Gene Editing: US Panel Review Of Vertex’s Exa-Cel To Focus On Nonclinical Assessment Of Off-Target Effects
Advisory committee discussion on the adequacy of Vertex’s analyses, using in silico and cellular methods, of off-target alterations with the gene therapy for sickle cell disease could help guide nonclinical assessment of future products made with CRISPR/Cas9-mediated gene editing.
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Agency grants same-day approval to the first two gene therapies for sickle cell disease; bluebird’s lentiviral-based lovo-cel carries a boxed label warning on hematologic malignancies, while Vertex’s CRISPR-Cas9 exa-cel carries a warning and precaution about potential off-target effects. Only the Vertex product qualified for a rare pediatric disease priority review voucher.
US FDA draft guidance does not specify the number of donor samples to test in nonclinical studies or the process for detecting genetic variants potentially susceptible to off-target effects. An advisory committee found adequate Vertex's analyses, which the sponsor called ‘the most comprehensive evaluation of off-target potential performed to date.’
US FDA advisory committee members questioned how potential off-target effects with Vertex’s gene therapy for sickle cell disease should be conveyed to patients and families, and whether labeling should say anything about these theoretical risks.