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Vertex’s Exa-Cel Off-Target Analyses Set Early Bar For Other Genome Editing Products

 
• By Sue Sutter

US FDA draft guidance does not specify the number of donor samples to test in nonclinical studies or the process for detecting genetic variants potentially susceptible to off-target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.’

Foggy road
FDA's guidance is foggy on the quantum of evidence needed for nonclinical off-target analyses. • Source: Shutterstock

A lack of specificity in the US Food and Drug Administration’s genome editing draft guidance allowed Vertex Pharmaceuticals Incorporated to set what an advisory committee deemed a sufficiently high bar in its analyses for potential off-target effects with the sickle cell disease gene therapy exagamglogene autotemcel (exa-cel).

Although the FDA’s guidance describes the types of nonclinical studies that are appropriate for analyzing potential off-target edits, it does not quantify the number of donor samples that should be tested in such studies or how a sponsor should

Key Takeaways

  • FDA guidance on genome editing products does not specify the number of donor samples that should be used in nonclinical analyses of off-target editing.

  • Vertex reported that no off-target editing was observed across three off-target assessments performed in CD34+ hematopoietic stem and progenitor cells from a total of 14 healthy donors and patients

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