FDA publishes  a new guidance document on Adaptive Clinical Trials, valid from November 2019.

This document provides guidance to sponsors and applicants submitting investigational new drug applications (INDs), new drug applications (NDAs), biologics licensing applications (BLAs), or supplemental applications on the appropriate use of adaptive designs for clinical trials to provide evidence of the effectiveness and safety of a drug or biologic.

The Adaptive Design Clinical Trials for Drugs and Biologics Guidance for Industry can be found at:

https://www.fda.gov/regulatory-information/search-fda-guidance-documents/adaptive-design-clinical-trials-drugs-and-biologics-guidance-industry