Managing an FDA BLA Lifecycle from Complete Response Letter to Indication Narrowing: An Allogeneic Cell Therapy Case Study in Duchenne Muscular Dystrophy

When a marketing application's proposed indication is narrowed partway through review to align more closely with a trial's actual primary endpoint, the change is rarely cosmetic: it typically reflects a sponsor's recognition that the evidentiary case for the originally proposed, broader claim was weaker than the case for a more specific one the trial was actually designed and powered to support. This article traces the complete regulatory lifecycle of an allogeneic cardiosphere-derived cell therapy for Duchenne muscular dystrophy (DMD), from its initial pharmacodynamic rationale through a Complete Response Letter, an adverse advisory committee vote, and a subsequent amendment narrowing the proposed indication from cardiomyopathy to upper-limb function, as a case study in how indication scope and evidentiary strength are inseparable regulatory variables. The article develops the mechanism, the evidence base, and the regulatory timeline in full, proposes a real-world evidence strategy designed around the lessons of this lifecycle, and closes with recommendations for regulatory affairs professionals managing indication strategy for mutation-agnostic cell and gene therapies.Keywords: allogeneic cell therapy; Duchenne muscular dystrophy; indication narrowing; Complete Response Letter; Biologics License Application; regulatory artificial intelligence