The January 2005 CMC Strategy Forum was devoted to a discussion of live virus vaccines and viral vectors used for gene therapy. The purpose of the meeting was to determine whether consensus positions could be reached among the delegates regarding lot release, stability, characterization, and comparability testing. Part 1 of this two-part report on that meeting describes factors influencing the choices of lot-release assays for vaccines and gene-therapy products (1). Part 2 presents potency testing, characterization, and comparability studies, including…