What's in a word? Defining "gene therapy medicines".

Gene therapy medicinal products (GTMPs) have emerged as a transformative class of medicines. Defining what a certain class of medicines encompasses, and what it does not, is key, with ample implications and consequential regulatory requirements. In April 2023, the European Commission proposed new pharmaceutical legislation safeguarding the public health within the European Union with a new, broader definition of GTMP, including genome editing medicines and nucleic acids of either source, regulating, replacing, or adding a genetic sequence that mediates its effect by transcription or translation. This definition is all-encompassing for any "genetic" intervention and is agnostic to mechanism of action, duration of action, location of action, and associated risk. Here, we take this as a paradigm to discuss how terminology and definitions are more than just words and can have meaningful regulatory, scientific, and public health implications.