This document discusses issues in trial design and analysis for precision medicine products regulated by CBER. For autologous products, manufacturing failures or delays can impact study power and interpretation by affecting eligibility or disease progression during the trial. Example trials are discussed. For companion diagnostic products, basic study designs like randomize-all or marker-stratified are recommended, with statistical testing across groups using alpha adjustment strategies to control false conclusions of efficacy. Methods for testing efficacy in marker-positive subgroups and overall populations are also discussed.