The Food and Drug Administration (FDA, the Agency, or we) is announcing the availability of a draft document entitled "Innovative Designs for Clinical Trials of Cellular and Gene Therapy Products in Small Populations." The draft guidance document provides recommendations to sponsors who are planning clinical trials of cell and gene therapy (CGT) products intended for use in a disease or condition that affects a small population, generally one that meets the definition of a rare disease or condition under section 526(a)(2) of the FD&C Act (21 U.S.C. 360bb(a)(2)). It describes FDA requirements and provides considerations for the use of various clinical trial designs and endpoints to generate clinical evidence to support product licensure. The recommendations are intended for sponsors developing CGTs intended for use in small populations to leverage the use of innovative trial designs to simultaneously expedite drug development and generate data necessary to demonstrate substantial evidence of effectiveness.