time of issuance. Why the FDA issues RTF letters and how often the letters and their contents are made publicly available are unknown.