ABSTRACT
Gene therapy is a rapidly evolving field in which a wide variety of therapeutic approaches are being considered and tested. In regulating product development in such an area, it is important to be flexible and attentive to practical limitations. Gene therapy products also present novel issues. One example is the potential for recombination. Recombination can occur between sequences in a vector and other elements in a packaging cell or producer cell. Investigators with products under development should be aware of this problem and consider alternative selection markers, especially since simply omitting ampicillin from production runs may lead to poor yields. Animal studies are usually needed and informative in testing of new products prior to human use, even though they provide imperfect predictions about effects in humans. Gene therapy clinical trials involve special unresolved issues, as well as usual issues of design and ethics affecting all trials.
