The purpose of this guidance is to provide recommendations to sponsors interested in studying multiple versions of a cellular or gene therapy product in an early-phase clinical trial for a single disease.  Sponsors have expressed interest in gathering preliminary evidence of safety and activity using multiple versions of a cellular or gene therapy product in a single clinical trial.  Although multiple versions of a product can be studied together in a single clinical trial, each version of the product is distinct and is generally submitted to FDA in a separate investigational new drug application (IND).  The objective of these early-phase clinical studies is to guide which version(s) of the product to pursue for further development in later-phase studies.  Thus, these studies are not intended to provide primary evidence of effectiveness to support a marketing application and generally are not adequately powered to demonstrate a statistically significant difference in efficacy between the study arms.  In this guidance, we, FDA, provide recommendations for studies that evaluate multiple versions of a cellular or gene therapy product, including how to organize and structure the INDs, submit new information, and report adverse events.  This guidance finalizes the draft guidance of the same title dated September 2021.