Clinical development on the frontier: gene therapy for duchenne muscular dystrophy.

: The development of adeno-associated virus (AAV) vectors as safe vehicles for delivery of therapeutic genes has been a major milestone in the advancement of gene therapy, enabling a promising strategy for ameliorating a wide range of diseases, including Duchenne muscular dystrophy (DMD).: Based on experience with the development of a gene transfer therapy agent for DMD, we discuss ways in which gene therapy for rare disease challenges traditional clinical development paradigms, and recommend a step-wise approach for design and evaluation to support broader applicability of gene therapy.: The gene therapy development approach should intentionally design the therapeutic construct and the clinical study to systematically evaluate agent delivery, safety, and efficacy. Rigorous preclinical work is essential for establishing an effective gene delivery platform and determining the efficacious dose. Clinical studies should thoroughly evaluate transduction, on-target transgene expression at the tissue and cellular level, and functional efficacy.