Vertex discontinued development of an mRNA-based cystic fibrosis therapy after encountering tolerability issues tied to how the genetic medicine was delivered. The company said challenges in administration mirrored similar delivery-related problems seen across parts of the mRNA field. The decision removes a program from Vertex’s CF pipeline and underscores how delivery tolerability can still be a gating factor for in vivo genetic medicines, even when mechanistic targeting is supported. Details on specific trial stage outcomes were not included in the provided release text, but Vertex’s move indicates a strategic retreat from that modality for cystic fibrosis.