Approvable letters, and the related non-approvable letters (alternately not-approvable letters), were notifications sent out by the Food and Drug Administration (FDA) to drug manufacturers alerting them to the approval prospects of their drugs under development.
[1] The letters were intended to let manufacturers know how much work is needed on their applications.
[2] Approvable and non-approvable letters were covered under Title 21 of the Code of Federal Regulations, section 314.110.
[3] In 2018, the FDA replaced approvable letters with Complete Response Letters (CRL) to notify applicants when additional information is required before approval.
It was an indication that the application substantially met FDA requirements if specific conditions, such as labeling changes, are agreed to.